WO2024093458A1 - 复合电极及其制备方法、电池和用电设备 - Google Patents

复合电极及其制备方法、电池和用电设备 Download PDF

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WO2024093458A1
WO2024093458A1 PCT/CN2023/114473 CN2023114473W WO2024093458A1 WO 2024093458 A1 WO2024093458 A1 WO 2024093458A1 CN 2023114473 W CN2023114473 W CN 2023114473W WO 2024093458 A1 WO2024093458 A1 WO 2024093458A1
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active layer
active
composite electrode
layer
ternary
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English (en)
French (fr)
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丁有才
高鹏飞
李彦朋
吴怡祯
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Priority to EP23884395.7A priority Critical patent/EP4507024A4/en
Publication of WO2024093458A1 publication Critical patent/WO2024093458A1/zh
Priority to US18/948,356 priority patent/US20250070160A1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/043—Processes of manufacture in general involving compressing or compaction
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1397—Processes of manufacture of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of lithium-ion batteries, and in particular to a composite electrode and a preparation method thereof, a battery and an electrical device.
  • ternary lithium compounds There are currently two main types of cathode materials for commercial lithium-ion batteries: ternary lithium compounds and lithium iron phosphate.
  • the advantage of ternary materials is that they have high energy density and are suitable for long-range vehicles, but the disadvantage is that elements such as cobalt and nickel are relatively expensive, and there are safety risks, which are more likely to cause thermal runaway and fire.
  • the safety of lithium iron phosphate will be much improved, and because it does not contain rare transition metal elements, the cost is also lower.
  • the energy density of lithium iron phosphate is low, which will result in a short driving range. In this context, it is particularly important to develop a material that has both high energy density and low cost, as well as high safety characteristics. Lithium iron manganese phosphate is such a new material.
  • the crystal structure of lithium manganese iron phosphate material is the same as that of lithium iron phosphate, both of which belong to the olivine crystal type. The difference is that on the basis of lithium iron phosphate, Mn atoms are used to partially replace Fe atoms. Compared with lithium iron phosphate, the energy density of lithium manganese iron phosphate material can be greatly improved, and the safety has not deteriorated, which is almost the same as lithium iron phosphate. However, the conductivity of lithium manganese iron phosphate material is not good.
  • the main purpose of this application is to provide a composite electrode, aiming to improve the comprehensive performance of the electrode.
  • the present application proposes a composite electrode, which includes a current collector, a first active layer and a second active layer, wherein the first active layer is arranged on the current collector, and the second active layer is arranged on the side of the first active layer away from the current collector, and the first active layer includes a lithium iron manganese phosphate material, wherein at least a portion of the surface of the lithium iron manganese phosphate material is provided with a conductive coating material, and the mass of the conductive coating material is 1.0%-10.0% of the mass of the lithium iron manganese phosphate material.
  • the mass of the conductive coating material is 1%-5% of the mass of the lithium iron manganese phosphate material.
  • the mass of the conductive coating material is 1.0%-5% of the mass of the lithium manganese iron phosphate material, for example, it can be 1.0%, 2.0%, 3.0%, 4.0%, 5.0%, and the range between any two of the above points.
  • the mass of the conductive coating material is 1.3%-2.5% of the mass of the lithium manganese iron phosphate material.
  • the mass of the conductive coating material is 1.3%-2.5% of the mass of the lithium manganese iron phosphate material, the battery performance is better. Therefore, the mass of the conductive coating material is 1.3%-2.5% of the mass of the lithium manganese iron phosphate material, for example, it can be 1.3%, 1.5%, 1.8%, 2.0%, 2.3%, 2.5%, and the range value between any two of the above point values.
  • the conductive coating material is a carbon material.
  • the conductive coating material is a carbon material.
  • the porous carbon used as the coating material contains defects and oxygen-containing functional groups, which can catalyze the decomposition of the electrolyte.
  • the carbon material is provided on at least part of the surface of the lithium iron manganese phosphate material.
  • the carbon material is used to improve the conductivity of the lithium iron manganese phosphate material.
  • the active layer containing the lithium iron manganese phosphate material is provided in the inner layer, and the other active layer is provided in the outer layer. In this way, it is avoided that the active layer containing the lithium iron manganese phosphate material is directly exposed to the outside in a large area, and the lithium iron manganese phosphate material provided with the carbon material is reduced.
  • the problem of catalyzing the decomposition of the electrolyte at a high potential under a high conductivity condition is reduced.
  • the coating amount of the carbon material on at least part of the surface of the lithium iron manganese phosphate material can be increased, and the conductivity of the lithium iron manganese phosphate material can be improved, so as to solve the problem that the small amount of conductive carbon added in the traditional formula is difficult to meet the conductivity requirements.
  • the mass of the conductive coating material is 1.0%-10.0% of the mass of the lithium manganese iron phosphate material, for example, it can be 1.0%, 2.0%, 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, 8.0%, 9.0%, 10.0%, and the range between any two of the above points.
  • the composite electrode further comprises a third active layer, and the third active layer is disposed between the current collector and the first active layer;
  • the composite electrode further includes a fourth active layer, and the fourth active layer is disposed between the first active layer and the second active layer.
  • the composite electrode on the basis of satisfying that the second active layer covers the first active layer, also includes a third active layer 4, and the third active layer is arranged between the current collector 1 and the first active layer 2.
  • the above-mentioned effect can also be achieved, wherein the material of the third active layer is not limited.
  • the composite electrode further includes a fourth active layer 5, which is disposed between the first active layer 2 and the second active layer 3.
  • the above-mentioned effect can also be achieved, wherein the material of the fourth active layer 5 is not limited.
  • the second active layer is arranged on a lateral surface of the first active layer.
  • the second active layer covers the first active layer, that is, the second active layer covers the exposed structure of the first active layer.
  • the second active layer can cover not only the surface of the first active layer, but also the side circumference of the first active layer.
  • the first active layer further comprises a ternary material, and the mass of the lithium iron manganese phosphate material accounts for 20%-80% of the total mass of the first active layer.
  • the first active layer also includes a ternary material, and the mass of the lithium iron manganese phosphate material accounts for 20%-80% of the total mass of the first active layer.
  • the mass of the lithium iron manganese phosphate material can account for 20%, 30%, 40%, 50%, 60%, 70%, 80% of the total mass of the first active layer.
  • the mass of the lithium iron manganese phosphate material cannot be too low or too high. If the mass of the lithium iron manganese phosphate material is too low, the mass of the ternary material will be too high, and the stability of the battery will be reduced. If the mass of the lithium iron manganese phosphate material is too high, the mass of the ternary material will be too low, and the energy density will be insufficient.
  • the average particle size Dv50 of the lithium manganese iron phosphate material is in the range of 0.2um-1um.
  • the average particle size Dv50 of lithium iron manganese phosphate material can be 0.2um, 0.3um, 0.4um, 0.5um, 0.6um, 0.7um, 0.8um, 0.9um, 1um, and the range value between any two of the above point values.
  • the general structural formula of the lithium manganese iron phosphate material is LiMnxFeyM1 -xyPO4 , wherein 0.2 ⁇ x ⁇ 0.8; 0.1 ⁇ y ⁇ 0.5; 0 ⁇ 1-xy ⁇ 0.2, and M represents a doping element, optionally including at least one of Al, Cu, Mg, Zn, Ni, Ti, V, Zr, Co, Ga, Sn, Sb, Nb and Ge.
  • the general structural formula of lithium iron manganese phosphate material is LiMn x Fe y M 1-xy PO 4 , wherein 0.2 ⁇ x ⁇ 0.8; 0.1 ⁇ y ⁇ 0.5; 0 ⁇ 1-xy ⁇ 0.2, M represents a doping element, optionally including at least one of Al, Cu, Mg, Zn, Ni, Ti, V, Zr, Co, Ga, Sn, Sb, Nb and Ge.
  • the molar proportion of manganese in the lithium iron manganese phosphate material is 20%-80%, and the performance is relatively good.
  • the molar proportion of manganese in the lithium iron manganese phosphate material can be 20%, 30%, 40%, 50%, 60%, 70%, 80%, and the range value between any two of the above point values.
  • the thickness of the first active layer accounts for 20%-80% of the total thickness of the active layer.
  • the first active layer includes lithium iron manganese phosphate material, and the thickness of the first active layer accounts for 20%-80% of the total thickness of the active layer, for example, it can be 20%, 30%, 40%, 50%, 60%, 70%, 80%, and the range value between any two of the above points.
  • the thickness of the lithium iron manganese phosphate material cannot be too low or too high.
  • other active layers include ternary materials, if the thickness of the lithium iron manganese phosphate material is too low, the thickness of the ternary material will be too high, and the stability of the battery will be reduced. If the thickness of the lithium iron manganese phosphate material is too high, the thickness of the ternary material will be too low, and the energy density will be insufficient.
  • the compaction density of the second active layer is greater than the compaction density of the first active layer.
  • the volume density of the active layer will increase, the porosity will decrease, the specific surface area will increase, the contact resistance will decrease, the SEI impedance of the electrode electrolyte interface film will decrease, and the charge exchange impedance will decrease.
  • a lower compaction density will instead cause the problem of low discharge specific capacity. This is mainly because the higher porosity causes some particles to form an insulating state and cannot participate in charging and discharging, while the electrode with a high compaction density has a higher fracture strength, thereby reducing the risk of electrode particles falling off and forming insulating particles during the cycle.
  • a high compaction density can significantly make the distribution of the pore size and pores of the electrode more uniform, the distribution of the conductive agent and the binder more uniform, reduce the contact resistance and charge exchange impedance of the electrode, and increase the active area that can participate in the reaction, thereby significantly improving the electrochemical performance of the material. Therefore, the active layer needs to have a suitable compaction density to improve the performance of the active layer.
  • the first active layer includes lithium iron manganese phosphate material
  • the second active layer includes a ternary material, and based on the structural characteristics of the lithium iron manganese phosphate material and the ternary material itself, the compaction density of the second active layer is greater than the compaction density of the first active layer.
  • the compaction density of the second active layer is 3.0 g/cm 3 -4.5 g/cm 3
  • the compaction density of the first active layer is 2.2 g/cm 3 -3.0 g/cm 3 .
  • the first active layer includes lithium iron manganese phosphate material. Based on the structural characteristics of the lithium iron manganese phosphate material, the compaction density of the first active layer is in the range of 2.2g/cm 3 -3.0g/cm 3 , and the compaction density of the first active layer has good application value within this range.
  • the second active layer includes ternary material. Based on the structural characteristics of the ternary material, the compaction density of the second active layer is in the range of 3.0g/cm 3 -4.5g/cm 3 , and the compaction density of the second active layer has good application value within this range.
  • the second active layer includes at least one of a ternary material or lithium cobalt oxide.
  • Lithium cobalt oxide is an inorganic compound with the chemical formula LiCoO 2 , and is generally used as a positive electrode material for lithium-ion batteries.
  • the energy density of the composite electrode can be regulated to achieve a highly stable, high energy density, and low-cost battery cell.
  • the second active layer includes at least one of a ternary material or lithium cobalt oxide.
  • the second active layer may include a ternary material or lithium cobalt oxide, and the second active layer may also include a mixture of a ternary material and lithium cobalt oxide, which is not specifically limited.
  • the second active layer may also include other materials for the positive electrode.
  • the average particle size Dv50 of the ternary material or lithium cobalt oxide included in the second active layer is in the range of 0.5um-20um.
  • the average particle size Dv50 of the ternary material or lithium cobalt oxide included in the second active layer can be 0.5um, 1um, 2um, 3um, 4um, 5um, 6um, 7um, 8um, 9um, 10um, 11um, 12um, 13um, 14um, 15um, 16um, 17um, 18um, 19um, 20um, and the range between any two of the above point values.
  • the general structural formula of the ternary material is LiNi a Co b N (1-ab) O 2 , wherein N optionally includes at least one of Mn, Zr, Al, B, Ta, Mo, W, Nb, Sb, and La, wherein 0.35 ⁇ a ⁇ 1.0, 0 ⁇ b ⁇ 0.35, and 0 ⁇ 1-ab ⁇ 0.35.
  • the general structural formula of the ternary material is LiNi a Co b N (1-ab) O 2 , wherein N optionally includes at least one of Mn, Zr, Al, B, Ta, Mo, W, Nb, Sb, and La, wherein 0.35 ⁇ a ⁇ 1.0, 0 ⁇ b ⁇ 0.35, and 0 ⁇ 1-ab ⁇ 0.35.
  • the ternary material can be divided into low-nickel ternary material, medium-nickel ternary material, and high-nickel ternary material, and according to whether it contains cobalt element, the ternary material can also be divided into cobalt-free ternary material, wherein the cobalt element can be replaced by other metal elements.
  • the specific type of the ternary material is not limited.
  • the ternary material in the first active layer and the second active layer is the same.
  • the ternary materials in the first active layer and the second active layer can be the same or different, but it is best if they are the same.
  • the advantage of being the same is that the lithium insertion amounts of the two active layers are similar and the expansion degrees are the same, which is beneficial to the stability of the electrode.
  • the ternary material includes at least one of 5-series single crystal ternary material, 5-series polycrystalline ternary material, 6-series single crystal ternary material, 6-series polycrystalline ternary material, 7-series single crystal ternary material, 7-series polycrystalline ternary material, 8-series single crystal ternary material, 8-series polycrystalline ternary material, 9-series single crystal ternary material, 9-series polycrystalline ternary material, or cobalt-free ternary material.
  • the ternary material in the present application is not specifically limited and can be at least one of 5-series single crystal ternary material, 5-series polycrystalline ternary material, 6-series single crystal ternary material, 6-series polycrystalline ternary material, 7-series single crystal ternary material, 7-series polycrystalline ternary material, 8-series single crystal ternary material, 8-series polycrystalline ternary material, 9-series single crystal ternary material, 9-series polycrystalline ternary material, or cobalt-free ternary material.
  • the first active layer includes a first active material, a conductive agent and a binder
  • the first active material includes a lithium manganese iron phosphate material coated with a conductive coating material, and the mass of the lithium manganese iron phosphate material coated with the conductive coating material accounts for 94%-97% of the total mass of the first active layer;
  • the second active layer includes a second active material, a conductive agent and a binder, the second active material includes a ternary material, and the ternary material accounts for 95%-98% of the total mass of the second active layer.
  • the first active layer includes a first active material, a conductive agent and a binder.
  • the first active material includes a lithium manganese iron phosphate material coated with a conductive coating material.
  • the mass of the lithium manganese iron phosphate material coated with the conductive coating material accounts for 94%-97% of the total mass of the first active layer.
  • the lithium manganese iron phosphate material coated with the conductive coating material is within this range (for example, it can be 94%, 95%, 96%, 97%, and the range value between any two of the above point values), and an active layer with excellent performance can be prepared, wherein the binder content can be 1.8%, 2%, 2.5%, 3%, etc., and the conductive agent content can be 1.8%, 2%, 2.5%, etc.
  • the second active layer includes a second active material, a conductive agent and a binder, the second active material includes a ternary material, the ternary material accounts for 95%-98% of the total mass of the second active layer, and the ternary material is within this range (95%, 96%, 97%, 98%, and the range value between any two of the above point values) to prepare an active layer with excellent performance, wherein the binder content can be 1.5%, 2%, 2.5%, etc., and the conductive agent content can be 1.8%, 2%, 2.5%, etc.
