WO2023097433A1 - 负极极片、二次电池、电池模块、电池包和用电装置 - Google Patents

负极极片、二次电池、电池模块、电池包和用电装置 Download PDF

Info

Publication number
WO2023097433A1
WO2023097433A1 PCT/CN2021/134346 CN2021134346W WO2023097433A1 WO 2023097433 A1 WO2023097433 A1 WO 2023097433A1 CN 2021134346 W CN2021134346 W CN 2021134346W WO 2023097433 A1 WO2023097433 A1 WO 2023097433A1
Authority
WO
WIPO (PCT)
Prior art keywords
thermal conductivity
negative electrode
low thermal
edge region
electrode sheet
Prior art date
Application number
PCT/CN2021/134346
Other languages
English (en)
French (fr)
Inventor
黄玉平
马云建
林明峰
喻鸿钢
来佑磊
李彦辉
代宇
张建平
Original Assignee
宁德时代新能源科技股份有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 宁德时代新能源科技股份有限公司 filed Critical 宁德时代新能源科技股份有限公司
Priority to CN202180092464.8A priority Critical patent/CN116802824A/zh
Priority to PCT/CN2021/134346 priority patent/WO2023097433A1/zh
Priority to EP21956260.0A priority patent/EP4213235A1/en
Priority to US18/119,832 priority patent/US20230246155A1/en
Publication of WO2023097433A1 publication Critical patent/WO2023097433A1/zh

