WO2022199681A1 - 锂离子电池及动力车辆 - Google Patents

锂离子电池及动力车辆 Download PDF

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WO2022199681A1
WO2022199681A1 PCT/CN2022/082943 CN2022082943W WO2022199681A1 WO 2022199681 A1 WO2022199681 A1 WO 2022199681A1 CN 2022082943 W CN2022082943 W CN 2022082943W WO 2022199681 A1 WO2022199681 A1 WO 2022199681A1
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positive electrode
lithium
negative electrode
ion battery
battery
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French (fr)
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陈娜
邓暄炜
潘仪
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BYD Co Ltd
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BYD Co Ltd
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Priority to CA3213251A priority Critical patent/CA3213251A1/en
Priority to KR1020237033303A priority patent/KR20230150863A/ko
Priority to JP2023558576A priority patent/JP7698731B2/ja
Priority to EP22774335.8A priority patent/EP4300633A4/en
Publication of WO2022199681A1 publication Critical patent/WO2022199681A1/zh
Priority to US18/473,996 priority patent/US20240021793A1/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
    • H01M4/13—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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
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    • 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
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
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    • H01M10/058—Construction or manufacture
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/44—Methods for charging or discharging
    • H01M10/446—Initial charging measures
    • H—ELECTRICITY
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    • 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
    • H01M4/36—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
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • 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
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
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    • 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
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    • 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
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/44—Methods for charging or discharging
    • H—ELECTRICITY
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
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    • 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
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M2010/4292—Aspects relating to capacity ratio of electrodes/electrolyte or anode/cathode
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • 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
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • H01M4/583—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
    • 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 disclosure relates to the technical field of batteries, and in particular, to a lithium-ion battery and a power vehicle.
  • Lithium-ion batteries are a new generation of green high-energy batteries, which are widely used in electronic equipment, automobiles, aerospace and other fields.
  • the choice of cathode materials directly affects the performance of lithium-ion batteries, and mixing a variety of cathode materials is one of the commonly used methods in the battery field.
  • the mixed use of existing positive electrode materials mainly includes: mixed use of lithium iron phosphate material (LFP) and ternary material; mixed use of lithium manganese iron phosphate material (LMFP) and ternary material; mixed use of lithium manganate and ternary material, etc.
  • LFP lithium iron phosphate material
  • LMFP lithium manganese iron phosphate material
  • the former mixed solution will cause the risk of lithium precipitation when the battery is charged at a high rate under high SOC (state of charge, negative state), reducing the safety of the battery; while the latter two mixed solutions can alleviate the problem to a certain extent
  • the battery has the risk of lithium deposition under high-rate charging, but when it is discharged at low SOC, the cut-off voltage is quickly reached, and the discharge power is low.
  • the specific capacity of the positive electrode of the lithium battery mixed with a variety of positive electrode materials is low, which is not conducive to the improvement of the energy density of the battery.
  • the lithium-ion batteries prepared from them can be made in a high SOC state. It is not easy to precipitate lithium during charging, and the power is large when discharging in a low SOC state, and the specific capacity of each material can be fully utilized, and it has good cycle stability.
  • the present disclosure provides a lithium ion battery, including a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator between the positive electrode sheet and the negative electrode sheet, wherein the positive electrode sheet includes a positive electrode current collector and is disposed on the A positive electrode material layer on the positive electrode current collector, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer arranged on the negative electrode current collector, the negative electrode active material in the negative electrode material layer is graphite, and the positive electrode material
  • M 1 and ⁇ 1 are the first charge specific capacity and first efficiency of the lithium iron manganese phosphate material, respectively
  • M 2 and ⁇ 2 are the first charge specific capacity and first efficiency of the lithium iron phosphate material, respectively
  • M 3 , ⁇ 3 is the first charge specific capacity and the first efficiency of the ternary material, respectively
  • M 4 , ⁇ 4 are the first discharge specific capacity and the first efficiency of the graphite, respectively
  • X is the positive electrode active material on the positive electrode sheet.
  • the dressing amount, Y is the dressing amount of the graphite on the negative electrode sheet; wherein, the units of the M 1 , M 2 , M 3 , and M 4 are all mAh/g; the units of the X and Y are g .
  • LMFP, LFP and ternary materials are mixed as positive electrode active materials, and the mixing ratio of the three is adjusted, and the above-mentioned battery operation angles such as the specific capacity and initial efficiency of the positive and negative electrode active materials are jointly controlled.
  • the parameters ⁇ and ⁇ are within a certain range, which can better balance the charge-discharge characteristics of various materials, so that the positive electrode active material has a higher charge-discharge platform in both high SOC and low SOC states, thereby making the battery in high SOC state.
  • the lithium-ion battery can have good rate and power performance, high energy density and the like.
  • ⁇ (M 1 ⁇ 1 ⁇ A 1 +M 2 ⁇ 2 ⁇ A 2 +M 3 ⁇ 3 ⁇ A 3 ) ⁇ b ⁇ c/(a ⁇ A 3 ⁇ 1000), and ⁇ satisfies: 0.45 ⁇ 1.55;
  • a is the residual alkali content of the ternary material
  • b is the liquid injection coefficient of the lithium ion battery, in g/Ah
  • c is the residual water content in the electrolyte of the assembled lithium ion battery The theoretical value of ; the a and c are in ppm.
  • the lithium-ion battery can also have good rate and power performance, high energy density, good cycle performance, high safety and other properties.
  • the b is a constant in the range of 2.9-3.8
  • the c is in the range of 200ppm-400ppm
  • the a is in the range of 500ppm-1500ppm.
  • the A 2 is 2-5 times the A 1 .
  • the A 1 ranges from 10% to 25%.
  • the ratio of X to Y is in the range of 1.71-1.89.
  • the molar amount of manganese accounts for 0.75-0.9 of the sum of the molar amounts of ferromanganese.
  • the particle size D50 of the lithium iron phosphate material is 0.8 ⁇ m-1.3 ⁇ m
  • the particle size D50 of the lithium iron manganese phosphate material is 10 ⁇ m-15 ⁇ m
  • the particle size D50 of the ternary material is 4 ⁇ m-6 ⁇ m.
  • the present disclosure provides a powered vehicle including the lithium-ion battery described in the first aspect of the present disclosure.
  • Figure 1a is the charge-discharge curve of the lithium iron manganese phosphate-graphite system battery
  • Figure 1b shows the charge-discharge curve of the lithium iron phosphate-graphite system battery
  • Figure 1c shows the charge-discharge curve of the ternary material-graphite system battery
  • FIG. 2 is a charge-discharge curve of a full battery in Example 4 of the present disclosure.
  • An embodiment of the present disclosure provides a lithium-ion battery, including a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator between the positive electrode sheet and the negative electrode sheet, wherein the positive electrode sheet includes a positive electrode current collector and is disposed on the A positive electrode material layer on the positive electrode current collector, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on the negative electrode current collector, the negative electrode active material in the negative electrode material layer is graphite, and the positive electrode material layer includes A positive electrode active material composed of a lithium manganese iron phosphate material (LMFP), a lithium iron phosphate material (LFP) and a ternary material; wherein the lithium manganese iron phosphate material, the lithium iron phosphate material and the ternary material are active in the positive electrode
  • M 1 and ⁇ 1 are the first charge specific capacity and first efficiency of the lithium iron manganese phosphate material, respectively
  • M 2 and ⁇ 2 are the first charge specific capacity and first efficiency of the lithium iron phosphate material, respectively
  • M 3 , ⁇ 3 is the first charge specific capacity and the first efficiency of the ternary material, respectively
  • M 4 , ⁇ 4 are the first discharge specific capacity and the first efficiency of the graphite, respectively
  • X is the positive electrode active material on the positive electrode sheet.
  • the dressing amount, Y is the dressing amount of the graphite on the negative electrode sheet; wherein, the units of M 1 , M 2 , M 3 , and M 4 are all mAh/g; the units of X and Y are g.
  • M 1 , M 2 , M 3 , M 4 , ⁇ 1 , ⁇ 2 , ⁇ 3 , ⁇ 4 can all be made of a single LMFP, LFP, ternary or graphite material. Battery test got. X and Y are parameters determined when designing the battery.
  • ⁇ represents the excess ratio of the capacity of the negative electrode sheet to the capacity of the positive electrode sheet. If the ⁇ value is too low, there is a risk of lithium precipitation on the negative electrode sheet during the charging process; if the ⁇ value is too high, the dressing amount of the negative electrode sheet is too large, and the negative electrode sheet needs to be consumed when forming the SEI film (solid electrolyte interface film). More active lithium is not conducive to the development of the capacity of the positive electrode active material, and will reduce the energy density of the battery. Controlling 1.03 ⁇ 1.15 can not only lower the risk of lithium precipitation in the battery, but also help the capacity of its positive active material. In some embodiments of the present disclosure, 1.05 ⁇ 1.12, and in still other embodiments of the present disclosure, 1.08 ⁇ 1.12.
