WO2022077350A1 - 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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Publication number
WO2022077350A1
WO2022077350A1 PCT/CN2020/121179 CN2020121179W WO2022077350A1 WO 2022077350 A1 WO2022077350 A1 WO 2022077350A1 CN 2020121179 W CN2020121179 W CN 2020121179W WO 2022077350 A1 WO2022077350 A1 WO 2022077350A1
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Prior art keywords
negative electrode
active material
electrochemical device
electrolyte
positive electrode
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PCT/CN2020/121179
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English (en)
French (fr)
Inventor
王可飞
江兵
张青文
杜昌朝
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宁德新能源科技有限公司
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Application filed by 宁德新能源科技有限公司 filed Critical 宁德新能源科技有限公司
Priority to PCT/CN2020/121179 priority Critical patent/WO2022077350A1/zh
Priority to EP20957129.8A priority patent/EP4220774A1/en
Priority to CN202080014721.1A priority patent/CN113454810A/zh
Priority to JP2023522771A priority patent/JP2023546079A/ja
Publication of WO2022077350A1 publication Critical patent/WO2022077350A1/zh
Priority to US18/300,794 priority patent/US20230275226A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
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    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
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    • 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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    • 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
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    • 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
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    • 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
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    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
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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
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
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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
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H—ELECTRICITY
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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
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
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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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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
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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
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/661—Metal or alloys, e.g. alloy coatings
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of energy storage, in particular to an electrochemical device and an electronic device, in particular to a lithium ion battery.
  • Embodiments of the present application address at least one problem in the related art to at least some extent by providing an electrochemical device and an electronic device with improved high temperature storage performance and overcharge resistance.
  • the present application provides an electrochemical device comprising a positive electrode, a negative electrode and an electrolyte, the negative electrode comprising a negative electrode current collector and a negative electrode mixture layer formed on the negative electrode current collector, the negative electrode mixture
  • the layer includes an anode active material, wherein: the bonding strength between the anode active materials is F N/cm 2 , and F is in the range of 100 to 500; and the electrolyte includes propionate.
  • the negative electrode mixture layer includes rubber, and the rubber includes styrene-butadiene rubber, isoprene rubber, butadiene rubber, fluororubber, acrylonitrile-butadiene rubber, and styrene-propylene rubber at least one of them.
  • the rubber further includes at least one of an acrylic functional group, a chlorotrifluoroethylene functional group or a hexafluoropropylene functional group.
  • the content of the propionate is X % based on the weight of the electrolyte, and X is in the range of 5 to 65.
  • F and X satisfy: 1.6 ⁇ F/X ⁇ 100.
  • the specific surface area of the negative electrode mixture layer is A m 2 /g, and A is in the range of 2 to 5.
  • F and A satisfy: 20 ⁇ F/A ⁇ 250.
  • the negative electrode active material has at least one of the following features:
  • (c) includes a metal including at least one of molybdenum, iron, or copper, and the content of the metal is 0.05% or less based on the weight of the negative electrode mixture layer.
  • the electrolyte further includes at least one of the following compounds:
  • R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are each independently hydrogen or C 1 -C 10 alkyl
  • L 1 and L 2 are each independently -(CR 7 R 8 ) n -;
  • R 7 and R 8 are each independently hydrogen or C 1 -C 10 alkyl
  • n 1, 2 or 3.
  • the compound of formula 1 includes at least one of the following compounds:
  • the content of the compound of Formula 1 ranges from 0.01% to 5% based on the weight of the electrolyte.
  • the content of the compound having a cyano group is b % based on the weight of the electrolyte, and b is in the range of 0.01 to 10.
  • X and b satisfy: 0.5 ⁇ X/b ⁇ 200.
  • the present application provides an electronic device comprising an electrochemical device according to the present application.
  • a list of items linked by the term "at least one of” can mean any combination of the listed items.
  • the phrase "at least one of A and B” means A only; B only; or A and B.
  • the phrase "at least one of A, B, and C” means A only; or B only; C only; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C.
  • Item A may contain a single element or multiple elements.
  • Item B may contain a single element or multiple elements.
  • Item C may contain a single element or multiple elements.
  • the term "at least one of" has the same meaning as the term "at least one of”.
  • alkyl is intended to be a straight chain saturated hydrocarbon structure having 1 to 20 carbon atoms. "Alkyl” is also contemplated to be a branched or cyclic hydrocarbon structure having 3 to 20 carbon atoms. When specifying an alkyl group having a specific carbon number, it is intended to encompass all geometric isomers having that carbon number; thus, for example, “butyl” is meant to include n-butyl, sec-butyl, isobutyl, tert-butyl and cyclobutyl; “propyl” includes n-propyl, isopropyl and cyclopropyl.
  • alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl, n-pentyl, isopentyl, neopentyl, cyclopentyl, methylcyclopentyl, ethylcyclopentyl, n-hexyl, isohexyl, cyclohexyl, n-heptyl, octyl, cyclopropyl, cyclobutyl, norbornyl Base et al.
  • halo refers to the replacement of some or all of the hydrogen atoms in a group with halogen atoms (eg, fluorine, chlorine, bromine, or iodine).
  • the present application uses a combination of a negative electrode active material having a specific adhesive strength and an electrolyte solution including propionate, which can prevent the negative electrode from breaking during high-temperature storage and can fully derive the capacity of the electrochemical device , thereby significantly improving the anti-overcharge performance of the high-temperature storage performance of the electrochemical device.
  • the present application provides an electrochemical device comprising a positive electrode, a negative electrode, and an electrolyte as described below.
  • the negative electrode includes a negative electrode current collector and a negative electrode mixture layer disposed on one or both surfaces of the negative electrode current collector.
  • the negative electrode mixture layer contains a negative electrode active material layer, and the negative electrode active material layer contains a negative electrode active material.
  • the negative electrode mixture layer may be one or more layers, and each layer of the multiple layers of negative electrode active materials may contain the same or different negative electrode active materials.
  • the negative electrode active material is any material that can reversibly intercalate and deintercalate metal ions such as lithium ions.
  • the chargeable capacity of the negative electrode active material is greater than the discharge capacity of the positive electrode active material to prevent unintentional precipitation of lithium metal on the negative electrode during charging.
  • the adhesive strength between the negative electrode active materials is F N/cm 2 , and F is in the range of 100 to 500. In some embodiments, F is in the range of 150 to 450. In some embodiments, F is in the range of 200 to 400. In some embodiments, F is 100, 150, 200, 250, 300, 350, 400, 450, 500, or within a range consisting of any two of the foregoing.
  • F N/cm 2 the adhesive strength between the negative electrode active materials is F N/cm 2 , and F is in the range of 100 to 500. In some embodiments, F is in the range of 150 to 450. In some embodiments, F is in the range of 200 to 400. In some embodiments, F is 100, 150, 200, 250, 300, 350, 400, 450, 500, or within a range consisting of any two of the foregoing.
  • the bonding strength between negative active materials is one of the parameters characterizing the properties of negative active materials, which can be adjusted by adding specific substances (eg, rubber) or adjusting negative slurry formulation, coating process, and the like.
  • the bonding strength between the negative electrode active materials can be measured by the following method: cut the negative electrode of 2cm ⁇ 3cm, peel off the negative electrode mixture layer from one side of the negative electrode, and stick the other side of the negative electrode to the double-sided tape that has been pasted on the glass plate. (Part No.: No.515, manufactured by Nitto Denko Co., Ltd.). Then, the negative electrode current collector is peeled off to obtain a negative electrode mixture layer attached to the double-sided tape, which is used as a sample to be tested. The double-sided tape side of the sample to be tested was attached to the front end (tip diameter: 0.2 cm) of the measuring head of an adhesion tester (trade name: TAC-II, manufactured by RHESCA Co., Ltd.).
  • the measurement probe was pressed into the negative electrode mixture layer and pulled away to conduct a peeling test.
  • the maximum load that caused peeling between the negative electrode active materials was measured.
  • the value obtained by dividing the obtained maximum load by the cross-sectional area (0.031 cm 2 ) of the measuring head was referred to as the adhesive strength between the negative electrode active materials.
  • test conditions are as follows:
  • the pressing speed of the measuring probe is 30mm/min
  • the pressing time of the measuring probe is 10 seconds
  • the indentation load of the measuring probe is 3.9N;
  • the pull-off speed of the measurement probe was 600 mm/min.
  • the negative electrode mixture layer includes rubber.
  • the rubber can effectively improve the interfacial stability of the negative electrode mixture layer, thereby significantly improving the high-temperature storage performance and anti-overcharge performance of the electrochemical device.
  • the rubber includes at least one of styrene-butadiene rubber, isoprene rubber, butadiene rubber, fluororubber, acrylonitrile-butadiene rubber, styrene-propylene rubber.
  • the rubber further includes at least one of acrylic functionality, chlorotrifluoroethylene functionality, or hexafluoropropylene functionality.
