WO2023050359A1 - 电化学装置和包含其的电子装置 - Google Patents

电化学装置和包含其的电子装置 Download PDF

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WO2023050359A1
WO2023050359A1 PCT/CN2021/122314 CN2021122314W WO2023050359A1 WO 2023050359 A1 WO2023050359 A1 WO 2023050359A1 CN 2021122314 W CN2021122314 W CN 2021122314W WO 2023050359 A1 WO2023050359 A1 WO 2023050359A1
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active material
positive electrode
electrode active
lithium
electrochemical device
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French (fr)
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王可飞
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology Ltd
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Priority to PCT/CN2021/122314 priority Critical patent/WO2023050359A1/zh
Priority to EP21958931.4A priority patent/EP4394905A4/en
Priority to CN202411646563.8A priority patent/CN119447162A/zh
Priority to CN202180012340.4A priority patent/CN115039255B/zh
Publication of WO2023050359A1 publication Critical patent/WO2023050359A1/zh
Priority to US18/618,167 priority patent/US20240274819A1/en
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    • H—ELECTRICITY
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    • 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
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/60—Selection of substances as active materials, active masses, active liquids of organic compounds
    • H01M4/602—Polymers
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
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    • 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
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    • 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
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    • 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
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • H—ELECTRICITY
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
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    • 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
    • H—ELECTRICITY
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    • 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
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    • 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
    • H01M4/623—Binders being polymers fluorinated polymers
    • H—ELECTRICITY
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    • 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
    • H01M2004/028—Positive 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, in particular to an electrochemical device and an electronic device containing it, especially a lithium ion battery.
  • the embodiments of the present application provide an electrochemical device and an electronic device that can fully suppress the increase of DC internal resistance under high voltage and high temperature, and effectively improve the floating charge performance under high voltage, to solve the problems existing in the prior art to some extent.
  • the problem is not limited to:
  • the present application provides an electrochemical device, the electrochemical device includes a positive electrode, a negative electrode and an electrolyte, the positive electrode includes a positive electrode current collector and a positive electrode active material layer on the positive electrode current collector,
  • the positive electrode active material layer includes a positive electrode active material, wherein based on the mass of the positive electrode active material layer, the mass percentage of the positive electrode active material is M%, and the value range of M is 95 to 99, and the positive electrode active material layer
  • the surface crack width is Wmm, where M and W satisfy: M/W ⁇ 47.5.
  • W 2.
  • the mass per unit area of the positive electrode active material layer is M 1 mg/1540.25mm 2 , and the value of M 1 ranges from 100 to 400, wherein M 1 and W satisfy: M 1 /W ⁇ 50.
  • the solid content of the positive electrode active material layer coating slurry is M 2 %, and the value of M 2 ranges from 55 to 80, wherein M 2 and W satisfy: M 2 /W ⁇ 27.5.
  • the positive electrode includes a fluorine-based binder with a melting point in the range of 155°C to 270°C.
  • the positive electrode active material layer includes a polymer compound with ether bonds, wherein based on the mass of the positive electrode active material layer, the mass percentage of the polymer compound with ether bonds is M 4 %, M 4 ⁇ 0.3.
  • the oxidation potential of the polymer compound having ether bonds is greater than or equal to 4.6V.
  • the electrolyte solution includes additive A, and the additive A includes at least one of a compound having a cyano group or a compound having an F-P-O bond.
  • the mass percentage of the additive A is a%, and the value of a ranges from 0.1 to 15.
  • M/a 6.33.
  • the compound having a cyano group includes at least one of the following compounds: succinonitrile, glutaronitrile, adiponitrile, 1,5-dicyanopentane, 1,6-dicyano Hexyl hexane, tetramethylsuccinonitrile, 2-methylglutaronitrile, 2,4-dimethylglutaronitrile, 2,2,4,4-tetramethylglutaronitrile, 1,4-di Cyanopentane, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, ethylene glycol bis(propionitrile) ether, 3,5-dioxa- Pimelonitrile, 1,4-bis(cyanoethoxy)butane, diethylene glycol bis(2-cyanoethyl)ether, triethylene glycol bis(2-cyanoethyl)ether, tetra Ethylene glycol bis(2-cyanoethyl)
  • the compound having an F-P-O bond includes at least one of lithium difluorophosphate, a compound of formula 1, a compound of formula 2, a compound of formula 3 or a compound of formula 4:
  • the positive electrode active material satisfies one of the following conditions:
  • the positive active material includes lithium iron phosphate, and the D50 of the positive active material is D 1 ⁇ m, where 2 ⁇ D 1 ⁇ W;
  • the positive active material includes lithium manganese iron phosphate, and the D50 of the positive active material is D 2 ⁇ m, where 5 ⁇ D 2 ⁇ W;
  • the positive active material includes lithium manganate, and the D50 of the positive active material is D 3 ⁇ m, where 0.1 ⁇ D 3 ⁇ W;
  • the positive electrode active material includes lithium nickel cobalt manganese oxide, and the D50 of the positive electrode active material is D 4 ⁇ m, where 0.15 ⁇ D 4 ⁇ W;
  • the positive electrode active material includes lithium cobaltate, and the D50 of the positive electrode active material is D 5 ⁇ m, where 0.15 ⁇ D 5 ⁇ W.
  • the smoothness of the surface of the positive electrode sheet can be further adjusted, thereby improving the performance of the lithium-ion battery.
  • the electrolyte solution further includes additive B, which includes fluoroethylene carbonate, 1,3-propane sultone, vinyl sulfate, ethylene carbonate or phosphoric acid cyclic anhydride. at least one of .
  • the present application provides an electronic device, which includes the electrochemical device according to the embodiment of the present application.
  • the electrochemical device provided by the present application has reduced DC internal resistance and improved capacity retention, low temperature performance and float charge performance.
  • FIG. 1 shows SEM pictures of the surface of the positive electrode active material layer in Examples 1-8 of the present application.
  • a list of items linked by the terms “one of”, “one of”, “one of” or other similar terms may mean that any of the listed items one.
  • the phrase “one of A and B” means only A or only B.
  • the phrase “one of A, B, and C” means only A; only B; or only 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.
  • a list of items linked by the terms “at least one of”, “at least one of”, “at least one of” or other similar terms may mean that the listed items any combination of .
  • the phrase “at least one of A and B” means only A; only B; or A and B.
  • the phrase “at least one of A, B, and C” means only A; or only B; only C; 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.
  • the present application provides an electrochemical device, and the electrochemical device includes a positive electrode, a negative electrode, and an electrolyte.
  • the positive electrode includes a positive electrode current collector and a positive electrode active material layer on the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material.
  • the positive active material layer may be one or more layers.
  • each layer of the multilayer positive active material may contain the same or different positive active material.
  • the positive electrode active material is any material capable of reversibly intercalating and deintercalating metal ions such as lithium ions.
  • the discharge capacity of the positive active material is smaller than the chargeable capacity of the negative active material to prevent unintentional deposition of lithium metal on the negative electrode during charging.
  • the mass percentage of the positive active material is M%, and the value of M ranges from 95 to 99.
  • M is 95, 96, 97, 98, 99, or a range consisting of any two of these values.
  • the crack width on the surface of the positive electrode active material layer is W mm, W ⁇ 2.
  • W is 0.01, 0.02, 0.03, 0.05, 0.08, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.4, 1.5, 1.8, 2 or these values The range consisting of any two of them.
  • M and W satisfy: M/W ⁇ 47.5.
  • M/W is 47.5, 50, 60, 80, 90, 100, 120, 150, 200, 300, 400, 500, 100, 1500, 1800, 2000, 5000, 8000, 9000, 10000, A range of 15000, 18000, 20000, or any two of these values.
  • the positive electrode satisfies the above relationship, not only the interfacial stability of the positive active material layer can be improved, but also the DC internal resistance growth of the electrochemical device at room temperature and high temperature can be fully suppressed, and the floating charge performance at high voltage can be improved unexpectedly .
  • the crack width on the surface of the positive electrode active material layer can reflect the surface properties of the positive electrode active material layer, which is one of the parameters characterizing the positive electrode active material layer.
  • the smaller the crack width the better the flatness of the interface of the positive electrode active material layer, which can significantly improve the cycle performance, rate performance, floating charge performance of the electrochemical device and reduce the DC internal resistance of the electrochemical device.
  • the crack width of the positive active material layer can be affected by many factors, mainly including the coating weight of the positive active material layer, the compaction density of the positive active material layer, the solid content of the coating slurry of the positive active material layer, the particle size of the positive active material, The content of the positive electrode active material, the binder of the positive electrode active material layer, the auxiliary agent of the positive electrode active material layer, the functional treatment layer on the surface of the positive electrode active material layer, and the porosity of the positive electrode active material layer, etc.
  • Cracking in the present application refers to cracks generated on the surface of the positive electrode active material layer due to the influence of internal stress, external impact, or environmental conditions.
  • the crack width on the surface of the positive electrode active material layer in the present application refers to the largest crack width among all the cracks, which can be measured by a ruler or other measuring instruments.
  • the mass per unit area of the positive electrode active material layer is M 1 mg/1540.25 mm 2 , and the value of M 1 ranges from 100 to 400.
  • M is 100, 120, 140, 150, 160, 180, 200, 240, 250, 270, 280, 290, 300, 350, 380, 400, or a range consisting of any two of these values .
  • the positive electrode surface can maintain structural stability during charge-discharge cycles, which further improves the performance of lithium-ion batteries.
  • the active layer If the value of M1 exceeds 400, the active layer is too thick, the permeability of the electrolyte is reduced, and the electron transport in the battery will be difficult, causing the polarization of the battery to increase, thereby deteriorating the high current density charge and discharge characteristics.
  • the value of M 1 is lower than 100, the active layer will have a greater impact on the current collector during processing, destroying the current collector interface, and at the same time, the relative displacement between the active materials will also increase, affecting performance.
  • M 1 and W satisfy: M 1 /W ⁇ 50. In some embodiments, M 1 and W satisfy: M 1 /W is 50, 80, 100, 150, 200, 250, 300, 350, 400, 500 or a range consisting of any two of these values. When the positive electrode satisfies the above relationship, further improved effects can be obtained.
  • the solid content of the positive electrode active material layer coating slurry is M 2 %, and the value of M 2 ranges from 55 to 80.
  • M2 is a range of 55, 58, 60, 63, 65, 68, 70, 72, 75, 78, 80, or a combination of any two of these values.
  • the value of M2 ranges from 55 to 80, the surface defects of the positive electrode are less, which further improves the performance of the lithium-ion battery. If it exceeds this range, the pole pieces will crack severely during baking. In addition, if it is lower than this range, the solvent will be wasted in the process of preparing the positive electrode active material layer, and the baking time will be prolonged, thereby causing a loss in the process.
  • M 2 and W satisfy: M 2 /W ⁇ 27.5.
  • M2 /W is 27.5, 30, 32, 35, 38, 40, 45, 50, 60, 70, 80, 90, 100, 120, 200, 300, 350, 370, 400, 500 , 600, 700, 800, 1000, 1100, 1400, 1500, 3000, 5000, 7000, 9000, 10000, 16000, 20000 or any two of these values.
  • the positive electrode satisfies the above relationship, further improved effects can be obtained.
  • the positive electrode includes a fluorine-based binder with a melting point in the range of 155°C to 270°C.
  • the melting point of the fluorine-based binder is 155°C, 160°C, 165°C, 170°C, 172°C, 175°C, 180°C, 200°C, 220°C, 220°C, 230°C, 240°C °C, 250 °C, 260 °C, 270 °C or any combination of these values.
  • the fluorine-based binder includes polyvinylidene fluoride.
  • the polyvinylidene fluoride includes a homopolymer of vinylidene fluoride as a monomer and a copolymer of vinylidene fluoride (VdF) as a monomer.
  • VdF vinylidene fluoride
  • the ends of the polyvinylidene fluoride may be modified with maleic acid.
  • the mass percentage of the fluorine-based binder is 0.5% to 3%. In some embodiments, based on the mass of the positive electrode active material layer, the mass percentage of the fluorine-based binder is 0.5%, 0.8%, 1.0%, 1.5%, 1.8%, 2.0%, 2.2%, 2.5% , 2.8%, 3%, or a range consisting of any two of these values.
  • the content of the fluorine-based binder is less than 0.5%, the coverage of the positive electrode active material particles by the fluorine-based binder becomes insufficient, the binding property decreases, and the cracking phenomenon is aggravated.
  • the content of the fluorine-based binder exceeds 3%, the positive electrode active material particles are excessively covered by the fluorine-based binder, resulting in an increase in DC resistance, and high discharge rate performance cannot be obtained in a low-temperature environment, and the high-discharge rate performance cannot be obtained in a high-temperature environment. Good float performance cannot be obtained.
  • the positive active material layer includes additives.
  • the auxiliary agent includes a polymer compound having an ether bond, wherein based on the mass of the positive electrode active material layer, the mass percentage of the polymer compound having an ether bond is M 4 %, M 4 ⁇ 0.3.
  • M4 is 0.04, 0.05, 0.06, 0.07, 0.08, 0.1, 0.12, 0.14, 0.15, 0.18, 0.2, 0.25, 0.28, 0.3, or a range consisting of any two of these values.
  • the content of the auxiliary agent is within the above range, it is helpful to improve the following characteristics of the electrochemical device: output power characteristics, load characteristics, low temperature characteristics, cycle characteristics and high temperature storage characteristics.
  • the oxidation potential of the polymer compound having ether bonds is greater than or equal to 4.6V. In some embodiments, the oxidation potential of the polymer compound having ether bonds is 4.6V, 4.7V, 4.8V, 4.9V, 5.0V, 5.1V, 5.2V, 5.3V, 5.4V, 5.5V, 5.6 V, 6V, or a range consisting of any two of these values.
  • the oxidation potential of the auxiliary agent is within the above range, the electrochemical performance of the electrochemical device is stable and high-pressure resistant, which helps to improve the floating charge performance of the electrochemical device under high temperature and high pressure.
  • the polymer compound having ether linkages includes at least one of polyethylene oxide, polyether, polyalcohol or polyalcohol ester.
  • the type of the positive electrode active material is not particularly limited, as long as it can absorb and release metal ions (eg, lithium ions) electrochemically.
  • the positive active material is a material containing lithium and at least one transition metal. Examples of positive active materials may include, but are not limited to, lithium transition metal composite oxides and lithium transition metal phosphate compounds.
  • the transition metals in the lithium transition metal composite oxide include V, Ti, Cr, Mn, Fe, Co, Ni, Cu, and the like.
  • lithium transition metal composite oxides include lithium cobalt composite oxides such as LiCoO 2 , lithium nickel composite oxides such as LiNiO 2 , lithium manganese composite oxides such as LiMnO 2 , LiMn 2 O 4 , Li 2 MnO 4 , lithium nickel manganese cobalt composite oxides such as LiNi 1/3 Mn 1/3 Co 1/3 O 2 , LiNi 0.5 Mn 0.3 Co 0.2 O 2 , etc., in which a part of the transition metal atom which is the main body of these lithium transition metal composite oxides is Na, K, B, F, Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, W and other elements substituted .
