WO2023165593A1 - 电极极片及其制备方法和锂电池 - Google Patents

电极极片及其制备方法和锂电池 Download PDF

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Publication number
WO2023165593A1
WO2023165593A1 PCT/CN2023/079503 CN2023079503W WO2023165593A1 WO 2023165593 A1 WO2023165593 A1 WO 2023165593A1 CN 2023079503 W CN2023079503 W CN 2023079503W WO 2023165593 A1 WO2023165593 A1 WO 2023165593A1
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Prior art keywords
active material
network matrix
electrode
pole piece
conductive network
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Ceased
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PCT/CN2023/079503
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English (en)
French (fr)
Inventor
葛立萍
郝嵘
庄明昊
苏碧哲
许占
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BYD Co Ltd
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BYD Co Ltd
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Priority to KR1020247030859A priority Critical patent/KR20240151211A/ko
Priority to CA3245372A priority patent/CA3245372A1/en
Priority to EP23762991.0A priority patent/EP4489094A4/en
Priority to JP2024552286A priority patent/JP2025508528A/ja
Publication of WO2023165593A1 publication Critical patent/WO2023165593A1/zh
Priority to US18/823,106 priority patent/US20240429400A1/en
Anticipated expiration legal-status Critical
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    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • 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
    • H—ELECTRICITY
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    • 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
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    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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    • 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
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    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
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    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
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    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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    • H01M4/386—Silicon or alloys based on silicon
    • 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 batteries, in particular to an electrode pole piece, a preparation method thereof, and a lithium battery.
  • the industry improves the energy density and power of lithium batteries by increasing the surface density, compaction density and mass ratio of electrode active materials.
  • the industry generally ensures the electronic conductivity of the electrode pads during battery charging and discharging by adding an excessive amount of conductive agent. Excessive conductive agent will inevitably lead to too small active material content in the electrode sheet, thereby inhibiting the energy density of the battery.
  • the distribution and morphology of the excess conductive agent in the electrode sheet are difficult to control.
  • the present application provides an electrode pole piece, a preparation method thereof, and a lithium battery.
  • the electrode pole piece has a three-dimensional conductive network matrix, and the actual volume of the three-dimensional conductive network matrix and the electrode active material are controlled to meet a specific relationship, which can optimize the conductive network in the electrode pole piece, thereby improving the performance of the gram capacity, and furthermore It is beneficial to exert the energy density of the battery and improve the capacity retention rate of the battery.
  • the first aspect of the present application provides an electrode pole piece, the electrode pole piece includes an electrode active material layer, and the electrode active material layer includes a three-dimensional conductive network matrix and an electrode active material loaded on the three-dimensional conductive network matrix and Binder, the three-dimensional conductive network matrix and the electrode active material satisfy the following relationship:
  • V is the actual volume of the three-dimensional conductive network matrix, in cm ;
  • m is the mass of the electrode active material, in g;
  • D is the D50 particle size of the electrode active material, in ⁇ m, ⁇ is the true density of the electrode active material, and the unit is g/cm 3 ;
  • d is the thickness of a single carbon atomic layer, and the value of d is 0.334nm.
  • the D is in the range of 0.1 ⁇ m-20 ⁇ m.
  • the V corresponding to every 100 g of the electrode active material is in the range of 0.01 cm 3 -20 cm 3 .
  • the true density of lithium cobaltate is 5.1g/cm 3 ; the true density of the ternary material is 4.8g/cm 3 ; the true density of lithium manganate is 4.2g/cm 3 ; the true density of lithium iron phosphate The density is 3.6g/cm 3 ; the true density of graphite is 2.26g/cm 3 .
  • the three-dimensional conductive network matrix is a current collector with a three-dimensional network structure.
  • the electrode sheet further includes a current collector, and the three-dimensional conductive network matrix is located on at least one side surface of the current collector.
  • the shape of the three-dimensional conductive network matrix includes a cage shape.
  • At least part of the material of the three-dimensional conductive network matrix includes at least one of conductive polymers, metal materials, and conductive carbon materials.
  • the electrode pole piece is a positive pole piece
  • the electrode active material includes a positive electrode active material
  • the positive electrode active material includes lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate , lithium cobalt oxide, lithium manganese oxide, nickel At least one of lithium manganate, lithium-nickel-cobalt-manganese-oxygen layered ternary material, lithium-nickel-cobalt-aluminum-oxygen layered ternary material, and lithium-nickel-manganese-cobalt-aluminum-oxygen quaternary material.
  • the general structural formula of the lithium nickel cobalt manganese oxide layered ternary material is Li 1+m Ni x Co y Mn 1-xy O 2 , where x ⁇ 0.33, 0 ⁇ y ⁇ 0.4, 0 ⁇ m ⁇ 0.1.
  • the general structural formula of the lithium-nickel-cobalt-aluminum-oxygen layered ternary material is Li 1+m Ni x Co y Al 1-xy O 2 , where x ⁇ 0.33, 0 ⁇ y ⁇ 0.4, 0 ⁇ m ⁇ 0.1.
  • the general structural formula of the lithium nickel manganese cobalt aluminum oxygen quaternary material is Li 1+m Ni x Co y Mn z Al 1-xyz O 2 , where x ⁇ 0.33, 0 ⁇ y ⁇ 0.4, 0 ⁇ z ⁇ 0.4, 0 ⁇ m ⁇ 0.1.
  • the electrode pole piece is a negative electrode pole piece
  • the electrode active material includes a negative electrode active material
  • the negative electrode active material includes at least one of graphite, natural graphite, mesocarbon microspheres, and silicon carbon negative electrode materials .
  • the second aspect of the present application provides a method for preparing an electrode sheet, including:
  • the electrode sheet precursor is rolled to obtain the electrode sheet provided in the first aspect of the present application.
  • forming the mixed material containing the electrode active material and the binder on the three-dimensional conductive network matrix includes:
  • the three-dimensional conductive network matrix is placed on the current collector, and then the mixed material containing the electrode active material and the binder is coated on the three-dimensional conductive network matrix.
  • said rolling the electrode pole piece precursor includes:
  • the electrode sheet precursor is placed on the current collector, and then the rolling is carried out.
  • the method for constructing the three-dimensional conductive network matrix includes three-dimensional printing, powder metallurgy, electrodeposition or etching current collectors.
  • the constructing the three-dimensional conductive network matrix further includes conduction treatment.
  • the conduction treatment includes:
  • the three-dimensional conductive network matrix is prepared by the three-dimensional printing or the electrodeposition;
  • the surface of the non-conductive three-dimensional network matrix is carbonized, or a conductive layer is formed on the non-conductive three-dimensional network matrix, The three-dimensional conductive matrix is obtained.
  • the forming method of forming the mixed material containing the electrode active material and the binder on the three-dimensional conductive network matrix includes coating, and the coating includes drop coating and brush coating , Spraying, dipping, scraping, spin coating.
  • the third aspect of the present application provides a lithium battery, the lithium battery has the electrode sheet provided in the first aspect of the present application.
  • Fig. 1A and Fig. 1B are schematic diagrams of the structure of the section of the electrode pole piece provided by the embodiment of the present application;
  • Fig. 2 is the structural representation of the three-dimensional conductive network matrix that embodiment 1 makes;
  • FIG. 3 is a schematic flowchart of a method for preparing an electrode sheet provided in an embodiment of the present application.
  • the embodiment of the present application provides an electrode pole piece, the electrode pole piece is a positive pole piece or a negative pole piece, and the electrode pole piece includes an electrode active material layer, and the electrode active material layer includes a three-dimensional conductive network matrix and is loaded on the three-dimensional conductive network matrix
  • the electrode active material and binder on the surface, the three-dimensional conductive network matrix and the electrode active material satisfy the following relationship:
  • a mathematical calculation model is first set for the actual volume of the three-dimensional conductive network matrix: starting from the function of the three-dimensional conductive network matrix, the matrix is a conductive network between electrode active materials, and all electrode active materials need to be connected in the together, and make it into shape. Therefore, the electrode active material is preset as spheres with diameters D, and many spheres are closely arranged with each other.
  • the material used to form the three-dimensional conductive network matrix is filled between the gaps between the closely arranged spheres, and the three-dimensional
  • the conductive network matrix material will form an interconnected three-dimensional conductive network (that is, the three-dimensional conductive network can be understood as a hollow sphere or hollow prisms of other shapes interlaced with each other). Or first form a preset three-dimensional network structure, and then fill the gaps of the three-dimensional network structure with electrode active materials (preset as spheres with diameters D). Therefore, the above mathematical calculation model can be regarded as a combination of a sphere with a diameter D and its circumscribed regular hexahedron as the smallest volume unit.
