WO2021127991A1 - 电化学装置和电子装置 - Google Patents

电化学装置和电子装置 Download PDF

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WO2021127991A1
WO2021127991A1 PCT/CN2019/127962 CN2019127962W WO2021127991A1 WO 2021127991 A1 WO2021127991 A1 WO 2021127991A1 CN 2019127962 W CN2019127962 W CN 2019127962W WO 2021127991 A1 WO2021127991 A1 WO 2021127991A1
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negative electrode
active material
particles
electrochemical device
electrode active
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PCT/CN2019/127962
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English (en)
French (fr)
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崔辉
冯鹏洋
张水蓉
董佳丽
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东莞新能源科技有限公司
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Priority to US16/963,330 priority Critical patent/US11837698B2/en
Priority to PCT/CN2019/127962 priority patent/WO2021127991A1/zh
Publication of WO2021127991A1 publication Critical patent/WO2021127991A1/zh
Priority to US18/495,165 priority patent/US20240072306A1/en
Priority to US18/495,116 priority patent/US20240055664A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0569—Liquid materials characterised by the solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0034—Fluorinated solvents
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • This application relates to the field of energy storage, in particular to an electrochemical device and an electronic device.
  • Electrochemical devices for example, lithium-ion batteries
  • wearable devices smart phones, drones, and even electric vehicles due to their advantages of high energy density, long cycle life, and no memory effect. They have become the world today. The most promising new type of green chemical power supply.
  • lithium-ion batteries With the expansion of the application of lithium-ion batteries and the development of modern information technology, people have put forward more performance requirements for lithium-ion batteries, such as higher energy density, fast charge and discharge, and so on.
  • this application attempts to solve at least one problem existing in the related field at least to some extent.
  • the present application provides an electrochemical device, which includes a positive electrode, a negative electrode and an electrolyte, wherein:
  • the negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, and the negative electrode active material layer contains a negative electrode active material,
  • the electrolyte includes fluoroethylene carbonate (FEC), and
  • the electrochemical device satisfies the following relationship: 17.55 ⁇ K 1 -K 2 -1.63K 3 2 +11.27K 3 ⁇ 20.80,
  • K 1 represents the specific surface area value per unit mass of the negative electrode active material in m 2 /g, and 1.0 ⁇ K 1 ⁇ 2.0;
  • K 2 represents the content value of the fluoroethylene carbonate required per Ah capacity in g/Ah, and 0.015 ⁇ K 2 ⁇ 0.36;
  • K 3 represents the weight value of the negative electrode active material required per Ah capacity in g/Ah.
  • the negative electrode active material includes first particles, the first particles are secondary particles, and the secondary particles include no less than 2 primary particles, and the number of the secondary particles accounts for 50% to 90% of the total amount of the negative electrode active material particles.
  • the Dv50 of the primary particles in the secondary particles is 2 ⁇ m to 10 ⁇ m, and the Dv50 of the secondary particles is 5 ⁇ m to 20 ⁇ m.
  • the negative active material includes second particles, the second particles are primary particles, and the Dv50 of the second particles is 3 ⁇ m to 10 ⁇ m.
  • the Dv50 of the negative active material is 9 ⁇ m to 25 ⁇ m.
  • the negative active material layer has a porosity of 15% to 40%.
  • the negative electrode further includes a conductive layer having a thickness of 0.5 ⁇ m to 1.5 ⁇ m.
  • the electrolyte further includes an organic solvent, and the organic solvent includes ethyl propionate (EP).
  • EP ethyl propionate
  • the ratio W:P of the content value W of the ethyl propionate required per Ah capacity in g/Ah to the porosity value P of the negative electrode active material layer in percentage is 0.6 To 6.3.
  • the present application provides an electronic device including the electrochemical device according to the present application.
  • FIG. 1 shows the scanning electron microscope (SEM) topography of the negative electrode active material in the electrochemical device of the present application.
  • Figure 2 shows the EIS curve according to Example 34 of the present application.
  • a list of items connected by the term "at least one of” can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then 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 (exclude B); B and C (exclude A); or all of A, B, and C.
  • Project A can contain a single element or multiple elements.
  • Project B can contain a single element or multiple elements.
  • Project C can contain a single element or multiple elements.
  • the application provides an electrochemical device, which includes a positive electrode, a negative electrode and an electrolyte, wherein:
  • the negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, and the negative electrode active material layer contains a negative electrode active material,
  • the electrolyte includes fluoroethylene carbonate, and
  • the electrochemical device satisfies the following relationship: 17.55 ⁇ K 1 -K 2 -1.63K 3 2 +11.27K 3 ⁇ 20.80,
  • K 1 represents the specific surface area value per unit mass of the negative electrode active material in m 2 /g, and 1.0 ⁇ K 1 ⁇ 2.0;
  • K 2 represents the content value of the fluoroethylene carbonate required per Ah capacity in g/Ah, and 0.015 ⁇ K 2 ⁇ 0.36;
  • K 3 represents the weight value of the negative electrode active material required per Ah capacity in g/Ah.
  • FEC is easy to form a film on the negative electrode, and the relationship between FEC and the specific surface area of the negative electrode active material can be determined through the above relationship, which helps to better form a solid electrolyte interface (SEI) film .
  • SEI solid electrolyte interface
  • optimizing the relationship between the electrolyte composition (ie, FEC) and the negative electrode active material can help improve the electrolyte infiltration of the negative electrode active material at a compact density (for example, a compact density of 1.78 g/cm 3 or more).
  • a compact density for example, a compact density of 1.78 g/cm 3 or more.
  • the particle size and specific surface area of the negative active material affect the insertion and extraction paths of lithium ions, thereby affecting the kinetics of lithium ion batteries.
  • the use of a small particle size negative electrode active material with excellent isotropy can reduce the specific surface area of the base surface and increase the specific surface area of the end surface as much as possible while the total specific surface area remains unchanged.
  • the end surface is the surface in the Lc direction and the base surface is La In the direction of the plane, La is the average size of the negative electrode active material in the a-axis direction, and Lc refers to the thickness of the negative electrode active material layer deposited in the c-axis direction perpendicular to it.
  • the increase in the specific surface area of the end face enables lithium ions to directly enter between the negative active material layers from the end face defects, realizing rapid lithium ion migration, reducing the impedance of the lithium ion battery, and improving the kinetics of the lithium ion battery.
  • the deintercalation of lithium ions is easier to expand along the Lc direction, and the small particle size with excellent isotropy will inhibit the interlayer expansion of the negative electrode active material, thereby realizing the improvement of cycle performance.
  • the negative active material includes first particles, the first particles are secondary particles, and the secondary particles include no less than 2 primary particles. In some embodiments, the secondary particles include 3 to 10 primary particles. In some embodiments, the number of the secondary particles accounts for 50% to 95% of the total amount of the negative active material particles. In some embodiments, the number of the secondary particles accounts for 60% to 90% of the total amount of the negative active material particles.
  • the Dv50 of the primary particles in the secondary particles is 2 ⁇ m to 10 ⁇ m, and the Dv50 of the secondary particles is 5 ⁇ m to 20 ⁇ m. In some embodiments, the Dv50 of the primary particles in the secondary particles is 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, or 9 ⁇ m. In some embodiments, the Dv50 of the secondary particles is 8 ⁇ m to 18 ⁇ m. In some embodiments, the Dv50 of the secondary particles is 10 ⁇ m to 15 ⁇ m.
  • the negative active material includes second particles, the second particles are primary particles, and the Dv50 of the second particles is 3 ⁇ m to 10 ⁇ m. In some embodiments, the Dv50 of the second particle is 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, or 9 ⁇ m.
  • FIG. 1 shows the scanning electron microscope (SEM) topography of the negative electrode active material in the electrochemical device of the present application.