  • lithium transition metal composite oxides may include, but are not limited to, LiNi 0.5 Mn 0.5 O 2 , LiNi 0.85 Co 0.10 Al 0.05 O 2 , LiNi 0.33 Co 0.33 Mn 0.33 O 2 , LiNi 0.45 Co 0.10 Al 0.45 O 2 , LiMn 1.8 Al 0.2 O 4 and LiMn 1.5 Ni 0.5 O 4 etc.
  • combinations of lithium transition metal composite oxides include, but are not limited to, combinations of LiCoO 2 and LiMn 2 O 4 , wherein a part of Mn in LiMn 2 O 4 may be replaced by transition metals (for example, LiNi 0.33 Co 0.33 Mn 0.33 O 2 ), part of Co in LiCoO 2 can be replaced by transition metals.
  • the transition metals in the lithium-containing transition metal phosphate compound include V, Ti, Cr, Mn, Fe, Co, Ni, Cu, and the like.
  • lithium-containing transition metal phosphate compounds include iron phosphates such as LiFePO 4 , Li 3 Fe 2 (PO 4 ) 3 , LiFeP 2 O 7 , and cobalt phosphates such as LiCoPO 4 , wherein as these lithium transition metal phosphate compounds Some of the transition metal atoms of the main body are replaced by other elements such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si, etc.
  • lithium phosphate is included in the positive active material, which can improve the continuous charging characteristics of the electrochemical device.
  • the use of lithium phosphate is not limited.
  • the positive electrode active material and lithium phosphate are used in combination.
  • the mass percentage of lithium phosphate is greater than 0.1%, greater than 0.3% or greater than 0.5% relative to the mass of the aforementioned positive electrode active material and lithium phosphate.
  • the mass percentage of lithium phosphate is less than 10%, less than 8% or less than 5%.
  • the content of lithium phosphate is within the range formed by any two values above.
  • a substance having a different composition may adhere to the surface of the positive electrode active material.
  • surface attachment substances may include, but are not limited to: oxides such as alumina, silica, titania, zirconia, magnesia, calcium oxide, boron oxide, antimony oxide, bismuth oxide; lithium sulfate, sodium sulfate, potassium sulfate , magnesium sulfate, calcium sulfate, aluminum sulfate and other sulfates; lithium carbonate, calcium carbonate, magnesium carbonate and other carbonates; carbon, etc.
  • These surface attachment substances can be attached to the surface of the positive electrode active material by the following methods: dissolving or suspending the surface attachment substances in a solvent and infiltrating into the positive electrode active material and drying them; dissolving or suspending the surface attachment substance precursors In a solvent, after infiltrating and adding to the positive electrode active material, the method of making it react by heating or the like; and the method of firing while adding to the positive electrode active material precursor, etc.
  • attaching carbon a method of mechanically attaching a carbon material (for example, activated carbon, etc.) can also be used.
  • the content of the surface attachment substance is greater than 0.1 ppm, greater than 1 ppm or greater than 10 ppm. In some embodiments, based on the mass of the positive electrode active material layer, the content of the surface attachment substance is less than 10%, less than 5% or less than 2%. In some embodiments, based on the mass of the positive electrode active material layer, the content of the surface attachment substance is within the range formed by any two values above.
  • the oxidation reaction of the electrolyte solution on the surface of the positive electrode active material can be suppressed, and the life of the electrochemical device can be improved.
  • the amount of the surface-attached substance is too small, the effect cannot be fully expressed; when the amount of the surface-attached substance is too large, it will hinder the entry and exit of lithium ions, so the resistance may increase.
  • a positive electrode active material having a composition different from the positive electrode active material attached to the surface of the positive electrode active material is also referred to as a "positive electrode active material”.
  • the shape of the positive electrode active material particles includes, but is not limited to, block shape, polyhedron shape, spherical shape, ellipsoidal shape, plate shape, needle shape, columnar shape, and the like.
  • the positive active material particles include primary particles, secondary particles, or a combination thereof.
  • primary particles may agglomerate to form secondary particles.
  • the tap density of the positive active material is greater than 0.5 g/cm 3 , greater than 0.8 g/cm 3 or greater than 1.0 g/cm 3 .
  • the tap density of the positive electrode active material is within the above range, the required amount of dispersion medium and conductive material and positive electrode binder can be suppressed when the positive electrode active material layer is formed, thereby ensuring the filling of the positive electrode active material rate and capacity of the electrochemical device.
  • a composite oxide powder having a high tap density a high-density positive electrode active material layer can be formed. The larger the tap density is generally, the more preferable it is, and there is no particular upper limit.
  • the tap density of the positive active material is less than 4.0 g/cm 3 , less than 3.7 g/cm 3 or less than 3.5 g/cm 3 .
  • the tap density of the positive electrode active material has the upper limit as described above, a decrease in load characteristics can be suppressed.
  • the tap density of the positive active material can be calculated in the following way: put 5g to 10g of positive active material powder into a 10mL glass measuring cylinder, and vibrate 200 times with a stroke of 20mm to obtain the powder packing density (tap density ).
  • the median diameter (D50) of the positive electrode active material particles refers to the primary particle diameter of the positive electrode active material particles.
  • the median diameter (D50) of the positive electrode active material particles refers to the secondary particle diameter of the positive electrode active material particles.
  • the median diameter (D50) of the positive electrode active material particles is greater than 0.3 ⁇ m, greater than 0.5 ⁇ m, greater than 0.8 ⁇ m or greater than 1.0 ⁇ m. In some embodiments, the median diameter (D50) of the positive electrode active material particles is less than 30 ⁇ m, less than 27 ⁇ m, less than 25 ⁇ m or less than 22 ⁇ m. In some embodiments, the median diameter (D50) of the positive electrode active material particles is within the range formed by any two values above. When the median diameter (D50) of the positive electrode active material particles is within the above-mentioned range, a positive electrode active material with a high tap density can be obtained, and a decrease in the performance of the electrochemical device can be suppressed.
  • the positive electrode active material particle median diameter (D50) can be measured by a laser diffraction/scattering particle size distribution analyzer: in the case of using LA-920 manufactured by HORIBA Corporation as a particle size distribution meter, use 0.1% sodium hexametaphosphate aqueous solution as The dispersion medium used in the measurement was measured after 5 minutes of ultrasonic dispersion with the refractive index set to 1.24.
  • the positive electrode active material satisfies one of the following conditions:
  • the positive active material includes lithium iron phosphate, and the D50 of the positive active material is D 1 ⁇ m, where 2 ⁇ D 1 ⁇ W;
  • the positive active material includes lithium manganese iron phosphate, and the D50 of the positive active material is D 2 ⁇ m, where 5 ⁇ D 2 ⁇ W;
  • the positive active material includes lithium manganate, and the D50 of the positive active material is D 3 ⁇ m, where 0.1 ⁇ D 3 ⁇ W;
  • the positive electrode active material includes lithium nickel cobalt manganese oxide, and the D50 of the positive electrode active material is D 4 ⁇ m, where 0.15 ⁇ D 4 ⁇ W;
  • the positive electrode active material includes lithium cobaltate, and the D50 of the positive electrode active material is D 5 ⁇ m, where 0.15 ⁇ D 5 ⁇ W.
  • the above-mentioned positive electrode active materials such as lithium iron phosphate, lithium manganese iron phosphate, lithium manganate, lithium nickel cobalt manganese oxide, and lithium cobalt oxide can be used alone or in any combination.
  • the flatness of the surface of the positive pole piece and the compaction density of the pole piece can be further adjusted, thereby improving the performance of the lithium-ion battery.
  • the positive active material layer further includes a conductive agent.
  • the conductive agent includes at least one of carbon nanotubes, carbon fibers, acetylene black, graphene, Ketjen black, or carbon black.
  • the positive electrode current collector includes at least one of copper foil or aluminum foil.
  • the positive electrode can be prepared by a preparation method known in the art.
  • the positive electrode may be obtained by mixing a positive electrode active material, a conductive agent, and a binder in a solvent to prepare an active material composition, and coating the active material composition on a current collector.
  • the solvent may include N-methylpyrrolidone and the like, but is not limited thereto.
  • the electrolytic solution used in the electrochemical device of the present application includes an electrolyte and a solvent for dissolving the electrolyte.
  • the electrolyte solution includes additive A, and the additive A includes at least one of a compound having a cyano group or a compound having an F-P-O bond.
  • the mass percentage of the additive A is a%, and the value of a ranges from 0.1 to 15. In some embodiments, a is 0.1, 0.4, 0.5, 0.8, 1, 1.5, 1.8, 2, 2.5, 3, 3.5, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or a range of any two of these values.
  • M/a is 6.33, 8, 10, 15, 20, 24, 28, 30, 32, 35, 40, 45, 50, 100, 150, 190, 200, 250, or any of these values range of both.
  • the compound having a cyano group includes at least one of the following compounds: succinonitrile, glutaronitrile, adiponitrile, 1,5-dicyanopentane, 1,6-dicyano Hexyl hexane, tetramethylsuccinonitrile, 2-methylglutaronitrile, 2,4-dimethylglutaronitrile, 2,2,4,4-tetramethylglutaronitrile, 1,4-di Cyanopentane, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, ethylene glycol bis(propionitrile) ether, 3,5-dioxa- Pimelonitrile, 1,4-bis(cyanoethoxy)butane, diethylene glycol bis(2-cyanoethyl)ether, triethylene glycol bis(2-cyanoethyl)ether, tetra Ethylene glycol bis(2-cyanoethyl)
  • the compound having an F-P-O bond includes at least one of lithium difluorophosphate, a compound of formula 1, a compound of formula 2, a compound of formula 3 or a compound of formula 4:
  • the electrolyte also includes additive B, which includes fluoroethylene carbonate, 1,3-propane sultone, vinyl sulfate, ethylene carbonate, and phosphoric acid cyclic anhydride. at least one of .
  • the electrolyte solution further comprises any non-aqueous solvent known in the prior art as a solvent for the electrolyte solution.
  • the non-aqueous solvent includes, but is not limited to, one or more of the following: cyclic carbonate, chain carbonate, cyclic carboxylate, chain carboxylate, cyclic Ethers, chain ethers, phosphorus-containing organic solvents, sulfur-containing organic solvents, and aromatic fluorinated solvents.
  • examples of the cyclic carbonate may include, but are not limited to, one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate.
  • the cyclic carbonate has 3-6 carbon atoms.
  • examples of the chain carbonate may include, but are not limited to, one or more of the following: dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate (DEC), methyl carbonate Chain carbonates such as ethyl n-propyl carbonate, ethyl n-propyl carbonate, di-n-propyl carbonate, etc.
  • chain carbonates substituted with fluorine may include, but are not limited to, one or more of the following: bis(fluoromethyl)carbonate, bis(difluoromethyl)carbonate, bis(trifluoromethyl)carbonate base) carbonate, bis(2-fluoroethyl)carbonate, bis(2,2-difluoroethyl)carbonate, bis(2,2,2-trifluoroethyl)carbonate, 2-fluoroethyl methyl carbonate, 2,2-difluoroethyl methyl carbonate and 2,2,2-trifluoroethyl methyl carbonate, etc.
  • examples of the cyclic carboxylate may include, but are not limited to, one or more of the following: one or more of ⁇ -butyrolactone and ⁇ -valerolactone.
  • some of the hydrogen atoms of the cyclic carboxylate may be replaced by fluorine.
  • examples of the chain carboxylate may include, but are not limited to, one or more of the following: methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate ester, sec-butyl acetate, isobutyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, methyl butyrate, ethyl butyrate, butyric acid Propyl ester, methyl isobutyrate, ethyl isobutyrate, methyl valerate, ethyl valerate, methyl pivalate and ethyl pivalate, etc.
  • part of the hydrogen atoms of the chain carboxylate may be substituted by fluorine.
  • examples of fluorine-substituted chain carboxylic acid esters may include, but are not limited to, methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, and trifluoroacetic acid 2,2,2-trifluoroethyl ester, etc.
  • examples of the cyclic ether may include, but are not limited to, one or more of the following: tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 2-methyl 1,3-dioxolane, 4-methyl 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane and dimethoxypropane.
  • examples of the chain ethers may include, but are not limited to, one or more of the following: dimethoxymethane, 1,1-dimethoxyethane, 1,2- Dimethoxyethane, diethoxymethane, 1,1-diethoxyethane, 1,2-diethoxyethane, ethoxymethoxymethane, 1,1-ethoxy Methoxyethane and 1,2-ethoxymethoxyethane, etc.
  • examples of the phosphorus-containing organic solvent may include, but are not limited to, one or more of the following: trimethyl phosphate, triethyl phosphate, dimethyl ethyl phosphate, methyl phosphate Diethyl ester, ethylene methyl phosphate, ethylene ethyl phosphate, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, triphenyl phosphite, tris(2,2,2- phosphate Trifluoroethyl) ester and tris(2,2,3,3,3-pentafluoropropyl) phosphate, etc.
  • examples of the sulfur-containing organic solvent may include, but are not limited to, one or more of the following: sulfolane, 2-methylsulfolane, 3-methylsulfolane, dimethylsulfone, disulfone Ethyl sulfone, ethyl methyl sulfone, methyl propyl sulfone, dimethyl sulfoxide, methyl methanesulfonate, ethyl methanesulfonate, methyl ethanesulfonate, ethyl ethanesulfonate, dimethyl sulfate , diethyl sulfate and dibutyl sulfate.
  • some hydrogen atoms of the sulfur-containing organic solvent may be replaced by fluorine.
  • the aromatic fluorinated solvent includes, but is not limited to, one or more of the following: fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene and trifluoromethylbenzene.
  • the solvent used in the electrolyte of the present application includes cyclic carbonates, chain carbonates, cyclic carboxylates, chain carboxylates, 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, propyl propionate , n-propyl acetate, ethyl acetate, and combinations thereof.
  • the solvent used in the electrolyte of the present application includes: ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, ⁇ -butyrolactone and combinations thereof.
  • the electrolyte is not particularly limited, and any known substance as an electrolyte can be used arbitrarily.
  • lithium salts are generally used.
  • electrolytes may include, but are not limited to, inorganic lithium salts such as LiPF 6 , LiBF 4 , LiClO 4 , LiAlF 4 , LiSbF 6 , LiWF 7 ; lithium tungstates such as LiWOF 5 ; HCO 2 Li, CH 3 CO 2 Li, CH 2 FCO 2 Li, CHF 2 CO 2 Li, CF 3 CO 2 Li, CF 3 CH 2 CO 2 Li, CF 3 CF 2 CO 2 Li, CF 3 CF 2 CO 2 Li, CF 3 CF 2 CF 2 CO 2 Li, CF 3 CF 2 CF 2 Lithium carboxylate salts such as CF 2 CO 2 Li; FSO 3 Li, CH 3 SO 3 Li, CH 2 FSO 3 Li, CHF 2 SO 3 Li, CF 3 SO 3 Li, CF 3 CF 2 SO 3 Li, CF 3
  • the electrolyte is selected from LiPF 6 , LiSbF 6 , FSO 3 Li, CF 3 SO 3 Li, LiN(FSO 2 ) 2 , LiN(FSO 2 )(CF 3 SO 2 ), LiN(CF 3 SO 2 ) 2 , LiN(C 2 F 5 SO 2 ) 2 , cyclic lithium 1,2-perfluoroethanebissulfonimide, cyclic lithium 1,3-perfluoropropanebissulfonimide, LiC(FSO 2 ) 3 , LiC(CF 3 SO 2 ) 3 , LiC(C 2 F 5 SO 2 ) 3 , LiBF 3 CF 3 , LiBF 3 C 2 F 5 , LiPF 3 (CF 3 ) 3 , LiPF 3 (C 2 F 5 ) 3.