  • 6D2 represents the surface area of the circumscribed regular hexahedron (diameter is D) of a sphere with the particle size of the electrode active material D50 as the diameter
  • d ⁇ 6D2 represents the three-dimensional conductive network structure base used to form the above-mentioned circumscribed hollow regular hexahedron.
  • the minimum volume of the material that is, the minimum volume of the three-dimensional conductive network structure substrate used in the minimum volume unit).
  • D3 can represent the volume of a solid regular hexahedron whose edge length is D, Then it can represent the volume of the irregular object left after digging out a sphere with a diameter of D in a solid regular hexahedron with an edge length of D (that is, the maximum volume of the three-dimensional conductive network structure substrate used in the minimum volume unit).
  • the minimum unit volume V i of the three-dimensional conductive network matrix satisfies: Multiply the above relationship by the total number of electrode active material pellets The relationship between the actual volume of the entire three-dimensional conductive network matrix and the D50 particle size of the electrode active material can be obtained:
  • the amount of conductive agent can be reduced to the minimum, that is, the electrode sheet can be guaranteed to have a good conductive path so that the electrode sheet While the rate performance is better and the internal resistance is smaller, the proportion of the active material in the electrode sheet is maximized.
  • the accuracy of parameter control requirements in the preparation of the three-dimensional conductive network matrix can be reduced, and the production efficiency of the electrode sheet can be improved while the active material in the electrode sheet can be increased.
  • the proportion so as to improve the gram capacity, which is beneficial to the energy density of the battery, and improves the capacity retention rate of the battery.
  • the actual volume of the three-dimensional conductive network matrix satisfies the above relational formula, it can also be based on the used
  • the physical and chemical properties (such as particle size, compaction density, etc.) of the electrode active material are used to design the parameters such as the specific shape of the above-mentioned three-dimensional conductive network matrix, the size of the prism, and the connection mode of the prism to help realize the directional accumulation of the electrode active material particles ( That is, the packing manner and position of the active material particles are defined).
  • the performance of the battery can improve the capacity retention rate of the battery.
  • the actual volume of the above-mentioned three-dimensional conductive network matrix refers to the intrinsic volume of the three-dimensional conductive network matrix excluding its interstitial volume, and the actual volume of the three-dimensional conductive network matrix may be equal to the ratio of its mass to true density.
  • the D50 particle size of the above-mentioned electrode active material refers to the average particle size of the electrode active material, and the unit is ⁇ m
  • the specific definition of the above-mentioned D50 particle size includes the following situations: (1) the D50 particle size can be powder The corresponding particle size when the cumulative volume percentage of the electrode active material reaches 50%; (2) D50 particle size can be the corresponding particle size when the cumulative volume percentage of the powder electrode active material reaches 50%; (3) D50 particle size can be the corresponding particle size Powdered electrode active materials or pole pieces are randomly sampled, and the particle size of the electrode active material particles is observed under a scanning electron microscope (scanning electron microscopy, SEM) (the number of electrode active material particles in the sampling object is generally more than 500, preferably in the 1000 or more), measure the corresponding particle diameter when the cumulative volume percentage of the electrode active material particles reaches 50% or the corresponding particle diameter when the cumulative number percentage reaches 50%.
  • SEM scanning electron microscopy
  • the test method specifically includes the following steps: a) Disassemble the fully discharged battery to obtain the pole piece, and then cut any part of the dressing area by argon ions position, to obtain the cross-section sample of the pole piece; b) place the above-mentioned pole piece cross-section sample in the SEM for observation, adjust the voltage and magnification of the electron microscope according to actual needs, so as to ensure that enough particles in the above-mentioned sample can be clearly seen and photographed , to obtain the SEM photo; c) the obtained SEM photo can be imported into the gray scale debugging software (such as Geodict) to carry out statistics on the particle size of the particles, and the particle size of the statistical particles can also be directly identified by artificial eyes; d) the accumulation is carried out for 20 - 30 experiments, the number of particles counted in each experiment is not less than 500pcs, after the above results are counted, the particle size distribution range and D50 particle size of the electrode
  • D is in the range of 0.1 ⁇ m-20 ⁇ m (ie, the D50 particle size of the electrode active material is in the range of 0.1 ⁇ m-20 ⁇ m). Controlling the D50 particle size of the electrode active material within the above range is conducive to inhibiting the side reaction of the electrode active material during the battery’s working process, and is also conducive to ensuring that the electrode pole piece has a large compaction density, which in turn is conducive to ensuring the energy of the battery. density.
  • the actual volume V of the three-dimensional conductive network matrix corresponding to every 100 g of the electrode active material is in the range of 0.01 cm 3 -20 cm 3 .
  • the actual volume V of the corresponding three-dimensional conductive network matrix is controlled within an appropriate range, that is, the quality of the electrode active material loaded on the three-dimensional conductive network matrix per unit volume is controlled, which is conducive to ensuring
  • the mass ratio of the electrode active material in the electrode sheet and the manufacturability of the electrode sheet ensure that the battery has a suitable energy density, a high battery capacity, a good rate characteristic and a long service life.
  • FIG. 1A and FIG. 1B The specific structure of the electrode pad in the embodiment of the present application is introduced below, please refer to FIG. 1A and FIG. 1B .
  • the three-dimensional conductive network matrix is a current collector with a three-dimensional network structure.
  • the three-dimensional conductive network matrix can be obtained by etching the current collector.
  • the current collector does not have a three-dimensional network structure in its entire thickness direction, but has a three-dimensional network structure on the side close to the electrode active material layer.
  • the electrode sheet includes an unetched current collector and a three-dimensional conductive network matrix obtained by etching part of the current collector.
  • the current collector may include two parts along its thickness direction, one part is a solid unetched current collector, and the other part includes a three-dimensional network structure obtained after the current collector is etched.
  • the current collector includes a solid current collector substrate with a certain thickness and a current collector with a three-dimensional network structure (that is, a three-dimensional conductive network network matrix).
  • the current collector may include three parts along its thickness direction, the middle is solid, and the two sides have a three-dimensional network structure.
  • the electrode pad includes an unetched current collector and a two-layer three-dimensional conductive network matrix obtained by etching a part of the current collector.
  • two layers of three-dimensional conductive network matrix are respectively located on both sides of the unetched current collector. It can also be understood that the shapes of the above two layers of three-dimensional conductive network matrix may be the same or different. All the above-mentioned three-dimensional conductive network substrates are loaded with electrode active materials, and the electrode active materials loaded on the two layers of three-dimensional conductive network substrates can be the same or different.
  • the electrode sheet further includes a current collector, and the three-dimensional conductive network matrix is located on at least one side surface of the current collector.
  • the current collector at this time may be an ordinary solid current collector without a three-dimensional network structure.
  • the electrode sheet 100 includes a current collector 10 and a three-dimensional conductive network matrix 11 located on one side surface of the current collector 10 .
  • a three-dimensional conductive network matrix may be provided on one side of the current collector, or a three-dimensional conductive network matrix may be provided on both surfaces of the current collector.
  • FIG. 1B refer to FIG. 1B .
  • the electrode sheet 100 includes a current collector 10 , and three-dimensional conductive network matrices 11 and 12 respectively located on two sides of the current collector 10 .
  • the shapes of the above-mentioned three-dimensional conductive network matrix 11 and 12 may be the same or different. All the above-mentioned three-dimensional conductive network substrates are loaded with electrode active materials, and the electrode active materials loaded on the three-dimensional conductive network substrates 11 and 12 may be the same or different. The normal operation of the battery can only be guaranteed by loading the above-mentioned three-dimensional conductive network matrix loaded with electrode active materials on the current collector.
  • the shape of the three-dimensional conductive network matrix includes a cage shape.
  • the cage structure is conducive to its recombination with the current collector, and is also conducive to simplifying the parameter setting of the three-dimensional conductive network matrix relative to the longitudinal and transverse parameters of the electrode sheet in the design process.
  • the shape of the three-dimensional conductive network matrix can also be three-dimensional foam, N-hedral grid, three-dimensional spherical grid and other three-dimensional network structures.
  • At least part of the material of the three-dimensional conductive network matrix includes at least one of conductive polymers, metal materials, and conductive carbon materials.
  • the metal material may be a single metal substance or a metal alloy.
  • the materials of the three-dimensional conductive network matrix are all conductive materials, specifically at least one of conductive polymers, metal materials, and conductive carbon materials.
  • some materials of the three-dimensional conductive network matrix are non-conductive materials, specifically non-conductive polymers, ceramic materials and the like.
  • a conductive agent may be mixed into the non-conductive material, or a conductive coating may be formed on the surface of the non-conductive material.