  • the content of the rubber is 10% or less based on the weight of the negative electrode mixture layer. In some embodiments, the content of the rubber is 8% or less based on the weight of the negative electrode mixture layer. In some embodiments, the content of the rubber is 5% or less based on the weight of the negative electrode mixture layer. In some embodiments, the content of the rubber is 3% or less based on the weight of the negative electrode mixture layer. In some embodiments, the content of the rubber is 2% or less based on the weight of the negative electrode mixture layer.
  • the specific surface area of the negative electrode mixture layer is A m 2 /g, and A is in the range of 2 to 5. In some embodiments, A is in the range of 3 to 4. In some embodiments, A is 2, 2.5, 3, 3.5, 4, 4.5, or within a range consisting of any two of the foregoing.
  • the specific surface area of the negative electrode mixture layer is within the above range, the precipitation of lithium on the surface of the negative electrode and the gas generation caused by the reaction between the negative electrode and the electrolyte can be suppressed, thereby further improving the high-temperature storage performance and overcharge resistance of the electrochemical device. .
  • the specific surface area (BET) of the negative electrode mixture layer can be measured by using a surface area meter (automatic surface area measuring device manufactured by Okura Riken), pre-drying the sample at 350°C for 15 minutes under nitrogen flow, and then using nitrogen
  • the nitrogen-helium mixed gas whose relative pressure value with respect to atmospheric pressure was accurately adjusted to 0.3 was measured by the nitrogen adsorption BET single-point method using the gas flow method.
  • the bonding strength F N/cm 2 between the negative electrode active materials and the specific surface area A m 2 /g of the negative electrode mixture layer satisfy: 20 ⁇ F/A ⁇ 250. In some embodiments, 30 ⁇ F/A ⁇ 240. In some embodiments, 50 ⁇ F/A ⁇ 200. In some embodiments, 60 ⁇ F/A ⁇ 150. In some embodiments, the F/A is 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 125, 150, 180, 200, 240, 250 or between any two of the above within the range of values.
  • the bonding strength F N/cm 2 between the negative electrode active materials and the specific surface area A m 2 /g of the negative electrode mixture layer satisfy the above relationship, the high temperature storage performance and overcharge resistance of the electrochemical device can be further improved.
  • the negative active material has at least one of the following features (a)-(c):
  • the median particle diameter (D50) of the negative electrode active material means the volume-based average particle diameter obtained by the laser diffraction/scattering method.
  • the negative electrode active material has a median particle size of 5 ⁇ m to 30 ⁇ m. In some embodiments, the negative active material has a median particle size of about 10 ⁇ m to about 25 ⁇ m. In some embodiments, the negative active material has a median particle size of about 15 ⁇ m to about 20 ⁇ m. In some embodiments, the negative active material has about 1 ⁇ m, about 3 ⁇ m, about 5 ⁇ m, about 7 ⁇ m, about 10 ⁇ m, about 15 ⁇ m, about 20 ⁇ m, about 25 ⁇ m, about 30 ⁇ m, or in the range of any two of the above values value particle size. When the median particle diameter of the negative electrode active material is within the above range, the irreversible capacity of the electrochemical device is small and it is easy to uniformly coat the negative electrode.
  • the median particle size (D50) of the negative electrode active material can be determined by the following method: Disperse the negative electrode active material in a 0.2% aqueous solution (about 10 mL) of polyoxyethylene (20) sorbitan monolaurate, and use laser diffraction A/scattering particle size distribution meter (LA-700 manufactured by Horiba, Ltd.) was tested.
  • the negative active material includes at least one of artificial graphite, natural graphite, mesocarbon microspheres, soft carbon, hard carbon, amorphous carbon, silicon-containing material, tin-containing material, and alloy material;
  • the shape of the negative active material includes, but is not limited to, fibrous, spherical, granular, and scaly.
  • the interlayer distance of the lattice plane (002 plane) of the negative electrode active material is in the range of about 0.335 nm to about 0.360 nm, and is in the range of about 0.335 nm to In the range of about 0.350 nm or in the range of about 0.335 nm to about 0.345 nm.
  • the crystallite size (Lc) of the negative electrode active material is greater than about 1.0 nm or greater than about 1.5 nm based on the X-ray diffraction pattern of the Gakushin method.
  • the negative active material has a Raman R value greater than about 0.01, greater than about 0.03, or greater than about 0.1. In some embodiments, the negative active material has a Raman R value of less than about 1.5, less than about 1.2, less than about 1.0, or less than about 0.5. In some embodiments, the Raman R value of the negative electrode active material is within a range composed of any two values above.
  • the Raman half-width of the negative electrode active material around 1580 cm ⁇ 1 is not particularly limited. In some embodiments, the negative electrode active material has a Raman half-width around 1580 cm ⁇ 1 greater than about 10 cm ⁇ 1 or greater than about 15 cm ⁇ 1 . In some embodiments, the negative active material has a Raman half-width around 1580 cm ⁇ 1 of less than about 100 cm ⁇ 1 , less than about 80 cm ⁇ 1 , less than about 60 cm ⁇ 1 , or less than about 40 cm ⁇ 1 . In some embodiments, the Raman half-peak width of the negative electrode active material near 1580 cm ⁇ 1 is in the range composed of any two values above.
  • the negative active material has an aspect ratio of greater than about 1, greater than about 2, or greater than about 3. In some embodiments, the negative active material has an aspect ratio of less than about 10, less than about 8, or less than about 5. In some embodiments, the length-to-thickness ratio of the negative electrode active material is within a range composed of any two values above. When the aspect ratio of the negative electrode active material is within the above range, more uniform coating can be performed.
  • the negative active material includes a metal including at least one of molybdenum, iron, or copper. These metal elements can react with some organic substances with poor conductivity in the negative electrode active material, which is beneficial to the formation of a film on the surface of the negative electrode active material.
  • the above-mentioned metal elements are present in the negative electrode mixture layer in trace amounts to avoid the formation of non-conductive by-products and attach to the surface of the negative electrode.
  • the content of the metal is 0.05% or less based on the weight of the negative electrode mixture layer.
  • the content of the metal is 0.04% or less based on the weight of the negative electrode mixture layer.
  • the content of the metal is 0.03% or less based on the weight of the negative electrode mixture layer.
  • the content of the metal is 0.01% or less based on the weight of the negative electrode mixture layer.
  • the negative electrode mixture layer further includes at least one of a silicon-containing material, a tin-containing material, and an alloy material. In some embodiments, the negative electrode mixture layer further includes at least one of a silicon-containing material and a tin-containing material. In some embodiments, the negative electrode mixture layer further includes one or more of a silicon-containing material, a silicon-carbon composite material, a silicon-oxygen material, an alloy material, and a lithium-containing metal composite oxide material.
  • the negative electrode mixture layer further includes other kinds of negative electrode active materials, for example, one or more materials including metal elements and metalloid elements capable of forming alloys with lithium.
  • the metal elements and metalloid elements include, but are not limited to, Mg, B, Al, Ga, In, Si, Ge, Sn, Pb, Bi, Cd, Ag, Zn, Hf, Zr, Y, Pd and Pt.
  • examples of the metal element and metalloid element include Si, Sn, or a combination thereof. Si and Sn have excellent ability to deintercalate lithium ions, which can provide high energy density for lithium ion batteries.
  • other kinds of negative active materials may also include one or more of metal oxides and polymer compounds.
  • the metal oxides include, but are not limited to, iron oxide, ruthenium oxide, and molybdenum oxide.
  • the polymer compound includes, but is not limited to, polyacetylene, polyaniline, and polypyrrole.
  • the negative electrode mixture layer further includes a negative electrode conductive material
  • the conductive material may include any conductive material as long as it does not cause chemical changes.
  • conductive materials include carbon-based materials (eg, natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, etc.), conductive polymers (eg, polyphenylene derivatives), and their mixture.
  • the negative electrode mixture layer further includes a negative electrode binder.
  • the negative electrode binder can improve the bonding of the negative electrode active material particles to each other and the bonding of the negative electrode active material to the current collector.
  • the type of the negative electrode binder is not particularly limited, as long as it is a material that is stable to the electrolyte solution or the solvent used in the production of the electrode.
  • negative electrode binders include, but are not limited to, polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aramid, polyimide, cellulose, nitrocellulose Resin-based polymers such as plain; styrene-butadiene rubber (SBR), isoprene rubber, polybutadiene rubber, fluororubber, acrylonitrile-butadiene rubber (NBR), ethylene-propylene rubber and other rubber-like polymers; styrene ⁇ Butadiene ⁇ styrene block copolymer or its hydrogenated product; ethylene ⁇ propylene ⁇ diene terpolymer (EPDM), styrene ⁇ ethylene ⁇ butadiene ⁇ styrene copolymer, styrene ⁇ isoprene Thermoplastic elastomer-like polymers such as ethylene-styrene block copolymers or their hydrogenated products; syndiotactic-1,
  • the content of the negative electrode binder is greater than about 1%, greater than About 2% or greater than about 3%. In some embodiments, the content of the negative electrode binder is less than about 10%, less than about 8%, or less than about 5% based on the weight of the negative electrode mixture layer. Based on the weight of the negative electrode mixture layer, the content of the negative electrode binder is within a range composed of any two of the above numerical values.