  • the negative electrode active material in the electrochemical device of the present application includes primary particles and secondary particles. The combination of the two can make the negative electrode active material have a smaller particle size, a higher end surface area and a lower surface area. The specific surface area of the base surface, thereby reducing the charging resistance of the lithium-ion battery.
  • the Dv50 of the negative active material is 9 ⁇ m to 25 ⁇ m. In some embodiments, the Dv50 of the negative active material is 10 ⁇ m to 20 ⁇ m. In some embodiments, the Dv50 of the negative active material is 12 ⁇ m to 15 ⁇ m.
  • the weight ratio of the second particles to the first particles is 1:9 to 1:1. In some embodiments, the weight ratio of the second particles to the first particles is 1:8, 1:7, 1:6, 1:5, 1:4, 1:3, or 1:2.
  • the negative active material has a porosity of 15% to 40%. In some embodiments, the negative active material has a porosity of 20% to 35%. In some embodiments, the negative active material has a porosity of 25% to 30%.
  • the negative active material has a multi-edge spherical shape.
  • the negative active material has an OI value of 2.0 to 5.0, wherein the X-ray diffraction pattern of the negative active material includes 004 diffraction line patterns and 110 diffraction line patterns, which are obtained from the 004 diffraction line patterns
  • the ratio of the c-axis length C004 of the unit cell length C004 to the a-axis length C110 of the unit cell length obtained from the 110 diffraction line pattern, C004/C110 is the OI value of the negative electrode active material.
  • the negative electrode material has an OI value of 3.0 to 4.0. If the OI value is in this range, a negative electrode active material with better performance and better matching with the electrolyte can be obtained.
  • the negative active material is selected from natural graphite, artificial graphite, mesophase micro-carbon spheres (referred to as MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, At least one of Li-Sn-O alloy, Sn, SnO, SnO 2 , spinel structure lithiated TiO 2 -Li 4 Ti 5 O 12 , and Li-Al alloy.
  • Non-limiting examples of carbon materials include crystalline carbon, amorphous carbon, and mixtures thereof.
  • the crystalline carbon may be amorphous or flake-shaped, flake-shaped, spherical or fibrous natural graphite or artificial graphite.
  • Amorphous carbon can be soft carbon, hard carbon, mesophase pitch carbide, calcined coke, and the like.
  • the negative electrode further includes a conductive layer having a thickness of 0.5 ⁇ m to 1.5 ⁇ m.
  • the conductive layer has a thickness of 0.8 ⁇ m to 1.2 ⁇ m.
  • the conductive layer has a thickness of 1.0 ⁇ m.
  • the conductive material of the conductive layer may include any conductive material as long as it does not cause a chemical change.
  • Non-limiting examples of conductive materials include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanotubes, graphene, etc.), metal-based materials (e.g., metal Powder, metal fibers, etc., such as copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.
  • the conductive material of the conductive layer includes carbon nanotubes, and the diameter of the carbon nanotubes is 1 nm to 30 nm. In some embodiments, the diameter of the carbon nanotubes is 1 nm to 25 nm.
  • the diameter of the carbon nanotubes is 2 nm to 20 nm.
  • the conductive material of the conductive layer includes graphene, and the number of layers of the graphene is 1 to 700 layers. In some embodiments, the number of layers of the graphene is 1 to 500 layers. In some embodiments, the number of layers of the graphene is 1 to 300 layers.
  • the negative electrode further includes a binder
  • the binder is selected from at least one of the following: polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polypropylene Nitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene, butadiene benzene Rubber and acrylic and epoxy.
  • the negative electrode current collector used in the present application may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, foamed nickel, foamed copper, polymer substrates coated with conductive metals, and combinations thereof.
  • the electrolyte further includes an organic solvent, and the organic solvent includes ethyl propionate.
  • the organic solvent further includes ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate (DEC) , Methyl n-propyl carbonate, ethyl n-propyl carbonate, di-n-propyl carbonate, bis(fluoromethyl) carbonate, bis(difluoromethyl) carbonate, bis(trifluoromethyl)carbonic acid Ester, bis(2-fluoroethyl) carbonate, bis(2,2-difluoroethyl) carbonate, bis(2,2,2-trifluoroethyl) carbonate, 2-fluoroethylmethyl Carbonate, 2,2-difluoroethyl methyl carbonate, 2,2,2-trifluoroethyl methyl carbonate, methyl acetate, ethyl acetate, propyl acetate, isopropyl
  • EC ethylene carbonate
  • the content of the organic solvent is 70% to 95%.
  • the content of the ethyl propionate is 5% to 80%.
  • K W and the W:K 1 1 ratio is 0.12 to 1.14.
  • W:K 1 is 0.15 to 1.10.
  • W:K 1 is 0.3 to 1.0.
  • W:K 1 is 0.5 to 0.8.
  • the ratio W:P of the content value W of the ethyl propionate required per Ah capacity in g/Ah to the porosity value P of the negative electrode active material in percentage is 0.6 to 6.3. In some embodiments, W:P is 0.8 to 6.0. In some embodiments, W:P is 1.0 to 5.0. In some embodiments, W:P is 2.0 to 4.0. In some embodiments, W:P is 2.5 to 3.0.
  • the electrolyte includes a lithium salt.
  • the electrolyte that can be used in the electrolyte of the embodiments of the present application includes, but is not limited to: inorganic lithium salts, such as LiClO 4 , LiAsF 6 , LiPF 6 , LiBF 4 , LiSbF 6 , LiSO 3 F, LiN(FSO 2 ) 2, etc.; Fluorine-containing organic lithium salts, such as LiCF 3 SO 3 , LiN(FSO 2 )(CF 3 SO 2 ), LiN(CF 3 SO 2 ) 2 , LiN(C 2 F 5 SO 2 ) 2 , cyclic 1,3- Lithium hexafluoropropane disulfonimide, lithium cyclic 1,2-tetrafluoroethane disulfonimide, LiN (CF 3 SO 2 ) (C 4 F 9 SO 2 ), LiC (CF 3 SO 2 ) 3.
  • inorganic lithium salts such as LiClO 4 ,
  • Lithium salt containing dicarboxylic acid complex such as bis(oxalato) lithium borate, difluorooxalic acid Lithium borate, tris(oxalato) lithium phosphate, diflu
  • the electrolyte includes a combination of LiPF 6 and LiBF 4.
  • the electrolyte includes a combination of an inorganic lithium salt such as LiPF 6 or LiBF 4 and a fluorine-containing organic lithium salt such as LiCF 3 SO 3 , LiN(CF 3 SO 2 ) 2 , and LiN(C 2 F 5 SO 2 ) 2 .
  • the concentration of the electrolyte is in the range of 0.8-3 mol/L, for example, in the range of 0.8-2.5 mol/L, in the range of 0.8-2 mol/L, in the range of 1-2 mol/L, for example It is 1mol/L, 1.15mol/L, 1.2mol/L, 1.5mol/L, 2mol/L or 2.5mol/L.
  • the electrolyte further includes an additive, and the additive is selected from one or more of the following: LiBF4, vinyl sulfate (DTD), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), succinonitrile (SN), adiponitrile (ADN), 1,3-propane sultone (PS), or lithium dioxalate borate.
  • the additive is selected from one or more of the following: LiBF4, vinyl sulfate (DTD), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), succinonitrile (SN), adiponitrile (ADN), 1,3-propane sultone (PS), or lithium dioxalate borate.
  • the positive electrode includes a positive electrode current collector and a positive electrode active material provided on the positive electrode current collector.
  • the specific types of positive electrode active materials are not subject to specific restrictions, and can be selected according to requirements.
  • the positive active material includes a compound that reversibly intercalates and deintercalates lithium ions.
  • the positive active material may include a composite oxide containing lithium and at least one element selected from cobalt, manganese, and nickel.
