WO2023138109A1 - 一种锂离子电池及用电装置 - Google Patents

一种锂离子电池及用电装置 Download PDF

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WO2023138109A1
WO2023138109A1 PCT/CN2022/124017 CN2022124017W WO2023138109A1 WO 2023138109 A1 WO2023138109 A1 WO 2023138109A1 CN 2022124017 W CN2022124017 W CN 2022124017W WO 2023138109 A1 WO2023138109 A1 WO 2023138109A1
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positive electrode
negative electrode
lithium
coating area
ion battery
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PCT/CN2022/124017
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English (en)
French (fr)
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张业琼
黄海旭
江柯成
张传健
刘双
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江苏正力新能电池技术有限公司
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Publication of WO2023138109A1 publication Critical patent/WO2023138109A1/zh

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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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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 invention relates to the field of lithium batteries, in particular to a lithium ion battery and an electrical device.
  • New energy vehicles refer to the use of unconventional vehicle fuels as power sources, mainly including the following four types: hybrid electric vehicles (HEV), pure electric vehicles (BEV, including solar vehicles), fuel cell electric vehicles (FCEV), other new energy (such as super capacitors, flywheels and other high-efficiency energy storage) vehicles, etc.
  • HEV hybrid electric vehicles
  • BEV pure electric vehicles
  • FCEV fuel cell electric vehicles
  • new energy vehicles are mainly powered by power batteries, so the continuous pursuit of high energy density and long cycle life is the main improvement direction of power batteries.
  • One of the purposes of the present invention is to provide a lithium-ion battery to solve the problem that the energy density and cycle life of the battery for new energy vehicles are still insufficient to meet the needs of the existing technology.
  • a lithium ion battery comprising:
  • the positive electrode sheet includes a positive electrode coating area and a positive electrode empty foil area, the positive electrode coating area has macropores and micro mesopores, the specific surface area of the macropores in the positive electrode coating area is less than 3m 2 /g and greater than or equal to 1.0m 2 /g; the specific surface area of the micro mesopores in the positive electrode coating area is 1 to 4m 2 / g, and the volume of the micro mesopores in the positive electrode coating area is 0.9 to 1.1mm 3 /g;
  • the negative electrode sheet includes a negative electrode coating area and a negative electrode empty foil area.
  • the negative electrode coating area has macropores and micro mesopores.
  • the specific surface area of the macropores in the negative electrode coating area is 0.5-2.5m 2 /g;
  • the positive electrode coating area includes a positive electrode current collector and a positive electrode material layer coated on the surface of the positive electrode current collector, the positive electrode empty foil area includes a positive electrode current collector, and the compacted density of the positive electrode material layer is P 1 , 3.3g/cm 3 ⁇ P 1 ⁇ 3.6g/cm 3 .
  • the porosity of the positive electrode coating area is 30-50%.
  • the positive electrode material layer includes a positive electrode active material
  • the positive electrode active material includes at least one of nickel-cobalt lithium manganese oxide ternary material, lithium iron phosphate material, lithium manganese oxide material, lithium cobalt oxide material, nickel-cobalt lithium manganese oxide ternary material modified by doping or coating modification, and lithium iron phosphate material coated with carbon.
  • the positive electrode active material is a ternary material of nickel-cobalt lithium manganese oxide, the particle size D50 of the nickel-cobalt lithium manganate ternary material satisfies 1.5 ⁇ m ⁇ D50 ⁇ 6.5 ⁇ m, and the primary particle size d of the nickel-cobalt lithium manganate ternary material satisfies 500 nm ⁇ d ⁇ 4 ⁇ m.
  • the positive electrode material layer further includes a positive electrode conductive agent, and the mass of the positive electrode conductive agent accounts for 1.0-3.0% of the total mass of the positive electrode material layer.
  • the negative electrode coating area includes a negative electrode current collector and a negative electrode material layer coated on the surface of the negative electrode current collector, the negative electrode empty foil area includes a negative electrode current collector, and the compacted density of the negative electrode material layer is P 2 , 1.5g/cm 3 ⁇ P 2 ⁇ 1.8g/cm 3 .
  • the porosity of the negative electrode coating area is 35-55%.
  • the negative electrode material layer includes a negative electrode active material
  • the negative electrode active material includes at least one of artificial graphite, natural graphite, simple silicon Si, silicon oxide, simple tin and lithium titanate.
  • the negative electrode active material is artificial graphite material
  • the particle size D50 of the artificial graphite material satisfies 8 ⁇ m ⁇ D50 ⁇ 25 ⁇ m
  • the primary particle size d of the artificial graphite material satisfies 6 ⁇ m ⁇ d ⁇ 15 ⁇ m.
  • the negative electrode material layer includes a negative electrode conductive agent, and the mass of the negative electrode conductive agent accounts for 0.5-3.0% of the total mass of the negative electrode material layer.
  • the second object of the present invention is to provide an electrical device comprising the lithium-ion battery described in any one of the above.
  • the beneficial effect of the present invention is that the lithium-ion battery provided by the present invention adjusts the pore structure of the macropores and micro-mesopores in the positive electrode sheet and the negative electrode sheet, and simultaneously optimizes the specific surface area and volume of the macropores and micro-mesopores within an appropriate range, which can significantly improve the rate charge-discharge performance and cycle life of the battery, while taking into account the energy density of the lithium-ion battery.
  • the micro-mesoporous pore diameter is often lower than the critical radius of the electrolyte, so that the electrolyte has a better liquid retention effect in it, so that the battery has a longer service life during long-term operation; while the macropores provide the main path for the transmission of lithium ions inside the coating, effectively improving the rate charge and discharge performance of lithium-ion batteries.
  • Fig. 1 is a schematic structural view of the positive plate in an embodiment
  • Fig. 2 is a schematic structural view of the negative plate in an embodiment
  • the first aspect of the present invention is to provide a lithium ion battery, comprising:
  • the positive electrode sheet 1 includes a positive electrode coating area 2 and a positive electrode empty foil area 3.
  • the positive electrode coating area 2 has macropores and micro mesopores.
  • the specific surface area of the macropores in the positive electrode coating area 2 is less than 3m2 /g and greater than or equal to 1.0m2 / g;
  • the negative electrode sheet 4 includes a negative electrode coating area 5 and a negative electrode empty foil area 6.
  • the negative electrode coating area 5 has macropores and micro mesopores.
  • the specific surface area of the macropores in the negative electrode coating area 5 is 0.5-2.5 m 2 /g;
  • macropores and micro-mesopores are classified according to pore size.
  • macropores with a pore diameter greater than 50 nm mesopores with a pore diameter between 2 and 50 nm, and micropores with a pore diameter less than 2 nm; macropores in this paper refer to macropores with a pore diameter greater than 50 nm, and micro-mesoporous pores in this paper refer to a collection of micropores and mesopores, that is, micro-mesopores with a pore diameter less than or equal to 50 nm.
