WO2022205099A1 - 电化学装置及包含其的电子装置 - Google Patents

电化学装置及包含其的电子装置 Download PDF

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WO2022205099A1
WO2022205099A1 PCT/CN2021/084482 CN2021084482W WO2022205099A1 WO 2022205099 A1 WO2022205099 A1 WO 2022205099A1 CN 2021084482 W CN2021084482 W CN 2021084482W WO 2022205099 A1 WO2022205099 A1 WO 2022205099A1
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negative electrode
region
active material
lithium
material layer
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PCT/CN2021/084482
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English (en)
French (fr)
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刘俊飞
唐超
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宁德新能源科技有限公司
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Priority to JP2023555401A priority Critical patent/JP2024512402A/ja
Priority to KR1020237026931A priority patent/KR20230124750A/ko
Priority to EP21933770.6A priority patent/EP4318710A1/en
Priority to BR112023019946A priority patent/BR112023019946A2/pt
Priority to CN202180004206.XA priority patent/CN114051662A/zh
Priority to PCT/CN2021/084482 priority patent/WO2022205099A1/zh
Publication of WO2022205099A1 publication Critical patent/WO2022205099A1/zh
Priority to US18/374,786 priority patent/US20240047749A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0568—Liquid materials characterised by the solutes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present application relates to the field of energy storage technology, in particular to an electrochemical device and an electronic device including the same, in particular to a lithium ion battery.
  • Electrochemical devices e.g., lithium-ion batteries
  • smart products including mobile phones
  • notebooks, cameras and other electronic products electric vehicles, power tools, drones, intelligent robots and large-scale energy storage and other fields and industries.
  • people have put forward more requirements and challenges for the power supply of electronic products, such as thinner, lighter, more diverse shapes, and higher volumetric energy density. and mass energy density, higher safety and higher power, etc.
  • an active material layer is usually formed on the surface of the current collector by coating.
  • the thinning of the edge thickness caused by this coating method is unavoidable, which has a negative impact on the performance of the electrochemical device, especially the cycle performance.
  • Embodiments of the present application attempt to solve, at least to some extent, at least one problem in the related art by providing an electrochemical device and an electronic device including the same.
  • the present application provides an electrochemical device comprising a negative electrode and an electrolyte, wherein: the negative electrode comprises a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector,
  • the negative electrode active material layer includes a first region and a second region, the thickness D1 of the first region is smaller than the average thickness D2 of the second region, and the electrolyte contains a salt having PO bonds, based on per 1 cm 2.
  • the content of the salt having a PO bond is less than or equal to 0.05 g.
  • D1 and D2 satisfy: 0 ⁇ D1 ⁇ D2 ⁇ 97%.
  • the salt with PO bond includes LiPO 2 F 2 , NaPO 2 F 2 , KPO 2 F 2 , CsPO 2 F 2 , lithium difluorobisoxalate phosphate (LiDFOP), lithium tetrafluorooxalate phosphate (LiTFOP) at least one.
  • LiDFOP lithium difluorobisoxalate phosphate
  • LiTFOP lithium tetrafluorooxalate phosphate
  • the electrolyte further includes a first additive including 1,3-propanesultone, fluoroethylene carbonate, vinylene carbonate, succinic anhydride or maleic anhydride at least one of them.
  • the content of the first additive is 0.001 g to 0.2 g per 1 cm 2 of the first region.
  • the electrolyte further includes a second additive
  • the second additive includes lithium tetrafluoroborate (LiBF 4 ), lithium bis(fluorosulfonyl)imide (LiFSI), bis(trifluoromethane) Lithium sulfonyl)imide (LiTFSI), Lithium 4,5-dicyano-2-trifluoromethylimidazolium (LiTDI), Lithium Difluorooxalate Borate (LiDFOB), Lithium Bisoxalate Borate (LiBOB), Hexylene Dioxide Nitrile (AND), Succinonitrile (SN), 1,3,6-Hexanetrinitrile (HTCN), 1,2,3-Tris(2-cyanooxy)propane, 1,4-dicyano-2 - At least one of butene or glutaronitrile or tris(2-cyanoethyl)phosphine, the content of the second additive is
  • the first region is located at the edge of the negative electrode active material layer, and the width of the first region is less than or equal to 15 ⁇ m.
  • the area of the first region is less than or equal to 20% of the total area of the negative electrode active material layer.
  • the negative electrode active material layer includes a negative electrode active material, and the median particle diameter of the negative electrode active material is 5 ⁇ m to 20 ⁇ m.
  • the compaction density of the negative electrode is 1.3 g/cm 3 to 1.8 g/cm 3 .
  • the present application provides an electronic device comprising the electrochemical device as described above.
  • FIG. 1 shows a schematic diagram of the thinned region of the anode active material layer.
  • FIG. 2 shows a schematic diagram of the location of the thinned region of the negative electrode active material layer.
  • FIG. 3 shows a schematic diagram of the location of the thinned region of yet another negative electrode active material layer.
  • FIG. 4 shows a schematic diagram of the location of the thinning region of yet another negative electrode active material layer.
  • a term may refer to a range of variation less than or equal to ⁇ 10% of the numerical value, such as less than or equal to ⁇ 5%, less than or equal to ⁇ 4%, less than or equal to ⁇ 3%, Less than or equal to ⁇ 2%, less than or equal to ⁇ 1%, less than or equal to ⁇ 0.5%, less than or equal to ⁇ 0.1%, or less than or equal to ⁇ 0.05%.
  • a list of items linked by the term "at least one of” can mean any combination of the listed items.
  • the phrase "at least one of A and B” means A only; B only; or A and B.
  • the phrase "at least one of A, B, and C” means A only; or B only; C only; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C.
  • Item A may contain a single element or multiple elements.
  • Item B may contain a single element or multiple elements.
  • Item C may contain a single element or multiple elements.
  • an electrode When preparing an electrochemical device (eg, a lithium ion battery), an electrode is prepared by applying an active material slurry on a current collector by a coating method to form an active material layer.
  • the active material layer on the current collector inevitably has a phenomenon that the thickness of the edge region is smaller than the thickness of the center region.
  • the active material layer on the current collector includes a first region of gradually decreasing thickness (ie, a thinned region) and a second region of substantially uniform thickness. The presence of thinned regions can negatively impact the performance of electrochemical devices.
  • the contact interface between the electrolyte and the negative electrode becomes poor, and the stress is not uniform, resulting in an increase in polarization; the negative electrode has insufficient space for lithium insertion; there is a difference in current distribution in the negative electrode active material layer during the initial charging process. It retards film formation in the thinned area.
  • the present application makes up for the negative effect of the thinned region of the negative electrode active material layer by using an electrolyte containing a specific content of a salt with a P-O bond, thereby improving the cycle performance of the electrochemical device.
  • the present application provides an electrochemical device comprising a positive electrode, a negative electrode and an electrolyte as described below.
  • the electrochemical device further includes a separator disposed between the positive electrode and the negative electrode.
  • the negative electrode used in the electrochemical device of the present application includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, the negative electrode active material layer includes a first region and a second region, the first region The thickness D1 of any position of a region is smaller than the average thickness D2 of the second region.
  • D1 and D2 satisfy: 0 ⁇ D1 ⁇ D2 ⁇ 97%.
  • the first region is located at the edge of the negative electrode active material layer, and the width of the first region is less than or equal to 15 ⁇ m. In some embodiments, the width of the first region is less than or equal to 12 ⁇ m. In some embodiments, the width of the first region is less than or equal to 10 ⁇ m. In some embodiments, the width of the first region is less than or equal to 8 ⁇ m. In some embodiments, the width of the first region is less than or equal to 5 ⁇ m.
  • the “width of the first region” refers to the point where the thickness of the negative electrode active material layer reaches 97% of the thickness of the central region of the negative electrode active material layer from the junction position of the negative electrode current collector with the uncoated negative electrode active material and the coated negative electrode active material. distance in %.
  • the “width of the first region” may also be the distance from the edge position of the negative electrode active material layer to when the thickness of the negative electrode active material layer reaches 97% of the thickness of the central region of the negative electrode active material layer. When the width of the first region is within the above range, the thinned region of the negative electrode active material layer is smaller, which helps to improve the cycle performance of the electrochemical device.
  • the area of the first region is less than or equal to 20% of the total area of the negative active material layer. In some embodiments, the area of the first region is less than or equal to 18% of the total area of the negative active material layer. In some embodiments, the area of the first region is less than or equal to 15% of the total area of the negative active material layer. In some embodiments, the area of the first region is less than or equal to 12% of the total area of the negative active material layer. In some embodiments, the area of the first region is less than or equal to 10% of the total area of the negative electrode active material layer. In some embodiments, the area of the first region is less than or equal to 8% of the total area of the negative active material layer.
  • the area of the first region is less than or equal to 5% of the total area of the negative active material layer.
  • the ratio of the area of the first region to the total area of the negative electrode active material layer is within the above-mentioned range, the negative impact caused by the thinning area of the negative electrode active material layer can be effectively reduced, the additional process cost is not greatly increased, and the Improve the cycle performance of electrochemical devices.
  • the anode active material layer includes an anode active material.
  • the negative electrode active material is any substance that can electrochemically occlude and release metal ions such as lithium ions.
  • the negative electrode active material includes one or more of carbonaceous materials, silicon carbon materials, alloy materials, or lithium-containing metal composite oxide materials.