  • the above-mentioned conductive agent may be materials such as carbon nanotubes, graphene, fullerene, graphyne, conductive carbon black, Ketjen Black and the like.
  • the above-mentioned non-conductive material is a non-conductive polymer
  • a slight carbonization treatment may be performed on its surface, so that at least part of the materials in the final three-dimensional conductive network matrix are conductive materials.
  • at least the outer surface of the three-dimensional conductive network matrix is made conductive, so that it can fully contact with the electrode active material, so that an efficient conductive network can be formed in the electrode sheet.
  • the electrode active material includes a positive electrode active material or a negative electrode active material. It can be understood that, when the electrode pole piece is a positive pole piece, the electrode active material is a positive pole active material; when the above electrode pole piece is a negative pole piece, the electrode active material is a negative pole active material. Positive electrode active materials and negative electrode active materials are commonly used materials in the field of batteries.
  • the positive electrode active materials include but are not limited to lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide layered At least one of ternary material (NCM), lithium nickel cobalt aluminum oxide layered ternary material (NCA), lithium nickel manganese cobalt aluminum oxygen quaternary material (NCMA).
  • the negative electrode active material includes but not limited to at least one of graphite, natural graphite, mesocarbon microspheres, and silicon carbon negative electrode materials.
  • NCM represents lithium nickel cobalt manganese oxide layered ternary material; in some embodiments, its structural general formula can be expressed as Li 1+m Ni x Co y Mn 1-xy O 2 (x ⁇ 0.33, 0 ⁇ y ⁇ 0.4, 0 ⁇ m ⁇ 0.1).
  • NCA stands for lithium nickel cobalt aluminum oxide layered ternary material; in some embodiments, its general structural formula can be expressed as Li 1+m Ni x Co y Al 1-xy O 2 (x ⁇ 0.33, 0 ⁇ y ⁇ 0.4 , 0 ⁇ m ⁇ 0.1).
  • NCMA stands for lithium nickel manganese cobalt aluminum oxygen quaternary material; in some embodiments, its structural formula can be expressed as Li 1+m Ni x Co y Mn z Al 1-xyz O 2 (x ⁇ 0.33, 0 ⁇ y ⁇ 0.4, 0 ⁇ z ⁇ 0.4, 0 ⁇ m ⁇ 0.1).
  • the true density of lithium cobaltate can be 5.1g/cm 3 ; the true density of the above-mentioned ternary material can be 4.8g/cm 3 ; the true density of lithium manganate can be 4.2g/cm 3 ; The true density of lithium iron phosphate can be 3.6g/cm 3 ; the true density of graphite can be 2.26g/cm 3 .
  • the embodiment of the present application also provides a method for preparing electrode pads, including the following steps:
  • the preparation method has strong controllability, simple operation and can be used for large-scale industrial production.
  • S302 includes placing the three-dimensional conductive network matrix on the current collector, and then coating the mixed material containing the electrode active material and the binder on the three-dimensional conductive network matrix.
  • S303 includes placing the electrode sheet precursor on the current collector, and then performing rolling.
  • the construction of the three-dimensional conductive network matrix in S301 includes but not limited to three-dimensional printing, powder metallurgy, electrodeposition or etching of the current collector.
  • the construction method can be adjusted according to the raw materials used in the preparation of the three-dimensional conductive network matrix.
  • the raw material used for the three-dimensional conductive network matrix is a metal material
  • it can be prepared by three-dimensional laser selective sintering or powder metallurgy.
  • the three-dimensional conductive network matrix is a current collector with a three-dimensional network structure
  • it can be prepared by etching part of the current collector.
  • the raw materials used for the three-dimensional conductive network matrix are conductive polymers and conductive inorganic carbon materials, it can be prepared by three-dimensional printing or electrodeposition.
  • the above method further includes conductive treatment.
  • the conductive treatment includes but is not limited to: before constructing the three-dimensional conductive network matrix, after mixing the conductive agent into the raw material, the three-dimensional conductive network matrix is directly prepared by three-dimensional printing or electrodeposition; Methods After the non-conductive three-dimensional network matrix is prepared, the surface is slightly carbonized or a conductive layer is formed on the surface to obtain a three-dimensional conductive network matrix.
  • the conductive layer is suitable to be arranged on any non-conductive three-dimensional network matrix, and the carbonization treatment is suitable for the above-mentioned non-conductive three-dimensional network matrix whose raw material is a polymer.
  • the raw material used in preparing the three-dimensional conductive network matrix itself is a conductive material (for example, conductive polymer, conductive inorganic carbon material, metal material), the three-dimensional conductive network matrix can be directly constructed.
  • a conductive material for example, conductive polymer, conductive inorganic carbon material, metal material
  • the three-dimensional conductive network matrix can be directly constructed.
  • the above-mentioned conductive treatment can also be performed on it, and the specific conductive treatment method can be determined according to the shape of the material and the preparation method, and will not be repeated here.
  • the forming method in S302 includes coating, and the coating includes drop coating, brush coating, spray coating, dip coating, doctor blade coating, and spin coating.
  • the specific coating method can be determined according to the mixture of the electrode active material and the binder.
  • the mixed material can be liquid or solid.
  • the above-mentioned mixed material is a liquid mixed material containing a solvent, and the liquid mixed material can be formed on the three-dimensional conductive network substrate by means of drip coating, brush coating, spray coating, dip coating, scraping coating, spin coating, etc.
  • the above-mentioned mixed material is a solid mixed material, and the solid mixed material can be formed on the three-dimensional conductive network matrix by means of powder spraying or the like.
  • the embodiment of the present application also provides a lithium battery, which has the electrode sheet provided in the present application.
  • the positive pole piece in the lithium battery is the electrode pole piece provided by the present application
  • the negative pole piece is the traditional electrode pole piece.
  • the negative pole piece in the lithium battery is the electrode pole piece provided by the present application
  • the positive pole piece is a traditional electrode pole piece.
  • both the positive and negative pole pieces in the lithium battery are electrode pole pieces provided by the present application.
  • the above-mentioned battery has high gram capacity and excellent battery capacity retention rate, and the energy density of the battery is high.
  • Three-dimensional conductive network matrix composed of carbon fiber composite materials (Fig. 2). Specifically, make the carbon fiber pass through the groove of polylactic acid (PLA) filled, obtain the carbon fiber that the surface is coated with PLA, and make the carbon fiber that the surface is coated with PLA pass in the hole that has certain pore size, scrape off the excess carbon fiber surface. PLA to obtain filamentous carbon fiber composites.
  • the above-mentioned filamentary carbon fiber composite material is used for 3D printing, and after curing, a three-dimensional conductive network matrix composed of carbon fiber composite material is obtained, and then the surface is slightly carbonized to obtain a three-dimensional conductive network matrix.
  • the actual volume of the three-dimensional conductive network matrix is 1.13 cm 3 .
  • the positive electrode sheet obtained in step (2) is alternately stacked with the negative electrode sheet obtained in step (3) together with the separator, and a battery is prepared by stacking.
  • the positive and negative pole pieces are arranged alternately, and the adjacent positive and negative pole pieces are separated by a diaphragm to obtain a dry battery.
  • Put the dry cell in the aluminum-plastic film outer packaging inject the electrolyte, then vacuum seal it, and leave it at 60°C for 48 hours, then pressurize the layer at 60°C, perform secondary packaging, exhaust, and divide the volume to obtain Laminated soft pack full battery with a capacity of 2.2Ah.
  • the resulting battery is denoted as S1.
  • the resulting battery is denoted as S2.
  • Three-dimensional conductive network matrix 3D printing technology was used to print poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) (PEDOT:PSS) conductive polymer into a three-dimensional conductive network matrix, such that the actual volume of the three-dimensional conductive network matrix is 1.13 cm 3 .
  • PEDOT:PSS poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid)
  • the resulting battery is designated as S3.
  • (1) Construction of three-dimensional conductive network matrix Using 3D printing technology, aluminum powder is used as the printing material, and the three-dimensional conductive network matrix is printed on the positive current collector-aluminum foil by laser selection and sintering.
  • the volume of the three-dimensional conductive network is 1.13cm 3 .
  • the resulting battery is designated as S4.
  • the preparation process is the same as in Example 3, except that: after the three-dimensional conductive network substrate is printed, it is placed in a high-temperature furnace, and its surface is slightly carbonized at 200°C. The resulting battery is designated as S5.
  • the preparation process is the same as that in Example 3, except that carbon nanotubes are added to the 3D printed raw material PEDOT:PSS conductive polymer, and the mass percentage of carbon nanotubes in the mixture obtained is 20%.