  • the characterization of the micro-mesoporous structure in this paper is done by nitrogen adsorption test, the specific surface area is taken as the index, and the corresponding test standard is GB/T 19587-2017; the micro-mesoporous volume is taken as the index, and the corresponding test standard is GB/T 21650.2-2008.
  • the characterization of macroporous structure is done by mercury porosimetry test, taking macropore specific surface area as index, and the corresponding test standard is GB/T 21650.1-2008.
  • the macropores are mainly the gaps generated by the accumulation of the positive electrode active material in the positive electrode material layer 7 and the negative electrode active material in the negative electrode material layer 8.
  • the main path can be provided for the transmission of lithium ions inside the coating, thereby improving the rate charge and discharge performance of the lithium ion battery, especially the rate performance at high temperatures.
  • controlling the specific surface area of the macropores of the positive electrode sheet 1 and the negative electrode sheet 4 within the above range can avoid the problems of low compaction density and low energy density, especially for the adjustment of the specific surface area of the macropores in the positive electrode coating area 2. While ensuring the transmission of lithium ions, the specific surface area of the macropores is adjusted within a relatively small range, which can better ensure the compaction density of the material layer.
  • the micro-mesopores are mainly derived from the microstructure of the materials themselves, such as the positive electrode active material or negative electrode active material, conductive agent, and binder.
  • the pore structure of the micro-mesopores in the coating area can be effectively optimized, which not only makes the electrolyte have a better liquid retention effect, but also effectively reduces the problem of excessive side reactions caused by the micro-mesopores.
  • Simultaneous optimization with the macropores greatly improves the charge and discharge rate of lithium-ion batteries at high temperatures. performance.
  • the lithium ion battery of the present invention has excellent battery rate performance, cycle performance and energy density.
  • the specific surface area of the macropores in the positive electrode coating region 2 is B1, and the values can be: 1.0m 2 /g ⁇ B 1 ⁇ 1.2m 2 /g , 1.2m 2 /g ⁇ B 1 ⁇ 1.5m 2 /g, 1.5m 2 /g ⁇ B 1 ⁇ 1.8m 2 /g, 1.8m 2 /g ⁇ B 1 ⁇ 2.0m 2 /g, 2.0m 2 /g ⁇ B 1 ⁇ 2.2m 2 /g, 2.2m 2 /g ⁇ B 1 ⁇ 2.5m 2 /g, 2.5m 2 /g ⁇ B 1 ⁇ 2.8m 2 /g or 2.8m 2 / g ⁇ B 1 ⁇ 3.0m 2 /g.
  • the value of B 1 is 1.5m 2 /g ⁇ B 1 ⁇ 2.8m 2 /g.
  • the volume of the micro-mesopores in the positive electrode coating area 2 is V 1 , and the value can be: 0.9mm 3 /g ⁇ V 1 ⁇ 0.92mm 3 /g, 0.92mm 3 /g ⁇ V 1 ⁇ 0.94mm 3 /g, 0.94mm 3 /g ⁇ V 1 ⁇ 0.96mm 3 / g , 0.96mm 3 / g ⁇ V 1 ⁇ 0.98mm 3 / g , or 1.08 mm 3 / g ⁇ V 1 ⁇ 1.1 mm 3 /g.
  • the value of V 1 is 0.95mm 3 /g ⁇ V 1 ⁇ 1.05mm 3 /g.
  • the specific surface area of the macropores in the negative electrode coating area 5 is B 2 , which can be 0.5m 2 /g ⁇ B 2 ⁇ 0.7m 2 /g, 0.7m 2 /g ⁇ B 2 ⁇ 1.0m 2 /g, 1.0m 2 /g ⁇ B 2 ⁇ 1.2m 2 /g, 1.2m 2 /g ⁇ B 2 ⁇ 1.5m 2 /g, 1.5m 2 / g g ⁇ B 2 ⁇ 1.8m 2 / g , 1.8m 2 /g ⁇ B 2 ⁇ 2.0m 2 /g, 2.0m 2 / g ⁇ B 2 ⁇ 2.2m 2 /g, 2.2m 2 / g ⁇ B 2 ⁇ 2.5m 2 / g.
  • the value of B 2 is 0.7m 2 /g ⁇ B 2 ⁇ 1.8m 2 /g.
  • the specific surface area of the micro-mesopores in the negative electrode coating region 5 is C 2 , which can be: 0.5m 2 /g ⁇ C 2 ⁇ 0.6m 2 /g, 0.60m 2 /g ⁇ C 2 ⁇ 0.8m 2 /g, 0.8m 2 /g ⁇ C 2 ⁇ 1.0m 2 /g, 1.0m 2 /g ⁇ C 2 ⁇ 1.2m 2 /g,
  • the value of C 2 is 0.60m 2 /g ⁇ C 2 ⁇ 1.5m 2 /g.
  • V 2 is 0.44mm 3 /g ⁇ V 2 ⁇ 0.56mm 3 /g.
  • the positive electrode coating area 2 includes a positive electrode current collector 9 and a positive electrode material layer 7 coated on the surface of the positive electrode current collector 9.
  • the positive electrode empty foil area 3 includes a positive electrode current collector 9.
  • the positive electrode current collector 9 in the positive electrode empty foil area 3 is integrated with the positive electrode collector 9 in the positive electrode coating area 2.
  • the positive electrode current collector 9 is aluminum foil, and the compacted density of the positive electrode material layer 7 is P 1 , 3.3g/cm 3 ⁇ P 1 ⁇ 3.6 g/cm 3 .
  • the value of P 1 can be: 3.3g/cm 3 ⁇ P 1 ⁇ 3.35g/cm 3 , 3.35g/cm 3 ⁇ P 1 ⁇ 3.4g/cm 3 , 3.4g/cm 3 ⁇ P 1 ⁇ 3.45g/cm 3 , 3.45g/cm 3 ⁇ P 1 ⁇ 3.5g/cm 3 , 3.5g /cm 3 ⁇ P 1 ⁇ 3.55g / cm 3 or 3.55g/cm 3 ⁇ P 1 ⁇ 3.6g/cm 3 .
  • the value of P 1 is 3.4g/cm 3 ⁇ P 1 ⁇ 3.55g/cm 3 .
  • the compaction density is closely related to the energy density and rate performance of lithium-ion batteries. If the compaction density is too small, the energy density of the battery will be reduced. If the compaction density is too large, the specific surface area of the macropores will be too small, which will affect the transmission of lithium ions and affect the rate charge and discharge performance of the battery.
  • the present invention continues to adjust the compaction density of the positive electrode material layer 7 under the premise of controlling the specific surface area of the macropores in the positive electrode coating area 2 to the above range, which can not only significantly increase the energy density of the lithium-ion battery, but also lay the foundation for a wide range of new energy vehicles. At the same time, it will not affect the transmission of lithium ions, ensuring the rate charge and discharge performance of the battery.
  • the porosity of the positive electrode coating region 2 is 30-50%. Specifically, the porosity of the positive electrode coating region 2 may be 30-33%, 33-35%, 35-38%, 38-40%, 40-43%, 43-45% or 45-50%. Generally, the higher the porosity, the more developed the pore structure, but too high porosity often means too many macropores or too many micro-mesopores, and too many macropores often means too low compaction density and too low energy density, and too many micro-mesopores cannot effectively reduce the occurrence of battery side reactions.