  • the median particle size of the negative electrode active material is 5 ⁇ m to 20 ⁇ m. In some embodiments, the median particle size of the negative electrode active material is 8 ⁇ m to 18 ⁇ m. In some embodiments, the negative electrode active material has a median particle size of 10 ⁇ m to 15 ⁇ m. In some embodiments, the median particle size of the negative electrode active material is 5 ⁇ m, 8 ⁇ m, 10 ⁇ m, 12 ⁇ m, 15 ⁇ m, 18 ⁇ m, 20 ⁇ m, or a range composed of any two of the above values.
  • the “median particle size” refers to the particle size of the negative electrode active material in the volume-based particle size distribution from the small particle size side to the cumulative 50% volume, that is, the volume of the negative electrode active material smaller than this particle size accounts for the total negative electrode active material. 50% of the volume.
  • the median particle diameter of the negative electrode active material is within the above range, the cycle performance of the electrochemical device can be further improved.
  • the anode active material layer further includes an anode binder.
  • the negative electrode binder includes one or more of styrene-butadiene rubber, fluororubber, and ethylene propylene diene.
  • the negative electrode active material layer further includes a negative electrode conductive agent.
  • the negative electrode conductive agent includes one or more of a conductive metal material and a conductive polymer.
  • the negative electrode conductive agent includes one or more of carbon materials and the like.
  • the carbon material includes, but is not limited to, graphite, carbon black, acetylene black, and ketjen black.
  • the negative electrode has a compacted density of 1.3 g/cm 3 to 1.8 g/cm 3 . In some embodiments, the negative electrode has a compacted density of 1.4 g/cm 3 to 1.6 g/cm 3 . In some embodiments, the negative electrode has a compacted density of 1.5 g/cm 3 .
  • the negative electrode current collector includes a negative electrode conductive material.
  • the negative electrode current collector includes, but is not limited to, copper, nickel, and stainless steel.
  • the surface of the negative electrode current collector is roughened, and the roughened surface can improve the adhesion of the negative electrode active material.
  • the roughened negative current collector includes, but is not limited to, electrolytic copper foil.
  • the negative electrode current collector has a negative electrode active material layer on one surface.
  • a negative active material layer is present on both surfaces of the negative current collector in some embodiments.
  • at least one surface of the negative electrode current collector includes a region where the negative electrode active material layer is not disposed, also referred to as an empty foil region.
  • the electrolyte used in the electrochemical device of the present application contains a salt having a PO bond, and the content of the salt having a PO bond is less than or equal to 0.05 g per 1 cm 2 of the first region.
  • the salt with a P-O bond is an inorganic salt with a P-O bond.
  • the salt with PO bond described in comprises LiPO 2 F 2 , NaPO 2 F 2 , KPO 2 F 2 , CsPO 2 F 2 , lithium difluorobisoxalate phosphate or lithium difluorobisoxalate phosphate (LIDODFP ) at least one of them.
  • the content of the salt having PO bonds is less than or equal to 0.04 g per 1 cm 2 of the first area. In some embodiments, the content of the salt having PO bonds is less than or equal to 0.03 g per 1 cm 2 of the first area. In some embodiments, the content of the salt having PO bonds is less than or equal to 0.02 g per 1 cm 2 of the first area. In some embodiments, the content of the salt having PO bonds is less than or equal to 0.01 g per 1 cm 2 of the first area. In some embodiments, the content of the salt having PO bonds is less than or equal to 0.005 g per 1 cm 2 of the first area.
  • the content of the salt having a PO bond is less than or equal to 0.001 g per 1 cm 2 of the first area. In some embodiments, the content of the salt having PO bonds is less than or equal to 0.0005 g per 1 cm 2 of the first area.
  • salts with P-O bonds will preferentially enrich on the surface of the negative electrode, which not only contributes to the film formation of the second region of the negative electrode active material layer, but more importantly, it also contributes to the negative electrode activity
  • the formation of the film in the first region of the material layer and the enhancement of the stability of the formed film can reduce the occurrence of side reactions in the first region of the negative electrode active material layer, reduce the thickness variation caused by by-products in the first region, and improve the electrochemical performance. Cycling stability of the device.
  • the use of a salt having a P-O bond helps to reduce the negative effects caused by the difference in current distribution between the first region and the second region of the negative electrode active material layer, ensuring the effectiveness of film formation in the first region of the negative electrode active material layer .
  • the inclusion of the salt having the P-O bond in the above-mentioned content in the electrolyte solution can reduce the adverse effect caused by the thinned region of the negative electrode active material layer, thereby remarkably improving the cycle performance of the electrochemical device.
  • the electrolyte further includes a first additive, and the reduction potential of the first additive is below 2.5V.
  • the reduction potential of the first additive is below 2.5V, it can form a protective layer on the surface of the negative electrode, which helps to reduce the adverse effects caused by the thinning area of the negative electrode active material layer, thereby further significantly improving the cycle performance of the electrochemical device. .
  • the first additive comprises 1,3-propanesultone (PS), fluoroethylene carbonate (FEC), vinylene carbonate (VC), succinic anhydride or maleic anhydride at least one.
  • the first additive comprises 1,3-propanesultone (PS) and fluoroethylene carbonate (FEC).
  • PS 1,3-propanesultone
  • FEC fluoroethylene carbonate
  • the weight percentage of the 1,3-propanesultone in the electrolyte is greater than the weight percentage of the fluoroethylene carbonate in the electrolyte. In some embodiments, the ratio of the weight percent of the 1,3-propanesultone in the electrolyte to the weight percent of the fluoroethylene carbonate in the electrolyte is less than or equal to 1.5. When the weight percent ratio is within this range, the cycle performance of the electrochemical device can be improved, and the gas production of the electrochemical device can be reduced at the same time.
  • the first additive includes 1,3-propanesultone (PS), fluoroethylene carbonate (FEC), and vinylene carbonate (VC).
  • PS 1,3-propanesultone
  • FEC fluoroethylene carbonate
  • VC vinylene carbonate
  • the content of the first additive is 0.001 g to 0.2 g per 1 cm 2 of the first area. In some embodiments, the content of the first additive is 0.005 g to 0.2 g per 1 cm 2 of the first area. In some embodiments, the content of the first additive is 0.01 g to 0.15 g per 1 cm 2 of the first area. In some embodiments, the content of the first additive is 0.05 g to 0.13 g per 1 cm 2 of the first area. In some embodiments, the content of the first additive is 0.08 g to 0.1 g per 1 cm 2 of the first area.
  • the content of the first additive is 0.001 g, 0.005 g, 0.01 g, 0.03 g, 0.05 g, 0.07 g, 0.1 g, 0.15 g, 0.2 g per 1 cm 2 of the first area or within the range consisting of any two of the above values.
  • the content of the first additive in the electrolyte is within the above range, it is helpful to further significantly improve the cycle performance of the electrochemical device.
  • the electrolyte further includes a second additive including lithium tetrafluoroborate (LiBF 4 ), lithium bisfluorosulfonimide (LiFSI), lithium bistrifluorosulfonimide (LiTFSI), Lithium 4,5-dicyano-2-trifluoromethylimidazolium (LiTDI), Lithium Difluorooxalate Borate (LiDFOB), Lithium Bisoxalate Borate, Adiponitrile (ADN), Succinonitrile, 1, 3,6-hexanetrinitrile (HTCN), 1,2,3-tris(2-cyanooxy)propane, 1,4-dicyano-2-butene or glutaronitrile or tris(2-cyano) at least one of ethyl) phosphine.
  • LiBF 4 lithium tetrafluoroborate
  • LiFSI lithium bisfluorosulfonimide
  • LiTFSI lithium bistrifluorosulfon
  • the second additive includes LiBF4 and LiDFOB. In some embodiments, the second additive includes HTCN and LiDFOB. In some embodiments, the second additive includes LiBF4 , LiDFOB, and LiTFSI. In some embodiments, the second additive includes HTCN, LiDFOB, and LiTFSI.
  • the second additive can form a protective layer on the surface of the positive electrode to reduce the generation of side reactions at the positive electrode, and can also reduce the dissolution of the metal ions of the positive electrode.
  • the stability of the negative protective film is affected by the products of side reactions at the positive electrode. Therefore, the second additive can protect the negative electrode while protecting the positive electrode, thereby helping to improve the cycle performance of the electrochemical device.
  • the content of the second additive is 0.1 wt % to 10 wt % based on the weight of the electrolyte.
  • the content of the second additive is 0.2 wt % to 5 wt % based on the weight of the electrolyte.
  • the content of the second additive is 0.5 wt % to 3 wt % based on the weight of the electrolyte.
  • the content of the second additive is 1 wt % to 2 wt % based on the weight of the electrolyte.
  • the content of the second additive is 0.1 wt %, 0.5 wt %, 1 wt %, 2 wt %, 3 wt %, 4 wt %, 5 wt %, 6 wt %, 7 wt % , 8 wt %, 9 wt %, 10 wt % or within the range composed of any two of the above values.
  • the content of the second additive in the electrolyte is within the above range, it is helpful to further significantly improve the cycle performance of the electrochemical device.
  • LiPF 6 is included in the electrolyte that can be used in the present application.
  • the concentration of LiPF 6 is in the range of 0.8 mol/L to 3 mol/L, 0.8 mol/L to 2.5 mol/L, 0.8 mol/L In the range of L to 2 mol/L or the range of 1 mol/L to 2 mol/L.
  • the concentration of the lithium salt is about 1 mol/L, about 1.15 mol/L, about 1.2 mol/L, about 1.5 mol/L, about 2 mol/L, or about 2.5 mol/L.
  • Solvents that can be used in the electrolyte of the embodiments of the present application include, but are not limited to: cyclic carbonate, chain carbonate, cyclic carboxylate, chain carboxylate, cyclic ether, chain ether, phosphorus-containing Organic solvents, sulfur-containing organic solvents and aromatic fluorinated solvents.
