WO2023050834A1 - 一种二次电池、含有其的电池模块、电池包及用电装置 - Google Patents

一种二次电池、含有其的电池模块、电池包及用电装置 Download PDF

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WO2023050834A1
WO2023050834A1 PCT/CN2022/094330 CN2022094330W WO2023050834A1 WO 2023050834 A1 WO2023050834 A1 WO 2023050834A1 CN 2022094330 W CN2022094330 W CN 2022094330W WO 2023050834 A1 WO2023050834 A1 WO 2023050834A1
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negative electrode
film layer
secondary battery
electrode film
battery
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PCT/CN2022/094330
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English (en)
French (fr)
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陈斌溢
王家政
柳娜
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宁德时代新能源科技股份有限公司
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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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • 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 secondary battery, a battery module containing the same, 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.
  • 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.
  • winding batteries have more and more usage scenarios.
  • the cycle of winding structure batteries if the internal stress is too large, it will cause winding The two ends of the wound cell are broken, which may even cause safety problems.
  • the first aspect of the present application provides a secondary battery, including a wound-type electric core
  • the wound-type electric core includes: a negative electrode sheet, the negative electrode sheet includes a negative electrode current collector, and the negative electrode current collector includes a first surface and the second surface opposite to the first surface, the first surface is located on the side away from the center of the wound electric core, and the second surface is located on the side close to the center of the wound electric core;
  • the first negative electrode film layer is arranged on the negative electrode assembly On the first surface of the fluid;
  • the second negative electrode film layer is arranged on the second surface of the negative electrode current collector;
  • the first negative electrode film layer and the second negative electrode film layer both include negative electrode active materials, and the negative electrode active materials all include carbon materials.
  • the OI value of one negative electrode film layer is denoted as OI 1
  • the OI value of the second negative electrode film layer is denoted as OI 2 ;
  • the secondary battery satisfies: OI 1 ⁇ OI 2 .
  • a secondary battery provided by this application has a differentiated design for the negative pole piece, so as to reduce the stress accumulation on the outside of the pole piece and avoid the phenomenon that the pole piece is broken at the corner, so that the secondary battery can take into account better cycle at the same time performance and safety features.
  • OI 1 and OI 2 satisfy the relationship: 1.05 ⁇ OI 2 /OI 1 ⁇ 1.4; alternatively, 1.15 ⁇ OI 2 /OI 1 ⁇ 1.3.
  • OI 1 and OI 2 satisfy the relationship: 5 ⁇ OI 2 -OI 1 ⁇ 20.
  • the first negative electrode film layer and the second negative electrode film layer also include a silicon material
  • the mass ratio of the silicon material in the negative electrode active material in the first negative electrode film layer is denoted as CA
  • the silicon material in the second negative electrode film layer is The mass proportion of the material in the negative electrode active material is recorded as CB, and the secondary battery satisfies: CA ⁇ CB.
  • 8% ⁇ CA ⁇ 32% optionally, 10% ⁇ CA ⁇ 15%; and/or 9% ⁇ CB ⁇ 33%, optionally, 11% ⁇ CB ⁇ 16%.
  • the number of winding core layers of the wound electric core is greater than 20, and may be 21-120.
  • the expansion coefficient of the first negative electrode film layer is ⁇ 1
  • the expansion coefficient of the second negative electrode film layer is ⁇ 2
  • the secondary battery satisfies: ⁇ 2 / ⁇ 1 ⁇ 1.022; optionally, 1.005 ⁇ ⁇ 2 / ⁇ 1 ⁇ 1.02.
  • 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 electrical device, including at least one selected from the secondary battery of the first aspect of the present application, the battery module of the second aspect of the present application, or the battery pack of the third aspect of the present application. kind.
  • FIG. 1 is a schematic diagram of a negative pole piece of a wound-type electric core of the present application.
  • Fig. 2 is an enlarged view of the structure of the bending part of the negative pole piece of the wound-type electric core 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
  • a certain method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed in sequence, or may include steps (b) and (a) performed in sequence.
  • steps (a) and (b) performed in sequence, or may include steps (b) and (a) performed in sequence.
  • a certain method may also include step (c), means that step (c) can be added to the method in any order, for example, the above method may include steps (a), (b) and (c), and may also include steps (a), (c) and (b), may also include steps (c), (a) and (b) and the like.