  • the above ⁇ represents the balance relationship of the first efficiency of the LMFP material, the LFP material, the graphite, and the ternary material.
  • the first efficiency of the ternary material ⁇ the first efficiency of the graphite ⁇ the first efficiency of the LMFP material ⁇ the first efficiency of the LFP material, when the negative electrode is graphite and only LFP and/or LMFP material is used as the positive electrode active material, the LFP/LMFP material is due to the first efficiency
  • the loss of irreversible lithium caused by high is less, which is not enough for graphite consumption to form SEI film, so graphite will also consume other active lithium in the battery system, reduce the specific capacity of LFP/LMFP, and then cause the battery energy density to become lower; and ternary Due to the low initial efficiency of the material, more irreversible lithium left in the negative electrode is sufficient for the consumption of the negative electrode to form the SEI film.
  • the present disclosure controls the value range of ⁇ to be: 0.55 ⁇ 1.5, which is more conducive to improving the specific capacity of the overall positive electrode active material and improving the energy density of the battery.
  • the different charge-discharge characteristics of the three materials can be utilized, wherein the LMFP material has a certain length of discharge plateau in the high-voltage range (see Figure 1a, the charge-discharge voltage plateau is 3.95V).
  • the battery prepared by mixing the above three materials in an appropriate ratio has a charge-discharge plateau in both high SOC state and low SOC state (see Figure 2), and in high SOC state, LMFP and ternary materials can cooperate to discharge , the battery polarization is small, the battery can work at a large rate, and the discharge power is large, but the actual discharge current endured by the respective materials is small.
  • the three can work together.
  • the actual charging current of the respective materials is small, and it is not easy to precipitate lithium due to overcharge; in the low SOC state, LFP and LMFP can be charged and discharged cooperatively, the battery polarization is small, and the discharge power of the battery is large, which is helpful for power vehicles. Quickly reach a predetermined speed at startup.
  • LMFP, LFP and ternary materials are mixed in an appropriate proportion as the positive electrode active material, and the above-mentioned parameter ⁇ is controlled based on the relationship between the specific capacity and efficiency of the positive and negative electrode active materials.
  • ⁇ in a certain range can make the battery have higher average voltage and specific capacity at the same time, which is beneficial to improve its energy density, reduce the risk of lithium precipitation when the battery is charged in a high SOC state, and improve the discharge power in a low SOC state.
  • ⁇ (M 1 ⁇ 1 ⁇ A 1 +M 2 ⁇ 2 ⁇ A 2 +M 3 ⁇ 3 ⁇ A 3 ) ⁇ b ⁇ c/(a ⁇ A 3 ⁇ 1000), and satisfy: 0.45 ⁇ 1.55;
  • a is the residual alkali content of the ternary material
  • b is the liquid injection coefficient of the lithium ion battery, in g/Ah
  • c is the residual water content in the electrolyte of the assembled lithium ion battery The theoretical value of ; the a and c are in ppm.
  • the parameter a can be obtained by testing the ternary materials used before assembling the lithium-ion battery.
  • the parameter b is a parameter determined when designing the battery, and c is a theoretical value.
  • the residual water content c in the electrolyte is usually between 200ppm and 400ppm.
  • the injection coefficient b is the ratio of the injection volume of the electrolyte in the battery to the designed discharge capacity of the battery.
  • the quality of the electrolyte in the battery can be determined when the battery capacity is determined.
  • the theoretical value (in g) of the water content in the electrolyte solution can be obtained through c, and the HF quality converted from water can be further determined.
  • the b is 2.9 g/Ah to 3.8 g/Ah.
  • the above-mentioned parameter ⁇ can represent the suppressed situation of HF in the battery electrolyte.
  • the ternary materials can preferentially consume the residual water in the battery electrolyte due to their good water absorption properties, and reduce the content of HF in the electrolyte.
  • the residual alkali content on the surface of the ternary material and the HF content in the electrolyte meet a certain relationship (ie, 0.45 ⁇ 1.55), the HF content in the electrolyte can be greatly reduced, which can significantly reduce the solubility of the LFP material.
  • the dissolved iron and manganese of iron and LMFP materials are beneficial to the better stability of the structure of these two materials, thereby improving the cycle performance of the battery and having a longer cycle life.
  • the value range of ⁇ is: 0.5 ⁇ 1.45.
  • the A 2 is 2-5 times the A 1 . At this time, it can be ensured that the above-mentioned lithium-ion battery has better charging and discharging power and safety performance in different SOC states. In some embodiments of the present disclosure, the A 2 is 2.4-3.5 times the A 1 .
  • the A 1 ranges from 10% to 25%. In still other embodiments of the present disclosure, the A 1 ranges from 15% to 25%. In other embodiments of the present disclosure, The A1 is 15 %-22%. In some embodiments of the present disclosure, the A 2 ranges from 45% to 80%. In still other embodiments of the present disclosure, the A 2 ranges from 45% to 75%. In other embodiments of the present disclosure, The A2 is 50%-75%. In some embodiments of the present disclosure, the A 3 ranges from 10% to 40%. In still other embodiments of the present disclosure, the A 3 ranges from 10% to 30%. In other embodiments of the present disclosure, The A3 is 10%-25%.
  • the ratio of X to Y is in the range of 1.71-1.89. This can not only avoid the lithium precipitation of the negative electrode sheet during the charging process, but also help the capacity of the positive electrode active material to be exerted, and help to improve the energy density of the battery.
  • X/Y is 1.73, 1.82, or 1.87, and the like.
  • the general structural formula of the ternary material is LiNi x Co y M z
  • M is at least one of Mn, Al, Zr, Ti, Y, Sr, W, and the like.
  • y satisfies: 0.01 ⁇ y ⁇ 0.33
  • z satisfies: 0.01 ⁇ z ⁇ 0.33.
  • the value range of x is: 0.70 ⁇ x ⁇ 0.98.
  • the ternary material can also be called “high nickel ternary material", which has good water absorption, high specific capacity and good rate performance, and is in the range of 4.1-4.15
  • the value range of x is: 0.80 ⁇ x ⁇ 0.90
  • the value range of x is: 0.83 ⁇ x ⁇ 0.88.
  • the nickel element in the ternary material is alkaline and easily absorbs moisture and carbon dioxide when exposed to the air, and reacts with the surface lithium to generate lithium hydroxide (LiOH) and lithium carbonate (Li 2 CO 3 ).
  • the residual alkali content of the ternary material specifically refers to the percentage of the measured mass of LiOH and Li 2 CO 3 to the total mass of the ternary material before the battery is assembled. In some embodiments of the present disclosure, the a ranges from 500ppm to 1500ppm.
  • the molar amount of manganese accounts for 0.75-0.9 of the sum of the molar amounts of ferromanganese. That is, the general structural formula of lithium iron manganese phosphate can be written as LiMn k Fe 1-k PO 4 , where 0.75 ⁇ k ⁇ 0.9.
  • the mole proportion of manganese element is relatively large, which makes the lithium iron manganese phosphate material have a longer charging voltage platform of 4.05-4.1V, which is more conducive to reducing the risk of lithium precipitation when the battery is charged at a high SOC and a large rate.
  • the particle size D50 of the ternary material is 4 ⁇ m-6 ⁇ m, for example, 4 ⁇ m-5 ⁇ m.
  • the ternary material is a single-crystal-like material, and its structural stability is higher than that of the ternary material in an agglomerated state.
  • the particle size D50 of the lithium iron phosphate material is 0.8 ⁇ m-1.3 ⁇ m, for example, 0.8 ⁇ m-1.2 ⁇ m.
  • the particle size D50 of the lithium iron manganese phosphate material is 10 ⁇ m-15 ⁇ m.
  • the surface of the lithium iron phosphate or lithium iron phosphate material also has a carbon coating layer to improve the electrical conductivity thereof. Further, the carbon content in the lithium iron phosphate or lithium iron phosphate material is 0.8wt%-1.2wt%.
  • the positive electrode material layer and the negative electrode material layer further include a conductive agent and a binder.
  • the above-mentioned positive electrode material layer can be formed by coating and drying a positive electrode slurry comprising the above-mentioned positive electrode active material, a conductive agent, a binder and a solvent.
  • the binder and the solvent can be mixed first, and after fully stirring, the conductive agent is added, and after stirring, the above-mentioned positive electrode active material is added, and the mixture is sieved after stirring.