  • cyclic carbonates include, but are not limited to: ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate. In some embodiments, the cyclic carbonate has 3-6 carbon atoms.
  • chain carbonates include, but are not limited to: dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate (DEC), methyl-n-propyl carbonate, ethyl-n-propyl carbonate, Chain carbonates such as di-n-propyl carbonate, as chain carbonates substituted by fluorine, such as bis(fluoromethyl)carbonate, bis(difluoromethyl)carbonate, bis(trifluoromethyl)carbonate , bis(2-fluoroethyl)carbonate, bis(2,2-difluoroethyl)carbonate, bis(2,2,2-trifluoroethyl)carbonate, 2-fluoroethylmethylcarbonate esters, 2,2-difluoroethylmethylcarbonate and 2,2,2-trifluoroethylmethylcarbonate.
  • fluorine such as bis(fluoromethyl)carbonate, bis(difluoromethyl)carbonate, bis(trifluoromethyl)carbonate
  • cyclic carboxylic acid esters include, but are not limited to: gamma-butyrolactone and gamma-valerolactone.
  • some of the hydrogen atoms of the cyclic carboxylate may be replaced by fluorine.
  • chain carboxylates include, but are not limited to: methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, sec-butyl acetate, isobutyl acetate, tert-butyl acetate Butyl, methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, methyl isobutyrate, ethyl isobutyrate , methyl valerate, ethyl valerate, methyl pivalate and ethyl pivalate.
  • fluorine-substituted chain carboxylates include, but are not limited to: methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, and 2,2 trifluoroacetate , 2-trifluoroethyl ester.
  • cyclic ethers include, but are not limited to: tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 2-methyl 1,3-dioxolane, 4-methyl 1 , 3-dioxolane, 1,3-dioxane, 1,4-dioxane and dimethoxypropane.
  • chain ethers include, but are not limited to: dimethoxymethane, 1,1-dimethoxyethane, 1,2-dimethoxyethane, diethoxymethane, 1 ,1-diethoxyethane, 1,2-diethoxyethane, ethoxymethoxymethane, 1,1-ethoxymethoxyethane and 1,2-ethoxymethyl oxyethane.
  • phosphorus-containing organic solvents include, but are not limited to: trimethyl phosphate, triethyl phosphate, dimethyl ethyl phosphate, methyl diethyl phosphate, ethylene methyl phosphate, ethylene phosphate Ethyl ethyl, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, triphenyl phosphite, tris(2,2,2-trifluoroethyl) phosphate and tris(2,2, phosphate) 3,3,3-pentafluoropropyl) ester.
  • sulfur-containing organic solvents include, but are not limited to: sulfolane, 2-methyl sulfolane, 3-methyl sulfolane, dimethyl sulfone, diethyl sulfone, ethyl methyl sulfone, methyl propyl sulfone Sulfone, dimethyl sulfoxide, methyl methanesulfonate, ethyl methanesulfonate, methyl ethanesulfonate, ethyl ethanesulfonate, dimethyl sulfate, diethyl sulfate, and dibutyl sulfate.
  • some of the hydrogen atoms of the sulfur-containing organic solvent may be replaced by fluorine.
  • aromatic fluorine-containing solvents include, but are not limited to: fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, and trifluoromethylbenzene.
  • the solvent used in the electrolyte of the present application includes one or more of the above.
  • the solvent used in the electrolyte of the present application includes cyclic carbonate, chain carbonate, cyclic carboxylate, chain carboxylate, and combinations thereof.
  • the solvent used in the electrolyte of the present application comprises an organic solvent selected from the group consisting of: ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propionic acid Propyl ester, n-propyl acetate, ethyl acetate, and combinations thereof.
  • the solvent used in the electrolyte of the present application comprises: ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, ⁇ -butyrolactone or a combination thereof .
  • the positive electrode includes a positive electrode current collector and a positive electrode active material disposed on the positive electrode current collector.
  • the specific types of the positive electrode active materials are not specifically limited, and can be selected according to requirements.
  • the cathode active material includes a cathode material capable of absorbing and releasing lithium (Li).
  • cathode materials capable of absorbing/releasing lithium (Li) may include lithium cobalt oxide, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium manganate, lithium iron manganese phosphate, lithium vanadium phosphate, lithium vanadyl phosphate, phosphoric acid Lithium iron, lithium titanate, and lithium-rich manganese-based materials.
  • the chemical formula of lithium cobalt oxide can be as chemical formula 1:
  • M1 represents selected from nickel (Ni), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), Copper (Cu), Zinc (Zn), Molybdenum (Mo), Tin (Sn), Calcium (Ca), Strontium (Sr), Tungsten (W), Yttrium (Y), Lanthanum (La), Zirconium (Zr), At least one element of silicon (Si), fluorine (F) or sulfur (S), the values of x, a, b and c are respectively in the following ranges: 0.8 ⁇ x ⁇ 1.2, 0.8 ⁇ a ⁇ 1, 0 ⁇ b ⁇ 0.2, -0.1 ⁇ c ⁇ 0.2.
  • nickel cobalt lithium manganate or nickel cobalt aluminate can be as chemical formula 2:
  • M2 represents selected from cobalt (Co), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), Copper (Cu), Zinc (Zn), Molybdenum (Mo), Tin (Sn), Calcium (Ca), Strontium (Sr), Tungsten (W), Zirconium (Zr), Silicon (Si), Fluorine (F) or At least one element of sulfur (S), the values of y, d, e and f are respectively in the following ranges: 0.8 ⁇ y ⁇ 1.2, 0.3 ⁇ d ⁇ 0.98, 0.02 ⁇ e ⁇ 0.7, -0.1 ⁇ f ⁇ 0.2.
  • the chemical formula of lithium manganate can be as chemical formula 3:
  • M3 represents selected from cobalt (Co), nickel (Ni), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), At least one element of copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), niobium (Nb), tantalum (Ta) or tungsten (W) , the values of z, g and h are respectively in the following ranges: 0.8 ⁇ z ⁇ 1.2, 0 ⁇ g ⁇ 1.0 and -0.2 ⁇ h ⁇ 0.2.
  • the cathode active material layer may have a coating on the surface, or may be mixed with another compound having a coating.
  • the coating may include elements selected from the group consisting of oxides of the coating elements, hydroxides of the coating elements, oxyhydroxides of the coating elements, oxycarbonates of the coating elements, and hydroxycarbonates of the coating elements. At least one coating element compound selected from hydroxycarbonate).
  • the compound used for the coating can be amorphous or crystalline.
  • Coating elements contained in the coating may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, F or mixtures thereof.
  • the coating can be applied by any method as long as the method does not adversely affect the performance of the positive electrode active material.
  • the method may include any coating method well known to those of ordinary skill in the art, such as spraying, dipping, and the like.
  • the positive electrode active material layer further includes a binder, and optionally a positive electrode conductive material.
  • the binder can improve the bonding of the positive electrode active material particles to each other, and also improve the bonding of the positive electrode active material and the current collector.
  • binders include polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene , polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylic (esterified) styrene-butadiene rubber, epoxy resin, nylon, etc.
  • the positive electrode active material layer includes a positive electrode conductive material, thereby imparting conductivity to the electrode.
  • the positive electrode conductive material may include any conductive material as long as it does not cause chemical changes.
  • Non-limiting examples of positive conductive materials include carbon-based materials (eg, natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (eg, metal powder, metal fiber, etc., These include, for example, copper, nickel, aluminum, silver, etc.), conductive polymers (eg, polyphenylene derivatives), and mixtures thereof.
  • the positive electrode current collector for the electrochemical device according to the present application may be aluminum (Al), but is not limited thereto.
  • the electrochemical device of the present application is provided with a separator between the positive electrode and the negative electrode, so as to prevent current short circuit caused by the contact of the two pole pieces, while allowing lithium ions to pass through.
  • the separator includes polymers (eg, synthetic resins) or inorganics (eg, ceramics), or the like, formed from materials that are stable to the electrolyte of the present application.
  • the separator includes a porous membrane made of the polymer or the inorganic.
  • the separator includes a laminated film in which two or more porous films are laminated.
  • the polymers include, but are not limited to, polytetrafluoroethylene, polypropylene, and polyethylene.
  • the separator includes the above-mentioned porous film (base material layer) and a polymer compound layer provided on one or both surfaces of the base material layer, which can improve the separator relative to the positive electrode and the negative electrode The adhesiveness is improved, and the deflection of the electrode sheet is suppressed, thereby suppressing the decomposition reaction of the electrolytic solution and suppressing the liquid leakage of the electrolytic solution impregnating the base material layer.
  • the separator includes the above-mentioned porous film (base material layer) and a polymer compound layer provided on one or both surfaces of the base material layer, which can improve the separator relative to the positive electrode and the negative electrode The adhesiveness is improved, and the deflection of the electrode sheet is suppressed, thereby suppressing the decomposition reaction of the electrolytic solution and suppressing the liquid leakage of the electrolytic solution impregnating the base material layer.
  • the polymer compound layer includes, but is not limited to, polyvinylidene fluoride.
  • Polyvinylidene fluoride has excellent physical strength and electrochemical stability.
  • the polymer compound layer may be formed by: after preparing a solution in which the polymer material is dissolved, coating the base material layer with the solution or soaking the base material layer in the solution, and finally drying.
  • the electrochemical device of the present application includes any device in which an electrochemical reaction occurs, and specific examples thereof include all kinds of primary batteries or secondary batteries.