  • the present application also provides a method for preparing a composite electrode, comprising the following steps:
  • the first active material layer slurry and the second active material layer slurry are coated on the current collector, dried, and then cold pressed to obtain a composite electrode;
  • the first active material layer slurry and the second active material layer slurry are respectively formed into a first active layer and a second active layer, the first active layer is arranged on the current collector, and the second active layer is arranged on the side of the first active layer away from the current collector, the first active layer includes a lithium iron manganese phosphate material, and at least part of the surface of the lithium iron manganese phosphate material is provided with a conductive coating material, and the mass of the conductive coating material is 1.0%-10.0% of the mass of the lithium iron manganese phosphate material.
  • the composite electrode can be obtained by coating the first active material layer slurry and the second active material layer slurry on the current collector to form a multi-layer composite structure, drying and cold pressing.
  • the first active material layer slurry and the second active material layer slurry are respectively formed into the first active layer and the second active layer, the first active layer is arranged on the current collector, the second active layer is arranged on the side of the first active layer away from the current collector, the first active layer includes a lithium iron manganese phosphate material, and at least part of the surface of the lithium iron manganese phosphate material is provided with a conductive coating material.
  • the composite electrode designed includes a multi-layer active layer, at least part of the surface of the lithium iron manganese phosphate material is provided with a conductive coating material, the conductivity of the lithium iron manganese phosphate material is improved by the conductive coating material, the active layer containing the lithium iron manganese phosphate material is arranged in the inner layer, and the other active layer is arranged in the outer layer, so as to avoid directly exposing the active layer containing the lithium iron manganese phosphate material to the outside in a large area, and reduce the problem of the lithium iron manganese phosphate material provided with a conductive coating material catalyzing the decomposition of the electrolyte at a high potential under high conductivity.
  • the step of coating the first active material layer slurry and the second active material layer slurry on the current collector, drying, and then cold pressing to obtain a composite electrode includes the following steps:
  • the first active material layer slurry is coated on the current collector and dried, and then the second active material layer slurry is coated on the first active material layer and dried, and then cold pressed to obtain a composite electrode.
  • the composite electrode is prepared by the following method: preparing a current collector, coating a first active material layer slurry on the current collector, drying the first active material layer slurry through a drying mechanism to convert the first active material layer slurry into a first active layer, coating the second active material layer slurry on the first active layer, drying the second active material layer slurry to obtain two active layers on the current collector, cold pressing the pole piece through a cold pressing mechanism, and subjecting the current collector to cold pressing to compact the active layer on the current collector to obtain a composite electrode with a certain thickness.
  • the step of coating the first active material layer slurry and the second active material layer slurry on the current collector, drying, and cold pressing to obtain a composite electrode includes the following steps:
  • the first active material layer slurry and the second active material layer slurry are simultaneously coated on the current collector and dried at the same time. After drying, the mixture is cold pressed to obtain a composite electrode.
  • Coating the first active material layer slurry and the second active material layer slurry on the current collector at the same time can improve the coating efficiency and reduce the energy consumption of drying, that is, simplifying two drying times to one drying time. Moreover, the simultaneous coating will not form an interface between the two layers, the two active layers have good compatibility, and the structure is more stable.
  • the process of coating the first active material layer slurry and the second active material layer slurry on the current collector further includes the following steps:
  • a primer layer is firstly coated on the current collector, and then a first active material layer slurry and a second active material layer slurry are coated on the primer layer.
  • a high-viscosity coating is applied on the current collector, and then the first active material layer slurry and the second active material layer slurry are applied to enhance the bonding force between the active material and the substrate.
  • the drying temperature is 90°C-120°C
  • the cold pressing pressure is 20 tons-40 tons
  • the cold pressing temperature is 15°C-35°C.
  • the drying temperature is 90°C-120°C, for example, 90°C, 100°C, 110°C, 120°C.
  • the cold pressing pressure is 20 tons-40 tons, for example, 20 tons, 25 tons, 30 tons, 35 tons, 40 tons, and the range between any two of the above points. At the same time, cold pressing is performed at room temperature to simplify the operation.
  • the present application also provides a battery, comprising: a negative electrode plate, a positive electrode plate, a separator and an electrolyte, wherein the positive electrode plate is the composite electrode.
  • the battery prepared using the composite electrode has better cost performance.
  • the present application also provides an electrical device, which includes the battery.
  • the electrical equipment adopts the above cost-effective battery to improve the performance of the electrical equipment and increase its use value.
  • the composite electrode of the present application includes a current collector, a first active layer and a second active layer, wherein the first active layer is arranged on the current collector, and the second active layer is arranged on the side of the first active layer away from the current collector, and the first active layer includes a lithium iron manganese phosphate material, wherein at least part of the surface of the lithium iron manganese phosphate material is provided with a conductive coating material, and the conductivity of the lithium iron manganese phosphate material is improved by coating the conductive coating material on at least part of the surface of the lithium iron manganese phosphate material, and at the same time, the second active layer is arranged on the side of the first active layer away from the current collector, so as to reduce the risk of direct contact between the lithium iron manganese phosphate material coated with the conductive coating material in the first active layer and the electrolyte, reduce the risk of catalytic electrolyte decomposition at high potential, reduce the problem of gas production reaction and battery cell swelling, and improve the conductivity of the
  • the mass of the conductive coating material is 1.0%-10.0% of the mass of the lithium iron manganese phosphate material, for example, it can be 1.0%, 2.0%, 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, 8.0%, 9.0%, 10.0%, and the range between any two of the above points.
  • the second active layer covers the lithium iron manganese phosphate material layer, it can directly block the conductive coating material on at least part of the surface of the lithium iron manganese phosphate material, reducing the problem of the conductive coating material catalyzing the decomposition of the electrolyte at a high potential.
  • the amount of the conductive coating material can be increased to improve the conductivity of the lithium iron manganese phosphate material layer.
  • FIG1 is a schematic diagram of a process for preparing a composite electrode according to an embodiment of the present invention.
  • FIG2 is a schematic flow chart of another embodiment of a method for preparing a composite electrode of the present application.
  • FIG3 is a schematic flow chart of another embodiment of a method for preparing a composite electrode of the present application.
  • FIG4 is a schematic diagram of a process of another embodiment of a method for preparing a composite electrode of the present application.
  • FIG5 is a schematic diagram of the structure of the first active layer and the second active layer of the composite electrode of the present application.
  • FIG6 is a schematic structural diagram of an embodiment of a composite electrode of the present application.
  • FIG7 is a schematic structural diagram of another embodiment of the composite electrode of the present application.
  • FIG8 is a schematic structural diagram of another embodiment of the composite electrode of the present application.
  • FIG. 9 is a schematic structural diagram of another embodiment of the composite electrode of the present application.
  • connection can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined.
  • fixation can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined.
  • Batteries mentioned in this field can be divided into disposable batteries and rechargeable batteries according to whether they are rechargeable.
  • Common types of rechargeable batteries currently include: lead-acid batteries, nickel-metal hydride batteries and lithium-ion batteries.
  • Lithium-ion batteries are currently widely used in pure electric vehicles and hybrid vehicles. The capacity of lithium-ion batteries used for this purpose is relatively low, but they have larger output and charging current, and also have a longer service life, but the cost is higher.
  • the battery described in the embodiments of the present application refers to a rechargeable battery.
  • the embodiments disclosed in the present application will be described below mainly by taking a lithium-ion battery as an example. It should be understood that the embodiments disclosed in the present application are applicable to any other appropriate type of rechargeable battery.
  • the battery mentioned in the embodiments disclosed in the present application can be directly or indirectly applied to an appropriate device to power the device.
  • the battery mentioned in the embodiments disclosed in this application refers to a single physical module including one or more battery cells to provide a predetermined voltage and capacity.
  • Battery cells are the basic units in a battery, and can generally be divided into cylindrical battery cells, rectangular battery cells, and soft-pack battery cells according to the packaging method. The following will mainly focus on rectangular battery cells. It should be understood that the embodiments described below are also applicable to cylindrical battery cells or soft-pack battery cells in some aspects.
  • a battery cell includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator.
  • Lithium-ion battery cells mainly rely on the movement of lithium ions between the positive electrode sheet and the negative electrode sheet to work.
  • cylindrical battery cells the film structure of three layers of material is wound into a cylindrical electrode assembly, while in rectangular battery cells, the film structure is wound or stacked into an electrode assembly with a roughly rectangular shape.
  • the battery cell includes a shell, an electrode assembly and an electrolyte.
  • the electrode assembly is contained in the shell of the battery cell, and the electrode assembly includes a positive electrode sheet, a negative electrode sheet and a separator.
  • the shell includes a shell and an end cap.
  • the shell includes a housing formed by a plurality of walls and an opening. The end cap is arranged at the opening to close the housing chamber.
  • the housing chamber also contains an electrolyte.
  • the positive electrode sheet and the negative electrode sheet in the electrode assembly include tabs. In order to ensure that a large current passes without melting, the number of positive tabs is multiple and stacked together, and the number of negative tabs is multiple and stacked together.
  • the tabs are electrically connected to the electrode terminals located outside the battery cell through connecting members, and the electrode terminals generally include a positive electrode terminal and a negative electrode terminal.
  • the electrode terminal is generally arranged at the end cap portion.
  • a plurality of battery cells are connected in series and/or in parallel via the electrode terminals for application in various applications.
  • the application of batteries includes three levels: battery cells, battery modules and batteries.
  • the battery module is formed by electrically connecting a certain number of battery cells together and placing them in a frame in order to protect the battery cells from external impact, heat, vibration, etc.
  • the battery refers to the final state of the battery system installed in the electric vehicle.
  • the battery generally includes a box for encapsulating one or more battery cells.
  • the box generally consists of a cover and a box shell.
  • a plurality of mounting points for connecting with the vehicle body are arranged on the frame of the box or in the middle of the box shell. In order to improve the stability of the connection between the vehicle body and the battery, mounting parts are often arranged at the mounting points.
  • multiple battery cells are first integrated into a battery module, and then the battery module is packaged in a battery box to form a battery pack/battery box.
  • Commonly used battery modules generally include two end plates, between which multiple battery cells are arranged.
  • the end plate with the output pole of the battery module is also called the output pole end plate, and the end plate without the output pole of the battery module is also called the non-output pole end plate.
  • a battery pack may contain multiple battery modules in one row or multiple rows.
  • the arrangement of multiple rows of multiple battery modules may be double rows and multiple columns, multiple rows and double columns, multiple rows and multiple columns, etc.
  • the first end plate of each column is generally a head output extreme plate
  • the two adjacent end plates between two rows of battery modules are middle non-output extreme plates
  • the last end plate of each column is a tail non-output extreme plate
  • the head output extreme plate and one of the middle non-output extreme plates belong to the first row of battery modules
  • one of the middle non-output extreme plates and the tail output extreme plate belong to the second row of battery modules.
  • the battery module needs to be packaged into the battery box with the help of tooling, which is generally equipped with a clamping mechanism for clamping the battery module, such as a clamping claw, a suction cup, etc.
  • a clamping claw groove that matches the clamping claw is generally provided on the side of the end plate away from the battery cell, so that the clamping claw can be inserted to clamp and transport the battery module.
  • lithium iron phosphate materials Compared with lithium iron phosphate, lithium iron phosphate materials not only have a significantly higher energy density, but also have no deterioration in safety, which is almost equivalent to lithium iron phosphate, and has been much improved compared with ternary materials. Although lithium iron phosphate materials have many advantages, they have not been commercialized on a large scale. The main technical problems are as follows: lithium iron phosphate materials have poor conductivity, and it is difficult to meet the requirements by only relying on a small amount of conductive carbon added in the traditional formula. It is necessary to coat each particle with a layer of dense porous carbon to enhance the electronic conduction between particles. It is understandable that the higher the carbon content, the better the conductivity, and the better the rate performance of the battery.
  • porous carbon as a conductive coating material contains defects and oxygen-containing functional groups, which can catalyze the decomposition of the electrolyte.
  • other types of conductive coating materials may also contain impurities that catalyze the decomposition of the electrolyte, for example, active ingredient impurities in metal oxides also catalyze the decomposition of the electrolyte.
  • the present application designs a composite electrode, the composite electrode includes a multi-layer active layer, at least a portion of the surface of the lithium iron manganese phosphate material is provided with a conductive coating material, the conductivity of the lithium iron manganese phosphate material is improved by the conductive coating material, the active layer containing the lithium iron manganese phosphate material is arranged in the inner layer, and the other active layer is arranged in the outer layer, thus avoiding directly exposing the active layer containing the lithium iron manganese phosphate material to a large area, reducing the problem of the lithium iron manganese phosphate material provided with a conductive coating material catalyzing the decomposition of the electro
  • a composite electrode of the present application includes a current collector, a first active layer and a second active layer, wherein the first active layer is arranged on the current collector, and the second active layer is arranged on the side of the first active layer away from the current collector, and the first active layer includes a lithium iron manganese phosphate material, wherein at least a portion of the surface of the lithium iron manganese phosphate material is provided with a conductive coating material, and the mass of the conductive coating material is 1.0%-10.0% of the mass of the lithium iron manganese phosphate material.
  • the current collector refers to the structure or part that collects current.
  • metal foil such as copper foil and aluminum foil. It can also refer to the tabs. Its main function is to collect the current generated by the active materials of the battery so as to form a larger current for external output.
  • the active layer refers to a layered structure including an active material, wherein the active material refers to the positive electrode active material involved in the positive electrode, and the positive electrode active material can use a compound that can reversibly embed and de-embed Li + .
  • Coating refers to coating the surface of a material with conductive material to improve conductivity.
  • the conductive coating material refers to the conductive material coated on the surface of lithium manganese iron phosphate, such as carbon material, conductive polymer, etc. coated on the surface of lithium manganese iron phosphate particles.
  • the composite electrode of the present application improves the conductivity of the lithium iron manganese phosphate material by coating at least part of the surface of the lithium iron manganese phosphate material with a conductive coating material.
  • a second active layer 3 is arranged on the side of the first active layer 2 away from the current collector 1 to reduce the risk of direct contact between the lithium iron manganese phosphate material coated with the conductive coating material in the first active layer and the electrolyte, reduce the risk of catalytic electrolyte decomposition at high potential, reduce gas production reactions and battery cell swelling problems, and improve the conductivity of the composite electrode while reducing capacity attenuation and improving stability.
  • the mass of the conductive coating material is 1.0%-10.0% of the mass of the lithium iron manganese phosphate material, for example, it can be 1.0%, 2.0%, 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, 8.0%, 9.0%, 10.0%, and the range between any two of the above points.
  • the second active layer covers the lithium iron manganese phosphate material layer, it can directly block the conductive coating material on at least part of the surface of the lithium iron manganese phosphate material from contacting the electrolyte, reducing the risk of the conductive coating material catalyzing the decomposition of the electrolyte at a high potential.
  • the amount of the conductive coating material can be increased to improve the conductivity of the lithium iron manganese phosphate material layer.
  • one of the main functions of the second active layer is to cover the lithium manganese iron phosphate material layer.
  • the specific composition of the second active layer is not described. limited.
  • the mass of the conductive coating material on at least part of the surface of the lithium iron manganese phosphate material is 1%-5% of the mass of the lithium iron manganese phosphate material on at least part of the surface of the lithium iron manganese phosphate material.
  • the mass of the conductive coating material is 1.0%-5% of the mass of the lithium manganese iron phosphate material, for example, it can be 1.0%, 2.0%, 3.0%, 4.0%, 5.0%, and the range between any two of the above points.
  • the mass of the conductive coating material on at least part of the surface of the lithium iron manganese phosphate material is 1.3%-2.5% of the mass of the lithium iron manganese phosphate material on at least part of the surface of the lithium iron manganese phosphate material.