Links

Images

Classifications

    • 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
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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
    • H01M4/663—Selection of materials containing carbon or carbonaceous materials as conductive part, e.g. graphite, carbon fibres
    • 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
    • H01M4/665—Composites
    • H01M4/667—Composites in the form of layers, e.g. coatings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
    • H01M50/204—Racks, modules or packs for multiple batteries or multiple cells
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of secondary batteries, in particular to a negative pole piece, a 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 or safety performance.
  • the present application is made in view of the above problems, and its purpose is to provide a negative electrode sheet, the negative electrode sheet includes a main body region and at least one low thermal conductivity edge region; the thermal conductivity of the low thermal conductivity edge region and the main body region The coefficients are ⁇ 2 and ⁇ 1 respectively, and ⁇ 2 ⁇ 1 .
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium deposition situation of the secondary battery, especially the lithium deposition situation in the edge region is effectively improved.
  • the ratio ⁇ 1 / ⁇ 2 of ⁇ 1 to ⁇ 2 is 1.1-1.5:1.
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the value of ⁇ 1 is 300-400 W/(m ⁇ K).
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the value of ⁇ 2 is 200-300 W/(m ⁇ K).
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the electrical conductivity coefficients of the low thermal conductivity edge region and the main body region are ⁇ 2 and ⁇ 1 respectively; the negative electrode sheet satisfies the kinetic coefficient Q>0, and the kinetic coefficient Q is given by the following formula calculate:
  • the negative electrode sheet satisfies a kinetic coefficient Q ⁇ 0.1.
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the ratio ⁇ 1 / ⁇ 2 of ⁇ 1 to ⁇ 2 is less than 1.3, optionally 1-1.3:1.
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the value of ⁇ 1 is 5.3 ⁇ 10 7 -5.9 ⁇ 10 7 ⁇ S ⁇ cm ⁇ 1 .
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the value of ⁇ 2 is 5.0 ⁇ 10 7 -5.3 ⁇ 10 7 ⁇ S ⁇ cm ⁇ 1 .
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the negative electrode sheet includes a current collector layer, and the thermal conductivity coefficients of the current collector layer belonging to the low thermal conductivity edge region and the current collector layer belonging to the main body region are ⁇ 21 and ⁇ respectively 11 , and ⁇ 21 ⁇ 11 .
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the negative electrode sheet includes an active material layer, and the thermal conductivity coefficients of the negative electrode active material layer belonging to the low thermal conductivity edge region and the negative electrode active material layer belonging to the main body region are ⁇ 23 and ⁇ 13 , and ⁇ 23 ⁇ 13 .
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the negative electrode sheet includes a current collector layer and an active material layer, wherein between the current collector layer belonging to the low thermal conductivity edge region and the active material layer belonging to the low thermal conductivity edge region A primer layer belonging to the low thermal conductivity edge region is also provided; the active material layer belonging to the body region is directly stacked on the current collector layer belonging to the body region (that is, there is no primer layer between the two. layer).
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the negative electrode sheet includes a current collector layer and an active material layer, wherein between the current collector layer belonging to the low thermal conductivity edge region and the active material layer belonging to the low thermal conductivity edge region An undercoat layer belonging to the low thermal conductivity edge area is also provided; a layer belonging to the main body area is also provided between the current collector layer belonging to the main body area and the active material layer belonging to the low thermal conductivity edge area.
  • the thermal conductivity coefficients of the undercoat layer belonging to the low thermal conductivity edge region and the undercoat layer belonging to the main body region are ⁇ 22 and ⁇ 12 respectively, and ⁇ 22 ⁇ 12 .
  • the undercoat layer belonging to the low thermal conductivity edge region contains a thermal resistance material
  • the undercoat layer belonging to the main body region contains conductive carbon black
  • the thermal conductivity of the thermal resistance material is lower than The conductive carbon black.
  • the primer layer belonging to the body region does not contain the thermal resistance material.
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the undercoat layer belonging to the main body region contains the thermal resistance material, but the content of the thermal resistance material in the undercoat layer belonging to the main body region is lower than that belonging to the low
  • the undercoating of the thermally conductive edge zone is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the primer layer belonging to the low thermal conductivity edge region contains the following components: conductive carbon black 50-60% by weight; thermal resistance material 5-15% by weight; and binder 30-40% by weight .
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the primer layer belonging to the main body region contains the following components: 60-70% by weight of conductive carbon black; and 30-40% by weight of binder.
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the thermal resistance material is one or more selected from the group consisting of gelatin, ammonium sulfate, ammonium chloride, thiourea and copper chloride.
  • the negative pole sheet based on this scheme is used in the secondary battery, and the lithium separation situation of the secondary battery, especially the lithium separation situation in the edge region is further improved.
  • the negative electrode sheet includes a first low thermal conductivity edge region and/or a second low thermal conductivity edge region, and the main body region includes a first long side and a second long side parallel to each other; the first The low thermal conductivity edge area is located outside the first long side of the main body area; the second low thermal conductivity edge area is located outside the second long side of the main body area.
  • the body region has an aspect ratio greater than 1, such as an aspect ratio greater than 2.
  • the outer side of the low thermal conductivity edge region is adjacent to the edge of the negative electrode sheet.
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the distance from the inner side of the low thermal conductivity edge region to the edge of the negative electrode sheet is w
  • the width of the negative electrode sheet is W
  • w 8mm-15mm.
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • W 100mm-200mm.
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • an outer side of one or more sides of the body region is provided with a low thermal conductivity edge region.
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the area of the body region accounts for 78.1-88.5% of the area of one side of the negative electrode sheet.
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the area of the low thermal conductivity edge region accounts for 11.5-21.9% of the area of one side of the negative electrode sheet.
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the area ratio of the main body region and the low thermal conductivity edge region is 3.6-7.7:1.
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • One embodiment of the present application provides a secondary battery, which includes an electrode assembly, and the electrode assembly includes the negative electrode sheet described in any one of the above.
  • An embodiment of the present application provides a battery module, including the secondary battery described in any one of the above.
  • An embodiment of the present application provides a battery pack, including the battery module described in any one of the above.
  • An embodiment of the present application provides an electrical device, including at least one selected from any of the above-mentioned secondary batteries, any of the above-mentioned battery modules, or any of the above-mentioned battery packs.
  • the negative pole piece is used in the secondary battery, and the lithium analysis situation of the secondary battery, especially the lithium analysis situation in the edge area is improved;
  • Fig. 1(a) shows a negative electrode sheet according to an embodiment of the present application
  • Fig. 1(b) shows an electrode assembly according to an embodiment of the present application.
  • Fig. 2(a) shows a negative electrode sheet according to another embodiment of the present application
  • Fig. 2(b) shows an electrode assembly according to another embodiment of the present application.
  • Fig. 3(a) shows a negative electrode sheet according to another embodiment of the present application
  • Fig. 3(b) shows an electrode assembly according to another embodiment of the present application.
  • Fig. 4 shows a negative electrode sheet according to another embodiment of the present application.
  • FIG. 5 show schematic diagrams of cross-sections of negative electrode sheets according to some embodiments of the present application.
  • FIG. 6 shows a perspective view of a secondary battery according to some embodiments of the present application
  • FIG. 6 shows an exploded view of a secondary battery according to an embodiment of the present application.
  • FIG. 7 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG. 8 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 9 is an exploded view of the battery pack according to one embodiment of the present application shown in FIG. 8 .
  • FIG. 10 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.
  • Negative electrode sheet 10 main body region 11; low thermal conductivity edge region 12; first low thermal conductivity edge region 121; second low thermal conductivity edge region 122; third low thermal conductivity edge region 123; fourth low thermal conductivity edge region 124; first long side 111; second long side 112; active material layer 22; primer layer 24; current collector layer 26;
  • battery pack 1 upper case 2; lower case 3; battery module 4; secondary battery 5; case 51; electrode assembly 52; tab 522; top cover assembly 53
  • 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 (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) , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b) and so on.
  • the “comprising” and “comprising” mentioned in this application mean 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).
  • 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 typically includes a positive pole piece, a negative pole piece, a separator, and an electrolyte.
  • active ions such as lithium ions
  • the separator is set between the positive pole piece and the negative pole piece, which mainly plays the role of preventing the short circuit of the positive and negative poles, and at the same time allows active ions to pass through.
  • the electrolyte mainly plays the role of conducting active ions between the positive pole piece and the negative pole piece.
  • the positive electrode sheet generally includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, and the positive electrode active material 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 active material 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 active material layer optionally further includes 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 active material layer may optionally further 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
  • FIG. 1 shows a negative electrode sheet according to one embodiment of the present application.
  • the present application provides a negative electrode sheet 10, the negative electrode sheet 10 includes a main body region 11 and a first low thermal conductivity edge region 121, the first low thermal conductivity edge region 121 and the main body
  • the thermal conductivities of the zones 11 are ⁇ 2a and ⁇ 1 , respectively, and ⁇ 2a ⁇ 1 .
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium deposition situation of the secondary battery, especially the lithium deposition situation in the edge region is effectively improved.
  • the first low thermal conductivity edge region 121 is located on one side of the main body region 11 .
  • FIG. 1 shows an electrode assembly according to one embodiment of the present application.
  • the electrode assembly 52 includes a winding core obtained by laminating and winding the negative electrode sheet 10 , the separator and the positive electrode sheet.
  • the electrode assembly 52 also includes a tab 522 mounted on one side of the negative pole piece.
  • the first low thermal conductivity edge region 121 is located on the side of the main body region 11 close to the tab 522 .
  • FIG. 2 shows a negative electrode sheet according to one embodiment of the present application.
  • the present application provides a negative electrode sheet 10, the negative electrode sheet 10 includes a main body region 11 and a second low thermal conductivity edge region 122, the second low thermal conductivity edge region 122 and the main body
  • the thermal conductivities of the zones 11 are ⁇ 2b and ⁇ 1 , respectively, and ⁇ 2b ⁇ 1 .
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium deposition situation of the secondary battery, especially the lithium deposition situation in the edge region is effectively improved.
  • the second low thermal conductivity edge region 122 is located on one side of the main body region 11 .
  • FIG. 2 shows an electrode assembly according to an embodiment of the present application.
  • the electrode assembly 52 includes tabs 522 .
  • the electrode assembly 52 includes a negative electrode sheet 10 , a separator, and a winding core obtained by laminating and winding the positive electrode sheet.
  • the electrode assembly 52 also includes a tab 522 mounted on one side of the negative pole piece.
  • the second low thermal conductivity edge region 122 is located on the side of the main body region 11 away from the tab 522 .
  • FIG. 3 shows a negative electrode sheet according to one embodiment of the present application.
  • the negative electrode sheet 10 includes a main body region 11 and a low thermal conductivity edge region 12, and the thermal conductivity coefficients of the low thermal conductivity edge region 12 and the main body region 11 are ⁇ 2 and ⁇ 1 , respectively, and ⁇ 2 ⁇ 1 .
  • the low thermal conductivity edge region 12 includes a first low thermal conductivity edge region 121 and a second low thermal conductivity edge region 122 .
  • the first low thermal conductivity edge region 121 and the second low thermal conductivity edge region 122 are respectively located on two sides of the main body region 11 .
  • the thermal conductivity coefficients of the first low thermal conductivity edge region 121 , the second low thermal conductivity edge region 122 and the main body region 11 are ⁇ 2a , ⁇ 2b and ⁇ 1 respectively, and ⁇ 2a ⁇ 1 , ⁇ 2b ⁇ 1 .
  • FIG. 3 shows an electrode assembly according to an embodiment of the present application.
  • the electrode assembly 52 includes a winding core obtained by stacking and winding the negative electrode sheet 10 , the separator and the positive electrode sheet.
  • the electrode assembly 52 also includes a tab 522 mounted on one side of the negative pole piece.
  • the first low thermal conductivity edge region 121 is located on the side of the main body region 11 close to the tab 522