  • the positive electrode material layer 7 includes a positive electrode active material
  • the positive electrode active material includes at least one of nickel-cobalt lithium manganese oxide ternary material, lithium iron phosphate material, lithium manganese oxide material, lithium cobalt oxide material, nickel-cobalt lithium manganese oxide ternary material modified by doping or coating modification, and lithium iron phosphate material coated with carbon.
  • the positive electrode active material is nickel-cobalt lithium manganate ternary material
  • the particle size D50 distribution of the nickel-cobalt lithium manganate ternary material satisfies 1.5 ⁇ m ⁇ D50 ⁇ 6.5 ⁇ m
  • the primary particle size d of the nickel-cobalt lithium manganate ternary material satisfies 500nm ⁇ d ⁇ 4 ⁇ m.
  • the D50 of the nickel-cobalt-lithium manganese oxide ternary material can be tested with a laser particle size analyzer.
  • the particle size of the primary particle size of the nickel-cobalt lithium manganese oxide ternary material can be obtained by statistically identifying the longest size of a single complete grain in the SEM picture.
  • the particle size distribution of the material and the particle size of the primary particles will affect the specific surface area of the macropores, the specific surface area of the micro-mesopores, and the volume of the micro-mesopores.
  • materials with too small a particle size are difficult to control during use and difficult to compact; and materials with too large a particle size are prone to cracking during rolling, which affects the stability of the material; the stability (especially high temperature stability) of materials with too small a primary particle size will deteriorate, and the electrochemical performance of materials with a large primary particle size will deteriorate.
  • the positive electrode material layer 7 further includes a positive electrode conductive agent, and the mass of the positive electrode conductive agent accounts for 1.0-3.0% of the total mass of the positive electrode material layer 7 .
  • the mass of the positive electrode conductive agent accounts for 1.5-2.8% of the total mass of the positive electrode material layer 7 .
  • the positive electrode conductive agent itself is a porous material, and the positive electrode conductive agent is related to the specific surface area and volume of the micro-mesopores. More positive electrode conductive agent can increase the specific surface area of the micro-mesopores in the positive electrode coating area 2, but at the same time it will reduce the proportion of the positive electrode active material and reduce the energy of the battery. By adjusting the conductive agent within the above range, while ensuring the energy density of the battery, a suitable range of micro-mesopore specific surface area and volume can also be obtained to ensure the cycle life of the battery.
  • the positive electrode conductive agent includes at least one of activated carbon, carbon black, carbon nanotubes, graphite, soft carbon, hard carbon, and amorphous carbon;
  • the positive electrode material layer 7 further includes a positive electrode binder
  • the positive electrode binder includes at least one of styrene-butadiene rubber, polyacrylamide, polyvinylidene fluoride, polytetrafluoroethylene, polyacrylonitrile and polyimide.
  • the negative electrode coating area 5 includes a negative electrode current collector 10 and the negative electrode material layer 8 coated on the surface of the negative electrode current collector 10, the negative electrode empty foil area 6 includes the negative electrode current collector 10, and the negative electrode current collector 10 of the negative electrode coating area 5 and the negative electrode current collector 10 of the negative electrode empty foil area 6 are integrated.
  • the negative electrode current collector 10 is copper foil.
  • the compacted density P 2 of the negative electrode material layer 8 is 1.5g/cm 3 ⁇ P 2 ⁇ 1.8g/cm 3 .
  • the value of P 2 can be: 1.5g/cm 3 ⁇ P 2 ⁇ 1.6g/cm 3 , 1.6g/cm 3 ⁇ P 2 ⁇ 1.65g/cm 3 , 1.65g/cm 3 ⁇ P 2 ⁇ 1.7g/cm 3 , 1.7g/cm 3 ⁇ P 2 ⁇ 1.75g/cm 3 or 1.75g/cm 3 ⁇ P 2 ⁇ 1.8g/cm 3 .
  • the value of P 2 is 1.6 g/cm 3 ⁇ P 2 ⁇ 1.75 g/cm 3 .
  • the compaction density is closely related to the energy density and rate performance of lithium-ion batteries. If the compaction density is too small, the energy density of the battery will be reduced.
  • the present invention continues to adjust the compaction density of the negative electrode material layer 8 to match the positive electrode material layer 7, which can not only significantly increase the energy density of the lithium ion battery, lay the foundation for a wide range of applications of new energy vehicles, but also not affect the transmission of lithium ions, and ensure the rate charge and discharge performance of the battery.
  • the porosity of the negative electrode coating region 5 is 35-55%. Specifically, the porosity of the negative electrode coating region 5 may be 35-38%, 38-40%, 40-43%, 43-45%, 45-48%, 48-50%, 50-53% or 53-55%. Preferably, the porosity of the negative electrode coating region 5 is greater than the porosity of the positive electrode coating region 2, so that more pores can be provided for lithium ion intercalation, the intercalation speed is accelerated, and the rate performance improvement for the battery is more significant. In addition, keeping the porosity of the negative electrode coating region 5 within the above range can also avoid the reduction of the compaction density and energy density of the negative electrode sheet 4 due to excessively high porosity, and can also effectively reduce the occurrence of battery side reactions.
  • the negative electrode material layer 8 includes a negative electrode active material
  • the negative electrode active material includes at least one of artificial graphite, natural graphite, simple silicon Si, silicon oxide, simple tin and lithium titanate.
  • the negative electrode active material is made of artificial graphite, the particle size D50 distribution of the artificial graphite material satisfies 8 ⁇ m ⁇ D50 ⁇ 25 ⁇ m, and the primary particle size d of the artificial graphite material satisfies 6 ⁇ m ⁇ d ⁇ 15 ⁇ m.
  • the D50 of the artificial graphite material can be tested with a laser particle size analyzer.
  • the primary particle size of the artificial graphite material can be obtained by statistically identifying the longest size of a single complete grain in the SEM picture.
  • the particle size distribution of the material and the particle size of the primary particles will affect the specific surface area of the macropores, the specific surface area of the micro-mesopores, and the volume of the micro-mesopores.
  • materials with too small a particle size are difficult to control during use and difficult to compact; and materials with too large a particle size are prone to cracking during rolling, which affects the stability of the material; the stability (especially high temperature stability) of materials with too small a primary particle size will deteriorate, and the electrochemical performance of materials with a large primary particle size will deteriorate.
  • the negative electrode material layer 8 further includes a negative electrode conductive agent, and the mass of the negative electrode conductive agent accounts for 0.5-3.0% of the total mass of the negative electrode material layer 8 .
  • the mass of the negative electrode conductive agent accounts for 1.0-2.8% of the total mass of the negative electrode material layer 8 .
  • the negative electrode conductive agent itself is a porous material, and the negative electrode conductive agent is related to the specific surface area and volume of the micro-mesopores. More conductive agent can increase the specific surface area of the micro-mesopores in the negative electrode coating area, but at the same time it will reduce the proportion of the negative electrode active material and reduce the energy of the battery.