  • the electrochemical device is a lithium secondary battery, including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.
  • the electrochemical device of the present application is not particularly limited, and it can be used for any use known in the art.
  • the electrochemical devices of the present application may be used in, but are not limited to, notebook computers, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, headsets stereo headphones, VCRs, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power, motors, cars, motorcycles, power Bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.
  • the negative electrode slurry was evenly coated on the copper foil, dried at 85°C, and then after cold pressing, die-cutting, slitting and winding, dried under vacuum at 120°C for 12 hours to obtain a length of 1544.0 ⁇
  • a negative electrode with a width of 5.0 mm and a width of 66.5 ⁇ 1.0 mm, the total area of the single-sided negative electrode active material layer (on one side) is 1544.0 ⁇ 66.5 102676 (mm 2 ), about 1027 cm 2 , and the compaction density of the negative electrode is 1.6 g /cm 3 .
  • the positive active material Li(Ni 0.8 Co 0.08 Mn 0.07 )Al 0.05 O 2 , the conductive agent Super-P and polyvinylidene fluoride were mixed with N-methylpyrrolidone (NMP) in a mass ratio of 97:1.4:1.6, and stirred. uniform, and a positive electrode slurry was obtained, wherein the solid content of the positive electrode slurry was 72 wt %.
  • the positive electrode slurry was coated on aluminum foil, dried at 85°C, and then subjected to cold pressing, die cutting, slitting, and tab welding, and then dried under vacuum at 85°C for 4 hours to obtain a positive electrode.
  • a salt having a P-O bond, a first additive and/or a second additive are added to the base electrolyte to obtain an electrolyte.
  • PE polyethylene
  • the obtained positive electrode, separator and negative electrode are wound in order to form a bare cell, and the bare cell is placed in an outer packaging foil, leaving a liquid injection port.
  • the electrolyte is poured from the injection port, packaged, and then subjected to chemical formation (charged to 3.3V with a constant current of 0.02C, and then charged to 3.6V with a constant current of 0.1C), capacity and other processes to obtain a lithium-ion battery (thickness is about 9.1mm). , width is about 49mm, length is about 74mm).
  • Cycle capacity retention rate C1/C0 ⁇ 100%
  • Cyclic thickness expansion ratio (H1-H0)/H0 ⁇ 100%.
  • the thickness of the surface of the negative electrode active material layer away from the current collector on any single side to the surface of the current collector that the negative electrode active material layer contacts is It is D1
  • the thickness of 5 points is continuously tested.
  • 3 points satisfy D1>D2 ⁇ 97% the distance from the closest point near the edge of the negative electrode active material layer to the edge of the negative electrode active material layer is used as the negative electrode active material.
  • the above thickness test units are accurate to 0.01mm. During the test, the selection of the cross section needs to include the first region and the second region of the negative electrode active material layer.
  • the test is carried out with the central axis of the width as the cross-section using substantially the same method as described above.
  • the tests are carried out with the central axis of the length and the central axis of the width as the cross-sections using basically the same method as above.
  • the lithium-ion battery was discharged at a rate of 0.2C to a voltage of 2.8V, the weight of the lithium-ion battery was weighed and recorded as M 0 , the tabs and the outer packaging were cut off to obtain a bare cell, and the electrolyte was obtained by centrifuging the bare cell, Then, the content of anions in the electrolyte was tested by ion chromatography IC (Model: Thermo Fisher Scientific, AQUION) to obtain the relative content Q of salts with PO bonds in the electrolyte.
  • ion chromatography IC Model: Thermo Fisher Scientific, AQUION
  • the mass of the salt with PO bond in the bare cell is calculated by the following formula: (M 0 -M 1 ) ⁇ Q.
  • the type of the first additive and the second additive were tested using an ion chromatography IC (model: Thermo Fisher Scientific, AQUION) or a gas chromatograph GC (model: Agilent 7890A-5975C).
