WO2023142024A1 - 一种长寿命二次电池及电池模块、电池包和用电装置 - Google Patents

一种长寿命二次电池及电池模块、电池包和用电装置 Download PDF

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WO2023142024A1
WO2023142024A1 PCT/CN2022/074932 CN2022074932W WO2023142024A1 WO 2023142024 A1 WO2023142024 A1 WO 2023142024A1 CN 2022074932 W CN2022074932 W CN 2022074932W WO 2023142024 A1 WO2023142024 A1 WO 2023142024A1
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cap
negative electrode
positive electrode
electrode film
film layer
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PCT/CN2022/074932
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English (en)
French (fr)
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陈晓
王广军
叶永煌
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宁德时代新能源科技股份有限公司
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Priority to PCT/CN2022/074932 priority Critical patent/WO2023142024A1/zh
Priority to EP22917626.8A priority patent/EP4280298A1/en
Priority to US18/346,794 priority patent/US20230369556A1/en
Publication of WO2023142024A1 publication Critical patent/WO2023142024A1/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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • 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
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/661—Metal or alloys, e.g. alloy coatings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present application relates to the technical field of secondary batteries, in particular to a long-life secondary battery, a battery module, a battery pack and an electrical device.
  • secondary batteries have been widely used in energy storage power systems such as hydraulic, thermal, wind and solar power plants, as well as electric tools, electric bicycles, electric motorcycles, electric vehicles, Military equipment, aerospace and other fields. Due to the great development of secondary batteries, higher requirements have been put forward for their energy density, cycle performance and safety performance.
  • Improving the cycle performance of secondary batteries can not only reduce costs, but also reduce the environmental pressure caused by recycling secondary batteries, which is of great significance.
  • the present application was made in view of the above problems, and an object of the present application is to provide a secondary battery having improved cycle performance and safety performance.
  • the present application provides a secondary battery, a battery module, a battery pack and an electrical device.
  • the first aspect of the present application provides a secondary battery, including a positive pole piece, a negative pole piece, and a separator placed between the positive pole piece and the negative pole piece,
  • the positive electrode sheet includes a positive electrode current collector and positive electrode film layers A1 and B1 respectively arranged on the two surfaces of the positive electrode current collector, and the negative electrode sheet includes a negative electrode current collector and are respectively arranged on two surfaces of the negative electrode current collector.
  • Cap A1 and Cap B1 of the positive electrode film layers A1 and B1 satisfy Cap A1 ⁇ Cap B1, and at least one through hole is provided on the negative electrode current collector of the negative electrode sheet.
  • the present application adjusts the capacity ratio of the positive electrode film on both sides of the positive electrode sheet, and further adopts the method of punching holes in the negative electrode current collector to achieve the effect of slowing down the attenuation of the secondary battery and prolonging the service life, that is, improving the performance of the secondary battery. cycle performance.
  • the capacities Cap A1 and Cap B1 per unit area of the positive electrode film layers A1 and B1 satisfy 0.7 ⁇ Cap A1/Cap B1 ⁇ 1.
  • the cycle performance of the secondary battery can be further improved.
  • the negative electrode film layer opposite to the positive electrode film layer A1 separated by a separator is A2, and the capacity per unit area Cap A2 and Cap A1 of the negative electrode film layer A2 and the positive electrode film layer A1 satisfy 1.02 ⁇ Cap A2/Cap A1 ⁇ 1.2.
  • the ratio of the capacity per unit area Cap A2 and Cap A1 of the negative electrode film layer A2 and the positive electrode film layer A1 is within a given range, the safety performance of the secondary battery can be improved.
  • the negative electrode film layer opposite to the positive electrode film layer B1 separated by a separator is B2, and the capacity per unit area Cap B2 and Cap B1 of the negative electrode film layer B2 and the positive electrode film layer B1 satisfy max(Cap A1/Cap B1, (Cap B1+Cap A1-Cap A2)/Cap B1) ⁇ Cap B2/Cap B1 ⁇ 1.
  • the ratio of the capacity per unit area Cap B2 and Cap B1 of the negative electrode film layer B2 to the positive electrode film layer B1 is within a given range, the amount of negative electrode active material can be reduced while ensuring that the negative electrode film layer B2 does not decompose lithium, thereby improving Energy density of secondary batteries.
  • the ratio of the area of the through hole to the area of the negative electrode current collector is 0.2%-40%.
  • the ratio of the area of the through hole to the area of the negative electrode current collector is within the given range, the production processability of the negative electrode sheet and the conduction effect of lithium ions on the AB surface of the negative electrode film layer can be taken into account.
  • the diameter of the through hole is 5-500 ⁇ m, optionally 50-250 ⁇ m.
  • both the strength of the negative electrode sheet and the uniformity of the current density of the negative electrode sheet can be taken into account.
  • the positive electrode sheet has a compacted density of 2.0-3.6 g/cc, optionally 2.3-3.5 g/cc.
  • the negative electrode sheet has a compacted density of 0.5-2 g/cc, optionally 1.0-1.8 g/cc.
  • a second aspect of the present application provides a battery module including the secondary battery of the first aspect of the present application.
  • a third aspect of the present application provides a battery pack including the battery module of the second aspect of the present application.
  • the fourth aspect of the present application provides an electric device, the electric device includes the secondary battery selected from the first aspect of the present application, the battery module of the second aspect of the present application or the battery of the third aspect of the present application At least one of the packages.
  • the battery module, battery pack, and electric device of the present application include the secondary battery of the present application, and thus have at least the same advantages as the secondary battery.
  • FIG. 1 is a schematic diagram of a battery cell of a secondary battery according to an embodiment of the present application.
  • FIG. 2 is a schematic diagram of a negative electrode sheet of a secondary battery according to an embodiment of the present application.
  • FIG. 3 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 4 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG. 3 .
  • FIG. 5 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG. 6 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 7 is an exploded view of the battery pack according to one embodiment of the present application shown in FIG. 6 .
  • FIG. 8 is a schematic diagram of an electrical device in which a secondary battery is used as a power source according to an embodiment of the present application.
  • ranges disclosed herein are defined in terms of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive and may be combined arbitrarily, ie any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are contemplated. Additionally, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range "a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article, and "0-5" is only an abbreviated representation of the combination of these values.
  • a certain parameter is an integer ⁇ 2
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed in sequence, and may also include steps (b) and (a) performed in sequence.
  • steps (a) and (b) performed in sequence
  • steps (b) and (a) performed in sequence.
  • step (c) means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), also Steps (a), (c) and (b) may be included, and steps (c), (a) and (b) may also be included.
  • the "comprising” and “comprising” mentioned in this application means open or closed.
  • the “comprising” and “comprising” may mean that other components not listed may be included or included, or only listed components may be included or included.
  • the term "or” is inclusive unless otherwise stated.
  • the phrase "A or B” means “A, B, or both A and B.” More specifically, the condition "A or B” is satisfied by either of the following: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; or both A and B are true (or exist).
  • the inventors of the present application found that by adjusting the capacity ratio of the positive electrode film on both sides of the positive electrode sheet, combined with the method of punching holes on the negative electrode current collector, the active lithium consumption during the charging and discharging process can be supplemented, thereby slowing down the secondary The secondary battery decays and prolongs its service life.