  • the positive electrode active material is selected from lithium cobalt oxide (LiCoO 2 ), lithium nickel manganese cobalt ternary material, lithium manganese oxide (LiMn 2 O 4 ), lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O 4 ) , One or more of lithium iron phosphate (LiFePO 4 ).
  • the positive active material layer may have a coating on the surface, or may be mixed with another compound having a coating.
  • the coating may include oxides of coating elements, hydroxides of coating elements, oxyhydroxides of coating elements, oxycarbonates of coating elements, and hydroxycarbonates of coating elements ( At least one coating element compound selected from hydroxycarbonate).
  • the compound used for the coating may be amorphous or crystalline.
  • the coating element contained in the coating may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, F, or a mixture thereof.
  • the coating can be applied by any method as long as the method does not adversely affect the performance of the positive electrode active material.
  • the method may include any coating method well-known to those of ordinary skill in the art, such as spraying, dipping, and the like.
  • the positive active material layer further includes a binder, and optionally further includes a positive conductive material.
  • the binder improves the bonding of the positive electrode active material particles to each other, and also improves the bonding of the positive electrode active material to the current collector.
  • binders include polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl chloride Vinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylic (ester) styrene butadiene rubber, epoxy resin, nylon, etc.
  • the positive electrode active material layer includes a positive electrode conductive material, thereby imparting conductivity to the electrode.
  • the positive electrode conductive material may include any conductive material as long as it does not cause a chemical change.
  • Non-limiting examples of positive electrode conductive materials include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powder, metal fiber, etc., Including, for example, copper, nickel, aluminum, silver, etc.), conductive polymers (for example, polyphenylene derivatives), and mixtures thereof.
  • the positive electrode current collector used in the electrochemical device according to the present application may be aluminum (Al), but is not limited thereto.
  • a separator is provided between the positive electrode and the negative electrode to prevent short circuits.
  • the material and shape of the isolation film that can be used in the embodiments of the present application are not particularly limited, and they can be any technology disclosed in the prior art.
  • the isolation membrane includes a polymer or an inorganic substance formed of a material that is stable to the electrolyte of the present application.
  • the isolation film may include a substrate layer and a surface treatment layer.
  • the substrate layer is a non-woven fabric, film or composite film with a porous structure, and the material of the substrate layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate and polyimide.
  • a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be selected.
  • a surface treatment layer is provided on at least one surface of the substrate layer.
  • the surface treatment layer may be a polymer layer or an inorganic substance layer, or a layer formed by a mixed polymer and an inorganic substance.
  • the inorganic layer includes inorganic particles and a binder.
  • the inorganic particles are selected from alumina, silica, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, One or a combination of yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate.
  • the binder is selected from polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, One or a combination of polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.
  • the polymer layer contains a polymer, and the material of the polymer is selected from polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, poly At least one of (vinylidene fluoride-hexafluoropropylene)
  • the electrochemical device of the present application includes any device that undergoes an electrochemical reaction, and specific examples thereof 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, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.
  • the application also provides an electronic device, which includes the electrochemical device according to the application.
  • the use 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-input computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, and headsets.
  • Stereo headsets video recorders, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power assistance Bicycles, bicycles, lighting equipment, toys, game consoles, clocks, power tools, flashlights, cameras, large household storage batteries and lithium-ion capacitors, etc.
  • graphite, binder styrene-butadiene rubber (SBR) and thickener sodium carboxymethyl cellulose (CMC) are mixed in an appropriate amount of deionized water solvent at a weight ratio of 97.4:1.2:1.4 Stir and mix thoroughly to form a uniform negative electrode slurry; coat this slurry on the negative electrode current collector (copper foil or nickel foil), dry, cold press, cut pieces, and weld the tabs to obtain the negative electrode, in which graphite
  • the OI value of is 3.25; the surface of the negative electrode current collector is provided with a conductive layer, the conductive layer contains carbon nanotubes, and the diameter of the carbon nanotubes is 1 nm to 20 nm.
  • the positive active material lithium cobalt oxide (LiCoO 2 ), the conductive agent acetylene black and the binder polyvinylidene fluoride (PVDF) are fully mixed in an appropriate amount of N-methylpyrrolidone (NMP) solvent at a weight ratio of 96:2:2 Stir and mix to form a uniform positive electrode slurry; coat the slurry on the positive electrode current collector aluminum foil, dry, cold press, cut pieces, and weld the tabs to obtain the positive electrode.
  • NMP N-methylpyrrolidone
  • a polyethylene (PE) porous polymer film is used as the isolation membrane.
  • Capacity retention rate remaining discharge capacity/initial discharge capacity ⁇ 100%.
  • Table 1 shows the influence of the specific surface area value K 1 per unit mass of the negative active material, the content value K 2 of FEC, and the weight value K 3 of the negative active material on the capacity retention rate of the lithium ion battery.
  • the negative electrode active material graphite includes second particles with a Dv50 of 2.5 ⁇ m and first particles with a Dv50 of 22 ⁇ m.
  • the weight ratio of the second particles to the first particles is 0.2, W : K 1 is 0.1, W: P is 6.5, and the thickness of the undercoat layer is 1 ⁇ m.
  • Example 1 19 1.5 0.05 4.54 70.1%
  • Example 2 19 1.5 0.1 4.53 70.2%
  • Example 3 19 1.5 0.15 4.52 70.9%
  • Example 4 19 1.5 0.25 4.49 71.2%
  • Example 5 17 1.5 0.15 5.00 70.0%
  • Example 6 18 1.5 0.15 4.78 70.5%
  • Example 7 20 1.5 0.15 4.18 72.2%
  • Example 9 19 1 0.15 4.36 71.5%
  • Example 10 19 1.2 0.15 4.43 71.1%
  • Example 11 19 1.8 0.15 4.60 69.4%
  • Example 12 19 2 0.15 4.65 68.9% Comparative example 1 17 1.5 0.15 4.99 49.50%
  • Comparative example 2 19 3 0.15 4.88 61.20% Comparative example 3 19 1.5 0.5 4.41 50.10%
  • Comparative Example 1 does not satisfy 17.55 ⁇ K 1 -K 2 -1.63K 3 2 +11.27K 3 ⁇ 20.80, and its capacity retention rate is poor.
  • Comparative Examples 2 and 3 satisfy 17.55 ⁇ K 1 -K 2 -1.63K 3 2 +11.27K 3 ⁇ 20.80, K 1 or K 2 is beyond the scope expected by this application (that is, 1.0 ⁇ K 1 ⁇ 2.0 and 0.05 ⁇ K 2 ⁇ 0.25), the capacity retention rate of the lithium ion battery has not been effectively improved.
  • Examples 1-12 not only satisfy 17.55 ⁇ K 1 -K 2 -1.63K 3 2 +11.27K 3 ⁇ 20.80, but also 1.0 ⁇ K 1 ⁇ 2.0 and 0.05 ⁇ K 2 ⁇ 0.25, and the capacity retention rate of the lithium ion battery is remarkable Promote.
  • Table 2 shows the influence of the first particles and the second particles of the negative active material on the DCR of the lithium ion battery.
  • the embodiments shown in Table 2 are further improvements based on Embodiment 3, that is, the difference lies only in the parameters in Table 2.
  • Example 27 when the Dv50 of the second particles of the negative active material is greater than 10 ⁇ m, the DCR of the lithium ion battery is higher.
  • Example 17 when the Dv50 of the second particles of the negative active material is less than 3 ⁇ m, the DCR of the lithium ion battery is higher; as shown in Example 22, when the Dv50 of the first particles of the negative active material is less than 5 ⁇ m, The DCR of lithium ion batteries is relatively high; this is because the negative electrode active material has smaller particles, and the negative electrode is easy to pulverize after coating, which makes the transmission path of lithium ions longer, resulting in an increase in the DCR of lithium ion batteries.