  • Table 1 shows the effects of the electrolyte composition and the first region in the negative electrode active material layer on the cycle performance of lithium ion batteries in each of the comparative examples and examples.
  • the unit area content of the salt with PO bond or the first additive refers to the weight of the salt with PO bond or the first additive per 1 cm 2 of the first region.
  • the total area of the single-sided negative electrode active material layer was 1027 cm 2 .
  • the cycle capacity retention rate of the lithium ion battery can be further improved and the thickness expansion rate thereof can be reduced.
  • the cycle capacity retention rate of the lithium ion battery can be further improved and the thickness expansion rate thereof can be reduced.
  • the cycle capacity retention rate of the lithium ion battery can be further improved, and the thickness expansion rate thereof can be reduced.
  • the cycle capacity retention rate of the lithium ion battery can be further improved and the thickness expansion rate thereof can be reduced.
  • Table 2 shows the effect of the median particle size of anode active materials on the cycling performance of Li-ion batteries.
  • the preparation methods of Examples 38-41 are basically the same as those of Example 3, and the difference is only in the parameters shown in Table 2.
  • the cycle capacity retention rate of the lithium-ion battery can be further improved and its thickness expansion rate can be reduced.

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Abstract

本申请涉及一种电化学装置及包含其的电子装置。具体而言，本申请提供一种电化学装置，其包括负极和电解液，其中：所述负极包括负极集流体和设置于所述负极集流体的至少一个表面的负极活性材料层，所述负极活性材料层包括第一区域和第二区域，所述第一区域的任意位置的厚度小于所述第二区域的平均厚度，并且所述电解液包含特定含量的具有P-O键的盐。本申请的电化学装置具有优异的循环性能。

Description

电化学装置及包含其的电子装置 技术领域
本申请涉及储能技术领域，尤其涉及一种电化学装置及包含其的电子装置，特别是关于锂离子电池。
背景技术
电化学装置(例如，锂离子电池)因其能量密度高、工作电压高、重量轻、自放电率低、循环寿命长、无记忆效应和环境友好等优点已被广泛用于智能产品(包括手机、笔记本、相机等电子产品)、电动汽车、电动工具、无人机、智能机器人及规模化储能等领域与产业。然而，随着信息通讯技术的日新月异及市场需求的多样性变化，人们对电子产品的电源提出了更多要求和挑战，例如更薄、更轻、外形更多样化、更高的体积能量密度和质量能量密度、更高的安全性和更高的功率等。
电化学装置的制备过程中通常采用涂布方式在集流体表面形成活性材料层。然而，受生产工艺的限制，这种涂覆方式带来的边缘厚度变薄问题难以避免，其对电化学装置的性能，尤其是循环性能，具有负面影响。
鉴于此，确有必要提供一种具有改进的循环性能的电化学装置及包含其的电子装置。
发明内容
本申请的实施例通过提供一种电化学装置及包含其的电子装置以试图在至少某种程度上解决至少一种存在于相关领域中的问题。
在一个实施例中，本申请提供了一种电化学装置，其包括负极和电解液，其中：所述负极包括负极集流体和设置于所述负极集流体的至少一个表面的负极活性材料层，所述负极活性材料层包括第一区域和第二区域，所述第一区域的的厚度D1小于所述第二区域的平均厚度D2，并且所述电解液包含具有P-O键的盐，基于每1cm 2所述第一区域，所述具有P-O键的盐的含量为小于或等于0.05g。
根据本申请的实施例，D1和D2满足：0＜D1≤D2×97％。
根据本申请的实施例，所述具有P-O键的盐包括LiPO 2F 2、NaPO 2F 2、KPO 2F 2、CsPO 2F 2、二氟双草酸磷酸锂(LiDFOP)、四氟草酸磷酸锂(LiTFOP)中的至少一种。
根据本申请的实施例，所述电解液进一步包括第一添加剂，所述第一添加剂包括 1,3-丙磺内酯、氟代碳酸乙烯酯、碳酸亚乙烯酯、丁二酸酐或马来酸酐中的至少一种。
根据本申请的实施例，基于每1cm 2所述第一区域，所述第一添加剂的含量为0.001g至0.2g。
根据本申请的实施例，所述电解液进一步包括第二添加剂，所述第二添加剂包括四氟硼酸锂(LiBF 4)、双(氟磺酰)亚胺锂(LiFSI)、双(三氟甲基磺酰)亚胺锂(LiTFSI)、4,5-二氰基-2-三氟甲基咪唑锂(LiTDI)、二氟草酸硼酸锂(LiDFOB)、双草酸硼酸锂(LiBOB)、己二腈(AND)、琥珀腈(SN)、1,3,6-己烷三腈(HTCN)、1,2,3-三(2-氰氧基)丙烷、1,4-二氰基-2-丁烯或戊二腈或三(2-氰乙基)膦中的至少一种，基于所述电解液的重量，所述第二添加剂的含量为0.1wt％至10wt％。
根据本申请的实施例，所述第一区域位于所述负极活性材料层的边缘，所述第一区域的宽度为小于或等于15μm。
根据本申请的实施例，所述第一区域面积小于或等于所述负极活性材料层总面积的20％。
根据本申请的实施例，所述负极活性材料层包括负极活性材料，所述负极活性材料的中值粒径为5μm至20μm。
根据本申请的实施例，所述负极的压实密度为1.3g/cm 3至1.8g/cm 3。
在另一个实施例中，本申请提供了一种电子装置，所述电子装置包括如上所述的电化学装置。
本申请实施例的额外层面及优点将部分地在后续说明中描述、显示、或是经由本申请实施例的实施而阐释。
附图说明
在下文中将简要地说明为了描述本申请实施例或现有技术所必要的附图以便于描述本申请的实施例。显而易见地，下文描述中的附图仅只是本申请中的部分实施例。对本领域技术人员而言，在不需要创造性劳动的前提下，依然可以根据这些附图中所例示的结构来获得其他实施例的附图。
图1展示了负极活性材料层的削薄区的示意图。
图2展示了一种负极活性材料层的削薄区位置示意图。
图3展示了又一种负极活性材料层的削薄区位置示意图。
图4展示了再一种负极活性材料层的削薄区位置示意图。
具体实施方式
本申请的实施例将会被详细的描示在下文中。在本申请说明书全文中，将相同或相似的组件以及具有相同或相似的功能的组件通过类似附图标记来表示。在此所描述的有关附图的实施例为说明性质的、图解性质的且用于提供对本申请的基本理解。本申请的实施例不应该被解释为对本申请的限制。
除非另外明确指明，本文使用的下述术语具有下文指出的含义。
术语“约”用以描述及说明小的变化。当与事件或情形结合使用时，所述术语可指代其中事件或情形精确发生的例子以及其中事件或情形极近似地发生的例子。举例来说，当结合数值使用时，术语可指代小于或等于所述数值的±10％的变化范围，例如小于或等于±5％、小于或等于±4％、小于或等于±3％、小于或等于±2％、小于或等于±1％、小于或等于±0.5％、小于或等于±0.1％、或小于或等于±0.05％。另外，有时在本文中以范围格式呈现量、比率和其它数值。应理解，此类范围格式是用于便利及简洁起见，且应灵活地理解，不仅包含明确地指定为范围限制的数值，而且包含涵盖于所述范围内的所有个别数值或子范围，如同明确地指定每一数值及子范围一般。
在具体实施方式及权利要求书中，由术语“中的至少一种”连接的项目的列表可意味着所列项目的任何组合。例如，如果列出项目A及B，那么短语“A及B中的至少一种”意味着仅A；仅B；或A及B。在另一实例中，如果列出项目A、B及C，那么短语“A、B及C中的至少一种”意味着仅A；或仅B；仅C；A及B(排除C)；A及C(排除B)；B及C(排除A)；或A、B及C的全部。项目A可包含单个元件或多个元件。项目B可包含单个元件或多个元件。项目C可包含单个元件或多个元件。
在制备电化学装置时(例如，锂离子电池)，采用涂覆方式将活性材料浆料施加在集流体上以形成活性材料层，进而制备得到电极。然而，由于所涂布的活性材料浆料具有一定的流动性且现有生产工艺具有局限性，集流体上的活性材料层不可避免地会出现边缘区域厚度小于中心区域厚度的现象。如图1所示，集流体上的活性材料层包括厚度逐渐减小的第一区域(即，削薄区)以及厚度基本均一的第二区域。削薄区的存在会对电化学装置的性能产生负面影响。例如，在负极的削薄区处，电解液与负极的接触界面变差，应力不均匀，导致极化增大；负极嵌锂空间不足；在初始充电过程中负极活性材料层存在电流分布差异，其会延缓削薄区的成膜。这些因素会导致电化学装置的循环过程中的副反应增多，易发生析锂现象，循环性能不佳。