  • the resulting battery is designated as S6.
  • the preparation process is the same as in Example 3, except that graphene is added to the 3D printed raw material PEDOT:PSS conductive polymer, and the mass percentage of graphene in the obtained mixture is 20%.
  • the resulting battery is designated as S7.
  • Example 7 the positive pole pieces of Example 8-Example 19 were prepared.
  • the changes in the parameters of each positive pole piece in Examples 8-19 are summarized in Table 1, please refer to Table 1.
  • Li iron phosphate (LFP) has a D50 of 0.5 ⁇ m and a true density of 3.6 g/cm 3 .
  • the fabricated batteries are designated as S8-S19, respectively.
  • the negative electrode sheet of Example 20 also complies with the limitations of the present application. Specifically, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) (PEDOT:PSS) is electrically conductive by using 3D printing technology. The mixture of polymer and graphene (the mass percentage of graphene in the mixture is 20%) is printed into three-dimensional conductive network matrix, with 100g graphite negative electrode active material (D50 is 15 ⁇ m, true density is 2.26g/cm 3 ), 1g thickening Add the agent and 1g of the emulsion into water in a certain order, and mix uniformly to obtain the negative electrode active slurry.
  • PEDOT:PSS poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid)
  • the three-dimensional conductive network matrix is placed on the negative electrode current collector-copper foil, the above-mentioned negative electrode active slurry is coated on the above-mentioned three-dimensional conductive network matrix, and it is rolled after drying to obtain the negative electrode sheet.
  • the above-mentioned negative pole piece and the positive pole piece were assembled into a battery S20. It should be noted that the positive pole piece of the battery S20 was the positive pole piece prepared in Example 7.
  • Example 7 The difference from Example 7 is that the actual volume of the prepared three-dimensional conductive network matrix is 0.06 cm 3 .
  • the resulting battery is designated as DS1.
  • Example 7 The difference from Example 7 is that the actual volume of the prepared three-dimensional conductive network matrix is 20 cm 3 .
  • the resulting battery is designated as DS2.
  • Example 1 100g of LiNi 0.8 Co 0.1 Mn 0.1 (NCM811) (D50 is 1 ⁇ m, true density is 4.8g/cm 3 ) and 0.5g of binder PVDF5130 are dissolved in NMP, after mixing evenly Obtain positive electrode active slurry. Coat the above-mentioned positive electrode active slurry on a carbon fiber composite plate with a volume of 1.13 cm 3 and place it on an aluminum foil, and roll it after drying to obtain a positive electrode sheet without a three-dimensional conductive network matrix . The resulting battery is designated as DS3.
  • Example 1 100g of LiNi 0.8 Co 0.1 Mn 0.1 (NCM811) (D50 is 1 ⁇ m, true density is 4.8g/cm 3 ), 0.5g of binder PVDF5130, 2.486g of carbon fiber conductive agent ( HV) were dissolved together in NMP, and mixed uniformly to obtain positive electrode active slurry.
  • the above positive active slurry is uniformly coated on the aluminum foil, and rolled after drying to obtain a positive electrode sheet without a three-dimensional conductive network matrix.
  • the resulting battery is designated as DS4.
  • Electrochemical performance test is carried out to the electrode pole piece and battery that above-mentioned each embodiment and comparative example make, comprise the following steps:
  • Battery capacity test The capacity test steps are as follows: Ambient temperature 25°C, 2.2Ah as 1C, 1) Charging: 1/3C constant current and constant voltage charge to 4.25V/Cell, cut-off current 0.05C, hold for 30min; 2 ) Discharge: 1/3C constant current discharge to 2.5V/Cell, and leave for 30 minutes; 3) Cycle 3 times, record the third discharge capacity as the actual capacity of the battery. (Wherein, since the positive electrode active material used in Example 8 is LFP, the upper limit voltage is set as 3.8V and the lower limit voltage is 2.0V during the test). The results of the measurement are summarized in Table 3.