  • the present application proposes a secondary battery, including a positive pole piece, a negative pole piece, and a separator placed between the positive pole piece and the negative pole piece,
  • the positive electrode sheet includes a positive electrode current collector and positive electrode film layers A1 and B1 respectively arranged on the two surfaces of the positive electrode current collector, and the negative electrode sheet includes a negative electrode current collector and are respectively arranged on two surfaces of the negative electrode current collector.
  • Cap A1 and Cap B1 of the positive electrode film layers A1 and B1 satisfy Cap A1 ⁇ Cap B1, and at least one through hole is provided on the negative electrode current collector of the negative electrode sheet.
  • the inventors of the present application speculate that it is due to the following reasons: the application achieves the effect of pre-existing the active lithium in the secondary battery in the positive electrode sheet by regulating the capacity ratio of the positive electrode film on both sides of the positive electrode sheet; Further adopting the method of punching holes in the negative electrode current collector, the active lithium pre-stored in the positive electrode sheet can be slowly transferred to the negative electrode sheet during use, and finally released to supplement the consumption of active lithium in the system, so as to slow down the attenuation of the secondary battery and prolong the life of the secondary battery.
  • the effect of service life that is, to improve the cycle performance of the secondary battery.
  • the capacity per unit area Cap A1 and Cap B1 of the positive film layers A1 and B1 satisfy 0.7 ⁇ Cap A1/Cap B1 ⁇ 1, optionally 0.7 ⁇ Cap A1/Cap B1 ⁇ 0.99, 0.8 ⁇ Cap A1/Cap B1 ⁇ 0.99, 0.7 ⁇ Cap A1/Cap B1 ⁇ 0.95, further optionally 0.7 ⁇ Cap A1/Cap B1 ⁇ 0.8.
  • the ratio of the capacity per unit area Cap A1 and Cap B1 of the positive electrode film layers A1 and B1 is within a given range, the capacity in the positive electrode film layer B1 pre-stored in the positive electrode sheet in the initial state can be regulated, thereby further improving the secondary capacity.
  • the cycle performance of the battery can be regulated, thereby further improving the secondary capacity.
  • the negative electrode film layer opposite to the positive electrode film layer A1 separated by a separator is A2, and the capacity per unit area Cap A2 and Cap A1 of the negative electrode film layer A2 and the positive electrode film layer A1 satisfy 1.02 ⁇ Cap A2/Cap A1 ⁇ 1.2, optionally 1.02 ⁇ Cap A2/Cap A1 ⁇ 1.1.
  • the ratio of the capacity per unit area Cap A2 and Cap A1 of the negative electrode film layer A2 and the positive electrode film layer A1 is within a given range, it can be ensured that the negative electrode film layer A2 does not decompose lithium, thereby improving the safety performance of the secondary battery.
  • the negative electrode film layer opposite to the positive electrode film layer B1 separated by a separator is B2, and the capacity per unit area Cap B2 and Cap B1 of the negative electrode film layer B2 and the positive electrode film layer B1 satisfy max(Cap A1/Cap B1, (Cap B1+Cap A1-Cap A2)/Cap B1) ⁇ Cap B2/Cap B1 ⁇ 1.
  • max(Cap A1/Cap B1, (Cap B1+Cap A1-Cap A2)/Cap B1) means taking the larger value of Cap A1/Cap B1 and (Cap B1+Cap A1-Cap A2) By.
  • the ratio of the capacity per unit area Cap B2 and Cap B1 of the negative electrode film layer B2 to the positive electrode film layer B1 is within a given range, the amount of negative electrode active material can be reduced while ensuring that the negative electrode film layer B2 does not decompose lithium, thereby improving Energy density of secondary batteries.
  • the secondary battery includes a positive pole piece 100, a negative pole piece 200 and a separator 300 placed between the positive pole piece and the negative pole piece
  • the positive pole piece 100 includes a positive current collector and is respectively arranged on The positive electrode film layers A1 and B1 on the two surfaces of the positive electrode current collector
  • the negative electrode sheet 200 includes the negative electrode current collector and the negative electrode film layers respectively arranged on the two surfaces of the negative electrode current collector
  • the positive electrode film layer A1 is separated by a layer of separator film
  • the negative electrode film layer opposite to each other is A2, and the negative electrode film layer opposite to the positive electrode film layer B1 separated by a separator is B2.
  • At least one through hole 202 is provided on the negative electrode current collector 201 of the negative electrode sheet, and the negative electrode film layers on both surfaces of the negative electrode current collector can be communicated through the through hole 202 .
  • the capacity per unit area of positive electrode film layer and negative electrode film layer can be determined respectively by following method: determine the quality of active material in positive electrode film layer or negative electrode film layer per unit area; Determine the gram capacity of the active material of positive electrode film layer or negative electrode film layer, for example Adopt methods such as button cell testing; multiply the mass by the gram capacity to obtain the capacity per unit area of the positive electrode film layer or the negative electrode film layer.
  • the shape of the through hole is not particularly limited, and may be a rectangle, a square, a circle, an ellipse, a polygon, and the like.
  • the ratio of the area of the through hole to the area of the negative electrode collector is 0.2%-40%, optionally 0.5-20%.
  • the ratio of the area of the through hole to the area of the negative electrode current collector is within the given range, the production processability of the negative electrode sheet and the conduction effect of lithium ions on the AB surface of the negative electrode film layer can be taken into account.
  • the diameter of the through hole is 5-500 ⁇ m, optionally 50-250 ⁇ m.
  • both the strength of the negative electrode sheet and the uniformity of the current density of the negative electrode sheet can be taken into account.
  • the shape of the through hole is a non-circular hole, the pore diameter when it is regarded as a circular hole can be calculated equivalently according to the area of the hole ⁇ the thickness of the substrate.
  • the positive electrode sheet has a compacted density of 2.0-3.6 g/cc, optionally 2.3-3.5 g/cc.
  • the negative electrode sheet has a compacted density of 0.5-2 g/cc, optionally 1.0-1.8 g/cc.
  • two negative electrode sheets, one positive electrode sheet, and two separators are assembled into a single-layer laminated cell, and a separator and the first copper layer are inserted between the positive electrode film layer A1 and the negative electrode film layer A2.
  • a separator and a second copper wire are inserted between the positive electrode film layer B1 and the negative electrode film layer B2, and the single-layer laminated cell is injected with an electrolyte solution and formed to plate lithium on the copper wire, and then at 25 ° C for the first week
  • a secondary battery is provided.
  • a secondary battery typically includes a positive pole piece, a negative pole piece, an electrolyte, and a separator.
  • active ions are intercalated and extracted back and forth between the positive electrode and the negative electrode.
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the separator is arranged between the positive pole piece and the negative pole piece, which mainly plays a role in preventing the short circuit of the positive and negative poles, and at the same time allows ions to pass through.
  • the positive electrode sheet includes a positive electrode collector and a positive electrode film layer arranged on at least one surface of the positive electrode collector, and the positive electrode film layer includes a positive electrode active material.
  • the positive electrode current collector has two opposing surfaces in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposing surfaces of the positive electrode current collector.
  • the positive electrode current collector can be a metal foil or a composite current collector.
  • aluminum foil can be used as the metal foil.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalic acid It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene glycol ester
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode active material may be a positive electrode active material known in the art for batteries.