  • the second low thermal conductivity edge region 122 is located on the side of the main body region 11 away from the tab 522 .
  • the present application sets the main body region 11 and at least one low thermal conductivity edge region 12 on the negative electrode sheet 10, and controls the thermal conductivity coefficients of the low thermal conductivity edge region 12 and the main body region 11 to be ⁇ 2 and ⁇ 1 respectively, and ⁇ 2 ⁇ ⁇ 1 , the negative pole piece is used in a secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is significantly improved.
  • the reason is that the thermal conductivity of the edge region with low thermal conductivity is different from that of the main region (the former is smaller than the latter), and the temperature of the edge region with low thermal conductivity is higher than that of the main region during battery operation, so that the dynamic performance of the edge region with low thermal conductivity is higher than that of the main region. , so as to improve the lithium separation window of the negative electrode, inhibit the lithium separation at the edge of the pole piece, and improve the cycle stability and safety of the battery.
  • the negative electrode sheet of the present application is used in a secondary battery, and the lithium analysis situation of the secondary battery, especially the lithium analysis situation in the edge area is effectively improved.
  • the reasons may be as follows:
  • the present application found that when a secondary battery (such as a lithium-ion battery) is charged, Li + is deintercalated from the positive electrode, and these Li + diffuse in the electrolyte to the surface of the negative electrode and are embedded in the negative electrode material.
  • a secondary battery such as a lithium-ion battery
  • Li + diffuse in the electrolyte to the surface of the negative electrode and are embedded in the negative electrode material.
  • some Li + cannot be smoothly inserted into the negative electrode material, so lithium deposition side reaction occurs on the surface of the negative electrode sheet, that is, lithium precipitation.
  • the present application also found that gaps tend to exist near the edge of the negative electrode sheet due to the winding process, which leads to preferential deposition of lithium at the edge of the negative electrode.
  • the present application creatively sets a low thermal conductivity edge region on the edge of the negative electrode sheet. Since the thermal conductivity of the low thermal conductivity edge region is relatively low, during the operation of the secondary battery, the temperature of the low thermal conductivity edge region Higher, which increases the rate of diffusion and intercalation of Li + in the edge region of low thermal conductivity, thereby improving the lithium precipitation in the edge region of the negative electrode, thereby improving the working performance of the secondary battery.
  • low thermal conductivity edge region in the term “low thermal conductivity edge region”, “low thermal conductivity” means that the thermal conductivity of the edge region is lower than that of the main region, that is, the ratio of the thermal conductivity of the two is less than 1. "Low thermal conductivity” does not indicate or imply what specific value the thermal conductivity of the edge region must be.
  • the main body region 11 is the region near the center of the negative electrode sheet 10
  • the low thermal conductivity edge region refers to the region located outside the main body region 11 and having a lower thermal conductivity than the main body region 11.
  • edge region and “low thermal conductivity edge region” may be used interchangeably.
  • the thermal conductivity is obtained according to the test "ISO 22007-2:2008 Determination of Thermal Conductivity of Materials by Transient Plane Heat Source Method".
  • the unit of thermal conductivity may be W/(m ⁇ K).
  • the measurement direction of the thermal conductivity can be chosen to be perpendicular to the surface direction of the negative electrode sheet (ie, the normal direction).
  • the ratio ⁇ 1 / ⁇ 2 of the thermal conductivity ⁇ 1 to ⁇ 2 is 1.1-1.5:1, optionally 1.2-1.4:1, such as 1-1.1:1, 1.1-1.2:1, 1.2-1.3:1, 1.3-1.4:1, 1.4-1.5:1.
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the value of the thermal conductivity ⁇ 1 is 300-400W/(m ⁇ K), such as 300-320W/(m ⁇ K), 320-340W/(m ⁇ K), 340-360W/(m ⁇ K), ⁇ K), 360-380W/(m ⁇ K) or 380-400W/(m ⁇ K).
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the value of thermal conductivity ⁇ 2 is 200-300W/(m ⁇ K), such as 200-220W/(m ⁇ K), 220-240W/(m ⁇ K), 240-260W/(m ⁇ K), ⁇ K), 260-280W/(m ⁇ K) or 280-300W/(m ⁇ K).
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the electrical conductivity coefficients of the low thermal conductivity edge region 12 and the main body region 11 are ⁇ 2 and ⁇ 1 respectively; the negative electrode sheet 10 satisfies the kinetic coefficient Q>0, and the kinetic coefficient Q Calculated by the following formula:
  • the negative electrode sheet 10 satisfies a kinetic coefficient Q ⁇ 0.1.
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the electrical conductivity is obtained by testing with reference to the standard "GB/T 11007-2008 Conductivity Meter Test Method".
  • the unit of conductivity may be ⁇ S ⁇ cm ⁇ 1 .
  • the measurement direction of the conductivity can be selected to be parallel to the negative pole piece.
  • the ratio ⁇ 1 / ⁇ 2 of the conductivity ⁇ 1 to ⁇ 2 is less than 1.3, optionally, ⁇ 1 / ⁇ 2 is 1-1.3:1, and optionally ⁇ 1 / ⁇ 2 is 1.1 -1.2:1.
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the conductivity coefficient ⁇ 1 has a value of 5.3 ⁇ 10 7 -5.9 ⁇ 10 7 ⁇ S ⁇ cm -1 , such as 5.3-5.5 ⁇ S ⁇ cm -1 , 5.5-5.7 ⁇ S ⁇ cm -1 , 5.7-5.9 ⁇ S ⁇ cm ⁇ 1 .
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the conductivity coefficient ⁇ 2 has a value of 5.0 ⁇ 10 7 -5.3 ⁇ 10 7 ⁇ S ⁇ cm -1 , for example, 5.1-5.2 ⁇ S ⁇ cm -1 .
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the negative electrode sheet 10 has a length direction L and a width direction D, and the size of the negative electrode sheet 10 in the length direction L is larger than its size in the width direction D.
  • Both the main body region 11 and the low thermal conductivity edge region 12 extend along the length direction L of the negative electrode sheet 10 .
  • the body region 11 includes a first long side 111 and a second long side 112 parallel to each other, and the negative electrode sheet 10 includes a first low thermal conductivity edge region 121 and/or a second long side 112 .
  • Low thermal conductivity edge area 122, the first low thermal conductivity edge area 121 is located outside the first long side of the main body area 11; the second low thermal conductivity edge area 122 is located outside the second long side of the main body area 11 outside.
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the outer side of the low thermal conductivity edge region 12 is adjacent to the edge of the negative electrode sheet 10 .
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the term "close to” includes that the outer side of the low thermal conductivity edge region completely coincides with the edge of the negative electrode sheet 10 , or there is only a distance of less than 5 mm (eg, less than 3 mm) between the two.
  • the distance from the inner side of the low thermal conductivity edge region 12 to the edge of the negative electrode sheet 10 is w (the distance from the inner side of the two low thermal conductivity edge regions to the edge of the negative electrode sheet 10 are respectively w1 and w2)
  • the width of the negative pole piece 10 is W
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the area of the main body region 11 accounts for 78.1-88.5% of the area of one side of the negative electrode sheet 10, such as 78.1-80.1%, 80.1-82.1%, 82.1-84.1%, 84.1% -86.1%, 86.1-88.1%.
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the area of the low thermal conductivity edge region 12 accounts for 11.5-21.9% of the area of one side of the negative electrode sheet 10, such as 11.5-13.5%, 13.5-15.5%, 15.5-17.5% , 17.5-19.5% or 19.5-21.5%.
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the ratio of the area of the main body region 11 to the low thermal conductivity edge region 12 is 3.6-7.7:1, such as 3.6-4.6:1, 4.6-5.6:1, 5.6-6.6:1 Or 6.6-7.6:1.
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • Figure 4 shows a negative electrode sheet of some embodiments of the present application.
  • a low thermal conductivity edge region 12 is provided outside one or more sides of the body region 11 .
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the negative electrode sheet 10 includes a body region 11 and a plurality of edge regions 12 with low thermal conductivity.
  • the body region 11 has a quadrangular shape.
  • the outer sides of the four sides of the main body area 11 are respectively provided with edge areas 12, which are the first low thermal conductivity edge area 121, the second low thermal conductivity edge area 122, the third low thermal conductivity edge area 123 and the fourth low thermal conductivity edge area 124. .
  • FIG. 5 show negative electrode sheets according to some embodiments of the present application.
  • an embodiment of the present application provides a negative electrode sheet 10, the negative electrode sheet 10 includes a main body region 11 and at least one low thermal conductivity edge region 12; the low thermal conductivity edge region 12 and the The thermal conductivity coefficients of the main body region 11 are respectively ⁇ 2 and ⁇ 1 , and ⁇ 2 ⁇ 1 .
  • FIG. 5 show cross-sectional views of the negative electrode tab 10 of some embodiments.
  • the negative electrode sheet 10 includes a current collector layer 26, and the thermal conductivity of the current collector layer 26 belonging to the low thermal conductivity edge region 12 and the current collector layer 26 belonging to the main body region 11 are respectively ⁇ 21 and ⁇ 11 , and ⁇ 21 ⁇ 11 .
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the negative electrode sheet 10 may further include an active material layer laminated with the current collector layer 26 .
  • the negative electrode sheet 10 includes an active material layer 22, the thermal conductivity of the negative electrode active material layer 22 belonging to the low thermal conductivity edge region 12 and the negative electrode active material layer 22 belonging to the main body region 11 are ⁇ 23 and ⁇ 13 respectively, and ⁇ 23 ⁇ 13 .
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the negative electrode sheet 10 may further include a current collector layer laminated with the active material layer.
  • the negative electrode sheet 10 includes a current collector layer 26 and an active material layer 22, wherein the current collector layer 26 belonging to the low thermal conductivity edge region 12 and the active material layer 26 belonging to the low thermal conductivity edge region 12
  • An undercoat layer 24 belonging to the low thermal conductivity edge region 12 is also provided between the material layers 22; the active material layer 22 belonging to the main body region 11 is directly stacked on the current collector layer 26 belonging to the main body region 11 (that is, there is no bottom between the two). Coating 24).
  • the negative electrode sheet based on this scheme is used in a secondary battery, and the lithium separation situation of the secondary battery, especially the lithium separation situation in the edge region is further improved.
  • the negative electrode sheet 10 includes a current collector layer 26 and an active material layer 22, wherein the current collector layer 26 belonging to the low thermal conductivity edge region 12 and the active material layer 26 belonging to the low thermal conductivity edge region 12
  • An undercoat layer 24 belonging to the low thermal conductivity edge region 12 is also provided between the material layers 22; a layer belonging to the main body region 11 is also provided between the current collector layer 26 belonging to the main body region 11 and the active material layer 22 belonging to the low thermal conductivity edge region 12.
  • the thermal conductivity coefficients of the undercoat layer 24 belonging to the low thermal conductivity edge region 12 and the undercoat layer 24 belonging to the main body region 11 are ⁇ 22 and ⁇ 12 , and ⁇ 22 ⁇ 12 .
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the undercoat layer 24 belonging to the low thermal conductivity edge region 12 contains a thermal resistance material
  • the undercoat layer 24 belonging to the main body region 11 contains conductive carbon black
  • the The thermal conductivity of the thermal resistance material is lower than that of the conductive carbon black.
  • the undercoat layer 24 belonging to the body region 11 does not contain the thermal resistance material.
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the undercoat layer 24 belonging to the main body region 11 contains the thermal resistance material, but the thermal resistance material in the undercoat layer 24 belonging to the main body region 11 The content of is lower than that of the primer layer 24 belonging to the low thermal conductivity edge region 12 .
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the primer layer 24 belonging to the low thermal conductivity edge region 12 contains the following components: conductive carbon black 50-60% by weight (for example, 53-55% by weight); thermal resistance material 5 - 15% by weight (such as 8-12% by weight, such as 10% by weight); and 30-40% by weight of binder (such as 31-34% by weight).
  • conductive carbon black 50-60% by weight for example, 53-55% by weight
  • thermal resistance material 5 - 15% by weight such as 8-12% by weight, such as 10% by weight
  • binder such as 31-34% by weight
  • the binder in the primer layer 24 belonging to the low thermal conductivity edge region 12 is styrene-butadiene rubber.
  • the primer layer 24 belonging to the low thermal conductivity edge region 12 further contains a dispersant in an amount of 0.01-0.1% by weight.
  • the dispersant is carboxymethylcellulose.
  • the primer layer 24 belonging to the body region 11 contains the following components: 60-70% by weight of conductive carbon black; and 30-40% by weight of binder.
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the binder in the primer layer 24 belonging to the body region 11 is styrene-butadiene rubber.
  • the undercoat layer 24 belonging to the body region 11 further contains 0.01-0.1% by weight of a dispersant.
  • the dispersant is carboxymethylcellulose.
  • the thermal resistance material is one or more selected from the group consisting of gelatin, ammonium sulfate, ammonium chloride, thiourea and copper chloride.
  • the negative electrode sheet based on this solution is used in the secondary battery, and the lithium desorption condition of the secondary battery, especially the lithium desorption condition in the edge region is further improved.
  • the negative electrode sheet is a negative electrode without a current collector.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, and the negative electrode active material 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 active material layer is disposed on any one or both of the two opposing surfaces of the negative electrode current collector.
  • a metal foil or a composite current collector can be used as the negative electrode 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 active material layer may optionally further 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 active material layer may optionally further 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 active material 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)
  • 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 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 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.