  • the present invention can obtain a suitable range of micro-mesopore specific surface area and volume while ensuring the energy density of the battery, so as to ensure the cycle life of the battery.
  • the negative electrode conductive agent includes at least one of activated carbon, carbon black, carbon nanotubes, graphite, soft carbon, hard carbon, and amorphous carbon.
  • the negative electrode material layer 8 further includes a negative electrode binder
  • the negative electrode binder includes at least one of styrene-butadiene rubber, polyacrylamide, polyvinylidene fluoride, polytetrafluoroethylene, polyacrylonitrile and polyimide.
  • the second aspect of the present invention is to provide an electrical device, including any one of the lithium-ion batteries described above.
  • the electrical device is a pure electric vehicle (BEV).
  • BEV pure electric vehicle
  • a pure electric vehicle is a vehicle that is completely powered by a battery and drives wheels with a motor. It has the advantages of environmental protection, low noise, and low cost of use.
  • the preferred ternary lithium-ion battery has outstanding advantages such as high energy density, high working voltage, low self-discharge rate, and environmental friendliness, and can be used as an ideal power supply for BEV motors.
  • the power system of pure electric vehicles is very simple and can be divided into power battery packs and electric motors. Therefore, compared with lithium-ion batteries used in other types of electric vehicles, BEV batteries need to continue to pursue high energy density and long cycle life in order to expand the use of pure electric vehicles.
  • Using the lithium-ion battery provided by the invention as the battery for BEV can not only effectively improve the energy density of the battery, but also greatly prolong the service life of the battery.
  • a kind of lithium ion battery, its preparation method comprises the following steps:
  • volumetric energy density test prepare a test soft-pack lithium-ion battery with a capacity of 3Ah.
  • the nickel-cobalt lithium-manganate 1 soft-pack is first discharged to 2.8V at 3A and then charged to 4.35V at constant voltage.
  • the nickel-cobalt lithium-manganate 2 soft-pack is first discharged at 3A to 2.8V and then charged at 3A to 4.3V at constant voltage.
  • the nickel-cobalt lithium manganate 3 soft-pack is first discharged at 3A to 2.8V and then charged to 4.
  • 2V is charged at a constant voltage, and then discharged to 2.8V with a current of 3A, and the discharge energy when the voltage is reduced to 2.8V is counted, and then the volume of the pouch cell is tested by the drainage method to calculate the volumetric energy density.
  • Example 1 serial number Volume Energy Density (Wh/L) 45°C 1C/1C 80% cycles
  • Example 1 360 2100
  • Example 2 430 1300
  • Example 3 440 2200
  • Example 4 410 1800
  • Example 5 410 1900
  • Example 6 400
  • Example 7 410 2000
  • Example 8 390 1000
  • Example 9 310 2200
  • Example 10 380 1800
  • Example 11 400 1100
  • Example 12 420 1200
  • Example 13 400 2100
  • Example 14 380 1800
  • Example 15 370 1700
  • Example 16 360 1300
  • Example 18 400 1800