  • the kind of the solvent used to form the negative electrode slurry is not particularly limited, as long as it is a solvent capable of dissolving or dispersing the negative electrode active material, the negative electrode binder, and the thickener and conductive material used as necessary.
  • the solvent used to form the negative electrode slurry may use any one of an aqueous solvent and an organic solvent.
  • the aqueous solvent may include, but are not limited to, water, alcohol, and the like.
  • organic solvents may include, but are not limited to, N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate , diethyltriamine, N,N-dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, hexamethylphosphoramide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, Methyl naphthalene, hexane, etc.
  • NMP N-methylpyrrolidone
  • dimethylformamide dimethylacetamide
  • methyl ethyl ketone cyclohexanone
  • methyl acetate methyl acrylate
  • diethyltriamine N,N-dimethylaminopropylamine
  • THF t
  • the thickener is usually used to adjust the viscosity of the negative electrode slurry.
  • the kind of thickener is not particularly limited, and examples thereof may include, but are not limited to, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch , casein and their salts, etc.
  • the above-mentioned thickeners may be used alone or in any combination.
  • the content of the thickener is greater than about 0.1%, greater than about 0.5%, or greater than about 0.6% based on the weight of the negative mixture layer. In some embodiments, the content of the thickener is less than about 5%, less than about 3%, or less than about 2% based on the weight of the negative electrode mixture layer. When the content of the thickener is within the above range, the reduction in capacity and the increase in resistance of the electrochemical device can be suppressed, and at the same time, good coatability of the negative electrode slurry can be ensured.
  • the surface of the negative electrode mixture layer may have substances with different compositions attached thereto.
  • the surface adhering substances of the negative electrode mixture layer include, but are not limited to: oxides such as alumina, silica, titania, zirconia, magnesia, calcium oxide, boron oxide, antimony oxide, bismuth oxide, etc.; lithium sulfate, sodium sulfate , potassium sulfate, magnesium sulfate, calcium sulfate, aluminum sulfate and other sulfates; lithium carbonate, calcium carbonate, magnesium carbonate and other carbonates.
  • the content of the negative electrode active material is greater than about 80%, greater than about 82%, or greater than about 84% based on the weight of the negative electrode mixture layer. In some embodiments, the content of the negative electrode active material is less than about 99% or less than about 98% based on the weight of the negative electrode mixture layer. In some embodiments, based on the weight of the negative electrode mixture layer, the content of the negative electrode active material is within the range formed by any two of the foregoing arrays.
  • the density of the negative active material in the negative mixture layer is greater than about 1 g/cm 3 , greater than about 1.2 g/cm 3 , or greater than about 1.3 g/cm 3 . In some embodiments, the density of the negative active material in the negative mixture layer is less than about 2.2 g/cm 3 , less than about 2.1 g/cm 3 , less than about 2.0 g/cm 3 , or less than about 1.9 g/cm 3 . In some embodiments, the density of the negative electrode active material in the negative electrode mixture layer is within a range composed of any two values above.
  • the density of the negative electrode active material is within the above range, the destruction of the negative electrode active material particles can be prevented, and the increase of the irreversible capacity of the electrochemical device at the initial stage or the decrease in the permeability of the electrolyte near the interface of the negative electrode current collector/negative electrode active material can be suppressed.
  • the high current density charge-discharge characteristics deteriorate, and the capacity reduction and resistance increase of the electrochemical device can also be suppressed.
  • any known current collector can be used.
  • negative electrode current collectors include, but are not limited to, metal materials such as aluminum, copper, nickel, stainless steel, nickel-plated steel, and the like.
  • the anode current collector is copper.
  • the negative electrode current collector form may include, but is not limited to, metal foil, metal cylinder, metal coil, metal plate, metal film, metal mesh, stamped metal, foamed metal, etc.
  • the negative electrode current collector is a thin metal film.
  • the negative electrode current collector is copper foil.
  • the negative electrode current collector is a calendered copper foil based on a calendering method or an electrolytic copper foil based on an electrolytic method.
  • the thickness of the anode current collector is greater than about 1 ⁇ m or greater than about 5 ⁇ m. In some embodiments, the thickness of the negative current collector is less than about 100 ⁇ m or less than about 50 ⁇ m. In some embodiments, the thickness of the negative electrode current collector is within a range composed of any two of the above-mentioned values.
  • the thickness ratio of the negative electrode mixture layer to the negative electrode current collector refers to the thickness of the single-sided negative electrode mixture layer divided by the thickness of the negative electrode current collector, and its value is not particularly limited. In some embodiments, the thickness ratio is 50 or less. In some embodiments, the thickness ratio is 30 or less. In some embodiments, the thickness ratio is 20 or less. In some embodiments, the thickness ratio is 10 or less. In some embodiments, the thickness ratio is 1 or more. In some embodiments, the thickness ratio is within a range consisting of any two of the foregoing values. When the thickness ratio is within the above-mentioned range, the capacity of the electrochemical device can be ensured, and the heat release of the negative electrode current collector during charge and discharge at a high current density can be suppressed.
  • the electrolytic solution used in the electrochemical device of the present application includes an electrolyte and a solvent that dissolves the electrolyte.
  • the electrolyte used in the electrochemical devices of the present application further includes additives.
  • electrolyte includes propionate
  • the propionate comprises a compound of formula 2:
  • R 1 is selected from ethyl or haloethyl
  • R 2 is selected from C 1 -C 6 alkyl or C 1 -C 6 haloalkyl.
  • the propionate includes, but is not limited to, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, pentyl propionate, methyl halopropionate, halopropionate Ethyl halopropionate, propyl halopropionate, butyl halopropionate and pentyl halopropionate.
  • the propionate is selected from at least one of methyl propionate, ethyl propionate, propyl propionate, butyl propionate, and pentyl propionate.
  • the halogen group in the methyl halopropionate, ethyl halopropionate, propyl halopropionate, butyl halopropionate, and pentyl halopropionate is selected from fluoro One or more of group (-F), chlorine group (-Cl), bromine group (-Br) and iodine group (-I).
  • the halogen group is a fluorine group (-F), which can achieve more excellent effects.
  • the propionate is present in an amount of X % based on the weight of the electrolyte, and X is in the range of 5 to 65. In some embodiments, X is in the range of 10 to 60. In some embodiments, X is in the range of 15 to 50. In some embodiments, X is in the range of 20 to 40. In some embodiments, X is 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, or within a range consisting of any two of the foregoing. When the content of propionate in the electrolyte is within the above range, the high temperature storage performance and overcharge resistance of the electrochemical device can be further improved.
  • the content X% of propionate in the electrolyte and the adhesive strength F N/cm 2 satisfy: 1.6 ⁇ F/X ⁇ 100. In some embodiments, 2 ⁇ F/X ⁇ 80. In some embodiments, 3 ⁇ F/X ⁇ 70. In some embodiments, 5 ⁇ F/X ⁇ 60. In some embodiments, 6 ⁇ F/X ⁇ 50. In some embodiments, F/X is 1.6, 3, 5, 7, 8, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, or a range of any two of the above Inside.
  • the electrolyte further includes at least one of the following compounds:
  • R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are each independently hydrogen or C 1 -C 10 alkyl
  • L 1 and L 2 are each independently -(CR 7 R 8 ) n -;
  • R 7 and R 8 are each independently hydrogen or C 1 -C 10 alkyl
  • n 1, 2 or 3.
  • the fluorocarbonate can act together with the propionate to form a stable protective film on the surface of the negative electrode, thereby suppressing the decomposition reaction of the electrolyte.
  • examples of the fluorocarbonate may include, but are not limited to, one or more of the following: fluoroethylene carbonate, cis-4,4-difluoroethylene carbonate, trans-4 ,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4-fluoro-4-methyl ethylene carbonate, 4-fluoro-5-methyl ethylene carbonate, trifluoromethyl methyl carbonate , trifluoroethyl methyl carbonate and ethyl trifluoroethyl carbonate, etc.
  • the content of the fluorocarbonate ranges from 0.1% to 10% based on the weight of the electrolyte. In some embodiments, the content of the fluorocarbonate ranges from 0.5% to 8% based on the weight of the electrolyte. In some embodiments, the content of the fluorocarbonate ranges from 1% to 5% based on the weight of the electrolyte. In some embodiments, based on the weight of the electrolyte, the content of the fluorocarbonate is 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or within the range of any two of the above values.
  • compounds with a cyano group include, but are not limited to, one or more of the following: succinonitrile, glutaronitrile, adiponitrile, 1,5-dicyanopentane, 1,6 -dicyanohexane, tetramethylsuccinonitrile, 2-methylglutaronitrile, 2,4-dimethylglutaronitrile, 2,2,4,4-tetramethylglutaronitrile, 1, 4-dicyanopentane, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, ethylene glycol bis(propionitrile) ether, 3,5-dicyanobenzene Oxa-pimelonitrile, 1,4-bis(cyanoethoxy)butane, diethylene glycol bis(2-cyanoethyl) ether, triethylene glycol bis(2-cyanoethyl) ether, tetraethylene glycol bis(2-cyanoeth
  • the above-mentioned compounds having a cyano group may be used alone or in any combination. If the electrolyte contains two or more compounds having a cyano group, the content of the compound having a cyano group refers to the total content of the two or more compounds having a cyano group.