  • the mass of the conductive coating material is 1.3%-2.5% of the mass of the lithium manganese iron phosphate material on at least part of the surface of the lithium manganese iron phosphate material, the battery performance is better. Therefore, the mass of the conductive coating material is 1.3%-2.5% of the mass of the lithium manganese iron phosphate material, for example, it can be 1.3%, 1.5%, 1.8%, 2.0%, 2.3%, 2.5%, and a range value between any two of the above point values.
  • the conductive coating material is a carbon material.
  • the conductive coating material is a carbon material.
  • the porous carbon used as the coating material contains defects and oxygen-containing functional groups. These defects and oxygen-containing functional groups can catalyze the decomposition of the electrolyte.
  • the carbon material is provided on at least part of the surface of the lithium iron manganese phosphate material.
  • the carbon material is used to improve the conductivity of the lithium iron manganese phosphate material.
  • the active layer containing the lithium iron manganese phosphate material is provided in the inner layer, and the other active layer is provided in the outer layer. In this way, it is avoided that the active layer containing the lithium iron manganese phosphate material is directly exposed to the outside in a large area, and the lithium iron manganese phosphate material provided with the carbon material is reduced.
  • the problem of catalyzing the decomposition of the electrolyte at a high potential under a high conductivity condition By providing a layered active layer, the coating amount of the carbon material on at least part of the surface of the lithium iron manganese phosphate material can be increased, and the conductivity of the lithium iron manganese phosphate material can be improved, so as to solve the problem that the small amount of conductive carbon added in the traditional formula is difficult to meet the conductivity requirements.
  • the composite electrode further includes a third active layer, which is disposed between the current collector and the first active layer; and/or the composite electrode further includes a fourth active layer, which is disposed between the first active layer and the second active layer.
  • the composite electrode further includes a third active layer 4, and the third active layer is arranged between the current collector 1 and the first active layer 2.
  • the above-mentioned effect can also be achieved, wherein the material of the third active layer is not limited.
  • the composite electrode further includes a fourth active layer 5, which is disposed between the first active layer 2 and the second active layer 3.
  • the above-mentioned effect can also be achieved, wherein the material of the fourth active layer 5 is not limited.
  • the first active layer is a lithium iron manganese phosphate layer having a conductive coating material
  • the second active layer is a high-nickel ternary material layer
  • the fourth active layer is a medium-nickel ternary material layer
  • the first active layer is a lithium iron manganese phosphate layer having a high manganese content and a conductive coating material
  • the second active layer is a ternary material layer
  • the fourth active layer is a lithium iron manganese phosphate layer having a low manganese content and a conductive coating material.
  • the first active layer 2 and the second active layer 3 are used as a repeating unit, and a plurality of repeating units are arranged on the current collector 1.
  • the above-mentioned effect can also be achieved. That is, as long as the first active layer 2 is arranged in the inner layer of the composite electrode multilayer structure, the direct contact between the lithium manganese iron phosphate material in the first active layer and the electrolyte is reduced.
  • the second active layer may completely cover the first active layer 2 or may partially cover the first active layer 2, which is not specifically limited.
  • the second active layer is arranged on the side circumference of the first active layer.
  • the second active layer covers the first active layer, that is, the second active layer covers the exposed structure of the first active layer.
  • the second active layer can not only cover the surface of the first active layer, but also cover the side circumference of the first active layer.
  • the first active layer also includes a ternary material, and the mass of the lithium manganese iron phosphate material accounts for 20%-80% of the total mass of the first active layer.
  • ternary positive electrode materials are layered nickel-cobalt-manganese (aluminum) lithium oxide composite materials.
  • Nickel, cobalt, and manganese are transition metal elements.
  • the solid solution formed can be mixed in any proportion.
  • the increase in the proportion of nickel elements can improve the battery specific energy
  • the increase in the proportion of manganese elements can ensure structural stability
  • the increase in the proportion of cobalt elements can stabilize the layered structure of the material, which is beneficial to the cycle performance and rate performance of the battery.
  • ternary materials can also include materials that do not contain cobalt, for example, ternary materials obtained by using other metal elements instead of cobalt, such as ternary materials obtained by using Mo, Nb, etc. instead of cobalt.
  • the current compaction density of lithium iron phosphate is lower than that of lithium iron phosphate LFP.
  • the energy density can be improved at the material level, at the electrode level, due to the low compaction density of lithium iron phosphate, less active material is coated on the unit area of the substrate. In the end, the overall energy density has no obvious advantage over the LFP system.
  • the first active layer also includes a ternary material
  • the mass of the lithium manganese iron phosphate material accounts for 20%-80% of the total mass of the first active layer.
  • the mass of the lithium manganese iron phosphate material can account for 20%, 30%, 40%, 50%, 60%, 70%, 80% of the total mass of the first active layer, and the range value between any two of the above points.
  • the mass of the lithium manganese iron phosphate material It cannot be too low or too high. If the quality of lithium manganese iron phosphate material is too low, the quality of ternary material will be too high, and the stability of the battery will be reduced. If the quality of lithium manganese iron phosphate material is too high, the quality of ternary material will be too low, and the energy density will be insufficient.
  • the compaction density of lithium iron manganese phosphate is relatively low, the gram capacity and compaction density of the ternary material are generally relatively high.
  • the energy density of the composite electrode can be adjusted to achieve a highly stable, high energy density, and low-cost battery cell.
  • the average particle size Dv50 of the lithium manganese iron phosphate material is in the range of 0.2um-1um.
  • the average particle size Dv50 of lithium iron manganese phosphate material can be 0.2um, 0.3um, 0.4um, 0.5um, 0.6um, 0.7um, 0.8um, 0.9um, 1um, and the range value between any two of the above point values.
  • the general structural formula of the lithium manganese iron phosphate material is LiMnxFeyM1 -xyPO4 , wherein 0.2 ⁇ x ⁇ 0.8; 0.1 ⁇ y ⁇ 0.5; 0 ⁇ 1-xy ⁇ 0.2, and M represents a doping element, optionally including at least one of Al, Cu, Mg, Zn, Ni, Ti, V, Zr, Co, Ga, Sn, Sb, Nb and Ge.
  • the general structural formula of lithium iron manganese phosphate material is LiMn x Fe y M 1-xy PO 4 , wherein 0.2 ⁇ x ⁇ 0.8; 0.1 ⁇ y ⁇ 0.5; 0 ⁇ 1-xy ⁇ 0.2, M represents a doping element, optionally including at least one of Al, Cu, Mg, Zn, Ni, Ti, V, Zr, Co, Ga, Sn, Sb, Nb and Ge.
  • the molar proportion of manganese in the lithium iron manganese phosphate material is 20%-80%, and the performance is relatively good.
  • the molar proportion of manganese in the lithium iron manganese phosphate material can be 20%, 30%, 40%, 50%, 60%, 70%, 80%, and the range value between any two of the above point values.
  • the thickness of the first active layer accounts for 20%-80% of the total thickness of the active layer.
  • the first active layer includes lithium iron manganese phosphate material, and the thickness of the first active layer accounts for 20%-80% of the total thickness of the active layer, for example, it can be 20%, 30%, 40%, 50%, 60%, 70%, 80%, and the range value between any two of the above points.
  • the thickness of the lithium iron manganese phosphate material cannot be too low or too high.
  • other active layers include ternary materials, if the thickness of the lithium iron manganese phosphate material is too low, the thickness of the ternary material will be too high, and the stability of the battery will be reduced. If the thickness of the lithium iron manganese phosphate material is too high, the thickness of the ternary material will be too low, and the energy density will be insufficient.
  • the compaction density of the second active layer is greater than the compaction density of the first active layer.
  • Compacted density surface density/(thickness of the pole piece after rolling - thickness of the current collector), unit: g/cm 3 .
  • the compaction density of the active layer is calculated based on the mass of all materials in the electrode after rolling.
  • the active layer also includes conductive carbon and binder.
  • the volume density of the active layer will increase, the porosity will decrease, the specific surface area will increase, the contact resistance will decrease, the SEI impedance of the electrode electrolyte interface film will decrease, and the charge exchange impedance will decrease.
  • a lower compaction density will instead cause the problem of low discharge specific capacity. This is mainly because the higher porosity causes some particles to form an insulating state and cannot participate in charging and discharging, while the electrode with a high compaction density has a higher fracture strength, thereby reducing the risk of electrode particles falling off and forming insulating particles during the cycle.
  • a high compaction density can significantly make the distribution of the pore size and pores of the electrode more uniform, the distribution of the conductive agent and the binder more uniform, reduce the contact resistance and charge exchange impedance of the electrode, and increase the active area that can participate in the reaction, thereby significantly improving the electrochemical performance of the material. Therefore, the active layer needs to have a suitable compaction density to improve the performance of the active layer.
  • the first active layer includes lithium iron manganese phosphate material
  • the second active layer includes a ternary material, and based on the structural characteristics of the lithium iron manganese phosphate material and the ternary material itself, the compaction density of the second active layer is greater than the compaction density of the first active layer.
  • the compaction density of the second active layer is 3.0 g/cm 3 -4.5 g/cm 3
  • the compaction density of the first active layer is 2.2 g/cm 3 -3.0 g/cm 3 .
  • the first active layer includes lithium iron manganese phosphate material. Based on the structural characteristics of the lithium iron manganese phosphate material, the compaction density of the first active layer is in the range of 2.2g/cm 3 -3.0g/cm 3 , and the compaction density of the first active layer has good application value within this range.
  • the second active layer includes ternary material. Based on the structural characteristics of the ternary material, the compaction density of the second active layer is in the range of 3.0g/cm 3 -4.5g/cm 3 , and the compaction density of the second active layer has good application value within this range.
  • the second active layer includes at least one of a ternary material or lithium cobalt oxide.
  • Lithium cobalt oxide is an inorganic compound with the chemical formula LiCoO 2 , and is generally used as a positive electrode material for lithium-ion batteries.
  • the energy density of the composite electrode can be regulated to achieve a highly stable, high energy density, and low-cost battery cell.
  • the second active layer includes at least one of a ternary material or lithium cobalt oxide.
  • the second active layer may include a ternary material or lithium cobalt oxide, and the second active layer may also include a mixture of a ternary material and lithium cobalt oxide, which is not specifically limited.
  • the second active layer may also include other materials for the positive electrode.
  • this design can improve the energy density of the battery cell and make the energy density customizable; in addition, compared with pure ternary materials, the increased content of lithium iron manganese phosphate can reduce the risk of fire of ternary materials. At the same time, since the cost of ternary materials is relatively high, the composite electrode of the present application can also reduce costs and improve cost performance.
  • Lithium manganese iron phosphate materials are difficult to remove lithium at high SOC (State Of Charge), which means that batteries made of this material are It is difficult to charge the cell when it is nearly fully charged. The polarization of the battery is serious, and the lithium ions in the positive electrode material are difficult to escape and are embedded in the negative electrode. Therefore, it takes a lot of time to fully charge.
  • SOC State Of Charge
  • the degree of lithium delithiation of the surface ternary material is higher than that of the lower lithium manganese iron phosphate, which alleviates the problem of difficulty in lithium delithiation at high SOC of lithium manganese iron phosphate and reduces the polarization of the electrode.
  • the lithium manganese iron phosphate active material layer coated by the conductive coating material is first coated on the current collector, and then a layer of ternary material is coated, which is equivalent to a physical isolation layer, reducing the direct contact between the electrolyte and the conductive coating material and reducing gas production.
  • This structure can appropriately increase the content of the conductive coating material of the lithium manganese iron phosphate to achieve the comprehensive advantages of conductive performance and stability.
  • the average particle size Dv50 of the ternary material or lithium cobalt oxide included in the second active layer is in the range of 0.5um-20um.
  • the average particle size Dv50 of the ternary material or lithium cobalt oxide included in the second active layer can be 0.5um, 1um, 2um, 3um, 4um, 5um, 6um, 7um, 8um, 9um, 10um, 11um, 12um, 13um, 14um, 15um, 16um, 17um, 18um, 19um, 20um, and the range between any two of the above point values.
  • the general structural formula of the ternary material is LiNi a Co b N (1-ab) O 2 , wherein N optionally includes at least one of Mn, Zr, Al, B, Ta, Mo, W, Nb, Sb, and La, wherein 0.35 ⁇ a ⁇ 1.0, 0 ⁇ b ⁇ 0.35, and 0 ⁇ 1-ab ⁇ 0.35.
  • the general structural formula of the ternary material is LiNi a Co b N (1-ab) O 2 , wherein N optionally includes at least one of Mn, Zr, Al, B, Ta, Mo, W, Nb, Sb, and La, wherein 0.35 ⁇ a ⁇ 1.0, 0 ⁇ b ⁇ 0.35, and 0 ⁇ 1-ab ⁇ 0.35.
  • the ternary material can be divided into low-nickel ternary material, medium-nickel ternary material, and high-nickel ternary material, and according to whether it contains cobalt element, the ternary material can also be divided into cobalt-free ternary material, wherein the cobalt element can be replaced by other metal elements.
  • the specific type of the ternary material is not limited.
  • the ternary material in the first active layer and the second active layer is the same.
  • the ternary materials in the first active layer and the second active layer can be the same or different, but it is best if they are the same.
  • the advantage of being the same is that the lithium insertion amounts of the two active layers are similar and the expansion degrees are the same, which is beneficial to the stability of the electrode.
  • the ternary material includes at least one of 5-series single crystal ternary material, 5-series polycrystalline ternary material, 6-series single crystal ternary material, 6-series polycrystalline ternary material, 7-series single crystal ternary material, 7-series polycrystalline ternary material, 8-series single crystal ternary material, 8-series polycrystalline ternary material, 9-series single crystal ternary material, 9-series polycrystalline ternary material, or cobalt-free ternary material.
  • 5 series ternary materials refer to ternary materials with a molar ratio of nickel metal greater than or equal to 50% and less than 60%.
  • 6 series ternary materials refer to ternary materials with a molar ratio of nickel metal greater than or equal to 60% and less than 70%.
  • 7 series ternary materials refer to ternary materials with a molar ratio of nickel metal greater than or equal to 70% and less than 80%.
  • 8 series ternary materials refer to ternary materials with a molar ratio of nickel metal greater than or equal to 80% and less than 90%.
  • 9 series ternary materials refer to ternary materials with a molar ratio of nickel metal greater than or equal to 90%, such as Ni90, Ni92, Ni95, etc. As the nickel content gradually increases, the battery energy density also increases.
  • the medium nickel ternary material has a relatively high nickel content, a low nickel content, and a high cobalt content, so its own stability is sufficiently guaranteed.
  • single crystal materials generate less heat and have high stability.
  • Nickel ternary in single crystal currently achieves a good balance in multiple dimensions such as economy, stability, energy density, and cycle life.
  • Cobalt-free ternary materials refer to ternary materials that do not contain cobalt, for example, ternary materials in which the cobalt element can be replaced by other elements.
  • Single crystal ternary materials and polycrystalline ternary materials are named according to the morphology of the materials themselves. From the morphology point of view, single crystal is a single dispersed particle, while the corresponding polycrystalline ternary material is a secondary particle of primary particle agglomeration.
  • single crystal materials are more suitable for high voltage. At the same time, there are no grain boundaries inside single crystal materials, which can improve the cycle stability of ternary materials and extend the cycle life of batteries. Under the same ratio of nickel, cobalt and manganese, the gram capacity of single crystal ternary materials is slightly lower than that of polycrystalline ternary materials, but because of its higher voltage, the overall energy density of the material is already similar to that of the current high-nickel ternary materials. The disadvantage of single crystal ternary materials is that the rate performance is poor, the production process is more complicated, and the material price is relatively high.