  • Lithium difluorooxalate borate, lithium bis(oxalate)borate or lithium difluorobis(oxalato)phosphate which help to improve the output power characteristics, high-rate charge-discharge characteristics, and high-temperature storage characteristics of electrochemical devices and cycle characteristics, etc.
  • the content of the electrolyte is not particularly limited as long as the effect of the present application is not impaired.
  • the total molar concentration of lithium in the electrolyte is greater than 0.3 mol/L, greater than 0.4 mol/L or greater than 0.5 mol/L.
  • the total molar concentration of lithium in the electrolyte is less than 3 mol/L, less than 2.5 mol/L or less than 2.0 mol/L.
  • the total molar concentration of lithium in the electrolyte is within the range formed by any two values above. When the electrolyte concentration is within the above range, the lithium as charged particles will not be too small, and the viscosity can be kept in an appropriate range, so it is easy to ensure good electrical conductivity.
  • the electrolyte includes at least one salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate.
  • the electrolyte includes a salt selected from the group consisting of monofluorophosphate, oxalate, and fluorosulfonate.
  • the electrolyte includes a lithium salt.
  • the content of the salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate is greater than 0.01% or greater than 0.1%, based on the mass of the electrolyte.
  • the content of the salt selected from the group consisting of monofluorophosphate, borate, oxalate and fluorosulfonate is less than 20% or less than 10% based on the mass of the electrolyte. In some embodiments, the content of the salt selected from the group consisting of monofluorophosphate, borate, oxalate and fluorosulfonate is within the range formed by any two of the above values.
  • the electrolyte comprises one or more species selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate and one or more other salts.
  • the lithium salts exemplified above, in some examples, LiPF 6 , LiN(FSO 2 )(CF 3 SO 2 ), LiN(CF 3 SO 2 ) 2 , LiN(C 2 F 5 SO 2 ) 2 , cyclic lithium 1,2-perfluoroethanebissulfonimide, cyclic lithium 1,3-perfluoropropanebissulfonylimide, LiC(FSO 2 ) 3 , LiC(CF 3 SO 2 ) 3 , LiC(C 2 F 5 SO 2 ) 3 , LiBF 3 CF 3 , LiBF 3 C 2 F 5 , LiPF 3 (CF 3 ) 3 , LiPF 3 (C 2 F 5 ) 3 .
  • the additional salt is
  • the content of other salts is greater than 0.01% or greater than 0.1% based on the mass of the electrolyte. In some embodiments, the content of other salts is less than 20%, less than 15%, or less than 10%, based on the mass of the electrolyte. In some embodiments, the content of other salts is within the range formed by any two values above. Other salts having the above content help to balance the conductivity and viscosity of the electrolyte.
  • the negative electrode includes a negative electrode current collector and a negative electrode active material layer on one or both surfaces of the negative electrode current collector.
  • the negative electrode active material layer includes a negative electrode active material.
  • the negative electrode active material layer may be one or more layers, and each layer of the multilayer negative electrode active material may contain the same or different negative electrode active materials.
  • the negative electrode active material is any material capable of reversibly intercalating and deintercalating metal ions such as lithium ions.
  • the chargeable capacity of the negative active material is greater than the discharge capacity of the negative active material, so as to prevent unintentional precipitation of lithium metal on the negative electrode during charging.
  • any known current collector can be used arbitrarily.
  • negative electrode current collectors include, but are not limited to, metal materials such as aluminum, copper, nickel, stainless steel, and nickel-plated steel. In some embodiments, the negative current collector is copper.
  • the form of the negative electrode current collector may include, but not limited to, metal foil, metal cylinder, metal strip, metal plate, metal film, expanded metal, stamped metal, foamed metal, etc.
  • the negative electrode current collector is a metal film.
  • the negative electrode current collector is copper foil.
  • the negative electrode current collector is a rolled copper foil based on a rolling method or an electrolytic copper foil based on an electrolytic method.
  • the thickness of the negative electrode current collector is greater than 1 ⁇ m or greater than 5 ⁇ m. In some embodiments, the thickness of the negative electrode current collector is less than 100 ⁇ m or less than 50 ⁇ m. In some embodiments, the thickness of the negative electrode current collector is within the range formed by any two values above.
  • the negative electrode active material is not particularly limited as long as it can reversibly store and release lithium ions.
  • Examples of negative electrode active materials may include, but are not limited to, carbon materials such as natural graphite and artificial graphite; metals such as silicon (Si) and tin (Sn); or oxides of metal elements such as Si and Sn.
  • the negative electrode active materials can be used alone or in combination.
  • the negative active material layer may further include a negative binder.
  • the negative electrode binder can improve the combination of the negative electrode active material particles and the combination of the negative electrode active material and the current collector.
  • the type of negative electrode binder is not particularly limited, as long as it is a material stable to the electrolyte solution or the solvent used in electrode production.
  • the negative binder includes a resin binder. Examples of resin binders include, but are not limited to, fluororesins, polyacrylonitrile (PAN), polyimide resins, acrylic resins, polyolefin resins, and the like.
  • the negative electrode binder When using a water-based solvent to prepare the negative electrode mixture slurry, the negative electrode binder includes, but is not limited to, carboxymethyl cellulose (CMC) or its salt, styrene-butadiene rubber (SBR), polyacrylic acid (PAA) or Its salt, polyvinyl alcohol, etc.
  • CMC carboxymethyl cellulose
  • SBR styrene-butadiene rubber
  • PAA polyacrylic acid
  • Its salt polyvinyl alcohol, etc.
  • the negative electrode can be prepared by the following method: coating the negative electrode mixture slurry containing the negative electrode active material, resin binder, etc. on the negative electrode current collector, after drying, performing calendering to form the negative electrode on both sides of the negative electrode current collector active material layer, and thus a negative electrode can be obtained.
  • a separator is usually provided between the positive electrode and the negative electrode.
  • the electrolytic solution of the present application is usually used by permeating the separator.
  • the material and shape of the separator are not particularly limited as long as the effect of the present application is not significantly impaired.
  • the separator can be resin, glass fiber, inorganic material, etc. formed of materials stable to the electrolyte solution of the present application.
  • the separator includes a porous sheet or a non-woven fabric-like substance with excellent liquid retention properties.
  • the material of the resin or fiberglass separator may include, but are not limited to, polyolefin, aramid, polytetrafluoroethylene, polyethersulfone, and the like.
  • the polyolefin is polyethylene or polypropylene.
  • the polyolefin is polypropylene.
  • the materials for the above separators may be used alone or in any combination.
  • the isolation film can also be a material formed by laminating the above materials, examples of which include, but not limited to, a three-layer isolation film formed by laminating polypropylene, polyethylene, and polypropylene in this order.
  • Examples of materials of inorganic substances may include, but are not limited to, oxides such as aluminum oxide and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, sulfates (eg, barium sulfate, calcium sulfate, etc.).
  • Inorganic forms may include, but are not limited to, granular or fibrous.
  • the form of the separator may be in the form of a film, examples of which include, but are not limited to, non-woven fabrics, woven fabrics, microporous films, and the like.
  • the pore diameter of the isolation membrane is 0.01 ⁇ m to 1 ⁇ m, and the thickness is 5 ⁇ m to 50 ⁇ m.
  • the following separator can also be used: a separator formed by forming a composite porous layer containing the above-mentioned inorganic particles on the surface of the positive electrode and/or negative electrode using a resin-based binder,
  • a separator is formed by using fluororesin as a binder to form porous layers on both sides of the positive electrode with 90% of the alumina particles having a particle size of less than 1 ⁇ m.
  • the thickness of the separator is arbitrary. In some embodiments, the thickness of the isolation film is greater than 1 ⁇ m, greater than 5 ⁇ m, or greater than 8 ⁇ m. In some embodiments, the thickness of the isolation film is less than 50 ⁇ m, less than 40 ⁇ m or less than 30 ⁇ m. In some embodiments, the thickness of the isolation film is within the range formed by any two values above. When the thickness of the separator is within the above range, insulation and mechanical strength can be ensured, and rate characteristics and energy density of the electrochemical device can be ensured.
  • the porosity of the separator is arbitrary.
  • the isolation membrane has a porosity greater than 10%, greater than 15%, or greater than 20%.
  • the separator has a porosity of less than 60%, less than 50%, or less than 45%.
  • the porosity of the isolation membrane is within the range formed by any two values above. When the porosity of the separator is within the above range, insulation and mechanical strength can be ensured, and membrane resistance can be suppressed, so that the electrochemical device has good safety characteristics.
  • the average pore diameter of the separator is also arbitrary. In some embodiments, the average pore size of the isolation membrane is less than 0.5 ⁇ m or less than 0.2 ⁇ m. In some embodiments, the average pore size of the isolation membrane is greater than 0.05 ⁇ m. In some embodiments, the average pore diameter of the isolation membrane is within the range formed by any two values above. When the average pore diameter of the separator exceeds the above-mentioned range, short circuits are likely to occur. When the average pore diameter of the isolation membrane is within the above range, the electrochemical device has good safety characteristics.
  • an electrochemical device includes an electrode group, a current collection structure, an outer casing, and a protective element.
  • the electrode group may have either a laminated structure in which the positive electrode and the negative electrode are laminated with the separator interposed therebetween, or a structure in which the positive electrode and the negative electrode are wound in a spiral shape with the separator interposed therebetween.
  • the ratio of the mass of the electrode group to the internal volume of the battery is greater than 40% or greater than 50%.
  • the electrode set occupancy is less than 90% or less than 80%.
  • the occupancy of the electrode group is within the range formed by any two values above. When the electrode group occupancy ratio is within the above range, the capacity of the electrochemical device can be ensured, and at the same time, the decrease in characteristics such as repeated charge-discharge performance and high-temperature storage due to an increase in internal pressure can be suppressed.
  • the current collecting structure is not particularly limited. In some embodiments, the current collecting structure is a structure that reduces the resistance of the wiring portion and the bonding portion.
  • the electrode group has the above-mentioned laminated structure, it is suitable to use a structure in which the metal core portions of the electrode layers are bundled and welded to the terminal.
  • the internal resistance increases, so it is also suitable to provide two or more terminals in the electrode to reduce the resistance.
  • the electrode group has the above-mentioned winding structure, the internal resistance can be reduced by providing two or more lead wire structures on the positive electrode and the negative electrode respectively, and bundling them on the terminals.
  • the material of the outer case is not particularly limited, as long as it is stable to the electrolyte solution used.
  • metals such as nickel-plated steel sheets, stainless steel, aluminum or aluminum alloys, and magnesium alloys, or laminated films of resin and aluminum foil can be used, but not limited to.
  • the outer casing is aluminum or aluminum alloy metal or a laminated film.
  • Metal exterior cases include, but are not limited to, encapsulation and sealing structures formed by welding metals together by laser welding, resistance welding, or ultrasonic welding; or riveted structures using the above-mentioned metals through resin spacers.
  • the exterior case using the above-mentioned laminated film includes, but is not limited to, a package sealing structure formed by thermally bonding resin layers to each other, and the like. In order to improve the sealability, a resin different from the resin used in the laminated film may be interposed between the above-mentioned resin layers.
  • a resin having a polar group or a modified resin into which a polar group is introduced can be used as the interposed resin due to the bonding between the metal and the resin.
  • the shape of the exterior body is also arbitrary, and for example, any of cylindrical, square, laminated, button-shaped, large, and the like may be used.
  • Protection elements can use positive temperature coefficient (PTC) whose resistance increases when abnormal heat generation or excessive current flows, temperature fuses, thermistors, cut off by causing the internal pressure of the battery or the internal temperature to rise sharply at the time of abnormal heat generation A valve (current cut-off valve) for the current flowing in the circuit, etc.
  • PTC positive temperature coefficient
  • the above-mentioned protection element can be selected under the condition that it does not work in the normal use of high current, and it can also be designed in such a way that abnormal heat dissipation or thermal runaway will not occur even if there is no protection element.
  • the electrochemical device of the present application includes any device that undergoes an electrochemical reaction, and its specific examples include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors.
  • the electrochemical device is a lithium secondary battery, including a lithium metal secondary battery or a lithium ion secondary battery.
  • the present application further provides an electronic device, which includes the electrochemical device according to the present application.
  • the application of the electrochemical device of the present application is not particularly limited, and it can be used in any electronic device known in the prior art.
  • the electrochemical device of the present application can be used in, but not limited to, notebook computers, pen-based computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-worn Stereo headphones, VCRs, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic organizers, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, automobiles, motorcycles, power assist Bicycles, bicycles, lighting equipment, toys, game consoles, clocks, electric tools, flashlights, cameras, large household storage batteries and lithium-ion capacitors, etc.
  • the lithium ion battery is taken as an example below and the preparation of the lithium ion battery is described in conjunction with specific examples. Those skilled in the art will understand that the preparation method described in this application is only an example, and any other suitable preparation methods are described in this application. within range.
  • the positive electrode active material such as lithium cobaltate
  • Super-P and polyvinylidene fluoride are mixed with N-methylpyrrolidone ( NMP) were mixed and stirred evenly to obtain positive electrode slurry.
  • NMP N-methylpyrrolidone
  • the positive electrode slurry was coated on a 12 ⁇ m aluminum foil, dried, cold pressed, cut into pieces, and tabs were welded to obtain a positive electrode.
  • a polyethylene porous membrane with alumina coating was used as the separator, with a thickness of 9 ⁇ m.
  • the electrolyte solution is poured from the liquid injection port, packaged, and then the lithium-ion battery is produced through processes such as formation and capacity.
  • the lithium-ion battery was charged to 4.7V with a constant current of 1C, then charged at a constant voltage to a current of 0.05C, and then discharged to 3.0V with a constant current of 1C, which was the first cycle.
  • the lithium ion battery was subjected to 800 cycles under the above conditions.
  • the capacity retention rate after cycling is calculated according to the following formula:
  • Capacity retention (discharge capacity after 800 cycles/discharge capacity at first cycle) ⁇ 100%.
  • Discharge percentage [-20°C discharge capacity/25°C discharge capacity] ⁇ 100%.
  • VHX-5000 software uses the VHX-5000 software to measure the width of the widest part of the crack by using the parallel line method (select two adjacent widest points to form a straight line), measure each crack 5 times, and take the maximum value as the crack width, that is, W mm.