  • an embodiment of the present application provides a secondary battery, including an electrode assembly, and the electrode assembly includes the negative electrode sheet described in any one of the above.
  • FIG. 6 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 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.
  • 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.
  • an embodiment of the present application provides a battery module, including the secondary battery described in any one of the above.
  • FIG. 7 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.
  • an embodiment of the present application provides a battery pack, including the battery module described in any one of the above.
  • 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.
  • an embodiment of the present application provides an electrical device, including a battery selected from any of the above-mentioned secondary batteries, any of the above-mentioned battery modules, or any of the above-mentioned battery packs. at least one.
  • 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.
  • FIG. 10 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.
  • Copper foil was provided as the negative electrode collector, and the dimensions of the copper foil were as follows: thickness 6 ⁇ m, length 2545 mm, and width 183 mm.
  • First side primer coating the first side surface of the negative electrode current collector is divided into a main body area and two low thermal conductivity edge areas, the main body area and the two low thermal conductivity edge areas extend along the length direction of the negative electrode current collector, Two low thermal conductivity edge regions are respectively located on two sides of the long side of the main body region.
  • the size of the main body area is 2545mm ⁇ 163mm.
  • the dimensions of the two low thermal conductivity edge regions are 2545mm ⁇ 10mm, respectively.
  • the undercoating slurry in the main body area and the undercoating slurry in the low thermal conductivity edge area were coated on the main body area and the low thermal conductivity edge area respectively, with a coating thickness of 129 ⁇ m. Dry in an oven at 100°C for 6 hours after coating.
  • Coating the undercoating layer on the second side apply the undercoating layer on the second side surface of the negative electrode current collector by adopting the same partitioning and coating treatment as the first side surface.
  • the preparation method of negative active slurry is as follows: graphite/hard carbon, SBR (as binding agent) and CMC (as dispersant) are carried out proportioning by 97%: 1%: 2% by weight, and dilute with appropriate amount of distilled water, then Stir and mix in a vacuum mixer to form a uniform negative electrode active slurry.
  • Coating on the first side coating the negative electrode active slurry prepared in step (2) on the first side surface of the current collector with the undercoat layer. Dry in an oven at 100°C for 6 hours after coating.
  • the same negative electrode active slurry coating process as the first side is applied to the second side surface of the current collector with an undercoat layer. Dry in an oven at 100°C for 6 hours after coating.
  • the negative electrode sheet of Example 1 was obtained. Calculated on a single side, the loading capacity of the negative electrode active material is 0.160 g/1540.25 mm 2 .
  • the positive electrode active material LiNi 0.33 C0 0.33 Mn 0.33 O 2 , SP and PVDF are mixed according to 97%: 1.5%: 1.5% by weight, diluted with an appropriate amount of N-methylpyrrolidone, and then stirred in a vacuum mixer to form a uniform positive electrode active paste.
  • Aluminum foil was provided as the positive current collector.
  • the size of the positive electrode current collector is as follows: thickness 13 ⁇ m, length 2460 mm, width 179 mm.
  • the positive electrode active slurry was coated on the first side of the positive electrode current collector on one side, and dried in an oven at 100° C. for 6 hours after coating. Then, the positive electrode active slurry was coated on one side on the second side of the positive electrode current collector, and dried in an oven at 100° C. for 6 hours after coating.
  • the loading capacity of the positive electrode active material is 0.304g/1540.25mm 2 .
  • the electrode assembly (dimensions: 28cm ⁇ 148cm ⁇ 118cm).
  • the first edge region with low thermal conductivity is the edge region with low thermal conductivity close to the tab
  • the second edge region with low thermal conductivity is the edge region with low thermal conductivity far away from the tab.
  • the loading amount of the negative electrode active material is 96.76 g, and the loading amount of the positive electrode active material is 173.8 g.
  • Example 2 The difference between Example 2 and Example 1 lies in the formulation of the undercoating slurry in the edge region with low thermal conductivity.
  • step 1.2 of embodiment 4
  • Copper foil was provided as the negative electrode collector, and the dimensions of the copper foil were as follows: thickness 6 ⁇ m, length 2545 mm, and width 183 mm.
  • the first side surface of the negative electrode current collector is divided into a main body area and a first low thermal conductivity edge area, both the main body area and the first low thermal conductivity edge area extend along the length direction of the negative electrode current collector,
  • the first low thermal conductivity edge regions are respectively located on one side of the first long side (the long side on which tabs are subsequently installed) of the main body region.
  • the size of the main body area is 2545mm ⁇ 173mm.
  • the size of the first low thermal conductivity edge region is 2545mm ⁇ 10mm.
  • the undercoating slurry in the main body area and the undercoating slurry in the low thermal conductivity edge area were coated on the main body area and the low thermal conductivity edge area respectively, with a coating thickness of 129 ⁇ m. Dry in an oven at 100°C for 6 hours after coating.
  • Coating the undercoating layer on the second side apply the undercoating layer on the second side surface of the negative electrode current collector by adopting the same partitioning and coating treatment as the first side surface.
  • step 1.2 of embodiment 5
  • Copper foil was provided as the negative electrode collector, and the dimensions of the copper foil were as follows: thickness 6 ⁇ m, length 2545 mm, and width 183 mm.
  • the first side surface of the negative electrode current collector is divided into a main body area and a second low thermal conductivity edge area, both the main body area and the second low thermal conductivity edge area extend along the length direction of the negative electrode current collector,
  • the first low thermal conductivity edge regions are respectively located on one side of the second long side (the long side away from the tab) of the main body region.
  • the size of the main body area is 2545mm ⁇ 173mm.
  • the size of the second low thermal conductivity edge region is 2545mm ⁇ 10mm.
  • the undercoating slurry in the main body area and the undercoating slurry in the low thermal conductivity edge area were coated on the main body area and the low thermal conductivity edge area respectively, with a coating thickness of 129 ⁇ m. Dry in an oven at 100°C for 6 hours after coating.
  • Coating the undercoating layer on the second side apply the undercoating layer on the second side surface of the negative electrode current collector by adopting the same partitioning and coating treatment as the first side surface.
  • Copper foil was provided as the negative electrode current collector, and the dimensions of the copper foil were as follows: thickness 6 ⁇ m, length 2545 mm, and width 183 mm. Using a gravure coating process, the undercoating slurry in the main body area was coated on both sides of the negative electrode current collector, with a coating thickness of 129 ⁇ m. Dry in an oven at 100°C for 6 hours after coating. A current collector with an undercoat layer is obtained after coating.
  • the sampling method is as follows:
  • Cut the pole pieces with a punching knife, and the cutting positions are respectively located in the low thermal conductivity edge area (10mm from the edge of the negative pole piece) and the main body area (the area near the center of the pole piece); the size of the cut sample (rectangle: 5mm (horizontal)* 7mm (longitudinal))
  • the measuring device adopts the transient plane heat source method.
  • When measuring first select two samples with the same thickness. After measuring the thickness of the sample accurately, place the two thin plate samples on both sides of the probe respectively, and then use two pieces of heat insulating material of the same material to press Tight, so that there is no gap between the probe and the sample, to ensure that all the heat generated by the probe is absorbed by the sample.
  • Example 1 the thermal conductivity of the main body region, the first low thermal conductivity edge region and the second low thermal conductivity edge region were detected respectively, and named as ⁇ 1 , ⁇ 2a , ⁇ 2b .
  • Example 4 the thermal conductivity of the main body region and the first low thermal conductivity edge region were detected respectively, and named as ⁇ 1 , ⁇ 2a .
  • Example 5 the thermal conductivity of the main body region and the second low thermal conductivity edge region were detected respectively, and named as ⁇ 1 , ⁇ 2b .
  • Cut the pole piece with a punching knife and the cutting positions are respectively located in the low thermal conductivity edge area (10mm from the edge of the negative pole piece) and the main body area (the area near the center of the pole piece). Take a sample of 5 mm (horizontal) * 7 mm (longitudinal) along the long side direction (MD direction) with a punching knife.
  • the testing instrument is a two-probe sheet resistance tester, and the testing results are shown in Table 1.
  • Example 1 the thermal conductivity coefficients of the main body region, the first low thermal conductivity edge region and the second low thermal conductivity edge region were detected respectively, and named as ⁇ 1 , ⁇ 2a , and ⁇ 2b .
  • Example 4 the thermal conductivity of the main body region and the first low thermal conductivity edge region were detected respectively, and named as ⁇ 1 , ⁇ 2a .
  • Example 5 the thermal conductivity of the main body region and the second low thermal conductivity edge region were detected respectively, and named as ⁇ 1 and ⁇ 2b .
  • the secondary battery is subjected to a cyclic charging and discharging procedure, the charging and discharging current is 0.33C, and the number of cycles is 1000. After the cyclic charge and discharge procedure, the secondary battery was disassembled to evaluate the degree of lithium deposition of the negative electrode sheet.
  • the evaluation method of lithium analysis degree is as follows:
  • Lithium-free a single electrode assembly has no lithium-analysis area
  • First-level lithium analysis the maximum area of a single lithium analysis area is ⁇ 5*5mm 2 , and the number of lithium analysis areas for a single electrode assembly is ⁇ 1;
  • Third-level lithium analysis does not meet the first two levels of judgment conditions.
  • the application After analyzing the electrical conductivity, thermal conductivity and lithium deposition degree of the main region and the edge region, the application summarizes the following empirical coefficient-kinetic coefficient Q, and the relationship between the kinetic coefficient Q and lithium deposition in secondary batteries.
  • the tensile samples were cut from the negative electrode sheets of Examples 1-5 and Comparative Example 1, the gauge length of the tensile samples was 50 mm, and the width was 20 mm.
  • the gauge length is 50 ⁇ 0.5mm
  • the tensile speed is 2mm/min.
  • test standards in this field such as GB/T228-2002 tensile test method for metal materials at room temperature.
  • Examples 4-5 of Table 1 when the negative electrode sheet of the secondary battery has a first low thermal conductivity edge region or a second low thermal conductivity edge region, and the first low thermal conductivity edge region and the second low thermal conductivity edge region The thermal conductivity coefficients are lower than those of the main body area, and the secondary batteries of Examples 4-5 performed well, and only the first-stage lithium precipitation occurred.
  • Comparative Example 1 of Table 1 As shown in Comparative Example 1 of Table 1, when the negative electrode sheet of the secondary battery is not provided with the first low thermal conductivity edge region and the second low thermal conductivity edge region, the secondary battery of Comparative Example 1 performed poorly, and there was secondary precipitation lithium.
  • the present application found that when a secondary battery (such as a lithium-ion battery) is charged, Li + is deintercalated from the positive electrode, and these Li + diffuse in the electrolyte to the surface of the negative electrode and are embedded in the negative electrode material.
  • a secondary battery such as a lithium-ion battery
  • Li + diffuse in the electrolyte to the surface of the negative electrode and are embedded in the negative electrode material.
  • some Li + cannot be smoothly inserted into the negative electrode material, so lithium deposition side reaction occurs on the surface of the negative electrode sheet, that is, lithium precipitation.
  • the present application creatively found that gaps tend to exist at the edge of the negative electrode due to the winding process, which leads to preferential deposition of lithium at the edge of the negative electrode.
  • the present application creatively sets the edge region with low thermal conductivity on the edge of the negative electrode sheet, so during the operation of the secondary battery, the temperature of the low thermal conductivity edge region is higher, which improves the diffusion and intercalation process of Li + , and then The lithium separation situation of the negative electrode, especially the lithium separation situation in the edge region is improved.
  • the present application also pays attention to the electrical conductivity of the main body region and the edge region at the same time, under the condition of fully considering the influence of the dual factors of electrical conductivity and thermal conductivity on the lithium intercalation kinetics of the negative electrode edge region , the present application creatively summarizes and proposes an innovative kinetic coefficient Q, and the relationship between the kinetic coefficient Q and lithium separation in secondary batteries.
  • Examples 1-3 of Table 1 when the negative electrode sheet of the secondary battery has a first low thermal conductivity edge region and a second low thermal conductivity edge region, and the first low thermal conductivity edge region and the second low thermal conductivity edge region The thermal conductivity coefficients of the batteries are lower than those of the main body area, and the secondary batteries of Examples 1-3 have excellent mechanical properties, and the elongation rate is 0.6.
  • Examples 4-5 of Table 1 when the negative electrode sheet of the secondary battery has a first low thermal conductivity edge region or a second low thermal conductivity edge region, and the first low thermal conductivity edge region and the second low thermal conductivity edge region The thermal conductivity coefficients are lower than the main region, and the mechanical properties of the negative pole pieces of Examples 4-5 are good, and the elongation rate is 0.7-0.9.
  • Comparative Example 1 of Table 1 when the negative electrode sheet of the secondary battery is not provided with the first low thermal conductivity edge region and the second low thermal conductivity edge region, the mechanical properties of the secondary battery of Comparative Example 1 are not as good as those of Example 1. ⁇ 5, the elongation is 0.5.
  • 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. .