  • the ternary material in the present application is not specifically limited, and can be at least one of 5-series single crystal ternary material, 5-series polycrystalline ternary material, 6-series single crystal ternary material, 6-series polycrystalline ternary material, 7-series single crystal ternary material, 7-series polycrystalline ternary material, 8-series single crystal ternary material, 8-series polycrystalline ternary material, 9-series single crystal ternary material, 9-series polycrystalline ternary material, or cobalt-free ternary material.
  • the first active layer includes a first active material, a conductive agent and a binder
  • the first active material includes a lithium manganese iron phosphate material coated with a conductive coating material
  • the mass of the lithium manganese iron phosphate material coated with the conductive coating material accounts for 94%-97% of the total mass of the first active layer
  • the second active layer includes a second active material, a conductive agent and a binder
  • the second active material includes a ternary material, and the ternary material accounts for 95%-98% of the total mass of the second active layer.
  • the first active layer includes a first active material, a conductive agent and a binder.
  • the first active material includes a lithium manganese iron phosphate material coated with a conductive coating material.
  • the mass of the lithium manganese iron phosphate material coated with the conductive coating material accounts for 94%-97% of the total mass of the first active layer.
  • the lithium manganese iron phosphate material coated with the conductive coating material is within this range (for example, it can be 94%, 95%, 96%, 97%, and the range value between any two of the above point values), and an active layer with excellent performance can be prepared, wherein the binder content can be 1.8%, 2%, 2.5%, 3%, etc., and the conductive agent content can be 1.8%, 2%, 2.5%, etc.
  • the second active layer includes a second active material, a conductive agent and a binder, the second active material includes a ternary material, the ternary material accounts for 95%-98% of the total mass of the second active layer, and the ternary material is within this range (95%, 96%, 97%, 98%, and the range value between any two of the above point values) to prepare an active layer with excellent performance, wherein the binder content can be 1.5%, 2%, 2.5%, etc., and the conductive agent content can be 1.8%, 2%, 2.5%, etc.
  • Too little conductive agent will lead to poor conductivity, and too much will lead to reduced energy density.
  • a moderate amount of binder can prevent the coating from falling off and has good heat resistance. Too little will lead to insufficient adhesion, and too much will lead to excessive slurry viscosity.
  • the present application also provides a method for preparing a composite electrode, comprising the following steps: coating a first active material layer slurry and a second active material layer slurry on a current collector, drying, and cold pressing to obtain a composite electrode; wherein the first active material layer slurry and the second active material layer slurry are respectively formed into a first active layer and a second active layer, the first active layer is arranged on the current collector, and the second active layer is arranged on the side of the first active layer away from the current collector, the first active layer includes a lithium iron manganese phosphate material, and at least a portion of the surface of the lithium iron manganese phosphate material is provided with a conductive coating material, and the mass of the conductive coating material is 1.0%-10.0% of the mass of the lithium iron manganese phosphate material.
  • the first active material layer slurry refers to a material used to prepare the first active layer
  • the second active material layer slurry refers to a material used to prepare the second active layer
  • Drying refers to the process of evaporating the solvent in the slurry and removing the solvent. This allows the pole piece to have a lower solvent content. If the solvent content is too high, the lithium battery will consume excessive lithium during the formation stage, causing irreversible loss of lithium, resulting in reduced capacity, battery bloating and other problems, affecting battery performance.
  • Cold pressing refers to compressing the electrode pole piece. After the positive electrode coating is dried, it is necessary to roll the pole piece during the process time. Rolling means compacting the pole piece.
  • Hot pressing compaction is higher than cold pressing, and the rebound rate is lower, which can reduce the rolling force; but the cold pressing process is relatively simple and easy to operate and control.
  • the main equipment of the roller reaches the following process values, compaction density, rebound rate, and elongation. At the same time, it should be noted that there are no brittle pieces, hard lumps, falling materials, wavy edges, etc. on the surface of the pole piece, and no fractures are allowed in the gap.
  • the pole piece rolling process can reduce the elongation and width of the pole piece during the rolling process, reduce the destruction rate of the pore structure of the pole piece coating material; improve the thickness consistency of the pole piece coating to improve the cross-sectional shape of the pole piece; improve the compaction density consistency of the electrode material after the pole piece is rolled; and reduce the rebound of the electrode material on the surface after the pole piece is rolled.
  • the pole piece rolling process can also ensure that the pole piece surface is smooth and flat, prevent burrs on the coating surface from piercing the diaphragm and causing a short circuit; compact the pole piece coating material to reduce the volume of the pole piece to increase the energy density of the battery; make the active material and conductive agent particles in closer contact to improve electronic conductivity; enhance the bonding strength between the coating material and the current collector, reduce the occurrence of powder loss of the electrode during the cycle, and improve the cycle life and stability of the battery.
  • two rollers can be used to compress the pole piece, so that friction is generated between the roller and the battery pole piece; the battery pole piece is pulled into the rotating roller pair, and the battery pole piece is compressed and deformed.
  • the rolling of the battery pole piece is the process of compacting the battery material on the positive and negative pole pieces, which can increase the compaction density of the positive or negative electrode material.
  • the appropriate compaction density can increase the discharge capacity of the battery, reduce the internal resistance, reduce the polarization loss, extend the cycle life of the battery, and improve the utilization rate of the lithium-ion battery.
  • the composite electrode can be obtained by coating the first active material layer slurry and the second active material layer slurry on the current collector to form a multi-layer composite structure, drying and cold pressing.
  • the first active material layer slurry and the second active material layer slurry are respectively formed into the first active layer and the second active layer, the first active layer is arranged on the current collector, the second active layer is arranged on the side of the first active layer away from the current collector, the first active layer includes a lithium iron manganese phosphate material, and at least part of the surface of the lithium iron manganese phosphate material is provided with a conductive coating material.
  • the composite electrode designed includes a multi-layer active layer, at least part of the surface of the lithium iron manganese phosphate material is provided with a conductive coating material, the conductivity of the lithium iron manganese phosphate material is improved by the conductive coating material, the active layer containing the lithium iron manganese phosphate material is arranged in the inner layer, and the other active layer is arranged in the outer layer, so as to avoid directly exposing the active layer containing the lithium iron manganese phosphate material to the outside in a large area, and reduce the problem of the lithium iron manganese phosphate material provided with a conductive coating material catalyzing the decomposition of the electrolyte at a high potential under high conductivity.
  • the following steps are included: coating the first active material layer slurry on the current collector, drying, and then coating the second active material layer slurry on the first active material layer, drying, and cold pressing to obtain a composite electrode.
  • the composite electrode is prepared by the following method: preparing a current collector, coating a first active material layer slurry on the current collector, and drying the first active material layer slurry through a drying mechanism to convert the first active material layer slurry into a first active layer. Then, coating the second active material layer slurry on the first active layer, and drying the second active material layer slurry to obtain two active layers on the current collector.
  • the electrode is cold pressed by a cold pressing mechanism, and the current collector is cold pressed to compact the active layer on the current collector to obtain a composite electrode with a certain thickness.
  • the following steps are included: coating the first active material layer slurry and the second active material layer slurry on the current collector at the same time, drying them at the same time, and after drying, cold pressing them to obtain a composite electrode.
  • the simultaneous coating process of two layers can be realized.
  • by using coating equipment and customizing the corresponding gasket it is possible to extrude two slurries simultaneously and coat them on the current collector; simultaneously coating the first active material layer slurry and the second active material layer slurry can improve the coating efficiency and reduce the energy consumption of drying, that is, simplifying two drying times to one drying time, and the simultaneous coating will not form an interface between the two layers, the two active layers have good compatibility, and the structure is more stable.
  • the process of coating the first active material layer slurry and the second active material layer slurry on the current collector also includes the following steps: first coating a primer on the current collector, and then coating the first active material layer slurry and the second active material layer slurry on the primer.
  • Primer refers to a high-adhesion coating used to enhance the adhesion between the active material layer and the current collector.
  • a high-viscosity coating is applied on the current collector, and then the first active material layer slurry and the second active material layer slurry are applied to enhance the bonding force between the active material and the substrate.
  • the drying temperature is 90°C-120°C
  • the cold pressing pressure is 20 tons-40 tons
  • the cold pressing temperature is 15°C-35°C.
  • the drying temperature is 90°C-120°C, for example, 90°C, 100°C, 110°C, 120°C.
  • the cold pressing pressure is 20 tons-40 tons, for example, 20 tons, 25 tons, 30 tons, 35 tons, 40 tons, and the range between any two of the above points. At the same time, cold pressing is performed at room temperature to simplify the operation.
  • the present application also provides a battery, comprising: a negative electrode sheet, a positive electrode sheet, a separator and an electrolyte, wherein the positive electrode sheet is the above-mentioned composite electrode. Since the composite electrode adopts all the technical solutions of all the above-mentioned embodiments, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be described one by one here.
  • the battery prepared using the composite electrode has better cost performance.
  • the present application also provides an electrical device, which includes the above-mentioned battery. Since the battery adopts all the technical solutions of all the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be described one by one here.
  • the electrical equipment adopts the above cost-effective battery to improve the performance of the electrical equipment and increase its use value.
  • the positive electrode active material carbon-coated lithium manganese iron phosphate (carbon content 1%), conductive carbon black, binder PVDF and solvent N-methylpyrrolidone (NMP) are uniformly stirred in a weight ratio of 95:2:3:100 to obtain a uniformly mixed first active layer slurry; the first active layer slurry is uniformly coated on a 15-micron thick aluminum foil current collector and then dried at 110°C.
  • the cathode active material five-series single crystal ternary material, conductive carbon black, binder PVDF and solvent N-methylpyrrolidone (NMP) are uniformly stirred at a weight ratio of 95:2:2:100 to obtain a uniformly mixed second active layer slurry; the second active layer slurry is uniformly coated on the dried first active layer, and then dried at 110°C. After cold pressing at a pressure of 20-40 tons, a composite electrode with a coating thickness of about 100um can be obtained.
  • the ratio of the thickness of the first membrane active layer to the thickness of the second active layer is 5:5.
  • Ethylene carbonate (EC), polycarbonate (PC), and dimethyl carbonate (DMC) are mixed in a volume ratio of 1:1:1, and then LiPF 6 is uniformly dissolved in the above solution to obtain an electrolyte.
  • the concentration of LiPF 6 is 1 mol/L.
  • the positive electrode sheets, separators, and negative electrode sheets in the above-mentioned embodiments or comparative examples are stacked and wound in order to obtain an electrode assembly; the electrode assembly is placed in an outer package, and the above-prepared electrolyte is added. After packaging, standing, formation, aging and other processes, a secondary battery is obtained.
  • Example 1 On the basis of Example 1, with other conditions unchanged, the experimental parameters were changed (as shown in Table 1) to obtain the experimental data of Examples 2 to 11 and Comparative Examples 1 to 3.
  • Each battery is charged at a rate of 0.33C to a voltage of 4.2V at room temperature, and then discharged at a rate of 0.33C to a voltage of 2.0V.
  • the reversible capacity is measured as C0.
  • the total number of cycles is then recorded as X-Cycle.
  • the embodiments include a first active layer and a second active layer, and their cycle life is greater than that of the comparative example.
  • the carbon coating amount needs to be set within an appropriate range.
  • the thicker the thickness of the first active layer the greater the resistance, and the lower the energy density. Therefore, the thickness of the first active layer needs to be set within an appropriate range.
  • the more ternary material content in the first active layer the lower the resistance, the higher the energy density, but the cycle life will decrease.
  • the use of a composite electrode structure can effectively improve the comprehensive performance of the composite electrode.