  • the melting point of the fluorine-based binder can be measured by the following operations: first, take out the positive electrode from the battery, wash it with dimethyl carbonate, make it dry, remove the current collector, and place it in a suitable dispersion medium (such as N-methylpyrrolidone, etc.) Heat and stir in the medium to dissolve the binder in the dispersion medium. Thereafter, the positive electrode active material is removed by centrifugation, and the supernatant is filtered, then evaporated to dryness or reprecipitated in water, whereby the binder can be taken out.
  • a suitable dispersion medium such as N-methylpyrrolidone, etc.
  • DSC differential scanning calorimeter
  • the content of the fluorine-based binder was measured by first taking out the positive electrode from the battery, washing it with dimethyl carbonate, and drying it. Next, using a differential thermobalance device (TG-DTA such as Rigaku Thermo plus TG8120 manufactured by Rigaku Corporation), heat a sample of several mg to tens of mg at a heating rate of 1 to 5°C/min in an air atmosphere until it reaches 600°C , the content of the fluorine-based binder in the positive electrode active material layer was obtained from the amount of mass loss at this time.
  • TG-DTA such as Rigaku Thermo plus TG8120 manufactured by Rigaku Corporation
  • Table 1 shows the mass percentage (M%) of the positive active material in the positive active material layer and the crack width (Wmm) on the surface of the positive active material layer to the high temperature and high pressure DC internal resistance and the high temperature and high pressure floating charge performance of the lithium-ion battery Impact.
  • the cathode material in Table 1 is Hunan Shanshan lithium cobaltate LC9000E; the electrolyte is the basic electrolyte.
  • the difference between Examples 1-2 to 1-13 and Comparative Examples 1-1 to 1-3 and Example 1-1 lies in the parameters listed in Table 1, and other parameters are the same.
  • the ionic conductance and electronic conductance of the surface and interior of the positive electrode can be improved, so lower DC internal resistance can be obtained, and the performance of the electrochemical device is better.
  • the crack width of the pole piece is large, such as exceeding 2 mm, it will have a serious impact on the ion conductance and electron conductance, and deteriorate the performance of the battery.
  • defects on the surface of the positive electrode such as cracks, pits, craters, pinholes, etc. can be reduced, and the continuous destruction of the passivation layer on the surface of the positive electrode can be effectively suppressed during the charge and discharge cycle of the battery.
  • FIG. 1 shows SEM pictures of the surface of the positive electrode active material layer in Examples 1-8 of the present application. The picture shows that the surface of the positive electrode active material layer has a crack width of 0.3 mm.
  • Table 2 shows the effect of the mass per unit area (M 1 mg/1540.25mm 2 ) of the positive electrode active material layer and the crack width (Wmm) on the surface of the positive electrode active material layer on the high temperature and high pressure DC internal resistance and high temperature and high pressure floating of lithium-ion batteries. impact on chargeability.
  • M 1 mg/1540.25mm 2 mass per unit area
  • Wmm crack width
  • table 3 has shown the solid content (M 2 %) of positive electrode active material layer coating slurry and the crack width (Wmm) of positive electrode active material layer surface to the DC internal resistance under high temperature and high pressure of lithium-ion battery and floating charge under high temperature and high pressure performance impact.
  • the difference between Examples 3-1 to 3-15 and Example 1-1 lies in the parameters listed in Table 3.
  • Table 4-1 shows the influence of the melting point of the positive electrode binder on the DC internal resistance under high temperature and high pressure and the floating charge performance under high temperature and high pressure of lithium-ion batteries. The difference between Examples 4-1 to 4-12 and Example 1-1 lies in the parameters listed in Table 4-1.
  • the fluorine-based binder with a melting point in the range of 155°C to 270°C when used, the DC internal resistance of the lithium-ion battery is further reduced and the floating charge performance of the lithium-ion battery is improved.
  • the reason may be that when using a fluorine-based binder with a melting point in the range of 155°C to 270°C, the binder can be evenly distributed on the surface of the positive electrode material particles during the baking or hot pressing process of the electrode sheet preparation process, effectively improving the adhesion effect , to suppress the surface defects of the pole piece, and further improve the performance of the lithium-ion battery.
  • Table 4-2 shows the impact of the type and mass percentage (M 4 %) of the positive electrode additive on the DC internal resistance under high temperature and high pressure and the floating charge performance under high temperature and high pressure of the lithium ion battery.
  • the preparation method of the positive electrode in Examples 4-13 to 4-21 is as follows: lithium cobaltate (Hunan Shanshan LC9000E), Super-P and polyvinylidene fluoride are mixed with N- Mix methylpyrrolidone, then add the additives in Table 4-2 to the slurry, and stir evenly to obtain positive electrode slurry.
  • the positive electrode slurry was coated on a 12 ⁇ m aluminum foil, dried, cold pressed, cut into pieces, and tabs were welded to obtain a positive electrode.
  • Table 5 shows the impact of the type and particle size (D50) of the positive electrode active material and the crack width on the surface of the positive electrode active material layer on the DC internal resistance and floating charge performance under high temperature and high pressure of the lithium-ion battery. The only difference between Examples 5-1 to 5-6 and Example 1-1 lies in the parameters listed in Table 5.
  • the positive active material includes lithium iron phosphate, and the D50 of the positive active material is D 1 ⁇ m, where 2 ⁇ D 1 ⁇ W;
  • the positive active material includes lithium manganese iron phosphate, and the D50 of the positive active material is D 2 ⁇ m, where 5 ⁇ D 2 ⁇ W;
  • the positive active material includes lithium manganate, and the D50 of the positive active material is D 3 ⁇ m, where 0.1 ⁇ D 3 ⁇ W;
  • the positive electrode active material includes lithium nickel cobalt manganese oxide, and the D50 of the positive electrode active material is D 4 ⁇ m, where 0.15 ⁇ D 4 ⁇ W;
  • the positive electrode active material includes lithium cobaltate, and the D50 of the positive electrode active material is D 5 ⁇ m, where 0.15 ⁇ D 5 ⁇ W.
  • the reason may be that by selecting an appropriate particle size, the flatness of the surface of the positive electrode sheet can be further adjusted, thereby improving the performance of the lithium-ion battery.
  • Table 6 shows the impact of the type or content of the electrolyte additive and the mass percentage (M%) of the positive electrode active material on the DC internal resistance and the floating charge performance under high temperature and high pressure of the lithium-ion battery, wherein based on the total of the electrolyte Mass, the mass percent of the additive is a%.