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Composite Materials (AREA)
  • Battery Electrode And Active Subsutance (AREA)
  • Secondary Cells (AREA)

Abstract

本申请提供一种负极极片、二次电池、电池模块、电池包和用电装置。负极极片包括主体区和至少一个低导热边缘区；所述低导热边缘区和所述主体区的导热系数分别为λ2和λ1，并且λ2＜λ1。

Description

负极极片、二次电池、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，尤其涉及一种负极极片、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、循环性能或安全性能等也提出了更高的要求。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种负极极片，所述负极极片包括主体区和至少一个低导热边缘区；所述低导热边缘区和所述主体区的导热系数分别为λ 2和λ 1，并且λ 2＜λ 1。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到有效改善。
在一些实施方式中，λ 1与λ 2的比值λ 1/λ 2为1.1-1.5∶1。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
在一些实施方式中，λ 1的值为300-400W/(m·K)。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
在一些实施方式中，λ 2的值为200-300W/(m·K)。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
在一些实施方式中，所述低导热边缘区和所述主体区的导电系数分别为σ 2和σ 1；所述负极极片满足动力学系数Q＞0，所述动力学系数Q由下式计算：
Figure PCTCN2021134346-appb-000001
可选地，所述负极极片满足动力学系数Q≥0.1。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
在一些实施方式中，σ 1与σ 2的比值σ 1/σ 2为1.3以下，可选地为1-1.3∶1。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
在一些实施方式中，σ 1的值为5.3×10 7-5.9×10 7μS·cm -1。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
在一些实施方式中，σ 2的值为5.0×10 7-5.3×10 7μS·cm -1。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
在一些实施方式中，所述负极极片包括集流体层，属于所述低导热边缘区的所述集流 体层和属于所述主体区的所述集流体层的导热系数分别为λ 21和λ 11，并且λ 21＜λ 11。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
在一些实施方式中，所述负极极片包括活性材料层，属于所述低导热边缘区的所述负极活性材料层和属于所述主体区的所述负极活性材料层的导热系数分别为λ 23和λ 13，并且λ 23＜λ 13。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
在一些实施方式中，所述负极极片包括集流体层和活性材料层，其中属于所述低导热边缘区的所述集流体层和属于所述低导热边缘区的所述活性材料层之间还设置有属于所述低导热边缘区的底涂层；属于所述主体区的所述活性材料层直接层叠在属于所述主体区的所述集流体层上(即二者之间无底涂层)。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
在一些实施方式中，所述负极极片包括集流体层和活性材料层，其中属于所述低导热边缘区的所述集流体层和属于所述低导热边缘区的所述活性材料层之间还设置有属于所述低导热边缘区的底涂层；属于所述主体区的所述集流体层和属于所述低导热边缘区的所述活性材料层之间还设置有属于所述主体区的底涂层；属于所述低导热边缘区的所述底涂层和属于所述主体区的所述底涂层的导热系数分别为λ 22和λ 12，并且λ 22＜λ 12。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
在一些实施方式中，属于所述低导热边缘区的所述底涂层含有热阻材料，属于所述主体区的所述底涂层含有导电炭黑，所述热阻材料的导热系数低于所述导电炭黑。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
在一些实施方式中，属于所述主体区的所述底涂层不含有所述热阻材料。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
在一些实施方式中，属于所述主体区的所述底涂层含有所述热阻材料，但属于所述主体区的所述底涂层中所述热阻材料的含量低于属于所述低导热边缘区的所述底涂层。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
在一些实施方式中，属于所述低导热边缘区的所述底涂层含有以下成分：导电炭黑50-60重量％；热阻材料5-15重量％；以及粘结剂30-40重量％。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
在一些实施方式中，属于所述主体区的所述底涂层含有以下成分：导电炭黑60-70重量％；以及粘结剂30-40重量％。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
在一些实施方式中，所述热阻材料为选自以下中的一种或多种：明胶、硫酸铵、氯化铵、硫脲和氯化铜。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是 边缘区域的析锂情况得到进一步改善。
在一些实施方式中，所述负极极片包括第一低导热边缘区和/或第二低导热边缘区，所述主体区包括相互平行的第一长边和第二长边；所述第一低导热边缘区位于所述主体区的第一长边的外侧；所述第二低导热边缘区位于所述主体区的第二长边的外侧。在该实施方案中，主体区具有大于1的长宽比，例如大于2的长宽比。
在一些实施方式中，所述低导热边缘区的外侧紧邻所述负极极片的边缘。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
在一些实施方式中，所述低导热边缘区的内侧到所述负极极片边缘的距离为w，所述负极极片的宽度为W，W与w的比值W/w＝11.5-21.9∶1。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
在一些实施方式中，w＝8mm-15mm。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
在一些实施方式中，W＝100mm-200mm。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
在一些实施方式中，所述主体区的一个或多个边的外侧设置有低导热边缘区。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
在一些实施方式中，所述主体区的面积占所述负极极片单侧面积的78.1-88.5％。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
在一些实施方式中，所述低导热边缘区的面积占所述负极极片单侧面积的11.5-21.9％。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
在一些实施方式中，所述主体区和低导热边缘区的面积之比为3.6-7.7∶1。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
本申请的一个实施方式提供一种二次电池，包括电极组件，所述电极组件包括上述任一项所述的负极极片。
本申请的一个实施方式提供一种电池模块，包括上述任一项所述的二次电池。
本申请的一个实施方式提供一种电池包，包括上述任一项所述的电池模块。
本申请的一个实施方式提供一种用电装置，包括选自上述任一项的二次电池、上述任一项所述的电池模块或上述任一项所述的电池包中的至少一种。
有益效果
本申请一个或多个实施方案具有以下一项或多项有益效果：
(1)负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到改善；
(2)负极极片的力学性能，特别是延伸率，得到改善。
附图说明
图1的(a)示出本申请一实施方式的负极极片，图1的(b)示出本申请一实施方式的电极组件。
图2的(a)示出本申请又一实施方式的负极极片，图2的(b)示出本申请又一实施方式的电极组件。
图3的(a)示出本申请又一实施方式的负极极片，图3的(b)示出本申请又一实施方式的电极组件。
图4示出本申请又一实施方式的负极极片。
图5的(a)-(d)示出本申请一些实施方式的负极极片的截面的示意图。
图6的(a)示出本申请一些实施方式的二次电池的透视图，图(6)的(b)示出的本申请一谢实施方式的二次电池的爆炸图。
图7是本申请一实施方式的电池模块的示意图。
图8是本申请一实施方式的电池包的示意图。
图9是图8所示的本申请一实施方式的电池包的爆炸图。
图10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：
负极极片10；主体区11；低导热边缘区12；第一低导热边缘区121；第二低导热边缘区122；第三低导热边缘区123；第四低导热边缘区124；第一长边111；第二长边112；活性材料层22；底涂层24；集流体层26；
电池包1；上箱体2；下箱体3；电池模块4；二次电池5；壳体51；电极组件52；极耳522；顶盖组件53
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负极活性材料及其制造方法、正极极片、负极极片、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，所述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)。
[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。
通常情况下，二次电池包括正极极片、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。
[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活性材料层，正极活性材料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，正极活性材料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，正极活性材料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，正极活性材料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。
[负极极片]
图1的(a)示出本申请一实施方式的负极极片。
参考图1的(a)，在一些实施方式中，本申请提供一种负极极片10，负极极片10包括主体区11和第一低导热边缘区121，第一低导热边缘区121和主体区11的导热系数分别为λ 2a和λ 1，并且λ 2a＜λ 1。基于该方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到有效改善。
参考图1的(a)，在一些实施方式中，第一低导热边缘区121位于主体区11的一侧。
图1的(b)示出本申请一实施方式的电极组件。
参考图1的(b)，在一些实施方式中，电极组件52包括负极极片10、隔离膜和正极极片经层叠卷绕后获得的卷芯。电极组件52还包括安装在负极极片一侧的极耳522。在本实施方式中，第一低导热边缘区121位于主体区11靠近极耳522的一侧。基于该方案的电极组件用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到有效改善。
图2的(a)示出本申请一实施方式的负极极片。
参考图2的(a)，在一些实施方式中，本申请提供一种负极极片10，负极极片10包括主体区11和第二低导热边缘区122，第二低导热边缘区122和主体区11的导热系数分别为λ 2b和λ 1，并且λ 2b＜λ 1。基于该方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到有效改善。
参考图2的(a)，在一些实施方式中，第二低导热边缘区122位于主体区11的一侧。
图2的(b)示出本申请一实施方式的电极组件。
参考图2的(b)，在一些实施方式中，电极组件52包括极耳522。电极组件52包括负极极片10、隔离膜和正极极片经层叠卷绕后获得的卷芯。电极组件52还包括安装在负极极片一侧的极耳522。在本实施方式中，第二低导热边缘区122位于主体区11远离极耳522的一侧。
图3的(a)示出本申请一实施方式的负极极片。
参考图3的(a)，在一些实施方式中，负极极片10包括主体区11和低导热边缘区12， 低导热边缘区12和主体区11的导热系数分别为λ 2和λ 1，并且λ 2＜λ 1。
参考图3的(a)，在一些实施方式中，低导热边缘区12包括第一低导热边缘区121和第二低导热边缘区122。第一低导热边缘区121和第二低导热边缘区122分别位于主体区11的两侧。第一低导热边缘区121、第二低导热边缘区122和主体区11的导热系数分别为λ 2a、λ 2b和λ 1，并且λ 2a＜λ 1、λ 2b＜λ 1。
图3的(b)示出本申请一实施方式的电极组件。
参考图3的(b)，在一些实施方式中，电极组件52包括负极极片10、隔离膜和正极极片经层叠卷绕后获得的卷芯。电极组件52还包括安装在负极极片一侧的极耳522。在本实施方式中，第一低导热边缘区121位于主体区11靠近极耳522的一侧，第二低导热边缘区122位于主体区11远离极耳522的一侧。
本申请通过在负极极片10上设置主体区11和至少一个低导热边缘区12，并控制所述低导热边缘区12和所述主体区11的导热系数分别为λ 2和λ 1，并且λ 2＜λ 1，该负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到显著的改善。其原因在于，低导热边缘区与主体区的导热系数不同(前者小于后者)，电池在工作时低导热边缘区的温度高于主体区，使得低导热边缘区的动力学性能高于主体区，从而提高负极的析锂窗口，抑制极片的边缘析锂，提高电池循环稳定性和安全性。
不受理论限制，本申请的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到有效改善，原因可能如下：
本申请发现，二次电池(如锂离子电池)充电时，Li +从正极脱嵌，这些Li +在电解质中扩散至负极表面，并嵌入负极材料中。但是，由于欧姆电阻、电荷转移和扩散过程的阻碍，一些Li +不能顺利嵌入负极材料，故而在负极极片表面发生锂沉积副反应，即析锂。本申请还发现，负极极片靠近边缘的位置易于因卷绕工序而存在间隙，这导致锂优先在负极边缘沉积。
基于本申请的上述发现，本申请创造性地在负极极片的边缘设置了低导热边缘区，由于低导热边缘区的导热系数较低，故而在二次电池工作过程中，低导热边缘区的温度更高，这增大了低导热边缘区Li +的扩散和嵌入的速率，进而改善了负极边缘区的析锂情况，进而改善了二次电池的工作性能。
在一些实施方式中，术语“低导热边缘区”一词中，“低导热”是指边缘区比主体区更低的导热系数，即二者存在导热系数的比值小于1。“低导热”并非指示或暗示边缘区的导热系数必须要达到何种具体值。
参考图1-3，在一些实施方式中，主体区11是负极极片10中心附近的区域，低导热 边缘区是指位于主体区11外侧且导热系数低于主体区11的区域。
在一些实施方式中，除非特别说明，“边缘区”与“低导热边缘区”可互换使用。
在一些实施方式中，导热系数根据“ISO 22007-2：2008瞬态平面热源法测定材料的导热系数”测试获得。导热系数的单位可以是W/(m·K)。导热系数的测量方向可选为垂直于负极极片的面方向(即法向)。
在一些实施方式中，导热系数λ 1与λ 2的比值λ 1/λ 2为1.1-1.5∶1，可选地为1.2-1.4∶1，例如1-1.1∶1、1.1-1.2∶1、1.2-1.3∶1、1.3-1.4∶1、1.4-1.5∶1。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
在一些实施方式中，导热系数λ 1的值为300-400W/(m·K)，例如300-320W/(m·K)、320-340W/(m·K)、340-360W/(m·K)、360-380W/(m·K)或380-400W/(m·K)。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
在一些实施方式中，导热系数λ 2的值为200-300W/(m·K)，例如200-220W/(m·K)、220-240W/(m·K)、240-260W/(m·K)、260-280W/(m·K)或280-300W/(m·K)。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
应当理解，λ 2和λ 1的取值范围是可能存在重叠的情况，只要满足λ 2＜λ 1即可。
在一些实施方式中，所述低导热边缘区12和所述主体区11的导电系数分别为σ 2和σ 1；所述负极极片10满足动力学系数Q＞0，所述动力学系数Q由下式计算：
Figure PCTCN2021134346-appb-000002
可选地，所述负极极片10满足动力学系数Q≥0.1。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
在一些实施方式种，导电系数参考标准“GB/T 11007-2008电导率仪试验方法”测试获得。电导率的单位可以是μS·cm -1。电导率的测量方向可选为平行于负极极片。
在一些实施方式中，导电系数σ 1与σ 2的比值σ 1/σ 2为1.3以下，可选地，σ 1/σ 2为1-1.3∶1，可选地σ 1/σ 2为1.1-1.2∶1。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
在一些实施方式中，导电系数σ 1的值为5.3×10 7-5.9×10 7μS·cm -1，例如5.3-5.5μS·cm - 1、5.5-5.7μS·cm -1、5.7-5.9μS·cm -1。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
在一些实施方式中，导电系数σ 2的值为5.0×10 7-5.3×10 7μS·cm -1，例如5.1-5.2μS·cm - 1。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
参考图3的(a)，在一些实施方式中，负极极片10具有长度方向L和宽度方向D，负极极片10在长度方向L的尺寸大于其在宽度方向D的尺寸。主体区11和低导热边缘区12均沿负极极片10的长度方向L延伸。低导热边缘区12的内侧到负极极片10的边缘的距离为w，负极极片的宽度为W，W与w的比值W/w＝11.5-21.9∶1。
参考图3，在一些实施方式中，所述主体区11包括相互平行的第一长边111和第二长边112，所述负极极片10包括第一低导热边缘区121和/或第二低导热边缘区122，所述第一低导热边缘区121位于所述主体区11的第一长边的外侧；所述第二低导热边缘区122位于所述主体区11的第二长边的外侧。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
参考图3，在一些实施方式中，所述低导热边缘区12的外侧紧邻所述负极极片10的边缘。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
在一些实施方式中，术语“紧邻”包括低导热边缘区的外侧与所述负极极片10的边缘完全重合，或者二者之间仅有5mm以下(例如3mm以下)的间距。
参考图3，在一些实施方式中，所述低导热边缘区12的内侧到所述负极极片10边缘的距离为w(两个低导热边缘区的内侧到所述负极极片10边缘的距离各自为w1和w2)，所述负极极片10的宽度为W，W与w的比值W/w＝11.5-21.9∶1，例如W/w＝11.5-13.5∶1、13.5-15.5∶1、15.5-17.5∶1、17.5-19.5∶1或19.5-21.5∶1。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
参考图3，在一些实施方式中，w＝8mm-15mm，例如w＝10mm-12mm。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
参考图3，在一些实施方式中，W＝100mm-200mm，例如W＝100mm-120mm、120mm-140mm、140mm-160mm、160mm-180mm或180mm-200mm。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
参考图3，在一些实施方式中，所述主体区11的面积占所述负极极片10单侧面积的78.1-88.5％，例如78.1-80.1％、80.1-82.1％、82.1-84.1％、84.1-86.1％、86.1-88.1％。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