  • Example 19 390 1800
  • Example 20 320 2100
  • Example 21 410 2200
  • Example 21 380 1200
  • the energy density and cycle performance of the battery can be effectively improved.
  • the particle size of graphite is further screened, the compaction density of positive electrode material layer 7 and negative electrode material layer 8 is adjusted, the content of positive electrode conductive agent in positive electrode material layer 7 and the content of negative electrode conductive agent in negative electrode material layer 8, and the porosity of positive electrode coating area 2 and negative electrode coating area 5, the energy density and cycle performance of lithium-ion batteries can be more significantly improved.

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Abstract

本发明提供了一种锂离子电池，包括：正极片，包括正极涂覆区和正极空箔区，正极涂覆区具有大孔和微介孔，正极涂覆区的大孔的比表面积小于3m 2/g且大于或等于1.0m 2/g；正极涂覆区的微介孔的比表面积为1～4m 2/g，正极涂覆区的微介孔的体积为0.9～1.1mm 3/g；负极片，包括负极涂覆区和负极空箔区，负极涂覆区具有大孔和微介孔，负极涂覆区的大孔的比表面积为0.5～2.5m 2/g；负极涂覆区的微介孔的比表面积为0.5～2.2m 2/g，负极涂覆区的微介孔的体积为0.4～0.6mm 3/g。相比于现有技术，本发明的锂离子电池具有更为优异的电化学性能，能满足新能源汽车高能量密度、长循环寿命的需求。

Description

一种锂离子电池及用电装置 技术领域
本发明涉及锂电池领域，具体涉及一种锂离子电池及用电装置。
背景技术
新能源汽车是指采用非常规的车用燃料作为动力来源，主要包括以下四种类型：混合动力电动汽车(HEV)、纯电动汽车(BEV，包括太阳能汽车)、燃料电池电动汽车(FCEV)、其他新能源(如超级电容器、飞轮等高效储能器)汽车等。其中，新能源汽车主要是通过动力电池组来提供动力，因此不断追求高能量密度和长循环寿命是动力电池组的主要改进方向。
发明内容
本发明的目的之一在于：针对现有技术的不足，提供一种锂离子电池，以解决目前新能源汽车用电池的能量密度和循环寿命仍不足以满足需求的问题。
为了实现上述目的，本发明采用以下技术方案：
一种锂离子电池，包括：
正极片，包括正极涂覆区和正极空箔区，所述正极涂覆区具有大孔和微介孔，所述正极涂覆区的大孔的比表面积小于3m 2/g且大于或等于1.0m 2/g；所述正极涂覆区的微介孔的比表面积为1～4m 2/g，所述正极涂覆区的微介孔的体积为0.9～1.1mm 3/g；
负极片，包括负极涂覆区和负极空箔区，所述负极涂覆区具有大孔和微介孔，所述负极涂覆区的大孔的比表面积为0.5～2.5m 2/g；所述负极涂覆区的 微介孔的比表面积为0.5～2.2m 2/g，所述负极涂覆区的微介孔的体积为0.4～0.6mm 3/g。
优选的，所述正极涂覆区包括正极集流体以及涂覆于所述正极集流体表面的正极材料层，所述正极空箔区包括正极集流体，所述正极材料层的压实密度为P 1，3.3g/cm 3<P 1<3.6g/cm 3。
优选的，所述正极涂覆区的孔隙率为30～50％。
优选的，所述正极材料层包括正极活性物质，所述正极活性物质包括镍钴锰酸锂三元材料、磷酸铁锂材料、锰酸锂材料、钴酸锂材料、经过掺杂改性或包覆改性的镍钴锰酸锂三元材料和经过碳包覆的磷酸铁锂材料中的至少一种。
优选的，所述正极活性物质为镍钴锰酸锂三元材料，所述镍钴锰酸锂三元材料的粒径D50满足1.5μm<D50<6.5μm，所述镍钴锰酸锂三元材料的一次颗粒粒径d满足500nm<d<4μm。
优选的，所述正极材料层还包括正极导电剂，所述正极导电剂的质量占所述正极材料层的总质量的1.0～3.0％。
优选的，所述负极涂覆区包括负极集流体以及涂覆于所述负极集流体表面的负极材料层，所述负极空箔区包括负极集流体，所述负极材料层的压实密度为P 2，1.5g/cm 3<P 2<1.8g/cm 3。
优选的，所述负极涂覆区的孔隙率为35～55％。
优选的，所述负极材料层包括负极活性物质，所述负极活性物质包括人造石墨、天然石墨、硅单质Si、硅氧化物、锡单质和钛酸锂中的至少一种。
优选的，所述负极活性物质为人造石墨材料，所述人造石墨材料的粒径D 50满足8μm<D50<25μm，所述人造石墨材料的一次颗粒粒径d满足6μm<d<15μm。
优选的，所述负极材料层包括还负极导电剂，所述负极导电剂的质量占所述负极材料层总质量的0.5～3.0％。
本发明的目的之二在于，提供一种用电装置，包括上述任一项所述的锂离子电池。
相比于现有技术，本发明的有益效果在于：本发明提供的锂离子电池，调整正极片和负极片中大孔和微介孔的孔道结构，将大孔和微介孔的比表面积、体积同步优化在合适的范围内，可显著提升电池的倍率充放电性能和循环寿命，同时兼顾了锂离子电池的能量密度。具体的，微介孔孔径往往低于电解液的临界半径，使得电解液在其中有更好的保液效果，从而使得电池在长期运行过程中具有更长的使用寿命；而大孔给锂离子在涂层内部的传输提供了主要路径，有效改善了锂离子电池的倍率充放电性能。
附图说明
为了更清楚地说明本发明实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本发明的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图示出的结构获得其他的附图。
图1为一实施例中正极片的结构示意图；
图2为一实施例中负极片的结构示意图；
1、正极片；2、正极涂覆区；3、正极空箔区；4、负极片；5、负极涂覆区；6、负极空箔区；7、正极材料层；8、负极材料层；9、正极集流体；10、负极集流体。
本发明目的的实现、功能特点及优点将结合实施例，参照附图做进一步说明。
具体实施方式
本发明第一方面在于提供一种锂离子电池，包括：
正极片1，包括正极涂覆区2和正极空箔区3，正极涂覆区2具有大孔和微介孔，正极涂覆区2的大孔的比表面积小于3m 2/g且大于或等于1.0m 2/g；正极涂覆区2的微介孔的比表面积为1～4m 2/g，正极涂覆区2的微介孔的体积为0.9～1.1mm 3/g；
负极片4，包括负极涂覆区5和负极空箔区6，负极涂覆区5具有大孔和微介孔，负极涂覆区5的大孔的比表面积为0.5～2.5m 2/g；负极涂覆区5的微介孔的比表面积为0.5～2.2m 2/g，负极涂覆区5的微介孔的体积为0.4～0.6mm 3/g。