  • the longitudinal resistivity of the corresponding positive electrode sheet (Example 1-19) is much smaller than that of the positive electrode sheet whose actual volume is lower than the amount of the design rule (for Ratio 1), and the positive electrode sheet (comparative example 2) whose actual volume of the three-dimensional conductive network matrix exceeds the design rule dosage has no significant improvement on the resistivity, and it will inevitably lead to a decrease in the mass ratio of the positive electrode active material in the electrode sheet, Thus affecting battery performance.
  • the battery with the electrode pole piece of the three-dimensional conductive network structure provided by the present application has a relatively balanced performance in terms of gram capacity and capacity retention after cycling, and when the three-dimensional conductive network structure When the actual volume exceeds the limit of this application, it will result in a lower gram capacity (battery DS2). When the actual volume of the three-dimensional conductive network structure is lower than the limit of the present application, it will result in poor capacity retention (battery DS1).
  • the capacity retention rate of battery S20 is higher after 500 cycles, indicating that when the battery When the positive and negative pole pieces are the same as the electrode pole pieces defined in the present application, the battery cycle capacity retention rate is better.
  • the electrode sheet without a three-dimensional conductive network matrix has no advantage in terms of gram capacity, and the capacity retention rate of the battery is extremely low. quick.

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Abstract

一种电极极片及其制备方法和锂电池，该电极极片包括电极活性材料层，该电极活性材料层包括三维导电网络基体及负载在该三维导电网络基体上的电极活性材料和粘结剂，该三维导电网络基体与该电极活性材料之间满足以下关系式（I）：其中，V为该三维导电网络基体的实际体积，单位为cm3；m是该电极活性材料的质量，单位为g；D为该电极活性材料的D50粒径，单位为μm，ρ为该电极活性材料的真密度，单位为g/cm3；d为单层碳原子层厚度，d的值为0.334nm。

Description

电极极片及其制备方法和锂电池
本申请要求于2022年3月3日提交中国专利局、申请号为202210209397.X、申请名称为“一种电极极片及其制备方法和锂电池”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
本申请涉及锂电池技术领域，具体涉及一种电极极片及其制备方法和锂电池。
背景技术
随着新能源产业的发展，市场对锂电池的能量与功率的要求也日益增加。据文献报道，业界通过提高电极活性材料的面密度、压实密度及其质量占比来提高锂电池的能量密度与功率。但在传统电极极片的生产过程中，业界一般通过添加过量的导电剂来保证电池充放电过程中电极极片的电子导电率。过量的导电剂势必会导致电极极片中活性材料含量过小，进而抑制电池能量密度的发挥。此外，过量的导电剂在电极极片中的分布及形态均难以控制。
发明内容
鉴于此，本申请提供了一种电极极片及其制备方法、锂电池。该电极极片带有三维导电网络基体，且控制三维导电网络基体的实际体积与电极活性材料之间满足特定的关系，可以优化电极极片中的导电网络，从而提高克容量的发挥，进而有利于电池能量密度的发挥，并提高电池的容量保持率。
本申请第一方面提供了一种电极极片，所述电极极片包括电极活性材料层，所述电极活性材料层包括三维导电网络基体及负载在所述三维导电网络基体上的电极活性材料和粘结剂，所述三维导电网络基体与所述电极活性材料之间满足以下关系式：
其中，V为所述三维导电网络基体的实际体积，单位为cm3；m是所述电极活性材料的质量，单位为g；D为所述电极活性材料的D50粒径，单位为μm，ρ为所述电极活性材料的真密度，单位为g/cm3；d为单层碳原子层厚度，d的值为0.334nm。
可选地，所述D在0.1μm-20μm的范围内。
可选地，所述电极极片中，每100g所述电极活性材料对应的所述V在0.01cm3-20cm3的范围内。
可选地，钴酸锂的真密度为5.1g/cm3；所述三元材料的真密度为4.8g/cm3；锰酸锂的真密度为4.2g/cm3；磷酸铁锂的真密度为3.6g/cm3；石墨的真密度为2.26g/cm3。
可选地，所述三维导电网络基体为具有三维网络结构的集流体。
可选地，所述电极极片还包括集流体，所述三维导电网络基体位于所述集流体的至少一侧表面。
可选地，所述三维导电网络基体的形状包括笼状。
可选地，所述三维导电网络基体的至少部分材料包括导电聚合物、金属材料、导电碳材料中的至少一种。
可选地，所述电极极片为正极极片，所述电极活性材料包括正极活性材料，所述正极活性材料包括磷酸铁锂、磷酸锰锂、磷酸锰铁锂、磷酸钒锂、磷酸钴锂、钴酸锂、锰酸锂、镍 锰酸锂、锂镍钴锰氧层状三元材料、锂镍钴铝氧层状三元材料、锂镍锰钴铝氧四元材料中的至少一种。
可选地，所述锂镍钴锰氧层状三元材料的结构通式为Li1+mNixCoyMn1-x-yO2，其中，x≥0.33，0≤y≤0.4，0≤m≤0.1。
可选地，所述锂镍钴铝氧层状三元材料的结构通式为Li1+mNixCoyAl1-x-yO2，其中，x≥0.33，0≤y≤0.4，0≤m≤0.1。
可选地，所述锂镍锰钴铝氧四元材料的结构通式为Li1+mNixCoyMnzAl1-x-y-zO2，其中，x≥0.33，0≤y≤0.4，0≤z≤0.4，0≤m≤0.1。
可选地，所述电极极片为负极极片，所述电极活性材料包括负极活性材料，所述负极活性材料包括石墨、天然石墨、中间相碳微球、硅碳负极材料中的至少一种。
相应地，本申请第二方面提供了一种电极极片的制备方法，包括：
构建三维导电网络基体；
将含电极活性材料与粘结剂的混合物料形成在所述三维导电网络基体上，以使所述电极活性材料负载在三维导电网络基体上，得到电极极片前驱体；
将所述电极极片前驱体进行辊压，得到本申请第一方面提供的电极极片。
可选地，所述将含电极活性材料与粘结剂的混合物料形成在所述三维导电网络基体上包括：
将所述三维导电网络基体置于集流体上，再将含所述电极活性材料与所述粘结剂的所述混合物料涂布在所述三维导电网络基体上。
可选地，所述将所述电极极片前驱体进行辊压包括：
将所述电极极片前驱体置于集流体上，再进行所述辊压。
可选地，所述构建所述三维导电网络基体的方法包括三维打印、粉末冶金、电沉积或对集流体进行蚀刻。
可选地，当制备所述三维导电网络基体使用的原材料为不可导电的材料时，所述构建所述三维导电网络基体还包括导电化处理。
可选地，所述导电化处理包括：
在所述原材料中混入导电剂后，通过所述三维打印或所述电沉积制备所述三维导电网络基体；或
在通过所述三维打印或所述电沉积制备不导电的三维网络基体后，对所述不导电的三维网络基体的表面进行碳化处理，或在所述不导电的三维网络基体的形成导电层，得到所述三维导电基体。
可选地，所述将含所述电极活性材料与所述粘结剂的所述混合物料形成在所述三维导电网络基体上的形成方式包括涂布，所述涂布包括滴涂、刷涂、喷涂、浸涂、刮涂、旋涂。
本申请第三方面提供了一种锂电池，所述锂电池具有本申请第一方面提供的电极极片。
附图说明
图1A和图1B为本申请实施例提供的电极极片截面的结构示意简图；
图2为实施例1制得的三维导电网络基体的结构示意图；