  • the positive active material may include at least one of the following materials: olivine-structured lithium-containing phosphate, lithium transition metal oxide, and their respective modified compounds.
  • the present application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials of batteries can also be used. These positive electrode active materials may be used alone or in combination of two or more.
  • lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxides (such as LiNiO 2 ), lithium manganese oxides (such as LiMnO 2 , LiMn 2 O 4 ), lithium Nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1/3 Co 1/3 Mn 1/3 O 2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (also abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (also abbreviated as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (also abbreviated as NCM 622 ), LiNi At least one of 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM 811 )), lithium nickel cobalt aluminum oxide (such as LiN
  • olivine-structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also abbreviated as LFP)), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), phosphoric acid At least one of a composite material of lithium manganese and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also abbreviated as LFP)
  • composite materials of lithium iron phosphate and carbon such as LiMnPO 4
  • LiMnPO 4 lithium manganese phosphate
  • phosphoric acid At least one of a composite material of lithium manganese and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.
  • the positive electrode active material is a sodium ion positive electrode material, such as transition metal oxides, polyanionic compounds, and Prussian blue compounds.
  • the positive active material is LFP or NCM 523 .
  • the positive electrode film layer may further optionally include a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), polyimide (PI), vinylidene fluoride-tetrafluoroethylene-propylene At least one of meta-copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PAA polyacrylic acid
  • PI polyimide
  • vinylidene fluoride-tetrafluoroethylene-propylene At least one of meta-copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene
  • the binder is polyvinylidene fluoride (PVDF), polyacrylic acid (PAA), polytetrafluoroethylene (PTFE), or polyimide (PI).
  • PVDF polyvinylidene fluoride
  • PAA polyacrylic acid
  • PTFE polytetrafluoroethylene
  • PI polyimide
  • the positive electrode film layer may also optionally include a conductive agent.
  • the conductive agent may include at least one of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the conductive agent is at least one of graphite, carbon black, acetylene black, graphene and carbon nanotubes.
  • the positive electrode sheet can be prepared in the following manner: the above-mentioned components used to prepare the positive electrode sheet, such as positive electrode active material, conductive agent, binder and any other components, are dispersed in a solvent (such as N -Methylpyrrolidone (NMP)) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • a solvent such as N -Methylpyrrolidone (NMP)
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two opposing surfaces in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposing surfaces of the negative electrode current collector.
  • the negative electrode current collector can use a metal foil or a composite current collector.
  • copper foil can be used as the metal foil.
  • the composite current collector may include a base layer of polymer material and a metal layer formed on at least one surface of the base material of polymer material.
  • Composite current collectors can be formed by metal materials (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyethylene terephthalic acid It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • the negative electrode active material can be a negative electrode active material known in the art for batteries.
  • the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, graphene, carbon nanotubes, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material may be selected from at least one of simple tin, tin oxide compounds and tin alloys.
  • the present application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials of batteries can also be used. These negative electrode active materials may be used alone or in combination of two or more.
  • the negative electrode active material is at least one of natural graphite, artificial graphite, graphene, carbon nanotubes, soft carbon, and hard carbon.
  • the negative electrode active material is at least one of natural graphite and artificial graphite.
  • the negative electrode film layer may further optionally include a binder.
  • the binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer may also optionally include a conductive agent.
  • the conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode film layer may optionally include other additives, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • thickeners such as sodium carboxymethylcellulose (CMC-Na)
  • CMC-Na sodium carboxymethylcellulose
  • the negative electrode sheet can be prepared in the following manner: the above-mentioned components used to prepare the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.
  • a solvent such as deionized water
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the present application has no specific limitation on the type of electrolyte, which can be selected according to requirements.
  • electrolytes can be liquid, gel or all solid.
  • the electrolyte is an electrolytic solution.
  • the electrolyte solution includes an electrolyte salt and a solvent.
  • the electrolyte salt may be selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, trifluoromethane At least one of lithium sulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium difluorooxalate borate, lithium difluorodifluorooxalatephosphate and lithium tetrafluorooxalatephosphate.
  • the solvent may be selected from ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, Butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate At least one of ester, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte may optionally include additives.
  • additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performances of the battery, such as additives that improve battery overcharge performance, additives that improve high-temperature or low-temperature performance of batteries, and the like.
  • a separator is further included in the secondary battery.
  • the present application has no particular limitation on the type of the isolation membrane, and any known porous structure isolation membrane with good chemical stability and mechanical stability can be selected.
  • the material of the isolation film can be selected from polyolefin (such as polyethylene, polypropylene), polyester, polyimide, polyamide, cellulose, glass fiber, non-woven fabric and polyvinylidene fluoride at least one of the
  • the separator can be a single-layer film or a multi-layer composite film, without any particular limitation.
  • the separator is a multilayer composite film, the materials of each layer may be the same or different, and there is no particular limitation.
  • the isolation film is a polyolefin film, a polyester film, a polyimide film, a polyamide film, or a cellulose film.
  • the separator is a polyethylene film or a polypropylene film.
  • the positive pole piece, the negative pole piece and the separator can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer package.
  • the outer package can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard case, such as a hard plastic case, aluminum case, steel case, and the like.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft case may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • FIG. 3 shows a square-shaped secondary battery 5 as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plates enclose to form an accommodating cavity.
  • the housing 51 has an opening communicating with the accommodating cavity, and the cover plate 53 can cover the opening to close the accommodating cavity.
  • the positive pole piece, the negative pole piece and the separator can be formed into an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the accommodating cavity. Electrolyte is infiltrated in the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • the secondary battery can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.
  • FIG. 5 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 may be fixed by fasteners.
  • the battery module 4 may also include a case having a housing space in which a plurality of secondary batteries 5 are accommodated.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3 , the upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application.
  • the secondary battery, battery module, or battery pack can be used as a power source of the electric device, and can also be used as an energy storage unit of the electric device.
  • the electric devices may include mobile devices (such as mobile phones, notebook computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, etc.) , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but not limited thereto.
  • a secondary battery, a battery module or a battery pack can be selected according to its use requirements.
  • FIG. 8 is an example of an electrical device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or a battery module may be used.
  • the electric device may be a mobile phone, a tablet computer, a notebook computer, and the like.
  • the electrical device is usually required to be light and thin, and a secondary battery can be used as a power source.
  • the positive electrode film layer A1 On one surface of the positive electrode current collector Al foil, after drying at room temperature, dry at 110°C for 2 hours, and cold press to obtain the positive electrode film layer A1, which has a thickness of 87 ⁇ m, a compacted density of 2.4 g/cm 3 , and a capacity per unit area It is 33.2Ah/m 2 ; the positive electrode active material LFP, the conductive agent SP, and the binder PVDF are mixed uniformly in the solvent NMP at a mass ratio of 97:1:2 to obtain the second positive electrode slurry, and the second positive electrode slurry is uniformly Coated on the other surface of the positive electrode current collector, dried at room temperature, dried at 110°C for 2 hours, and cold pressed to obtain the positive electrode film layer B1 with a thickness of 108 ⁇ m and a compacted density of 2.4 g/cm 3 , the capacity per unit area is 41.5Ah/m 2 ; and then cut to obtain a positive electrode sheet of 87cm ⁇
  • Negative electrode active material artificial graphite, conductive agent SP, binder SBR are mixed uniformly in deionized water by mass ratio 97: 1: 2, obtain the first negative electrode slurry, the first negative electrode slurry is evenly coated on a thickness of 6 ⁇ m On one surface of the Cu foil of the negative electrode current collector, after drying at room temperature, dry at 110°C for 2 hours, and cold press to obtain the negative electrode film layer A2, which has a thickness of 59 ⁇ m and a compacted density of 1.65 g/cm 3 .