  • Example 28 when the Dv50 of the first particles of the negative active material is greater than 20 ⁇ m, the particles of the negative active material are larger, resulting in an increase in the DCR of the lithium ion battery.
  • the Dv50 of the first particles of the negative electrode active material and the weight ratio of the second particles to the first particles were kept constant, as the Dv50 of the second particles gradually increased in the range of 3 ⁇ m to 10 ⁇ m .
  • the negative electrode active material contains more particles with a larger particle size, so that the isotropy of the graphite layer is reduced, the specific surface area of the base surface increases, the specific surface area of the end surface decreases, the path for lithium ions to enter the graphite layer becomes longer, and the migration of lithium ions becomes longer. Slow, which causes the impedance of the lithium-ion battery to increase and the kinetics to decrease.
  • Table 3 shows the effect of EP content in the electrolyte on the DCR and capacity retention rate of lithium-ion batteries.
  • the examples shown in Table 3 are improvements on the basis of Example 3. That is, the difference is only in the parameters in Table 3.
  • the contents of EC, PC, DEC and EP in Table 3 are calculated based on the total weight of the solvent system .
  • Example 34 when W:K 1 is greater than 1.14, the capacity retention rate of the lithium ion battery is low. As shown in Example 35, when W:K 1 is less than 0.12, the DCR of the lithium ion battery is larger.
  • Table 4 shows the influence of the porosity of the negative electrode active material on the Rct and capacity retention rate of the lithium ion battery.
  • the examples shown in Table 4 are improvements on the basis of Example 3. That is, the difference is only in the parameters in Table 4.
  • the contents of EC, PC, DEC and EP in Table 4 are calculated based on the total weight of the solvent system .
  • Example 36 when W:P is less than 0.6, the capacity retention rate of the lithium ion battery is low. As shown in Example 42, when W:P is greater than 6.3, the electrolyte is insufficient to completely infiltrate the graphite voids, resulting in a higher Rct of the lithium ion battery.
  • Table 5 lists the influence of the thickness of the conductive layer on the negative electrode current collector on the DCR and capacity retention of lithium-ion batteries.
  • the embodiments shown in Table 5 are improvements on the basis of Embodiment 32, that is, the difference lies only in the parameters in Table 5.
  • Example 32 1 46.2 69.40%
  • Example 43 0.4 60.4 58.40%
  • Example 44 0.5 53.4 72.80%
  • Example 45 0.8 49.7 71.90%
  • Example 46 1.5 44.5 69.30%
  • Example 47 1.6 40.8 55.70%
  • Example 48 0 57.3 60.30%
  • Example 48 The preparation method of Example 48 is the same as that of Example 32, except that there is no conductive layer on the negative electrode current collector.
  • references to “embodiments”, “partial examples”, “one embodiment”, “another example”, “examples”, “specific examples” or “partial examples” throughout the specification mean that At least one embodiment or example in this application includes the specific feature, structure, material, or characteristic described in the embodiment or example. Therefore, descriptions appearing in various places throughout the specification, such as: “in some embodiments”, “in embodiments”, “in one embodiment”, “in another example”, “in an example “In”, “in a specific example” or “exemplified”, which are not necessarily quoting the same embodiment or example in this application.