  • the content of the compound having a cyano group is b % based on the weight of the electrolyte, and b is in the range of 0.01 to 10. In some embodiments, b is in the range of 0.05 to 8. In some embodiments, b is in the range of 0.1 to 5. In some embodiments, b is in the range of 0.5 to 3. In some embodiments, b is in the range of 1 to 2. In some embodiments, b is 0.01, 0.05, 0.1, 0.5, 1, 2, 5, 8, 10, or within a range of any two of the above. When the content of the compound having a cyano group in the electrolyte is within the above range, the high-temperature storage performance and overcharge resistance of the electrochemical device can be further improved.
  • the content X% of the propionate in the electrolyte and the content b% of the compound having a cyano group satisfy: 0.5 ⁇ X/b ⁇ 200. In some embodiments, 1 ⁇ X/b ⁇ 150. In some embodiments, 5 ⁇ X/b ⁇ 100. In some embodiments, 10 ⁇ X/b ⁇ 80. In some embodiments, 30 ⁇ X/b ⁇ 50. In some embodiments, X/b is 0.5, 1, 5, 10, 20, 50, 80, 100, 120, 150, 180, 200, or within a range of any two of the above.
  • Lithium difluorophosphate LiPO 2 F 2
  • the content of the lithium difluorophosphate is 0.01% to 1.5% based on the weight of the electrolyte. In some embodiments, the content of the lithium difluorophosphate is 0.05% to 1.2% based on the weight of the electrolyte. In some embodiments, the content of the lithium difluorophosphate is 0.1% to 1.0% based on the weight of the electrolyte. In some embodiments, the content of the lithium difluorophosphate is 0.5% to 0.8% based on the weight of the electrolyte.
  • the content of the lithium difluorophosphate is 0.01%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.8%, 1%, 1.5% or within a range of any two of the above.
  • the compound of formula 1 includes at least one of the following compounds:
  • the content of the compound of Formula 1 ranges from 0.01% to 5% based on the weight of the electrolyte. In some embodiments, the content of the compound of Formula 1 ranges from 0.05% to 4% based on the weight of the electrolyte. In some embodiments, the content of the compound of Formula 1 ranges from 0.1% to 3% based on the weight of the electrolyte. In some embodiments, the content of the compound of Formula 1 ranges from 0.5% to 2% based on the weight of the electrolyte. In some embodiments, the content of the compound of Formula 1 ranges from 1% to 1.5% based on the weight of the electrolyte.
  • the content of the compound of formula 1 is 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5% or at within the range of any two of the above values.
  • the content of the compound of formula 1 in the electrolyte is within the above range, the high temperature storage performance and overcharge resistance of the electrochemical device can be further improved.
  • the electrolyte further comprises any non-aqueous solvent known in the art as a solvent for the electrolyte.
  • 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 carbonate Ethers, chain ethers, phosphorus-containing organic solvents, sulfur-containing organic solvents and aromatic fluorine-containing 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 n-propyl carbonate, ethyl-n-propyl carbonate, di-n-propyl carbonate and other chain carbonates, etc.
  • fluorine-substituted chain carbonates 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 gamma-butyrolactone and gamma-valerolactone.
  • some of the hydrogen atoms of the cyclic carboxylate may be replaced by fluorine.
  • examples of the chain carboxylates 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, methyl isobutyrate, ethyl isobutyrate, methyl valerate, ethyl valerate, methyl pivalate and ethyl pivalate, etc.
  • some of the hydrogen atoms of the chain carboxylate may be replaced by fluorine.
  • examples of fluorine-substituted chain carboxylates 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, 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 and the like.
  • 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, dimethysulfone 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 of the hydrogen atoms of the sulfur-containing organic solvent may be replaced by fluorine.
  • the aromatic fluorine-containing solvent includes, but is not limited to, one or more of the following: fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene and trifluoromethylbenzene.
  • the solvents used in the electrolytes of the present application include 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, propionic acid Propyl ester, n-propyl acetate, ethyl acetate, and combinations thereof.
  • the solvent used in the electrolyte of the present application comprises: ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, ⁇ -butyrolactone and combinations thereof .
  • examples of the additives may include, but are not limited to, one or more of the following: fluorocarbonates, ethylene carbonate containing carbon-carbon double bonds, compounds containing sulfur-oxygen double bonds, and acid anhydrides .
  • the additive is present in an amount of 0.01% to 15%, 0.1% to 10%, or 1% to 5% based on the weight of the electrolyte.
  • the content of the propionate is 1.5 to 30 times, 1.5 to 20 times, 2 to 20 times, or 5 to 20 times that of the additive based on the weight of the electrolyte.
  • the additive comprises one or more ethylene carbonates containing carbon-carbon double bonds.
  • the carbon-carbon double bond-containing vinyl carbonate may include, but are not limited to, one or more of the following: vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, carbonic acid-1 ,2-Dimethyl vinylene carbonate, 1,2-diethyl vinylene carbonate, fluorovinylene carbonate, trifluoromethyl vinylene carbonate; vinyl ethylene carbonate, 1-methyl carbonate Ethyl-2-vinylethylene carbonate, 1-ethyl-2-vinylethylene carbonate, 1-n-propyl-2-vinylethylene carbonate, 1-methyl-2-ethylene carbonate Ethylene carbonate, 1,1-divinylethylene carbonate, 1,2-divinylethylene carbonate, 1,1-dimethyl-2-methylene carbonate and 1,1-diethyl-2-methylene ethylene carbonate, etc.
  • the carbon-carbon double bond may include, but are not limited to
  • the additive is a combination of a fluorocarbonate and a carbon-carbon double bond-containing ethylene carbonate. In some embodiments, the additive is a combination of a fluorocarbonate and a compound containing a sulfur-oxygen double bond. In some embodiments, the additive is a combination of a fluorocarbonate and a compound having 2-4 cyano groups. In some embodiments, the additive is a combination of a fluorocarbonate and a cyclic carboxylate. In some embodiments, the additive is a combination of fluorocarbonate and cyclic phosphoric anhydride. In some embodiments, the additive is a combination of a fluorocarbonate and a carboxylic acid anhydride. In some embodiments, the additive is a combination of fluorocarbonate and fluorine anhydride. In some embodiments, the additive is a combination of a fluorocarbonate and a carboxylic acid anhydride.
  • the electrolyte is not particularly limited, and any known electrolyte can be used.
  • 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 Lithium sulf
  • Methylated lithium salts such as LiC (C 2 F 5 SO 2 ) 3 ; bis(malonate) lithium borate, difluoro(malonate) lithium borate, etc. (malonate) boric acid Lithium salts; (malonate) lithium phosphate salts such as lithium tris(malonate) phosphate, lithium difluorobis(malonate) phosphate, lithium tetrafluoro(malonate) phosphate; and LiPF 4 ( CF3 ) 2 , LiPF4 ( C2F5 ) 2 , LiPF4 ( CF3SO2 ) 2 , LiPF4 ( C2F5SO2 ) 2 , LiBF3CF3 , LiBF3C2F5 , LiBF 3 C 3 F 7 , LiBF 2 (CF 3 ) 2 , LiBF 2 (C 2 F 5 ) 2 , LiBF 2 (CF 3 SO 2 ) 2 , LiBF 2 (C 2 F 5 SO 2 ) 2 and other fluor
  • 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 , Lithium Cyclic 1,2-Perfluoroethane Bissulfonimide, Lithium Cyclic 1,3-Perfluoropropane Bissulfonimide, 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 and 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 effects of the present application are 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 a range consisting of any two of the above-mentioned values. When the electrolyte concentration is within the above-mentioned range, the amount of lithium as the charged particles is not too small, and the viscosity can be kept in an appropriate range, so that 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 amount of 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 weight of the electrolyte.
  • the amount of salt selected from the group consisting of monofluorophosphates, borates, oxalates, and fluorosulfonates is less than 20% or less than 10% based on the weight of the electrolyte. In some embodiments, the amount of salt selected from the group consisting of monofluorophosphates, borates, oxalates, and fluorosulfonates is within a range consisting of any two of the foregoing values.
  • the electrolyte comprises one or more species selected from the group consisting of monofluorophosphates, borates, oxalates, and fluorosulfonates, and one or more salts in addition thereto.
  • Other salts include the lithium salts exemplified above, and 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-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 .
  • the other salts include the lithium salt
  • the additional salt is present in an amount greater than 0.01% or greater than 0.1% based on the weight of the electrolyte. In some embodiments, the amount of additional salt is less than 20%, less than 15%, or less than 10% based on the weight of the electrolyte. In some embodiments, the content of other salts is within the range composed of any two of the above-mentioned values. The other salts having the above-mentioned contents help to balance the conductivity and viscosity of the electrolyte.