图3为本申请实施例提供的一种电极极片的制备方法的流程示意图。
附图标记说明：100-电极极片；10-集流体；11-三维导电网络基体；12-三维导电网络基体。
具体实施方式
本申请实施例提供了一种电极极片，该电极极片为正极极片或负极极片，电极极片包括电极活性材料层，电极活性材料层包括三维导电网络基体及负载在三维导电网络基体上的电极活性材料和粘结剂，三维导电网络基体与电极活性材料之间满足以下关系式：
其中，V为三维导电网络基体的实际体积，单位为cm3；m是电极活性材料的质量，单位为g；D为电极活性材料的D50粒径，单位为μm，ρ为电极活性材料的真密度，单位为g/cm3；d为单层碳原子层厚度，d的值为0.334nm。
本申请中，首先为该三维导电网络基体的实际体积设定数学计算模型：从三维导电网络基体的功能出发，该基体为电极活性材料之间的导电网络，需要将所有的电极活性材料连接在一起，并使之定型。因此，将电极活性材料预设成直径均为D的球体，众多球体相互紧密排列，可以理解，此时将用于形成三维导电网络基体的材料填充在紧密排列的球体的缝隙之间，则三维导电网络基体材料将形成相互连接的三维导电网络(即，该三维导电网络可以理解成球体中空或其他形状中空的类棱柱相互交错连接而成)。或首先形成预设的三维网络结构，随后可将电极活性材料(预设成直径均为D的球体)填充于三维网络结构空隙中。因此，上述数学计算模型可以看成以直径为D的球体及其外接正六面体为最小体积单元的组合物。
在上述关系式中，6D2代表以电极活性材料D50粒径为直径的球体的外接正六面体(直径为D)的表面积，d×6D2则代表构成上述外接空心正六面体所用三维导电网络结构基材的最小体积(即，最小体积单元中所用三维导电网络结构基材的最小体积)。代表以电极活性材料D50粒径为直径的球体的体积，D3可以代表棱长为D的实心正六面体的体积，则可以代表棱长为D的实心正六面体中挖去一个直径为D的球体后剩下的不规则物体的体积(即，最小体积单元中所用三维导电网络结构基材的最大体积)。可见，在每个最小体积单元中，三维导电网络基体的最小单元体积Vi满足：将上述关系式同时乘以所用电极活性材料小球的总个数即可得到整个三维导电网络基体的实际体积与电极活性材料D50粒径的关系式：
当三维导电网络基体的实际体积V更接近上述关系式中限定的下限值时，能够将导电剂的用量降到最低，即，能在保证电极极片具有良好的导电通路以使电极极片的倍率性能较优、内阻较小的同时，最大限度地提高电极极片中活性材料占比。当上述V更接近上述关系式的上限值时，能够降低三维导电网络基体的制备中对参数控制要求的精准度，在提高电极极片的生产效率的同时，可提高电极极片中活性材料的占比，从而提高克容量发挥，进而有利于电池能量密度的发挥，并提高电池的容量保持率。
此外，在三维导电网络基体的实际体积满足上述关系式的情况下，还可以根据所使用的 电极活性材料的物化特性(例如，粒径、压实密度等)来设计上述三维导电网络基体的具体形状、棱柱的尺寸、棱柱的连接方式等参数，来帮助实现电极活性材料颗粒的定向堆积(即，限定活性材料颗粒的堆积方式和位置)。此外，还可以帮助设计电极极片和电芯的面密度、压实密度，以使电极极片的活性材料具有高面密度和高压实密度，从而提高克容量发挥，进而有利于电池能量密度的发挥，提高电池的容量保持率。
本申请中，上述三维导电网络基体的实际体积是指三维导电网络基体不包含其间隙体积的本征体积，三维导电网络基体的实际体积可以等于其质量与真密度之比。
本申请中，上述电极活性材料的D50粒径指的是电极活性材料的平均粒径，单位为μm，而上述D50粒径的具体定义包括以下几种情况：(1)D50粒径可以是粉末电极活性材料累计体积百分数达到50％时所对应的粒径；(2)D50粒径可以是粉末电极活性材料累计数量百分数达到50％时所对应的粒径；(3)D50粒径可以是对粉末状电极活性材料或极片进行随机取样，在扫描电镜(scanning electron microscopy，SEM)下观测其中电极活性材料颗粒的粒度情况(取样对象中的电极活性材料颗粒数目一般在500以上，最好在1000以上)，测定电极活性材料颗粒的累计体积百分数达到50％时所对应的粒径或累计数量百分数达到50％时所对应的粒径。
当对极片中的电极活性材料颗粒进行随机取样测定其D50粒径时，测试方法具体包括以下步骤：a)将放电完全的电池进行拆解得到极片，然后通过氩离子切割敷料区域的任意位置，得到极片截面样品；b)将上述极片截面样品置于SEM中进行观测，根据实际需求调整电镜电压和放大倍数，以保证能够清晰地看到上述样品中的足够多的颗粒并拍照，得到SEM照片；c)可将得到的SEM照片导入灰度调试软件(例如Geodict)，以对颗粒的粒径进行统计，也可直接采用人工肉眼识别统计颗粒的粒径；d)累积进行20-30次实验，每次实验中统计的颗粒数不少于500pcs，对上述结果进行统计后，得到该电极极片中的电极活性材料颗粒的粒径分布范围以及D50粒径。
本申请一些实施方式中，D在0.1μm-20μm的范围内(即，电极活性材料的D50粒径在0.1μm-20μm的范围内)。控制电极活性材料的D50粒径在上述范围内，有利于抑制电极活性材料在电池工作过程中发生副反应，也有利于保证电极极片具有较大的压实密度，进而有利于保证电池的能量密度。
本申请一些实施方式中，电极极片中，每100g电极活性材料对应的三维导电网络基体的实际体积V在0.01cm3-20cm3的范围内。对于每100g电极活性材料来说，控制对应的三维导电网络基体的实际体积V在合适范围内，也就是控制了每单位体积的三维导电网络基体上负载的电极活性材料的质量，这有利于保证电极活性材料在电极极片中的物质质量占比以及电极极片的可制备性，进而保证电池具有合适的能量密度以及较高的电池容量、较优的倍率特性以及较长的使用寿命。
下面介绍本申请实施例中电极极片的具体结构，请参见图1A和图1B。
本申请一些实施方式中，三维导电网络基体为具有三维网络结构的集流体。此时的三维导电网络基体可通过对集流体进行蚀刻得到。可以理解的是，此时为了便于承载电极活性材料，集流体并非在其整个厚度方向均具有三维网络结构，而是在靠近电极活性材料层的一侧具有三维网络结构。具体地，电极极片包括未蚀刻的集流体，以及对部分集流体进行蚀刻后得到的三维导电网络基体。在一些具体实施例中，集流体沿其厚度方向可以包括两部分，一部分为实心状的未蚀刻的集流体，另一部分包括集流体蚀刻后得到的三维网络结构。换句话说，该集流体包括一定厚度的实心集流体基底及具有三维网络结构的集流体(即三维导电网 络基体)。在另一些实施例中，集流体沿其厚度方向可以包括三部分，中间为实心状，两侧具有三维网络结构。具体地，电极极片包括未蚀刻的集流体，以及对部分集流体进行蚀刻后得到的两层三维导电网络基体。其中，两层三维导电网络基体分别位于未蚀刻的集流体的两侧。还可以理解的是，上述两层三维导电网络基体的形状可以相同，也可以不同。上述所有的三维导电网络基体上均负载有电极活性材料，两层三维导电网络基体上负载的电极活性材料可以相同也可以不同。
本申请另外一些实施方式中，电极极片还包括集流体，三维导电网络基体位于集流体的至少一侧表面。此时的集流体可以为普通的实心集流体，不具有三维网络结构。具体地，可参见图1A。此时，电极极片100包括集流体10，以及位于集流体10一侧表面的三维导电网络基体11。进一步地，可以是集流体的一侧表面上设有三维导电网络基体，还可以是集流体的两侧表面上均设有三维导电网络基体。具体地，可参见图1B。此时，电极极片100包括集流体10，以及分别位于集流体10两侧表面的三维导电网络基体11以及12。上述三维导电网络基体11以及12的形状可以相同，也可以不同。上述所有的三维导电网络基体上均负载有电极活性材料，三维导电网络基体11以及12上负载的电极活性材料可以相同也可以不同。将上述负载有电极活性材料的三维导电网络基体负载在集流体上，才能保障电池的正常工作。
本申请一些实施方式中，三维导电网络基体的形状包括笼状。笼状结构有利于其与集流体的复合，也有利于简化三维导电网络基体在设计的过程中相对于电极极片的纵向及横向的参数设定。另一些实施方式中，三维导电网络基体的形状还可以是三维泡沫状、N面体网格状、三维球形网格状等其他一些呈三维网状的结构。
本申请实施方式中，三维导电网络基体的至少部分材料包括导电聚合物、金属材料、导电碳材料中的至少一种。其中，金属材料可以是金属单质、金属合金。在一些具体实施例中，三维导电网络基体的材料全部为导电材料，具体可以为导电聚合物、金属材料、导电碳材料中的至少一种。另一些实施例中，三维导电网络基体的部分材料为不可导电的材料，具体可以为不导电聚合物、陶瓷材料等。在上述情况下，可以在上述不可导电的材料中混入导电剂，也可以在上述不可导电的材料的表面形成导电涂层。其中，上述导电剂可以是碳纳米管、石墨烯、富勒烯、石墨炔、导电炭黑、科琴黑等材料。特别地，当上述不可导电的材料为不导电聚合物时，还可以对其表面进行轻微碳化处理，以使最终的三维导电网络基体中的至少部分材料为可导电的材料。进一步地，使得至少三维导电网络基体的外表面导电，这样才可以与电极活性材料充分接触，从而可以在电极极片中形成高效的导电网络。
本申请实施方式中，电极活性材料包括正极活性材料或负极活性材料。可以理解的是，当上述电极极片为正极极片时，电极活性材料为正极活性材料；当上述电极极片为负极极片时，电极活性材料为负极活性材料。正极活性材料、负极活性材料为电池领域的常用材料。