参考图3，在一些实施方式中，所述低导热边缘区12的面积占所述负极极片10单侧面积的11.5-21.9％，例如11.5-13.5％、13.5-15.5％、15.5-17.5％、17.5-19.5％或19.5-21.5％。 基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
参考图3，在一些实施方式中，所述主体区11和低导热边缘区12的面积之比为3.6-7.7∶1，例如3.6-4.6∶1、4.6-5.6∶1、5.6-6.6∶1或6.6-7.6∶1。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
图4示出本申请一些实施方式的负极极片。
参考图4，在一些实施方式中，所述主体区11的一个或多个边的外侧设置有低导热边缘区12。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
参考图4，在一些实施方式中，负极极片10包括主体区11和多个低导热边缘区12。主体区11具有四边形的形状。主体区11的四个边的外侧分别设置有边缘区12，它们依次为第一低导热边缘区121，第二低导热边缘区122，第三低导热边缘区123和第四低导热边缘区124。
图5的(a)-(d)示出本申请一些实施方式的负极极片。
参考图5的(a)，本申请的一个实施方式提供一种负极极片10，所述负极极片10包括主体区11和至少一个低导热边缘区12；所述低导热边缘区12和所述主体区11的导热系数分别为λ 2和λ 1，并且λ 2＜λ 1。
图5的(a)-(d)示出一些实施方式的负极极片10的截面图。
参考图5的(a)，在一些实施方式中，负极极片10包括集流体层26，属于低导热边缘区12的集流体层26和属于主体区11的集流体层26的导热系数分别为λ 21和λ 11，并且λ 21＜λ 11。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。负极极片10还可以包括与集流体层26层叠的活性材料层。
参考图5的(b)，在一些实施方式中，负极极片10包括活性材料层22，属于低导热边缘区12的负极活性材料层22和属于主体区11的负极活性材料层22的导热系数分别为λ 23和λ 13，并且λ 23＜λ 13。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。负极极片10还可以包括与活性材料层层叠的集流体层。
参考图5的(c)，在一些实施方式中，负极极片10包括集流体层26和活性材料层22，其中属于低导热边缘区12的集流体层26和属于低导热边缘区12的活性材料层22之间还设置有属于低导热边缘区12的底涂层24；属于主体区11的活性材料层22直接层叠在属于主体区11的集流体层26上(即二者之间无底涂层24)。基于此方案的负极极片用于二 次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
参考图5的(d)，在一些实施方式中，负极极片10包括集流体层26和活性材料层22，其中属于低导热边缘区12的集流体层26和属于低导热边缘区12的活性材料层22之间还设置有属于低导热边缘区12的底涂层24；属于主体区11的集流体层26和属于低导热边缘区12的活性材料层22之间还设置有属于主体区11的底涂层24；属于低导热边缘区12的底涂层24和属于主体区11的底涂层24的导热系数分别为λ 22和λ 12，并且λ 22＜λ 12。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
参考图5，在一些实施方式中，属于所述低导热边缘区12的所述底涂层24含有热阻材料，属于所述主体区11的所述底涂层24含有导电炭黑，所述热阻材料的导热系数低于所述导电炭黑。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
参考图5，在一些实施方式中，属于所述主体区11的所述底涂层24不含有所述热阻材料。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
参考图5，在一些实施方式中，属于所述主体区11的所述底涂层24含有所述热阻材料，但属于所述主体区11的所述底涂层24中所述热阻材料的含量低于属于所述低导热边缘区12的所述底涂层24。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
参考图5，在一些实施方式中，属于所述低导热边缘区12的所述底涂层24含有以下成分：导电炭黑50-60重量％(例如53-55重量％)；热阻材料5-15重量％(例如8-12重量％，例如10重量％)；以及粘结剂30-40重量％(例如31-34重量％)。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
参考图5，在一些实施方式中，属于所述低导热边缘区12的所述底涂层24中粘结剂为丁苯橡胶。
参考图5，在一些实施方式中，属于所述低导热边缘区12的所述底涂层24还含有分散剂0.01-0.1重量％。可选地，分散剂为羧甲基纤维素。
参考图5，在一些实施方式中，属于所述主体区11的所述底涂层24含有以下成分：导电炭黑60-70重量％；以及粘结剂30-40重量％。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
参考图5，在一些实施方式中，属于所述主体区11的所述底涂层24中粘结剂为丁苯 橡胶。
参考图5，在一些实施方式中，属于所述主体区11的所述底涂层24还含有分散剂0.01-0.1重量％。可选地，分散剂为羧甲基纤维素。
在一些实施方式中，所述热阻材料为选自以下中的一种或多种：明胶、硫酸铵、氯化铵、硫脲和氯化铜。基于此方案的负极极片用于二次电池，二次电池的析锂情况、尤其是边缘区域的析锂情况得到进一步改善。
参考图5的(b)，在一些实施方式中，负极极片是无集流体的负极。
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活性材料层，所述负极活性材料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，负极活性材料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，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、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，负极活性材料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，负极活性材料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，负极活性材料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，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，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。
参考图6，本申请的一个实施方式提供一种二次电池，包括电极组件，所述电极组件包括上述任一项所述的负极极片。
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6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6，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，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。
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。
参考图7，本申请的一个实施方式提供一种电池模块，包括上述任一项所述的二次电池。
图7是作为一个示例的电池模块4。参照图7，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。
参考图8和图9，本申请的一个实施方式提供一种电池包，包括上述任一项所述的电池模块。
参照图8和图9，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。
参考图10，本申请的一个实施方式提供一种用电装置，包括选自上述任一项的二次电池、上述任一项所述的电池模块或上述任一项所述的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。
图10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。
下面结合具体实验对本申请的方案进行具体阐述。
一、极片的制备
以下实验中采用的原料如下表所示
名称 厂家/牌号/CAS
导电炭黑(SP) 天津天一世纪化工产品科技发展有限公司
丁苯橡胶(SBR) 天津市陆港石油橡胶有限公司
羧甲基纤维素(CMC) 文安县长虹纤维素厂
聚偏二氟乙烯(PVDF) 广东东莞代理孚诺林化工
硫脲CH 4N 2S 山东益丰生化环保股份有限公司
明胶(Gelatin) 衡水言若粘合剂有限公司/9000-70-8
氯化铜(CuCl 2) 苏州金瑞环保资源综合利用有限公司
碳酸乙烯酯(EC) 上海凯茵化工有限公司
碳酸二乙酯(DEC) 上海凯茵化工有限公司
碳酸二甲酯(DMC) 上海凯茵化工有限公司
实施例1
1.负极极片的制备
1.1负极底涂层浆料的制备
主体区底涂层浆料的制备方法如下：将SP∶SBR∶CMC按重量比SP∶SBR∶CMC＝0.645∶0.323∶0.032混合，溶于水，在真空搅拌机中搅拌均匀，获得浆料。
低导热边缘区底涂层浆料的制备方法如下：将SP∶SBR∶CMC∶硫脲，按重量比SP∶SBR∶CMC∶硫脲＝0.545∶0.323∶0.032∶0.1混合，溶于水，在真空搅拌机中搅拌均匀，获得浆料。
1.2负极底涂层的分区涂布(双侧低导热边缘区)
提供铜箔作为负极集流体，铜箔的尺寸如下：厚度6μm，长度2545mm，宽度183mm。
第一侧底涂层涂布：在负极集流体的第一侧表面划分为一个主体区和两个低导热边缘区，主体区和两个低导热边缘区均沿负极集流体的长度方向延伸，两个低导热边缘区分别位于该主体区的长边的两侧。主体区的尺寸为2545mm×163mm。两个低导热边缘区的尺寸分别为2545mm×10mm。采用凹版涂布工艺，将主体区底涂层浆料和低导热边缘区底涂层浆料分别涂布至上述主体区和低导热边缘区，涂布厚度为129μm。涂布后在100℃的烘箱中烘干6h。
第二侧底涂层涂布：采用与第一侧表面相同的分区和涂布处理，对负极集流体的第二侧表面底涂层涂布。
经第一侧底涂层涂布和第二侧底涂层涂布后，获得具有底涂层的集流体。
1.3负极活性浆料的制备
负极活性浆料的制备方法如下：将石墨/硬碳、SBR(作为粘结剂)和CMC(作为分散剂)按97％∶1％∶2％重量百分比进行配比，并用适量蒸馏水稀释，然后在真空搅拌机中搅拌混合，形成均匀的负极活性浆料。
1.4负极活性材料的涂布
第一侧涂布：将步骤(2)制备的负极活性浆料涂敷在具有底涂层的集流体的第一侧表面。涂布后在100℃的烘箱中烘干6h。
第二侧涂布，采用与第一侧相同的负极活性浆料涂布工艺，对具有底涂层的集流体的第二侧表面。涂布后在100℃的烘箱中烘干6h。
获得实施例1的负极极片。按单面计，负极活性材料的负载量为0.160g/1540.25mm 2。
2.正极极片的制备
2.1正极活性浆料的制备
将正极活性材料LiNi 0.33C0 0.33Mn 0.33O 2、SP和PVDF按97％∶1.5％∶1.5％重量百分比例 混合，用适量的N-甲基吡咯烷酮稀释，然后在真空搅拌机中搅拌形成均匀的正极活性浆料。
2.2正极活性材料的涂布
提供铝箔作为正极集流体。正极集流体的尺寸如下：厚度13μm，长度2460mm，宽度179mm。
将正极活性浆料在正极集流体的第一侧进行单面涂布，涂布后在100℃的烘箱中烘干6h。然后将正极活性浆料在正极集流体的第二侧进行单面涂布，涂布后在100℃的烘箱中烘干6h。
实施例1所述的正极极片。按单面计，正极活性材料的负载量为0.304g/1540.25mm 2。
3.二次电池的制备
3.1在正极极片、负极极片的一个长边分别安装极耳，然后与隔离膜按顺序层叠，卷绕，形成卷芯，即电极组件(尺寸为28cm×148cm×118cm)。第一低导热边缘区为靠近极耳的低导热边缘区，第二低导热边缘区为远离极耳的低导热边缘区。将电极组件置于外包装中，注入150g电解液，电解液为含1MLiPF6的溶液，溶液的溶剂为EC、DEC和DMC按体积比1∶1∶1混合的产物。封装外包装后，即获得二次电池。
一个二次电池中，负极活性材料的负载量为96.76g，正极活性材料的负载量为173.8g。
实施例2
实施例2与实施例1的区别仅在于低导热边缘区底涂层浆料的配方。实施例3的步骤1.1中，低导热边缘区底涂层浆料的配方如下：按重量比，SP∶SBR∶CMC∶明胶＝0.545∶0.323∶0.032∶0.1。其他步骤参数参照实施例1。
实施例3
实施例3与实施例1的区别在于低导热边缘区底涂层浆料的配方。实施例3的步骤1.1中，低导热边缘区底涂层浆料的配方如下，按重量比，SP∶SBR∶CMC∶氯化铜＝0.545∶0.323∶0.032∶0.1。其他步骤参数参照实施例1。
实施例4
实施例4与实施例1的区别在于以下(1)-(2)：
(1)低导热边缘区底涂层浆料的配方
实施例4的步骤1.1中，低导热边缘区底涂层浆料的配方如下：按重量比，SP∶SBR∶CMC∶氯化铜＝0.545∶0.323∶0.032∶0.1。
(2)负极底涂层的分区涂布(单侧低导热边缘区)
实施例4的步骤1.2中：
提供铜箔作为负极集流体，铜箔的尺寸如下：厚度6μm，长度2545mm，宽度183mm。
第一侧底涂层涂布：在负极集流体的第一侧表面划分为一个主体区和第一低导热边缘区，主体区和第一低导热边缘区均沿负极集流体的长度方向延伸，第一低导热边缘区分别位于主体区第一长边(后续安装极耳的长边)的一侧。主体区的尺寸为2545mm×173mm。第一低导热边缘区的尺寸为2545mm×10mm。采用凹版涂布工艺，将主体区底涂层浆料和低导热边缘区底涂层浆料分别涂布至上述主体区和低导热边缘区，涂布厚度为129μm。涂布后在100℃的烘箱中烘干6h。
第二侧底涂层涂布：采用与第一侧表面相同的分区和涂布处理，对负极集流体的第二侧表面底涂层涂布。
经第一侧底涂层涂布和第二侧底涂层涂布后，获得具有底涂层的集流体。
其他步骤参数参照实施例1。
实施例5
实施例5与实施例1的区别在于以下(1)-(2)：
(1)低导热边缘区底涂层浆料的配方
实施例5的步骤1.1中，低导热边缘区底涂层浆料的配方如下：按重量比，SP∶SBR∶CMC∶氯化铜＝0.545∶0.323∶0.032∶0.1。
(2)负极底涂层的分区涂布(单侧低导热边缘区)
实施例5的步骤1.2中：
提供铜箔作为负极集流体，铜箔的尺寸如下：厚度6μm，长度2545mm，宽度183mm。
第一侧底涂层涂布：在负极集流体的第一侧表面划分为一个主体区和第二低导热边缘区，主体区和第二低导热边缘区均沿负极集流体的长度方向延伸，第一低导热边缘区分别位于主体区第二长边(远离极耳的长边)的一侧。主体区的尺寸为2545mm×173mm。第二低导热边缘区的尺寸为2545mm×10mm。采用凹版涂布工艺，将主体区底涂层浆料和低导热边缘区底涂层浆料分别涂布至上述主体区和低导热边缘区，涂布厚度为129μm。涂布后在100℃的烘箱中烘干6h。
第二侧底涂层涂布：采用与第一侧表面相同的分区和涂布处理，对负极集流体的第二侧表面底涂层涂布。
经第一侧底涂层涂布和第二侧底涂层涂布后，获得具有底涂层的集流体。
其他步骤参数参照实施例1。
对比例1
对比例1与实施例1的区别如下：
对比例1的步骤1.2中负极底涂层的无分区涂布。具体如下：
提供铜箔作为负极集流体，铜箔的尺寸如下：厚度6μm，长度2545mm，宽度183mm。采用凹版涂布工艺，将主体区底涂层浆料涂布至负极集流体的两侧表面，涂布厚度为129μm。涂布后在100℃的烘箱中烘干6h。涂布后获得具有底涂层的集流体。
其他步骤参数参照实施例1。
分析检测项目
1、导热系数(λ)的测定
参考标准“ISO 22007-2：2008瞬态平面热源法测定材料的导热系数”，检测负极极片的低导热边缘区和主体区的导热系数：
(1)采样方法如下：
用冲刀裁切极片，裁切位置分别位于低导热边缘区(距离负极极片边缘10mm区域)和主体区(极片中心附近的区域)；裁切样品大小(矩形：5mm(横)*7mm(纵))
(2)检测方法如下：
采用瞬态平面热源法测量装置，测量时先选择两块厚度一致的样品，精确测量样品厚度后，将两块薄板样品分别放置于探头的两边，然后用两块相同材质的绝热隔热材料压紧，使探头与样品之间没有空隙，以保证探头产生的所有热量均为样品所吸收。
对于实施例1-3，分别检测主体区、第一低导热边缘区和第二低导热边缘区的导热系数，命名为λ 1、λ 2a、λ 2b。对于实施例4，分别检测主体区和第一低导热边缘区的导热系数，命名为λ 1、λ 2a。对于实施例5，分别检测主体区和第二低导热边缘区的导热系数，命名为λ 1、λ 2b。
2、负极极片主体区/低导热边缘区的电导率(σ)的测定
参考标准“GB/T 11007-2008电导率仪试验方法”，检测负极极片的低导热边缘区和主体区的电导率：
(1)采样方法如下
用冲刀裁切极片，裁切位置分别位于低导热边缘区(距离负极极片边缘10mm区域) 和主体区(极片中心附近的区域)。用冲刀沿着长边方向(MD方向)，取5mm(横)*7mm(纵)的样品。
(2)检测方法如下
检测仪器为两探针膜片电阻测试仪，检测结果如表1。
对于实施例1-3，分别检测主体区、第一低导热边缘区和第二低导热边缘区的导热系数，命名为σ 1、σ 2a、σ 2b。对于实施例4，分别检测主体区和第一低导热边缘区的导热系数，命名为σ 1、σ 2a。对于实施例5，分别检测主体区和第二低导热边缘区的导热系数，命名为σ 1、σ 2b。
3、析锂程度的测定规则如下
对二次电池进行循环充放电程序，充电和放电的电流为0.33C，循环圈数为1000圈。循环充放电程序结束后，拆解二次电池，评估负极极片的析锂程度。
析锂程度评估方法如下：
无析锂：单个电极组件无析锂区
一级析锂：单个析锂区最大面积≤5*5mm 2，单个电极组件的析锂区个数≤1；
二级析锂：5*5mm 2＜单个析锂区最大面积≤10*10mm 2，单个电极组件的析锂区个数≤1；
三级析锂：不满足前两级判定条件。
4、动力学系数的计算
经过对主体区和边缘区电导率、导热系数和析锂程度进行分析，本申请归纳了以下经验系数-动力学系数Q，以及动力学系数Q与二次电池析锂的关系。
Figure PCTCN2021134346-appb-000003
5、拉伸延伸率：
从实施例1-5和对比例1的负极极片上裁切拉伸样品，拉伸样品的标距50mm，宽度为20mm。
使用拉力机进行拉伸试验，标距50±0.5mm，拉伸速度2mm/min，拉伸完成后按照下式计算拉伸延伸率：
拉伸延伸率＝拉伸位移÷标距(50mm)
未详细描述的测试细节可以参考本领域通用测试标准，例如GB/T228-2002金属材料室温拉伸试验方法。
Figure PCTCN2021134346-appb-000004
(1)关于导热系数
如表1的实施例1-3所示，当二次电池的负极极片上具有第一低导热边缘区和第二低导热边缘区时，且第一低导热边缘区和第二低导热边缘区的导热系数均低于主体区，实施例1～3的二次电池表现优异，无析锂发生。
如表1的实施例4～5所示，当二次电池的负极极片上具有第一低导热边缘区或第二低导热边缘区时，且第一低导热边缘区和第二低导热边缘区的导热系数均低于主体区，实施例4～5的二次电池表现良好，仅有一级析锂发生。
如表1的对比例1所示，当二次电池的负极极片上未设置有第一低导热边缘区和第二低导热边缘区时，对比例1的二次电池表现不良，存在二级析出锂。
(2)关于Q值
如表1的实施例1-5所示，当上述动力学系数Q＞0时，尤其是Q＞0.1时，负极极片没有析锂或仅表现出一级析锂。
如表1的对比例1所示，当动力学系数Q＝0时，负极极片存在二级析锂。
不受理论限制，实施例1-5的二次电池析锂情况改善的原因可能如下：
首先，本申请发现，二次电池(如锂离子电池)充电时，Li +从正极脱嵌，这些Li +在电解质中扩散至负极表面，并嵌入负极材料中。但是，由于欧姆电阻、电荷转移和扩散过程的阻碍，一些Li +不能顺利嵌入负极材料，故而在负极极片表面发生锂沉积副反应，即析锂。
进一步，本申请创造性地发现，负极边缘易于因卷绕工序而存在间隙，这导致锂优先在负极边缘沉积。
进一步，本申请创造性地在负极极片的边缘设置了具有低导热边缘区，故而在二次电池工作过程中，低导热边缘区的温度更高，这改善了Li +的扩散和嵌入过程，进而改善了负极的析锂情况、尤其是边缘区域的析锂情况。
进一步，本申请在设置低导热边缘区的基础上，还同时关注了主体区和边缘区的电导率，在充分考虑了电导率和导热系数双因素对负极边缘区嵌锂动力学影响的情况下，本申请创造性地归纳并提出了创新的动力学系数Q，以及动力学系数Q与二次电池析锂的关系。
Figure PCTCN2021134346-appb-000005
实验数据显示，通过控制动力学系数Q＞0时，尤其是Q＞0.1时，负极极片没有析锂或仅表现出一级析锂。
(3)关于力学性能
如表1的实施例1-3所示，当二次电池的负极极片上具有第一低导热边缘区和第二低导热边缘区时，且第一低导热边缘区和第二低导热边缘区的导热系数均低于主体区，实施例1～3的二次电池力学性能优异，延伸率为0.6。
如表1的实施例4～5所示，当二次电池的负极极片上具有第一低导热边缘区或第二低导热边缘区时，且第一低导热边缘区和第二低导热边缘区的导热系数均低于主体区，实施例4～5的负极极片力学性能良好，延伸率为0.7～0.9。
如表1的对比例1所示，当二次电池的负极极片上未设置有第一低导热边缘区和第二低导热边缘区时，对比例1的二次电池的力学性能不如实施例1～5，延伸率为0.5。
以上技术发现为本申请首次提出，且是本领域技术人员预料不到的。
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 (19)