  • the positive active material added can be directly a mixture of the above-mentioned LMFP, LFP and ternary materials, or these three materials can be added in batches.
  • the mass ratio of the positive electrode active material in the positive electrode material layer is 95%-97%. In still other embodiments of the present disclosure, the mass ratio of the graphite in the negative electrode material layer is 95%-98%.
  • the above-mentioned positive electrode active material can make the maximum compaction density of the positive electrode sheet in the range of 2.7g/cm 3 -2.8g/cm 3 .
  • the conductive agent and the binder are conventional choices in the battery field.
  • at least one of carbon nanotubes, carbon fibers, carbon black (eg, acetylene black, ketjen black), furnace black, and graphene may be used as the conductive agent, but it is not limited thereto.
  • the conductive agent includes three kinds of carbon nanotubes, carbon black and graphene, and the conductive agent of the three dimensions can make the positive electrode material layer have better conductivity.
  • the mass ratio of carbon nanotubes, carbon black and graphene may be 6:5:2.
  • the binder can be selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), styrene butadiene rubber (SBR), polyacrylonitrile (PAN), polyimide (PI)
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PVA polyvinyl alcohol
  • SBR styrene butadiene rubber
  • PAN polyacrylonitrile
  • PI polyimide
  • PAA polyacrylic acid
  • PAA polyacrylate
  • polyolefin such as polyethylene, polypropylene, polystyrene
  • CMC carboxymethyl cellulose
  • PVDF can refer to a copolymer obtained by copolymerizing vinylidene fluoride and an olefin compound containing a polar group
  • the polar group includes at least one of a carboxyl group, an epoxy group, a hydroxyl group and a sulfonic acid group.
  • the presence of the clusters can enhance the peel strength between the positive electrode material layer or the negative electrode material layer and the current collector.
  • the positive electrode current collector and the negative electrode current collector can be independently selected from metal foils or alloy foils.
  • the metal foil includes copper, titanium, aluminum, platinum, iridium, ruthenium, nickel, tungsten, tantalum, gold or silver foil
  • the alloy foil includes stainless steel, or copper, titanium, aluminum, platinum, iridium, An alloy of at least one element of ruthenium, nickel, tungsten, tantalum, gold and silver.
  • the alloy foil material has the above-mentioned elements as the main components.
  • the metal foil may further include doping elements, including but not limited to one of platinum, ruthenium, iron, cobalt, gold, copper, zinc, aluminum, magnesium, palladium, rhodium, silver, and tungsten or more.
  • the positive electrode current collector and the negative electrode current collector can be etched or roughened to form a secondary structure, so as to facilitate effective contact with the electrode material layer.
  • aluminum foil is usually used for the positive electrode current collector
  • copper foil is usually used for the negative electrode current collector.
  • Embodiments of the present disclosure also provide a powered vehicle, where the powered vehicle includes the above-mentioned lithium-ion battery. Due to the use of the above-mentioned lithium-ion battery, the power vehicle can be fully charged quickly when being charged on the charging pile, and can quickly reach a high starting speed when starting, and the battery has strong endurance and high safety.
  • the LMFP material used in the embodiments of the present disclosure is LiMn 0.8 Fe 0.2 PO 4 , the particle size D50 of which is 10-15 ⁇ m, the first charging specific capacity M 1 is 160 mAh/g, and the first efficiency ⁇ 1 is 96%;
  • the diameter D50 is 0.8-1.2 ⁇ m, the first charge specific capacity M 2 is 162 mAh/g, and the first efficiency ⁇ 2 is 99%.
  • the ternary material is a high-nickel ternary-type single crystal material with a general structural formula of LiNi 083 Co 0.12 Mn 0.05 , a particle size D50 of 4-5 ⁇ m, a first charge specific capacity M 3 of 238mAh/g, and a first efficiency ⁇ 3 of 86%, the residual alkali content a is 700ppm.
  • the first discharge specific capacity M 4 of graphite is 355 mAh/g, and the first efficiency ⁇ 4 is 95%.
  • the liquid injection coefficient b of the battery to be assembled is 3.1 g/Ah, and the theoretical value of the residual water content c in the electrolyte after the battery is assembled is designed to be 200 ppm.
  • the LMFP material, the LFP material and the ternary material were mixed according to the mixing ratios A 1 , A 2 and A 3 provided in Table 1, respectively, to obtain the positive electrode active materials of each embodiment, and the positive electrode active materials were controlled according to the table 1.
  • the ratio between the amount of dressing X on the positive electrode sheet and the amount of graphite dressing Y on the negative electrode sheet is determined according to the above formulas ⁇ , ⁇ , ⁇ , and the relevant experimental parameters are summarized in Table 1.
  • the preparation of the positive electrode sheet the organic solvent NMP and the binder PVDF are added to the mixer, and after stirring for 1 h, a conductive agent (specifically carbon tube, carbon black and graphene in a mass ratio of 6:5:2 is added to it). mixture), stirred for 30 min, then added the positive active materials of each example or comparative example respectively, stirred for 3 h, and after sieving, obtained the positive electrode slurry of each example and comparative example.
  • the mixing mass ratio of the positive electrode active material, the conductive agent, the binder PVDF, and the organic solvent NMP is 100:2:2:30.
  • the positive electrode slurries of each example and comparative example were respectively coated on both sides of the aluminum foil, and after removing NMP by high temperature baking, a positive electrode material layer was formed on the aluminum foil, and then rolled and slitted to obtain double-sided surfaces.
  • the compaction density of the pole piece can be calculated according to the areal density and thickness of the double-sided pole piece, and the results are summarized in Table 2.
  • the positive electrode slurries of the examples and comparative examples were respectively coated on one surface of the aluminum foil. After removing NMP by high temperature baking, a positive electrode material layer was formed on the aluminum foil, and then rolled and slitted. , a single-sided positive electrode sheet with a single-sided density of 2.0 g/dm 2 was obtained.
  • negative electrode sheet graphite, conductive carbon black Supper P, binder SBR, binder CMC, and water are mixed in a mass ratio of 100:1.0:2.5:1.1:105 to obtain a negative electrode slurry; the negative electrode slurry is coated with Covered on both sides of the copper foil, after baking at high temperature to remove water, a negative electrode material layer was formed on the copper foil, and then rolled and cut to obtain an areal density of 2.1g/dm 2 and a compaction density of 1.60g /cm 3 of double-sided negative electrode sheets.
  • Assembly of the battery Take the double-sided positive electrode sheets of each example and the comparative example and the above-mentioned double-sided negative electrode sheets with an areal density of 2.1 g/dm 2 ; use PP film as a separator to assemble a 053450 full battery.
  • the trigger temperature of the thermal runaway of the positive electrode material of the coin-type battery of each embodiment and the comparative example was tested, and the capacity of the full battery of each embodiment and the comparative example after being cycled at 45°C for 2000 weeks was tested.
  • the retention rate and the content of Fe and Mn eluted in the negative electrode are summarized in Table 2.
  • the test method for the trigger temperature of the thermal runaway of the positive electrode material is as follows: take the button batteries of each embodiment and the comparative example, and first fully charge each button battery (the specific method is: first charge with a constant current of 0.1C to a cut-off voltage of 4.2V, then charge at a constant voltage of 4.2V, the cut-off current is 0.05C), so that the positive electrode sheet is in a state of complete delithiation, then disassemble the button battery, take out the positive electrode sheet, and put the positive electrode material and electrolyte on the positive electrode sheet according to a certain quality. After mixing, it was placed in a high-temperature crucible, heated at a heating rate of 5 °C/min, and its thermogram was measured by differential scanning calorimeter (DSC) to observe the trigger temperature of thermal runaway of the positive electrode material.
  • DSC differential scanning calorimeter
  • the test method for the capacity retention rate of 2000 cycles at 45°C is as follows: at 45°C, the full cells of each example and comparative example are first charged with a constant current of 1C to a voltage of 4.1V, and then charged with a constant voltage of 4.1V.
  • the cut-off current is 0.05C; then the constant current is discharged at 1C until the voltage is 2.5V, and after 2000 cycles of charge and discharge, the ratio of the discharge capacity of the battery in the 2000th cycle to the discharge capacity of the first cycle is calculated, and this ratio is calculated.
  • the relationship between the discharge cut-off voltage and the discharge current is fitted; then according to the discharge cut-off voltage V 0 (specifically 2.5V) of the battery we set, we calculate the discharge cut-off voltage V 0 (specifically 2.5V) under a certain discharge time.
  • the current I 0 required to discharge to the set cut-off voltage V 0 , the discharge peak power P 0 V 0 *I 0 .