其中，正极活性材料包括但不限于磷酸铁锂、磷酸锰锂、磷酸锰铁锂、磷酸钒锂、磷酸钴锂、钴酸锂、锰酸锂、镍锰酸锂、锂镍钴锰氧层状三元材料(NCM)、锂镍钴铝氧层状三元材料(NCA)、锂镍锰钴铝氧四元材料(NCMA)中的至少一种。负极活性材料包括但不限于石墨、天然石墨、中间相碳微球、硅碳负极材料中的至少一种。其中，NCM代表锂镍钴锰氧层状三元材料；在一些实施方式中，其结构通式可以表示为Li1+mNixCoyMn1-x-yO2(x≥0.33，0≤y≤0.4，0≤m≤0.1)。NCA代表锂镍钴铝氧层状三元材料；在一些实施方式中，其结构通式可以表示为Li1+mNixCoyAl1-x-yO2(x≥0.33，0≤y≤0.4，0≤m≤0.1)。NCMA代表锂镍锰钴铝氧四元材料；在一些实施方式中，其结构通式可以表示为Li1+mNixCoyMnzAl1-x-y-zO2(x≥0.33，0≤y≤0.4，0≤z≤0.4，0≤m≤0.1)。
本申请一些具体实施例中，钴酸锂的真密度可以为5.1g/cm3；上述三元材料的真密度可以为4.8g/cm3；锰酸锂的真密度可以为4.2g/cm3；磷酸铁锂的真密度可以为3.6g/cm3；石墨的真密度可以为2.26g/cm3。
相应地，参考图3，本申请实施例还提供了一种电极极片的制备方法，包括以下步骤：
S301，构建三维导电网络基体；
S302，将含电极活性材料与粘结剂的混合物料形成在三维导电网络基体上，以使电极活性材料负载在三维导电网络基体上，得到电极极片前驱体；
S303，将电极极片前驱体进行辊压，得到本申请提供的电极极片。
该制备方法可控性强，操作简单，可进行大规模的工业化生产。
本申请一些实施方式中，S302包括将三维导电网络基体置于集流体上，再将含电极活性材料与粘结剂的混合物料涂布在三维导电网络基体上。另一些实施方式中，S303包括将电极极片前驱体置于集流体上，再进行辊压。
本申请实施方式中，S301中的构建三维导电网络基体包括但不限于三维打印、粉末冶金、电沉积或对集流体进行蚀刻。其中，构建方法可根据制备三维导电网络基体时使用的原材料来调整。例如，在一些具体实施例中，当三维导电网络基体采用的原材料为金属材料时，则可以采用三维激光选取烧结或粉末冶金的方法制备。在一些实施例中，当三维导电网络基体为具有三维网络结构的集流体时，则可以对部分集流体进行蚀刻来进行制备。当三维导电网络基体采用的原材料为导电的聚合物、导电的无机碳材料时，可以采用三维打印或电沉积的方法制备。
在一些实施方式中，当制备三维导电网络基体时使用的原材料为不可导电的材料时(例如不导电的陶瓷、不导电的聚合物时)，上述方法还包括导电化处理。该导电化处理包括但不限于：在构建三维导电网络基体之前，在该原材料中混入导电剂后，直接采用三维打印或电沉积的方法制备三维导电网络基体；或在采用三维打印或电沉积的方法制得不导电的三维网络基体后，对其进行表面轻微碳化处理或在其表面形成导电层，以得到三维导电网络基体。其中，导电层适合设置在任意不导电的三维网络基体上，碳化处理适用于上述原材料为聚合物的不导电的三维网络基体。
当制备三维导电网络基体时使用的原材料本身就为可导电材料(例如，导电聚合物、导电无机碳材料、金属材料)时，可直接构建得到三维导电网络基体。当然，也可以对其进行上述导电化处理，具体的导电化处理方式可根据材料的形态以及制备方法进行确定，此处不再赘述。
本申请实施方式中，S302中的形成方式包括涂布，上述涂布包括滴涂、刷涂、喷涂、浸涂、刮涂、旋涂。具体的涂布方式可根据电极活性材料与粘结剂的混合物料来定。该混合物料可以是液态或固态。本申请一些实施方式中，上述混合物料为含有溶剂的液态混合物料，可将该液态混合物料通过滴涂、刷涂、喷涂、浸涂、刮涂、旋涂等方式形成在三维导电网络基体上。另一些实施方式中，上述混合物料为固态混合物料，可将该固态混合物料通过粉末喷涂等方式形成在三维导电网络基体上。
本申请实施例还提供了一种锂电池，该锂电池具有本申请提供的电极极片。一些实施方式中，锂电池中的正极极片为本申请提供的电极极片，负极极片为传统的电极极片。一些实施方式中，锂电池中的负极极片为本申请提供的电极极片，正极极片为传统的电极极片。一些实施方式中，锂电池中的正、负极极片均为本申请提供的电极极片。
上述电池具有较高的克容量和优异的电池容量保持率，且电池的能量密度较高。
下面结合具体实施例进一步详细说明本申请技术方案。
实施例1
(1)三维导电网络基体的构建：采用3D打印技术，制备由碳纤维复合材料构成的三维导电网络基体(图2)。具体地，使碳纤维通过盛有的聚乳酸(PLA)的槽中，得到表面涂覆有PLA的碳纤维，并使表面涂覆有PLA的碳纤维通过具有一定孔径的孔洞中，刮去碳纤维表面多余的PLA，得到丝状的碳纤维复合材料。利用上述丝状的碳纤维复合材料进行3D打印，经固化后得到由碳纤维复合材料构成的三维导电网络基体，再对其表面进行轻微碳化，得到三维导电网络基体。该三维导电网络基体的实际体积为1.13cm3。
(2)正极极片的制备：将100g的LiNi0.8Co0.1Mn0.1(NCM811)(D50为1μm，真密度为4.8g/cm3)与0.5g粘结剂PVDF5130溶解在N-甲基吡咯烷酮(NMP)中，混合均匀后得到正极活性浆料。将三维导电网络基体置于正极集流体-铝箔之上，并将上述正极活性浆料涂覆在三维导电网络基体上，干燥后对其进行辊压，得到正极极片。
(3)负极极片的制备：将100g的石墨负极活性材料、1g的增稠剂、1g的乳液、2g导电碳黑按一定顺序加入水中，混合均匀后得到负极活性浆料。将上述负极活性材料均匀地涂覆在负极集流体-铜箔的表面。烘干后，经过辊压机压片后得到负极极片。
(4)电池的制备
采用步骤(2)获得的正极极片与步骤(3)获得的负极极片与隔膜一起交替层叠，通过叠片方式制备电池。其中，正、负极极片交替排布，且相邻正、负极极片之间被隔膜隔开，获得干电芯。将干电芯置于铝塑膜外包装中，注入电解液，然后抽真空密封，在60℃下搁置48h，接着于60℃下加压化层、二次封装、排气、分容后得到容量为2.2Ah的叠片软包全电池。制得的电池记作S1。
实施例2
实施例2与实施例1的区别在于：
(1)三维导电网络基体的构建：使用激光刻蚀技术，对正极集流体(铝箔)进行三维导电网络刻蚀，使得集流体基底中三维导电网络基体的实际体积为1.13cm3。
(2)正极极片的制备：将100g的LiNi0.8Co0.1Mn0.1(NCM811)(D50为1μm，真密度为4.8g/cm3)与0.5g的粘结剂PVDF5130溶解在NMP中，混合均匀后得到正极活性浆料。将上述正极活性浆料均匀地涂敷于三维导电网络基体之上，干燥后对其进行辊压，得到正极极片。
制得的电池记作S2。
实施例3
实施例3与实施例1的区别在于：
(1)三维导电网络基体的构建：采用3D打印技术，将聚(3,4-亚乙二氧基噻吩)-聚(苯乙烯磺酸)(PEDOT：PSS)导电聚合物打印成三维导电网络基体，使得三维导电网络基体的实际体积为1.13cm3。
(2)正极极片的制备：将100g的LiNi0.8Co0.1Mn0.1(NCM811)(D50为1μm，真密度为4.8g/cm3)与0.5g的粘结剂PVDF5130溶解在NMP中，混合均匀后得到正极活性浆料。将三维导电网络基体置于铝箔之上，并将上述正极活性浆料涂覆在三维导电网络基体上，干燥后对三维导电网络基体和铝箔进行辊压，得到正极极片。
制得的电池记作S3。
实施例4
实施例4与实施例1的区别在于：
(1)三维导电网络基体的构建：采用3D打印技术，铝粉作为打印材料，通过激光选取烧结在正极集流体-铝箔上打印三维导电网络基体，三维导电网络体积为1.13cm3。
(2)正极极片的制备：将100g的LiNi0.8Co0.1Mn0.1(NCM811)(D50为1μm，真密度为4.8g/cm3)与0.5g的粘结剂PVDF5130溶解在NMP中，混合均匀后得到正极活性浆料，并将上述正极活性浆料涂覆在三维导电网络基体上，干燥后对三维导电网络基体和铝箔进行辊压，得到正极极片。
制得的电池记作S4。
实施例5
制备过程同实施例3，不同的是：三维导电网络基体打印完成后，将其置于高温炉中，在200℃下对其表面进行轻微碳化。制得的电池记作S5。
实施例6
制备过程同实施例3，不同的是：在3D打印的原材料PEDOT：PSS导电聚合物中加入碳纳米管，得到的混合物中碳纳米管的质量百分数为20％。制得的电池记作S6。
实施例7
制备过程同实施例3，不同的是：在3D打印的原材料PEDOT：PSS导电聚合物中加入石墨烯，得到的混合物中石墨烯的质量百分数为20％。制得的电池记作S7。
实施例8-实施例19
按照实施例7的制备方法，制备实施例8-实施例19的正极极片，实施例8-19中各正极极片的参数的改变汇总在表1中，请参见表1。其中，磷酸铁锂(LFP)的D50为0.5μm、真密度为3.6g/cm3。制得的电池分别记作S8-S19。
实施例20
实施例20的负极极片也符合本申请的限定，具体地，采用3D打印技术，将聚(3,4-亚乙二氧基噻吩)-聚(苯乙烯磺酸)(PEDOT：PSS)导电聚合物和石墨烯的混合物(混合物中石墨烯的质量百分数为20％)打印成三维导电网络基体，将100g石墨负极活性材料(D50为15μm，真密度为2.26g/cm3)、1g增稠剂、1g乳液按一定顺序加入水中，混合均匀后得到负极活性浆料。将三维导电网络基体置于负极集流体-铜箔之上，并将上述负极活性浆料涂覆在上述三维导电网络基体上，干燥后对其进行辊压，得到负极极片。将上述负极极片与正极极片组装成电池S20，需要说明的是，电池S20的正极极片为实施例7制得的正极极片。
为突出本申请实施例的有益效果，设置以下对比例。
对比例1
与实施例7的区别为：制得的三维导电网络基体的实际体积为0.06cm3。制得的电池记作DS1。
对比例2
与实施例7的区别为：制得的三维导电网络基体的实际体积为20cm3。制得的电池记作DS2。
对比例3
与实施例1的区别为：将100g的LiNi0.8Co0.1Mn0.1(NCM811)(D50为1μm，真密度为4.8g/cm3)与0.5g的粘结剂PVDF5130溶解于NMP中，混合均匀后得到正极活性浆料。将上述正极活性浆料涂覆在体积为1.13cm3的表面经过碳化的碳纤维复合板材上，并将其放置在铝箔上，干燥后对其进行辊压，得到无三维导电网络基体的正极极片。制得的电池记作DS3。