  • the capacity is 36.5Ah/m 2 ; the negative electrode active material artificial graphite, the conductive agent SP, and the binder SBR are mixed uniformly in deionized water at a mass ratio of 97:1:2 to obtain the second negative electrode slurry, and the second negative electrode slurry
  • the material is uniformly coated on the other surface of the negative electrode current collector, dried at room temperature, then dried at 110°C for 2 hours, and cold-pressed to obtain the negative electrode film layer B2, which has a thickness of 67 ⁇ m and a compacted density of 1.65 g/ cm 3 , the capacity per unit area is 41.5Ah/m 2 ; and then cut to obtain a 93cm ⁇ 320cm negative electrode sheet, wherein the negative electrode current collector has about 9.5*10 6 circular through holes with a diameter of 200 ⁇ m, accounting for The proportion of the negative electrode current collector is 10%.
  • the isolation film is a 9 ⁇ m polyethylene isolation film.
  • EMC ethylmethyl carbonate
  • DEC diethyl carbonate
  • EC ethylene carbonate
  • a layer of isolation film is set opposite to each other, and then wound to obtain a bare cell. Place the bare cell in the outer packaging foil, inject the above-mentioned electrolyte into the dried battery, and go through processes such as vacuum packaging, standing, forming, and shaping to obtain a secondary battery.
  • the preparation of the secondary battery refers to Example 1 as a whole, the difference is that in the preparation of the positive electrode sheet, the positive electrode active material in the first positive electrode slurry and the second positive electrode slurry is replaced by NCM 523 , and the positive electrode film is obtained by cold pressing Layer A1 has a thickness of 51 ⁇ m, a compacted density of 3.3 g/cm 3 , and a capacity per unit area of 33.2 Ah/m 2 ; cold-pressed positive electrode film layer B1 has a thickness of 64 ⁇ m and a compacted density of 3.3 g/cm 3 , the capacity per unit area is 41.5Ah/m 2 .
  • the preparation of the secondary battery refers to Example 1 as a whole, the difference is that in the preparation of the positive electrode sheet, the positive electrode active material LFP in the first positive electrode slurry remains unchanged, and the positive electrode film layer A1 is obtained by cold pressing, and its thickness is 87 ⁇ m, the compacted density is 2.4g/cm 3 , and the capacity per unit area is 33.2Ah/m 2 ; the positive electrode active material in the second positive electrode slurry is replaced by NCM 523 , and the positive electrode film layer B1 is obtained by cold pressing, and its thickness is 64 ⁇ m , the compacted density is 3.3g/cm 3 , and the capacity per unit area is 41.5Ah/m 2 .
  • the preparation of the secondary battery refers to Example 1 as a whole, the difference is that in the preparation of the negative electrode sheet, the negative electrode active material in the first negative electrode slurry and the second negative electrode slurry is replaced with natural graphite, and the negative electrode film is obtained by cold pressing Layer A2 has a thickness of 59 ⁇ m, a compacted density of 1.6 g/cm 3 , and a capacity per unit area of 36.5 Ah/m 2 ; the cold-pressed negative electrode film layer B2 has a thickness of 67 ⁇ m and a compacted density of 1.6 g/cm 3 , the capacity per unit area is 41.5Ah/m 2 .
  • the preparation of the secondary battery refers to Example 1 as a whole.
  • the difference is that in the preparation of the negative electrode sheet, the negative electrode active material in the first negative electrode slurry remains unchanged, and the negative electrode film layer A2 is obtained by cold pressing, and its thickness is 59 ⁇ m.
  • the compacted density is 1.65g/cm 3 , and the capacity per unit area is 36.5Ah/m 2 ; the negative electrode active material in the second negative electrode slurry is replaced by natural graphite, and the negative electrode film layer B2 is obtained by cold pressing, with a thickness of 67 ⁇ m.
  • the solid density is 1.6g/cm 3 , and the capacity per unit area is 41.5Ah/m 2 .
  • the preparation of the secondary battery is generally referred to in Example 1, except that the thicknesses of the positive electrode film layer B1 and the negative electrode film layer B2 are 124 ⁇ m and 77 ⁇ m, respectively.
  • the preparation of the secondary battery is generally referred to in Example 1, except that the thicknesses of the positive electrode film layer B1 and the negative electrode film layer B2 are 91 ⁇ m and 57 ⁇ m, respectively.
  • the preparation of the secondary battery is generally referred to in Example 1, except that the thicknesses of the positive electrode film layer B1 and the negative electrode film layer B2 are 144 ⁇ m and 89 ⁇ m, respectively.
  • the preparation of the secondary battery is generally referred to in Example 1, except that the thickness of the negative electrode film layer A2 is 55 ⁇ m.
  • the preparation of the secondary battery is generally referred to in Example 1, except that the thickness of the negative electrode film layer A2 is 64 ⁇ m.
  • the preparation of the secondary battery is generally referred to in Example 1, except that the thickness of the negative electrode film layer A2 is 57 ⁇ m.
  • the preparation of the secondary battery is generally referred to in Example 1, except that the thickness of the negative electrode film layer A2 is 70 ⁇ m.
  • the preparation of the secondary battery is generally referred to in Example 1, except that the thickness of the negative electrode film layer B2 is 62 ⁇ m.
  • the preparation of the secondary battery is generally referred to in Example 1, except that the thickness of the negative electrode film layer B2 is 64 ⁇ m.
  • the preparation of the secondary battery is generally referred to in Example 1, the difference is that the diameter of the through holes is 200 ⁇ m, the number is 1.9*10 7 circular through holes, and the proportion of the negative electrode current collector is 20%.
  • the preparation of the secondary battery is generally referred to in Example 1, the difference is that the diameter of the through holes is 200 ⁇ m, the number is 4.8*10 5 circular through holes, and the proportion of the negative electrode current collector is 0.5%.
  • the preparation of the secondary battery refers to Example 1 as a whole, the difference is that in the preparation of the positive electrode sheet, the first positive electrode slurry is coated on both surfaces of the positive electrode current collector, and the positive electrode film layer is obtained by cold pressing, the thickness of which is is 87 ⁇ m, the compacted density is 2.4g/cm 3 , and the capacity per unit area is 33.2Ah/m 2 ; in the preparation of the negative electrode sheet, the first negative electrode slurry is coated on both surfaces of the negative electrode current collector, and the cold The negative electrode film layer was obtained by pressing, with a thickness of 59 ⁇ m, a compacted density of 1.65 g/cm 3 , a capacity per unit area of 36.5 Ah/m 2 , and no through holes on the negative electrode current collector.
  • Adopt the button cell test method to determine the gram capacity of the active material of the positive electrode film layer or the negative electrode film layer; determine the quality of the active material in the positive electrode film layer or the negative electrode film layer per unit area; multiply the gram capacity by the quality It is the capacity per unit area of the positive electrode film layer or the negative electrode film layer.