  • M% mass percentage
  • additives and M/a in an appropriate range, it is possible to make up for the deterioration of the surface of the pole sheet due to uneven SOC during the cycle of the battery.
  • the additives form a stable protective film on the surface of the positive electrode, especially for defects. The repair of the part is more important.
  • the consistency of the surface of the pole piece is well maintained during the cycle, so it not only further improves the DC internal resistance under high temperature and high pressure and the floating charge performance under high temperature and high pressure, but also means Unexpectedly, the capacity retention at high voltage and the rate performance at low temperature are simultaneously improved, which may be due to the good stability and low impedance of the formed interface between the cathode and electrolyte at high voltage and low temperature, It can make lithium ions easier to deintercalate.
  • the electrolyte when the electrolyte also includes at least one of fluoroethylene carbonate, 1,3-propane sultone, vinyl sulfate, ethylene ethylene carbonate, and phosphoric acid cyclic anhydride, it can further improve the performance under high temperature and high pressure. DC internal resistance and float charge performance under high temperature and high pressure.
  • references to “some embodiments”, “partial embodiments”, “one embodiment”, “another example”, “example”, “specific example” or “partial example” in the entire specification mean that At least one embodiment or example in this application includes a specific feature, structure, material or characteristic described in the embodiment or example.
  • descriptions that appear throughout the specification such as: “in some embodiments”, “in an embodiment”, “in one embodiment”, “in another example”, “in an example In”, “in a particular example” or “example”, they are not necessarily referring to the same embodiment or example in this application.
  • the particular features, structures, materials, or characteristics herein may be combined in any suitable manner in one or more embodiments or examples.

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Abstract

本申请涉及电化学装置和包含其的电子装置。本申请的电化学装置包括：正极、负极和电解液，所述正极包括正极集流体和位于所述正极集流体上的正极活性物质层，所述正极活性物质层包括正极活性物质，其中基于所述正极活性物质层的质量，所述正极活性物质的质量百分比为M％，M的取值范围为95至99，所述正极活性物质层表面的开裂宽度为W mm，其中M和W满足：M/W≥47.5。本申请提供的电化学装置具有降低的直流内阻以及改善的容量保持率、低温性能和浮充性能。

Description

电化学装置和包含其的电子装置 技术领域
本申请涉及储能领域，具体涉及一种电化学装置和包含其的电子装置，特别是锂离子电池。
背景技术
近年来，随着电池产业化规模的不断扩张及相关技术的发展，锂离子电池的能量密度受到越来越多的关注和挑战。在不断改善和提升能量密度的工作中，目前最为有效的方案是提高正极涂布重量，降低非活性材料的使用量。然而涂布重量增加后，由于应力增加，会出现严重的涂层开裂问题，影响了电池的一致性和电化学性能。
虽然现有技术中通过降低涂布速度，降低烘箱温度，从而降低极片烘干速度，可以防止极片中的溶剂过快挥发导致应力过大而导致极片涂层开裂，但是这种方式抑制了工业化生产、增加了制造成本，很难实现量产。
发明内容
本申请实施例通过提供一种能够充分抑制高压高温下的直流内阻增长，而且有效提高高电压下的浮充性能的电化学装置和电子装置，以在某种程度上解决存在于现有技术的问题。
在一个实施例中，本申请提供了一种电化学装置，所述电化学装置包括正极、负极和电解液，所述正极包括正极集流体和位于所述正极集流体上的正极活性物质层，所述正极活性物质层包括正极活性物质，其中基于所述正极活性物质层的质量，所述正极活性物质的质量百分比为M％，M的取值范围为95至99，所述正极活性物质层表面的开裂宽度为Wmm，其中M和W满足：M/W≥47.5。
在一些实施例中，W≤2。
在一些实施例中，所述正极活性物质层的单位面积质量为M 1mg/1540.25mm 2，M 1的取值范围为100至400，其中M 1和W满足：M 1/W≥50。
在一些实施例中，所述正极活性物质层涂布浆料的固含量为M 2％，M 2的取值范围 为55至80，其中M 2和W满足：M 2/W≥27.5。
在一些实施例中，所述正极包括熔点在155℃至270℃范围内的氟系粘结剂。
在一些实施例中，所述正极活性物质层包括具有醚键的高分子化合物，其中基于所述正极活性物质层的质量，所述具有醚键的高分子化合物的质量百分比为M 4％，M 4≤0.3。
在一些实施例中，所述具有醚键的高分子化合物的氧化电位大于或等于4.6V。
在一些实施例中，所述电解液包括添加剂A，所述添加剂A包括具有氰基的化合物或具有F-P-O键的化合物中的至少一种。
在一些实施例中，所述添加剂A的质量百分比为a％，a的取值范围为0.1至15。
在一些实施例中，M/a≥6.33。
在一些实施例中，所述具有氰基的化合物包括以下化合物中的至少一种：丁二腈、戊二腈、己二腈、1,5-二氰基戊烷、1,6-二氰基己烷、四甲基丁二腈、2-甲基戊二腈、2,4-二甲基戊二腈、2,2,4,4-四甲基戊二腈、1,4-二氰基戊烷、1,2-二氰基苯、1,3-二氰基苯、1,4-二氰基苯、乙二醇双(丙腈)醚、3,5-二氧杂-庚二腈、1,4-二(氰基乙氧基)丁烷、二乙二醇二(2-氰基乙基)醚、三乙二醇二(2-氰基乙基)醚、四乙二醇二(2-氰基乙基)醚、1,3-二(2-氰基乙氧基)丙烷、1,4-二(2-氰基乙氧基)丁烷、1,5-二(2-氰基乙氧基)戊烷、乙二醇二(4-氰基丁基)醚、1,4-二氰基-2-丁烯、1,4-二氰基-2-甲基-2-丁烯、1,4-二氰基-2-乙基-2-丁烯、1,4-二氰基-2,3-二甲基-2-丁烯、1,4-二氰基-2,3-二乙基-2-丁烯、1,6-二氰基-3-己烯、1,6-二氰基-2-甲基-3-己烯、1,3,5-戊三甲腈、1,2,3-丙三甲腈、1,3,6-己三甲腈、1,2,6-己三甲腈、1,2,3-三(2-氰基乙氧基)丙烷、1,2,4-三(2-氰基乙氧基)丁烷、1,1,1-三(氰基乙氧基亚甲基)乙烷、1,1,1-三(氰基乙氧基亚甲基)丙烷、3-甲基-1,3,5-三(氰基乙氧基)戊烷、1,2,7-三(氰基乙氧基)庚烷、1,2,6-三(氰基乙氧基)己烷或1,2,5-三(氰基乙氧基)戊烷。
在一些实施例中，所述具有F-P-O键的化合物包括二氟磷酸锂、式1化合物、式2化合物、式3化合物或式4化合物中的至少一种：
Figure PCTCN2021122314-appb-000001
Figure PCTCN2021122314-appb-000002
在一些实施例中，所述正极活性物质满足如下条件中的一者：
(1)所述正极活性物质包括磷酸铁锂，所述正极活性物质的D50为D 1μm，其中2×D 1≥W；
(2)所述正极活性物质包括磷酸锰铁锂，所述正极活性物质的D50为D 2μm，其中5×D 2≥W；
(3)所述正极活性物质包括锰酸锂，所述正极活性物质的D50为D 3μm，其中0.1×D 3≥W；
(4)所述正极活性物质包括镍钴锰酸锂，所述正极活性物质的D50为D 4μm，其中0.15×D 4≥W；和
(5)所述正极活性物质包括钴酸锂，所述正极活性物质的D50为D 5μm，其中0.15×D 5≥W。
本申请通过选择合适的粒径，可以进一步调节正极极片表面的平整度，从而提高锂离子电池的性能。
在一些实施例中，所述电解液进一步包括添加剂B，所述添加剂B包括氟代碳酸乙烯酯、1,3-丙磺酸内酯、硫酸乙烯酯、碳酸乙烯亚乙酯或磷酸环酐中的至少一种。
在另一个实施例中，本申请提供一种电子装置，其包括根据本申请的实施例所述的电化学装置。
本申请提供的电化学装置具有降低的直流内阻以及改善的容量保持率、低温性能和浮充性能。
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和显示，或是经由本申请实施例的实施而阐释。
附图说明
图1示出了本申请实施例1-8中正极活性物质层表面的SEM图片。
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。本申请的实施例不应该被解释为对本申请的限制。
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“中的一者”、“中的一个”、“中的一种”或其他相似术语所连接的项目的列表可意味着所列项目中的任一者。例如，如果列出项目A及B，那么短语“A及B中的一者”意味着仅A或仅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中的一者”意味着仅A；仅B；或仅C。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。
在具体实施方式及权利要求书中，由术语“中的至少一者”、“中的至少一个”、“中的至少一种”或其他相似术语所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中的至少一者”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中的至少一者”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。
一、电化学装置
在一些实施例中，本申请提供了一种电化学装置，所述电化学装置包括正极、负极和电解液。
正极
1、正极活性物质层
在一些实施例中，所述正极包括正极集流体和位于所述正极集流体上的正极活性物质层，所述正极活性物质层包括正极活性物质。在一些实施例中，所述正极活性物质层可以是一层或多层。在一些实施例中，多层正极活性物质中的每层可以包含相同或不同的正极活性物质。正极活性物质为任何能够可逆地嵌入和脱嵌锂离子等金属离子的物质。在一些实施例中，正极活性物质的放电容量小于负极活性物质的可充电容量，以防止在充电期间锂金属无意地析出在负极上。
(1)正极活性物质层表面的开裂宽度
在一些实施例中，基于所述正极活性物质层的质量，所述正极活性物质的质量百分比为M％，M的取值范围为95至99。
在一些实施例中，M为95、96、97、98、99或这些数值中任意两者组成的范围。当正极活性物质层中正极活性物质的质量百分比高于95％时，可显著提高电化学装置的能量密度。
在一些实施例中，所述正极活性物质层表面的开裂宽度为W mm，W≤2。在一些实施例中、W为0.01、0.02、0.03、0.05、0.08、0.1、0.15、0.2、0.3、0.4、0.5、0.6、0.7、0.8、0.9、1.0、1.4、1.5、1.8、2或这些数值中任意两者组成的范围。当正极活性物质层表面的开裂宽度无限小，尤其没有时，可明显改善电化学装置在高电压下的浮充性能。
在一些实施例中，M和W满足：M/W≥47.5。在一些实施例中，M/W为47.5、50、60、80、90、100、120、150、200、300、400、500、100、1500、1800、2000、5000、8000、9000、10000、15000、18000、20000或这些数值中任意两者组成的范围。
当正极满足上述关系时，不仅能改善正极活性物质层的界面稳定性，而且能够充分抑制电化学装置在常温和高温下的直流内阻增长，且出乎意料地改善高电压下的浮充性能。
正极活性物质层表面的开裂宽度可反映出正极活性物质层的表面性质，其是表征正 极活性物质层的参数之一。开裂宽度越小，正极活性物质层界面平整度越好，可显著改善电化学装置的循环性能、倍率性能、浮充性能以及降低电化学装置的直流内阻。正极活性物质层开裂宽度可受多种因素影响，主要包括正极活性物质层涂布重量、正极活性物质层压实密度、正极活性物质层涂布浆料的固含量、正极活性物质的粒径、正极活性物质的含量、正极活性物质层粘结剂、正极活性物质层助剂、正极活性物质层表面的功能处理层、以及正极活性物质层的孔隙率等。
本申请的开裂是指在正极活性物质层受内应力、外部冲击或环境条件等的影响而在其表面所产生的裂纹。本申请的所述正极活性物质层表面的开裂宽度是指所有裂纹中最大的开裂宽度，其可通过量尺或借助其他测试尺寸的仪器来测定。
(2)正极活性物质层的质量
在一些实施例中，所述正极活性物质层的单位面积质量为M 1mg/1540.25mm 2，M 1的取值范围为100至400。在一些实施例中，M 1为100、120、140、150、160、180、200、240、250、270、280、290、300、350、380、400或这些数值中任意两者组成的范围。当M 1的取值范围为100至400时，正极表面在充放电循环中能够保持结构稳定性，进一步提高了锂离子电池的性能。如果M 1的取值超过400，则活性层太厚，电解液的浸透性降低，同时在电池中电子传输也会困难，引起电池极化增大，从而导致高电流密度充放电特性恶化。另外，如果M 1的取值低于100，活性层在加工过程中对集流体产生较大的冲击，破坏集流体界面，同时活性物质之间的相对位移也会增大，影响性能。
在一些实施例中，M 1和W满足：M 1/W≥50。在一些实施例中，M 1和W满足：M 1/W为50、80、100、150、200、250、300、350、400、500或这些数值中任意两者组成的范围。当正极满足上述关系时，能够获得进一步改善的效果。
(3)正极活性物质层涂布浆料的固含量
在一些实施例中，所述正极活性物质层涂布浆料的固含量为M 2％，M 2的取值范围为55至80。在一些实施例中，M 2为55、58、60、63、65、68、70、72、75、78、80或这些数值中任意两者组成的范围。当M 2的取值范围为55至80时，则正极表面缺陷较少，进一步提高了锂离子电池的性能。如果超过该范围，则极片在烘烤中开裂严重。另外，如果低于该范围，在制备正极活性物质层的过程中会浪费溶剂、延长烘烤时间，从而带来工艺上的损失。