  1. 一种负极极片，其特征在于，
    所述负极极片包括主体区和至少一个低导热边缘区；
    所述低导热边缘区和所述主体区的导热系数分别为λ 2和λ 1，并且λ 2＜λ 1。
  2. 根据权利要求1所述的负极极片，其特征在于以下任一项：
    (1)λ 1与λ 2的比值λ 1/λ 2为1.1-1.5∶1，可选地为1.2-1.4∶1；
    (2)λ 1的值为300-400W/(m·K)；
    (3)λ 2的值为200-300W/(m·K)。
  3. 根据权利要求1或2所述的负极极片，其中，所述低导热边缘区和所述主体区的导电系数分别为σ 2和σ 1；
    所述负极极片满足动力学系数Q＞0，所述动力学系数Q由下式计算：
    Figure PCTCN2021134346-appb-100001
    可选地，所述负极极片满足动力学系数Q≥0.1。
  4. 根据权利要求1-3中任一项所述的负极极片，其特征在于以下任一项：
    (1)σ 1与σ 2的比值σ 1/σ 2为1.3以下，可选地为1-1.3∶1；
    (2)σ 1的值为5.3×10 7-5.9×10 7μS·cm -1；
    (3)σ 2的值为5.0×10 7-5.3×10 7μS·cm -1。
  5. 根据权利要求1-4中任一项所述的负极极片，其特征在于，所述负极极片包括集流体层；
    属于所述低导热边缘区的所述集流体层和属于所述主体区的所述集流体层的导热系数分别为λ 21和λ 11，并且λ 21＜λ 11。
  6. 根据权利要求1-5中任一项所述的负极极片，其特征在于，所述负极极片包括活性材料层；
    属于所述低导热边缘区的所述负极活性材料层和属于所述主体区的所述负极活性材料层的导热系数分别为λ 23和λ 13，并且λ 23＜λ 13。
  7. 根据权利要求1-4中任一项所述的负极极片，其特征在于，所述负极极片包括集流体层和活性材料层，其中
    属于所述低导热边缘区的所述集流体层和属于所述低导热边缘区的所述活性材料层之间还设置有属于所述低导热边缘区的底涂层；
    属于所述主体区的所述活性材料层直接层叠在属于所述主体区的所述集流体层上。
  8. 根据权利要求1-4中任一项所述的负极极片，其特征在于，所述负极极片包括集流体层和活性材料层，其中
    属于所述低导热边缘区的所述集流体层和属于所述低导热边缘区的所述活性材料层之间还设置有属于所述低导热边缘区的底涂层；
    属于所述主体区的所述集流体层和属于所述低导热边缘区的所述活性材料层之间还设置有属于所述主体区的底涂层；
    属于所述低导热边缘区的所述底涂层和属于所述主体区的所述底涂层的导热系数分别为λ 22和λ 12，并且λ 22＜λ 12。
  9. 根据权利要求8所述的负极极片，其特征在于，属于所述低导热边缘区的所述底涂层含有热阻材料，属于所述主体区的所述底涂层含有导电炭黑，所述热阻材料的导热系数低于所述导电炭黑。
  10. 根据权利要求9所述的负极极片，其特征在于，
    属于所述主体区的所述底涂层不含有所述热阻材料；或者
    属于所述主体区的所述底涂层含有所述热阻材料，但属于所述主体区的所述底涂层中所述热阻材料的含量低于属于所述低导热边缘区的所述底涂层。
  11. 根据权利要求7-10中任一项所述的负极极片，其特征在于，属于所述低导热边缘区的所述底涂层含有以下成分：
    导电炭黑50-60重量％；
    热阻材料5-15重量％；
    粘结剂30-40重量％。
  12. 根据权利要求8-10中任一项所述的负极极片，其特征在于，属于所述主体区的所述底涂层含有以下成分：
    导电炭黑60-70重量％；
    粘结剂30-40重量％。
  13. 根据权利要求9-12中任一项所述的负极极片，其特征在于，所述热阻材料为选自以下中的一种或多种：明胶、硫酸铵、氯化铵、硫脲和氯化铜。
  14. 根据权利要求1-13中任一项所述的负极极片，所述负极极片包括第一低导热边缘区和/或第二低导热边缘区，所述主体区包括相互平行的第一长边和第二长边，
    所述第一低导热边缘区位于所述主体区的第一长边的外侧；
    所述第二低导热边缘区位于所述主体区的第二长边的外侧。
  15. 根据权利要求1-13中任一项所述的负极极片，其具有以下一项或多项特征：
    (1)所述低导热边缘区的外侧紧邻所述负极极片的边缘；
    (2)所述低导热边缘区的内侧到所述负极极片边缘的距离为w，所述负极极片的宽度为W，W与w的比值W/w＝11.5-21.9∶1；
    可选地，w＝8mm-15mm；
    可选地，W＝100mm-200mm；
    (3)所述主体区的一个或多个边的外侧设置有低导热边缘区
    (4)所述主体区的面积占所述负极极片单侧面积的78.1-88.5％；
    (5)所述低导热边缘区的面积占所述负极极片单侧面积的11.5-21.9％；
    (6)所述主体区和低导热边缘区的面积之比为3.6-7.7∶1。
  16. 一种二次电池，包括电极组件，所述电极组件包括权利要求1-15中任一项所述的负极极片。
  17. 一种电池模块，包括权利要求16所述的二次电池。
  18. 一种电池包，包括权利要求17所述的电池模块。
  19. 一种用电装置，包括选自权利要求16所述的二次电池、权利要求17所述的电池模块或权利要求18所述的电池包中的至少一种。
PCT/CN2021/134346 2021-11-30 2021-11-30 负极极片、二次电池、电池模块、电池包和用电装置 WO2023097433A1 (zh)