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Abstract

涉及锂离子电池技术领域，特别涉及一种复合电极及其制备方法、电池和用电设备。复合电极包括集流体、第一活性层和第二活性层，第一活性层设置在集流体上，第二活性层设置在第一活性层背离集流体的一侧，第一活性层包括磷酸锰铁锂材料，磷酸锰铁锂材料的至少部分表面设有导电包覆材料，导电包覆材料的质量为磷酸锰铁锂材料质量的百分之一至十。通过导电包覆材料来提高磷酸锰铁锂材料的导电性，采用在第一活性层背离集流体的一侧设置第二活性层，降低第一活性层中包覆有导电包覆材料的磷酸锰铁锂材料与电解液直接接触的风险，降低高电位下催化电解液分解的风险，减少产气反应与电芯鼓胀的问题，在提高复合电极导电性的同时，降低容量衰减。

Description

复合电极及其制备方法、电池和用电设备
相关申请
本申请要求于2022年11月03日申请的、申请号为202211396687.6的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及锂离子电池技术领域，特别涉及一种复合电极及其制备方法、电池和用电设备。
背景技术
目前商用锂离子电池的正极材料主要有两种：三元含锂化合物与磷酸铁锂。三元材料的优点是能量密度高，适合长续航汽车，但缺点是钴镍等元素价格较高，而且存在安全风险，更容易引发热失控起火。相比于三元材料，磷酸铁锂的安全性会提高很多，而且由于不含稀有过渡金属元素，成本也更低廉。然而，磷酸铁锂的能量密度较低，会导致续航里程短。在这个背景下，开发出一种既高能量密度和低成本，又具有高安全特性的材料尤为重要。磷酸锰铁锂就是这样的一种新型材料。
磷酸锰铁锂材料的晶体结构与磷酸铁锂相同，都属于橄榄石晶型，不同点在于在磷酸铁锂的基础上，使用Mn原子部分替代Fe原子。磷酸锰铁锂材料不仅能量密度相比于磷酸铁锂能大幅提高，安全性却没有恶化，几乎与磷酸铁锂相当，但是磷酸锰铁锂材料导电性不好。
发明内容
本申请的主要目的是提供一种复合电极，旨在提高电极的综合性能。
为实现上述目的，本申请提出的一种复合电极，所述复合电极包括集流体、第一活性层和第二活性层，所述第一活性层设置在所述集流体上，所述第二活性层设置在所述第一活性层背离所述集流体的一侧，所述第一活性层包括磷酸锰铁锂材料，其中，所述磷酸锰铁锂材料的至少部分表面设有导电包覆材料，所述导电包覆材料的质量为所述磷酸锰铁锂材料质量的1.0％-10.0％。
可选地，所述导电包覆材料的质量为所述磷酸锰铁锂材料质量的1％-5％。
导电包覆材料的量越多，导电性越好，电池的倍率性能就会越好。但是导电包覆材料含量进一步提高，实际的活性材料含量就会降低，电极的能量密度也会损失。因此，导电包覆材料的质量为磷酸锰铁锂材料质量的1.0％-5％，例如可以是1.0％、2.0％、3.0％、4.0％、5.0％，以及上述任意两个点值之间的范围值。
可选地，所述导电包覆材料的质量为所述磷酸锰铁锂材料质量的1.3％-2.5％。
导电包覆材料的质量为所述磷酸锰铁锂材料质量的1.3％-2.5％时，电池的性能较佳，因此，导电包覆材料的质量为磷酸锰铁锂材料质量的1.3％-2.5％，例如可以是1.3％、1.5％、1.8％、2.0％、2.3％、2.5％，以及上述任意两个点值之间的范围值。
可选地，所述导电包覆材料为碳材料。
导电包覆材料为碳材料，作为包覆材料的多孔碳中含有缺陷和含氧官能团，这些缺陷和含氧官能团能催化电解液分解，磷酸锰铁锂材料的至少部分表面设置有碳材料，通过碳材料提高磷酸锰铁锂材料的导电性，将含有磷酸锰铁锂材料的活性层设置在内层，另外的活性层设置在外层，如此，避免直接将含有磷酸锰铁锂材料的活性层大面积暴露在外，降低设有碳材料的磷酸锰铁锂材料，在高导电情况下的在高电位下催化电解液分解的问题。通过层状活性层的设置，可以提高磷酸锰铁锂材料的至少部分表面的碳材料的包覆量，提高磷酸锰铁锂材料的导电性，以解决传统配方中添加的少量导电碳难以满足导电性的要求。
导电包覆材料的量越多，导电性越好，电池的倍率性能就会越好。但是导电包覆材料含量进一步提高，实际的活性材料含量就会降低，电极的能量密度也会损失。因此，导电包覆材料的质量为磷酸锰铁锂材料质量的1.0％-10.0％，例如可以是1.0％、2.0％、3.0％、4.0％、5.0％、6.0％、7.0％、8.0％、9.0％、10.0％，以及上述任意两个点值之间的范围值。
可选地，所述复合电极还包括第三活性层，所述第三活性层设于所述集流体与所述第一活性层之间；
和/或，所述复合电极还包括第四活性层，所述第四活性层设于所述第一活性层与所述第二活性层之间。
本申请中，在满足第二活性层遮盖第一活性层的基础上，复合电极还包括第三活性层4，第三活性层设于集流体1与第一活性层2之间，此时，也能实现上述的效果，其中，第三活性层的材料不做限定。
还可以理解的是，复合电极还包括第四活性层5，第四活性层设于第一活性层2与第二活性层3之间，此时，也能实现上述的效果，其中，第四活性层5的材料不做限定。
可选地，所述第二活性层设置在所述第一活性层的侧周面。
可以理解的是，第一活性层2被遮盖的面积越多，第一活性层中的磷酸锰铁锂材料与电解液的直接 接触面积会越少，为了进一步减少第一活性层中的磷酸锰铁锂材料与电解液的直接接触，第二活性层覆盖第一活性层，也即，第二活性层将第一活性层暴露在外的结构都遮盖住，例如，第二活性层不仅可以遮盖第一活性层的表面，还可以遮盖第一活性层的侧周面。
可选地，所述第一活性层还包括三元材料，所述磷酸锰铁锂材料的质量占所述第一活性层总质量的20％-80％。
为了提高复合电极的能量密度，第一活性层还包括三元材料，且磷酸锰铁锂材料的质量占第一活性层总质量的20％-80％，例如，磷酸锰铁锂材料的质量可以占第一活性层总质量的20％、30％、40％、50％、60％、70％、80％，其中，磷酸锰铁锂材料的质量不能过低和过高，磷酸锰铁锂材料的质量过低会导致三元材料质量过高，电池的稳定性降低，磷酸锰铁锂材料的质量过高会导致三元材料质量过低，能量密度不足。
可选地，所述磷酸锰铁锂材料的平均粒径Dv50的范围值为0.2um-1um。
磷酸锰铁锂材料的离子传导能力很差，颗粒太大，锂离子传输路径长，动力学性能差，若颗粒尺寸做的很小，动力学性能好，但是加工性差，很难在集流体上进行涂布，因此磷酸锰铁锂材料的平均粒径Dv50可以为0.2um、0.3um、0.4um、0.5um、0.6um、0.7um、0.8um、0.9um、1um，以及上述任意两个点值之间的范围值。
可选地，所述磷酸锰铁锂材料的结构通式为LiMnxFeyM1-x-yPO4，式中，0.2≤x≤0.8；0.1≤y≤0.5；0≤1-x-y≤0.2，M表示掺杂元素，可选地包括Al、Cu、Mg、Zn、Ni、Ti、V、Zr、Co、Ga、Sn、Sb、Nb和Ge中的至少一种。
磷酸锰铁锂材料的结构通式为LiMnxFeyM1-x-yPO4，式中，0.2≤x≤0.8；0.1≤y≤0.5；0≤1-x-y≤0.2，M表示掺杂元素，可选地包括Al、Cu、Mg、Zn、Ni、Ti、V、Zr、Co、Ga、Sn、Sb、Nb和Ge中的至少一种。磷酸锰铁锂材料中锰的摩尔占比为20％-80％，性能比较好，例如，磷酸锰铁锂材料中锰的摩尔占比可以是20％、30％、40％、50％、60％、70％、80％，以及上述任意两个点值之间的范围值。
可选地，所述第一活性层的厚度占活性层总厚度的20％-80％。
第一活性层包括磷酸锰铁锂材料，第一活性层的厚度占活性层总厚度的20％-80％，例如可以是20％、30％、40％、50％、60％、70％、80％，以及上述任意两个点值之间的范围值。磷酸锰铁锂材料的厚度不能过低和过高，例如，当其他活性层包括三元材料时，磷酸锰铁锂材料的厚度过低会导致三元材料厚度过高，电池的稳定性降低，磷酸锰铁锂材料的厚度过高会导致三元材料厚度过低，能量密度不足。
可选地，所述第二活性层的压实密度大于所述第一活性层的压实密度。
随着压实密度的上升，活性层的体积密度会上升，孔隙率会下降，比表面积上升，接触电阻下降，电极电解液界面膜SEI阻抗会降低，电荷交换阻抗下降。较低的压实密度反而会造成放电比容量低的问题，这主要是较高的孔隙率造成部分颗粒形成绝缘状态，无法参与充放电，而高压实密度的电极有更高的断裂强度，从而降低在循环过程中电极颗粒脱落，形成绝缘状态颗粒的风险。高的压实密度可以明显使电极的孔径和孔隙的分布更加均匀，导电剂和粘结剂分布更加均匀，降低电极的接触电阻和电荷交换阻抗，增大能够参与反应的活性面积，从而显著的提高材料的电化学性能。因此，活性层需要有合适的压实密度，以提高活性层的性能。基于第一活性层包括磷酸锰铁锂材料，第二活性层包括三元材料，基于磷酸锰铁锂材料和三元材料本身的结构特性，第二活性层的压实密度大于第一活性层的压实密度。
可选地，所述第二活性层的压实密度为3.0g/cm3-4.5g/cm3，所述第一活性层的压实密度为2.2g/cm3-3.0g/cm3。
第一活性层包括磷酸锰铁锂材料，基于磷酸锰铁锂材料本身的结构特性，第一活性层的压实密度范围为2.2g/cm3-3.0g/cm3，第一活性层的压实密度在该范围内具有较好的应用价值。第二活性层包括三元材料，基于三元材料本身的结构特性，第二活性层的压实密度范围为3.0g/cm3-4.5g/cm3，第二活性层的压实密度在该范围内具有较好的应用价值。
可选地，所述第二活性层包括三元材料或钴酸锂中的至少一种。
钴酸锂是一种无机化合物，化学式为LiCoO2，一般使用作锂离子电池的正电极材料。
由于磷酸锰铁锂的压实密度低，导致在单位面积基材上涂布的活性材料更少，最终整体的能量密度相比于LFP体系优势不明显；而三元材料的克容量和压实密度普遍较高，通过调控第一活性层与第二活性层的材料来调控复合电极的能量密度，实现高稳定、高能量密度的、低成本的电芯。
为此，第二活性层包括三元材料或钴酸锂中的至少一种，例如，第二活性层可以包括三元材料或钴酸锂，第二活性层还可以包括三元材料与钴酸锂的混合，具体不做限定。当然，除了三元材料与钴酸锂之外，第二活性层还可以包括其他的用于正极的材料。
可选地，所述第二活性层中包括的三元材料或钴酸锂的平均粒径Dv50的范围值为0.5um-20um。
可以理解的是，颗粒太大锂离子传输路径长，动力学性能差，若颗粒尺寸做的很小，动力学性能好，但是加工性差，很难在集流体上进行涂布。因此，第二活性层中包括的三元材料或钴酸锂的平均粒径Dv50可以为0.5um、1um、2um、3um、4um、5um、6um、7um、8um、9um、10um、11um、12um、13um、14um、15um、16um、17um、18um、19um、20um，以及上述任意两个点值之间的范围值。
可选地，当所述第二活性层包括三元材料时，所述三元材料的结构通式为LiNiaCobN(1-a-b)O2，式中，N可选地包括Mn、Zr、Al、B、Ta、Mo、W、Nb、Sb、La中的至少一种，其中，0.35≤a<1.0，0≤b≤0.35，0≤1-a-b≤0.35。
三元材料的结构通式为LiNiaCobN(1-a-b)O2，式中，N可选地包括Mn、Zr、Al、B、Ta、Mo、W、Nb、Sb、La中的至少一种，其中，0.35≤a<1.0，0≤b≤0.35，0≤1-a-b≤0.35。根据镍含量的不同，三元材料可以分为低镍三元材料、中镍三元材料、高镍三元材料，以及根据是否含钴元素，三元材料还可以分为无钴三元材料，其中钴元素可由其他金属元素替代，本申请中，三元材料的具体类型不作限定。
可选地，在所述第一活性层包括三元材料时，所述第一活性层和所述第二活性层中的三元材料相同。
理论上，第一活性层和第二活性层中的三元材料可以相同也可以不同，但是最好是相同，相同的优势是两活性层的嵌锂量接近，膨胀程度一样，有利于极片的稳定。
可选地，所述三元材料包括5系单晶三元材料、5系多晶三元材料、6系单晶三元材料、6系多晶三元材料、7系单晶三元材料、7系多晶三元材料、8系单晶三元材料、8系多晶三元材料、9系单晶三元材料、9系多晶三元材料、或无钴三元材料中的至少一种。
本申请中的三元材料具体不做限定，可以是5系单晶三元材料、5系多晶三元材料、6系单晶三元材料、6系多晶三元材料、7系单晶三元材料、7系多晶三元材料、8系单晶三元材料、8系多晶三元材料、9系单晶三元材料、9系多晶三元材料、或无钴三元材料中的至少一种。
可选地，所述第一活性层包括第一活性物质、导电剂和粘结剂，所述第一活性物质包括包覆有导电包覆材料的磷酸锰铁锂材料，所述包覆有导电包覆材料的磷酸锰铁锂材料质量占所述第一活性层总质量的94％-97％；
和/或，所述第二活性层包括第二活性物质、导电剂和粘结剂，所述第二活性物质包括三元材料，所述三元材料占所述第二活性层总质量的95％-98％。
第一活性层包括第一活性物质、导电剂和粘结剂，第一活性物质包括包覆有导电包覆材料的磷酸锰铁锂材料，包覆有导电包覆材料的磷酸锰铁锂材料质量占第一活性层总质量的94％-97％，包覆有导电包覆材料的磷酸锰铁锂材料在该范围内(例如可以是94％、95％、96％、97％，以及上述任意两个点值之间的范围值)，可以制备性能优异的活性层，其中，粘结剂含量可以为1.8％、2％、2.5％、3％等，导电剂含量可以是1.8％、2％、2.5％等。
第二活性层包括第二活性物质、导电剂和粘结剂，第二活性物质包括三元材料，三元材料占第二活性层总质量的95％-98％，三元材料在该范围内(95％、96％、97％、98％，以及上述任意两个点值之间的范围值)，可以制备性能优异的活性层，其中，粘结剂含量可以为1.5％、2％、2.5％等，导电剂含量可以是1.8％、2％、2.5％等。
本申请还提供一种复合电极的制备方法，包括以下步骤：
在集流体上涂覆第一活性物质层浆料和第二活性物质层浆料，烘干后，经过冷压，得到复合电极；
其中，所述第一活性物质层浆料和所述第二活性物质层浆料分别形成为第一活性层和第二活性层，所述第一活性层设置在所述集流体上，所述第二活性层设置在所述第一活性层背离所述集流体的一侧，所述第一活性层包括磷酸锰铁锂材料，所述磷酸锰铁锂材料的至少部分表面设有导电包覆材料，所述导电包覆材料的质量为所述磷酸锰铁锂材料质量的1.0％-10.0％。
通过将第一活性物质层浆料和第二活性物质层浆料涂覆在集流体上形成多层的复合结构，在烘干后，经过冷压，可以得到复合电极。并且，第一活性物质层浆料和第二活性物质层浆料分别形成为第一活性层和第二活性层，第一活性层设置在集流体上，第二活性层设置在第一活性层背离集流体的一侧，第一活性层包括磷酸锰铁锂材料，磷酸锰铁锂材料的至少部分表面设有导电包覆材料。通过设计的复合电极，复合电极包括多层活性层，磷酸锰铁锂材料的至少部分表面设置有导电包覆材料，通过导电包覆材料提高磷酸锰铁锂材料的导电性，将含有磷酸锰铁锂材料的活性层设置在内层，另外的活性层设置在外层，如此，避免直接将含有磷酸锰铁锂材料的活性层大面积暴露在外，降低设有导电包覆材料的磷酸锰铁锂材料，在高导电情况下的在高电位下催化电解液分解的问题。