  • the specific features, structures, materials, or characteristics herein can be combined in one or more embodiments or examples in any suitable manner.

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Abstract

一种电化学装置和电子装置，该电化学装置包括正极、负极和电解液，其中：所述负极包括负极集流体和设置在所述负极集流体上的负极活性物质，所述电解液包括氟代碳酸乙烯酯，并且所述电化学装置满足以下关系：17.55≤K 1-K 2-1.63K 3 2+11.27K 3≤20.80，其中：K 1表示以m 2/g计所述负极活性物质的单位质量的比表面积值，并且1.0≤K 1≤2.0；K 2表示以g/Ah计每Ah容量所需的所述氟代碳酸乙烯酯的含量值，并且0.05≤K 2≤0.25；并且K 3表示以g/Ah计每Ah容量所需的所述负极活性物质的重量值。该电化学装置具有改善的动力学性能和循环性能。

Description

电化学装置和电子装置 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电子装置。
背景技术
电化学装置(例如，锂离子电池)由于具有高能量密度、长循环寿命及无记忆效应等优点而被广泛应用于穿戴设备、智能手机、无人机、甚至电动汽车等领域，已成为当今世界最具发展潜力的新型绿色化学电源。随着锂离子电池应用的拓展及现代信息技术的发展，人们对锂离子电池提出了更多性能要求，例如，具有较高的能量密度、可进行快速充放电等。
有鉴于此，确有必要对整个电化学装置进行优化改进，使其在实现快速充放电的同时保持优异的电化学性能。
发明内容
本申请通过提供一种电化学装置和电子装置以试图在至少某种程度上解决至少一种存在于相关领域中的问题。
根据本申请的一个方面，本申请提供了一种电化学装置，其包括正极、负极和电解液，其中：
所述负极包括负极集流体和设置在所述负极集流体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，
所述电解液包括氟代碳酸乙烯酯(FEC)，并且
所述电化学装置满足以下关系：17.55≤K 1-K 2-1.63K 3 2+11.27K 3≤20.80，
其中：
K 1表示以m 2/g计所述负极活性物质的单位质量的比表面积值，并且1.0≤K 1≤2.0；
K 2表示以g/Ah计每Ah容量所需的所述氟代碳酸乙烯酯的含量值，并且0.015≤K 2≤0.36；并且
K 3表示以g/Ah计每Ah容量所需的所述负极活性物质的重量值。
根据本申请的实施例，所述负极活性物质包括第一颗粒，所述第一颗粒为二次颗粒， 所述二次颗粒包含不少于2个一次颗粒，所述二次颗粒的数量占所述负极活性物质颗粒总量的50％至90％。
根据本申请的实施例，所述二次颗粒中的一次颗粒的Dv50为2μm至10μm，且所述二次颗粒的Dv50为5μm至20μm。
根据本申请的实施例，所述负极活性物质包括第二颗粒，所述第二颗粒为一次颗粒，所述第二颗粒的Dv50为3μm至10μm。
根据本申请的实施例，所述负极活性物质的Dv50为9μm至25μm。
根据本申请的实施例，所述负极活性物质层具有15％至40％的孔隙率。
根据本申请的实施例，所述负极进一步包括导电层，所述导电层具有0.5μm至1.5μm的厚度。
根据本申请的实施例，所述电解液进一步包括有机溶剂，所述有机溶剂包括丙酸乙酯(EP)。
根据本申请的实施例，以g/Ah计每Ah容量所需的所述丙酸乙酯的含量值W与所述K 1的比率W∶K 1为0.12至1.14。
根据本申请的实施例，以g/Ah计每Ah容量所需的所述丙酸乙酯的含量值W与以百分数计所述负极活性物质层的孔隙率值P的比率W∶P为0.6至6.3。
根据本申请的另一个方面，本申请提供了一种电子装置，其包括根据本申请的电化学装置。
本申请的额外层面及优点将部分地在后续说明中描述、显示、或是经由本申请实施例的实施而阐释。
附图说明
图1展示了本申请的电化学装置中的负极活性物质的扫描式电子显微镜(SEM)形貌图。
图2展示了根据本申请实施例34的EIS曲线。
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。
在具体实施方式及权利要求书中，由术语“中的至少一种”连接的项目的列表可意味着所列项目的任何组合。例如，如果列出项目A及B，那么短语“A及B中的至少一种”意味着仅A；仅B；或A及B。在另一实例中，如果列出项目A、B及C，那么短语“A、 B及C中的至少一种”意味着仅A；或仅B；仅C；A及B(排除C)；A及C(排除B)；B及C(排除A)；或A、B及C的全部。项目A可包含单个元件或多个元件。项目B可包含单个元件或多个元件。项目C可包含单个元件或多个元件。
本申请提供了一种电化学装置，其包括正极、负极和电解液，其中：
所述负极包括负极集流体和设置在所述负极集流体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，
所述电解液包括氟代碳酸乙烯酯，并且
所述电化学装置满足以下关系：17.55≤K 1-K 2-1.63K 3 2+11.27K 3≤20.80，
其中：
K 1表示以m 2/g计所述负极活性物质的单位质量的比表面积值，并且1.0≤K 1≤2.0；
K 2表示以g/Ah计每Ah容量所需的所述氟代碳酸乙烯酯的含量值，并且0.015≤K 2≤0.36；并且
K 3表示以g/Ah计每Ah容量所需的所述负极活性物质的重量值。
在本申请的电化学装置中，FEC易在负极成膜，通过上述关系式可确定FEC与负极活性物质的比表面积之间的关系，从而有助于更好地形成固体电解质界面(SEI)膜，提高循环后期SEI膜的稳定性，减少副反应产物的形成，最终改善电化学装置的循环性能。此外，优化电解液组分(即，FEC)与负极活性物质之间的关系有助于改善高压实密度(如压实密度为1.78g/cm 3以上)下负极活性物质的电解液浸润，从而改善电化学装置的动力学性能，如直流阻抗和电荷转移阻抗等。
在上述方案的基础上，以下详细说明可用于本申请的负极、电极液、正极、隔离膜、电化学装置和电子装置。
负极
负极活性物质(例如，石墨)的粒径和比表面积会影响锂离子的嵌入和脱出路径，从而影响锂离子电池的动力学。采用各向同性度优异的小粒径负极活性物质能在总比表面积保持不变的情况下尽可能降低基面的比表面积，增加端面比表面积，其中端面为Lc方向的面，基面为La方向的面，La为负极活性物质沿a轴方向的平均大小，Lc指的是负极活性物质层沿与其垂直的c轴方向进行堆积的厚度。端面比表面积的增加，能够使得锂离子直接由端面缺陷位进入负极活性物质层间，实现快速的锂离子迁移，降低锂离子电池阻抗，改善锂离子电池的动力学。在循环过程中，锂离子的脱嵌更易沿Lc方向膨胀，而同向度优异的小粒径会抑制负极活性物质的层间膨胀，从而实现循环性能 的提高。
根据本申请的实施例，所述负极活性物质包括第一颗粒，所述第一颗粒为二次颗粒，所述二次颗粒包含不少于2个一次颗粒。在一些实施例中，所述二次颗粒包含3个至10个一次颗粒。在一些实施例中，所述二次颗粒的数量占所述负极活性物质颗粒总量的50％至95％。在一些实施例中，所述二次颗粒的数量占所述负极活性物质颗粒总量的60％至90％。
根据本申请的实施例，所述二次颗粒中的一次颗粒的Dv50为2μm至10μm，且所述二次颗粒的Dv50为5μm至20μm。在一些实施例中，所述二次颗粒中的一次颗粒的Dv50为3μm、4μm、5μm、6μm、7μm、8μm或9μm。在一些实施例中，所述二次颗粒的Dv50为8μm至18μm。在一些实施例中，所述二次颗粒的Dv50为10μm至15μm。
根据本申请的实施例，所述负极活性物质包括第二颗粒，所述第二颗粒为一次颗粒，所述第二颗粒的Dv50为3μm至10μm。在一些实施例中，所述第二颗粒的Dv50为4μm、5μm、6μm、7μm、8μm或9μm。
图1展示了本申请的电化学装置中的负极活性物质的扫描式电子显微镜(SEM)形貌图。如该图所示，本申请的电化学装置中的负极活性物质包括一次颗粒和二次颗粒，二者的组合可使负极活性物质具有较小的粒径、较高的端面比表面积和较低的基面比表面积，从而降低了锂离子电池的充电阻抗。
根据本申请的实施例，所述负极活性物质的Dv50为9μm至25μm。在一些实施例中，所述负极活性物质的Dv50为10μm至20μm。在一些实施例中，所述负极活性物质的Dv50为12μm至15μm。