为了解决上述问题，本申请通过使用包含特定含量的具有P-O键的盐的电解液弥补了负极活性材料层的削薄区带来的负面影响，从而改善了电化学装置的循环性能。 具体来说，本申请提供了一种电化学装置，其包括如下所述的正极、负极和电解液。在一些实施例中，所述电化学装置进一步包括设置在所述正极与所述负极之间的隔离膜。
负极
本申请的电化学装置中使用的负极包括负极集流体和设置于所述负极集流体的至少一个表面的负极活性材料层，所述负极活性材料层包括第一区域和第二区域，所述第一区域的任意位置的厚度D1小于所述第二区域的平均厚度D2。
在一些实施例中，D1和D2满足：0＜D1≤D2×97％。
在一些实施例中，所述第一区域位于所述负极活性材料层的边缘，所述第一区域的宽度为小于或等于15μm。在一些实施例中，所述第一区域的宽度为小于或等于12μm。在一些实施例中，所述第一区域的宽度为小于或等于10μm。在一些实施例中，所述第一区域的宽度为小于或等于8μm。在一些实施例中，所述第一区域的宽度为小于或等于5μm。“第一区域的宽度”指的是从未涂覆负极活性材料的负极集流体与涂覆负极活性材料的交界位置起至负极活性材料层的厚度达到负极活性材料层的中心区域的厚度的97％时的距离。“第一区域的宽度”也可以为负极活性材料层边缘位置起至负极活性材料层的厚度达到负极活性材料层的中心区域的厚度的97％时的距离。当第一区域的宽度在上述范围内时，负极活性材料层的削薄区较小，有助于改善电化学装置的循环性能。
在一些实施例中，所述第一区域面积小于或等于所述负极活性材料层总面积的20％。在一些实施例中，所述第一区域面积小于或等于所述负极活性材料层总面积的18％。在一些实施例中，所述第一区域面积小于或等于所述负极活性材料层总面积的15％。在一些实施例中，所述第一区域面积小于或等于所述负极活性材料层总面积的12％。在一些实施例中，所述第一区域面积小于或等于所述负极活性材料层总面积的10％。在一些实施例中，所述第一区域面积小于或等于所述负极活性材料层总面积的8％。在一些实施例中，所述第一区域面积小于或等于所述负极活性材料层总面积的5％。第一区域面积越小，对工艺要求较高，工艺成本越高。当第一区域面积占负极活性材料层总面积的比例在上述范围内时，可有效地降低负极活性材料层的削薄区带来的负面影响，且不大幅度增加额外的工艺成本，同时能改善电化学装置的循环性能。
在一些实施例中，所述负极活性材料层包括负极活性材料。在一些实施例中，所述负极活性材料为任何能够电化学性地吸留、放出锂离子等金属离子的物质。在一些 实施例中，所述负极活性材料包括碳质材料、硅碳材料、合金材料或含锂金属复合氧化物材料中的一种或多种。
在一些实施例中，所述负极活性材料的中值粒径为5μm至20μm。在一些实施例中，所述负极活性材料的中值粒径为8μm至18μm。在一些实施例中，所述负极活性材料的中值粒径为10μm至15μm。在一些实施例中，所述负极活性材料的中值粒径为5μm、8μm、10μm、12μm、15μm、18μm、20μm或在上述任意两个数值所组成的范围内。“中值粒径”指的是负极活性材料在体积基准的粒度分布中从小粒径侧起达到体积累积50％的粒径，即，小于此粒径的负极活性材料的体积占负极活性材料总体积的50％。当负极活性材料的中值粒径在上述范围内时，可进一步改善电化学装置的循环性能。
在一些实施例中，所述负极活性材料层进一步包含负极粘合剂。在一些实施例中，所述负极粘合剂包含丁苯橡胶、氟类橡胶和乙烯丙烯二烯中的一种或多种。
在一些实施例中，所述负极活性材料层进一步包含负极导电剂。在一些实施例中，所述负极导电剂包括具有导电性的金属材料和导电聚合物中的一种或多种。在一些实施例中，负极导电剂包括碳材料等的一种或多种。在一些实施例中，所述碳材料包括，但不限于，石墨、炭黑、乙炔黑和科琴黑。
在一些实施例中，所述负极的压实密度为1.3g/cm 3至1.8g/cm 3。在一些实施例中，所述负极的压实密度为1.4g/cm 3至1.6g/cm 3。在一些实施例中，所述负极的压实密度为1.5g/cm 3。
在一些实施例中，负极集流体包括负极导电材料。在一些实施例中，所述负极集流体包括，但不限于，铜、镍和不锈钢。在一些实施例中，所述负极集流体的表面的被粗糙化，粗糙化的表面能够提高负极活性材料的粘附性。在一些实施例中，粗糙化的负极集流体包括，但不限于，电解铜箔。
在一些实施例中，负极集流体的一个表面上有负极活性材料层。在一些实施例中负极集流体的两个表面上均有负极活性材料层。在一些实施例中，在负极集流体的至少一个表面上包含未设置负极活性材料层的区域，也称为空箔区域。
电解液
本申请的电化学装置中的使用的电解液包含具有P-O键的盐，基于每1cm 2所述第一区域，所述具有P-O键的盐的含量为小于或等于0.05g。
在一些实施例中，所述具有P-O键的盐为具有P-O键的无机盐。
在一些实施例中，中所述具有P-O键的盐包括LiPO 2F 2、NaPO 2F 2、KPO 2F 2、 CsPO 2F 2、二氟双草酸磷酸锂或二氟二草酸磷酸锂(LIDODFP)中的至少一种。
在一些实施例中，基于每1cm 2所述第一区域，所述具有P-O键的盐的含量为小于或等于0.04g。在一些实施例中，基于每1cm 2所述第一区域，所述具有P-O键的盐的含量为小于或等于0.03g。在一些实施例中，基于每1cm 2所述第一区域，所述具有P-O键的盐的含量为小于或等于0.02g。在一些实施例中，基于每1cm 2所述第一区域，所述具有P-O键的盐的含量为小于或等于0.01g。在一些实施例中，基于每1cm 2所述第一区域，所述具有P-O键的盐的含量为小于或等于0.005g。在一些实施例中，基于每1cm 2所述第一区域，所述具有P-O键的盐的含量为小于或等于0.001g。在一些实施例中，基于每1cm 2所述第一区域，所述具有P-O键的盐的含量为小于或等于0.0005g。
在电化学装置初始充电时，具有P-O键的盐会优先富集到负极表面，其不仅有助于负极活性材料层的第二区域的成膜，更重要的是，其还有助于负极活性材料层的第一区域的成膜并加强形成的膜的稳定性，从而可以减少负极活性材料层的第一区域中副反应的发生，降低第一区域因副产物导致的厚度变化，提高电化学装置的循环稳定性。此外，使用具有P-O键的盐有助于减少负极活性材料层的第一区域与第二区域之间的电流分布差异产生的负面影响，保证负极活性材料层的第一区域中成膜的有效性。在电解液中包含上述含量的具有P-O键的盐可降低负极活性材料层的削薄区所产生的不利影响，从而显著改善电化学装置的循环性能。
在一些实施例中，所述电解液进一步包括第一添加剂，所述第一添加剂的还原电位在2.5V以下。当第一添加剂的还原电位在2.5V以下时，其可在负极表面形成保护层，有助于降低负极活性材料层的削薄区所产生的不利影响，从而进一步显著改善电化学装置的循环性能。
在一些实施例中，所述第一添加剂包括1,3-丙磺内酯(PS)、氟代碳酸乙烯酯(FEC)、碳酸亚乙烯酯(VC)、丁二酸酐或马来酸酐中的至少一种。
在一些实施例中，所述第一添加剂包含1,3-丙磺内酯(PS)和氟代碳酸乙烯酯(FEC)。
在一些实施例中，所述1,3-丙磺内酯占所述电解液的重量百分比大于所述氟代碳酸乙烯酯占所述电解液的重量百分比。在一些实施例中，所述1,3-丙磺内酯的占所述电解液的重量百分比与所述氟代碳酸乙烯酯占所述电解液的重量百分比的比值小于或等于1.5。当重量百分比的比值在此范围内时，能够改善电化学装置的循环性能，同时 可降低电化学装置的产气量。
在一些实施例中，所述第一添加剂包括1,3-丙磺内酯(PS)、氟代碳酸乙烯酯(FEC)、和碳酸亚乙烯酯(VC)。
在一些实施例中，基于每1cm 2所述第一区域，所述第一添加剂的含量为0.001g至0.2g。在一些实施例中，基于每1cm 2所述第一区域，所述第一添加剂的含量为0.005g至0.2g。在一些实施例中，基于每1cm 2所述第一区域，所述第一添加剂的含量为0.01g至0.15g。在一些实施例中，基于每1cm 2所述第一区域，所述第一添加剂的含量为0.05g至0.13g。在一些实施例中，基于每1cm 2所述第一区域，所述第一添加剂的含量为0.08g至0.1g。在一些实施例中，基于每1cm 2所述第一区域，所述第一添加剂的含量为0.001g、0.005g、0.01g、0.03g、0.05g、0.07g、0.1g、0.15g、0.2g或在以上任意两个数值所组成的范围内。当电解液中第一添加剂的含量在上述范围内时，有助于进一步显著改善电化学装置的循环性能。
在一些实施例中，所述电解液进一步包括第二添加剂，所述第二添加剂包括四氟硼酸锂(LiBF 4)、双氟磺酰亚胺锂(LiFSI)、双三氟磺酰亚胺锂(LiTFSI)、4,5-二氰基-2-三氟甲基咪唑锂(LiTDI)、二氟草酸硼酸锂(LiDFOB)、双草酸硼酸锂、己二腈(ADN)、琥珀腈、1,3,6-己烷三腈(HTCN)、1,2,3-三(2-氰氧基)丙烷、1,4-二氰基-2-丁烯或戊二腈或三(2-氰乙基)膦中的至少一种。在一些实施例中，所述第二添加剂包括LiBF 4和LiDFOB。在一些实施例中，所述第二添加剂包括HTCN和LiDFOB。在一些实施例中，所述第二添加剂包括LiBF 4、LiDFOB和LiTFSI。在一些实施例中，所述第二添加剂包括HTCN、LiDFOB和LiTFSI。
第二添加剂可在正极表面形成保护层以减少正极处副反应的产生，还可减少正极金属离子的溶出。电化学装置循环过程中，负极保护膜的稳定性会受到正极处副反应的产物的影响。因此，第二添加剂在保护正极的同时可起到保护负极的作用，从而有助于改善电化学装置的循环性能。
在一些实施例中，基于所述电解液的重量，所述第二添加剂的含量为0.1wt％至10wt％。基于所述电解液的重量，所述第二添加剂的含量为0.2wt％至5wt％。在一些实施例中，基于所述电解液的重量，所述第二添加剂的含量为0.5wt％至3wt％。在一些实施例中，基于所述电解液的重量，所述第二添加剂的含量为1wt％至2wt％。在一些实施例中，基于所述电解液的重量，所述第二添加剂的含量为0.1wt％、0.5wt％、1wt％、2wt％、3wt％、4wt％、5wt％、6wt％、7wt％、8wt％、9wt％、10wt％或在 以上任意两个数值所组成的范围内。当电解液中第二添加剂的含量在上述范围内时，有助于进一步显著改善电化学装置的循环性能。