  • the electrolytic solution may contain additional additives such as a negative electrode coating film forming agent, a positive electrode protective agent, and an overcharge inhibitor as necessary.
  • additives generally used in non-aqueous electrolyte secondary batteries can be used, and examples thereof can include, but are not limited to, vinylene carbonate, succinic anhydride, biphenyl, cyclohexylbenzene, 2,4-difluorobenzyl Ether, propane sultone, propene sultone, etc. These additives may be used alone or in any combination.
  • the content of these additives in the electrolytic solution is not particularly limited, and may be appropriately set according to the type and the like of the additives.
  • the additive is present in an amount of less than 5%, in the range of 0.01% to 5%, or in the range of 0.2% to 5%, based on the weight of the electrolyte.
  • the positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on one or both surfaces of the positive electrode current collector.
  • the positive electrode active material layer contains a positive electrode active material.
  • the positive electrode active material layer may be one or more layers. Each of the multilayered positive active materials may contain the same or different positive active materials.
  • the positive active material is any material that can reversibly intercalate and deintercalate metal ions such as lithium ions.
  • the type of the positive electrode active material is not particularly limited as long as it can electrochemically occlude and release metal ions (eg, lithium ions).
  • the positive active material is a material containing lithium and at least one transition metal.
  • the positive electrode active material may include, but are not limited to, lithium transition metal composite oxides and lithium-containing transition metal phosphate compounds.
  • the transition metal in the lithium transition metal composite oxide includes V, Ti, Cr, Mn, Fe, Co, Ni, Cu, and the like.
  • the 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 , etc., LiNi 1/3 Mn 1/3 Co 1/3 O 2 , LiNi 0.5 Mn 0.3 Co 0.2 O 2 and other lithium-nickel-manganese-cobalt composite oxides, in which a part of the transition metal atoms serving as the host of these lithium transition metal composite oxides are 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 .
  • lithium transition metal composite oxide 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 and so on.
  • combinations of lithium transition metal composite oxides include, but are not limited to, combinations of LiCoO 2 and LiMn 2 O 4 , wherein a portion of Mn in LiMn 2 O 4 may be replaced by transition metals (eg, LiNi 0.33 Co 0.33 Mn 0.33 O 2 ), a part of Co in LiCoO 2 can be replaced by transition metals.
  • the transition metal in the lithium-containing transition metal phosphate compound includes V, Ti, Cr, Mn, Fe, Co, Ni, Cu, and the like.
  • the lithium-containing transition metal phosphate compounds include LiFePO 4 , Li 3 Fe 2 (PO 4 ) 3 , LiFeP 2 O 7 and other iron phosphates, and LiCoPO 4 and other cobalt phosphates, wherein as these lithium transition metal phosphate compounds A part of the transition metal atoms of the host is replaced by Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si and other elements.
  • 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 active material and lithium phosphate are used in combination.
  • the content of lithium phosphate is greater than 0.1%, greater than 0.3%, or greater than 0.5% relative to the weight of the positive electrode active material and lithium phosphate.
  • the content of lithium phosphate is less than 10%, less than 8%, or less than 5% relative to the weight of the positive electrode active material and lithium phosphate.
  • the content of lithium phosphate is within the range composed of any two values above.
  • a substance having a different composition may be attached to the surface of the above-mentioned positive electrode active material.
  • surface-attached 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-adhering substances can be attached to the surface of the positive electrode active material by the following methods: dissolving or suspending the surface-adhering substances in a solvent, infiltrating and adding to the positive-electrode active material, and drying; dissolving or suspending the surface-adhering substance precursors In a solvent, after being infiltrated into the positive electrode active material, and then reacted by heating or the like; and a method of adding it to a positive electrode active material precursor while firing, and the like.
  • attaching carbon a method of mechanically attaching a carbon material (eg, activated carbon, etc.) can also be used.
  • the content of the surface-attached substance is greater than 0.1 ppm, greater than 1 ppm, or greater than 10 ppm based on the weight of the positive electrode active material layer. In some embodiments, the content of the surface-attached material is less than 10%, less than 5%, or less than 2% based on the weight of the positive electrode active material layer. In some embodiments, based on the weight of the positive electrode active material layer, the content of the surface-attached material is within a range composed of any two of the above-mentioned values.
  • 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 exhibited; when the amount of the surface-attached substance is too large, the ingress and egress of lithium ions are hindered, and thus the resistance may increase.
  • a positive electrode active material having a substance different in composition adhered to the surface of the positive electrode active material is also referred to as a "positive electrode active material”.
  • the shapes of the positive electrode active material particles include, but are not limited to, block, polyhedron, spherical, elliptical spherical, plate, needle, column, 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 amount of the dispersion medium required for the formation of the positive electrode active material layer and the required amounts of the conductive material and the positive electrode binder can be suppressed, whereby the filling of the positive electrode active material can be ensured rate and capacity of electrochemical devices.
  • a high-density positive electrode active material layer can be formed by using a composite oxide powder having a high tap density. Generally, the larger the tap density, the more preferable, 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, the reduction in load characteristics can be suppressed.
  • the tap density of the positive electrode active material can be calculated in the following way: put 5g to 10g of positive electrode active material powder into a 10mL glass graduated cylinder, and perform 200 strokes of 20mm vibration to obtain the powder filling 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 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 particle size (D50) of the positive 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 a range composed of any two of the above-mentioned values.
  • the median particle diameter (D50) of the positive electrode active material particles is within the above range, a positive electrode active material with a high tap density can be obtained, and the reduction in the performance of the electrochemical device can be suppressed.
  • the production process of the positive electrode of the electrochemical device that is, when the positive electrode active material, conductive material, binder, etc. are slurried with a solvent and applied in a thin film
  • problems such as occurrence of streaks can be prevented.
  • by mixing two or more kinds of positive electrode active materials having different median particle diameters it is possible to further improve the filling property at the time of positive electrode preparation.
  • the median diameter (D50) of the positive electrode active material particles can be measured by a laser diffraction/scattering particle size distribution analyzer: when using LA-920 manufactured by HORIBA as a particle size distribution meter, a 0.1% sodium hexametaphosphate aqueous solution is used as the particle size distribution meter.
  • the dispersion medium used in the measurement was measured with the measurement refractive index set to 1.24 after ultrasonic dispersion for 5 minutes.
  • the average primary particle size of the positive electrode active material is greater than 0.05 ⁇ m, greater than 0.1 ⁇ m, or greater than 0.5 ⁇ m. In some embodiments, the average primary particle size of the positive active material is less than 5 ⁇ m, less than 4 ⁇ m, less than 3 ⁇ m, or less than 2 ⁇ m. In some embodiments, the average primary particle size of the positive electrode active material is within the range composed of any two values above.
  • the average primary particle size of the positive electrode active material is within the above-mentioned range, the powder filling property and specific surface area can be ensured, the deterioration of battery performance can be suppressed, and moderate crystallinity can be obtained, thereby ensuring the reversibility of charge and discharge of the electrochemical device. .
  • the average primary particle size of the positive electrode active material can be obtained by observing an image obtained by a scanning electron microscope (SEM): in an SEM image with a magnification of 10,000 times, for any 50 primary particles, the relative value in the horizontal direction is calculated. The longest value of the slice obtained by the left and right boundary lines of the straight primary particles was obtained, and the average value was obtained to obtain the average primary particle diameter.
  • SEM scanning electron microscope
  • the specific surface area (BET) of the positive active material is greater than 0.1 m 2 /g, greater than 0.2 m 2 /g, or greater than 0.3 m 2 /g. In some embodiments, the specific surface area (BET) of the positive active material is less than 50 m 2 /g, less than 40 m 2 /g, or less than 30 m 2 /g. In some embodiments, the specific surface area (BET) of the positive active material is within a range composed of any two of the above-mentioned values. When the specific surface area (BET) of the positive electrode active material is within the above range, the performance of the electrochemical device can be ensured, and at the same time, the positive electrode active material can have good coatability.
  • the specific surface area (BET) of the positive active material can be measured by pre-drying the sample at 150°C for 30 minutes under nitrogen flow using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken), and then The nitrogen-helium mixed gas whose relative pressure value of nitrogen gas to atmospheric pressure was accurately adjusted to 0.3 was used for the measurement by the nitrogen adsorption BET single-point method using the gas flow method.
  • a surface area meter for example, a fully automatic surface area measuring device manufactured by Okura Riken
  • the kind of the positive electrode conductive material is not limited, and any known conductive material can be used.
  • the positive electrode conductive material may include, but are not limited to, graphite such as natural graphite, artificial graphite; carbon black such as acetylene black; carbon materials such as amorphous carbon such as needle coke; carbon nanotubes; graphene, and the like.
  • the above-mentioned positive electrode conductive materials may be used alone or in any combination.