根据本申请的实施例，所述第二颗粒与所述第一颗粒的重量比为1∶9至1∶1。在一些实施例中，所述第二颗粒与所述第一颗粒的重量比为1∶8、1∶7、1∶6、1∶5、1∶4、1∶3或1∶2。
根据本申请的实施例，所述负极活性物质具有15％至40％的孔隙率。在一些实施例中，所述负极活性物质具有20％至35％的孔隙率。在一些实施例中，所述负极活性物质具有25％至30％的孔隙率。
根据本申请的实施例，所述负极活性物质具有多边缘类球形状。
根据本申请的实施例，所述负极活性物质具有2.0至5.0的OI值，其中所述负极活性物质的X射线衍射图谱包括004衍射线图形和110衍射线图形，由所述004衍射线 图形得到的单位晶胞长度的c轴长度C004与由所述110衍射线图形得到的单位晶胞长度的a轴长度C110的比值C004/C110为所述负极活性物质的OI值。在一些实施例中，所述负极材料具有3.0至4.0的OI值。OI值在此范围内能够得到性能更优异、与电解液匹配性更好的负极活性材料。
根据本申请的实施例，所述负极活性材料选自天然石墨、人造石墨、中间相微碳球(简称为MCMB)、硬碳、软碳、硅、硅-碳复合物、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO 2、尖晶石结构的锂化TiO 2-Li 4Ti 5O 12、Li-Al合金中的至少一种。碳材料的非限制性示例包括结晶碳、非晶碳和它们的混合物。结晶碳可以是无定形的或片形的、小片形的、球形的或纤维状的天然石墨或人造石墨。非晶碳可以是软碳、硬碳、中间相沥青碳化物、煅烧焦等。
根据本申请的实施例，所述负极进一步包括导电层，所述导电层具有0.5μm至1.5μm的厚度。在一些实施例中，所述导电层具有0.8μm至1.2μm的厚度。在一些实施例中，所述导电层具有1.0μm的厚度。在一些实施例中，所述导电层的导电材料可以包括任何导电材料，只要它不引起化学变化。导电材料的非限制性示例包括基于碳的材料(例如，天然石墨、人造石墨、碳黑、乙炔黑、科琴黑、碳纤维、碳纳米管、石墨烯等)、基于金属的材料(例如，金属粉、金属纤维等，例如铜、镍、铝、银等)、导电聚合物(例如，聚亚苯基衍生物)和它们的混合物。在一些实施例中，所述导电层的导电材料包括碳纳米管，所述碳纳米管的直径为1nm至30nm。在一些实施例中，所述碳纳米管的直径为1nm至25nm。在一些实施例中，所述碳纳米管的直径为2nm至20nm。在一些实施例中，所述导电层的导电材料包括石墨烯，所述石墨烯的层数为1层至700层。在一些实施例中，所述石墨烯的层数为1层至500层。在一些实施例中，所述石墨烯的层数为1层至300层。
根据本申请的实施例，所述负极进一步包括粘结剂，所述粘结剂选自以下的至少一种：聚偏氟乙烯、偏氟乙烯-六氟丙烯的共聚物、聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、羧甲基纤维素钠、聚乙烯呲咯烷酮、聚乙烯醚、聚甲基丙烯酸甲酯、聚四氟乙烯及聚六氟丙烯、丁苯橡胶和丙烯酸酯和环氧树脂。
用于本申请所述的负极集流体可以选自铜箔、镍箔、不锈钢箔、钛箔、泡沫镍、泡沫铜、覆有导电金属的聚合物基底和它们的组合。
电解液
根据本申请的实施例，所述电解液进一步包括有机溶剂，所述有机溶剂包括丙酸乙 酯。
根据本申请的实施例，所述有机溶剂还包含碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸亚丁酯、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、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、2，2，2-三氟乙基甲基碳酸酯、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、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、γ-丁内酯或γ-戊内酯中的至少一种。
根据本申请的实施例，以所述电解液的总重量计，所述有机溶剂的含量为70％至95％。
根据本申请的实施例，以所述有机溶剂的总重量计，所述丙酸乙酯的含量为5％至80％。
根据本申请的实施例，以g/Ah计每Ah容量所需的所述丙酸乙酯的含量值W与所述K 1的比率W∶K 1为0.12至1.14。在一些实施例中，W∶K 1为0.15至1.10。在一些实施例中，W∶K 1为0.3至1.0。在一些实施例中，W∶K 1为0.5至0.8。
根据本申请的实施例，以g/Ah计每Ah容量所需的所述丙酸乙酯的含量值W与以百分数计所述负极活性物质的孔隙率值P的比率W∶P为0.6至6.3。在一些实施例中，W∶P为0.8至6.0。在一些实施例中，W∶P为1.0至5.0。在一些实施例中，W∶P为2.0至4.0。在一些实施例中，W∶P为2.5至3.0。
根据本申请的实施例，所述电解液包括锂盐。可用于本申请实施例的电解液中的电解质包括、但不限于：无机锂盐，例如LiClO 4、LiAsF 6、LiPF 6、LiBF 4、LiSbF 6、LiSO 3F、LiN(FSO 2) 2等；含氟有机锂盐，例如LiCF 3SO 3、LiN(FSO 2)(CF 3SO 2)、LiN(CF 3SO 2) 2、LiN(C 2F 5SO 2) 2、环状1，3-六氟丙烷二磺酰亚胺锂、环状1，2-四氟乙烷二磺酰亚胺锂、LiN(CF 3SO 2)(C 4F 9SO 2)、LiC(CF 3SO 2) 3、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 2(CF 3) 2、LiBF2(C2F5)2、LiBF 2(CF 3SO 2) 2、LiBF 2(C 2F 5SO 2) 2；含二羧酸配合物锂盐，例如双(草酸根合)硼酸锂、二氟草酸根合硼酸锂、三(草酸根合)磷酸锂、二氟双(草酸根合)磷酸锂、四氟(草酸根合)磷酸锂等。另外，上述电解质可以单独使用一种，也可以同时使用两种或两种以上。例如，在一些实施例中，电解质包括 LiPF 6和LiBF 4的组合。在一些实施例中，电解质包括LiPF 6或LiBF 4等无机锂盐与LiCF 3SO 3、LiN(CF 3SO 2) 2、LiN(C 2F 5SO 2) 2等含氟有机锂盐的组合。在一些实施例中，电解质的浓度在0.8-3mol/L的范围内，例如0.8-2.5mol/L的范围内、0.8-2mol/L的范围内、1-2mol/L的范围内、又例如为1mol/L、1.15mol/L、1.2mol/L、1.5mol/L、2mol/L或2.5mol/L。
根据本申请的实施例，所述电解液进一步包括添加剂，所述添加剂选自以下的一种或多种：LiBF4、硫酸乙烯酯(DTD)、碳酸亚乙烯酯(VC)、乙烯基碳酸乙烯酯(VEC)、丁二腈(SN)、己二腈(ADN)、1，3-丙烷磺酸内酯(PS)、或二草酸硼酸锂。
正极
在根据本申请所述的电化学装置中，正极包括正极集流体和设置在所述正极集流体上的正极活性材料。正极活性材料的具体种类均不受到具体的限制，可根据需求进行选择。
例如，在一些实施方案中，正极活性材料包括可逆地嵌入和脱嵌锂离子的化合物。在一些实施方案中，正极活性材料可以包括复合氧化物，所述复合氧化物含有锂以及从钴、锰和镍中选择的至少一种元素。在又一些实施方案中，正极活性材料选自钴酸锂(LiCoO 2)、锂镍锰钴三元材料、锰酸锂(LiMn 2O 4)、镍锰酸锂(LiNi 0.5Mn 1.5O 4)、磷酸铁锂(LiFePO 4)中的一种或几种。
在一些实施方案中，正极活性材料层可以在表面上具有涂层，或者可以与具有涂层的另一化合物混合。所述涂层可以包括从涂覆元素的氧化物、涂覆元素的氢氧化物、涂覆元素的羟基氧化物、涂覆元素的碳酸氧盐(oxycarbonate)和涂覆元素的羟基碳酸盐(hydroxycarbonate)中选择的至少一种涂覆元素化合物。用于涂层的化合物可以是非晶的或结晶的。在涂层中含有的涂覆元素可以包括Mg、Al、Co、K、Na、Ca、Si、Ti、V、Sn、Ge、Ga、B、As、Zr、F或它们的混合物。可以通过任何方法来施加涂层，只要所述方法不对正极活性材料的性能产生不利影响即可。例如，所述方法可以包括对本领域普通技术人员来说众所周知的任何涂覆方法，例如喷涂、浸渍等。
在一些实施方案中，正极活性材料层还包含粘合剂，并且可选地还包括正极导电材料。