可用于本申请的电解液中包括LiPF 6在一些实施例中，LiPF 6的浓度在0.8mol/L至3mol/L的范围内，0.8mol/L至2.5mol/L的范围内、0.8mol/L至2mol/L的范围或1mol/L至2mol/L的范围内。在一些实施例中，锂盐的浓度为约1mol/L、约1.15mol/L、约1.2mol/L、约1.5mol/L、约2mol/L或约2.5mol/L。
可用于本申请实施例的电解液中的溶剂包括，但不限于：环状碳酸酯、链状碳酸酯、环状羧酸酯、链状羧酸酯、环状醚、链状醚、含磷有机溶剂、含硫有机溶剂和芳香族含氟溶剂。
在一些实施例中，环状碳酸酯包括，但不限于：碳酸亚乙酯(EC)、碳酸亚丙酯(PC)和碳酸亚丁酯。在一些实施例中，环状碳酸酯具有3-6个碳原子。
在一些实施例中，链状碳酸酯包括，但不限于：碳酸二甲酯、碳酸甲乙酯、碳酸二乙酯(DEC)、碳酸甲基正丙基酯、碳酸乙基正丙基酯、碳酸二正丙酯等链状碳酸酯，作为被氟取代的链状碳酸酯，例如双(氟甲基)碳酸酯、双(二氟甲基)碳酸酯、双(三氟甲基)碳酸酯、双(2-氟乙基)碳酸酯、双(2,2-二氟乙基)碳酸酯、双(2,2,2-三氟乙基)碳酸酯、2-氟乙基甲基碳酸酯、2,2-二氟乙基甲基碳酸酯和2,2,2-三氟乙基甲基碳酸酯。
在一些实施例中，环状羧酸酯包括，但不限于：γ-丁内酯和γ-戊内酯。在一些实施例中，环状羧酸酯的部分氢原子可被氟取代。
在一些实施例中，链状羧酸酯包括，但不限于：乙酸甲酯、乙酸乙酯、乙酸丙酯、乙酸异丙酯、乙酸丁酯、乙酸仲丁酯、乙酸异丁酯、乙酸叔丁酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丙酸异丙酯、丁酸甲酯、丁酸乙酯、丁酸丙酯、异丁酸甲酯、异丁酸乙酯、戊酸甲酯、戊酸乙酯、特戊酸甲酯和特戊酸乙酯。在一些实施例中，链状羧酸酯的部分氢原子可被氟取代。在一些实施例中，氟取代的链状羧酸酯包括，但不限于：三氟乙酸甲酯、三氟乙酸乙酯、三氟乙酸丙酯、三氟乙酸丁酯和三氟乙酸2,2,2-三氟乙酯。
在一些实施例中，环状醚包括，但不限于：四氢呋喃、2-甲基四氢呋喃、1,3-二氧戊环、2-甲基1,3-二氧戊环、4-甲基1,3-二氧戊环、1,3-二氧六环、1,4-二氧六环和二甲氧基丙烷。
在一些实施例中，链状醚包括，但不限于：二甲氧基甲烷、1,1-二甲氧基乙烷、1,2-二甲氧基乙烷、二乙氧基甲烷、1,1-二乙氧基乙烷、1,2-二乙氧基乙烷、乙氧基甲氧基 甲烷、1,1-乙氧基甲氧基乙烷和1,2-乙氧基甲氧基乙烷。
在一些实施例中，含磷有机溶剂包括，但不限于：磷酸三甲酯、磷酸三乙酯、磷酸二甲基乙酯、磷酸甲基二乙酯、磷酸亚乙基甲酯、磷酸亚乙基乙酯、磷酸三苯酯、亚磷酸三甲酯、亚磷酸三乙酯、亚磷酸三苯酯、磷酸三(2,2,2-三氟乙基)酯和磷酸三(2,2,3,3,3-五氟丙基)酯。
在一些实施例中，含硫有机溶剂包括，但不限于：环丁砜、2-甲基环丁砜、3-甲基环丁砜、二甲基砜、二乙基砜、乙基甲基砜、甲基丙基砜、二甲基亚砜、甲磺酸甲酯、甲磺酸乙酯、乙磺酸甲酯、乙磺酸乙酯、硫酸二甲酯、硫酸二乙酯和硫酸二丁酯。在一些实施例中，含硫有机溶剂的部分氢原子可被氟取代。
在一些实施例中，芳香族含氟溶剂包括，但不限于：氟苯、二氟苯、三氟苯、四氟苯、五氟苯、六氟苯和三氟甲基苯。
在一些实施例中，本申请的电解液中使用的溶剂包括如上所述的一种或多种。在一些实施例中，本申请的电解液中使用的溶剂包括环状碳酸酯、链状碳酸酯、环状羧酸酯、链状羧酸酯及其组合。在一些实施例中，本申请的电解液中使用的溶剂包含选自由下列物质组成的群组的有机溶剂：碳酸亚乙酯、碳酸亚丙酯、碳酸二乙酯、丙酸乙酯、丙酸丙酯、乙酸正丙酯、乙酸乙酯及其组合。在一些实施例中，本申请的电解液中使用的溶剂包含：碳酸亚乙酯、碳酸亚丙酯、碳酸二乙酯、丙酸乙酯、丙酸丙酯、γ-丁内酯或其组合。
正极
正极包括正极集流体和设置在所述正极集流体上的正极活性材料。正极活性材料的具体种类均不受到具体的限制，可根据需求进行选择。
在一些实施方案中，正极活性材料包括够吸收和释放锂(Li)的正极材料。能够吸收/释放锂(Li)的正极材料的例子可以包括钴酸锂、镍钴锰酸锂、镍钴铝酸锂、锰酸锂、磷酸锰铁锂、磷酸钒锂、磷酸钒氧锂、磷酸铁锂、钛酸锂和富锂锰基材料。
具体的，钴酸锂的化学式可以如化学式1：
Li xCo aM1 bO 2-c        化学式1
其中M1表示选自镍(Ni)、锰(Mn)、镁(Mg)、铝(Al)、硼(B)、钛(Ti)、钒(V)、铬(Cr)、铁(Fe)、铜(Cu)、锌(Zn)、钼(Mo)、锡(Sn)、钙(Ca)、锶(Sr)、钨(W)、钇(Y)、镧(La)、锆(Zr)、硅(Si)、氟(F)或硫(S)中的至少一种元素，x、a、b和c值分别在以下范围内：0.8≤x≤1.2、0.8≤a≤1、0≤b≤0.2、-0.1≤c≤0.2。
镍钴锰酸锂或镍钴铝酸锂的化学式可以如化学式2：
Li yNi dM2 eO 2-f        化学式2
其中M2表示选自钴(Co)、锰(Mn)、镁(Mg)、铝(Al)、硼(B)、钛(Ti)、钒(V)、铬(Cr)、铁(Fe)、铜(Cu)、锌(Zn)、钼(Mo)、锡(Sn)、钙(Ca)、锶(Sr)、钨(W)、锆(Zr)、硅(Si)、氟(F)或硫(S)中的至少一种元素，y、d、e和f值分别在以下范围内：0.8≤y≤1.2、0.3≤d≤0.98、0.02≤e≤0.7、-0.1≤f≤0.2。
锰酸锂的化学式可以如化学式3：
Li zMn 2-gM3 gO 4-h       化学式3
其中M3表示选自钴(Co)、镍(Ni)、镁(Mg)、铝(Al)、硼(B)、钛(Ti)、钒(V)、铬(Cr)、铁(Fe)、铜(Cu)、锌(Zn)、钼(Mo)、锡(Sn)、钙(Ca)、锶(Sr)、铌(Nb)、钽(Ta)或钨(W)中的至少一种元素，z、g和h值分别在以下范围内：0.8≤z≤1.2、0≤g<1.0和-0.2≤h≤0.2。
在一些实施例中，正极活性材料层可以在表面上具有涂层，或者可以与具有涂层的另一化合物混合。所述涂层可以包括从涂覆元素的氧化物、涂覆元素的氢氧化物、涂覆元素的羟基氧化物、涂覆元素的碳酸氧盐(oxycarbonate)和涂覆元素的羟基碳酸盐(hydroxycarbonate)中选择的至少一种涂覆元素化合物。用于涂层的化合物可以是非晶的或结晶的。在涂层中含有的涂覆元素可以包括Mg、Al、Co、K、Na、Ca、Si、Ti、V、Sn、Ge、Ga、B、As、Zr、F或它们的混合物。可以通过任何方法来施加涂层，只要所述方法不对正极活性材料的性能产生不利影响即可。例如，所述方法可以包括对本领域普通技术人员来说众所周知的任何涂覆方法，例如喷涂、浸渍等。
在一些实施方案中，正极活性材料层还包含粘合剂，并且可选地还包括正极导电材料。
粘合剂可提高正极活性材料颗粒彼此间的结合，并且还提高正极活性材料与集流体的结合。粘合剂的非限制性示例包括聚乙烯醇、羟丙基纤维素、二乙酰基纤维素、聚氯乙烯、羧化的聚氯乙烯、聚氟乙烯、聚乙烯吡咯烷酮、聚氨酯、聚四氟乙烯、聚偏1,1-二氟乙烯、聚乙烯、聚丙烯、丁苯橡胶、丙烯酸(酯)化的丁苯橡胶、环氧树脂、尼龙等。
正极活性材料层包括正极导电材料，从而赋予电极导电性。所述正极导电材料可以包括任何导电材料，只要它不引起化学变化。正极导电材料的非限制性示例包括基于碳的材料(例如，天然石墨、人造石墨、碳黑、乙炔黑、科琴黑、碳纤维等)、基于 金属的材料(例如，金属粉、金属纤维等，包括例如铜、镍、铝、银等)、导电聚合物(例如，聚亚苯基衍生物)和它们的混合物。
用于根据本申请的电化学装置的正极集流体可以是铝(Al)，但不限于此。
隔离膜
在一些实施例中，本申请的电化学装置在正极与负极之间设有隔离膜，以防止两个极片接触导致的电流短路，同时可使锂离子通过。
本申请的电化学装置中使用的隔离膜的材料和形状没有特别限制，其可为任何现有技术中公开的技术。在一些实施例中，隔离膜包括由对本申请的电解液稳定的材料形成的聚合物(例如，合成树脂)或无机物(例如，陶瓷)等。在一些实施例中，隔离膜包括由所述聚合物或所述无机物制成的多孔膜。在一些实施例中，隔离膜包括层压两种以上多孔膜的层压膜。在一些实施例中，所述聚合物包括，但不限于，聚四氟乙烯、聚丙烯和聚乙烯。
在一些实施例中，所述隔离膜包括上述多孔膜(基底材料层)和设置在所述基底材料层的一个或两个表面上的高分子化合物层，其可提高隔离膜相对于正极和负极的粘附性，抑制卷绕电极极片时产生偏斜，由此抑制电解液的分解反应并抑制浸渍基底材料层的电解液的液体泄漏。通过使用此种隔离膜，即使在重复充电/放电的情况下，电化学装置的电阻不会显著增加，从而抑制了电化学装置的膨胀。
在一些实施例中，所述高分子化合物层包含，但不限于，聚偏二氟乙烯。聚偏二氟乙烯具有优异的物理强度和电化学稳定性。所述高分子化合物层可通过以下方法形成：在制备溶解有高分子材料的溶液之后，用所述溶液对基底材料层进行涂布或将基底材料层浸泡在溶液中，最后进行干燥。
应用
本申请的电化学装置包括发生电化学反应的任何装置，它的具体实例包括所有种类的一次电池或二次电池。特别地，该电化学装置是锂二次电池，包括锂金属二次电池、锂离子二次电池、锂聚合物二次电池或锂离子聚合物二次电池。
本申请的电化学装置的用途没有特别限定，其可用于现有技术中已知的任何用途。在一个实施例中，本申请的电化学装置可用于，但不限于，笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、 电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
实施例
以下说明根据本申请的锂离子电池的实施例和对比例进行性能评估。
1、锂离子电池的制备
对比例1：
(1)负极的制备
将负极活性材料人造石墨(中值粒径12.0μm)、导电剂Super P、羧甲基纤维素钠(CMC)、粘结剂丁苯橡胶(SBR)按照重量比96.4:1.5:0.5:1.6混合，加入去离子水，搅拌均匀，得到负极浆料，其中负极浆料的固含量为54wt％。将负极浆料均匀涂覆在铜箔上，在85℃下烘干，然后经过冷压、模切、分切、卷绕后，在120℃的真空条件下干燥12小时，得到长度为1544.0±5.0mm、宽度为66.5±1.0mm的负极，单面负极活性材料层的总面积(以单面计)为1544.0×66.5＝102676(mm 2)，约1027cm 2，负极的压实密度为1.6g/cm 3。