  • 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).
  • Secondary batteries also known as rechargeable batteries or accumulators, refer to batteries that can be activated by charging the active materials and continue to be used after the battery is discharged.
  • a secondary battery usually includes a positive pole piece, a negative pole piece, a separator and an electrolyte.
  • active ions such as lithium ions
  • 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 active ions to pass through.
  • the electrolyte is between the positive pole piece and the negative pole piece, and mainly plays the role of conducting active ions.
  • the positive pole piece, the negative pole piece and the separator form a wound battery cell through a winding process.
  • FIG. 1 shows a schematic diagram of a negative pole piece of a wound battery of the present application.
  • the negative electrode sheet of the present application includes a negative electrode current collector 7, the negative electrode current collector 7 includes a first surface and a second surface opposite to the first surface, the first surface is located on the side of the wound-type electric core away from the center , the second surface is located on the side near the center of the winding type electric core; the first negative electrode film layer 6 is arranged on the first surface of the negative electrode current collector 7; the second negative electrode film layer 8 is arranged on the second surface of the negative electrode current collector 7 On the surface; the first negative electrode film layer 6 and the second negative electrode film layer 8 both include negative electrode active materials, and the negative electrode active materials all include carbon materials.
  • the OI value of the first negative electrode film layer 6 is denoted as OI 1
  • the second negative electrode film layer 8 The OI value is denoted as OI 2 ; the secondary battery satisfies: OI 1 ⁇ OI 2 .
  • the inventors found that, as exemplarily shown in Figure 2, the first negative electrode film layer 6 is a convex layer of the outer ring, which is subjected to a greater tension than the inner ring. There will be local stress imbalance at the bend of the battery cell, which will reduce the battery life.
  • the OI values on both sides of the battery cell to be different, the expansion of the battery cell in the thickness direction of the current collector 7 is reduced, and the cycle performance of the battery is enhanced.
  • OI 1 and OI 2 satisfy the relationship: 1.05 ⁇ OI 2 /OI 1 ⁇ 1.4; alternatively, 1.15 ⁇ OI 2 /OI 1 ⁇ 1.3.
  • OI 1 and OI 2 satisfy the relationship: 5 ⁇ OI 2 -OI 1 ⁇ 20.
  • the OI value of the negative electrode film layer is a well-known parameter in the art, and its size can be adjusted by known methods. For example, in the negative electrode sheet preparation process, it can be obtained by adjusting the compaction density of the negative electrode film layer. desired OI value.
  • the first negative electrode film layer 6 and the second negative electrode film layer 8 also include silicon material
  • the mass ratio of the silicon material in the negative electrode active material in the first negative electrode film layer 6 is denoted as CA
  • the second negative electrode film layer The mass proportion of the silicon material in the negative electrode active material in layer 8 is denoted as CB
  • the secondary battery satisfies: CA ⁇ CB.
  • the inventors have found that the tension on the first negative electrode film layer 6 is greater than that of the inner ring.
  • the silicon content CA added to the outer ring is smaller than the silicon content CB of the inner ring, especially when a specific relationship is met, the outer ring can be made to be perpendicular to the current collector 7
  • the absolute expansion of the plane direction is smaller than the absolute expansion of the inner ring along the direction perpendicular to the plane of the current collector 7, which can effectively balance the tension of the inner and outer rings, thereby improving the cycle performance of the battery.
  • the number of winding core layers of the wound electric core is greater than 20, and may be 21-120.
  • the tension gap between the inner and outer rings of the electric core is relatively large, and the beneficial effect brought by the application is also obvious.
  • the expansion coefficient of the first negative electrode film layer 6 is ⁇ 1
  • the expansion coefficient of the second negative electrode film layer 8 is ⁇ 2
  • the secondary battery satisfies: ⁇ 2 / ⁇ 1 ⁇ 1.022; optionally, 1.005 ⁇ 2 / ⁇ 1 ⁇ 1.02.
  • the negative electrode current collector 7 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, soft carbon, hard carbon, silicon-based material, tin-based material, 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 can be selected from at least one of simple tin, tin oxide and tin alloy.
  • 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 film layer may further optionally include a binder.
  • the binder may be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), At least one of polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer may also optionally include a conductive agent.