其中，本文大孔、微介孔是按孔径大小进行划分。根据国际理论(化学)与应用化学联合会IUPAC的定义，孔径大于50nm为大孔，孔径介于2～50n m之间的为中孔(即是介孔)，而孔径小于2nm为微孔；本文大孔即是孔径大于50nm的为大孔，本文微介孔则是为微孔和中孔的集合，即是孔径小于或等于50nm的为微介孔。
本文中微介孔结构的表征是通过氮气吸附试验完成，取比表面积作为指标，对应测试标准为GB/T 19587-2017；取微介孔体积作为指标，对应测试标准为GB/T 21650.2-2008。大孔结构的表征是通过压汞法试验完成，取大孔比表面积作为指标，对应测试标准为GB/T 21650.1-2008。
对于正极涂覆区2和负极涂覆区5而言，大孔主要是来源于正极材料层7的正极活性物质和负极材料层8的负极活性物质的堆积产生的缝隙，通过控制最终的大孔的比表面积，可为锂离子在涂层内部的传输提供主要的路径，进而改善锂离子电池的倍率充放电性能，特别是在高温下的倍率性能。对于本发明的锂离子电池而言，将正极片1和负极片4的大孔的比表面积控制在上述范围内，可避免压实密度过低和能量密度过低的问题，特别是对于正极涂覆区2中大孔比表面积的调整，在保证锂离子传输的同时，将大孔的比表面积调整在相对较小的范围内，可更好的保证材料层的压实密度。
而对于正极涂覆区2和负极涂覆区5而言，微介孔主要是来源与正极活性物质或负极活性物质、导电剂、粘结剂等组成材料本身的微观结构，通过同步调控微介孔的比表面积和体积，可有效优化涂覆区微介孔的孔道结构，不仅可使得电解液具有更好的保液效果，也有效降低了因微介孔带来的副反应过多问题，与大孔同步优化，大大改善了锂离子电池在高温下倍率充放电性能。
本发明通过优化正极片1和负极片4中的孔道结构，不同类型的孔道相互影响相互促进，最终使得本发明的锂离子电池具有优异的电池倍率性能、循环性能和能量密度。
具体的，正极涂覆区2的大孔的比表面积为B1，取值可为：1.0m 2/g≤B 1＜1.2m 2/g、1.2m 2/g≤B 1＜1.5m 2/g、1.5m 2/g≤B 1＜1.8m 2/g、1.8m 2/g≤B 1＜2.0m 2/g、2.0m 2/g≤B 1＜2.2m 2/g、2.2m 2/g≤B 1＜2.5m 2/g、2.5m 2/g≤B 1＜2.8m 2/g或2.8m 2/g≤B 1＜3.0m 2/g。优选的，B 1取值为1.5m 2/g≤B 1≤2.8m 2/g。
正极涂覆区2的微介孔的比表面积为C1，取值可为：1.0m 2/g≤C 1＜1.2m 2/g、1.2m 2/g≤C 1＜1.5m 2/g、1.5m 2/g≤C 1＜1.8m 2/g、1.8m 2/g≤C 1＜2.0m 2/g、2.0m 2/g≤C 1＜2.2m 2/g、2.2m 2/g≤C 1＜2.5m 2/g、2.5m 2/g≤C 1＜2.8m 2/g、2.8m 2/g≤C 1＜3.0m 2/g、3.0m 2/g≤C 1＜3.2m 2/g、3.2m 2/g≤C 1＜3.5m 2/g、3.5m 2/g≤C 1＜3.8m 2/g或3.8m 2/g≤C 1≤4.0m 2/g。优选的，C 1取值为1.5m 2/g≤C 1≤3.0m 2/g。
正极涂覆区2的微介孔的体积为V 1，取值可为：0.9mm 3/g≤V 1＜0.92mm 3/g、0.92mm 3/g≤V 1＜0.94mm 3/g、0.94mm 3/g≤V 1＜0.96mm 3/g、0.96mm 3/g≤V 1＜0.98mm 3/g、0.98mm 3/g≤V 1＜1.0mm 3/g、1.0mm 3/g≤V 1＜1.02mm 3/g、1.02mm 3/g≤V 1＜1.04mm 3/g、1.04mm 3/g≤V 1＜1.06mm 3/g、1.06mm 3/g≤V 1＜1.08mm 3/g或1.08mm 3/g≤V 1≤1.1mm 3/g。优选的，V 1的取值为0.95mm 3/g≤V 1≤1.05mm 3/g。
负极涂覆区5的大孔的比表面积为B 2，取值可为0.5m 2/g≤B 2＜0.7m 2/g、0.7m 2/g≤B 2＜1.0m 2/g、1.0m 2/g≤B 2＜1.2m 2/g、1.2m 2/g≤B 2＜1.5m 2/g、1.5m 2/g≤B 2＜1.8m 2/g、1.8m 2/g≤B 2＜2.0m 2/g、2.0m 2/g≤B 2＜2.2m 2/g、2.2m 2/g≤B 2≤2.5m 2/g。优选的，B 2取值为0.7m 2/g≤B 2≤1.8m 2/g。
负极涂覆区5的微介孔的比表面积为C 2，取值可为：0.5m 2/g≤C 2＜0.6m 2/g、0.60m 2/g≤C 2＜0.8m 2/g、0.8m 2/g≤C 2＜1.0m 2/g、1.0m 2/g≤C 2＜1.2m 2/g、
1.2m 2/g≤C 2＜1.5m 2/g、1.5m 2/g≤C 2＜1.8m 2/g、1.8m 2/g≤C 2＜2.0m 2/g或2.0m 2/g≤C 2＜2.2m 2/g。优选的，C 2取值为0.60m 2/g≤C 2≤1.5m 2/g。
负极涂覆区5的微介孔的体积为V 2，取值可为：0.4mm 3/g≤V 2＜0.42mm 3/g、0.42mm 3/g≤V 2＜0.44mm 3/g、0.44mm 3/g≤V 2＜0.46mm 3/g、0.46mm 3/g≤V 2＜0.48mm 3/g、0.48mm 3/g≤V 2＜0.50mm 3/g、0.50mm 3/g≤V 2＜0.52mm 3/g、0.52mm 3/g≤V 2＜0.54mm 3/g、0.54mm 3/g≤V 2＜0.56mm 3/g、0.56mm 3/g≤V 2＜0.58mm 3/g或0.58mm 3/g≤V 2≤0.6mm 3/g。优选的，V 2的取值为0.44mm 3/g≤V 2≤0.56mm 3/g。
为实现对大孔比表面积、微介孔比表面积、微介孔体积的调整，我们需要选择合适的正极材料层7、负极材料层8以及合适的压实密度。
在一些实施例中，正极涂覆区2包括正极集流体9以及涂覆于正极集流体9表面的正极材料层7，正极空箔区3包括正极集流体9，正极空箔区3的 正极集流体9与正极涂覆区2的正极集流体9一体设置，在本实施例中，正极集流体9为铝箔，正极材料层7的压实密度为P 1，3.3g/cm 3<P 1<3.6g/cm 3。具体的，P 1的取值可为：3.3g/cm 3<P 1≤3.35g/cm 3、3.35g/cm 3<P 1≤3.4g/cm 3、3.4g/cm 3<P 1≤3.45g/cm 3、3.45g/cm 3<P 1≤3.5g/cm 3、3.5g/cm 3<P 1≤3.55g/cm 3或3.55g/cm 3<P 1＜3.6g/cm 3。优选的，P 1的取值为3.4g/cm 3<P 1≤3.55g/cm 3。压实密度与锂离子电池的能量密度和倍率性能息息相关，压实密度过小，会降低电池的能量密度，压实密度过大，大孔的比表面积过小，会影响锂离子的传输，影响电池的倍率充放电性能。本发明在控制正极涂覆区2中大孔比表面积为上述范围的前提下，继续调整正极材料层7的压实密度，不仅可显著提升锂离子电池的能量密度，为新能源汽车的大范围应用打下基础，同时也不会影响锂离子的传输，保证电池的倍率充放电性能。
在一些实施例中，正极涂覆区2的孔隙率为30～50％。具体的，正极涂覆区2的孔隙率可为30～33％、33～35％、35～38％、38～40％、40～43％、43～45％或45～50％。一般的，孔隙率越高，孔道结构越发达，但过高孔隙率往往意味过多的大孔或过多的微介孔，而过多的大孔则往往意味着过低的压实密度和过低的能量密度，过多的微介孔则无法有效降低电池副反应的发生。