  • Button battery test method The active material powder is made into a single-sided coated pole piece, assembled with a lithium sheet to form a button battery, and the button capacity is obtained by charging and discharging at a rate of 0.1C.
  • the gram capacity parameter is obtained by dividing the capacity by the mass of the pole piece active material, which can accurately evaluate the gram capacity parameter of the positive and negative active materials.
  • the storage ratio of electricity 1-(charge capacity in the first week/(Cap A1+Cap A2)).
  • the charging cut-off voltage of lithium iron phosphate positive secondary battery is 4.0V
  • the charging cut-off voltage of lithium iron phosphate positive secondary battery is 4.0V
  • the secondary battery after 1000 cycles of the above cycle was disassembled, and the surface morphology of the negative electrode sheet was observed by a metallographic optical microscope (Axio Observer Z1M) magnified 1000 times to observe whether lithium dendrites were formed.
  • Example 1 and Example 6 to Example 8 comprehensively, when the ratio Cap A1/Cap B1 of the capacity per unit area of the positive electrode film layer A1 and B1 is greater than or equal to 0.7 and less than 1, the capacity of the secondary battery can be further improved by 80%. Number of cycles and capacity retention after 1000 cycles.
  • Example 1 when the ratio of the area of the through hole on the negative electrode current collector to the area of the negative electrode current collector is 0.2-40%, the capacity of the secondary battery is 80% cycle number and The capacity retention rate after 1000 cycles is good.
  • the present application is not limited to the above-mentioned embodiments.
  • the above-mentioned embodiments are merely examples, and within the scope of the technical solutions of the present application, embodiments that have substantially the same configuration as the technical idea and exert the same effects are included in the technical scope of the present application.
  • various modifications conceivable by those skilled in the art are added to the embodiments, and other forms constructed by combining some components in the embodiments are also included in the scope of the present application. .

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Abstract

本申请提供了一种二次电池，包括正极极片、负极极片和置于所述正极极片与所述负极极片之间的隔离膜，所述正极极片包括正极集流体和分别设置在所述正极集流体两个表面上的正极膜层A1和B1，所述负极极片包括负极集流体和分别设置在所述负极集流体两个表面上的负极膜层，其中所述正极膜层A1和B1的单位面积容量Cap A1和Cap B1满足Cap A1＜Cap B1，并且所述负极极片的所述负极集流体上设置有至少一个通孔。本申请还涉及包含所述二次电池的电池模块、电池包和用电装置。

Description

一种长寿命二次电池及电池模块、电池包和用电装置 技术领域
本申请涉及二次电池技术领域，尤其涉及一种长寿命二次电池、电池模块、电池包和用电装置。
背景技术
近年来，随着二次电池的应用范围越来越广泛，二次电池广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。由于二次电池取得了极大的发展，因此对其能量密度、循环性能和安全性能等也提出了更高的要求。
提升二次电池的循环性能，不仅可以降低成本，还可以减少回收二次电池导致的环保压力，具有非常重要的意义。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种二次电池，所述二次电池具有改善的循环性能和安全性能。
为了达到上述目的，本申请提供了一种二次电池以及电池模块、电池包和用电装置。
本申请的第一方面提供了一种二次电池，包括正极极片、负极极片和置于所述正极极片与所述负极极片之间的隔离膜，
所述正极极片包括正极集流体和分别设置在所述正极集流体两个表面上的正极膜层A1和B1，所述负极极片包括负极集流体和分别设置在所述负极集流体两个表面上的负极膜层，
其中所述正极膜层A1和B1的单位面积容量Cap A1和Cap B1满足Cap A1＜Cap B1，并且所述负极极片的所述负极集流体上设置有至少一个通孔。
由此，本申请通过调控正极极片两侧正极膜层的容量比值，进一步采用在负极集流体上打孔的方式，达到减缓二次电池衰减、延长使用寿命的效果，即改善二次电池的循环性能。
在任意实施方式中，所述正极膜层A1和B1的单位面积容量Cap A1和Cap B1满足0.7≤Cap A1/Cap B1＜1。当正极膜层A1和B1的单位面积容量Cap A1和Cap B1的比值在给定范围内时，能够进一步改善二次电池的循环性能。
在任意实施方式中，与所述正极膜层A1间隔一层隔离膜相对设置的负极膜层为A2，所述负极膜层A2和所述正极膜层A1的单位面积容量Cap A2和Cap A1满足1.02≤Cap A2/Cap A1≤1.2。当负极膜层A2和正极膜层A1的单位面积容量Cap A2和Cap A1的比值在给定范围内时，能够改善二次电池的安全性能。
在任意实施方式中，与所述正极膜层B1间隔一层隔离膜相对设置的负极膜层为B2，所述负极膜层B2与所述正极膜层B1的单位面积容量Cap B2和Cap B1满足max(Cap A1/Cap B1，(Cap B1+Cap A1-Cap A2)/Cap B1)≤Cap B2/Cap B1≤1。当负极膜层B2与正极膜层B1的单位面积容量Cap B2和Cap B1的比值在给定范围内时，可以在保证负极膜层B2不析锂的情况下，降低负极活性材料用量，从而提升二次电池的能量密度。
在任意实施方式中，所述通孔的面积占所述负极集流体的面积的比例为0.2％-40％。当所述通孔的面积占所述负极集流体的面积的比例在所给范围内时，可以兼顾负极极片生产加工性以及负极膜层AB面的锂离子导通效果。