  • the conductive agent may 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 7, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.
  • a solvent such as deionized water
  • the positive electrode sheet generally includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current 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.
  • a metal foil or a composite current collector can be used as the positive electrode 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 LiNi
  • the olivine structure contains Examples of lithium phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also may be abbreviated as LFP)), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), lithium manganese phosphate and carbon At least one of a composite material, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also may be abbreviated as LFP)
  • composite materials of lithium iron phosphate and carbon such as LiMnPO 4
  • LiMnPO 4 lithium manganese phosphate and carbon
  • the positive electrode film layer may further optionally include a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of meta-copolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the positive electrode film layer may also optionally include a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • 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) 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
  • 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 liquid and 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 also optionally includes additives.
  • the additives may include negative film-forming additives, positive 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 the battery, 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 at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the separator can be a single-layer film or a multi-layer composite film, without any particular limitation. When 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 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 bag may be plastic, and examples of plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.
  • 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 are wound to form a winding battery core 52 .
  • the wound electric core 52 is packaged in the containing chamber.
  • the electrolyte solution impregnates the wound type cell 52 .
  • 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.
  • a secondary battery, a battery module, or a battery pack can be used as a power source of a power consumption device, and can also be used as an energy storage unit of the power consumption device.
  • Electric devices can include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but not limited thereto.
  • secondary batteries, battery modules, or battery packs can be selected according to their usage 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.
  • Preparation of positive pole piece Dissolve positive active material NCM 523 , conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) in a solvent N-methylpyrrolidone (NMP) in a weight ratio of 96.5:1.5:2 ), fully stirred and mixed to obtain the positive electrode slurry; then the positive electrode slurry was uniformly coated on the positive electrode current collector, and then dried, cold pressed, and cut to obtain the positive electrode sheet.
  • NMP N-methylpyrrolidone
  • Negative electrode slurry preparation mix artificial graphite, conductive agent acetylene black, thickener CMC, and binder SBR in a mass ratio of 96.4:1:1.2:1.4, add solvent deionized water, and mix to obtain negative electrode slurry;
  • Negative electrode sheet preparation apply the negative electrode slurry on both surfaces of the negative electrode current collector respectively, adjust the compaction density of the negative electrode film layers on both sides, so that the OI value of the first negative electrode film layer 6 is 50, and the second negative electrode film layer 8 has an OI value of 55.1.
  • Isolation film Polypropylene film is used.
  • Preparation of the secondary battery stack and wind the above-mentioned positive pole piece, separator, and negative pole piece in sequence to obtain a wound-type battery cell; put the wound-type battery cell into the outer packaging, and add the above-prepared The electrolyte solution is packaged, left to stand, formed, aged and other processes to obtain a secondary battery.
  • Examples 2-5 and Comparative Examples 1-2 are similar to the secondary battery preparation method of Example 1, but the OI values of the first negative electrode film layer 6 and the second negative electrode film layer 8 are adjusted respectively. For details of different product parameters, see Table 1.
  • the OI value of the negative electrode film layer has a meaning known in the art, and can be tested by methods known in the art. For example, it can be obtained by using an X-ray diffractometer (such as Bruker D8 Discover), according to the general rules of the X-ray diffraction analysis method and the lattice parameter determination method of graphite JIS K 0131-1996, JB/T4220-2011, to obtain the X-ray diffraction spectrum,
  • the OI value of the negative film layer C004/C110, wherein, C004 is the peak area of the diffraction peak of the 004 crystal plane, and C110 is the peak area of the diffraction peak of the 110 crystal plane.
  • the method for testing the OI value of the negative electrode film layer can be as follows: the prepared negative electrode sheet is directly placed in an X-ray powder diffractometer, and the peak area of the diffraction peak of the 004 crystal plane and the peak area of the 110 crystal plane are obtained by X-ray diffraction analysis. The peak area of the diffraction peak is used to obtain the OI value of the negative electrode film.
  • the 2 ⁇ angle corresponding to the 004 crystal plane of graphite is 53.5°-55.5° (eg 54.5°); the 2 ⁇ angle corresponding to the 110 crystal plane of graphite is 76.5°-78.5° (eg 77.4°).