  • the test method for M 1 and ⁇ 1 of the LMFP material mentioned above is: prepare an LMFP positive electrode sheet with a single-sided density of 2.0 g/dm 2 in the above-mentioned manner (the positive electrode active material only contains LMFP) , the compaction density of the positive electrode sheet is about 2.5 g/cm 3 .
  • the LMFP positive electrode sheet, metal lithium sheet, separator and a certain quality of electrolyte were assembled into a CR2025 button battery in a glove box. Place the button battery for about 4 hours, so that the pole pieces are fully soaked in the electrolyte.
  • the coin cell was charged with constant current at 0.1C to a voltage of 4.3V, then charged with a constant voltage of 4.3V until the cut-off current was 0.01C, and then discharged with a constant current of 0.1C to a voltage of 2.0V.
  • the ratio of the discharge capacity and the charge capacity during the first cycle is recorded as the first efficiency ⁇ 1
  • the ratio of the charge capacity during the first cycle to the mass of the LMFP active material on the pole piece is taken as the first charge specific capacity M 1 of the LMFP material. .
  • the test method for M 2 and ⁇ 2 of the above-mentioned LFP material is as follows: prepare an LFP positive electrode sheet (the positive electrode active material only contains LFP) with a single-sided areal density of 2.0 g/dm 2 in the above-mentioned manner, and the compacted density of the positive electrode sheet is 2.6 g/dm . g/cm 3 or so.
  • the LFP positive electrode sheet, metal lithium sheet, separator and a certain quality of electrolyte were assembled into a CR2025 button battery in a glove box. Place the button battery for about 4 hours, and let the pole piece fully soak in the electrolyte.
  • the coin cell was charged with constant current at 0.1C to a voltage of 3.8V, then charged with a constant voltage of 3.8V until the cut-off current was 0.01C, and then discharged with a constant current of 0.1C to a voltage of 2.0V.
  • the ratio of the discharge capacity and the charge capacity during the first cycle is recorded as the first efficiency ⁇ 2
  • the ratio of the charge capacity during the first cycle to the mass of the LFP active material on the pole piece is taken as the first charge specific capacity M 2 of the LFP material .
  • the test method for M 3 and ⁇ 3 of the above-mentioned ternary material is: prepare a ternary positive electrode sheet with a single-sided areal density of 2.0 g/dm 2 in the above-mentioned manner, and the compaction density of the positive electrode sheet is about 3.5 g/cm 3 ,
  • the positive active material of the positive electrode sheet only contains the ternary material LiNi 083 Co 0.12 Mn 0.05 .
  • the ternary positive electrode sheet, lithium sheet, separator and electrolyte of a certain quality were assembled into a CR2025 button battery in a glove box. Place the button battery for about 4 hours, so that the pole pieces are fully soaked in the electrolyte.
  • the button battery is charged at 0.1C with constant current to 4.3V, charged with constant voltage of 4.3V until the cut-off current is 0.01C, and discharged with constant current of 0.1C to 3.0V.
  • the ratio of the discharge capacity and the charge capacity in the first cycle is recorded as the first efficiency ⁇ 3
  • the ratio of the charge capacity in the first cycle and the mass of the active material on the pole piece is recorded as the first charge ratio of the high nickel ternary material. capacity M 3 .
  • the testing method for M 4 and ⁇ 4 of the above-mentioned graphite is as follows: prepare a graphite pole piece with a single surface density of 1.05 g/dm 2 in the above-mentioned manner, and the compacted density of the graphite pole piece is about 1.60 g/cm 3 .
  • Graphite pole pieces, lithium pieces, separators and a certain quality of electrolyte were assembled into a CR2025 button battery in a glove box. Place the button battery for about 4 hours, and let the pole piece fully soak in the electrolyte.
  • Constant current discharge 0.1C to 0.005V (1) Constant current discharge 0.1C to 0.005V; (2) Constant current discharge 0.09C, 0.08C...0.02C to 0.001V; (3) Set aside for 15min; (4) Constant current charge 0.1C to 1.5 V; (5) set aside for 15min.