对比例4
与实施例1的区别为：将100g的LiNi0.8Co0.1Mn0.1(NCM811)(D50为1μm，真密度为4.8g/cm3)、0.5g的粘结剂PVDF5130、2.486g的碳纤维导电剂(HV)一起溶解于NMP中，混合均匀后得到正极活性浆料。将上述正极活性浆料均匀地涂覆在铝箔上，干燥后对其进行辊压，得到无三维导电网络基体的正极极片。制得的电池记作DS4。
表1各实施例与对比例制得的电极极片的参数汇总表

对上述各实施例及对比例制得的电极极片及电池进行电化学性能测试，包括以下步骤：
(1)电极极片的纵向电阻率测试：使用纵向电阻率仪测试所得正极极片的纵向电阻率，测试压强设置为25Mpa，保压时间为30s，每组电极极片取10个点测试后取平均值。将所得数据汇总在表2中。
(2)电极极片的极限压实密度测试：不断增大辊压机压力，并使用万分尺测试电极极片的厚度，直到电极极片厚度不会再减少，得到电极极片的极限压实密度。将所得数据汇总在表3中。
(3)电池容量测试：容量测试步骤如下：环境温度25℃，以2.2Ah为1C，1)充电：1/3C恒流恒压充电至4.25V/Cell，截止电流0.05C，搁置30min；2)放电：1/3C恒流放电至2.5V/Cell，搁置30min；3)循环3次，记录第3次放电容量为电池的真实容量。(其中，因实施例8使用的正极活性材料为LFP，因此测试过程中设置上限电压为3.8V，下限电压为2.0V)。测定的结果汇总在表3中。
(4)电池循环性能测试：以2.2Ah为1C，1)充电：1/3C恒流恒压充电至4.25V/Cell，截止电流0.05C，搁置30min；2)放电：1/3C恒流放电至2.5V/Cell，搁置30min；3)循环3次，记录第3次放电容量为电池的真实容量C0；4)充电：以电池真实容量C0为1C，1C恒流恒压充电至4.25V，截止电流0.05C；5)搁置30min；6)放电：以电池真实容量C0为1C，1C恒流放电至2.5V；7)搁置30min；8)循环4)到7)共计500次。(其中，因实施例8使用的正极活性材料为LFP，因此测试过程中设置上限电压为3.8V，下限电压为2.0V)。测定的结果汇总在表3中。
表2实施例和对比例制得的电极极片的纵向电阻率和极限压实密度

表3实施例和对比例制得的电池的克容量及容量保持率

由表2中数据可知，具有三维导电网络基体的正极极片(实施例1-19)的纵向电阻率远远小于无三维导电网络基体的正极极片(对比例3)。此外，三维导电网络基体的实际体积在设计规则的限定值之内时，相应的正极极片(实施例1-19)的纵向电阻率远小于实际体积低于设计规则用量的正极极片(对比例1)，而三维导电网络基体的实际体积超出设计规则用量的正极极片(对比例2)则对电阻率无明显改善，并且其势必会导致极片中正极活性材料的质量占比降低，从而影响电池性能。而从正极极片的极限压实密度数据中可以看出，具有三维导电网络基体的正极极片(实施例1-19以及对比例1-2)的极限压实密度大于不含三维导电网络基体的正极极片(对比例3)，但当三维导电网络基体的实际体积超出三维网络设计规则用量时，对应的正极极片的极片压实密度会有所降低(对比例2)。
从表3中数据可以看出，具有本申请提供的三维导电网络结构的电极极片的电池，其在克容量发挥及循环后容量保持率方面有着比较均衡的表现，而当三维导电网络结构的实际体积超过本申请限定时，会导致克容量较低(电池DS2)。当三维导电网络结构的实际体积低于本申请限定时，会导致容量保持率较差(电池DS1)。当电池的正、负极极片同时为本申请限定的电极极片时(电池S20)，相较于使用相同正极极片的电池S7，电池S20循环500次后容量保持率更高，说明当电池的正、负极极片同为本申请限定的电极极片时，其电池循环容量保持率更优。此外，从实施例电池S1-S20和对比例电池DS3-DS3的数据可以看出，不具有三维导电网络基体的电极极片，其在克容量方面无任何优势，并且电池的容量保持率下降极快。
以上是本申请的示例性实施方式，应当指出，对于本技术领域的普通技术人员来说，在不脱离本申请原理的前提下，还可以对其做出若干改进和润饰，这些改进和润饰也视为本申请的保护范围。

Claims (20)

  1. 一种电极极片(100)，其特征在于，所述电极极片(100)包括电极活性材料层，所述电极活性材料层包括三维导电网络基体(11)及负载在所述三维导电网络基体(11)上的电极活性材料和粘结剂，所述三维导电网络基体(11)与所述电极活性材料之间满足以下关系式：
    其中，V为所述三维导电网络基体(11)的实际体积，单位为cm3；m是所述电极活性材料的质量，单位为g；D为所述电极活性材料的D50粒径，单位为μm，ρ为所述电极活性材料的真密度，单位为g/cm3；d为单层碳原子层厚度，d的值为0.334nm。
  2. 根据权利要求1所述的电极极片(100)，其特征在于，所述D在0.1μm-20μm的范围内。
  3. 根据权利要求1或2所述的电极极片(100)，其特征在于，所述电极极片(100)中，每100g所述电极活性材料对应的所述V在0.01cm3-20cm3的范围内。
  4. 根据权利要求1至3任一项所述的电极极片(100)，其特征在于，所述三维导电网络基体(11)为具有三维网络结构的集流体。
  5. 根据权利要求1至3任一项所述的电极极片(100)，其特征在于，所述电极极片(100)还包括集流体(10)，所述三维导电网络基体(11)位于所述集流体(10)的至少一侧表面。
  6. 根据权利要求1至5任一项所述的电极极片(100)，其特征在于，所述三维导电网络基体(11)的形状包括笼状。
  7. 根据权利要求1至6任一项所述的电极极片(100)，其特征在于，所述三维导电网络基体(11)的至少部分材料包括导电聚合物、金属材料、导电碳材料中的至少一种。
  8. 根据权利要求1至7任一项所述的电极极片(100)，其特征在于，所述电极极片(100)为正极极片，所述电极活性材料包括正极活性材料，所述正极活性材料包括磷酸铁锂、磷酸锰锂、磷酸锰铁锂、磷酸钒锂、磷酸钴锂、钴酸锂、锰酸锂、镍锰酸锂、锂镍钴锰氧层状三元材料、锂镍钴铝氧层状三元材料、锂镍锰钴铝氧四元材料中的至少一种。
  9. 根据权利要求8所述的电极极片(100)，其特征在于，所述锂镍钴锰氧层状三元材料的结构通式为Li1+mNixCoyMn1-x-yO2，其中，x≥0.33，0≤y≤0.4，0≤m≤0.1。
  10. 根据权利要求8或9所述的电极极片(100)，其特征在于，所述锂镍钴铝氧层状三元材料的结构通式为Li1+mNixCoyAl1-x-yO2，其中，x≥0.33，0≤y≤0.4，0≤m≤0.1。
  11. 根据权利要求9至10任一项所述的电极极片(100)，其特征在于，所述锂镍锰钴铝氧四元材料的结构通式为Li1+mNixCoyMnzAl1-x-y-zO2，其中，x≥0.33，0≤y≤0.4，0≤z≤0.4，0≤m≤0.1。
  12. 根据权利要求1至7任一项所述的电极极片(100)，其特征在于，所述电极极片(100)为负极极片，所述电极活性材料包括负极活性材料，所述负极活性材料包括石墨、天然石墨、中间相碳微球、硅碳负极材料中的至少一种。
  13. 一种电极极片的制备方法，其特征在于，包括：
    构建三维导电网络基体(S301)；
    将含电极活性材料与粘结剂的混合物料形成在所述三维导电网络基体上，以使所述电极活性材料和粘结剂负载在所述三维导电网络基体上，得到电极极片前驱体(S302)；
    将所述电极极片前驱体进行辊压，得到如权利要求1-12任一项所述的电极极片(S303)。
  14. 根据权利要求13所述的制备方法，其特征在于，所述将含电极活性材料与粘结剂的混合物料形成在所述三维导电网络基体上包括：
    将所述三维导电网络基体置于集流体上，再将含所述电极活性材料与所述粘结剂的所述混合物料涂布在所述三维导电网络基体上。
  15. 根据权利要求13所述的制备方法，其特征在于，所述将所述电极极片前驱体进行辊压包括：
    将所述电极极片前驱体置于集流体上，再进行所述辊压。
  16. 根据权利要求13至15任一项所述的制备方法，其特征在于，所述构建所述三维导电网络基体包括：
    三维打印、粉末冶金、电沉积或对集流体进行蚀刻。
  17. 根据权利要求16所述的制备方法，其特征在于，当制备所述三维导电网络基体使用的原材料为不可导电的材料时，所述构建所述三维导电网络基体还包括导电化处理。
  18. 根据权利要求17所述的制备方法，其特征在于，所述导电化处理包括：
    在所述原材料中混入导电剂后，通过所述三维打印或所述电沉积制备所述三维导电网络基体；或
    在通过所述三维打印或所述电沉积制备不导电的三维网络基体后，对所述不导电的三维网络基体的表面进行碳化处理，或在所述不导电的三维网络基体的形成导电层，得到所述三维导电基体。
  19. 根据权利要求13至18任一项所述的制备方法，其特征在于，所述将含所述电极活性材料与所述粘结剂的所述混合物料形成在所述三维导电网络基体上的形成方式包括涂布，所述涂布包括滴涂、刷涂、喷涂、浸涂、刮涂、旋涂。
  20. 一种锂电池，其特征在于，所述锂电池具有如权利要求1-12任一项所述的电极极片(100)。
PCT/CN2023/079503 2022-03-03 2023-03-03 电极极片及其制备方法和锂电池 Ceased WO2023165593A1 (zh)

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