在一些实施例中，正极材料层7包括正极活性物质，正极活性物质包括镍钴锰酸锂三元材料、磷酸铁锂材料、锰酸锂材料、钴酸锂材料、经过掺杂改性或包覆改性的镍钴锰酸锂三元材料和经过碳包覆的磷酸铁锂材料中的至少一种。优选的，正极活性物质选用镍钴锰酸锂三元材料，镍钴锰酸锂三元材料的粒径D50分布满足1.5μm<D50<6.5μm，镍钴锰酸锂三元材料的一次 颗粒粒径d满足500nm<d<4μm。其中，镍钴锰酸锂三元材料的D50可以使用激光粒度仪进行测试，镍钴锰酸锂三元的一次颗粒粒径大小通过SEM图片中可通过统计可辨识单颗完整晶粒的最长尺寸得到。材料的粒径分布和一次颗粒粒径大小会影响大孔比表面积、微介孔比表面积、微介孔的体积。一般地，在性能上，粒径过小材料在使用过程中工艺难以调控，压实困难；而粒径过大则材料在辊压过程中容易发生龟裂，影响材料的稳定性；一次颗粒粒径过小材料的稳定性(尤其是高温稳定性)会变差，而一次颗粒粒径过大材料的电化学性能会变差。
在一些实施例中，正极材料层7还包括正极导电剂，正极导电剂的质量占正极材料层7总质量的1.0～3.0％。优选的，正极导电剂的质量占正极材料层7总质量的1.5～2.8％。正极导电剂本身为多孔材料，正极导电剂与微介孔的比表面积和体积相关，较多的正极导电剂可提升正极涂覆区2微介孔的比表面积，但同时会减少正极活性物质的占比，降低电池的能量，本发明通过调整导电剂在上述范围内，在保证电池能量密度的同时，也可获得合适范围的微介孔比表面积和体积，以保证电池的循环寿命。
在一些实施例中，正极导电剂包括活性炭、炭黑、碳纳米管、石墨、软碳、硬碳和无定型碳中的至少一种；
在一些实施例中，正极材料层7还包括正极粘接剂，正极粘接剂包括丁苯橡胶、聚丙烯酰胺、聚偏氟乙烯、聚四氟乙烯、聚丙烯腈和聚酰亚胺中的至少一种。
在一些实施例中，负极涂覆区5包括负极集流体10以及涂覆于负极集流体10表面的负极材料层8，负极空箔区6包括负极集流体10，负极涂覆区5的负极集流体10和负极空箔区6的负极集流体10一体设置，在本实施例中，负极集流体10为铜箔。负极材料层8的压实密度P 2，1.5g/cm 3<P 2<1.8g/cm 3。具体的，P 2的取值可为：1.5g/cm 3<P 2≤1.6g/cm 3、1.6g/cm 3<P 2≤1.65g/cm 3、1.65g/cm 3<P 2≤1.7g/cm 3、1.7g/cm 3<P 2≤1.75g/cm 3或1.75g/cm 3<P 2＜1.8g/cm 3。优选的，P 2的取值为1.6g/cm 3＜P 2≤1.75g/cm 3。压实密度与锂离子电池的能量密度和倍率性能息息相关，压实密度过小，会降低电池的能量密度，压实密度过大大，大孔的比表面积过小，会影响锂离子的传输，影响电池的倍率充放电性能。本发明在控制负极涂覆区5中大孔比表面积为上述范围的前提下，继续调整负极材料层8的压实密度，与正极材料层7相匹配，不仅可显著提升锂离子电池的能量密度，为新能源汽车的大范围应用打下基础，同时也不会影响锂离子的传输，保证电池的倍率充放电性能。
在一些实施例中，负极涂覆区5的孔隙率为35～55％。具体的，负极涂覆区5的孔隙率可为35～38％、38～40％、40～43％、43～45％、45～48％、48～50％、50～53％或53～55％。优选的，负极涂覆区5的孔隙率大于正极涂覆区2的孔隙率，如此可提供更多的孔隙供锂离子嵌入，嵌入速度加快，对于电池的倍率性能改善更加显著。此外，保持负极涂覆区5的孔隙率在上述范围内，也可避免因孔隙率过高导致负极片4的压实密度和能量密度降低，也能有效降低电池副反应的发生。
在一些实施例中，负极材料层8包括负极活性物质，负极活性物质包括人造石墨、天然石墨、硅单质Si、硅氧化物、锡单质和钛酸锂中的至少一种。 优选的，负极活性物质选用人造石墨材料，人造石墨材料的粒径D50分布满足8μm<D50<25μm，人造石墨材料的一次颗粒粒径d满足6μm<d<15μm。其中，人造石墨材料的D50可以使用激光粒度仪进行测试，人造石墨材料的一次颗粒粒径大小通过SEM图片中可通过统计可辨识单颗完整晶粒的最长尺寸得到。材料的粒径分布和一次颗粒粒径大小会影响大孔比表面积、微介孔比表面积、微介孔的体积。一般地，在性能上，粒径过小材料在使用过程中工艺难以调控，压实困难；而粒径过大则材料在辊压过程中容易发生龟裂，影响材料的稳定性；一次颗粒粒径过小材料的稳定性(尤其是高温稳定性)会变差，而一次颗粒粒径过大材料的电化学性能会变差。
在一些实施例中，负极材料层8还包括负极导电剂，负极导电剂的质量占负极材料层8总质量的0.5～3.0％。优选的，负极导电剂的质量占负极材料层8总质量的1.0～2.8％。负极导电剂本身为多孔材料，负极导电剂与微介孔的比表面积和体积相关，较多的导电剂可提升负极涂覆区5微介孔的比表面积，但同时会减少负极活性物质的占比，降低电池的能量，本发明通过调整导电剂在上述范围内，在保证电池能量密度的同时，也可获得合适范围的微介孔比表面积和体积，以保证电池的循环寿命。
在一些实施例中，负极导电剂包括活性炭、炭黑、碳纳米管、石墨、软碳、硬碳和无定型碳中的至少一种。
在一些实施例中，负极材料层8还包括负极粘接剂，负极粘接剂包括丁苯橡胶、聚丙烯酰胺、聚偏氟乙烯、聚四氟乙烯、聚丙烯腈和聚酰亚胺中的至少一种。
本发明第二方面在于提供一种用电装置，包括上述任一项的锂离子电池。
优选的，该用电装置为纯电动汽车(BEV)，纯电动汽车是完全由蓄电池提供电力，用电机驱动车轮行驶的车型，具有环保、低噪音、使用成本低廉等优点。其中优选的三元锂离子电池具有高能量密度、高工作电压、较低的自放电率、环境友好等突出优势，可以作为BEV电机的理想电源。较其他类型的电动车来说，纯电动车动力系统十分简单，可以划分为动力电池组与电动机，因此与其他类型的电动车采用的锂离子电池相比，BEV电池更需要不断追求高能量密度和长循环寿命，以拓宽纯电动汽车的使用范围。采用本发明提供的锂离子电池作为BEV用电池，不仅可有效提升电池的能量密度，还大大延长了电池的使用寿命。
下面结合实施例，举例说明本发明的实施方案。应理解，这些实施例仅用于说明本发明而不意在限制本发明要求保护的范围。
实施例1～22
一种锂离子电池，其制备方法包括以下步骤：
1)将正极活性物质粉末、导电碳、碳纳米管以及PVDF以规定比例混合，然后在高速搅拌机中加入NMP并均匀混合成固含量为74％的浆料；将该浆料使用转移涂布机涂布于厚度为13微米的铝箔单面，并干燥，保持单位面积涂层干燥后重量为20.0mg/cm 2；然后在铝箔的另一面采用同样的工序涂布并干燥获得正极片1半成品；
2)将负极活性物质粉末、导电碳、碳纳米管、CMC以及SBR以指定比例混合，然后在高速搅拌机中加入去离子水并均匀混合成固含量为48％的浆料。将该浆料使用转移涂布机涂布于厚度为8微米的铜箔单面，并干燥，保持单位面积涂层干燥后重量为18.1mg/cm 2。然后在铜箔的另一面采用同样的工序涂布并干燥获得负极片4半成品；
3)将上述极片的裸露金属箔材部分加工并焊接成极耳，然后与隔离膜卷绕形成卷芯；使用铝塑膜包裹卷芯制成半成品电芯后注入电解液，经化成、分容步骤获得成品锂离子电池。
通过控制正极材料层7和负极材料层8的种类、材料的粒径尺寸、调控正极材料层7和负极材料层8的压实密度、正极材料层7的正极导电剂和负极材料层8的负极导电剂的含量以及正极涂覆区2和负极涂覆区5的孔隙率，从而调整正极涂覆区2和负极涂覆区5的大孔比表面积、微介孔比表面积以及微介孔体积，具体见以下多个实施例。