在任意实施方式中，所述通孔的孔径为5-500μm，可选为50-250μm。当所述通孔的孔径在所给范围内时，可以兼顾负极极片强度以及负极极片电流密度均匀性。
在任意实施方式中，所述正极极片的压实密度为2.0-3.6g/cc，可选为2.3-3.5g/cc。
在一些实施方式中，所述负极极片的压实密度为0.5-2g/cc，可 选为1.0-1.8g/cc。
本申请的第二方面提供一种电池模块，所述电池模块包括本申请的第一方面的二次电池。
本申请的第三方面提供一种电池包，所述电池包包括本申请的第二方面的电池模块。
本申请的第四方面提供一种用电装置，所述用电装置包括选自本申请的第一方面的二次电池、本申请的第二方面的电池模块或本申请的第三方面的电池包中的至少一种。
本申请的电池模块、电池包和用电装置包括本申请的二次电池，因而至少具有与所述二次电池相同的优势。
附图说明
图1是本申请一实施方式的二次电池的电芯的示意图。
图2是本申请一实施方式的二次电池的负极极片的示意图。
图3是本申请一实施方式的二次电池的示意图。
图4是图3所示的本申请一实施方式的二次电池的分解图。
图5是本申请一实施方式的电池模块的示意图。
图6是本申请一实施方式的电池包的示意图。
图7是图6所示的本申请一实施方式的电池包的分解图。
图8是本申请一实施方式的二次电池用作电源的用电装置的示意图。
附图标记说明：
1电池包；2上箱体；3下箱体；4电池模块；5二次电池；51壳体；52电极组件；53顶盖组件；100正极极片；200负极极片；300隔离膜；201负极集流体；202通孔
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的二次电池、电池模块、电池包和用电装置的实施方式。但是会有省略不必要的详 细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放 式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
随着二次电池应用场景的普及和拓宽，对二次电池使用寿命的需求逐年提升。提升二次电池的循环性能，不仅可以实现降低成本的目的，而且还可以减少二次电池回收导致的环保压力，具有非常重要的意义。
当前为了增加二次电池的使用寿命，一般采用以下措施：(1)改善活性材料的表面包覆，减小表面副反应；(2)提高导电物质含量，降低电阻；(3)减小电池使用区间等。但是这些措施无不带来高昂的成本提升和技术挑战。
经过大量实验，本申请发明人发现当调整正极极片两侧正极膜层的容量比值，并结合在负极集流体上打孔的方式，可以补充充放电过程中的活性锂消耗，从而达到减缓二次电池衰减、延长其使用寿命的效果。
本申请的一个实施方式中，本申请提出了一种二次电池，包括正极极片、负极极片和置于所述正极极片与所述负极极片之间的隔离膜，
所述正极极片包括正极集流体和分别设置在所述正极集流体两个表面上的正极膜层A1和B1，所述负极极片包括负极集流体和分别设置在所述负极集流体两个表面上的负极膜层，
其中所述正极膜层A1和B1的单位面积容量Cap A1和Cap B1满足Cap A1＜Cap B1，并且所述负极极片的所述负极集流体上设置有至少一个通孔。
虽然机理尚不清楚，本申请发明人推测是由于以下原因：本申请通过调控正极极片两侧正极膜层的容量比值，实现将二次电池中的活 性锂预存在正极极片中的效果；进一步采用在负极集流体上打孔的方式，正极极片中预存的活性锂可以在使用过程中缓慢转移到负极极片中，最终释放出来补充体系活性锂消耗，达到减缓二次电池衰减、延长使用寿命的效果，即改善二次电池的循环性能。
在一些实施方式中，所述正极膜层A1和B1的单位面积容量Cap A1和Cap B1满足0.7≤Cap A1/Cap B1＜1，可选地0.7≤Cap A1/Cap B1≤0.99，0.8≤Cap A1/Cap B1≤0.99，0.7≤Cap A1/Cap B1≤0.95，进一步可选地0.7≤Cap A1/Cap B1≤0.8。当正极膜层A1和B1的单位面积容量Cap A1和Cap B1的比值在给定范围内时，可以调控初始状态下，预存在正极极片的正极膜层B1中的容量，从而进一步改善二次电池的循环性能。
在一些实施方式中，与所述正极膜层A1间隔一层隔离膜相对设置的负极膜层为A2，所述负极膜层A2和所述正极膜层A1的单位面积容量Cap A2和Cap A1满足1.02≤Cap A2/Cap A1≤1.2，可选地1.02≤Cap A2/Cap A1≤1.1。当负极膜层A2和正极膜层A1的单位面积容量Cap A2和Cap A1的比值在给定范围内时，可以确保负极膜层A2不析锂，从而改善二次电池的安全性能。
在一些实施方式中，与所述正极膜层B1间隔一层隔离膜相对设置的负极膜层为B2，所述负极膜层B2与所述正极膜层B1的单位面积容量Cap B2和Cap B1满足max(Cap A1/Cap B1，(Cap B1+Cap A1-Cap A2)/Cap B1)≤Cap B2/Cap B1≤1。
需要说明的是，max(Cap A1/Cap B1，(Cap B1+Cap A1-Cap A2)/Cap B1)表示取Cap A1/Cap B1和(Cap B1+Cap A1-Cap A2)所得数值中的大者。
当负极膜层B2与正极膜层B1的单位面积容量Cap B2和Cap B1的比值在给定范围内时，可以在保证负极膜层B2不析锂的情况下，降低负极活性材料用量，从而提升二次电池的能量密度。
如图1所示，所述二次电池包括正极极片100、负极极片200和置于正极极片与负极极片之间的隔离膜300，正极极片100包括正极 集流体和分别设置在正极集流体两个表面上的正极膜层A1和B 1，负极极片200包括负极集流体和分别设置在负极集流体两个表面上的负极膜层，与正极膜层A1间隔一层隔离膜相对设置的负极膜层为A2，与正极膜层B1间隔一层隔离膜相对设置的负极膜层为B2。
如图2所示，在负极极片的负极集流体201上设置有至少一个通孔202，负极集流体两个表面上的负极膜层可通过通孔202连通。
正极膜层和负极膜层的单位面积容量各自可通过如下方法确定：确定单位面积正极膜层或负极膜层中活性材料的质量；确定正极膜层或负极膜层的活性材料的克容量，例如采用扣式电池测试等方法；将所述质量乘以所述克容量，即得到正极膜层或负极膜层的单位面积容量。
在本申请实施例中，对通孔的形状没有特别的限制，可以为矩形、方形、圆形、椭圆形、多边形等。
在本申请实施例中，当负极极片的负极集流体上设置有多于一个通孔时，对通孔的排列方式没有特别的限制。
在一些实施方式中，所述通孔的面积占所述负极集流体的面积的比例为0.2％-40％，可选地为0.5-20％。当所述通孔的面积占所述负极集流体的面积的比例在所给范围内时，可以兼顾负极极片生产加工性以及负极膜层AB面的锂离子导通效果。
在一些实施方式中，所述通孔的孔径为5-500μm，可选为50-250μm。当所述通孔的孔径在所给范围内时，可以兼顾负极极片强度以及负极极片电流密度均匀性。当通孔形状属于非圆形孔时，可以按照孔面积×基材厚度等效计算其视同为圆形孔时的孔径。
在一些实施方式中，所述正极极片的压实密度为2.0-3.6g/cc，可选为2.3-3.5g/cc。
在一些实施方式中，所述负极极片的压实密度为0.5-2g/cc，可选为1.0-1.8g/cc。
在一些实施方式中，将两片负极极片、一片正极极片和两片隔离膜组装成单层叠片电芯，在正极膜层A1和负极膜层A2之间插入一 片隔离膜和第一铜丝，在正极膜层B1和负极膜层B2之间插入一片隔离膜和第二铜丝，对该单层叠片电芯注入电解液后化成以对铜丝镀锂，然后在25℃下首周充电过程中检测第一铜丝与负极膜层A2之间的电压v1，第二铜丝与负极膜层B2之间的电压v2，v1与v2之间的小者满足min(v1，v2)＞-20mV。通过该方法，第一可以确定不会有析锂风险，第二检验是否符合产品特征。
另外，以下适当参照附图对本申请的二次电池、电池模块、电池包和用电装置进行说明。
本申请的一个实施方式中，提供一种二次电池。
通常情况下，二次电池包括正极极片、负极极片、电解质和隔离膜。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。
[正极极片]