  • the content of the positive electrode conductive material is greater than 0.01%, greater than 0.1%, or greater than 1% based on the weight of the positive electrode active material layer. In some embodiments, the content of the positive electrode conductive material is less than 10%, less than 8% or less, or less than 5% based on the weight of the positive electrode active material layer. When the content of the positive electrode conductive material is within the above range, sufficient conductivity and capacity of the electrochemical device can be ensured.
  • the type of the positive electrode binder used in the production of the positive electrode active material layer is not particularly limited, and in the case of the coating method, any material that can be dissolved or dispersed in the liquid medium used in the production of the electrode may be used.
  • positive binders may include, but are not limited to, one or more of the following: polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, Aromatic polyamide, cellulose, nitrocellulose and other resin-based polymers; styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), fluororubber, isoprene rubber, polybutadiene rubber, ethylene-propylene rubber and other rubbers styrene-butadiene-styrene block copolymer or its hydrogenated product, ethylene-propylene-diene terpolymer (EPDM), styrene-ethylene-butadiene-ethylene copolymer,
  • the content of the positive electrode binder is greater than 0.1%, greater than 1%, or greater than 1.5% based on the weight of the positive electrode active material layer. In some embodiments, the content of the positive electrode binder is less than 10%, less than 5%, less than 4%, or less than 3% based on the weight of the positive electrode active material layer. When the content of the positive electrode binder is within the above range, the positive electrode can have good electrical conductivity and sufficient mechanical strength, and ensure the capacity of the electrochemical device.
  • the kind of the solvent used to form the positive electrode slurry is not limited as long as it is a solvent capable of dissolving or dispersing the positive electrode active material, the conductive material, the positive electrode binder, and the thickener used as necessary.
  • the solvent used to form the positive electrode slurry may include any one of an aqueous solvent and an organic solvent.
  • the aqueous medium may include, but are not limited to, water, a mixed medium of alcohol and water, and the like.
  • Examples of the organic medium may include, but are not limited to, aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as methyl ketone and cyclohexanone; esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N,N-dimethylaminopropylamine; diethyl ether, propylene oxide, tetrahydrofuran (THF) ) and other ethers; N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide and other amides; hexamethylphosphoramide, dimethyl sulfoxide and other aprotic polar solvents, etc.
  • aliphatic hydrocarbons such as hexane
  • aromatic hydrocarbons such as benzene, toluen
  • Thickeners are usually used to adjust the viscosity of the slurry.
  • a thickener and a styrene-butadiene rubber (SBR) emulsion can be used for slurrying.
  • SBR styrene-butadiene rubber
  • the kind of thickener is not particularly limited, and examples thereof may include, but are not limited to, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch , casein and their salts, etc.
  • the above-mentioned thickeners may be used alone or in any combination.
  • the content of the thickener is greater than 0.1%, greater than 0.2%, or greater than 0.3% based on the weight of the positive active material layer. In some embodiments, the content of the thickener is less than 5%, less than 3%, or less than 2% based on the weight of the positive active material layer. In some embodiments, based on the weight of the positive electrode active material layer, the content of the thickener is within a range composed of any two of the above-mentioned values. When the content of the thickener is within the above range, the positive electrode slurry can have good coatability, and at the same time, the capacity reduction and resistance increase of the electrochemical device can be suppressed.
  • the content of the positive active material is greater than 80%, greater than 82%, or greater than 84% based on the weight of the positive electrode active material layer. In some embodiments, the content of the positive active material is less than 99% or less than 98% based on the weight of the positive active material layer. In some embodiments, based on the weight of the positive electrode active material layer, the content of the positive electrode active material is within the range formed by any two of the foregoing arrays. When the content of the positive electrode active material is within the above range, the electric capacity of the positive electrode active material in the positive electrode active material layer can be secured while maintaining the strength of the positive electrode.
  • a pressing process may be performed by a manual press, a roll press, or the like.
  • the density of the positive active material layer is greater than 1.5 g/cm 3 , greater than 2 g/cm 3 , or greater than 2.2 g/cm 3 .
  • the density of the positive active material layer is less than 5 g/cm 3 , less than 4.5 g/cm 3 , or less than 4 g/cm 3 .
  • the density of the positive active material layer is within a range composed of any two of the above-mentioned values. When the density of the positive electrode active material layer is within the above-mentioned range, the electrochemical device can have good charge-discharge characteristics while suppressing an increase in resistance.
  • the thickness of the positive electrode active material layer is the thickness of the positive electrode active material layer
  • the thickness of the positive electrode active material layer refers to the thickness of the positive electrode active material layer on either side of the positive electrode current collector. In some embodiments, the thickness of the positive active material layer is greater than 10 ⁇ m or greater than 20 ⁇ m. In some embodiments, the thickness of the positive active material layer is less than 500 ⁇ m or less than 450 ⁇ m.
  • the positive electrode active material can be produced using a conventional method for producing inorganic compounds.
  • the following production method can be used: the raw material of the transition metal is dissolved or pulverized and dispersed in a solvent such as water, the pH is adjusted while stirring, a spherical precursor is produced and recovered, and if necessary, the After drying, Li sources such as LiOH, Li 2 CO 3 , and LiNO 3 are added and fired at high temperature to obtain a positive electrode active material.
  • the type of the positive electrode current collector is not particularly limited, and it may be any known material suitable for use as a positive electrode current collector.
  • positive electrode current collectors may include, but are not limited to, metal materials such as aluminum, stainless steel, nickel plating, titanium, tantalum, and the like; carbon materials such as carbon cloth, carbon paper, and the like.
  • the positive electrode current collector is a metallic material.
  • the positive current collector is aluminum.
  • the form of the positive electrode current collector is not particularly limited.
  • the form of the positive electrode current collector may include, but is not limited to, metal foil, metal cylinder, metal coil, metal plate, metal foil, metal expanded mesh, stamped metal, foamed metal, and the like.
  • the positive electrode current collector is a carbon material
  • the form of the positive electrode current collector may include, but is not limited to, carbon plates, carbon films, carbon cylinders, and the like.
  • the positive current collector is a metal foil.
  • the metal foil is in the form of a mesh. The thickness of the metal foil is not particularly limited.
  • the thickness of the metal foil is greater than 1 ⁇ m, greater than 3 ⁇ m, or greater than 5 ⁇ m. In some embodiments, the thickness of the metal foil is less than 1 mm, less than 100 ⁇ m, or less than 50 ⁇ m. In some embodiments, the thickness of the metal foil is within a range composed of any two of the above-mentioned values.
  • the surface of the positive electrode current collector may include a conductive aid.
  • conductive aids may include, but are not limited to, carbon and noble metals such as gold, platinum, and silver.
  • the thickness ratio of the positive electrode active material layer to the positive electrode current collector means the thickness of the positive electrode active material layer on one side divided by the thickness of the positive electrode current collector, and its value is not particularly limited. In some embodiments, the thickness ratio is less than 50, less than 30, or less than 20. In some embodiments, the thickness ratio is greater than 0.5, greater than 0.8, or greater than 1. In some embodiments, the thickness ratio is within a range consisting of any two of the foregoing values. When the thickness ratio is within the above range, the heat generation of the positive electrode current collector can be suppressed during charging and discharging at a high current density, and the capacity of the electrochemical device can be secured.
  • the positive electrode can be produced by forming a positive electrode active material layer containing a positive electrode active material and a binder on a current collector.
  • the production of the positive electrode using the positive electrode active material can be carried out by a conventional method, that is, dry mixing the positive electrode active material and a binder, and, if necessary, a conductive material and a thickening agent, etc., to form a sheet, and the obtained
  • the sheet is crimped onto the positive electrode current collector; or these materials are dissolved or dispersed in a liquid medium to make a slurry, and the slurry is applied to the positive electrode current collector and dried to form on the current collector.
  • a positive electrode active material layer whereby a positive 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 effects of the present application are not significantly impaired.
  • the separator may be resin, glass fiber, inorganic matter, etc. formed of a material that is stable to the electrolyte of the present application.
  • the separator includes a porous sheet with excellent liquid retention properties, a non-woven fabric-like substance, or the like.
  • Examples of materials for the resin or fiberglass separator may include, but are not limited to, polyolefins, aramids, polytetrafluoroethylene, polyethersulfone, and the like.
  • the polyolefin is polyethylene or polypropylene.
  • the polyolefin is polypropylene.
  • the materials of the above-mentioned separators may be used alone or in any combination.
  • the separator can also be a material formed by laminating the above materials, examples of which include, but are not limited to, a three-layer separator formed by laminating polypropylene, polyethylene, and polypropylene in the order.
  • inorganic materials may include, but are not limited to, oxides such as alumina and silica, nitrides such as aluminum nitride and silicon nitride, sulfates (eg, barium sulfate, calcium sulfate, etc.).
  • inorganic forms may include, but are not limited to, particulate or fibrous.
  • the form of the separator may be a film form, examples of which include, but are not limited to, non-woven fabrics, woven fabrics, microporous membranes, and the like.
  • the separator has a pore size of 0.01 ⁇ m to 1 ⁇ m and a thickness of 5 ⁇ m to 50 ⁇ m.