可选地，在所述在集流体上涂覆第一活性物质层浆料和第二活性物质层浆料，烘干后，经过冷压，得到复合电极的步骤中，包括以下步骤：
在集流体上涂覆第一活性物质层浆料，烘干后，再在第一活性物质层上涂覆第二活性物质层浆料，烘干后，经过冷压，得到复合电极。
复合电极通过以下方法制得，准备集流体，在集流体上涂覆第一活性物质层浆料，通过烘干机构，烘干第一活性物质层浆料后，第一活性物质层浆料变成第一活性层，再在第一活性层上涂覆第二活性物质层浆料，烘干第二活性物质层浆料后，在集流体上得到两层活性层，通过冷压机构，对极片进行冷压，将该集流体经过冷压，使集流体上的活性层被压实，得到一定厚度的复合电极。
可选地，在所述在集流体上涂覆第一活性物质层浆料和第二活性物质层浆料，烘干后，经过冷压，得到复合电极的步骤中，包括以下步骤：
在集流体上同时涂覆第一活性物质层浆料与第二活性物质层浆料，同时进行烘干，烘干后，经过冷压，得到复合电极。
同时在集流体上涂覆第一活性物质层浆料和第二活性物质层浆料可以提高涂布效率，降低烘干的能耗，也即将两次烘干简化为一次烘干，并且，同时涂布不会在两层之间形成界面，两层活性层的相容性好，结构更稳定。
可选地，所述在集流体上涂覆第一活性物质层浆料和第二活性物质层浆料的过程中，还包括以下步骤：
在集流体上先涂覆一层底涂，再在所述底涂上涂覆第一活性物质层浆料和第二活性物质层浆料。
先在集流体上涂布一层高粘的涂层，再涂布第一活性物质层浆料和第二活性物质层浆料，用于增强活性材料与基材之间的粘结力。
可选地，在烘干后，经过冷压，得到复合电极的步骤中，所述烘干的温度为90℃-120℃，所述冷压的压力为20吨-40吨，所述冷压的温度为15℃-35℃。
为了有效去除浆料中的溶剂，采用烘干的温度为90℃-120℃，例如，可以是90℃、100℃、110℃、120℃。为了将活性层压实至合适密度，冷压的压力为20吨-40吨，例如可以是20吨、25吨、30吨、35吨、40吨，以及上述任意两个点值之间的范围值，同时，在常温下进行冷压，简化操作。
本申请还提供一种电池，包括：负极极片、正极极片、隔离膜及电解液，其中所述正极极片为所述的复合电极。
由于上述的复合电极具有高稳定、高能量密度和低成本的电芯的优势，采用该复合电极制备的电池性价比更好。
本申请还提供一种用电设备，所述用电设备包括所述的电池。
用电设备采用上述高性价比的电池，提高用电设备的使用性能，提高使用价值。
本申请的复合电极，包括集流体、第一活性层和第二活性层，第一活性层设置在集流体上，第二活性层设置在第一活性层背离集流体的一侧，第一活性层包括磷酸锰铁锂材料，其中，磷酸锰铁锂材料的至少部分表面设有导电包覆材料，通过导电包覆材料包覆在磷酸锰铁锂材料的至少部分表面来提高磷酸锰铁锂材料的导电性，同时，采用在第一活性层背离集流体的一侧设置第二活性层，降低第一活性层中的包覆有导电包覆材料的磷酸锰铁锂材料与电解液直接接触的风险，降低高电位下催化电解液分解的风险，减少产气反应与电芯鼓胀的问题，在提高复合电极导电性的同时，还降低容量衰减和提高稳定性。导电包覆材料的量越多，导电性越好，电池的倍率性能就会越好。但是导电包覆材料含量进一步提高，实际的活性材料含量就会降低，电极的能量密度也会损失。因此，导电包覆材料的质量为磷酸锰铁锂材料质量的1.0％-10.0％，例如可以是1.0％、2.0％、3.0％、4.0％、5.0％、6.0％、7.0％、8.0％、9.0％、10.0％，以及上述任意两个点值之间的范围值。同时，由于第二活性层遮盖磷酸锰铁锂材料层，可以直接阻隔磷酸锰铁锂材料的至少部分表面的导电包覆材料，降低导电包覆材料在高电位下催化电解液分解的问题，此时可增大导电包覆材料的用量，提高磷酸锰铁锂材料层的导电性。
附图说明
为了更清楚地说明本申请实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图示出的结构获得其他的附图。
图1为本申请复合电极的制备方法一实施例的流程示意图；
图2为本申请复合电极的制备方法另一实施例的流程示意图；
图3为本申请复合电极的制备方法再一实施例的流程示意图；
图4为本申请复合电极的制备方法又一实施例的流程示意图；
图5为本申请复合电极第一活性层与第二活性层的结构示意图；
图6为本申请复合电极一实施例的结构示意图；
图7为本申请复合电极另一实施例的结构示意图；
图8为本申请复合电极再一实施例的结构示意图；
图9为本申请复合电极又一实施例的结构示意图。
附图标号说明：
本申请目的的实现、功能特点及优点将结合实施例，参照附图做进一步说明。
具体实施方式
下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本申请的一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
需要说明，本申请实施例中所有方向性指示(诸如上、下、左、右、前、后……)仅用于解释在某一特定姿态(如附图所示)下各部件之间的相对位置关系、运动情况等，如果该特定姿态发生改变时，则该方向性指示也相应地随之改变。
在本申请中，除非另有明确的规定和限定，术语“连接”、“固定”等应做广义理解，例如，“固定”可以是固定连接，也可以是可拆卸连接，或成一体；可以是机械连接，也可以是电连接；可以是直接相连，也可以通过中间媒介间接相连，可以是两个元件内部的连通或两个元件的相互作用关系，除非另有明确的限定。对于本领域的普通技术人员而言，可以根据具体情况理解上述术语在本申请中的具体含义。
另外，在本申请中如涉及“第一”、“第二”等的描述仅用于描述目的，而不能理解为指示或暗示其相对重要性或者隐含指明所指示的技术特征的数量。由此，限定有“第一”、“第二”的特征可以明示或者隐含地包括至少一个该特征。另外，全文中出现的“和/或”的含义为，包括三个并列的方案，以“A和/或B为例”，包括A方案，或B方案，或A和B同时满足的方案。另外，各个实施例之间的技术方案可以相互结合，但是必须是以本领域普通技术人员能够实现为基础，当技术方案的结合出现相互矛盾或无法实现时应当认为这种技术方案的结合不存在，也不在本申请要求的保护范围之内。
本领域中所提到的电池按是否可充电可以分为一次性电池和可充电电池。目前常见的可充电电池的类型有：铅酸电池、镍氢电池和锂离子电池。锂离子电池目前广泛应用于纯电动车及混合动力车，用于这种用途的锂离子电池的容量相对略低，但有较大的输出、充电电流，也有较长的使用寿命，但成本较高。
本申请实施例中所描述的电池是指可充电电池。下文中将主要以锂离子电池为例来描述本申请公开的实施例。应当理解的是，本申请公开的实施例对于其他任意适当类型的可充电电池都是适用的。本申请中公开的实施例所提到的电池可以直接或者间接应用于适当的装置中来为该装置供电。
本申请公开的实施例中所提到的电池是指包括一个或多个电池单体以提供预定的电压和容量的单一的物理模块。电池单体是电池中的基本单元，一般按封装的方式可以分为：柱形电池单体、长方体电池单体和软包电池单体。下文中将主要围绕长方体电池单体来展开。应当理解的是，下文中所描述的实施例在某些方面对于柱形电池单体或软包电池单体而言也是适用的。
电池单体包括正极极片、负极极片、电解液和隔离膜。锂离子电池单体主要依靠锂离子在正极极片和负极极片之间的移动来工作。柱形电池单体中三层材料的薄膜结构被卷绕成柱形形状的电极组件，而在长方体电池单体中薄膜结构被卷绕或者叠置成具有大致长方体形状的电极组件。
在通常的电池单体结构中，电池单体包括外壳、电极组件和电解液。电极组件被容纳在电池单体的外壳中，电极组件包括正极极片、负极极片和隔离膜。外壳包括外壳和端盖。外壳包括由多个壁形成的容纳腔以及开口。端盖布置在开口处以封闭容纳腔。除了电极组件之外，容纳腔中还容纳有电解液。电极组件中的正极极片和负极极片包括极耳。为了保证通过大电流而不发生熔断，正极极耳的数量为多个且层叠在一起，负极极耳的数量为多个且层叠在一起。极耳通过连接构件与位于电池单体外部的电极端子电连接，电极端子一般包括正电极端子和负电极端子。对长方体电池单体而言，电极端子一般设置在端盖部分。多个电池单体经由电极端子而被串联和/或并联在一起以应用于各种应用场合。
在一些诸如电动车辆等的大功率应用场合，电池的应用包括三个层次：电池单体、电池模块和电池。电池模块是为了从外部冲击、热、振动等中保护电池单体，将一定数目的电池单体电连接在一起并放入一个框架中而形成的。电池则指的是装入电动车辆的电池系统的最终状态。电池一般包括用于封装一个或多个电池单体的箱体。箱体一般由盖体和箱壳组成。
箱体的边框上或箱壳中部设置有多个用于与车辆主体连接的挂载点，为提高车辆主体与电池连接的稳定性，多在挂载点设置挂载部。
在一些电池生产加工技术中，首先将多个电池单体先整合为电池模块，然后将电池模块封装于电池的箱体中，形成电池包/电池箱。
常用的电池模块一般包括两块端板，两块端板之间排布有多个电池单体。设置有电池模块输出极的端板又称输出极端板，未设置电池模块输出极的端板又称非输出极端板。
电池包内可封装一排多个电池模块，也可封装多排多个电池模块，多排多个电池模块的排列方式可以是双排多列、多排双列、多排多列等。以封装双排多列电池模块的电池包为例，每一列第一个端板一般为头部输出极端板，两排电池模块间相邻的两块端板为中部非输出极端板，每一列最后一个端板为尾部非输出极端板，头部输出极端板和其中一个中部非输出极端板属于第一排电池模块，其中一个中部非输出极端板和尾部输出极端板属于第二排电池模块。
电池模块封装入电池的箱体需要依托工装才可实现，工装上一般设置有夹持电池模块的夹持机构，如夹爪、吸盘等。当采用设置夹爪的工装封装电池模块时，一般会在端板背离电池单体一侧设置与夹爪适配的夹爪槽，以供夹爪插入实现对电池模块的夹持与转运。
电池技术的发展要同时考虑多方面的设计因素，例如，能量密度、循环寿命、放电容量、充放电倍率等性能参数，另外，还需要考虑电池的生产成本以及加工工艺，以提高电池的质量以及生产效率。
磷酸锰铁锂材料不仅能量密度相比于磷酸铁锂能大幅提高，安全性却没有恶化，几乎与磷酸铁锂相当，相比于三元材料改善了很多。尽管磷酸锰铁锂材料优点很多，但却一直没有得到大规模商用，主要存在如下技术问题：磷酸锰铁锂材料导电性不好，只依靠传统配方中添加的少量导电碳难以满足要求，需要在每个颗粒外面包覆一层致密的多孔碳，增强颗粒之间的电子传导。可以理解的是，碳含量越高，导电性越好，电池的倍率性能就会越好。但是在电池满充的时候碳含量太高又会导致高电位下催化电解液分解，加大产气，导致电芯鼓胀，不仅容量衰减还加大产气与电芯鼓胀。例如，可以理解的是，作为导电包覆材料的多孔碳中含有缺陷和含氧官能团，这些缺陷和含氧官能团能催化电解液分解，此外，还可能存在的情形是，其他种类的导电包覆材料也可能会存在催化电解液分解的杂质，例如，金属氧化物中的活性成分杂质也催化电解液分解。
为此，本申请中一方面为了提高磷酸锰铁锂材料的导电性，同时又减轻包覆有导电材料的磷酸锰铁锂材料在高导电情况下，在高电位下催化电解液分解的风险，本申请通过设计复合电极，复合电极包括多层活性层，磷酸锰铁锂材料的至少部分表面设置有导电包覆材料，通过导电包覆材料提高磷酸锰铁锂材料的导电性，将含有磷酸锰铁锂材料的活性层设置在内层，另外的活性层设置在外层，如此，避免直接将含有磷酸锰铁锂材料的活性层大面积暴露在外，降低设有导电包覆材料的磷酸锰铁锂材料，在高导电情况下的在高电位下催化电解液分解的问题。
本申请的一种复合电极，复合电极包括集流体、第一活性层和第二活性层，第一活性层设置在集流体上，第二活性层设置在第一活性层背离集流体的一侧，第一活性层包括磷酸锰铁锂材料，其中，磷酸锰铁锂材料的至少部分表面设有导电包覆材料，导电包覆材料的质量为磷酸锰铁锂材料质量的1.0％-10.0％。
集流体，顾名思义就是指汇集电流的结构或零件，在锂离子电池上主要指的是金属箔，如铜箔、铝箔。泛指也可以包括极耳。其功用主要是将电池活性物质产生的电流汇集起来以便形成较大的电流对外输出。
活性层，是指包括有活性材料的层状结构，其中的活性材料是指正极涉及的正极活性物质，正极活性物质可以使用能可逆地嵌入与脱嵌Li+的化合物。
包覆，包覆是指在材料表面包覆导电物质，以提高导电性。
导电包覆材料，是指包覆在磷酸锰铁锂表面的导电材料，例如磷酸锰铁锂颗粒表面包覆碳材料、导电聚合物等。
如图5至图9所示，本申请的复合电极，通过导电包覆材料包覆在磷酸锰铁锂材料的至少部分表面来提高磷酸锰铁锂材料的导电性，同时，采用在第一活性层2背离集流体1的一侧设置第二活性层3，降低第一活性层中的包覆有导电包覆材料的磷酸锰铁锂材料与电解液直接接触的风险，降低高电位下催化电解液分解的风险，减少产气反应和电芯鼓胀的问题，在提高复合电极导电性的同时，还降低容量衰减和提高稳定性。导电包覆材料的量越多，导电性越好，电池的倍率性能就会越好。但是导电包覆材料含量进一步提高，实际的活性材料含量就会降低，电极的能量密度也会损失。因此，导电包覆材料的质量为磷酸锰铁锂材料质量的1.0％-10.0％，例如可以是1.0％、2.0％、3.0％、4.0％、5.0％、6.0％、7.0％、8.0％、9.0％、10.0％，以及上述任意两个点值之间的范围值。同时，由于第二活性层遮盖磷酸锰铁锂材料层，可以直接阻隔磷酸锰铁锂材料的至少部分表面的导电包覆材料与电解液接触，降低导电包覆材料在高电位下催化电解液分解的风险，此时可增大导电包覆材料的用量，提高磷酸锰铁锂材料层的导电性。
可以理解的是，第二活性层主要的功能之一是遮盖磷酸锰铁锂材料层，第二活性层的成分具体不做 限定。
进一步地，磷酸锰铁锂材料的至少部分表面导电包覆材料的质量为磷酸锰铁锂材料的至少部分表面磷酸锰铁锂材料质量的1％-5％。
导电包覆材料的量越多，导电性越好，电池的倍率性能就会越好。但是导电包覆材料含量进一步提高，实际的活性材料含量就会降低，电极的能量密度也会损失。因此，导电包覆材料的质量为磷酸锰铁锂材料质量的1.0％-5％，例如可以是1.0％、2.0％、3.0％、4.0％、5.0％，以及上述任意两个点值之间的范围值。
进一步地，磷酸锰铁锂材料的至少部分表面导电包覆材料的质量为磷酸锰铁锂材料的至少部分表面磷酸锰铁锂材料质量的1.3％-2.5％。
导电包覆材料的质量为磷酸锰铁锂材料的至少部分表面磷酸锰铁锂材料质量的1.3％-2.5％时，电池的性能较佳，因此，导电包覆材料的质量为磷酸锰铁锂材料质量的1.3％-2.5％，例如可以是1.3％、1.5％、1.8％、2.0％、2.3％、2.5％，以及上述任意两个点值之间的范围值。
进一步地，导电包覆材料为碳材料。