粘合剂提高正极活性材料颗粒彼此间的结合，并且还提高正极活性材料与集流体的结合。粘合剂的非限制性示例包括聚乙烯醇、羟丙基纤维素、二乙酰基纤维素、聚氯乙烯、羧化的聚氯乙烯、聚氟乙烯、含亚乙基氧的聚合物、聚乙烯吡咯烷酮、聚氨酯、聚 四氟乙烯、聚偏1，1-二氟乙烯、聚乙烯、聚丙烯、丁苯橡胶、丙烯酸(酯)化的丁苯橡胶、环氧树脂、尼龙等。
正极活性材料层包括正极导电材料，从而赋予电极导电性。所述正极导电材料可以包括任何导电材料，只要它不引起化学变化。正极导电材料的非限制性示例包括基于碳的材料(例如，天然石墨、人造石墨、碳黑、乙炔黑、科琴黑、碳纤维等)、基于金属的材料(例如，金属粉、金属纤维等，包括例如铜、镍、铝、银等)、导电聚合物(例如，聚亚苯基衍生物)和它们的混合物。
用于根据本申请的电化学装置的正极集流体可以是铝(Al)，但不限于此。
隔离膜
在一些实施例中，正极与负极之间设有隔离膜以防止短路。可用于本申请的实施例中使用的隔离膜的材料和形状没有特别限制，其可为任何现有技术中公开的技术。在一些实施例中，隔离膜包括由对本申请的电解液稳定的材料形成的聚合物或无机物等。
例如，隔离膜可包括基材层和表面处理层。基材层为具有多孔结构的无纺布、膜或复合膜，基材层的材料选自聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯和聚酰亚胺中的至少一种。具体的，可选用聚丙烯多孔膜、聚乙烯多孔膜、聚丙烯无纺布、聚乙烯无纺布或聚丙烯-聚乙烯-聚丙烯多孔复合膜。
基材层的至少一个表面上设置有表面处理层，表面处理层可以是聚合物层或无机物层，也可以是混合聚合物与无机物所形成的层。
无机物层包括无机颗粒和粘结剂，无机颗粒选自氧化铝、氧化硅、氧化镁、氧化钛、二氧化铪、氧化锡、二氧化铈、氧化镍、氧化锌、氧化钙、氧化锆、氧化钇、碳化硅、勃姆石、氢氧化铝、氢氧化镁、氢氧化钙和硫酸钡中的一种或几种的组合。粘结剂选自聚偏氟乙烯、偏氟乙烯-六氟丙烯的共聚物、聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯醚、聚甲基丙烯酸甲酯、聚四氟乙烯和聚六氟丙烯中的一种或几种的组合。
聚合物层中包含聚合物，聚合物的材料选自聚酰胺、聚丙烯腈、丙烯酸酯聚合物、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯醚、聚偏氟乙烯、聚(偏氟乙烯-六氟丙烯)中的至少一种
电化学装置
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、锂离子二次电池、锂聚合物二次电池或锂离子聚合物二次电池。
电子装置
本申请另提供了一种电子装置，其包括根据本申请的电化学装置。
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
根据各实施例和对比例的设置将石墨、粘结剂丁苯橡胶(SBR)和增稠剂羧甲基纤维素钠(CMC)按照重量比97.4∶1.2∶1.4在适量的去离子水溶剂中充分搅拌混合，使其形成均匀的负极浆料；将此浆料涂覆于负极集流体(铜箔或镍箔)上，烘干、冷压、裁片、焊接极耳，得到负极，其中石墨的OI值为3.25；负极集流体表面设置有导电层，导电层含碳纳米管，碳纳米管的管径为1nm至20nm。
2、电解液的制备
在含水量＜10ppm的氩气气氛手套箱中，将碳酸乙烯酯(EC)、碳酸丙烯酯(PC)及碳酸二乙酯(DEC)按照3∶3∶4的质量比混合均匀得到非水溶剂，再将充分干燥的LiPF6溶解于上述非水溶剂，最后加入一定质量的氟代碳酸乙烯酯，并可进一步添加上述提出的其他添加剂，得到基础电解液。基础电解液适用于本发明表1和表2所列实施例。表3和表4所列实施例的电解液溶剂体系已具体给出。
3、正极的制备
将正极活性物质钴酸锂(LiCoO 2)、导电剂乙炔黑和粘结剂聚偏二氟乙烯(PVDF)按重量比96∶2∶2在适量的N-甲基吡咯烷酮(NMP)溶剂中充分搅拌混合，使其形成均匀的正极浆料；将此浆料涂覆于正极集流体铝箔上，烘干、冷压、裁片、焊接极耳，得到正极。
4、隔离膜的制备
以聚乙烯(PE)多孔聚合物薄膜作为隔离膜。
5、锂离子电池的制备
将正极、隔离膜和负极按顺序叠好，使隔离膜处于正极和负极之间起到隔离的作用，然后卷绕，置于外包装箔中，注入上述电解液，经过真空封装、静置、化成、整形等工序，即完成锂离子电池的制备。
二、测试方法
1、负极活性物质的扫描式电子显微镜(SEM)测试方法
使用JEOL公司JSM-6360LV型及其配套的X射线能谱仪对样品进行SEM扫描，以对样品的形貌结构和元素分布进行分析。
2、锂离子电池的直流阻抗(DCR)的测试方法
以1.5C的电流将锂离子电池恒流充电至4.2V，再恒压充电至0.05C。静置30min，然后以0.1C的电流放电10s(每0.1s记录对应电压值U1)，以1C的电流放电360s(每0.1s记录对应电压值U2)。重复充放电步骤5次。“1C”是在1小时内将电池容量完全放完的电流值。按如下公式计算锂离子电池在50％荷电状态(SOC)状态下的DCR：
R＝(U2-U1)/(1C-0.1C)。
3、锂离子电池的电化学阻抗谱(EIS)的测试方法
将三电极锂离子电池置于电化学工作站，按照工作电极与参比电极的顺序接好。对电化学体系施加5mV的振幅、500KHz-30mHz频率的正弦波交流信号，获得频域范围内相应电信号反馈，得到锂离子电池的EIS曲线。如图2所示，第一个半圆弧与x轴的右交点为电荷转移阻抗值，即Rct。
4、锂离子电池的常温循环性能的测试方法
将锂离子电池放至25℃恒温箱中，以恒定电流1.5C充电至4.4V，在4.4V下恒压充电至0.05C，再以1.0C恒流放电至3.0V，此记为一个充放电循环过程。按上述方式进行800次循环充放电测试。通过下式计算锂离子电池的容量保持率：
容量保持率＝剩余放电容量/初始放电容量×100％。
三、测试结果
表1展示了负极活性物质的单位质量的比表面积值K 1、FEC的含量值K 2和负极活性物质的重量值K 3对锂离子电池的容量保持率的影响。在表1所示的各实施例和对比例中，负极活性物质石墨包括Dv50为2.5μm的第二颗粒和Dv50为22μm的第一颗粒，第二颗粒与第一颗粒的重量比为0.2，W∶K 1为0.1，且W∶P为6.5，底涂层厚度为1μm。
表1
实施例/对比例 K 1-K 2-1.63K 3 2+11.27K 3 K 1 K 2 K 3 容量保持率
实施例1 19 1.5 0.05 4.54 70.1％
实施例2 19 1.5 0.1 4.53 70.2％
实施例3 19 1.5 0.15 4.52 70.9％
实施例4 19 1.5 0.25 4.49 71.2％
实施例5 17 1.5 0.15 5.00 70.0％
实施例6 18 1.5 0.15 4.78 70.5％
实施例7 20 1.5 0.15 4.18 72.2％
实施例8 20.8 1.5 0.15 3.45 73.0％
实施例9 19 1 0.15 4.36 71.5％
实施例10 19 1.2 0.15 4.43 71.1％
实施例11 19 1.8 0.15 4.60 69.4％
实施例12 19 2 0.15 4.65 68.9％
对比例1 17 1.5 0.15 4.99 49.50％
对比例2 19 3 0.15 4.88 61.20％
对比例3 19 1.5 0.5 4.41 50.10％
如表1所示，对比例1不满足17.55≤K 1-K 2-1.63K 3 2+11.27K 3≤20.80，其容量保持率较差。对比例2和3虽然满足17.55≤K 1-K 2-1.63K 3 2+11.27K 3≤20.80，但K 1或K 2超出了本申请所希望的范围(即，1.0≤K 1≤2.0和0.05≤K 2≤0.25)，锂离子电池的容量保持率没有得到有效改善。实施例1-12不仅满足17.55≤K 1-K 2-1.63K 3 2+11.27K 3≤20.80，而且1.0≤K 1≤2.0以及0.05≤K 2≤0.25，锂离子电池的容量保持率得到显著提升。
如实施例1-4所示，当K 1在1.0-2.0的范围内逐渐增加时，锂离子电池的容量保持率随之略有升高，这是因为当K 1、K 2和K 3之间的关系一定时，随着电解液中FEC的含量(即K 2)的增加，K 3将随之变化。当K 2/K 3保持不变时，锂离子电池的容量保持率变化不明显。当电解液中FEC的含量过高时(例如，对比例3中K 2＝0.5)，电解液对 应的溶剂含量下降，电解液中锂盐解离困难；同时FEC易分解，加速电解液中HF的形成，导致电解液酸度升高，并且HF将攻击正极界面，使得过渡金属溶出加剧，破坏电芯性能，从而导致锂离子电池的容量保持率下降。