  • a separator formed by forming a composite porous layer containing the above-mentioned inorganic particles on the surface of the positive electrode and/or the negative electrode using a resin-based binder can also be used,
  • a separator is formed by using a fluororesin as a binder to form a porous layer on both surfaces of a positive electrode with alumina particles having a particle size of less than 90% of 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 isolation membrane has a thickness of less than 50 ⁇ m, less than 40 ⁇ m, or less than 30 ⁇ m. In some embodiments, the thickness of the isolation film is within a range consisting of any two of the above-mentioned values. When the thickness of the separator is within the above range, insulating properties 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 isolation membrane has a porosity of less than 60%, less than 50%, or less than 45%.
  • the porosity of the separator is within a range consisting of any two of the above-mentioned values. 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.
  • the separator has an average pore size of less than 0.5 ⁇ m or less than 0.2 ⁇ m. In some embodiments, the separator has an average pore size greater than 0.05 ⁇ m. In some embodiments, the average pore size of the isolation membrane is in the range composed of any two of the above-mentioned values. When the average pore diameter of the separator exceeds the above-mentioned range, a short circuit is likely to occur. When the average pore diameter of the separator is within the above range, the electrochemical device has good safety characteristics.
  • the electrochemical device assembly includes an electrode group, a current collecting structure, an outer casing, and a protective element.
  • the electrode group may have any of a laminated structure in which the positive electrode and the negative electrode are laminated with the separator interposed therebetween, and a structure in which the positive electrode and the negative electrode are wound in a spiral shape with the separator interposed therebetween.
  • the proportion 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 rate of the electrode group is within a range composed of any two of the above-mentioned values.
  • the electrode group occupancy ratio is within the above-mentioned range, the capacity of the electrochemical device can be ensured, and at the same time, the deterioration of characteristics such as repeated charge and discharge performance and high temperature storage associated with 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-described laminated structure, a structure in which the metal core portions of the respective electrode layers are bundled and welded to the terminals is suitably used.
  • the electrode area of one sheet increases, the internal resistance increases. Therefore, it is also suitable to provide two or more terminals in the electrode to reduce the resistance.
  • the electrode group has the above-described winding structure, the internal resistance can be reduced by providing two or more lead structures for the positive electrode and the negative electrode, respectively, and bundling them on the terminals.
  • the material of the outer casing is not particularly limited as long as it is stable to the electrolyte solution used.
  • the outer casing can be used, but not limited to, nickel-plated steel sheet, stainless steel, metal such as aluminum or aluminum alloy, magnesium alloy, or a laminated film of resin and aluminum foil.
  • the outer casing is a metal or laminated film of aluminum or aluminum alloy.
  • Metal-based outer casings include, but are not limited to, a hermetically sealed structure formed by welding metals to each other by laser welding, resistance welding, or ultrasonic welding, or a riveted structure using the above-mentioned metals through a resin gasket.
  • the outer casing using the above-mentioned laminated film includes, but is not limited to, a hermetically sealed structure formed by thermally adhering resin layers to each other, and the like. In order to improve the sealing property, a resin different from the resin used for 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 a resin to be sandwiched due to the bonding of the metal and the resin.
  • the shape of the exterior body is also arbitrary, and may be any of a cylindrical shape, a square shape, a laminated type, a button type, a large size, and the like, for example.
  • the protective element can use a positive temperature coefficient (PTC), a thermal fuse, a thermistor, whose resistance increases when abnormal heat is generated or an excessive current flows, and can be cut off by rapidly increasing the internal pressure or internal temperature of the battery when abnormal heat is generated A valve (current cutoff valve), etc. for the current flowing in the circuit.
  • PTC positive temperature coefficient
  • the above-mentioned protective element can be selected to be in a condition that does not work in the normal use of high current, and can also be designed in a form that does not cause abnormal heat release or thermal runaway even if there is no protective element.
  • the electrochemical device of the present application includes any device in which an electrochemical reaction occurs, and specific examples thereof include all kinds of primary batteries, 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 comprising the electrochemical device according to the present 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 art.
  • the electrochemical devices of the present application may be used in, but not limited to, notebook computers, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, headsets stereo headphones, VCRs, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power, motors, cars, motorcycles, power Bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.
  • lithium ion batteries The preparation of lithium ion batteries is described below by taking lithium ion batteries as an example and in conjunction with specific embodiments. Those skilled in the art will understand that the preparation methods described in this application are only examples, and any other suitable preparation methods are included in the scope of this application. within the range.
  • the artificial graphite, rubber and sodium carboxymethyl cellulose are mixed with deionized water in a mass ratio of 96%:2%:2%, and stirred evenly to obtain a negative electrode slurry.
  • the negative electrode slurry was coated on a 12 ⁇ m current collector. After drying, cold pressing, cutting and welding the tabs, the negative electrode is obtained.
  • Styrene Butadiene Rubber SBR 2 Acrylate SBR copolymer 3 Styrene Acrylate Copolymer 4 Chlorotrifluoroethylene-styrene butadiene rubber blend 5 HFP (hexafluoropropylene) styrene butadiene rubber blend
  • Lithium cobalt oxide (LiCoO 2 ), conductive material (Super-P) and polyvinylidene fluoride (PVDF) were mixed with N-methylpyrrolidone (NMP) in a mass ratio of 95%:2%:3%, and stirred evenly, A positive electrode slurry was obtained.
  • the positive electrode slurry was coated on a 12 ⁇ m aluminum foil, dried, cold pressed, and then cut into pieces and welded with tabs to obtain a positive electrode.
  • a polyethylene (PE) porous polymer film was used as the separator.
  • the obtained positive electrode, separator and negative electrode were wound in order and placed in an outer packaging foil, leaving a liquid injection port.
  • the electrolyte is poured from the liquid injection port, packaged, and then the lithium ion battery is prepared through processes such as chemical formation and capacity.
  • the lithium-ion battery was allowed to stand for 30 minutes, then charged to 4.45V at a constant current rate of 0.5C, and then charged to 0.05C at a constant voltage of 4.45V, and stood for 5 minutes to measure the thickness of the lithium-ion battery.
  • the thickness of the lithium-ion battery was measured again after 21 days of storage at 60°C.
  • the high-temperature storage expansion rate of lithium-ion batteries is calculated by the following formula:
  • High-temperature storage expansion ratio [(thickness after storage ⁇ thickness before storage)/thickness before storage] ⁇ 100%.
  • Overcharge deformation rate [(T2-T1)/T1] ⁇ 100%.
  • Table 1 shows the bonding strength between anode active materials and the effect of propionate in the electrolyte on the high-temperature storage expansion rate and overcharge deformation rate of lithium-ion batteries.
  • the results show that when the bonding strength between the negative electrode active materials is 100 N/cm 2 to 500 N/cm 2 and the electrolyte includes propionate, the negative electrode expansion/contraction caused by the charging and discharging process can be suppressed, and the negative electrode mixture layer and the electrolyte can be stabilized.
  • the interface between liquid and liquid can significantly reduce the high-temperature storage expansion rate and overcharge deformation rate of lithium-ion batteries.
  • Table 2 shows the effect of the specific surface area of the negative mixture layer on the high temperature storage expansion rate and overcharge deformation rate of the lithium ion battery performance.
  • Examples 2-1 to 2-6 differ from Example 1-1 or Example 1-5 only in the parameters listed in Table 2.
  • Table 3 shows the effect of trace metals in the anode active material on the high-temperature storage expansion rate and overcharge deformation rate of lithium-ion batteries. Examples 3-1 to 3-8 differ from Example 1-1 only in the parameters listed in Table 3.
  • Table 4 shows the effect of electrolyte composition on the high-temperature storage expansion rate and overcharge deformation rate of Li-ion batteries. Examples 4-1 to 4-31 differ from Example 1-1 only in the parameters listed in Table 4.
  • the results show that, on the basis that the bonding strength between the negative active materials is 100 N/cm 2 to 500 N/cm 2 and the electrolyte includes propionate, when the electrolyte further contains fluorocarbonate, organic When the compound, lithium difluorophosphate and/or the compound of formula 1 are used, the high temperature storage expansion rate and the overcharge deformation rate of the lithium ion battery can be further reduced.
  • Table 5 shows the effect of the relationship between the content of propionate in the electrolyte, X%, and the organic compound having a cyano group, b%, on the high-temperature storage expansion rate and overcharge deformation rate of lithium-ion batteries.
  • Examples 5-1 to 5-8 differ from Example 1-1 or Example 4-3 only in the parameters listed in Table 5.