  • the ratio of the charge capacity and discharge capacity during the first cycle is recorded as the first efficiency ⁇ 4
  • the ratio of the discharge capacity in the first cycle to the mass of the active material on the pole piece is recorded as the first discharge specific capacity M 4 of the graphite material .
  • Comparative Example 2 LMFP and ternary materials are mixed. Without the participation of LFP materials, the discharge power in the low SOC state is low, only 300W/g. At the same time, the addition ratio of ternary materials is too large. The problem occurred in Example 1; and the cycle performance of LMFP is worse than that of LFP material. The capacity retention rate of the full battery of Comparative Example 2 at 45°C for 2000 cycles is lower than that of Comparative Example 1, only 70%.
  • Comparative Example 3 two materials, LMFP and LFP, were mixed without the participation of ternary materials. Due to the lack of ternary materials to suppress the presence of HF in the electrolyte to further suppress the dissolution of Mn and Fe, the battery of Comparative Example 3 had the worst cycle performance, with a capacity retention rate as low as 60% at 45°C for 2000 cycles.
  • Comparative Example 4 although three kinds of positive active materials are mixed, the mixing ratio does not satisfy the ranges of 1.03 ⁇ 1.15 and 0.55 ⁇ 1.5 required by the present disclosure.
  • the battery of Comparative Example 4 has lower charging power in high SOC state and lower discharging power in low SOC state; at the same time, due to the excessive addition of ternary materials, its safety performance and cycle performance will be reduced to varying degrees.

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Abstract

公开了一种锂离子电池及动力车辆，锂离子电池包括正极片、负极片、电解液及隔膜，正极片包括正极集流体和设置在正极集流体上的正极材料层，负极片包括负极集流体和设置在负极集流体上的负极材料层，负极材料层中的负极活性材料为石墨，正极材料层包括由磷酸锰铁锂材料、磷酸铁锂材料和三元材料构成的正极活性材料，磷酸锰铁锂材料、磷酸铁锂材料和三元材料在正极活性材料中的质量占比分别为A 1、A 2和A 3，且A 1+A 2+A 3＝1；定义：α＝(M 4×η 4×Y)/[(M 1×η 1×A 1+M 2×η 2×A 2+M 3×η 3×A 3)×X]，β＝[M 1×(1-η 1)×A 1+M 2×(1-η 2)×A 2+M 3×(1-η 3)×A 3]×X/[M 4×(1-η 4)×Y]，且满足以下条件：1.03≤α≤1.15，0.55≤β≤1.5，X为正极活性材料在正极片上的敷料量，Y为石墨在所述负极片上的敷料量；其中，M 1、M 2、M 3、M 4的单位均为mAh/g；X、Y的单位为g。

Description

锂离子电池及动力车辆
优先权信息
本公开请求于2021年03月25日向中国国家知识产权局提交的、专利申请号为202110320984.1、公开名称为“一种锂离子电池及动力车辆”的中国专利公开的优先权，并且其全部内容通过引用结合在本公开中。
技术领域
本公开涉及电池技术领域，具体涉及一种锂离子电池及动力车辆。
背景技术
锂离子电池是新一代的绿色高能电池，在电子设备、汽车、航空航天等领域广泛应用。作为锂离子电池重要的组成部分，正极材料的选择直接影响锂离子电池的性能，而将多种正极材料混用是电池领域常用的手段之一。
现有的正极材料的混合使用主要有：磷酸铁锂材料(LFP)和三元材料混用；磷酸锰铁锂材料(LMFP)和三元材料混用；锰酸锂和三元材料混用等。但前一种混用方案，会使电池在高SOC(state of charge，负电状态)下进行大倍率充电时有析锂风险，降低电池的安全性；而后两种混用方案虽然能在一定程度上缓解电池在大倍率充电下的析锂风险，但在低SOC下放电时，很快达到截止电压，放电功率较低。此外，混用多种正极材料的锂电池的正极比容量低，不利于电池能量密度的提高。
公开内容
鉴于此，本公开通过将LMFP、LFP与三元材料按适量比例混用，并控制三者的首次充电容量、首次效率等满足一定的要求，可使由它们制得的锂离子电池在高SOC态充电时不易析锂、低SOC态放电时功率较大，且能充分发挥各材料的比容量，并具有良好的循环稳定性。
第一方面，本公开提供了一种锂离子电池，包括正极片、负极片、电解液及位于所述正极片与负极片之间的隔膜，其中，所述正极片包括正极集流体和设置在所述正极集流体上的正极材料层，所述负极片包括负极集流体和设置在所述负极集流体上的负极材料层，所述负极材料层中的负极活性材料为石墨，所述正极材料层包括由磷酸锰铁锂材料、磷酸铁锂材料和三元材料构成的正极活性材料；其中，所述磷酸锰铁锂材料、磷酸铁锂材料和三元材料在所述正极活性材料中的质量占比分别为A 1、A 2和A 3，且A 1+A 2+A 3＝1；
定义：α＝(M 4×η 4×Y)/[(M 1×η 1×A 1+M 2×η 2×A 2+M 3×η 3×A 3)×X]，
β＝[M 1×(1-η 1)×A 1+M 2×(1-η 2)×A 2+M 3×(1-η 3)×A 3]×X/[M 4×(1-η 4)×Y]，
且满足以下条件：1.03≤α≤1.15，0.55≤β≤1.5；
其中，M 1、η 1分别为所述磷酸锰铁锂材料的首次充电比容量和首次效率，M 2、η 2分别为所述磷酸铁锂材料的首次充电比容量和首次效率，M 3、η 3分别为所述三元材料的首次充电比容量和首次效率，M 4、η 4分别为所述石墨的首次放电比容量和首次效率，X为所述正极活性材料在所述正极片上的敷料量，Y为所述石墨在所述负极片上的敷料量；其中，所述M 1、M 2、M 3、M 4的单位均为mAh/g；所述X、Y的单位均为g。
本公开中，通过将LMFP、LFP和三元材料混合用作正极活性材料，并调节三者的掺混比例，并从正负极活性材料的比容量、首次效率等电池运行角度等共同控制上述参数α、β在一定范围，可以较好地平衡各种材料的充放电特性，使该正极活性材料在高SOC态和低SOC态下均存在较高的充放电平台，进而使电池在高SOC态充电时不易析锂、低SOC态放电时功率较大，且该正极活性材料具有较好的压实密度，并可发挥出较高的比容量，利于提升锂离子电池的能量密度。因此，该锂离子电池可以较好地兼顾良好的倍率和功率性能及较高的能量密度等。
本公开一些实施方式中，还定义：γ＝(M 1×η 1×A 1+M 2×η 2×A 2+M 3×η 3×A 3)×b×c/(a×A 3×1000)，且γ满足：0.45≤γ≤1.55；
其中，a为所述三元材料的残碱含量，b为所述锂离子电池的注液系数，单位为g/Ah，c为装配后的所述锂离子电池的电解液中的残留水含量的理论值；所述a和c以ppm计。
此时，所述正极活性材料中LFP、LMFP的结构稳定性提高，不易发生溶铁/溶锰，利于提升电池的循环性能。即，该锂离子电池还可以较好地兼顾良好的倍率和功率性能、较高的能量密度、良好的循环性能、高安全性等性能。
本公开一些实施方式中，所述b为在2.9-3.8之间的常数，所述c在200ppm-400ppm的范围内取值，所述a在500ppm-1500ppm的范围内取值。
本公开一些实施方式中，所述A 2是A 1的2-5倍。
本公开一些实施方式中，所述A 1在10％-25％的范围内取值。