根据以下对比例和实施例的设置，通过调节负极浆料的粘度、使用不同规格的涂布模头、控制涂布模头到涂辊的距离、基材走带的速度等方式调节和控制负极活性材料层的第一区域的宽度和面积。
表1中各对比例和实施例中的第一区域的面积对应的第一区域的宽度如下表所示：
第一区域的面积(cm 2) 第一区域的宽度(mm)
5 0.3
15 1.0
40 2.6
54 3.5
70 4.5
93 6.0
124 8.0
185 12.0
232 15.0
(2)正极的制备
将正极活性材料Li(Ni 0.8Co 0.08Mn 0.07)Al 0.05O 2、导电剂Super-P和聚偏二氟乙烯按照97:1.4:1.6的质量比例与N-甲基吡咯烷酮(NMP)混合，搅拌均匀，得到正极浆料，其中正极浆料的固含量为72wt％。将该正极浆料涂布在铝箔上，在85℃下烘干，然后经过冷压、模切、分切、焊接极耳后，在85℃的真空条件下干燥4小时，得到正极。
(3)电解液的制备
在干燥氩气环境下，将碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按照质量比为EC:PC:DEC:EMC＝15:25:50:10进行混合，根据实施例和对比例的设置加入添加剂，溶解并充分搅拌后加入锂盐LiPF 6，混合均匀，得到基础电解液，其中，LiPF 6的浓度为1.2mol/L。
根据以下对比例和实施例的设置，在基础电解液中添加具有P-O键的盐、第一添加剂和/或第二添加剂，得到电解液。
(4)隔离膜的制备
选用厚度为7μm的聚乙烯(PE)膜，在其上涂覆PVDF浆液和无机颗粒(片状勃姆石和Al 2O 3的质量比为70:30)浆液，烘干，涂层厚度为3μm，得到隔离膜。
(5)锂离子电池的制备
将得到的正极、隔离膜和负极按次序卷绕形成裸电芯，将裸电芯置于外包装箔中，留下注液口。从注液口灌注电解液，封装，再经过化成(以0.02C恒流充电到3.3V，再以0.1C恒流充电到3.6V)、容量等工序制得锂离子电池(厚度为约9.1mm、宽度为约49mm、长度为约74mm)。
2、测试方法
(1)锂离子电池的循环容量保持率和循环厚度膨胀率的测试方法
将锂离子电池置于25℃恒温箱中，静置30分钟，使锂离子电池达到恒温。测试锂离子电池的初始厚度H0。将达到恒温的锂离子电池以1.0C恒流充电至电压为4.2V，然后以4.2V恒压充电至电流为0.05C，接着以4C恒流放电至电压为2.8V，此为一个充放电循环，记录首次放电的容量C0。采用相同步骤使锂离子电池充放电循环600次，停止测试。记录循环后的放电容量C1以及锂离子电池的厚度H1。
通过下式计算锂离子电池的循环容量保持率和循环厚度膨胀率：
循环容量保持率＝C1/C0×100％；
循环厚度膨胀率＝(H1-H0)/H0×100％。
(2)负极活性材料层的第一区域和第二区域的厚度的测试方法
当负极活性材料层具有如图2所示的结构时，以长度中轴线为截面，以宽度方向为中心选取长度为1cm的截面，通过数码显微系统(VHX-950F)测试负极活性材料层的厚度，任选10个点，计算负极片总厚度的平均值E 0和集流体厚度平均值E 1，通过下式计算负极活性材料层的第二区域的厚度D2：D2＝(E 0-E 1)/2。
以长度中轴线为截面，从负极活性材料层边缘区开始间隔0.1mm测试一个点，测任意单面的负极活性材料层远离集流体的表面到该负极活性材料层接触的集流体表面的厚度即为D1，连续测试5个点的厚度，当其中3个点都满足D1＞D2×97％时，以此时靠近负极活性材料层边缘最近的点到负极活性材料层边缘的距离作为负极活性材料层第一区域的宽度。以上厚度测试单位精确到0.01mm。测试过程中，截面的选择需要包括负极活性材料层的第一区域和第二区域。
当负极活性材料层具有如图3所示的结构时，采用与上述基本相同的方法，以宽度中轴线为截面进行测试。
当负极活性材料层具有如图4所示的结构时，采用与上述基本相同的方法，分别以长度中轴线和宽度中轴线为截面进行测试。
(3)电解液中具有P-O键的盐的含量的测试方法
将锂离子电池以0.2C的倍率放电至电压为2.8V，称取锂离子电池的重量记为M 0，剪去极耳和外包装，得到裸电芯，通过离心裸电芯得到电解液，然后通过离子色谱IC(型号：赛默飞，AQUION)测试电解液中的阴离子含量，得到电解液中具有P-O键的盐的相对含量Q。然后将离心后的裸电芯用碳酸二甲酯(DMC)浸泡72小时后烘干，称量烘干后的裸电芯、极耳和外包装的总质量，记为M 1。通过下式计算裸电芯中具有P-O键的盐的质量：(M 0-M 1)×Q。将具有P-O键的盐的质量除以负极活性材料层的第一区域总面积，即可得到单位面积的第一区域对应的具有P-O键的盐的质量。
第一添加剂和第二添加剂的类型采用离子色谱IC(型号：赛默飞，AQUION)或气相色谱仪GC(型号：Agilent 7890A-5975C)进行测试。
3、测试结果
表1展示了各对比例和实施例中的电解液组分以及负极活性材料层中的第一区域对锂离子电池的循环性能的影响。具有P-O键的盐或第一添加剂的单位面积含量指的是每1cm 2所述第一区域的具有P-O键的盐或第一添加剂的重量。在表1所示各实施例和对比例中，单面负极活性材料层的总面积为1027cm 2。
表1
Figure PCTCN2021084482-appb-000001
Figure PCTCN2021084482-appb-000002
Figure PCTCN2021084482-appb-000003
如对比例1至9所示，减小负极活性材料层的第一区域的面积虽然能够提高锂离子电池的循环容量保持率并降低其厚度膨胀率，但锂离子电池的循环容量保持率较低，厚度膨胀率较高，难以满足使用需求。
如实施例1至13所示，当电解液包含小于或等于0.05g/cm 2的具有P-O键的盐时，可显著提高锂离子电池的循环容量保持率，并显著降低其厚度膨胀率。如实施例34至37所示，不用类型的具有P-O键的盐或其组合可实现基本相当的效果。
如实施例14至20所示，当电解液进一步包含0.001-0.2g/cm 2的第一添加剂时，可进一步提高锂离子电池的循环容量保持率，并降低其厚度膨胀率。
如实施例21至27所示，当电解液进一步包含0.1wt％至10wt％的第二添加剂时，可进一步提高锂离子电池的循环容量保持率，并降低其厚度膨胀率。如实施例28至33所示，当组合使用多种第一添加剂和/或第二添加剂时，可进一步提高锂离子电池的循环容量保持率，并降低其厚度膨胀率。
此外，当第一区域面积小于或等于负极活性材料层总面积的20％时，可进一步提高锂离子电池的循环容量保持率，并降低其厚度膨胀率。
表2展示了负极活性材料的中值粒径对锂离子电池的循环性能的影响。实施例38-41与实施例3制备方法基本相同，不同之处仅在于表2所示参数。
表2
Figure PCTCN2021084482-appb-000004
Figure PCTCN2021084482-appb-000005
如表2所示，当负极活性材料层中负极活性材料的中值粒径为5μm至20μm时，可进一步提高锂离子电池的循环容量保持率，并降低其厚度膨胀率。
整个说明书中对“一些实施例”、“部分实施例”、“一个实施例”、“另一举例”、“举例”、“具体举例”或“部分举例”的引用，其所代表的意思是在本申请中的至少一个实施例或举例包含了该实施例或举例中所描述的特定特征、结构、材料或特性。因此，在整个说明书中的各处所出现的描述，例如：“在一些实施例中”、“在实施例中”、“在一个实施例中”、“在另一个举例中”，“在一个举例中”、“在特定举例中”或“举例”，其不必然是引用本申请中的相同的实施例或示例。此外，本文中的特定特征、结构、材料或特性可以以任何合适的方式在一个或多个实施例或举例中结合。
尽管已经演示和描述了说明性实施例，本领域技术人员应该理解上述实施例不能被解释为对本申请的限制，并且可以在不脱离本申请的精神、原理及范围的情况下对实施例进行改变，替代和修改。

Claims (10)

  1. 一种电化学装置，其包括负极和电解液，其中：
    所述负极包括负极集流体和设置于所述负极集流体的至少一个表面的负极活性材料层，所述负极活性材料层包括第一区域和第二区域，所述第一区域的任意位置的厚度D1小于所述第二区域的平均厚度D2，并且
    所述电解液包含具有P-O键的盐，基于每1cm 2所述第一区域，所述具有P-O键的盐的含量为小于或等于0.05g。
  2. 根据权利要求1所述的电化学装置，其中D1和D2满足：D1≤D2×97％。
  3. 根据权利要求1所述的电化学装置，其中所述具有P-O键的盐包括LiPO 2F 2、NaPO 2F 2、KPO 2F 2、CsPO 2F 2、二氟双草酸磷酸锂或四氟草酸磷酸锂中的至少一种。
  4. 根据权利要求1所述的电化学装置，其中所述电解液进一步包括第一添加剂，所述第一添加剂包括1,3-丙磺内酯、氟代碳酸乙烯酯、碳酸亚乙烯酯、丁二酸酐或马来酸酐中的至少一种。
  5. 根据权利要求4所述的电化学装置，其中基于每1cm 2所述第一区域，所述第一添加剂的含量为0.001g至0.2g。
  6. 根据权利要求1所述的电化学装置，其中所述电解液进一步包括第二添加剂，所述第二添加剂包括四氟硼酸锂、双(氟磺酰)亚胺锂、双(三氟甲基磺酰)亚胺锂、4,5-二氰基-2-三氟甲基咪唑锂、二氟草酸硼酸锂、双草酸硼酸锂、己二腈、琥珀腈、1,3,6-己烷三腈、1,2,3-三(2-氰氧基)丙烷、1,4-二氰基-2-丁烯或戊二腈或三(2-氰乙基)膦中的至少一种，基于所述电解液的重量，所述第二添加剂的含量为0.1wt％至10wt％。
  7. 根据权利要求1所述的电化学装置，其中所述第一区域位于所述负极活性材料层的边缘，所述第一区域的宽度为小于或等于15mm。
  8. 根据权利要求1所述的电化学装置，其中所述第一区域面积小于或等于所述负 极活性材料层总面积的20％。
  9. 根据权利要求1-8中任一项所述的电化学装置，其中所述负极活性材料层包括负极活性材料，所述负极活性材料的中值粒径为5μm至20μm。
  10. 一种电子装置，其包括根据权利要求1-9中任一权利要求所述的电化学装置。
PCT/CN2021/084482 2021-03-31 2021-03-31 电化学装置及包含其的电子装置 WO2022205099A1 (zh)

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