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，所述正极膜层包括正极活性材料。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，所述正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极活性材料可采用本领域公知的用于电池的正极活性材料。作为示例，正极活性材料可包括以下材料中的至少 一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM 333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM 523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM 211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM 622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM 811))、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化合物等中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO 4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的至少一种。
在一些实施方式中，正极活性材料为钠离子正极材料，例如过渡金属氧化物、聚阴离子化合物和普鲁士蓝类化合物。
在一些实施方式中，正极活性材料为LFP或NCM 523。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、聚丙烯酸(PAA)、聚酰亚胺(PI)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，所述粘结剂为聚偏氟乙烯(PVDF)、聚丙烯酸(PAA)、聚四氟乙烯(PTFE)或聚酰亚胺(PI)。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，所述导电剂可以包括石墨、超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，所述导电剂为石墨、炭黑、乙炔黑、石墨烯 和碳纳米管中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮(NMP))中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、石墨烯、碳纳米管、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。所述硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。所述锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方案中，负极活性材料为天然石墨、人造石墨、石墨烯、碳纳米管、软碳和硬碳中的至少一种。
在一些实施方案中，负极活性材料为天然石墨和人造石墨中的至少一种。
在一些实施方式中，负极膜层还可选地包括粘结剂。所述粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施方式中，所述电解质采用电解液。所述电解液包括电解质盐和溶剂。
在一些实施方式中，电解质盐可选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
在一些实施方式中，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸 乙酯、1，4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
在一些实施方式中，所述电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
[隔离膜]
在一些实施方式中，二次电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可选自聚烯烃(如聚乙烯、聚丙烯)、聚酯、聚酰亚胺、聚酰胺、纤维素、玻璃纤维、无纺布及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，隔离膜为聚烯烃膜、聚酯膜、聚酰亚胺膜、聚酰胺膜或纤维素膜。
在一些实施方式中，隔离膜为聚乙烯膜或聚丙烯膜。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图3是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图4，外包装可包括壳体51和盖板53。 其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图5是作为一个示例的电池模块4。参照图5，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图6和图7是作为一个示例的电池包1。参照图6和图7，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
另外，本申请还提供一种用电装置，所述用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。所述二次电池、电池模块、或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以包括移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、 电动卡车等)、电气列车、船舶及卫星、储能系统等，但不限于此。
作为所述用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图8是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的用电装置可以是手机、平板电脑、笔记本电脑等。该用电装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
实施例1
[正极极片的制备]
将正极活性材料LFP、导电剂SP、粘结剂PVDF按质量比97∶1∶2在溶剂NMP中混合均匀，得到第一正极浆料，将第一正极浆料均匀涂布在厚度为13μm的正极集流体Al箔的一个表面上，在室温下晾干后，在110℃下干燥2h，冷压得到正极膜层A1，其厚度为87μm，压实密度为2.4g/cm 3，单位面积容量为33.2Ah/m 2；将正极活性材料LFP、导电剂SP、粘结剂PVDF按质量比97∶1∶2在溶剂NMP中混合均匀，得到第二正极浆料，将第二正极浆料均匀涂布在所述正极集流体的另一个表面上，在室温下晾干后，在110℃下干燥2h，冷压得到正极膜层B1，其厚度为108μm，压实密度为2.4g/cm 3，单位面积容量为41.5Ah/m 2；然后进行分切，得到87cm×200cm的正极极片。
[负极极片的制备]
将负极活性材料人造石墨、导电剂SP、粘结剂SBR按质量比97∶ 1∶2在去离子水中混合均匀，得到第一负极浆料，将第一负极浆料均匀涂布在厚度为6μm的负极集流体Cu箔的一个表面上，在室温下晾干后，在110℃下干燥2h，冷压得到负极膜层A2，其厚度为59μm，压实密度为1.65g/cm 3，单位面积容量为36.5Ah/m 2；将负极活性材料人造石墨、导电剂SP、粘结剂SBR按质量比97∶1∶2在去离子水中混合均匀，得到第二负极浆料，将第二负极浆料均匀涂布在所述负极集流体的另一个表面上，在室温下晾干后，在110℃下干燥2h，冷压得到负极膜层B2，其厚度为67μm，压实密度为1.65g/cm 3，单位面积容量为41.5Ah/m 2；然后进行分切，得到93cm×320cm负极极片，其中所述负极集流体具有约9.5*10 6个圆形通孔，其孔径为200μm，占所述负极集流体的比例为10％。
[隔离膜]
隔离膜为9μm聚乙烯隔离膜。
[电解液的制备]
将碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸亚乙酯(EC)按质量比5∶2∶3进行混合，得到有机溶剂，将充分干燥的电解质盐LiPF 6溶解于上述溶剂中，电解质盐的浓度为1mol/L，混合均匀后得到电解液。
[二次电池的制备]
将一片正极极片、两片隔离膜、一片负极极片按顺序叠好，使正极膜层A1与负极膜层A2隔着一层隔离膜相对设置，正极膜层B1与负极膜层B2隔着一层隔离膜相对设置，然后卷绕得到裸电芯。将裸电芯置于外包装箔中，将上述电解液注入到干燥后的电池中，经过真空封装、静置、化成、整形等工序，获得二次电池。
实施例2
二次电池的制备整体上参照实施例1，区别在于：在正极极片的制备中，将第一正极浆料和第二正极浆料中的正极活性材料替换为NCM 523，冷压得到正极膜层A1，其厚度为51μm，压实密度为3.3g/cm 3，单位面积容量为33.2Ah/m 2；冷压得到正极膜层B1，其厚度 为64μm，压实密度为3.3g/cm 3，单位面积容量为41.5Ah/m 2。
实施例3
二次电池的制备整体上参照实施例1，区别在于，在正极极片的制备中，将第一正极浆料中的正极活性材料LFP保持不变，冷压得到正极膜层A1，其厚度为87μm，压实密度为2.4g/cm 3，单位面积容量为33.2Ah/m 2；将第二正极浆料中的正极活性材料替换为NCM 523，冷压得到正极膜层B1，其厚度为64μm，压实密度为3.3g/cm 3，单位面积容量为41.5Ah/m 2。