如实施例5-8所示，当K 1和K 2保持一定时，K 1-K 2-1.63K 3 2+11.27K 3在17.55-20.80的范围内逐渐升高时，K 3逐渐降低，即对应于单位负极活性物质的FEC的含量升高。FEC带有强吸电子基团，具有较高的还原电位，能够先于溶剂在负极表面还原形成稳定的钝化膜，从而抑制电解液溶剂在负极的还原分解，缓解循环过程中SEI膜的破坏，同时降低电解液在锂离子电池中的消耗。由此，锂离子电池的容量保持率得到显著。
如实施例9-12所示，当K 1-K 2-1.63K 3 2+11.27K 3和K 2在本申请所希望的范围内且保持一定时，随着K 1含量的升高，负极活性物质的比表面积增大，在循环过程中与电解液的接触增多，需要形成的SEI膜增多。但由于K2没有增加，循环过程中SEI膜的破坏无法得到缓解及修复，电解液的消耗加速。由此，锂离子电池的容量保持率逐渐降低。
表2展示了负极活性物质的第一颗粒和第二颗粒对锂离子电池的DCR的影响。表2所示的各实施例是基于实施例3的进一步改进，也即区别仅在于表2中的参数。
表2
Figure PCTCN2019127962-appb-000001
Figure PCTCN2019127962-appb-000002
如实施例27所示，当负极活性物质的第二颗粒的Dv50大于10μm时，锂离子电池的DCR较高。如实施例17所示，当负极活性物质的第二颗粒的Dv50小于3μm时，锂离子电池的DCR较高；如实施例22所示，当负极活性物质的第一颗粒的Dv50小于5μm时，锂离子电池的DCR较高；这是由于负极活性物质的颗粒较小，在涂覆后负极易粉化，使锂离子的传输路径变长，导致锂离子电池的DCR增加。如实施例28所示，当负极活性物质的第一颗粒的Dv50大于20μm时，负极活性物质的颗粒较大，导致锂离子电池的DCR增加。
如实施例13-16所示，当负极活性物质的第一颗粒和第二颗粒的Dv50保持一定时，随着第二颗粒与第一颗粒的重量比在1∶9-1∶1的范围逐渐减小，第一颗粒的相对含量增加，端面比表面积增加，使得锂离子能够直接由端面缺陷位进入石墨层间，实现快速的锂离子迁移，由此降低锂离子电池的阻抗，改善锂离子电池的动力学。
如实施例18-21所示，当负极活性物质的第一颗粒的Dv50和第二颗粒与第一颗粒的重量比保持恒定时，随着第二颗粒的Dv50在3μm至10μm的范围内逐渐增加，负极活性物质包含更多粒径较大的颗粒，使得石墨层的各向同性降低，基面比表面积增加，端面比表面积降低，锂离子进入石墨层间的路径变长，锂离子的迁移变慢，由此导致锂离子电池的阻抗增加，动力学下降。
如实施例23-26所示，当负极活性物质的第二颗粒的Dv50和第二颗粒与第一颗粒的重量比保持恒定时，随着第一颗粒的Dv50在5μm至20μm的范围内逐渐增加，负极活性物质的端面比表面积增加，基面比表面积降低，锂离子进入石墨层间路径变短，由此导致锂离子电池的阻抗增加，动力学下降。
表3展示了电解液中EP的含量对锂离子电池的DCR和容量保持率的影响。表3所示的各实施例是在实施例3的基础上的改进，也即区别仅在于表3中的参数，表3中EC、PC、DEC和EP的含量是基于溶剂体系的总重量计算。
表3
Figure PCTCN2019127962-appb-000003
Figure PCTCN2019127962-appb-000004
如实施例34所示，当W∶K 1大于1.14时，锂离子电池容量保持率低。如实施例35所示，当W∶K 1小于0.12时，锂离子电池的DCR较大。
如实施例29-33所示，随着W∶K 1在0.12-1.14的范围内逐渐增大，锂离子电池的DCR逐渐降低，动力学性能得到改善，但容量保持率逐渐降低。这是因为EP本身粘度较低，随其含量增加，锂离子在电解液中的迁移阻抗降低，在充放电过程中由电解液带来的浓差极化减少，从而使得锂离子电池的动力学提升。但是EP极易氧化(其氧化电位远低于传统碳酸酯溶剂)，在循环过程中易分解产气，使得容量保持率下降。
表4展示了负极活性物质的孔隙率对锂离子电池的Rct和容量保持率的影响。表4所示的各实施例是在实施例3的基础上的改进，也即区别仅在于表4中的参数，表4中EC、PC、DEC和EP的含量是基于溶剂体系的总重量计算。
表4
Figure PCTCN2019127962-appb-000005
如实施例36所示，当W∶P小于0.6时，锂离子电池的容量保持率较低。如实施例42所示，当W∶P大于6.3时，电解液不足，无法完全浸润石墨空隙，导致锂离子电池的Rct较高。
如实施例37-41所示，随着W∶P在0.6-6.3的范围内逐渐降低，锂离子电池的Rct降低，动力学性能得到改善，但容量保持率随之降低。这是因为随W∶P的降低，负极活性物质的孔隙率增大，能够浸润负极活性物质的电解液增多，使得电解液与负极活性 物质的接触增加，从而改善锂离子电池的动力学性能。但随着负极活性物质的孔隙率增大，循环过程中副产物增加，电解液的消耗增加，导致容量保持率下降。
表5中列出了在负极集流体上导电层的厚度对锂离子电池DCR和容量保持率的影响。表5所示的各实施例是在实施例32的基础上的改进，也即区别仅在于表5中的参数。
表5
  导电层的厚度(μm) DCR(mΩ) 容量保持率
实施例32 1 46.2 69.40％
实施例43 0.4 60.4 58.40％
实施例44 0.5 53.4 72.80％
实施例45 0.8 49.7 71.90％
实施例46 1.5 44.5 69.30％
实施例47 1.6 40.8 55.70％
实施例48 0 57.3 60.30％
实施例48与实施例32制备方法相同，不同的是负极集流体上无导电层。
由实施例43-48可知，当负极集流体上的导电层的厚度在0.5μm至1.5μm的范围内时，能够起到传导电子的作用，同时可增加负极活性物质层与负极集流体粘结性，从而在循环过程中减少负极活性物质层的剥离，表现出DCR电荷转移阻抗降低，动力学变好。
整个说明书中对“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 (11)

  1. 一种电化学装置，其包括正极、负极和电解液，其中：
    所述负极包括负极集流体和设置在所述负极集流体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，
    所述电解液包括氟代碳酸乙烯酯，并且
    所述电化学装置满足以下关系：17.55≤K 1-K 2-1.63K 3 2+11.27K 3≤20.80，
    其中：
    K 1表示以m 2/g计所述负极活性物质的单位质量的比表面积值，并且1.0≤K 1≤2.0；
    K 2表示以g/Ah计每Ah容量所需的所述氟代碳酸乙烯酯的含量值，并且0.015≤K 2≤0.36；并且
    K 3表示以g/Ah计每Ah容量所需的所述负极活性物质的重量值。
  2. 根据权利要求1所述的电化学装置，其中所述负极活性物质包括第一颗粒，所述第一颗粒为二次颗粒，所述二次颗粒的数量占所述负极活性物质颗粒总量的50％至95％。
  3. 根据权利要求2所述的电化学装置，其中所述二次颗粒中的一次颗粒的Dv50为2μm至10μm，且所述二次颗粒的Dv50为5μm至20μm。
  4. 根据权利要求1所述的电化学装置，其中所述负极活性物质包括第二颗粒，所述第二颗粒为一次颗粒，所述第二颗粒的Dv50为3μm至10μm。
  5. 根据权利要求1所述的电化学装置，其中所述负极活性物质的Dv50为9μm至25μm。
  6. 根据权利要求1所述的电化学装置，其中所述负极活性物质层具有15％至40％的孔隙率。
  7. 根据权利要求1所述的电化学装置，其中所述负极进一步包括导电层，所述导电层具有0.5μm至1.5μm的厚度。
  8. 根据权利要求1所述的电化学装置，其中所述电解液进一步包括有机溶剂，所述有机溶剂包括丙酸乙酯。
  9. 根据权利要求8所述的电化学装置，其中以所述有机溶剂的总重量计，所述丙酸乙酯的含量为5％至80％。
  10. 根据权利要求8所述的电化学装置，其中以g/Ah计每Ah容量所需的所述丙酸乙酯的含量值W与所述K 1的比率W∶K 1为0.12至1.14。
  11. 根据权利要求8所述的电化学装置，其中以g/Ah计每Ah容量所需的所述丙酸乙酯的含量值W与以百分数计所述负极活性物质层的孔隙率值P的比率W∶P为0.6至6.3。
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