Priority Applications (4)

Application Number Priority Date Filing Date Title
CN202180092464.8A CN116802824A (zh) 2021-11-30 2021-11-30 负极极片、二次电池、电池模块、电池包和用电装置
PCT/CN2021/134346 WO2023097433A1 (zh) 2021-11-30 2021-11-30 负极极片、二次电池、电池模块、电池包和用电装置
EP21956260.0A EP4213235A1 (en) 2021-11-30 2021-11-30 Negative electrode plate, secondary battery, battery module, battery pack and electric apparatus
US18/119,832 US20230246155A1 (en) 2021-11-30 2023-03-10 Negative electrode plate, secondary battery, battery module, battery pack, and power consuming device

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/CN2021/134346 WO2023097433A1 (zh) 2021-11-30 2021-11-30 负极极片、二次电池、电池模块、电池包和用电装置

Related Child Applications (1)

Application Number Title Priority Date Filing Date
US18/119,832 Continuation US20230246155A1 (en) 2021-11-30 2023-03-10 Negative electrode plate, secondary battery, battery module, battery pack, and power consuming device

Publications (1)

Publication Number Publication Date
WO2023097433A1 true WO2023097433A1 (zh) 2023-06-08

Family

ID=86611277

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CN2021/134346 WO2023097433A1 (zh) 2021-11-30 2021-11-30 负极极片、二次电池、电池模块、电池包和用电装置

Country Status (4)

Country Link
US (1) US20230246155A1 (zh)
EP (1) EP4213235A1 (zh)
CN (1) CN116802824A (zh)
WO (1) WO2023097433A1 (zh)

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010212094A (ja) * 2009-03-10 2010-09-24 Nissan Motor Co Ltd 双極型電池
JP2013020784A (ja) * 2011-07-11 2013-01-31 Toyota Motor Corp 非水電解質二次電池
JP2016054132A (ja) * 2014-09-04 2016-04-14 トヨタ自動車株式会社 全固体電池
JP2018081792A (ja) * 2016-11-15 2018-05-24 株式会社Ｇｓユアサ 蓄電素子
JP2019016427A (ja) * 2017-07-03 2019-01-31 トヨタ自動車株式会社 二次電池システム
CN111916874A (zh) * 2020-09-08 2020-11-10 天合光能股份有限公司 电池导热结构及电池模组
CN112018326A (zh) * 2020-09-17 2020-12-01 珠海冠宇电池股份有限公司 一种负极片及包括该负极片的锂离子电池
CN113471569A (zh) * 2021-07-08 2021-10-01 宁德新能源科技有限公司 极片、电化学装置和电子装置
CN113594467A (zh) * 2021-08-17 2021-11-02 珠海冠宇电池股份有限公司 一种复合集流体和锂离子电池

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010212094A (ja) * 2009-03-10 2010-09-24 Nissan Motor Co Ltd 双極型電池
JP2013020784A (ja) * 2011-07-11 2013-01-31 Toyota Motor Corp 非水電解質二次電池
JP2016054132A (ja) * 2014-09-04 2016-04-14 トヨタ自動車株式会社 全固体電池
JP2018081792A (ja) * 2016-11-15 2018-05-24 株式会社Ｇｓユアサ 蓄電素子
JP2019016427A (ja) * 2017-07-03 2019-01-31 トヨタ自動車株式会社 二次電池システム
CN111916874A (zh) * 2020-09-08 2020-11-10 天合光能股份有限公司 电池导热结构及电池模组
CN112018326A (zh) * 2020-09-17 2020-12-01 珠海冠宇电池股份有限公司 一种负极片及包括该负极片的锂离子电池
CN113471569A (zh) * 2021-07-08 2021-10-01 宁德新能源科技有限公司 极片、电化学装置和电子装置
CN113594467A (zh) * 2021-08-17 2021-11-02 珠海冠宇电池股份有限公司 一种复合集流体和锂离子电池

Also Published As

Publication number Publication date
EP4213235A1 (en) 2023-07-19
US20230246155A1 (en) 2023-08-03
CN116802824A (zh) 2023-09-22

Similar Documents

Publication Publication Date Title
KR20220036961A (ko) 이차 전지, 이차 전지를 포함하는 전지 모듈, 전지 팩 및 장치
CN115966842A (zh) 一种隔离膜、含有其的二次电池和用电装置
WO2023029002A1 (zh) 负极集流体、含有其的二次电池、电池模块、电池包及用电装置
US20240079600A1 (en) Cathode plate, secondary battery, battery module, battery pack, and electric device
WO2024012166A1 (zh) 二次电池及用电装置
WO2023082924A1 (zh) 极片、锂离子电池、电池模块、电池包及用电装置
WO2023130910A1 (zh) 电池极片的制备方法、电池极片和二次电池
WO2023050842A1 (zh) 复合隔离膜、电化学储能装置及用电装置
WO2024021018A1 (zh) 干法电极用底涂胶及其制备方法、复合集流体、电池极片、二次电池、电池模块、电池包和用电装置
WO2023137624A1 (zh) 二次电池、电池模块、电池包以及用电装置
WO2022199301A1 (zh) 一种锂离子电池的阳极极片及其应用
WO2023060529A1 (zh) 锂离子电池
WO2023087218A1 (zh) 负极极片及其制备方法、二次电池、电池模块、电池包和用电装置
WO2023097433A1 (zh) 负极极片、二次电池、电池模块、电池包和用电装置
CN115810863A (zh) 隔离膜及其制备方法、二次电池、电池模块、电池包和用电装置
JP2023547000A (ja) シリコンカーボン負極材料、負極極板、二次電池、電池モジュール、電池パック及び電力消費装置
WO2023133882A1 (zh) 隔膜及其相关的二次电池、电池模块、电池包和用电装置
WO2023141954A1 (zh) 锂离子电池、电池模块、电池包和用电装置
WO2023065128A1 (zh) 负极极片、二次电池、电池模块、电池包和用电装置
WO2023130212A1 (zh) 一种锂离子二次电池、电池模块、电池包和用电装置
WO2023115431A1 (zh) 二次电池
WO2023060534A1 (zh) 一种二次电池
WO2023050834A1 (zh) 一种二次电池、含有其的电池模块、电池包及用电装置
WO2023159373A1 (zh) 极片、电极组件及二次电池
WO2024060176A1 (zh) 复合集流体及其制作方法、电极片、二次电池和用电装置

Legal Events

Date Code Title Description
ENP Entry into the national phase

Ref document number: 2021956260

Country of ref document: EP

Effective date: 20230314

WWE Wipo information: entry into national phase

Ref document number: 202180092464.8

Country of ref document: CN