  • the secondary batteries prepared in Examples 1-5 and Comparative Examples 1-2 were cycled at 45°C 1C/1C with a voltage of 2.8-4.2V. Before the cycle, the thickness of the fully charged battery was measured, the battery was equipped with a clamp, and a 5000N clamp was applied The force simulates the force exerted by the end plate on the battery during the assembly of the module, and then performs 1500 cycles with a clamp, removes the clamp, fully charges and stands for 12 hours, and measures the thickness change of the battery. Divide the thickness difference of the battery before and after the cycle by the thickness of the battery before the cycle and multiply by 100% to obtain the expansion rate of the battery.
  • the secondary battery was subjected to a full charge and full discharge cycle test at a rate of 1C until the capacity of the secondary battery decayed to 80% of the initial capacity, and the number of cycles was recorded.
  • Examples 1-5 effectively reduce the expansion rate of the battery, avoid the breakage of the accessories caused by the accumulation of external stress at the corner during the use of the battery, and improve the durability of the secondary battery. Safety performance and cycle life.
  • 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，包括卷绕型电芯，卷绕型电芯包括：负极极片，负极极片包括负极集流体，负极集流体包括第一表面和与第一表面相对的第二表面，第一表面位于卷绕型电芯远离中心的一面，第二表面位于卷绕型电芯靠近中心的一面；第一负极膜层，设置在负极集流体的第一表面上；第二负极膜层，设置在负极集流体的第二表面上；第一负极膜层和第二负极膜层均包括负极活性材料，负极活性材料均包括碳材料，第一负极膜层的OI值记为OI 1，第二负极膜层的OI值记为OI 2；二次电池满足：OI 1＜OI 2。

Description

一种二次电池、含有其的电池模块、电池包及用电装置
相关申请的交叉引用
本申请要求享有于2021年09月30日提交的名称为“一种二次电池、含有其的电池模块、电池包及用电装置”的中国专利申请202111165064.3的优先权，该申请的全部内容通过引用并入本文中。
技术领域
本申请涉及二次电池技术领域，具体涉及一种二次电池、含有其的电池模块、电池包及用电装置。
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。随着二次电池对续航里程的要求越来越高，卷绕型电芯有越来越多的使用场景，卷绕结构的电芯在其循环过程中，如果内应力过大，会导致卷绕型电芯两端弯折处断裂，甚至会引发安全问题。
如何使电池同时兼顾较好的电性能和安全性能，仍是亟待解决的问题。
发明内容
为了达到上述目的，本申请的第一方面提供一种二次电池，包括卷 绕型电芯，卷绕型电芯包括：负极极片，负极极片包括负极集流体，负极集流体包括第一表面和与第一表面相对的第二表面，第一表面位于卷绕型电芯远离中心的一面，第二表面位于卷绕型电芯靠近中心的一面；第一负极膜层，设置在负极集流体的第一表面上；第二负极膜层，设置在负极集流体的第二表面上；第一负极膜层和第二负极膜层均包括负极活性材料，负极活性材料均包括碳材料，第一负极膜层的OI值记为OI 1，第二负极膜层的OI值记为OI 2；二次电池满足：OI 1＜OI 2。
本申请提供的一种二次电池，对负极极片进行了差异化设计，从而降低极片外侧应力堆积，避免极片在拐角处附件断裂的现象，从而使得二次电池同时兼顾较好的循环性能及安全性能。
在任意实施方式中，OI 1和OI 2满足关系式:1.05≤OI 2/OI 1≤1.4；可选地，1.15≤OI 2/OI 1≤1.3。
在任意实施方式中，OI 1和OI 2满足关系式:5＜OI 2-OI 1＜20。
在任意实施方式中，15≤OI 1≤80，可选为20≤OI 1≤60；和/或