导电包覆材料为碳材料，作为包覆材料的多孔碳中含有缺陷和含氧官能团，这些缺陷和含氧官能团能催化电解液分解，磷酸锰铁锂材料的至少部分表面设置有碳材料，通过碳材料提高磷酸锰铁锂材料的导电性，将含有磷酸锰铁锂材料的活性层设置在内层，另外的活性层设置在外层，如此，避免直接将含有磷酸锰铁锂材料的活性层大面积暴露在外，降低设有碳材料的磷酸锰铁锂材料，在高导电情况下的在高电位下催化电解液分解的问题。通过层状活性层的设置，可以提高磷酸锰铁锂材料的至少部分表面的碳材料的包覆量，提高磷酸锰铁锂材料的导电性，以解决传统配方中添加的少量导电碳难以满足导电性的要求。
进一步地，复合电极还包括第三活性层，第三活性层设于集流体与第一活性层之间；和/或，复合电极还包括第四活性层，第四活性层设于第一活性层与第二活性层之间。
如图8和图9所示，本申请中，在满足第二活性层遮盖第一活性层的基础上，复合电极还包括第三活性层4，第三活性层设于集流体1与第一活性层2之间，此时，也能实现上述的效果，其中，第三活性层的材料不做限定。
还可以理解的是，复合电极还包括第四活性层5，第四活性层设于第一活性层2与第二活性层3之间，此时，也能实现上述的效果，其中，第四活性层5的材料不做限定。例如，第一活性层为具有导电包覆材料的磷酸锰铁锂层，第二活性层为高镍三元材料层，第四活性层为中镍三元材料层，或者，第一活性层为具有导电包覆材料的高锰含量的磷酸锰铁锂层，第二活性层为三元材料层，第四活性层为具有导电包覆材料的低锰含量的磷酸锰铁锂层。
还可以理解的是，如图9所示，第一活性层2与第二活性层3作为一个重复单元，多个重复单元设置在集流体1上，此时，也能实现上述的效果。也即，只要满足第一活性层2设置在复合电极多层结构的内层，使得减少第一活性层中的磷酸锰铁锂材料与电解液的直接接触即可。
还可以理解的是，第二活性层可以是完全遮盖第一活性层2，也可以是部分遮盖第一活性层2，具体不做限定。
进一步地，第二活性层设置在第一活性层的侧周面。
可以理解的是，第一活性层2被遮盖的面积越多，第一活性层中的磷酸锰铁锂材料与电解液的直接接触面积会越少，为了进一步减少第一活性层中的磷酸锰铁锂材料与电解液的直接接触，第二活性层覆盖第一活性层，也即，第二活性层将第一活性层暴露在外的结构都遮盖住，例如，第二活性层不仅可以遮盖第一活性层的表面，还可以遮盖第一活性层的侧周面。
进一步地，第一活性层还包括三元材料，磷酸锰铁锂材料的质量占第一活性层总质量的20％-80％。
三元材料，三元正极材料是层状镍钴锰(铝)酸锂复合材料，镍、钴、锰为过渡金属元素，所形成的固溶体可以任意比例混合，镍元素比例上升可以提升电池比能量，锰元素比例上升可以保证结构稳定性，钴元素比例上升可以稳定材料层状结构，有利于电池的循环性能和倍率性能。此外，还可以理解的是，三元材料还可以包括不含钴的材料，例如，采用其他金属元素代替钴得到的三元材料，如可采用Mo，Nb等代替钴得到的三元材料。
磷酸锰铁锂目前的压实密度相比于磷酸铁锂LFP偏低，虽然材料层面可以提高一些能量密度，但是在极片层级，由于磷酸锰铁锂的压实密度低，导致在单位面积基材上涂布的活性材料更少，最终整体的能量密度相比于LFP体系优势不明显。
为此，为了提高复合电极的能量密度，第一活性层还包括三元材料，且磷酸锰铁锂材料的质量占第一活性层总质量的20％-80％，例如，磷酸锰铁锂材料的质量可以占第一活性层总质量的20％、30％、40％、50％、60％、70％、80％，以及上述任意两个点值之间的范围值。其中，磷酸锰铁锂材料的质量 不能过低和过高，磷酸锰铁锂材料的质量过低会导致三元材料质量过高，电池的稳定性降低，磷酸锰铁锂材料的质量过高会导致三元材料质量过低，能量密度不足。
也即，由于磷酸锰铁锂的压实密度较低，三元材料的克容量和压实密度普遍较高，通过调控第一活性层中磷酸锰铁锂和三元材料量可以调控复合电极的能量密度，实现高稳定、高能量密度的、低成本的电芯。
进一步地，磷酸锰铁锂材料的平均粒径Dv50的范围值为0.2um-1um。
磷酸锰铁锂材料的离子传导能力很差，颗粒太大，锂离子传输路径长，动力学性能差，若颗粒尺寸做的很小，动力学性能好，但是加工性差，很难在集流体上进行涂布，因此磷酸锰铁锂材料的平均粒径Dv50可以为0.2um、0.3um、0.4um、0.5um、0.6um、0.7um、0.8um、0.9um、1um，以及上述任意两个点值之间的范围值。
进一步地，磷酸锰铁锂材料的结构通式为LiMnxFeyM1-x-yPO4，式中，0.2≤x≤0.8；0.1≤y≤0.5；0≤1-x-y≤0.2，M表示掺杂元素，可选地包括Al、Cu、Mg、Zn、Ni、Ti、V、Zr、Co、Ga、Sn、Sb、Nb和Ge中的至少一种。
磷酸锰铁锂材料的结构通式为LiMnxFeyM1-x-yPO4，式中，0.2≤x≤0.8；0.1≤y≤0.5；0≤1-x-y≤0.2，M表示掺杂元素，可选地包括Al、Cu、Mg、Zn、Ni、Ti、V、Zr、Co、Ga、Sn、Sb、Nb和Ge中的至少一种。磷酸锰铁锂材料中锰的摩尔占比为20％-80％，性能比较好，例如，磷酸锰铁锂材料中锰的摩尔占比可以是20％、30％、40％、50％、60％、70％、80％，以及上述任意两个点值之间的范围值。
进一步地，第一活性层的厚度占活性层总厚度的20％-80％。
第一活性层包括磷酸锰铁锂材料，第一活性层的厚度占活性层总厚度的20％-80％，例如可以是20％、30％、40％、50％、60％、70％、80％，以及上述任意两个点值之间的范围值。磷酸锰铁锂材料的厚度不能过低和过高，例如，当其他活性层包括三元材料时，磷酸锰铁锂材料的厚度过低会导致三元材料厚度过高，电池的稳定性降低，磷酸锰铁锂材料的厚度过高会导致三元材料厚度过低，能量密度不足。
进一步地，第二活性层的压实密度大于第一活性层的压实密度。
压实密度＝面密度/(极片碾压后的厚度-集流体厚度)，单位：g/cm3。
活性层的压实密度是按照极片中所有材料辊压后的质量来算的，活性层中除了活性材料，还包括导电碳和粘结剂等。
随着压实密度的上升，活性层的体积密度会上升，孔隙率会下降，比表面积上升，接触电阻下降，电极电解液界面膜SEI阻抗会降低，电荷交换阻抗下降。较低的压实密度反而会造成放电比容量低的问题，这主要是较高的孔隙率造成部分颗粒形成绝缘状态，无法参与充放电，而高压实密度的电极有更高的断裂强度，从而降低在循环过程中电极颗粒脱落，形成绝缘状态颗粒的风险。高的压实密度可以明显使电极的孔径和孔隙的分布更加均匀，导电剂和粘结剂分布更加均匀，降低电极的接触电阻和电荷交换阻抗，增大能够参与反应的活性面积，从而显著的提高材料的电化学性能。因此，活性层需要有合适的压实密度，以提高活性层的性能。基于第一活性层包括磷酸锰铁锂材料，第二活性层包括三元材料，基于磷酸锰铁锂材料和三元材料本身的结构特性，第二活性层的压实密度大于第一活性层的压实密度。
进一步地，第二活性层的压实密度为3.0g/cm3-4.5g/cm3，第一活性层的压实密度为2.2g/cm3-3.0g/cm3。
第一活性层包括磷酸锰铁锂材料，基于磷酸锰铁锂材料本身的结构特性，第一活性层的压实密度范围为2.2g/cm3-3.0g/cm3，第一活性层的压实密度在该范围内具有较好的应用价值。第二活性层包括三元材料，基于三元材料本身的结构特性，第二活性层的压实密度范围为3.0g/cm3-4.5g/cm3，第二活性层的压实密度在该范围内具有较好的应用价值。
进一步地，第二活性层包括三元材料或钴酸锂中的至少一种。
钴酸锂是一种无机化合物，化学式为LiCoO2，一般使用作锂离子电池的正电极材料。
由于磷酸锰铁锂的压实密度低，导致在单位面积基材上涂布的活性材料更少，最终整体的能量密度相比于LFP体系优势不明显；而三元材料的克容量和压实密度普遍较高，通过调控第一活性层与第二活性层的材料来调控复合电极的能量密度，实现高稳定、高能量密度的、低成本的电芯。
为此，第二活性层包括三元材料或钴酸锂中的至少一种，例如，第二活性层可以包括三元材料或钴酸锂，第二活性层还可以包括三元材料与钴酸锂的混合，具体不做限定。当然，除了三元材料与钴酸锂之外，第二活性层还可以包括其他的用于正极的材料。
相比于纯的磷酸锰铁锂电极而言，这种设计可以提高电芯的能量密度并实现能量密度可定制；另外，相比于纯的三元材料，磷酸锰铁锂含量提高可以实现降低三元材料的起火的风险。同时由于三元材料成本较高，采用本申请的复合电极还可以降低成本，提高性价比。
磷酸锰铁锂材料在高SOC(State Of Charge，荷电状态)下脱锂困难，也就是说这种材料做成的电 芯在接近电量充满的时候充电很困难，电池的极化严重，正极材料里面的锂离子难以脱出，嵌入到负极，因此会耗费大量时间充满电。
通过在磷酸锰铁锂电极层表面涂布一层三元材料，充电过程中，表层三元材料的脱锂程度比下层磷酸锰铁锂高，缓解磷酸锰铁锂高SOC脱锂困难的问题，降低电极的极化。
可以理解的是，在集流体上先涂布由导电包覆材料包覆的磷酸锰铁锂活性物质层，然后再涂布一层三元材料层，相当于物理隔离层，减少电解液与导电包覆材料直接接触，降低产气。这种结构可以适当提高磷酸锰铁锂的导电包覆材料的含量，以达到导电性能和稳定综合优势。
进一步地，第二活性层中包括的三元材料或钴酸锂的平均粒径Dv50的范围值为0.5um-20um。
可以理解的是，颗粒太大锂离子传输路径长，动力学性能差，若颗粒尺寸做的很小，动力学性能好，但是加工性差，很难在集流体上进行涂布。因此，第二活性层中包括的三元材料或钴酸锂的平均粒径Dv50可以为0.5um、1um、2um、3um、4um、5um、6um、7um、8um、9um、10um、11um、12um、13um、14um、15um、16um、17um、18um、19um、20um，以及上述任意两个点值之间的范围值。
进一步地，当第二活性层包括三元材料时，三元材料的结构通式为LiNiaCobN(1-a-b)O2，式中，N可选地包括Mn、Zr、Al、B、Ta、Mo、W、Nb、Sb、La中的至少一种，其中，0.35≤a<1.0，0≤b≤0.35，0≤1-a-b≤0.35。
三元材料的结构通式为LiNiaCobN(1-a-b)O2，式中，N可选地包括Mn、Zr、Al、B、Ta、Mo、W、Nb、Sb、La中的至少一种，其中，0.35≤a<1.0，0≤b≤0.35，0≤1-a-b≤0.35。根据镍含量的不同，三元材料可以分为低镍三元材料、中镍三元材料、高镍三元材料，以及根据是否含钴元素，三元材料还可以分为无钴三元材料，其中钴元素可由其他金属元素替代，本申请中，三元材料的具体类型不作限定。
进一步地，在第一活性层包括三元材料时，第一活性层和第二活性层中的三元材料相同。
理论上，第一活性层和第二活性层中的三元材料可以相同也可以不同，但是最好是相同，相同的优势是两活性层的嵌锂量接近，膨胀程度一样，有利于极片的稳定。
进一步地，三元材料包括5系单晶三元材料、5系多晶三元材料、6系单晶三元材料、6系多晶三元材料、7系单晶三元材料、7系多晶三元材料、8系单晶三元材料、8系多晶三元材料、9系单晶三元材料、9系多晶三元材料、或无钴三元材料中的至少一种。
5系三元材料，是指镍金属的摩尔比大于等于50％、小于60％的三元材料。6系三元材料，是指镍金属的摩尔比大于等于60％、小于70％的三元材料。7系三元材料，是指镍金属的摩尔比大于等于70％、小于80％的三元材料。8系三元材料，是指镍金属的摩尔比大于等于80％、小于90％的三元材料。9系三元材料，是指镍金属的摩尔比大于等于90％的三元材料，例如包括Ni90、Ni92、Ni95等。随着镍的含量逐步提高，电池能量密度也随之提升，镍越高，电芯能量密度越大，但钴被迫减少，电池的稳定风险也随之陡增。中镍三元材料因镍含量相对高镍较低，且钴含量也较高，本身稳定性就足够有保证。再加上单晶材料产热较少，稳定性高。单晶中镍三元目前在经济性、稳定性、能量密度、循环寿命等多个维度实现了较好的平衡。
无钴三元材料，是指不含有钴的三元材料，例如钴元素可以由其他元素替换构成的三元材料。
单晶三元材料和多晶三元材料是根据材料本身的形貌来命名的。从形貌上看，单晶为单个分散颗粒，而与之对应的多晶三元材料则是一次颗粒团聚的二次颗粒。
相对多晶材料，单晶材料更适合做高电压。同时，单晶材料内部没有晶界，可提升三元材料的循环稳定性，对延长电池的循环寿命在镍钴锰比例相同的情况下，单晶三元材料克容量稍低于多晶三元材料，但由于其电压更高，因此材料整体能量密度已经和目前高镍三元材料差不多。单晶三元材料的缺点则在于倍率性能表现不佳，且生产工艺更为复杂，材料价格相对较高。
也即，本申请中的三元材料具体不做限定，可以是5系单晶三元材料、5系多晶三元材料、6系单晶三元材料、6系多晶三元材料、7系单晶三元材料、7系多晶三元材料、8系单晶三元材料、8系多晶三元材料、9系单晶三元材料、9系多晶三元材料、或无钴三元材料中的至少一种。
进一步地，第一活性层包括第一活性物质、导电剂和粘结剂，第一活性物质包括包覆有导电包覆材料的磷酸锰铁锂材料，包覆有导电包覆材料的磷酸锰铁锂材料质量占第一活性层总质量的94％-97％；和/或，第二活性层包括第二活性物质、导电剂和粘结剂，第二活性物质包括三元材料，三元材料占第二活性层总质量的95％-98％。
第一活性层包括第一活性物质、导电剂和粘结剂，第一活性物质包括包覆有导电包覆材料的磷酸锰铁锂材料，包覆有导电包覆材料的磷酸锰铁锂材料质量占第一活性层总质量的94％-97％，包覆有导电包覆材料的磷酸锰铁锂材料在该范围内(例如可以是94％、95％、96％、97％，以及上述任意两个点值之间的范围值)，可以制备性能优异的活性层，其中，粘结剂含量可以为1.8％、2％、2.5％、3％等，导电剂含量可以是1.8％、2％、2.5％等。
第二活性层包括第二活性物质、导电剂和粘结剂，第二活性物质包括三元材料，三元材料占第二活性层总质量的95％-98％，三元材料在该范围内(95％、96％、97％、98％，以及上述任意两个点值之间的范围值)，可以制备性能优异的活性层，其中，粘结剂含量可以为1.5％、2％、2.5％等，导电剂含量可以是1.8％、2％、2.5％等。
导电剂过少导致导电效果变差，过多导致能量密度降低。粘结剂用量适中可以使得涂层不掉粉且耐热性较好，过少则粘结性不足，过多则导致浆料粘度超标。
进一步地，如图1所示，本申请还提供一种复合电极的制备方法，包括以下步骤：在集流体上涂覆第一活性物质层浆料和第二活性物质层浆料，烘干后，经过冷压，得到复合电极；其中，第一活性物质层浆料和第二活性物质层浆料分别形成为第一活性层和第二活性层，第一活性层设置在集流体上，第二活性层设置在第一活性层背离集流体的一侧，第一活性层包括磷酸锰铁锂材料，磷酸锰铁锂材料的至少部分表面设有导电包覆材料，导电包覆材料的质量为磷酸锰铁锂材料质量的1.0％-10.0％。
第一活性物质层浆料是指用来制备第一活性层的材料，第二活性物质层浆料是指用来制备第二活性层的材料。