性能测试
1)体积能量密度测试：制备容量为3Ah的测试用软包锂离子电池，镍钴锰酸锂1软包先以3A电流放电至2.8V再以3A电流充电至4.35V在恒压充电，镍钴锰酸锂2软包先以3A电流放电至2.8V再以3A电流充电至4.3V在恒压充电，镍钴锰酸锂3软包先以3A电流放电至2.8V再以3A电流充电至4.2V在恒压充电，然后以3A电流放电至2.8V，统计电压降低至2.8V时的放电能量，再用排水法测试软包电芯体积，即可计算体积能量密度。
2)45℃循环性能测试：制备容量为3Ah的测试用软包锂离子电池，在恒温45度的设备中镍钴锰酸锂1以3A电流在2.8V-4.35V电压范围内进行充放电循环，镍钴锰酸锂2以3A电流在2.8V-4.3V电压范围内进行充放电循环，镍钴锰酸锂3以3A电流在2.8V-4.2V电压范围内进行充放电循环，统计当电池容量保持率降低至80％时经历的循环周数。
以上测试结果见表3。
表1电极材料明细
Figure PCTCN2022124017-appb-000001
表2工艺参数明细
Figure PCTCN2022124017-appb-000002
Figure PCTCN2022124017-appb-000003
表3测试结果
编号 体积能量密度(Wh/L) 45℃ 1C/1C 80％的循环周数
实施例1 360 2100
实施例2 430 1300
实施例3 440 2200
实施例4 410 1800
实施例5 410 1900
实施例6 400 1800
实施例7 410 2000
实施例8 390 1000
实施例9 310 2200
实施例10 380 1800
实施例11 400 1100
实施例12 420 1200
实施例13 400 2100
实施例14 380 1800
实施例15 370 1700
实施例16 360 1300
实施例17 370 800
实施例18 400 1800
实施例19 390 1800
实施例20 320 2100
实施例21 410 2200
实施例21 380 1200
由上述各实施例的参数及其测试结果可以看出：
1)由实施例11～13、实施例16～18、以及实施例19～21的对比中，可以看出，当只有正极涂覆区2满足上述范围时，相比于只有负极涂覆区5满足上述范围的情形，锂离子电池具有更好的综合电化学性能，兼顾了高能量密度与长循环寿命；而当正极涂覆区2和负极涂覆区5均满足上述范围时，锂离子电池具有更佳的电化学性能。
2)由实施例1～2、8～9、22和实施例3～4、7、10、13～14、18、21的对比中可以看出，当同时将正极涂覆区2和负极涂覆区5的压实密度、正极 涂覆区2和负极涂覆区5的大孔比表面积、正极涂覆区2和负极涂覆区5的微介孔比表面积和体积、正极涂覆区2和负极涂覆区5的孔隙率调整在本发明筛选范围内时，可尽可能地提升锂离子电池的能量密度和循环寿命；而如都不落入上述范围，则表现出较差的电化学性能，不能兼顾高能量密度与长循环寿命，参见实施例1～2、8～9、22的测试结果。特别地，当人造石墨的粒径分布满足8μm<D50<25μm，一次颗粒粒径d满足6μm<d<15μm时，如人造石墨1，其在锂离子电池体系中电化学性能表现更佳。
3)由实施例3和4、以及实施例13和14的对比中还可以看出，当负极涂覆区5的孔隙率高于正极涂覆区2的孔隙率时，锂离子电池表现出更优异的电化学性能，可同时兼顾高能量密度与长循环寿命。这主要是因为负极更高的孔隙率可提供更多的孔隙供锂离子嵌入，嵌入速度加快，对于电化学性能的改善也就越显著。
综上可见，当同时调控正极涂覆区2和负极涂覆区5的大孔比表面积、微介孔比表面积以及微介孔体积，并将其均优化在合适范围内，可以有效提升电池的能量密度和循环性能。当进一步筛选石墨的粒径尺寸、调控正极材料层7和负极材料层8的压实密度、正极材料层7的正极导电剂的含量和负极材料层8的负极导电剂的含量以及正极涂覆区2的孔隙率和负极涂覆区5的孔隙率时，可更加显著地提升锂离子电池的能量密度和循环性能。
根据上述说明书的揭示和教导，本发明所属领域的技术人员还能够对上述实施方式进行变更和修改。因此，本发明并不局限于上述的具体实施方式，凡是本领域技术人员在本发明的基础上所作出的任何显而易见的改进、替换 或变型均属于本发明的保护范围。此外，尽管本说明书中使用了一些特定的术语，但这些术语只是为了方便说明，并不对本发明构成任何限制。

Claims (12)

  1. 一种锂离子电池，其特征在于，包括：
    正极片，包括正极涂覆区和正极空箔区，所述正极涂覆区具有大孔和微介孔，所述正极涂覆区的大孔的比表面积小于3m 2/g且大于或等于1.0m 2/g；所述正极涂覆区的微介孔的比表面积为1～4m 2/g，所述正极涂覆区的微介孔的体积为0.9～1.1mm 3/g；
    负极片，包括负极涂覆区和负极空箔区，所述负极涂覆区具有大孔和微介孔，所述负极涂覆区的大孔的比表面积为0.5～2.5m 2/g；所述负极涂覆区的微介孔的比表面积为0.5～2.2m 2/g，所述负极涂覆区的微介孔的体积为0.4～0.6mm 3/g。
  2. 根据权利要求1所述的锂离子电池，其特征在于，所述正极涂覆区包括正极集流体以及涂覆于所述正极集流体表面的正极材料层，所述正极材料层的压实密度为P 1，3.3g/cm 3<P 1<3.6g/cm 3。
  3. 根据权利要求1或2所述的锂离子电池，其特征在于，所述正极涂覆区的孔隙率为30～50％。
  4. 根据权利要求2所述的锂离子电池，其特征在于，所述正极材料层包括正极活性物质，所述正极活性物质包括镍钴锰酸锂三元材料、磷酸铁锂材料、锰酸锂材料、钴酸锂材料、经过掺杂改性或包覆改性的镍钴锰酸锂三元材料和经过碳包覆的磷酸铁锂材料中的至少一种。
  5. 根据权利要求4所述的锂离子电池，其特征在于，所述正极活性物质为镍钴锰酸锂三元材料，所述镍钴锰酸锂三元材料的粒径D50满足1.5μm<D50<6.5μm，所述镍钴锰酸锂三元材料的一次颗粒粒径d满足500nm<d<4μm。
  6. 根据权利要求2、4～5任一项所述的锂离子电池，其特征在于，所述正极材料层还包括正极导电剂，所述正极导电剂的质量占所述正极材料层的总质量的1.0～3.0％。
  7. 根据权利要求1所述的锂离子电池，其特征在于，所述负极涂覆区包括负极集流体以及涂覆于所述负极集流体表面的负极材料层，所述负极材料层的压实密度为P 2，1.5g/cm 3<P 2<1.8g/cm 3。
  8. 根据权利要求1或7所述的锂离子电池，其特征在于，所述负极涂覆区的孔隙率为35～55％。
  9. 根据权利要求7所述的锂离子电池，其特征在于，所述负极材料层包括负极活性物质，所述负极活性物质包括人造石墨、天然石墨、硅单质Si、硅氧化物、锡单质和钛酸锂中的至少一种。
  10. 根据权利要求9所述的锂离子电池，其特征在于，所述负极活性物质为人造石墨材料，所述人造石墨材料的粒径D50满足8μm<D50<25μm，所述人造石墨材料的一次颗粒粒径d满足6μm<d<15μm。
  11. 根据权利要求7、9～10任一项所述的锂离子电池，其特征在于，所述负极材料层还包括负极导电剂，所述负极导电剂的质量占所述负极材料层总质量的0.5～3.0％。
  12. 一种用电装置，其特征在于，包括权利要求1～11任一项所述的锂离子电池。
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