25≤OI 2≤90，可选为30≤OI 2≤70。
在任意实施方式中，第一负极膜层和第二负极膜层还包括硅材料，第一负极膜层中硅材料在负极活性材料中的质量占比记为CA，第二负极膜层中硅材料在负极活性材料中的质量占比记为CB，则二次电池满足：CA＜CB。
在任意实施方式中，0.1％≤CB-CA≤1.0％，可选地，0.2％≤CB-CA≤0.5％。
在任意实施方式中，8％≤CA≤32％，可选地，10％≤CA≤15％；和/或9％≤CB≤33％，可选地，11％≤CB≤16％。
在任意实施方式中，卷绕型电芯的卷芯层数大于20，可选为21-120。
在任意实施方式中，第一负极膜层的膨胀系数为α 1，第二负极膜层的膨胀系数为α 2，则二次电池满足：α 2/α 1≤1.022；可选地，1.005≤α 2/α 1≤1.02。
本申请的第二方面提供一种电池模块，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，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，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。
附图说明
图1是本申请卷绕型电芯的负极极片示意图。
图2是本申请卷绕型电芯的负极极片弯折处结构放大图。
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盖板；6第一负极膜层；7集流体；8第二负极膜层。
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及其制造方法、正极极片、负极极片、电解液、隔离膜、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。例如，某种方法包括步骤(a)和(b)，表示该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，提到某种方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到方法，例如，上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，“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)。
[二次电池]
二次电池又称为充电电池或蓄电池，是指在电池放电后可通过充电的方式使活性材料激活而继续使用的电池。
二次电池通常包括正极极片、负极极片、隔离膜及电解液。在电池充放电过程中，活性离子(例如锂离子)在正极极片和负极极片之间往返嵌 入和脱出。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，同时可以使活性离子通过。电解液在正极极片和负极极片之间，主要起到传导活性离子的作用。
本申请的二次电池中，正极极片、负极极片和隔离膜通过卷绕工艺形成卷绕型电芯。
[负极极片]
图1示出了本申请卷绕型电芯的负极极片的示意图。如图1所示，本申请的负极极片包括负极集流体7，负极集流体7包括第一表面和与第一表面相对的第二表面，第一表面位于卷绕型电芯远离中心的一面，第二表面位于卷绕型电芯靠近中心的一面；第一负极膜层6，设置在负极集流体7的第一表面上；第二负极膜层8，设置在负极集流体7的第二表面上；第一负极膜层6和第二负极膜层8均包括负极活性材料，负极活性材料均包括碳材料，第一负极膜层6的OI值记为OI 1，第二负极膜层8的OI值记为OI 2；二次电池满足：OI 1＜OI 2。
经过大量研究后，发明人发现，如图2所示例性地示出的，第一负极膜层6为外圈凸面层，其受到的张力比内圈大，在电芯服役过程中，卷绕型电芯弯折处会出现局部应力不平衡的情况，降低电池寿命。本申请通过设置电芯两侧OI值不同，降低了电芯在集流体7厚度方向上的膨胀，增强了电池的循环性能。
在一些实施方式中，OI 1和OI 2满足关系式:1.05≤OI 2/OI 1≤1.4；可选地，1.15≤OI 2/OI 1≤1.3。
在一些实施方式中，OI 1和OI 2满足关系式:5＜OI 2-OI 1＜20。
在一些实施方式中，15≤OI 1≤80，可选为20≤OI 1≤60；和/或
25≤OI 2≤90，可选为30≤OI 2≤70。
需要说明的是，负极膜层的OI值是本领域的公知参数，可以通过已知的方法调整其大小，例如，在负极极片制备过程中，可以通过调整负极膜层的压实密度来获得所需的OI值。
在一些实施方式中，第一负极膜层6和第二负极膜层8还包括硅材料，第一负极膜层6中硅材料在负极活性材料中的质量占比记为CA，第二负极膜层8中硅材料在负极活性材料中的质量占比记为CB，则二次电池满足：CA＜CB。
在一些实施方式中，0.1％≤CB-CA≤1.0％，可选地，0.2％≤CB-CA≤0.5％。
在一些实施方式中，8％≤CA≤32％，可选地，10％≤CA≤15％。
在一些实施方式中，9％≤CB≤33％，可选地，11％≤CB≤16％。
发明人发现，第一负极膜层6受到的张力比内圈大，当外圈添加的硅含量CA小于内圈硅含量CB，尤其是还符合特定关系时，可以使外圈沿垂直于集流体7平面方向的绝对膨胀量小于内圈沿垂直于集流体7平面方向的绝对膨胀量，可以有效平衡内外圈的张力，从而改善电池的循环性能。
在一些实施方式中，卷绕型电芯的卷芯层数大于20，可选为21-120。当卷绕型电芯的卷芯层数在所给范围内时，电芯内外圈弯折处的张力差距也较大，本申请带来的有益效果也较明显。