在一些实施例中，M 2和W满足：M 2/W≥27.5。在一些实施例中，M 2/W为27.5、30、 32、35、38、40、45、50、60、70、80、90、100、120、200、300、350、370、400、500、600、700、800、1000、1100、1400、1500、3000、5000、7000、9000、10000、16000、20000或这些数值中任意两者组成的范围。当正极满足上述关系时，能够获得进一步改善的效果。
(4)正极活性物质层中的粘结剂
在一些实施例中，所述正极包括熔点在155℃至270℃范围内的氟系粘结剂。在一些实施例中，所述氟系粘结剂的熔点为155℃、160℃、165℃、170℃、172℃、175℃、180℃、200℃、220℃、220℃、230℃、240℃、250℃、260℃、270℃或这些数值中任意两者组成的范围。
当使用熔点在155℃至270℃范围内的氟系粘结剂时，也获得了优异的高温高压下直流内阻和高温高压下浮充性能。尤其是，当使用熔点在155℃至260℃范围内的氟系粘结剂时，则在极片制备工艺的烘烤或热压环节中能够进一步均匀分布在正极材料颗粒的表面，有效提高粘附效果，抑制极片表面缺陷，进一步提高了锂离子电池的性能。
在一些实施例中，所述氟系粘结剂包括聚偏氟乙烯。在一些实施例中，所述聚偏氟乙烯包括偏氟乙烯作为单体的均聚物、偏氟乙烯(VdF)作为单体的共聚物。在一些实施例中，所述聚偏氟乙烯的末端可经马来酸改性。
在一些实施例中，基于所述正极活性物质层的质量，所述氟系粘结剂的质量百分比为0.5％至3％。在一些实施例中，基于所述正极活性物质层的质量，所述氟系粘结剂的质量百分比为0.5％、0.8％、1.0％、1.5％、1.8％、2.0％、2.2％、2.5％、2.8％、3％或这些数值中任意两者组成的范围。
当氟系粘结剂的含量不足0.5％时，氟系粘结剂对正极活性物质颗粒的覆盖变得不充分，粘结性下降，开裂现象加重。另一方面，当氟系粘结剂的含量超过3％时，正极活性物质颗粒被氟系粘结剂过度覆盖，导致直流电阻上升，在低温环境下不能得到高放电倍率性能，并且在高温环境下不能得到良好的浮充性能。
(5)正极活性物质层中的助剂
在一些实施例中，所述正极活性物质层包括助剂。在一些实施例中，所述助剂包括具有醚键的高分子化合物，其中基于所述正极活性物质层的质量，所述具有醚键的高分子化合物的质量百分比为M 4％，M 4≤0.3。
在一些实施例中，M 4为0.04、0.05、0.06、0.07、0.08、0.1、0.12、0.14、0.15、0.18、0.2、0.25、0.28、0.3或这些数值中任意两者组成的范围。当助剂的含量在以上范围内时，有助于改善电化学装置的以下特性：输出功率特性、负荷特性、低温特性、循环特性以及高温保存特性等。
在一些实施例中，所述具有醚键的高分子化合物的氧化电位大于或等于4.6V。在一些实施例中，所述具有醚键的高分子化合物的氧化电位为4.6V、4.7V、4.8V、4.9V、5.0V、5.1V、5.2V、5.3V、5.4V、5.5V、5.6V、6V或这些数值中任意两者组成的范围。当助剂的氧化电位在以上范围内时，电化学装置的电化学性能稳定且耐高压，有助于改善电化学装置在高温高压下的浮充性能。
在一些实施例中，所述具有醚键的高分子化合物包括聚环氧乙烷、聚醚、聚醇或聚醇酯中的至少一种。
(6)正极活性物质
在一些实施例中，所述正极活性物质的种类没有特别限制，只要是能够以电化学方式吸藏和释放金属离子(例如，锂离子)即可。在一些实施例中，正极活性物质为含有锂和至少一种过渡金属的物质。正极活性物质的实例可包括，但不限于，锂过渡金属复合氧化物和含锂过渡金属磷酸化合物。
在一些实施例中，锂过渡金属复合氧化物中的过渡金属包括V、Ti、Cr、Mn、Fe、Co、Ni、Cu等。在一些实施例中，锂过渡金属复合氧化物包括LiCoO 2等锂钴复合氧化物、LiNiO 2等锂镍复合氧化物、LiMnO 2、LiMn 2O 4、Li 2MnO 4等锂锰复合氧化物、LiNi 1/3Mn 1/3Co 1/3O 2、LiNi 0.5Mn 0.3Co 0.2O 2等锂镍锰钴复合氧化物，其中作为这些锂过渡金属复合氧化物的主体的过渡金属原子的一部分被Na、K、B、F、Al、Ti、V、Cr、Mn、Fe、Co、Li、Ni、Cu、Zn、Mg、Ga、Zr、Si、Nb、Mo、Sn、W等其它元素所取代。锂过渡金属复合氧化物的实例可包括，但不限于，LiNi 0.5Mn 0.5O 2、LiNi 0.85Co 0.10Al 0.05O 2、LiNi 0.33Co 0.33Mn 0.33O 2、LiNi 0.45Co 0.10Al 0.45O 2、LiMn 1.8Al 0.2O 4和LiMn 1.5Ni 0.5O 4等。锂过渡金属复合氧化物的组合的实例包括，但不限于，LiCoO 2与LiMn 2O 4的组合，其中LiMn 2O 4中的一部分Mn可被过渡金属所取代(例如，LiNi 0.33Co 0.33Mn 0.33O 2)，LiCoO 2中的一部分Co可被过渡金属所取代。
在一些实施例中，含锂过渡金属磷酸化合物中的过渡金属包括V、Ti、Cr、Mn、Fe、Co、Ni、Cu等。在一些实施例中，含锂过渡金属磷酸化合物包括LiFePO 4、Li 3Fe 2(PO 4) 3、LiFeP 2O 7等磷酸铁类、LiCoPO 4等磷酸钴类，其中作为这些锂过渡金属磷酸化合物的主体的 过渡金属原子的一部分被Al、Ti、V、Cr、Mn、Fe、Co、Li、Ni、Cu、Zn、Mg、Ga、Zr、Nb、Si等其它元素所取代。
在一些实施例中，正极活性物质中包含磷酸锂，其可提高电化学装置的连续充电特性。磷酸锂的使用没有限制。在一些实施例中，正极活性物质和磷酸锂混合使用。在一些实施例中，相对于上述正极活性物质与磷酸锂的质量，磷酸锂的质量百分比为大于0.1％、大于0.3％或大于0.5％。在一些实施例中，相对于上述正极活性物质与磷酸锂的质量，磷酸锂的质量百分比为小于10％、小于8％或小于5％。在一些实施例中，磷酸锂的含量在上述任意两个数值所组成的范围内。
在上述正极活性物质的表面可附着有与其组成不同的物质。表面附着物质的实例可包括，但不限于：氧化铝、二氧化硅、二氧化钛、氧化锆、氧化镁、氧化钙、氧化硼、氧化锑、氧化铋等氧化物；硫酸锂、硫酸钠、硫酸钾、硫酸镁、硫酸钙、硫酸铝等硫酸盐；碳酸锂、碳酸钙、碳酸镁等碳酸盐；碳等。
这些表面附着物质可以通过下述方法附着于正极活性物质表面：使表面附着物质溶解或悬浮于溶剂中而渗入添加到该正极活性物质中并进行干燥的方法；使表面附着物质前体溶解或悬浮于溶剂中，在渗入添加到该正极活性物质中后，利用加热等使其反应的方法；以及添加到正极活性物质前体中同时进行烧制的方法等等。在附着碳的情况下，还可以使用将碳材料(例如，活性炭等)进行机械附着的方法。
在一些实施例中，基于所述正极活性物质层的质量，表面附着物质的含量为大于0.1ppm、大于1ppm或大于10ppm。在一些实施例中，基于正极活性物质层的质量，表面附着物质的含量为小于10％、小于5％或小于2％。在一些实施例中，基于正极活性物质层的质量，表面附着物质的含量在上述任意两个数值所组成的范围内。
通过在正极活性物质表面附着物质，可以抑制正极活性物质表面的电解液的氧化反应，可以提高电化学装置的寿命。当表面附着物质的量过少时，其效果无法充分表现；当表面附着物质的量过多时，会阻碍锂离子的出入，因而电阻有时会增加。
本申请中，将在正极活性物质的表面附着有与其组成不同的物质的正极活性物质也称为“正极活性物质”。
在一些实施例中，正极活性物质颗粒的形状包括，但不限于，块状、多面体状、球状、椭圆球状、板状、针状和柱状等。在一些实施例中，正极活性物质颗粒包括一次颗粒、二次颗粒或其组合。在一些实施例中，一次颗粒可以凝集而形成二次颗粒。
在一些实施例中，正极活性物质的振实密度为大于0.5g/cm 3、大于0.8g/cm 3或大于1.0g/cm 3。当正极活性物质的振实密度在上述范围内时，可以抑制正极活性物质层形成时所需要的分散介质量及导电材料和正极粘合剂的所需量，由此可以确保正极活性物质的填充率和电化学装置的容量。通过使用振实密度高的复合氧化物粉体，可以形成高密度的正极活性物质层。振实密度通常越大越优选，没有特别的上限。在一些实施例中，正极活性物质的振实密度为小于4.0g/cm 3、小于3.7g/cm 3或小于3.5g/cm 3。当正极活性物质的振实密度的具有如上所述的上限时，可以抑制负荷特性的降低。
正极活性物质的振实密度可通过以下方式计算：将5g至10g的正极活性物质粉体放入10mL的玻璃制量筒中，进行200次冲程20mm的振动，得出粉体填充密度(振实密度)。
当正极活性物质颗粒为一次颗粒时，正极活性物质颗粒的中值粒径(D50)指的是正极活性物质颗粒一次粒径。当正极活性物质颗粒的一次颗粒凝集而形成二次颗粒时，正极活性物质颗粒的中值粒径(D50)指的是正极活性物质颗粒二次粒径。
在一些实施例中，正极活性物质颗粒的中值粒径(D50)为大于0.3μm、大于0.5μm、大于0.8μm或大于1.0μm。在一些实施例中，正极活性物质颗粒的中值粒径(D50)为小于30μm、小于27μm、小于25μm或小于22μm。在一些实施例中，正极活性物质颗粒的中值粒径(D50)在上述任意两个数值所组成的范围内。当正极活性物质颗粒的中值粒径(D50)在上述范围内时，可得到高振实密度的正极活性物质，可以抑制电化学装置性能的降低。另一方面，在电化学装置的正极的制备过程中(即，将正极活性物质、导电材料和粘合剂等用溶剂浆料化而以薄膜状涂布时)，可以防止条纹产生等问题。此处，通过将具有不同中值粒径的两种以上的正极活性物质进行混合，可以进一步提高正极制备时的填充性。
正极活性物质颗粒中值粒径(D50)可利用激光衍射/散射式粒度分布测定装置测定：在使用HORIBA社制造的LA-920作为粒度分布计的情况下，使用0.1％六偏磷酸钠水溶液作为测定时使用的分散介质，在5分钟的超声波分散后将测定折射率设定为1.24而进行测定。
在一些实施例中，所述正极活性物质满足如下条件中的一者：
(1)所述正极活性物质包括磷酸铁锂，所述正极活性物质的D50为D 1μm，其中2×D 1≥W；
(2)所述正极活性物质包括磷酸锰铁锂，所述正极活性物质的D50为D 2μm，其中5×D 2≥W；
(3)所述正极活性物质包括锰酸锂，所述正极活性物质的D50为D 3μm，其中0.1×D 3≥W；
(4)所述正极活性物质包括镍钴锰酸锂，所述正极活性物质的D50为D 4μm，其中0.15×D 4≥W；和
(5)所述正极活性物质包括钴酸锂，所述正极活性物质的D50为D 5μm，其中0.15×D 5≥W。
在一些实施例中，上述正极活性物质如磷酸铁锂、磷酸锰铁锂、锰酸锂、镍钴锰酸锂、钴酸锂可单独使用或任意组合使用。通过选择合适的粒径，可以进一步调节正极极片表面的平整度以及极片的压实密度等，从而提高锂离子电池的性能。
在一些实施例中，所述正极活性物质层进一步包括导电剂。在一些实施例中，所述导电剂包括碳纳米管、碳纤维、乙炔黑、石墨烯、科琴黑或碳黑中的至少一种。
在一些实施例中，所述正极集流体包括铜箔或铝箔中的至少一种。
在一些实施例中，所述正极可以通过本领域公知的制备方法制备。例如，所述正极可以通过如下方法获得：在溶剂中将正极活性材料、导电剂和粘合剂混合，以制备活性材料组合物，并将该活性材料组合物涂覆在集流体上。在一些实施例中，所述溶剂可以包括N-甲基吡咯烷酮等，但不限于此。
2、电解液
在一些实施例中，本申请电化学装置中使用的电解液包括电解质和溶解该电解质的溶剂。在一些实施例中，所述电解液包括添加剂A，所述添加剂A包括具有氰基的化合物或具有F-P-O键的化合物中的至少一种。
当在电解液中添加具有氰基的化合物或具有F-P-O键的化合物时，能够获得优异的高温高压下直流内阻和高温高压下浮充性能。尤其是，当组合使用具有氰基的化合物和具有F-P-O键的化合物时，则可以进一步抑制循环过程中正极表面保护膜的分解和再造带来的极片表面缺陷，从而提高锂离子电池的性能。
在一些实施例中，所述添加剂A的质量百分比为a％，a的取值范围为0.1至15。在一些实施例中，a为0.1、0.4、0.5、0.8、1、1.5、1.8、2、2.5、3、3.5、4、5、6、7、8、9、10、11、12、13、14、15或这些数值中任意两者组成的范围。
在一些实施例中，M/a为6.33、8、10、15、20、24、28、30、32、35、40、45、50、100、150、190、200、250或这些数值中任意两者组成的范围。当满足上述关系时，极片表面的一致性在循环过程中得到较好的保持，因此不仅进一步改善高温高压下直流内阻和高温高压下浮充性能，而且意想不到的是，高电压下的容量保持率和低温下的倍率性能同时得 到提高，这可能是由于在高压和低温下，正极和电解液之间的形成的界面具有良好的稳定性和低阻抗，能够使锂离子更容易脱嵌。
在一些实施例中，所述具有氰基的化合物包括以下化合物中的至少一种：丁二腈、戊二腈、己二腈、1,5-二氰基戊烷、1,6-二氰基己烷、四甲基丁二腈、2-甲基戊二腈、2,4-二甲基戊二腈、2,2,4,4-四甲基戊二腈、1,4-二氰基戊烷、1,2-二氰基苯、1,3-二氰基苯、1,4-二氰基苯、乙二醇双(丙腈)醚、3,5-二氧杂-庚二腈、1,4-二(氰基乙氧基)丁烷、二乙二醇二(2-氰基乙基)醚、三乙二醇二(2-氰基乙基)醚、四乙二醇二(2-氰基乙基)醚、1,3-二(2-氰基乙氧基)丙烷、1,4-二(2-氰基乙氧基)丁烷、1,5-二(2-氰基乙氧基)戊烷、乙二醇二(4-氰基丁基)醚、1,4-二氰基-2-丁烯、1,4-二氰基-2-甲基-2-丁烯、1,4-二氰基-2-乙基-2-丁烯、1,4-二氰基-2,3-二甲基-2-丁烯、1,4-二氰基-2,3-二乙基-2-丁烯、1,6-二氰基-3-己烯、1,6-二氰基-2-甲基-3-己烯、1,3,5-戊三甲腈、1,2,3-丙三甲腈、1,3,6-己三甲腈、1,2,6-己三甲腈、1,2,3-三(2-氰基乙氧基)丙烷、1,2,4-三(2-氰基乙氧基)丁烷、1,1,1-三(氰基乙氧基亚甲基)乙烷、1,1,1-三(氰基乙氧基亚甲基)丙烷、3-甲基-1,3,5-三(氰基乙氧基)戊烷、1,2,7-三(氰基乙氧基)庚烷、1,2,6-三(氰基乙氧基)己烷或1,2,5-三(氰基乙氧基)戊烷。
在一些实施例中，所述具有F-P-O键的化合物包括二氟磷酸锂、式1化合物、式2化合物、式3化合物或式4化合物中的至少一种：
Figure PCTCN2021122314-appb-000003
Figure PCTCN2021122314-appb-000004
在一些实施例中，所述电解液还包括添加剂B，所述添加剂B包括氟代碳酸乙烯酯、1,3-丙磺酸内酯、硫酸乙烯酯、碳酸乙烯亚乙酯、磷酸环酐中的至少一种。
在一些实施例中，所述电解液进一步包含现有技术中已知的任何可作为电解液的溶剂的非水溶剂。
在一些实施例中，所述非水溶剂包括，但不限于，以下中的一种或多种：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，所述环状碳酸酯的实例可包括，但不限于，以下中的一种或多种：碳酸乙烯酯(EC)、碳酸丙烯酯(PC)和碳酸亚丁酯。在一些实施例中，所述环状碳酸酯具有3-6个碳原子。
在一些实施例中，所述链状碳酸酯的实例可包括，但不限于，以下中的一种或多种：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等。被氟取代的链状碳酸酯的实例可包括，但不限于，以下中的一种或多种：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等。
在一些实施例中，所述环状羧酸酯的实例可包括，但不限于，以下中的一种或多种：γ-丁内酯和γ-戊内酯中的一种或多种。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，所述链状羧酸酯的实例可包括，但不限于，以下中的一种或多种：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等。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的实例可包括，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2,2,2-三氟乙酯等。
在一些实施例中，所述环状醚的实例可包括，但不限于，以下中的一种或多种：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，所述链状醚的实例可包括，但不限于，以下中的一种或多种：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-乙氧基甲氧基乙烷等。
在一些实施例中，所述含磷有机溶剂的实例可包括，但不限于，以下中的一种或多种：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)酯等。