本公开一些实施方式中，所述X与Y的比值在1.71-1.89的范围内。
本公开一些实施方式中，所述三元材料的结构通式为LiNi xCo yM z，其中，所述M为第III副族至第V主族中的至少一种金属元素，0.33≤x≤0.98，0<y<1，0<z<1，且x+y+z＝1。
本公开一些实施方式中，所述磷酸锰铁锂材料中，锰的摩尔量占锰铁摩尔量之和的0.75-0.9。
本公开一些实施方式中，所述磷酸铁锂材料的粒径D50为0.8μm-1.3μm，所述磷酸锰铁 锂材料的粒径D50为10μm-15μm，所述三元材料的粒径D50为4μm-6μm。
第二方面，本公开提供了一种动力车辆，该动力车辆包括本公开第一方面所述的锂离子电池。
本公开实施例的优点将会在下面的说明书中部分阐明，一部分根据说明书是显而易见的，或者可以通过本公开实施例的实施而获知。
附图说明
此处所说明的附图用来提供对本公开的进一步理解，构成本公开的一部分，本公开的示意性实施例及其说明用于解释本公开，并不构成对本公开的不当限定。在附图中：
图1a为磷酸锰铁锂-石墨体系电池的充放电曲线；
图1b为磷酸铁锂-石墨体系电池的充放电曲线；
图1c为三元材料-石墨体系电池的充放电曲线；
图2为本公开实施例4中全电池的充放电曲线。
具体实施方式
以下所述是本发明的示例性实施方式，应当指出，对于本技术领域的普通技术人员来说，在不脱离本发明原理的前提下，还可以做出若干改进和润饰，这些改进和润饰也视为本发明的保护范围。
本公开实施例提供了一种锂离子电池，包括正极片、负极片、电解液及位于所述正极片与负极片之间的隔膜，其中，所述正极片包括正极集流体和设置在所述正极集流体上的正极材料层，所述负极片包括负极集流体和设置在所述负极集流体上的负极材料层，所述负极材料层中的负极活性材料为石墨，所述正极材料层包括由磷酸锰铁锂材料(LMFP)、磷酸铁锂材料(LFP)和三元材料构成的正极活性材料；其中，所述磷酸锰铁锂材料、磷酸铁锂材料和三元材料在所述正极活性材料中的质量占比分别为A 1、A 2和A 3，且A 1+A 2+A 3＝1；
定义：α＝(M 4×η 4×Y)/[(M 1×η 1×A 1+M 2×η 2×A 2+M 3×η 3×A 3)×X]，
β＝[M 1×(1-η 1)×A 1+M 2×(1-η 2)×A 2+M 3×(1-η 3)×A 3]×X/[M 4×(1-η 4)×Y]，
且满足以下条件：1.03≤α≤1.15，0.55≤β≤1.5；
其中，M 1、η 1分别为所述磷酸锰铁锂材料的首次充电比容量和首次效率，M 2、η 2分别为所述磷酸铁锂材料的首次充电比容量和首次效率，M 3、η 3分别为所述三元材料的首次充电比容量和首次效率，M 4、η 4分别为所述石墨的首次放电比容量和首次效率，X为所述正极活性材料在所述正极片上的敷料量，Y为所述石墨在所述负极片上的敷料量；其中，所述M 1、M 2、M 3、M 4的单位均为mAh/g；所述X、Y的单位为g。
需要说明的是，上述M 1、M 2、M 3、M 4、η 1、η 2、η 3、η 4均可分别通过对单独的LMFP、LFP、三元或石墨材料制成的扣式电池测试得到。X、Y为在设计电池时就确定好的一参数。
上述α代表负极片的容量相对于正极片的容量的过剩比。若α值过低，则在充电过程中负极片上有析锂的风险；若α值过高，则负极片的敷料量过大，则负极片在形成SEI膜(固体电解质界面膜)时需要消耗更多的活性锂，不利于正极活性材料容量的发挥，会降低电池的能量密度。控制1.03≤α≤1.15，可使电池析锂风险较低的同时，还利于其正极活性材料的容量发挥。本公开一些实施方式中，1.05≤α≤1.12，在本公开再一些实施方式中，1.08≤α≤1.12。
上述β代表LMFP材料、LFP材料、石墨、三元材料这四者首次效率的平衡关系。三元材料的首次效率＜石墨的首次效率＜LMFP材料的首次效率＜LFP材料的首次效率，当负极为石墨，只采用LFP和/或LMFP材料作为正极活性材料时，LFP/LMFP材料因首效高造成的不可逆锂的损失少，不足以供石墨消耗形成SEI膜，所以石墨还会消耗电池体系中的其他活性锂，降低LFP/LMFP的比容量，进而造成电池能量密度变低；而三元材料因首效低，其留在负极中的较多不可逆锂足够负极形成SEI膜的消耗，当LFP/LMFP和三元材料混用时，相当于三元材料变相给LFP/LMFP补锂，可提高整体正极活性材料的比容量。综合考虑后，本公开控制β的取值范围为：0.55≤β≤1.5，这更有助于提升整体正极活性材料的比容量，利于电池能量密度的提高。
此外，当将LMFP、LFP和三元材料混用时，可利用三种材料的不同充放电特性，其中LMFP材料在高电压区间具有一定长度的放电平台(参见图1a，充放电电压平台为3.95V-4.0V)，有利于降低体系在高SOC态下大倍率充电时的析锂风险；LFP材料在低电压区间具有较长的充放电平台(参见图1b，充放电电压平台在3.2V左右)，有利于提升体系在低SOC态下的大功率放电性能；三元材料在整个电压区间的容量释放比较均衡(参见图1c)，更偏向于高电压区间的容量释放。因此，将上述三种材料按合适比例混合制得的电池，在高SOC态和低SOC态下都存在充放电平台(参见图2)，在高SOC态下，LMFP和三元材料可协同放电，电池极化小，电池可以在大倍率下工作，放电功率较大，但各自材料承受的实际放电电流较小，相应地，当电池在高SOC态下以大倍率充电时，三者可以协同充电，各自材料承受的实际充电电流较小，不易因过充而析锂；在低SOC态下，LFP和LMFP可协同充放电，电池极化小，电池的放电功率大，有助于动力车辆在启动时快速达到预定速度。
因此，本公开上述提供的锂离子电池中，将LMFP、LFP和三元材料三者按合适比例混合用作正极活性材料，并基于正负极活性材料的比容量、效率等关系控制上述参数α、β在一定范围，能使电池同时具有较高的平均电压和比容量，利于提升其能量密度，并可降低电池在高SOC态充电时的析锂风险、提高低SOC态下的放电功率。
本公开一些实施方式中，还定义：γ＝(M 1×η 1×A 1+M 2×η 2×A 2+M 3×η 3×A 3)×b×c/(a×A 3×1000)，且满足：0.45≤γ≤1.55；
其中，a为所述三元材料的残碱含量，b为所述锂离子电池的注液系数，单位为g/Ah，c为装配后的所述锂离子电池的电解液中的残留水含量的理论值；所述a和c以ppm计。
这里，参数a可通过在装配该锂离子电池之前对所用三元材料进行测试得到。参数b为在设计电池时就确定好的一参数，c为一理论值，对通常的装配合格的电池来说，其电解液中的残留水含量c通常在200ppm-400ppm之间。其中，注液系数b为电池中电解液的注液量与电池的设计放电容量的比值，当注液系数b确定时，在电池容量确定的情况下，就可确定电池中电解液的质量，进而可通过c得知电解液中的所含水质量的理论值(以g计)，进一步可确定由水转化成的HF质量。在本公开的一些实施方式中，所述b为2.9g/Ah-3.8g/Ah。
上述参数γ可以代表电池电解液中HF的被抑制情况。LFP、LMFP和三元材料混用时，三元材料因具有较好的吸水性能而可优先消耗掉电池电解液中残留的水分，降低电解液中HF的含量。当三元材料表面的残碱含量与电解液中的HF含量满足一定的关系时(即0.45≤γ≤1.55)，可以使电解液中的HF含量被大大降低，进而可明显降低LFP材料的溶铁、LMFP材料的溶铁锰，利于这两种材料的结构较好地保持稳定，从而可提高电池的循环性能，具有较长的循环寿命。本公开一些实施方式中，所述γ的取值范围为：0.5≤γ≤1.45。
本公开一些实施方式中，所述A 2是A 1的2-5倍。此时，可以保证上述锂离子电池在不同SOC态下的充放电功率和安全性能更好。在本公开一些实施方式中，所述A 2是A 1的2.4-3.5倍。
本公开一些实施方式中，所述A 1在10％-25％的范围内取值，本公开再一些实施方式中，所述A 1为15％-25％，本公开另一些实施方式中，所述A 1为15％-22％。本公开一些实施方式中，所述A 2在45％-80％的范围内取值，本公开再一些实施方式中，所述A 2为45％-75％，本公开另一些实施方式中，所述A 2为50％-75％。本公开一些实施方式中，所述A 3在10％-40％的范围内取值，本公开再一些实施方式中，所述A 3为10％-30％，本公开另一些实施方式中，所述A 3为10％-25％。
本公开一些实施方式中，，所述X与Y的比值(X/Y)在1.71-1.89的范围内。这样既可以避免负极片在充电过程中析锂，又利于正极活性材料的容量发挥，助于提升电池的能量密度。在本公开再一些实施例中，X/Y为1.73、1.82或1.87等。
本公开中，三元材料的结构通式为LiNi xCo yM z，M为第III副族至第V主族中的至少一种金属元素，0.33≤x≤0.98，0<y<1，0<z<1，且x+y+z＝1。例如，M为Mn、Al、Zr、Ti、Y、Sr和W等中的至少一种。本公开一些实施方式中，y满足：0.01≤y≤0.33，z满足：0.01≤z≤0.33。
本公开一些实施方式中，x的取值范围是：0.70≤x≤0.98。此外，x的值较高时，该三元 材料也可称为“高镍三元材料”，其吸水性较好，且具有较高的比容量和较好的倍率性能，并在4.1-4.15V左右存在H2-H3相变，存在明显的充放电平台，有利于LMFP和高镍三元材料之间的协同放电。本公开再一些实施方式中，x的取值范围是：0.80≤x≤0.90，本公开又一些实施方式中，x的取值范围是：0.83≤x≤0.88。
三元材料中的镍元素呈碱性，暴露在空气中易吸收水分和二氧化碳，与表层锂反应生成氢氧化锂(LiOH)和碳酸锂(Li 2CO 3)。其中，三元材料的残碱含量具体是指在电池装配之前，测得LiOH和Li 2CO 3的质量占三元材料总质量的百分比。本公开一些实施方式中，所述a在500ppm-1500ppm的范围内取值。