在一些实施方式中，第一负极膜层6的膨胀系数为α 1，第二负极膜层8的膨胀系数为α 2，则二次电池满足：α 2/α 1≤1.022；可选地，1.005≤α 2/α 1≤1.02。
在一些实施方式中，负极集流体7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、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。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。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。
在一些实施方式中，负极膜层还可选地包括粘结剂。作为示例，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。作为示例，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7上，经烘干、冷压等工序后，即可得到负极极片。
[正极极片]
正极极片通常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，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，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，正极膜层还可选地包括粘结剂。作为示例，粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、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，正极膜层还可选地包括导电剂。作为示例，导电剂可以包括超导碳、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，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)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。
[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，电解质为液态的，且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，电解液还可选地包括添加剂。作为示例，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玻璃纤维、无纺布、聚乙烯、聚丙烯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，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能够盖设于开口，以封闭容纳腔。正极极片、负极极片和隔离膜经卷绕工艺形成卷绕型电芯52。卷绕型电芯52封装于容纳腔内。电解液浸润于卷绕型电芯52中。二次电池5所含卷绕型电芯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，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。二次电池、电池模块、或电池包可以用作用电装置的电源，也可以用作用电装置的能量存储单元。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。
[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
1、正极极片的制备：将正极活性材料NCM 523、导电剂乙炔黑、粘 结剂聚偏二氟乙烯(PVDF)按重量比为96.5:1.5:2溶于溶剂N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀后得到正极浆料；之后将正极浆料均匀涂覆于正极集流体上，之后经过烘干、冷压、分切，得到正极极片。
2、负极极片的制备：
负极浆料制备：将人造石墨、导电剂乙炔黑、增稠剂CMC、粘结剂SBR按质量比96.4:1:1.2:1.4混合，加入溶剂去离子水，混匀后获得负极浆料；
负极极片制备：将负极浆料分别涂覆在负极集流体的两个表面上，调整两面负极膜层的压实密度，使得第一负极膜层6的OI值为50，第二负极膜层8的OI值为55.1。
3、隔离膜：采用聚丙烯膜。
4、电解液的制备：将碳酸亚乙酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按体积比1:1:1混合，然后将LiPF 6均匀溶解在上述溶液中，得到电解液。该电解液中，LiPF 6的浓度为1mol/L。
5、二次电池的制备：将上述正极极片、隔离膜、负极极片按顺序堆叠并卷绕，得到卷绕型电芯；将卷绕型电芯放入外包装中，加入上述制备的电解液，经封装、静置、化成、老化等工序后，得到二次电池。
实施例2-5和对比例1-2与实施例1的二次电池制备方法相似，但是分别调整了第一负极膜层6和第二负极膜层8的OI值，不同的产品参数详见表1。
表1：实施例1-5与对比例1-2的参数结果
序号 OI 1 OI 2 OI 2/OI 1
实施例1 50.0 55.1 1.10
实施例2 50.0 58.0 1.16