在一些实施例中，所述含硫有机溶剂的实例可包括，但不限于，以下中的一种或多种：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，所述芳香族含氟溶剂包括，但不限于，以下中的一种或多种：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：碳酸乙烯酯、碳酸丙烯酯、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：碳酸乙烯酯、碳酸丙烯酯、碳酸二乙酯、丙酸乙酯、丙酸丙酯、γ-丁内酯及其组合。
在一些实施例中，电解质没有特别限制，可以任意地使用作为电解质公知的物质。在锂二次电池的情况下，通常使用锂盐。电解质的实例可包括，但不限于，LiPF 6、LiBF 4、LiClO 4、LiAlF 4、LiSbF 6、LiWF 7等无机锂盐；LiWOF 5等钨酸锂类；HCO 2Li、CH 3CO 2Li、CH 2FCO 2Li、CHF 2CO 2Li、CF 3CO 2Li、CF 3CH 2CO 2Li、CF 3CF 2CO 2Li、CF 3CF 2CF 2CO 2Li、CF 3CF 2CF 2CF 2CO 2Li等羧酸锂盐类；FSO 3Li、CH 3SO 3Li、CH 2FSO 3Li、CHF 2SO 3Li、 CF 3SO 3Li、CF 3CF 2SO 3Li、CF 3CF 2CF 2SO 3Li、CF 3CF 2CF 2CF 2SO 3Li等磺酸锂盐类；LiN(FCO) 2、LiN(FCO)(FSO 2)、LiN(FSO 2) 2、LiN(FSO 2)(CF 3SO 2)、LiN(CF 3SO 2) 2、LiN(C 2F 5SO 2) 2、环状1,2-全氟乙烷双磺酰亚胺锂、环状1,3-全氟丙烷双磺酰亚胺锂、LiN(CF 3SO 2)(C 4F 9SO 2)等酰亚胺锂盐类；LiC(FSO 2) 3、LiC(CF 3SO 2) 3、LiC(C 2F 5SO 2) 3等甲基化锂盐类；双(丙二酸根合)硼酸锂盐、二氟(丙二酸根合)硼酸锂盐等(丙二酸根合)硼酸锂盐类；三(丙二酸根合)磷酸锂、二氟双(丙二酸根合)磷酸锂、四氟(丙二酸根合)磷酸锂等(丙二酸根合)磷酸锂盐类；以及LiPF 4(CF 3) 2、LiPF 4(C 2F 5) 2、LiPF 4(CF 3SO 2) 2、LiPF 4(C 2F 5SO 2) 2、LiBF 3CF 3、LiBF 3C 2F 5、LiBF 3C 3F 7、LiBF 2(CF 3) 2、LiBF 2(C 2F 5) 2、LiBF 2(CF 3SO 2) 2、LiBF 2(C 2F 5SO 2) 2等含氟有机锂盐类；二氟草酸硼酸锂、双(草酸)硼酸锂等草酸硼酸锂盐类；四氟草酸根合磷酸锂、二氟双(草酸根合)磷酸锂、三(草酸根合)磷酸锂等草酸根合磷酸锂盐类等。
在一些实施例中，电解质选自LiPF 6、LiSbF 6、FSO 3Li、CF 3SO 3Li、LiN(FSO 2) 2、LiN(FSO 2)(CF 3SO 2)、LiN(CF 3SO 2) 2、LiN(C 2F 5SO 2) 2、环状1,2-全氟乙烷双磺酰亚胺锂、环状1,3-全氟丙烷双磺酰亚胺锂、LiC(FSO 2) 3、LiC(CF 3SO 2) 3、LiC(C 2F 5SO 2) 3、LiBF 3CF 3、LiBF 3C 2F 5、LiPF 3(CF 3) 3、LiPF 3(C 2F 5) 3、二氟草酸硼酸锂、双(草酸)硼酸锂或二氟双(草酸根合)磷酸锂，其有助于改善电化学装置的输出功率特性、高倍率充放电特性、高温保存特性和循环特性等。
电解质的含量没有特别限制，只要不损害本申请的效果即可。在一些实施例中，电解液中的锂的总摩尔浓度为大于0.3mol/L以上、大于0.4mol/L或大于0.5mol/L。在一些实施例中，电解液中的锂的总摩尔浓度为小于3mol/L、小于2.5mol/L或小于2.0mol/L以下。在一些实施例中，电解液中的锂的总摩尔浓度在上述任意两个数值所组成的范围内。当电解质浓度在上述范围内时，作为带电粒子的锂不会过少，并且可以使粘度处于适当的范围，因而容易确保良好的电导率。
当使用两种以上的电解质的情况下，电解质包括至少一种为选自由单氟磷酸盐、硼酸盐、草酸盐和氟磺酸盐组成的组中的盐。在一些实施例中，电解质包括选自由单氟磷酸盐、草酸盐和氟磺酸盐组成的组中的盐。在一些实施例中，电解质包括锂盐。在一些实施例中，基于电解质的质量，选自由单氟磷酸盐、硼酸盐、草酸盐和氟磺酸盐组成的组中的盐的含量为大于0.01％或大于0.1％。在一些实施例中，基于电解质的质量，选自由单氟磷酸盐、硼酸盐、草酸盐和氟磺酸盐组成的组中的盐的含量为小于20％或小于10％。在一些实施例中，选自由单氟磷酸盐、硼酸盐、草酸盐和氟磺酸盐组成的组中的盐的含 量在上述任意两个数值所组成的范围内。
在一些实施例中，电解质包含选自由单氟磷酸盐、硼酸盐、草酸盐和氟磺酸盐组成的组中的一种以上物质和一种以上的其它盐。作为其它盐，可以举出在上文中例示的锂盐，在一些实施例中为LiPF 6、LiN(FSO 2)(CF 3SO 2)、LiN(CF 3SO 2) 2、LiN(C 2F 5SO 2) 2、环状1,2-全氟乙烷双磺酰亚胺锂、环状1,3-全氟丙烷双磺酰亚胺锂、LiC(FSO 2) 3、LiC(CF 3SO 2) 3、LiC(C 2F 5SO 2) 3、LiBF 3CF 3、LiBF 3C 2F 5、LiPF 3(CF 3) 3、LiPF 3(C 2F 5) 3。在一些实施例中，除此以外的盐为LiPF 6。
在一些实施例中，基于电解质的质量，其它盐的含量为大于0.01％或大于0.1％。在一些实施例中，基于电解质的质量，其它盐的含量为小于20％、小于15％或小于10％。在一些实施例中，其它盐的含量在上述任意两个数值所组成的范围内。具有上述含量的其它盐有助于平衡电解液的电导率和粘度。
3、负极
在一些实施例中，负极包括负极集流体和位于所述负极集流体的一个或两个表面上的负极活性物质层。所述负极活性物质层包含负极活性物质。负极活性物质层可以是一层或多层，多层负极活性物质中的每层可以包含相同或不同的负极活性物质。负极活性物质为任何能够可逆地嵌入和脱嵌锂离子等金属离子的物质。在一些实施例中，负极活性物质的可充电容量大于负极活性物质的放电容量，以防止在充电期间锂金属无意地析出在负极上。
作为保持负极活性物质的集流体，可以任意使用公知的集流体。负极集流体的实例包括，但不限于，铝、铜、镍、不锈钢、镀镍钢等金属材料。在一些实施例中，负极集流体为铜。
在负极集流体为金属材料的情况下，负极集流体形式可包括，但不限于，金属箔、金属圆柱、金属带卷、金属板、金属薄膜、金属板网、冲压金属、发泡金属等。在一些实施例中，负极集流体为金属薄膜。在一些实施例中，负极集流体为铜箔。在一些实施例中，负极集流体为基于压延法的压延铜箔或基于电解法的电解铜箔。
在一些实施例中，负极集流体的厚度为大于1μm或大于5μm。在一些实施例中，负极集流体的厚度为小于100μm或小于50μm。在一些实施例中，负极集流体的厚度在上述任意两个数值所组成的范围内。
负极活性物质没有特别限制，只要能够可逆地吸藏、放出锂离子即可。负极活性物质的实例可包括，但不限于，天然石墨、人造石墨等碳材料；硅(Si)、锡(Sn)等金属；或Si、Sn等金属元素的氧化物等。负极活性物质可以单独使用或组合使用。
在一些实施例中，负极活性物质层还可包括负极粘合剂。负极粘合剂可提高负极活性物质颗粒彼此间的结合和负极活性物质与集流体的结合。负极粘合剂的种类没有特别限制，只要是对于电解液或电极制造时使用的溶剂稳定的材料即可。在一些实施例中，负极粘合剂包括树脂粘合剂。树脂粘合剂的实例包括，但不限于，氟树脂、聚丙烯腈(PAN)、聚酰亚胺树脂、丙烯酸系树脂、聚烯烃树脂等。当使用水系溶剂制备负极合剂浆料时，负极粘合剂包括，但不限于，羧甲基纤维素(CMC)或其盐、苯乙烯-丁二烯橡胶(SBR)、聚丙烯酸(PAA)或其盐、聚乙烯醇等。
在一些实施例中，负极可以通过以下方法制备：在负极集流体上涂布包含负极活性物质、树脂粘合剂等的负极合剂浆料，干燥后，进行压延而在负极集流体的两面形成负极活性物质层，由此可以得到负极。
4、隔离膜
在一些实施例中，为了防止短路，在正极与负极之间通常设置有隔离膜。这种情况下，本申请的电解液通常渗入该隔离膜而使用。
对隔离膜的材料及形状没有特别限制，只要不显著损害本申请的效果即可。所述隔离膜可为由对本申请的电解液稳定的材料所形成的树脂、玻璃纤维、无机物等。在一些实施例中，所述隔离膜包括保液性优异的多孔性片或无纺布状形态的物质等。树脂或玻璃纤维隔离膜的材料的实例可包括，但不限于，聚烯烃、芳香族聚酰胺、聚四氟乙烯、聚醚砜等。在一些实施例中，所述聚烯烃为聚乙烯或聚丙烯。在一些实施例中，所述聚烯烃为聚丙烯。上述隔离膜的材料可以单独使用或任意组合使用。
所述隔离膜还可为上述材料层积而成的材料，其实例包括，但不限于，按照聚丙烯、聚乙烯、聚丙烯的顺序层积而成的三层隔离膜等。
无机物的材料的实例可包括，但不限于，氧化铝、二氧化硅等氧化物、氮化铝、氮化硅等氮化物、硫酸盐(例如，硫酸钡、硫酸钙等)。无机物的形式可包括，但不限于，颗粒状或纤维状。
所述隔离膜的形态可为薄膜形态，其实例包括，但不限于，无纺布、织布、微多孔性膜等。在薄膜形态中，所述隔离膜的孔径为0.01μm至1μm，厚度为5μm至50μm。除了上述独立的薄膜状隔离膜以外，还可以使用下述隔离膜：通过使用树脂类的粘合剂在正极和/或负极的表面形成含有上述无机物颗粒的复合多孔层而形成的隔离膜，例如，将氟树脂作为粘合剂使90％粒径小于1μm的氧化铝颗粒在正极的两面形成多孔层而形成的隔离膜。
所述隔离膜的厚度是任意的。在一些实施例中，所述隔离膜的厚度为大于1μm、大于5μm或大于8μm。在一些实施例中，所述隔离膜的厚度为小于50μm、小于40μm或小于30μm。在一些实施例中，所述隔离膜的厚度在上述任意两个数值所组成的范围内。当所述隔离膜的厚度在上述范围内时，则可以确保绝缘性和机械强度，并可以确保电化学装置的倍率特性和能量密度。
在使用多孔性片或无纺布等多孔质材料作为隔离膜时，隔离膜的孔隙率是任意的。在一些实施例中，所述隔离膜的孔隙率为大于10％、大于15％或大于20％。在一些实施例中，所述隔离膜的孔隙率为小于60％、小于50％或小于45％。在一些实施例中，所述隔离膜的孔隙率在上述任意两个数值所组成的范围内。当所述隔离膜的孔隙率在上述范围内时，可以确保绝缘性和机械强度，并可以抑制膜电阻，使电化学装置具有良好的安全特性。
所述隔离膜的平均孔径也是任意的。在一些实施例中，所述隔离膜的平均孔径为小于0.5μm或小于0.2μm。在一些实施例中，所述隔离膜的平均孔径为大于0.05μm。在一些实施例中，所述隔离膜的平均孔径在上述任意两个数值所组成的范围内。若所述隔离膜的平均孔径超过上述范围，则容易发生短路。当隔离膜的平均孔径在上述范围内时，使电化学装置具有良好的安全特性。
5、电化学装置
在一些实施例中，电化学装置包括电极组、集电结构、外装壳体和保护元件。
电极组
电极组可以是由上述正极和负极隔着上述隔离膜层积而成的层积结构、以及上述正极和负极隔着上述隔离膜以漩涡状卷绕而成的结构中的任一种。在一些实施例中，电极组的质量在电池内容积中所占的比例(电极组占有率)为大于40％或大于50％。在一些实施例中，电极组占有率为小于90％或小于80％。在一些实施例中，电极组占有率在上述任意两个数值所组成的范围内。当电极组占有率在上述范围内时，可以确保电化学装置的容量，同时可以抑制与内部压力上升相伴的反复充放电性能及高温保存等特性的降低。
集电结构
集电结构没有特别限制。在一些实施例中，集电结构为降低配线部分及接合部分的电阻的结构。当电极组为上述层积结构时，适合使用将各电极层的金属芯部分捆成束而焊接至端子上所形成的结构。一片的电极面积增大时，内部电阻增大，因而在电极内设置2个以上的端子而降低电阻也是适合使用的。当电极组为上述卷绕结构时，通过在正极和负极分别设置 2个以上的引线结构，并在端子上捆成束，从而可以降低内部电阻。
外装壳体
外装壳体的材质没有特别限制，只要是对于所使用的电解液稳定的物质即可。外装壳体可使用，但不限于，镀镍钢板、不锈钢、铝或铝合金、镁合金等金属类、或者树脂与铝箔的层积膜。在一些实施例中，外装壳体为铝或铝合金的金属或层积膜。
金属类的外装壳体包括，但不限于，通过激光焊接、电阻焊接、超声波焊接将金属彼此熔敷而形成的封装密闭结构；或者隔着树脂制垫片使用上述金属类形成的铆接结构。使用上述层积膜的外装壳体包括，但不限于，通过将树脂层彼此热粘而形成的封装密闭结构等。为了提高密封性，还可以在上述树脂层之间夹入与层积膜中所用的树脂不同的树脂。在通过集电端子将树脂层热粘而形成密闭结构时，由于金属与树脂的接合，可使用具有极性基团的树脂或导入了极性基团的改性树脂作为夹入的树脂。另外，外装体的形状也是任意的，例如可以为圆筒形、方形、层积型、纽扣型、大型等中的任一种。
保护元件
保护元件可以使用在异常放热或过大电流流过时电阻增大的正温度系数(PTC)、温度熔断器、热敏电阻、在异常放热时通过使电池内部压力或内部温度急剧上升而切断在电路中流过的电流的阀(电流切断阀)等。上述保护元件可选择在高电流的常规使用中不工作的条件的元件，亦可设计成即使不存在保护元件也不至于发生异常放热或热失控的形式。
6、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、二次电池、燃料电池、太阳能电池或电容器。特别地，该电化学装置是锂二次电池，包括锂金属二次电池或锂离子二次电池。
本申请另提供了一种电子装置，其包括根据本申请所述的电化学装置。
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电子装置。在一些实施例中，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。
下面以锂离子电池为例并且结合具体的实施例说明锂离子电池的制备，本领域的技术人员将理解，本申请中描述的制备方法仅是实例，其他任何合适的制备方法均在本申请的范围内。
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。
一、锂离子电池的制备
1、负极的制备
将人造石墨、丁苯橡胶和羧甲基纤维素钠按照96％:2％:2％的质量比例与去离子水混合，搅拌均匀，得到浆料。将浆料涂布在9μm的铜箔上。干燥，冷压，再经过裁片、焊接极耳，得到负极。
2、正极的制备
将正极活性物质(例如钴酸锂)、Super-P和聚偏氟乙烯按照(95-99％):(0.1-5％):(0.1-5％)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。将该正极浆料涂布在12μm的铝箔上，干燥，冷压，再经过裁片、焊接极耳，得到正极。
3、电解液的制备
在干燥氩气环境下，将EC、PP和DEC(质量比1：1：1)混合，加入LiPF 6混合均匀，形成基础电解液，其中LiPF 6的含量为12％。在基础电解液中加入不同含量添加剂得到不同实施例和对比例的电解液。电解液中各物质的质量百分比为基于电解液的总质量计算得到。
电解液中组分的缩写及其名称如下表所示：
材料名称 缩写 材料名称 缩写
碳酸乙烯酯 EC 丙酸丙酯 PP
碳酸二乙酯 DEC 氟代碳酸乙烯酯 FEC
丁二腈 SN 己二腈 ADN
乙二醇二(2-氰基乙基)醚 EDN 1,3,6-己烷三腈 HTCN
1,2,3-三(2-氰基乙氧基)丙烷 TCEP 1,3-丙磺酸内酯 PS
式1化合物 式1 式2化合物 式2
式3化合物 式3 式4化合物 式4
二氟磷酸锂 LiPO 2F 2 硫酸乙烯酯 DTD
碳酸乙烯亚乙酯 VC 1-丙基磷酸环酐 T3P
4、隔离膜的制备
以具有氧化铝涂层的聚乙烯多孔膜作为隔离膜，厚度9μm。
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，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、容量等工序制得锂离子电池。
二、测试方法
1、锂离子电池高温高压下直流内阻的测试方法
在65℃下，将锂离子电池以1.5C恒流充电至4.7V，再以4.7V恒压充电至0.05C，静置30分钟。以0.1C放电10秒，记录电压值为U1，以1C放电360秒，记录电压值为U2。重复充放电步骤5次。“1C”是在1小时内将锂离子电池容量完全放完的电流值。
通过下式计算锂离子电池在65℃下的直流电阻R：
R＝(U2-U1)/(1C-0.1C)。
2、锂离子电池的高温高压下浮充性能的测试方法
在25℃下，将锂离子电池以0.5C放电至4.7V，再以0.5C充电至4.7V，在4.7V下恒压充电至0.05C，置于50℃烘箱中，以20mA为截至电流持续恒压4.7V充电，监控锂离子电池厚度的变化。用初始50％充电状态(State of Charge，SOC)的厚度作为基准，电池厚度增加超过20％视为失效点，记录达到失效点的浮充时间。
3、锂离子电池的高温高压下容量保持率的测试方法
在45℃下，将锂离子电池以1C恒流充电至4.7V，然后恒压充电至电流为0.05C，再用1C恒流放电至3.0V，此时为首次循环。按照上述条件使锂离子电池进行800次循环。循环后的容量保持率按照下式进行计算：
容量保持率＝(800次循环后的放电容量/首次循环的放电容量)×100％。
4、锂离子电池的低温放电性能的测试方法