实施例4
二次电池的制备整体上参照实施例1，区别在于，在负极极片的制备中，将第一负极浆料和第二负极浆料中的负极活性材料替换为天然石墨，冷压得到负极膜层A2，其厚度为59μm，压实密度为1.6g/cm 3，单位面积容量为36.5Ah/m 2；冷压得到负极膜层B2，其厚度为67μm，压实密度为1.6g/cm 3，单位面积容量为41.5Ah/m 2。
实施例5
二次电池的制备整体上参照实施例1，区别在于，在负极极片的制备中，第一负极浆料中的负极活性材料保持不变，冷压得到负极膜层A2，其厚度为59μm，压实密度为1.65g/cm 3，单位面积容量为36.5Ah/m 2；将第二负极浆料中的负极活性材料替换为天然石墨，冷压得到负极膜层B2，其厚度为67μm，压实密度为1.6g/cm 3，单位面积容量为41.5Ah/m 2。
实施例6
二次电池的制备整体上参照实施例1，区别在于，正极膜层B1和负极膜层B2的厚度分别为124μm和77μm。
实施例7
二次电池的制备整体上参照实施例1，区别在于，正极膜层B1和负极膜层B2的厚度分别为91μm和57μm。
实施例8
二次电池的制备整体上参照实施例1，区别在于，正极膜层B1 和负极膜层B2的厚度分别为144μm和89μm。
实施例9
二次电池的制备整体上参照实施例1，区别在于，负极膜层A2的厚度为55μm。
实施例10
二次电池的制备整体上参照实施例1，区别在于，负极膜层A2的厚度为64μm。
实施例11
二次电池的制备整体上参照实施例1，区别在于，负极膜层A2的厚度为57μm。
实施例12
二次电池的制备整体上参照实施例1，区别在于，负极膜层A2的厚度为70μm。
实施例13
二次电池的制备整体上参照实施例1，区别在于，负极膜层B2的厚度为62μm。
实施例14
二次电池的制备整体上参照实施例1，区别在于，负极膜层B2的厚度为64μm。
实施例15
二次电池的制备整体上参照实施例1，区别在于，通孔的孔径为200μm，个数为1.9*10 7个圆形通孔，占所述负极集流体的比例为20％。
实施例16
二次电池的制备整体上参照实施例1，区别在于，通孔的孔径为200μm，个数为4.8*10 5个圆形通孔，占所述负极集流体的比例为0.5％。
对比例1
二次电池的制备整体上参照实施例1，区别在于，在正极极片的制备中，将第一正极浆料涂敷在正极集流体的两个表面上，冷压得到正极膜层，其厚度为87μm，压实密度为2.4g/cm 3，单位面积容量为 33.2Ah/m 2；在负极极片的制备中，将第一负极浆料涂覆在负极集流体的两个表面上，冷压得到负极膜层，其厚度为59μm，压实密度为1.65g/cm 3，单位面积容量为36.5Ah/m 2，并且负极集流体上没有通孔。
极片和二次电池的性能测试
1.正极膜层和负极膜层的单位面积容量
采用扣式电池测试方法，确定正极膜层或负极膜层的活性材料的克容量；确定单位面积的正极膜层或负极膜层中活性材料的质量；将所述克容量乘以所述质量即为正极膜层或负极膜层的单位面积容量。
扣式电池测试方法：将活性材料粉末制作成单面涂布的极片，与锂片组装成扣式电池，通过0.1C倍率充放电得到扣电容量。充放电过程中的电压上下限，对于LFP正极活性材料：2.5-4.05V，对于NCM 523正极活性材料：2.5-4.35V，对于负极活性材料：0.005-2V。将容量除以极片活性材料质量得到克容量参数，可准确评估正负极活性材料的克容量参数。
2.正极极片的藏电比例
将二次电池在25℃下以1mA·cm -2的恒定电流充电至4.3V，之后以4.3V恒压充电至电流降到0.3mA·cm -2，得到首周充电容量C1，正极极片的藏电比例＝1-(首周充电容量/(Cap A1+Cap A2))。
其中磷酸铁锂正极二次电池的充电截止电压为4.0V
3.二次电池循环性能测试
将二次电池在25℃下以1.5mA·cm -2的恒定电流充电至4.3V，之后以4.3V恒压充电至电流降到0.3mA·cm -2，再以1.5mA·cm -2的恒定电流放电至2.5V，得到首周放电比容量(Cd1)；如此反复充放电至第n周，得二次电池循环n周后的放电比容量，记为Cdn。按照下式计算二次电池的容量保持率：容量保持率＝循环n周后的放电比容量(Cdn)/首周放电比容量(Cd1)；并记录容量剩余80％时二次电池循环的周数。
其中磷酸铁锂正极二次电池的充电截止电压为4.0V
4.负极极片析锂
将上述循环1000周后的二次电池拆解，通过金相光学显微镜(Axio Observer Z1M)放大1000倍观察负极极片的表面形貌，观察是否有锂枝晶生成。
按照上述过程分别测试上述实施例和对比例，具体数值参见表1。
Figure PCTCN2022074932-appb-000001
Figure PCTCN2022074932-appb-000002
由表1可知，上述所有实施例的二次电池的容量80％循环圈数和循环1000周容量保持率均高于对比例的二次电池。此外，所有实施例的二次电池均没有析锂。
综合比较实施例1至实施例5，相比于对比例1，通过调控正极极片两侧正极膜层的容量比值并在负极集流体上打孔，对二次电池的循环性能有明显改善。
综合比较实施例1和实施例6至实施例8，当正极膜层A1和B1的单位面积容量的比值Cap A1/Cap B1大于等于0.7且小于1时，能够进一步改善二次电池的容量80％循环圈数和循环1000周容量保持率。
综合比较实施例1和实施例9至实施例12，当负极膜层A2和正极膜层A1的单位面积容量的比值Cap A2/Cap A1为1.02-1.2时，能够进一步改善二次电池的循环性能。
综合比较实施例1和实施例13至实施例14，当负极膜层B2和正极膜层B1的单位面积容量的比值Cap B2/Cap B1满足max(Cap A1/Cap B1，(Cap B1+Cap A1-Cap A2)/Cap B1)≤Cap B2/Cap B1≤1时，能够进一步改善二次电池的容量80％循环圈数和循环1000周容量保持率。
综合比较实施例1和实施例15至实施例16，当负极集流体上的通孔的面积占负极集流体的面积的比例为0.2-40％时，二次电池的容量80％循环圈数和循环1000周容量保持率均较佳。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (11)

  1. 一种二次电池，包括正极极片、负极极片和置于所述正极极片与所述负极极片之间的隔离膜，
    所述正极极片包括正极集流体和分别设置在所述正极集流体两个表面上的正极膜层A1和B1，所述负极极片包括负极集流体和分别设置在所述负极集流体两个表面上的负极膜层，
    其中所述正极膜层A1和B1的单位面积容量Cap A1和Cap B1满足Cap A1＜Cap B1，并且所述负极极片的所述负极集流体上设置有至少一个通孔。
  2. 根据权利要求1所述的二次电池，其中所述正极膜层A1和B1的单位面积容量Cap A1和Cap B1满足0.7≤Cap A1/Cap B1＜1。
  3. 根据权利要求1或2所述的二次电池，其中与所述正极膜层A1间隔一层隔离膜相对设置的负极膜层为A2，所述负极膜层A2和所述正极膜层A1的单位面积容量Cap A2和Cap A1满足1.02≤Cap A2/Cap A1≤1.2。
  4. 根据权利要求1至3中任一项所述的二次电池，其中与所述正极膜层B1间隔一层隔离膜相对设置的负极膜层为B2，所述负极膜层B2与所述正极膜层B1的单位面积容量Cap B2和Cap B1满足max(Cap A1/Cap B1，(Cap B1+Cap A1-Cap A2)/Cap B1)≤Cap B2/Cap B1≤1。
  5. 根据权利要求1至4中任一项所述的二次电池，其中所述通孔的面积占所述负极集流体的面积的比例为0.2％-40％。
  6. 根据权利要求1至5中任一项所述的二次电池，其中所述通 孔的孔径为5-500μm，可选为50-250μm。
  7. 根据权利要求1至6中任一项所述的二次电池，其中所述正极极片的压实密度为2.0-3.6g/cc，可选为2.3-3.5g/cc。
  8. 根据权利要求1至7中任一项所述的二次电池，其中所述负极极片的压实密度为0.5-2g/cc，可选为1.0-1.8g/cc。
  9. 一种电池模块，其中所述电池模块包括权利要求1至8中任一项所述的二次电池。
  10. 一种电池包，其中所述电池包包括权利要求9所述的电池模块。
  11. 一种用电装置，其中所述用电装置包括选自权利要求1至8中任一项所述的二次电池、权利要求9所述的电池模块或权利要求10所述的电池包中的至少一种。
PCT/CN2022/074932 2022-01-29 2022-01-29 一种长寿命二次电池及电池模块、电池包和用电装置 WO2023142024A1 (zh)

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