本公开一些实施方式中，所述磷酸锰铁锂材料中，锰的摩尔量占锰铁摩尔量之和的0.75-0.9。即，磷酸锰铁锂的结构通式可写成LiMn kFe 1-kPO 4，其中，0.75≤k≤0.9。此时，锰元素的摩尔占比较大，使得磷酸锰铁锂材料在4.05-4.1V的充电电压平台较长，更有利于降低电池在高SOC以大倍率充电时的析锂风险。
本公开一些实施方式中，所述三元材料的粒径D50为4μm-6μm，例如为4μm-5μm。本公开再一些实施方式中，所述三元材料为类单晶材料，其结构稳定性较团聚体态的三元材料高。
本公开一些实施方式中，所述磷酸铁锂材料的粒径D50为0.8μm-1.3μm，例如为0.8μm-1.2μm。
本公开一些实施方式中，所述磷酸锰铁锂材料的粒径D50为10μm-15μm。
进一步地，所述磷酸铁锂或磷酸铁锂材料的表面还具有碳包覆层，以使其导电性提高。进一步地，所述磷酸铁锂或磷酸铁锂材料中的碳含量为0.8wt％-1.2wt％。
其中，所述正极材料层、所述负极材料层还包括导电剂和粘结剂。举例来说，上述正极材料层可以通过包含上述正极活性材料、导电剂、粘结剂和溶剂的正极浆料经涂覆、干燥而成。在配制该正极浆料时，可以先将粘结剂与溶剂混合，充分搅拌后，再加入导电剂，经搅拌后再加入上述正极活性材料，搅拌后过筛。所加入的正极活性材料可以直接是上述LMFP、LFP和三元材料的混合物，也可以将这三种材料分批加入。
本公开一些实施方式中，所述正极活性材料在所述正极材料层中的质量占比为95％-97％。本公开再一些实施方式中，所述石墨在所述负极材料层中的质量占比为95％-98％。
本公开一些实施方式中，上述正极活性材料可使所述正极片的最大压实密度在2.7g/cm 3-2.8g/cm 3。
其中，导电剂、粘结剂均为电池领域的常规选择。例如，导电剂可以采用碳纳米管、碳纤维、炭黑(如乙炔黑、科琴黑)、炉黑及石墨烯中的至少一种，但不限于此。本公开一些实施方式中，所述导电剂包括碳纳米管、炭黑以及石墨烯中的三种，三种维度的导电 剂可使正极材料层具有较好的导电性。进一步地，碳纳米管、炭黑以及石墨烯的质量比可以为6：5：2。
粘结剂可以选自聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、聚乙烯醇(PVA)、丁苯橡胶(SBR)、聚丙烯腈(PAN)、聚酰亚胺(PI)、聚丙烯酸(PAA)、聚丙烯酸酯、聚烯烃(如聚乙烯、聚丙烯、聚苯乙烯)、羧甲基纤维素钠(CMC)和海藻酸钠中的一种或多种。其中，PVDF可以指通过偏氟乙烯与含极性基团的烯烃类化合物共聚得到的共聚物，极性基团包括羧基、环氧基、羟基和磺酸基中的至少一种，极性基团的存在可以增强正极材料层或负极材料层与集流体之间的剥离强度。
其中，上述正极集流体及负极集流体可以独立地选自金属箔材或合金箔材。所述金属箔材包括铜、钛、铝、铂、铱、钌、镍、钨、钽、金或银箔材，所述合金箔材包括不锈钢、或含铜、钛、铝、铂、铱、钌、镍、钨、钽、金和银中至少一种元素的合金。
本公开一些实施方式中，所述合金箔材以上述这些元素为主体成分。所述金属箔材可进一步包含掺杂元素，所述掺杂元素包括但不限于铂、钌、铁、钴、金、铜、锌、铝、镁、钯、铑、银、钨中的一种或多种。上述正极集流体及负极集流体可被蚀刻处理或粗化处理，以形成次级结构，便于和电极材料层形成有效接触。一般地，正极集流体通常采用铝箔，负极集流体通常采用铜箔。
本公开实施例还提供了一种动力车辆，该动力车辆包括上述锂离子电池。由于采用了上述锂离子电池，该动力车辆在充电桩上充电时可以较快地充满电，在启动时可以快速达到较高的启动速度，且该电池的续航能力强、安全性高。
下面结合多个具体实施例对本公开实施例进行进一步的说明。
本公开实施例采用的LMFP材料为LiMn 0.8Fe 0.2PO 4，其粒径D50为10-15μm，首次充电比容量M 1为160mAh/g，首次效率η 1为96％；采用的LFP材料的粒径D50为0.8-1.2μm，首次充电比容量M 2为162mAh/g，首次效率η 2为99％。三元材料为高镍三元类单晶材料，其结构通式为LiNi 083Co 0.12Mn 0.05，粒径D50为4-5μm，其首次充电比容量M 3为238mAh/g，首次效率η 3为86％，残碱含量a为700ppm。石墨的首次放电比容量M 4为355mAh/g，首次效率η 4为95％。待装配的电池的注液系数b为3.1g/Ah，电池装配后电解液中的残留水含量c的理论值设计为200ppm。
正极活性材料的配制：
将LMFP材料、LFP材料与三元材料分别按表1提供的掺混比例A 1、A 2、A 3混合，得到各实施例的正极活性材料，并按表1所列来控制正极活性材料在正极片上的敷料量X与石墨在负极片上的敷料量Y之间的比值，根据上述公式确定述参数γ、α、β，相关实验参数 汇总在表1。
此外，为突出本公开技术方案的有益效果，还提供了如下表1所示的对比例1-4。
表1 各实施例及对比例的部分参数
Figure PCTCN2022082943-appb-000001
正极片的制备：将有机溶剂NMP与粘结剂PVDF加入到搅拌机中，搅拌1h后，再向其中加入导电剂(具体是碳管、炭黑与石墨烯按照质量比为6∶5∶2的混合物)，搅拌30min，再分别加入各实施例或对比例的正极活性材料，搅拌3h，过筛后，得到各实施例及对比例的正极浆料。其中，各正极浆料中，正极活性材料与导电剂、粘结剂PVDF、有机溶剂NMP的混合质量比为100∶2∶2∶30。
将各实施例及对比例的正极浆料分别涂覆在铝箔的两侧表面上，经高温烘烤去除NMP后，在铝箔上形成正极材料层，再经辊压、分切，得到双面面密度为4.0g/dm 2的双面正极片。可以根据双面极片的面密度和厚度，计算极片的压实密度，结果汇总在表2。
按类似的方式，将各实施例及对比例的正极浆料分别涂覆在铝箔的一侧表面上，经高温烘烤去除NMP后，在铝箔上形成正极材料层，再经辊压、分切，得到单面面密度为2.0g/dm 2的单面正极片。
负极片的制备：将石墨与导电炭黑Supper P、粘结剂SBR、粘结剂CMC、水按100：1.0：2.5：1.1：105的质量比混合，得到负极浆料；将负极浆料涂覆在铜箔的两侧表面上，经高温烘烤去除水后在铜箔上形成负极材料层，再经辊压、分切，得到面密度为2.1g/dm 2、压实密度为1.60g/cm 3的双面负极片。
电池的装配：取各实施例及对比例的双面正极片及上述面密度为2.1g/dm 2的双面负极片；以PP膜作隔膜，组装成053450全电池。
取各实施例及对比例的单面正极片，以金属锂片作为负极，用Celgard 2300微孔膜作隔膜，1.0mol/L LiPF 6的碳酸乙烯酯(EC)：碳酸二甲酯(DMC)＝1:1～5(体积比)的溶液作电解液，在手套箱中组装成CR2025扣式电池。
为对本公开的有益效果进行有力支持，测试各实施例及对比例的扣式电池的正极材料热失控的触发温度，测试各实施例及对比例的全电池在45℃下循环2000周后的容量保持率及在负极溶出的Fe、Mn含量，结果汇总在表2。
其中，正极材料热失控的触发温度的测试方法为：取各实施例及对比例的扣式电池，先将各扣式电池充满电(具体方式为：先以0.1C恒流充电至截止电压为4.2V，再以4.2V恒压充电，截止电流是0.05C)，使正极片处于完全脱锂状态，之后拆解扣式电池，取出正极片，将正极片上的正极材料与电解液按一定质量比混合后置于高温坩埚中，以5℃/min的升温速率升温，通过差示扫描量热仪(DSC)测试其热谱图，以观察正极材料热失控的触发温度。
45℃下循环2000周的容量保持率的测试方法为：在45℃下，将各实施例及对比例的全电池先以1C恒流充电至电压为4.1V，再以4.1V恒压充电，截止电流是0.05C；之后在1C下恒流放电至电压为2.5V，以此进行充放电循环2000周后，计算电池第2000圈的放电容量与第一圈的放电容量的比值，将此比值作为电池循环2000周后的容量保持率。
不同SOC下的充放电功率特性的测试方法为：
1、将各实施例及对比例的全电池以0.2C恒流充电至4.2V；搁置5min；0.2C恒流放电至2.5V，搁置5min；循环2次，记录第2次放电容量记为C 0，以此容量调SOC；
2、将各全电池以0.2C恒流充电至4.2V，搁置30min；以0.2C恒流放电至指定的SOC(具体是指全电池以0.2C恒流充电至4.2v时SOC的20％)，然后在不同放电电流下进行放电：
1)、以0.5C恒流放电30s，搁置5min，记录放电截止电压，再以0.2C恒流充电75s，搁置5min，以将SOC调回至为20％；
2)、1C恒流放电30s，搁置5min，记录放电截止电压，再以0.2C恒流充电150s，搁置5min，以将SOC调回至为20％；
3)、2C恒流放电30s，搁置5min，记录放电截止电压，再以0.2C恒流充电300s，搁置5min，以将SOC调回至为20％；
4)、3C恒流放电30s，搁置5min，记录放电截止电压，再以0.2C恒流充电450s，搁置5min，以将SOC调回至为20％；
5)、5C恒流放电30s，搁置5min，记录放电截止电压，再以0.2C恒流充电750s，搁置5min，以将SOC调回至为20％；
6)、7C恒流放电30s，搁置5min，记录放电截止电压，再以0.2C恒流充电1050s，搁置5min，以将SOC调回至为20％；
7)、10C恒流放电30s，搁置5min，记录放电截止电压，再以0.2C恒流充电1500s，搁置5min，以将SOC调回至为20％；
根据以上测试的7组数据，拟合出放电截止电压与放电电流之间的关系式；再根据我们设定的电池的放电截止电压V 0(具体是2.5V)，计算出在一定放电时间下放电至设定的截止电压V 0所需要的电流I 0，则放电峰值功率P 0＝V 0*I 0。