在25℃下，以0.5C恒流充电到4.7V，恒压充电至0.05C截止，然后以0.5C恒流放电到3.0V截止，记录为25℃放电容量。在25℃下，以0.5C恒流充电到4.7V，恒压充电至0.05C截止，之后将电池置于-20℃恒温箱中，静置2小时，再以0.5C恒流放电到3.0V截止，记录为-20℃放电容量。通过下式计算锂离子电池的放电百分比：
放电百分比＝[-20℃放电容量/25℃放电容量]×100％。
5、开裂宽度的测试方法
取电池拆解出来的正极极片，将极片沿着裂纹方向用小刀裁切成40mm(宽)×100mm(长)的矩形待测样，然后用两块2mm(厚)×70mm(宽)×140mm(长)光滑洁净玻璃板夹紧待测样，制成样品。将样品裂纹侧正面放置于KEYENCE VHX-5000光学显微镜载物台上，使用100×倍率观察并拍照。然后使用VHX-5000软件采用平行线法测量裂纹最宽处的宽度(选择相邻最宽的两点组成直线)，每条裂纹测量5次，取最大值作为开裂宽度，即W mm。
6、氟系粘结剂的熔点的测试方法
氟系粘结剂的熔点可以通过如下操作测定：首先，从电池取出正极，用碳酸二甲酯清洗、使其干燥之后，去除集流体，在适当的分散介质(例如N-甲基吡咯烷酮等)中进行加热、搅拌，从而使粘结剂溶解于分散介质中。之后，通过离心分离而去除正极活性物质，过滤上清液之后，通过蒸干或在水中进行再沉淀，从而可以取出粘结剂。其次，利用差示扫描量热计(DSC例如Rigaku Corporation制Rigaku Thermo plusDSC8230)，将数mg至数十mg的样品以1至10℃/min的升温速度进行加温，将在100℃至300℃为止的温度范围所出现的吸热峰之中表示最大吸热量的温度设为氟系粘结剂的熔点。
7、氟系粘结剂的含量的测试方法
氟系粘结剂的含量通过以下操作而测定：首先，从电池取出正极，用碳酸二甲酯进行清洗并使其干燥。接着，使用差示热天平装置(TG-DTA例如Rigaku Corporation制RigakuThermo plus TG8120)，将数mg至数十mg的样品以1至5℃/min的升温速度，在空气气氛下加热至600℃为止，根据此时的质量减少量，求出正极活性物质层中的氟系粘结剂的含量。需要说明的是，对于是否为由粘结剂导致的质量减少量，如利用上述的粘结剂的熔点测定方法而说明的那样操作，分离粘结剂，在空气气氛下进行仅粘结剂的TG-DTA测定，通过调查粘结剂在多少度燃烧从而可以确认。
三、测试结果
A、表1展示了正极活性物质层中正极活性物质的质量百分比(M％)以及正极活性物质层表面的开裂宽度(Wmm)对锂离子电池的高温高压下直流内阻和高温高压下浮充性能的影响。表1中正极材料为湖南杉杉钴酸锂LC9000E；电解液为基础电解液。实施例1-2至1-13及对比例1-1至1-3与实施例1-1的区别仅在于表1中所列举的参数，其它参数相同。
表1
Figure PCTCN2021122314-appb-000005
由以上测试结果可以看出，当正极活性物质的质量分数为95％至99％，且正极满足M/W≥47.5时，锂离子电池在高温高压下直流内阻和高温高压下浮充性能得到显著改善。具体来说，正极活性物质的质量分数越高越有利于电池能量密度的提升。但是当正极活性物质的质量分数超过99％时，相应的粘结剂和导电剂的比例就会下降，从而使得极片加工困难，造成开裂现象明显。当W≤2时，正极表面和内部的离子电导和电子电导均能得到改善，因此可以获得更低的直流内阻，电化学装置性能更优。一旦极片开裂宽度较大，例如超过2mm，则会对离子电导和电子电导产生严重影响，使电池性能劣化。
本申请通过控制M以及M/W在合适的范围内，可以减少正极表面的缺陷如开裂、凹坑、火山口、针孔等，有效抑制电池充放电循环中正极表面钝化层的不断破坏，减少修复次数，从而使锂离子获得一个顺畅的脱嵌通道，并且减小极片表面的SOC不均(也即电荷载体在缺陷处的蓄积)，因为发生SOC不均的地方往往是极片劣化的起点。
图1示出了本申请实施例1-8中正极活性物质层表面的SEM图片。图片显示正极活性物质层表面具有0.3mm的开裂宽度。
B、表2展示了正极活性物质层的单位面积质量(M 1mg/1540.25mm 2)以及正极活性物质层表面的开裂宽度(Wmm)对锂离子电池的高温高压下直流内阻和高温高压下浮充性能的影响。实施例2-1至2-15与实施例1-1的区别仅在于表2所列参数。
表2
实施例 M 1 W(mm) M 1/W≥50 直流内阻(mΩ) 浮充时间(小时)
1-1 90 2 45 75.1 780
2-1 100 2 50 71.5 796
2-2 150 1 150 71.2 799
2-3 200 0.8 250 70.6 822
2-4 200 1 200 71.3 819
2-5 250 0.8 312.5 70.1 831
2-6 260 0.5 520 69.1 834
2-7 270 0.2 1350 68.3 841
2-8 300 0.2 1500 68.1 852
2-9 300 0.1 3000 64.2 880
2-10 400 0.05 8000 60.1 896
2-11 400 0.01 40000 58.1 915
2-12 400 0.005 80000 50.2 931
2-13 80 3 26.7 131.2 488
2-14 80 1.5 53.3 94.2 450
2-15 420 2 210 93.5 417
由以上测试结果可以看出，当M 1的范围为100至400，且满足M 1/W≥50时，则正极表面在充放电循环中能够保持结构稳定性，进一步降低锂离子电池的直流内阻且改善其浮充性能。
C、表3展示了正极活性物质层涂布浆料的固含量(M 2％)以及正极活性物质层表面的开裂宽度(Wmm)对锂离子电池的高温高压下直流内阻和高温高压下浮充性能的影响。实施例3-1至3-15与实施例1-1的区别仅在于表3所列参数。
表3
实施例 M 2 W(mm) M 2/W≥27.5 直流内阻(mΩ) 浮充时间(小时)
1-1 52 2 26 75.1 780
3-1 65 2 37.5 68.2 812
3-2 70 1 70 67.1 835
3-3 70 0.8 87.5 66.9 879
3-4 75 1 75 65.3 899
3-5 75 0.8 93.8 64.1 875
3-6 75 0.5 150 67.2 869
3-7 75 0.2 375 66.9 871
3-8 80 0.2 400 62.9 877
3-9 75 0.1 750 61.8 902
3-10 75 0.05 1500 57.2 916
3-11 75 0.01 7500 53.1 947
3-12 80 0.005 16000 48.5 975
2-6 52 0.5 124 69.1 834
2-7 52 0.2 310 68.3 841
3-13 60 3 20 120.5 512
3-14 50 1.5 33.3 96.1 479
3-15 85 2 42.5 98.3 422
由以上测试结果可以看出，当正极活性物质层涂布浆料的固含量为55％至80％时，且满足M 2/W≥27.5，正极表面缺陷较少，进一步降低了锂离子电池的直流内阻且改善了锂离子电池的浮充性能。
D、表4-1展示了正极粘结剂的熔点对锂离子电池的高温高压下直流内阻和高温高压下浮充性能的影响。实施例4-1至4-12与实施例1-1的区别仅在于表4-1所列参数。
表4-1
实施例 正极粘结剂(熔点) 直流内阻(mΩ) 浮充时间(小时)
1-1 聚偏氟乙烯(150℃) 75.1 780
4-1 聚偏氟乙烯(170℃) 63.1 879
4-2 聚偏氟乙烯(168℃) 58.9 891
4-3 聚偏氟乙烯(165℃) 55.3 906
4-4 聚偏氟乙烯(160℃) 48.1 984
4-5 聚偏氟乙烯(155℃) 59.3 928
4-6 聚偏氟乙烯(165℃) 45.2 1005
4-7 聚偏氟乙烯(165℃) 41.2 1231
4-8 聚偏氟乙烯(175℃) 70.5 789
4-9 聚偏氟乙烯(225℃) 71.2 801
4-10 聚偏氟乙烯(250℃) 71.9 812
4-11 聚偏氟乙烯(270℃) 72.1 831
4-12 聚偏氟乙烯(280℃) 68.8 758
由以上测试结果可以看出，当使用熔点在155℃至270℃范围内的氟系粘结剂时，进一步降低了锂离子电池的直流内阻且改善了锂离子电池的浮充性能。原因可能是使用熔点在155℃至270℃范围内的氟系粘结剂时，粘结剂在极片制备工艺烘烤或热压环节能够均匀分布在正极材料颗粒的表面，有效提高粘附效果，抑制极片表面缺陷，进一步提高了锂离子电池的性能。
E、表4-2展示了正极助剂的种类和质量百分比(M 4％)对锂离子电池的高温高压下直流内阻和高温高压下浮充性能的影响。实施例4-13至4-21与实施例1-1的区别仅在于表4-2所列参数。实施例4-13至4-21中正极的制备方法如下：将钴酸锂(湖南杉杉LC9000E)、Super-P和聚偏氟乙烯按照95％:2％:3％的质量比例与N-甲基吡咯烷酮混合，再在浆料中加入表4-2中的助剂，搅拌均匀，得到正极浆料。将该正极浆料涂布在12μm的铝箔上，干燥，冷压，再经过裁片、焊接极耳，得到正极。
表4-2
Figure PCTCN2021122314-appb-000006
由以上测试结果可以看出，当在正极浆料中添加0.1％-0.3％具有醚键的高分子化合物时，获得了优异的高温高压下直流内阻和高温高压下浮充性能。尤其是，当具有醚键的高分子化合物的氧化电位高于4.6V时，进一步降低了锂离子电池的直流内阻且改善了锂离子电池的浮充性能。原因可能是在正极浆料中添加具有醚键的高分子化合物时，可以降低正极活性物质层表面的开裂宽度，以进一步抑制了极片的表面缺陷，提高锂离子电池高电压下的性能。
F、表5展示了正极活性物质的种类和粒径(D50)以及正极活性物质层表面的开裂宽度对锂离子电池的高温高压下直流内阻和高温高压下浮充性能的影响。实施例5-1至5-6与实施例1-1的区别仅在于表5所列参数。
表5
Figure PCTCN2021122314-appb-000007
由以上测试结果可以看出，当正极活性物质的粒径以及正极活性物质层表面的开裂宽度满足如下条件中的一者时，进一步降低了锂离子电池的直流内阻且改善了锂离子电池的浮充性能：
(1)所述正极活性物质包括磷酸铁锂，所述正极活性物质的D50为D 1μm，其中2×D 1≥W；
(2)所述正极活性物质包括磷酸锰铁锂，所述正极活性物质的D50为D 2μm，其中5×D 2≥W；
(3)所述正极活性物质包括锰酸锂，所述正极活性物质的D50为D 3μm，其中0.1×D 3≥W；
(4)所述正极活性物质包括镍钴锰酸锂，所述正极活性物质的D50为D 4μm，其中0.15×D 4≥W；和
(5)所述正极活性物质包括钴酸锂，所述正极活性物质的D50为D 5μm，其中0.15×D 5≥W。
原因可能是通过选择合适的粒径，可以进一步调节正极极片表面的平整度，从而提高锂离子电池的性能。
G、表6展示了电解液添加剂的种类或含量以及正极活性物质的质量百分比(M％)对锂离子电池的高温高压下直流内阻和高温高压下浮充性能的影响，其中基于电解液的总质量，添加剂的质量百分比为a％。实施例6-1至6-41与实施例1-1的区别仅在于表6所列参数。
表6
Figure PCTCN2021122314-appb-000008
Figure PCTCN2021122314-appb-000009
由以上测试结果可以看出，当在电解液中添加具有氰基的化合物或具有F-P-O键的化合物时，能够获得优异的高温高压下直流内阻和高温高压下浮充性能。尤其是，当组合使用具有氰基的化合物和具有F-P-O键的化合物时，则可以进一步抑制循环过程中正极表面保护膜的分解和再造带来的极片表面缺陷，从而提高锂离子电池的性能。
更具体地，通过控制添加剂的含量以及M/a在合适的范围内，可以弥补电池在循环过程中极片表面由于SOC不均导致的劣化，添加剂在正极表面形成稳定的保护膜，尤其对于缺陷部位的修复更为重要，当M/a≥6.33时，极片表面的一致性在循环过程中得到较好的保持，因此不仅进一步改善高温高压下直流内阻和高温高压下浮充性能，而且意想不到的是，高电压下的容量保持率和低温下的倍率性能同时得到提高，这可能是由于在高压和低温下，正极和电解液之间的形成的界面具有良好的稳定性和低阻抗，能够使锂离子更容易脱嵌。
此外，当电解液还包括氟代碳酸乙烯酯、1,3-丙磺酸内酯、硫酸乙烯酯、碳酸乙烯亚乙酯、磷酸环酐中的至少一种时，可以进一改善高温高压下直流内阻和高温高压下浮充性能。
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 (15)

  1. 一种电化学装置，其包括正极、负极和电解液，
    所述正极包括正极集流体和位于所述正极集流体上的正极活性物质层，所述正极活性物质层包括正极活性物质，
    其中基于所述正极活性物质层的质量，所述正极活性物质的质量百分比为M％，M的取值范围为95至99，
    所述正极活性物质层表面的开裂宽度为W mm，
    其中M和W满足：M/W≥47.5。
  2. 根据权利要求1所述的电化学装置，其中W≤2。
  3. 根据权利要求1所述的电化学装置，其中所述正极活性物质层的单位面积质量为M 1mg/1540.25mm 2，M 1的取值范围为100至400，其中M 1和W满足：M 1/W≥50。
  4. 根据权利要求1所述的电化学装置，其中所述正极活性物质层涂布浆料的固含量为M 2％，M 2的取值范围为55至80，其中M 2和W满足：M 2/W≥27.5。
  5. 根据权利要求1所述的电化学装置，其中所述正极包括熔点在155℃至270℃范围内的氟系粘结剂。
  6. 根据权利要求1所述的电化学装置，其中所述正极活性物质层包括具有醚键的高分子化合物，其中基于所述正极活性物质层的质量，所述具有醚键的高分子化合物的质量百分比为M 4％，M 4≤0.3。
  7. 根据权利要求6所述的电化学装置，其中所述具有醚键的高分子化合物的氧化电位大于或等于4.6V。
  8. 根据权利要求1所述的电化学装置，其中所述电解液包括添加剂A，所述添加剂A包括具有氰基的化合物或具有F-P-O键的化合物中的至少一种。
  9. 根据权利要求8所述的电化学装置，其中所述添加剂A的质量百分比为a％，a的取值范围为0.1至15。
  10. 根据权利要求9所述的电化学装置，其中M/a≥6.33。
  11. 根据权利要求8所述的电化学装置，其中所述具有氰基的化合物包括以下化合物中的至少一种：丁二腈、戊二腈、己二腈、1,5-二氰基戊烷、1,6-二氰基己烷、四甲基丁二腈、2-甲基戊二腈、2,4-二甲基戊二腈、2,2,4,4-四甲基戊二腈、1,4-二氰基戊烷、1,2-二氰基苯、1,3-二氰基苯、1,4-二氰基苯、乙二醇双(丙腈)醚、3,5-二氧杂-庚二腈、1,4-二(氰基乙氧基)丁烷、二乙二醇二(2-氰基乙基)醚、三乙二醇二(2-氰基乙基)醚、四乙二醇二(2-氰基乙基)醚、1,3-二(2-氰基乙氧基)丙烷、1,4-二(2-氰基乙氧基)丁烷、1,5-二(2-氰基乙氧基)戊烷、乙二醇二(4-氰基丁基)醚、1,4-二氰基-2-丁烯、1,4-二氰基-2-甲基-2-丁烯、1,4-二氰基-2-乙基-2-丁烯、1,4-二氰基-2,3-二甲基-2-丁烯、1,4-二氰基-2,3-二乙基-2-丁烯、1,6-二氰基-3-己烯、1,6-二氰基-2-甲基-3-己烯、1,3,5-戊三甲腈、1,2,3-丙三甲腈、1,3,6-己三甲腈、1,2,6-己三甲腈、1,2,3-三(2-氰基乙氧基)丙烷、1,2,4-三(2-氰基乙氧基)丁烷、1,1,1-三(氰基乙氧基亚甲基)乙烷、1,1,1-三(氰基乙氧基亚甲基)丙烷、3-甲基-1,3,5-三(氰基乙氧基)戊烷、1,2,7-三(氰基乙氧基)庚烷、1,2,6-三(氰基乙氧基)己烷或1,2,5-三(氰基乙氧基)戊烷。
  12. 根据权利要求8所述的电化学装置，其中所述具有F-P-O键的化合物包括二氟磷酸锂、式1化合物、式2化合物、式3化合物或式4化合物中的至少一种：
    Figure PCTCN2021122314-appb-100001
    Figure PCTCN2021122314-appb-100002
  13. 根据权利要求1所述的电化学装置，其中所述正极活性物质满足如下条件中的一者：
    (1)所述正极活性物质包括磷酸铁锂，所述正极活性物质的D50为D 1μm，其中2×D 1≥W；
    (2)所述正极活性物质包括磷酸锰铁锂，所述正极活性物质的D50为D 2μm，其中5×D 2≥W；
    (3)所述正极活性物质包括锰酸锂，所述正极活性物质的D50为D 3μm，其中0.1×D 3≥W；
    (4)所述正极活性物质包括镍钴锰酸锂，所述正极活性物质的D50为D 4μm，其中0.15×D 4≥W；和
    (5)所述正极活性物质包括钴酸锂，所述正极活性物质的D50为D 5μm，其中0.15×D 5≥W。
  14. 根据权利要求8所述的电化学装置，其中所述电解液进一步包括添加剂B，所述添加剂B包括氟代碳酸乙烯酯、1,3-丙磺酸内酯、硫酸乙烯酯、碳酸乙烯亚乙酯或磷酸环酐中的至少一种。
  15. 一种电子装置，其包括根据权利要求1-14中任一项所述的电化学装置。
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