烘干是指将浆料中的溶剂蒸发，去除溶剂的过程。使极片处于较低的溶剂含量，如果溶剂含量过多，锂电池在化成阶段会消耗过量的锂，造成锂的不可逆损失，导致容量降低，电池气胀等问题，影响电池性能。
冷压是指对电极极片进行压缩，正极涂布干燥完，需要在工艺时间内进行对辊。对辊即对极片进行压实，目前有热压和冷压两种工艺。热压压实相对冷压高，反弹率较低，可减少轧制力；但冷压工艺相对简单易操作控制。对辊主要设备到如下工艺值，压实密度、反弹率、延伸率。同时要注意极片表面无脆片、硬块、掉料、波浪边等现象且间隙处不允许断裂。极片轧制工艺可以降低极片在轧制过程中的延伸率和宽展率，降低极片涂层材料孔隙结构的破坏率；提高极片涂层的厚度一致性，以改善极片的横截面形状；提高极片轧制后电极材料的压实密度一致性；减少极片轧制后表面电极材料的反弹。极片轧制工艺还可以保证极片表面光滑和平整，防止涂层表面的毛刺刺穿隔膜引发短路；对极片涂层材料进行压实，降低极片的体积，以提高电池的能量密度；使活性物质、导电剂颗粒接触更加紧密，提高电子导电率；增强涂层材料与集流体的结合强度，减少电极片在循环过程中掉粉的情况发生，提高电池的循环寿命和稳定性能。
例如，可以利用两根棍轴来对极片做压缩活动，使轧辊与电池极片之间产生摩擦力；使电池极片拉进旋转的对辊之间，电池极片受压变形。电池极片的对辊是正负极片上电池材料压实的过程，可增加正极或负极材料的压实密度，合适的压实密度可增大电池的放电容量、减小内阻、减小极化损失、延长电池的循环寿命、提高锂离子电池的利用率。
通过将第一活性物质层浆料和第二活性物质层浆料涂覆在集流体上形成多层的复合结构，在烘干后，经过冷压，可以得到复合电极。并且，第一活性物质层浆料和第二活性物质层浆料分别形成为第一活性层和第二活性层，第一活性层设置在集流体上，第二活性层设置在第一活性层背离集流体的一侧，第一活性层包括磷酸锰铁锂材料，磷酸锰铁锂材料的至少部分表面设有导电包覆材料。通过设计的复合电极，复合电极包括多层活性层，磷酸锰铁锂材料的至少部分表面设置有导电包覆材料，通过导电包覆材料提高磷酸锰铁锂材料的导电性，将含有磷酸锰铁锂材料的活性层设置在内层，另外的活性层设置在外层，如此，避免直接将含有磷酸锰铁锂材料的活性层大面积暴露在外，降低设有导电包覆材料的磷酸锰铁锂材料，在高导电情况下的在高电位下催化电解液分解的问题。
进一步地，如图1和图3所示，在在集流体上涂覆第一活性物质层浆料和第二活性物质层浆料，烘干后，经过冷压，得到复合电极的步骤中，包括以下步骤：在集流体上涂覆第一活性物质层浆料，烘干后，再在第一活性物质层上涂覆第二活性物质层浆料，烘干后，经过冷压，得到复合电极。
如图3所示，复合电极通过以下方法制得，准备集流体，在集流体上涂覆第一活性物质层浆料，通过烘干机构，烘干第一活性物质层浆料后，第一活性物质层浆料变成第一活性层，再在第一活性层上涂覆第二活性物质层浆料，烘干第二活性物质层浆料后，在集流体上得到两层活性层，通过冷压机构，对极片进行冷压，将该集流体经过冷压，使集流体上的活性层被压实，得到一定厚度的复合电极。
进一步地，如图1和图4所示，在在集流体上涂覆第一活性物质层浆料和第二活性物质层浆料，烘干后，经过冷压，得到复合电极的步骤中，包括以下步骤：在集流体上同时涂覆第一活性物质层浆料与第二活性物质层浆料，同时进行烘干，烘干后，经过冷压，得到复合电极。
可以理解的是，同时涂布两层工艺可以实现，例如，利用涂布设备，定制相应的垫片，可以实现同时挤出两种浆料涂在集流体上；同时涂覆第一活性物质层浆料和第二活性物质层浆料可以提高涂布效率，降低烘干的能耗，也即将两次烘干简化为一次烘干，并且，同时涂布不会在两层之间形成界面，两层活性层的相容性好，结构更稳定。
进一步地，如图2所示，在所集流体上涂覆第一活性物质层浆料和第二活性物质层浆料的过程中，还包括以下步骤：在集流体上先涂覆一层底涂，再在底涂上涂覆第一活性物质层浆料和第二活性物质层浆料。
底涂是指高黏涂层，用于增强活性材料层与集流体之间的粘结力。
先在集流体上涂布一层高粘的涂层，再涂布第一活性物质层浆料和第二活性物质层浆料，用于增强活性材料与基材之间的粘结力。
进一步地，在烘干后，经过冷压，得到复合电极的步骤中，烘干的温度为90℃-120℃，冷压的压力为20吨-40吨，冷压的温度为15℃-35℃。
为了有效去除浆料中的溶剂，采用烘干的温度为90℃-120℃，例如，可以是90℃、100℃、110℃、120℃。为了将活性层压实至合适密度，冷压的压力为20吨-40吨，例如可以是20吨、25吨、30吨、35吨、40吨，以及上述任意两个点值之间的范围值，同时，在常温下进行冷压，简化操作。
进一步地，本申请还提供一种电池，包括：负极极片、正极极片、隔离膜及电解液，其中正极极片为上述的复合电极。由于复合电极采用了上述所有实施例的全部技术方案，因此至少具有上述实施例的技术方案所带来的所有有益效果，在此不再一一赘述。
由于上述的复合电极具有高稳定、高能量密度和低成本的电芯的优势，采用该复合电极制备的电池性价比更好。
进一步地，本申请还提供一种用电设备，用电设备包括上述的电池。由于电池采用了上述所有实施例的全部技术方案，因此至少具有上述实施例的技术方案所带来的所有有益效果，在此不再一一赘述。
用电设备采用上述高性价比的电池，提高用电设备的使用性能，提高使用价值。
实施例
实施例1
正极极片的制备
第一活性层制备：将正极活性物质碳包覆的磷酸锰铁锂(碳含量1％)、导电炭黑、粘结剂PVDF和溶剂N-甲基吡咯烷酮(NMP)按重量比95：2：3：100均匀搅拌，得到混合均匀的第一活性层浆料；将第一活性层浆料均匀的涂覆在厚15微米的铝箔集流体上，然后在110℃下烘干。
第二活性层制备：将正极活性物质五系单晶三元材料、导电炭黑、粘结剂PVDF和溶剂N-甲基吡咯烷酮(NMP)按重量比95：2：2：100均匀搅拌，得到混合均匀的第二活性层浆料；将第二活性层浆料均匀的涂覆在已烘干的第一活性层上，然后在110℃下烘干。经过压力20-40吨冷压处理后即可获得涂层厚度约为100um的复合电极。
其中，第一膜活性层的厚度与第二活性层的厚度比为5：5。
负极极片的制备
将人造石墨、导电炭黑、粘结剂羧甲基纤维素(CMC)和溶剂水按重量比95：2：3：100均匀混合，搅拌得到均匀的负极浆料；将负极浆料均匀的涂覆在厚6μm的铜箔集流体上，然后在100℃下烘干。经过压力20-40吨冷压处理后即可获得涂层厚度约为60μm的膜片。
电解液的制备
将碳酸亚乙酯(EC)、聚碳酸酯(PC)、碳酸二甲酯(DMC)按体积比1:1:1混合，然后将LiPF6均匀溶解在上述溶液中，得到电解液。该电解液中，LiPF6的浓度为1mol/L。
隔膜：以厚度为12μm的聚乙烯膜(PE)作为隔离膜。
二次电池的制备
将上述各实施例或对比例中的正极极片、隔离膜、负极极片按顺序堆叠并卷绕，得到电极组件；将电极组件放入外包装中，加入上述制备的电解液，经封装、静置、化成、老化等工序后，得到二次电池。
在实施例1的基础上，在其他条件不变的情况下，改变实验参数(如表1所示)，得到实施例2至实施例11、以及对比例1至对比例3的实验数据。
二次电池性能测试
电池循环寿命测试
分别取五个上述各实施例和对比例中二次电池进行平行试验，每个电池在常温下以0.33C倍率充电至电压等于4.2V，然后再以0.33C倍率放电至电压等于2.0V，测得可逆容量为C0。不断重复充电放电，直到某一次循环的放电容量Cn/C0≤80％为止。那么总的循环次数记为X-Cycle。
各实施例和对比例的二次电池性能测试结果如表1所示。
表1电池性能测试数据表

从表1中可以看出，比较实施例和对比例，实施例中包括第一活性层和第二活性层，其循环寿命要大于对比例。具体地，如实施例1至实施例6所示，磷酸锰铁锂材料的碳包覆量越多，电阻越低，但是能量密度会降低，为了兼顾导电性和能量密度，需要将碳包覆量设置在合适范围内。如实施例5、实施例7和实施例8所示，第一活性层的厚度越厚，电阻越大，能量密度会降低，因此，第一活性层的厚度需要设置在合适的范围内。如实施例9至实施例11所示，第一活性层中的三元材料含量越多，电阻越低，能量密度会升高，但是循环寿命会降低。
从对比例1至对比例3可以看出，当复合电极的活性层全部是第一活性层，或者全部是第二活性层，其循环寿命下降。
综上所述，采用复合电极的结构，能有效提高复合电极的综合性能。
上仅为本申请的优选实施例，并非因此限制本申请的专利范围，凡是在本申请的申请构思下，利用本申请说明书及附图内容所作的等效结构变换，或直接/间接运用在其他相关的技术领域均包括在本申请的专利保护范围内。

Claims (25)

  1. 一种复合电极，其中，所述复合电极包括集流体、第一活性层和第二活性层，所述第一活性层设置在所述集流体上，所述第二活性层设置在所述第一活性层背离所述集流体的一侧，所述第一活性层包括磷酸锰铁锂材料，其中，所述磷酸锰铁锂材料的至少部分表面设有导电包覆材料，所述导电包覆材料的质量为所述磷酸锰铁锂材料质量的1.0％-10.0％。
  2. 如权利要求1所述的复合电极，其中，所述导电包覆材料的质量为所述磷酸锰铁锂材料质量的1％-5％。
  3. 如权利要求2所述的复合电极，其中，所述导电包覆材料的质量为所述磷酸锰铁锂材料质量的1.3％-2.5％。
  4. 如权利要求1所述的复合电极，其中，所述导电包覆材料为碳材料。
  5. 如权利要求1至4中任一项所述的复合电极，其中，所述复合电极还包括第三活性层，所述第三活性层设于所述集流体与所述第一活性层之间；
    和/或，所述复合电极还包括第四活性层，所述第四活性层设于所述第一活性层与所述第二活性层之间。
  6. 如权利要求1至4中任一项所述的复合电极，其中，所述第二活性层设置在所述第一活性层的侧周面。
  7. 如权利要求1至6中任一项所述的复合电极，其中，所述第一活性层还包括三元材料，所述磷酸锰铁锂材料的质量占所述第一活性层总质量的20％-80％。
  8. 如权利要求1至7中任一项所述的复合电极，其中，所述磷酸锰铁锂材料的平均粒径Dv50的范围值为0.2um-1um。
  9. 如权利要求1至8中任一项所述的复合电极，其中，所述磷酸锰铁锂材料的结构通式为LiMnxFeyM1-x-yPO4，式中，0.2≤x≤0.8；0.1≤y≤0.5；0≤1-x-y≤0.2，M表示掺杂元素，可选地包括Al、Cu、Mg、Zn、Ni、Ti、V、Zr、Co、Ga、Sn、Sb、Nb和Ge中的至少一种。
  10. 如权利要求1至9中任一项所述的复合电极，其中，所述第一活性层的厚度占活性层总厚度的20％-80％。
  11. 如权利要求1至10中任一项所述的复合电极，其中，所述第二活性层的压实密度大于所述第一活性层的压实密度。
  12. 如权利要求11所述的复合电极，其中，所述第二活性层的压实密度为3.0g/cm3-4.5g/cm3，所述第一活性层的压实密度为2.2g/cm3-3.0g/cm3。
  13. 如权利要求1至12中任一项所述的复合电极，其中，所述第二活性层包括三元材料或钴酸锂中的至少一种。
  14. 如权利要求13所述的复合电极，其中，所述第二活性层中包括的三元材料或钴酸锂的平均粒径Dv50的范围值为0.5um-20um。
  15. 如权利要求13或14所述的复合电极，其中，当所述第二活性层包括三元材料时，所述三元材料的结构通式为LiNiaCobN(1-a-b)O2，式中，N可选地包括Mn、Zr、Al、B、Ta、Mo、W、Nb、Sb、La中的至少一种，其中，0.35≤a<1.0，0≤b≤0.35，0≤1-a-b≤0.35。
  16. 如权利要求13至15中任一项所述的复合电极，其中，在所述第一活性层包括三元材料时，所述第一活性层和所述第二活性层中的三元材料相同。
  17. 如权利要求15所述的复合电极，其中，所述三元材料包括5系单晶三元材料、5系多晶三元材料、6系单晶三元材料、6系多晶三元材料、7系单晶三元材料、7系多晶三元材料、8系单晶三元材料、8系多晶三元材料、9系单晶三元材料、9系多晶三元材料、或无钴三元材料中的至少一种。
  18. 如权利要求1至17中任一项所述的复合电极，其中，所述第一活性层包括第一活性物质、导电剂和粘结剂，所述第一活性物质包括包覆有导电包覆材料的磷酸锰铁锂材料，所述包覆有导电包覆材料的磷酸锰铁锂材料质量占所述第一活性层总质量的94％-97％；
    和/或，所述第二活性层包括第二活性物质、导电剂和粘结剂，所述第二活性物质包括三元材料，所述三元材料占所述第二活性层总质量的95％-98％。
  19. 一种复合电极的制备方法，其中，包括以下步骤：
    在集流体上涂覆第一活性物质层浆料和第二活性物质层浆料，烘干后，经过冷压，得到复合电极；
    其中，所述第一活性物质层浆料和所述第二活性物质层浆料分别形成为第一活性层和第二活性层，所述第一活性层设置在所述集流体上，所述第二活性层设置在所述第一活性层背离所述集流体的一侧，所述第一活性层包括磷酸锰铁锂材料，所述磷酸锰铁锂材料的至少部分表面设有导电包覆材料，所述导电包覆材料的质量为所述磷酸锰铁锂材料质量的1.0％-10.0％。
  20. 如权利要求19所述的复合电极的制备方法，其中，在所述在集流体上涂覆第一活性物质层浆料和第二活性物质层浆料，烘干后，经过冷压，得到复合电极的步骤中，包括以下步骤：
    在集流体上涂覆第一活性物质层浆料，烘干后，再在第一活性物质层上涂覆第二活性物质层浆料，烘干后，经过冷压，得到复合电极。
  21. 如权利要求19所述的复合电极的制备方法，其中，在所述在集流体上涂覆第一活性物质层浆料和第二活性物质层浆料，烘干后，经过冷压，得到复合电极的步骤中，包括以下步骤：
    在集流体上同时涂覆第一活性物质层浆料与第二活性物质层浆料，同时进行烘干，烘干后，经过冷压，得到复合电极。
  22. 如权利要求19至21中任一项所述的复合电极的制备方法，其中，所述在集流体上涂覆第一活性物质层浆料和第二活性物质层浆料的过程中，还包括以下步骤：
    在集流体上先涂覆一层底涂，再在所述底涂上涂覆第一活性物质层浆料和第二活性物质层浆料。
  23. 如权利要求19至22中任一项所述的复合电极的制备方法，其中，在烘干后，经过冷压，得到复合电极的步骤中，所述烘干的温度为90℃-120℃，所述冷压的压力为20吨-40吨，所述冷压的温度为15℃-35℃。
  24. 一种电池，其中，包括：负极极片、正极极片、隔离膜及电解液，其中所述正极极片为如权利要求1至18中任一项所述的复合电极。
  25. 一种用电设备，其中，所述用电设备包括如权利要求24所述的电池。
PCT/CN2023/114473 2022-11-03 2023-08-23 复合电极及其制备方法、电池和用电设备 Ceased WO2024093458A1 (zh)

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