3、在室温下，将各全电池以0.2C恒流放电至2.5V，搁置30min，以0.2C恒流充电至指定的SOC(具体是全电池以0.2C恒流放电至2.5V时SOC的80％)，然后在不同充电电流下进行充电：
1)、0.5C恒流充电30s，搁置5min，记录充电截止电压，再以0.2C恒流放电75s，搁置5min，以将SOC调回至为80％；
2)、1C恒流充电30s，搁置5min，记录充电截止电压，再以0.2C恒流放电150s，搁置5min，以将SOC调回至为80％；
3)、2C恒流充电30s，搁置5min，记录充电截止电压，再以0.2C恒流放电300s，搁置5min，以将SOC调回至为80％；
4)、3C恒流充电30s，搁置5min，记录充电截止电压，再以0.2C恒流放电450s，搁置5min，以将SOC调回至为80％；
5)、5C恒流充电30s，搁置5min，记录充电截止电压，再以0.2C恒流放电750s，搁置5min，以将SOC调回至为80％；
根据以上测试的5组数据，拟合出充电截止电压与充电电流之间的关系式；再根据我们设定的电池的充电截止电压V 0’(具体是4.2V)，计算出在一定充电时间下充电至设定的截止电压V 0'所需要的电流I 0’，则充电峰值功率P 0’＝V 0’*I 0’。
此外，需要说明的是，上述提及的LMFP材料的M 1、η 1的测试方法为：按上述方式制备单面面密度为2.0g/dm 2的LMFP正极片(正极活性材料仅含LMFP)，该正极片的压实密度在2.5g/cm 3左右。将该LMFP正极片、金属锂片、隔膜以及一定质量的电解液在手套箱中装配成CR2025的扣式电池。将扣式电池放置4h左右，让极片在电解液中充分浸润。将扣式电池在0.1C下恒流充电至电压为4.3V，再以4.3V恒压充电至截止电流为0.01C，之后 以0.1C恒流放电至电压为2.0V。以首圈循环过程中的放电容量和充电容量的比值记为首次效率η 1，以首圈循环过程中充电容量与极片上LMFP活性材料的质量的比值作为该LMFP材料的首次充电比容量M 1。
上述LFP材料的M 2、η 2的测试方法为：按上述方式制备单面面密度为2.0g/dm 2的LFP正极片(正极活性材料仅含LFP)，该正极片的压实密度在2.6g/cm 3左右。将该LFP正极片、金属锂片、隔膜以及一定质量的电解液在手套箱中装配成CR2025的扣式电池。将扣式电池放置4h左右，让极片在电解液中充分浸润。将扣式电池在0.1C下恒流充电至电压为3.8V，再以3.8V恒压充电至截止电流为0.01C，之后以0.1C恒流放电至电压为2.0V。以首圈循环过程中的放电容量和充电容量的比值记为首次效率η 2，以首圈循环过程中充电容量与极片上LFP活性材料的质量的比值作为该LFP材料的首次充电比容量M 2。
上述三元材料的M 3、η 3的测试方法为：按上述方式制备单面面密度为2.0g/dm 2的三元正极片，该正极片的压实密度在3.5g/cm 3左右，该正极片的正极活性材料仅含三元材料LiNi 083Co 0.12Mn 0.05。将该三元正极片、锂片、隔膜以及一定质量的电解液在手套箱中装配成CR2025的扣式电池。将扣式电池放置4h左右，让极片在电解液中充分浸润。扣式电池在0.1C，恒流充电至4.3V，恒压4.3V充电至截止电流为0.01C，恒流0.1C放电至3.0V。以首圈循环过程中的放电容量和充电容量的比值记为首次效率η 3，以首圈循环中充电容量与极片上活性材料的质量，两者的比值记为高镍三元材料首次充电比容量M 3。
上述石墨的M 4、η 4的测试方法为：按上述方式制备单面面密度为1.05g/dm 2的石墨极片，该石墨极片的压实密度在1.60g/cm 3左右。将石墨极片、锂片、隔膜以及一定质量的电解液在手套箱中装配成CR2025的扣式电池。将扣式电池放置4h左右，让极片在电解液中充分浸润。将扣式电池(1)恒流放电0.1C到0.005V；(2)恒流放电0.09C，0.08C…0.02C到0.001V；(3)搁置15min；(4)恒流充电0.1C到1.5V；(5)搁置15min。以首圈循环过程中的充电容量和放电容量的比值记为首次效率η 4，以首圈循环中放电容量与极片上活性材料的质量，两者的比值记为石墨材料首次放电比容量M 4。
表2 各实施例及对比例的正极片及电池性能测试结果
Figure PCTCN2022082943-appb-000002
Figure PCTCN2022082943-appb-000003
由表1及表2可以获知，对比例1中是LFP与三元材料两者混合，没有LMFP的参与，其在高SOC态的充电功率较低，只有300W/g，同时三元材料的添加比例太多，达到65％，电池的安全性能大大降低，其热失控的出发温度降至250℃；同时电池整体的循环性能也有所降低。
对比例2中是LMFP与三元材料两者混合，没有LFP材料的参与，其在低SOC态的放电功率较低，只有300W/g，同时三元材料的添加比例太多，同样会存在对比例1中出现的问题；且LMFP比LFP材料的循环性能差，对比例2的全电池在45℃下循环2000次的容量保持率比对比例1还低，仅为70％。
对比例3中是LMFP和LFP两种材料混合，没有三元材料的参与。由于缺少三元材料来抑制电解液中HF的存在以进一步抑制Mn和Fe的溶出，因此，对比例3的电池的循环性能最差，其在45℃循环2000次容量保持率低至60％。
对比例4中虽然是三种正极活性材料的混合，但是其混合比例不满足本公开要求的1.03≤α≤1.15、0.55≤β≤1.5范围内。对比例4的电池在高SOC态的充电功率和低SOC态的放电功率均较低；同时由于三元材料的添加比例过多，其安全性能和循环性能都会有不同程度的降低。
由表2可以获知，当由LMFP材料、LFP材料与三元材料混合形成的正极活性材料中，三者的掺混比例同时使上述α在1.03-1.15、β在0.55-1.5时，电池在低SOC下的放电功率及高SOC下的充电功率均较大，低SOC下的放电功率可在1400W/g以上、高SOC下的充电功率可在600W/g以上，且正极片的压实密度较高、正极材料的结构稳定性高，电池的循环性能好、安全 性好。同时，当γ还在0.45-1.55的范围时，电池的综合性能更优异。
以上所述实施例仅表达了本公开的几种实施方式，其描述较为具体和详细，但并不能因此而理解为对本公开专利范围的限制。应当指出的是，对于本领域的普通技术人员来说，在不脱离本公开构思的前提下，还可以做出若干变形和改进，这些都属于本公开的保护范围。因此，本公开专利的保护范围应以所附权利要求为准。

Claims (10)

  1. 一种锂离子电池，包括正极片、负极片、电解液及位于所述正极片与所述负极片之间的隔膜，所述正极片包括正极集流体和设置在所述正极集流体上的正极材料层，所述负极片包括负极集流体和设置在所述负极集流体上的负极材料层，其中，所述负极材料层中的负极活性材料为石墨，所述正极材料层包括由磷酸锰铁锂材料、磷酸铁锂材料和三元材料构成的正极活性材料，所述磷酸锰铁锂材料、所述磷酸铁锂材料和所述三元材料在所述正极活性材料中的质量占比分别为A 1、A 2和A 3，且A 1+A 2+A 3＝1；
    定义：α＝(M 4×η 4×Y)/[(M 1×η 1×A 1+M 2×η 2×A 2+M 3×η 3×A 3)×X]，
    β＝[M 1×(1-η 1)×A 1+M 2×(1-η 2)×A 2+M 3×(1-η 3)×A 3]×X/[M 4×(1-η 4)×Y]，
    且满足以下条件：1.03≤α≤1.15，0.55≤β≤1.5；
    其中，M 1、η 1分别为所述磷酸锰铁锂材料的首次充电比容量和首次效率，M 2、η 2分别为所述磷酸铁锂材料的首次充电比容量和首次效率，M 3、η 3分别为所述三元材料的首次充电比容量和首次效率，M 4、η 4分别为所述石墨的首次放电比容量和首次效率，X为所述正极活性材料在所述正极片上的敷料量，Y为所述石墨在所述负极片上的敷料量；其中，所述M 1、M 2、M 3、M 4的单位均为mAh/g；所述X、Y的单位为g。
  2. 如权利要求1所述的锂离子电池，其中，还定义：γ＝(M 1×η 1×A 1+M 2×η 2×A 2+M 3×η 3×A 3)×b×c/(a×A 3×1000)，且满足：0.45≤γ≤1.55；
    其中，a为所述三元材料的残碱含量，b为所述锂离子电池的注液系数，单位为g/Ah，c为装配后的所述锂离子电池的电解液中的残留水含量的理论值；所述a和c以ppm计。
  3. 如权利要求1或2所述的锂离子电池，其中，所述A 2是A 1的2-5倍。
  4. 如权利要求1-3中任一项所述的锂离子电池，其中，所述A 1在10％-25％的范围内取值。
  5. 如权利要求1-4中任一项所述的锂离子电池，其中，所述X与Y的比值在1.71-1.89的范围内取值。
  6. 如权利要求1-5中任一项所述的锂离子电池，其中，所述b为在2.9-3.8之间的常数，所述c在200ppm-400ppm的范围内取值，所述a在500ppm-1500ppm的范围内取值。
  7. 如权利要求1-6中任一项所述的锂离子电池，其中，所述三元材料的结构通式为LiNi xCo yM z，其中，所述M为第III副族至第V主族中的至少一种金属元素，0.33≤x≤0.98，0<y<1，0<z<1，且x+y+z＝1。
  8. 如权利要求1-7中任一项所述的锂离子电池，其中，所述磷酸锰铁锂材料中，锰的摩尔量占锰铁摩尔量之和的0.75-0.9。
  9. 如权利要求1-8中任一项所述的锂离子电池，其中，所述磷酸铁锂材料的粒径D50为 0.8μm-1.3μm，所述磷酸锰铁锂材料的粒径D50为10μm-15μm，所述三元材料的粒径D50为4μm-6μm。
  10. 一种动力车辆，其中，所述动力车辆包括权利要求1-9任一项所述的锂离子电池。
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