实施例3 50.0 60.0 1.20
实施例4 50.0 65.0 1.30
实施例5 50.0 69.9 1.40
对比例1 50.0 50.0 1.00
对比例2 50.0 45.0 0.90
电池测试
(1)负极膜层的OI值测试
负极膜层的OI值为本领域公知的含义，可以采用本领域已知的方法测试。例如，可通过使用X射线衍射仪(如Bruker D8 Discover)得到，依据X射线衍射分析法通则以及石墨的点阵参数测定方法JIS K 0131-1996、JB/T4220-2011，得到X射线衍射图谱，负极膜层的OI值＝C004/C110，其中，C004为004晶面衍射峰的峰面积，C110为110晶面衍射峰的峰面积。具体地，负极膜层的OI值测试方法可以为：将制备好的负极极片直接置于X射线粉末衍射仪中，通过X射线衍射分析法得到004晶面衍射峰的峰面积以及110晶面衍射峰的峰面积，进而得到负极膜层的OI值。其中，石墨的004晶面所对应的2θ角为53.5°-55.5°(例如54.5°)；石墨的110晶面所对应的2θ角为76.5°-78.5°(例如77.4°)。
(2)电池厚度及膨胀率测试
对实施例1-5和对比例1-2制备的二次电池进行45℃1C/1C循环，电压2.8-4.2V，循环前测量满充下电池的厚度，电池带上夹具，施加5000N的夹具力模拟模组组装过程中端板对电池施加的力，然后进行带夹具循环1500圈，拆掉夹具，满充静置12h，测量电池的厚度变化。用循环 前后电池的厚度差除以循环前电池厚度并乘100％，即得到电池的膨胀率。
(3)循环性能测试
在25℃下，将二次电池以1C倍率进行满充、满放循环测试，直至二次电池的容量衰减至初始容量的80％，记录循环圈数。
表2：实施例1-5与对比例1-2的性能测试结果
序号 循环圈数 循环前电池厚度/mm 循环后电池厚度/mm 膨胀率
实施例1 2400 26.63 28.56 7.3％
实施例2 2450 26.6 28.44 6.9％
实施例3 2500 26.55 28.22 6.3％
实施例4 2460 26.61 28.47 7.0％
实施例5 2440 26.66 28.55 7.1％
对比例1 2000 26.49 29.67 12.0％
对比例2 1900 26.53 29.85 12.5％
根据上述结果可知，实施例1-5相较于对比例1-2，有效降低了电池的膨胀率，避免了在电池使用过程中拐角处因外侧应力堆积导致附件断裂，提高了二次电池的安全性能和循环寿命。
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 (12)

  1. 一种二次电池，包括卷绕型电芯，所述卷绕型电芯包括：
    负极极片，包括负极集流体，所述负极集流体包括第一表面和与第一表面相对的第二表面，所述第一表面位于所述卷绕型电芯远离中心的一面，所述第二表面位于所述卷绕型电芯靠近中心的一面；
    第一负极膜层，设置在所述第一表面上；
    第二负极膜层，设置在所述第二表面上；
    所述第一负极膜层和所述第二负极膜层均包括负极活性材料，所述负极活性材料均包括碳材料，所述第一负极膜层的OI值记为OI 1，所述第二负极膜层的OI值记为OI 2；
    所述二次电池满足：OI 1＜OI 2。
  2. 根据权利要求1所述的二次电池，其中，所述OI 1和所述OI 2满足关系式:1.05≤OI 2/OI 1≤1.4；可选地，1.15≤OI 2/OI 1≤1.3。
  3. 根据权利要求1或2所述的二次电池，其中，所述OI 1和所述OI 2满足关系式:5＜OI 2-OI 1＜20。
  4. 根据权利要求1-3任一项所述的二次电池，其中，
    15≤OI 1≤80，可选为20≤OI 1≤60；和/或
    25≤OI 2≤90，可选为30≤OI 2≤70。
  5. 根据权利要求1-4任一项所述的二次电池，其中，
    所述第一负极膜层和所述第二负极膜层还包括硅材料，所述第一负极膜层中硅材料在所述负极活性材料中的质量占比记为CA，所述第二负极膜层中硅材料在所述负极活性材料中的质量占比记为CB，则所述二次电池满足：CA＜CB。
  6. 根据权利要求5所述的二次电池，其中，
    0.1％≤CB-CA≤1.0％，可选地，0.2％≤CB-CA≤0.5％。
  7. 根据权利要求5或6所述的二次电池，其中，
    8％≤CA≤32％，可选地，10％≤CA≤15％；和/或
    9％≤CB≤33％，可选地，11％≤CB≤16％。
  8. 根据权利要求1-7任一项所述的二次电池，其中，
    所述卷绕型电芯的卷芯层数大于20，可选为21-120。
  9. 根据权利要求1-8任一项所述的二次电池，其中，
    所述第一负极膜层的膨胀系数为α 1，所述第二负极膜层的膨胀系数为α 2，则所述二次电池满足：α 2/α 1≤1.022；可选地，1.005≤α 2/α 1≤1.02。
  10. 一种电池模块，包括权利要求1-9任一项所述的二次电池。
  11. 一种电池包，包括权利要求10所述的电池模块。
  12. 一种用电装置，包括权利要求1-9任一项所述的二次电池、权利要求10所述的电池模块或权利要求11所述的电池包中的至少一种。
PCT/CN2022/094330 2021-09-30 2022-05-23 一种二次电池、含有其的电池模块、电池包及用电装置 WO2023050834A1 (zh)

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