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Abstract

一种电化学装置和电子装置。电化学装置包括正极、负极和电解液，负极包括负极集流体和形成在负极集流体上的负极合剂层，负极合剂层包括负极活性物质，其中负极活性物质之间具有特定的粘接强度且电解液包括丙酸酯。电化学装置具有改进的高温存储性能和抗过充性能。

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，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不断发展，电化学装置(例如，锂离子电池)的用途得到了极大的扩展，其已经成为主流电子产品的储能设备。随着需求的增加，人们对锂离子电池的性能要求也进一步提高，生产工艺也得到了不断优化。
由于原材料种类繁多且性能各有优缺点，在使用时通常采用多种原材料配合的方式。然而，不同材料之间在配料过程有可能出现匹配性差的问题，由此会造成电池性能下降。
有鉴于此，确有必要提供一种具有改进的性能的电化学装置和电子装置。
发明内容
本申请实施例通过提供一种具有改进的高温存储性能和抗过充性能的电化学装置和电子装置以在至少某种程度上解决至少一种存在于相关领域中的问题。
在本申请的一方面，本申请提供一种电化学装置，其包括正极、负极和电解液，所述负极包括负极集流体和形成在所述负极集流体上的负极合剂层，所述负极合剂层包括负极活性物质，其中：所述负极活性物质之间的粘接强度为F N/cm 2，F在100至500的范围内；所述电解液包括丙酸酯。
根据本申请的实施例，所述负极合剂层包括橡胶，所述橡胶包括丁苯橡胶、异戊二烯橡胶、丁二烯橡胶、氟橡胶、丙烯腈-丁二烯橡胶、苯乙烯-丙烯橡胶中的至少一种。
根据本申请的实施例，所述橡胶进一步包括丙烯酸官能团、氯三氟乙烯官能团或六氟丙烯官能团中的至少一种。
根据本申请的实施例，基于所述电解液的重量，所述丙酸酯的含量为X％，X在5至65的范围内。
根据本申请的实施例，F与X满足：1.6≤F/X≤100。
根据本申请的实施例，所述负极合剂层的比表面积为A m 2/g，A在2至5的范围内。
根据本申请的实施例，F与A满足：20≤F/A≤250。
根据本申请的实施例，所述负极活性物质具有以下特征中的至少一者：
(a)具有5μm至30μm的中值粒径；
(b)包括人造石墨、天然石墨、中间相碳微球、软碳、硬碳、无定形碳、含硅材料、含锡材料、合金材料中的至少一种；
(c)包括金属，所述金属包括钼、铁或铜中的至少一种，并且基于所述负极合剂层的重量，所述金属的含量为0.05％以下。
根据本申请的实施例，所述电解液进一步包括以下化合物中的至少一种：
i)氟代碳酸酯；
ii)具有氰基的化合物；
iii)二氟磷酸锂；
iv)式1化合物：
Figure PCTCN2020121179-appb-000001
其中：
R 1、R 2、R 3、R 4、R 5和R 6各自独立地为氢或C 1-C 10烷基；
L 1和L 2各自独立地为-(CR 7R 8) n-；
R 7和R 8各自独立地为氢或C 1-C 10烷基；以及
n为1、2或3。
根据本申请的实施例，所述式1化合物包括以下化合物中的至少一种：
Figure PCTCN2020121179-appb-000002
Figure PCTCN2020121179-appb-000003
根据本申请的实施例，基于所述电解液的重量，所述式1化合物的含量在0.01％至5％的范围内。
根据本申请的实施例，基于所述电解液的重量，所述具有氰基的化合物的含量为b％，b在0.01至10的范围内。
根据本申请的实施例，X与b满足：0.5≤X/b≤200。
在本申请的另一方面，本申请提供一种电子装置，其包括根据本申请所述的电化学装置。
本申请实施例的额外层面及优点将部分地在后续说明中描述、显示、或是经由本申请实施例的实施而阐释。
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。
除非另外明确指明，本文使用的下述术语具有下文指出的含义。
在具体实施方式及权利要求书中，由术语“中的至少一者”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。术语“中的至少一种”具有与术语“中的至少一者”相同的含义。
如本文所使用，术语“烷基”预期是具有1至20个碳原子的直链饱和烃结构。“烷基”还预期是具有3至20个碳原子的支链或环状烃结构。当指定具有具体碳数的烷基时，预期涵盖具有该碳数的所有几何异构体；因此，例如，“丁基”意思是包括正丁基、仲丁基、异丁基、叔丁基和环丁基；“丙基”包括正丙基、异丙基和环丙基。烷基实例包括，但不限于甲基、乙基、正丙基、异丙基、环丙 基、正丁基、异丁基、仲丁基、叔丁基、环丁基、正戊基、异戊基、新戊基、环戊基、甲基环戊基、乙基环戊基、正己基、异己基、环己基、正庚基、辛基、环丙基、环丁基、降冰片基等。
如本文所使用，术语“卤代”指的是基团中的氢原子部分或全部被卤素原子(例如，氟、氯、溴或碘)取代。
随着电化学装置(例如，锂离子电池)的广泛应用，人们对其性能提出了越来越高的要求，尤其是安全性。当锂离子电池处于高温或过充条件下时，其内部易产生大量热量，当这些热量无法均匀地释放时，会导致锂离子电池的老化、膨胀、变形甚至爆炸的问题。
为了解决上述问题，本申请使用了具有特定粘接强度的负极活性物质和包括丙酸酯的电解液的组合，其能够防止负极在高温存储期间发生断裂，并可使电化学装置的容量充分导出，从而显著改善电化学装置的高温存储性能的抗过充性能。
在一个实施例中，本申请提供了一种电化学装置，其包括如下所述的正极、负极和电解液。
I、负极
负极包括负极集流体和设置在所述负极集流体的一个或两个表面上的负极合剂层。
1、负极合剂层
负极合剂层包含负极活性物质层，负极活性物质层包含负极活性物质。负极合剂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正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。
本申请的电化学装置的一个特征在于负极活性物质之间的粘接强度为F N/cm 2，F在100至500的范围内。在一些实施例中，F在150至450的范围内。在一些实施例中，F在200至400的范围内。在一些实施例中，F为100、150、200、250、300、350、400、450、500或在由上述任意两个数值所组成的范围内。当负极活性物质之间的粘接强度在上述范围内时，可显著改善电化学装置的高温存储性能和抗过充性能。
负极活性物质之间的粘接强度使表征负极活性物质的性质的参数之一，其可通过添加特定物质(例如，橡胶)或调控负极浆料配方、涂布工艺等来调整。
负极活性物质之间的粘接强度可通过以下方法测定：切取2cm×3cm的负极，从负极的一面上剥离负极合剂层，将负极的另一面的粘贴到已粘贴于玻璃板上的双面胶带(件号：No.515、日东电工株式会社制)上。然后，将负极集流体剥离，得到贴于双面胶带上的负极合剂层，作为待测试样。将待测试样的双面胶带侧安装到粘性试验机(商品名：TAC-II、株式会社RHESCA制)的测定头的前端(前端直径为0.2cm)。接着，在下述条件下将测定探针压入负极合剂层中拉离而进行剥离试验。在该剥离试验中，测定在负极活性物质间引起剥离的最大负载。将所得到的最大负载除以测定头的截面积(0.031cm 2)而得到的值记为负极活性物质间的粘接强度。
试验条件如下：
测定探针的压入速度为30mm/分钟；
测定探针的压入时间为10秒；
测定探针的压入负载为3.9N；
测定探针的拉离速度为600mm/分钟。
在一些实施例中，所述负极合剂层包括橡胶。橡胶能够有效地改善负极合剂层的界面稳定性，从而显著改善电化学装置的高温存储性能和抗过充性能。
在一些实施例中，所述橡胶包括丁苯橡胶、异戊二烯橡胶、丁二烯橡胶、氟橡胶、丙烯腈-丁二烯橡胶、苯乙烯-丙烯橡胶中的至少一种。
在一些实施例中，所述橡胶进一步包括丙烯酸官能团、氯三氟乙烯官能团或六氟丙烯官能团中的至少一种。
在一些实施例中，基于所述负极合剂层的重量，所述橡胶的含量为10％以下。在一些实施例中，基于所述负极合剂层的重量，所述橡胶的含量为8％以下。在一些实施例中，基于所述负极合剂层的重量，所述橡胶的含量为5％以下。在一些实施例中，基于所述负极合剂层的重量，所述橡胶的含量为3％以下。在一些实施例中，基于所述负极合剂层的重量，所述橡胶的含量为2％以下。
在一些实施例中，所述负极合剂层的比表面积为A m 2/g，A在2至5的范围内。在一些实施例中，A在3至4的范围内。在一些实施例中，A为2、2.5、3、3.5、4、4.5或在由上述任意两个数值所组成的范围内。当负极合剂层的比表面 积在上述范围内时，可以抑制锂在负极表面的析出并抑制负极与电解液反应所导致的气体产生，从而可进一步改善电化学装置的高温存储性能和抗过充性能。
负极合剂层的比表面积(BET)可通过如下方法测定：使用表面积计(大仓理研制造的全自动表面积测定装置)，在氮气流通下于350℃对试样进行15分钟预干燥，然后使用氮气相对于大气压的相对压力值准确调节为0.3的氮氦混合气体，通过采用气体流动法的氮吸附BET单点法进行测定。
在一些实施例中，负极活性物质之间的粘接强度F N/cm 2与负极合剂层的比表面积A m 2/g满足：20≤F/A≤250。在一些实施例中，30≤F/A≤240。在一些实施例中，50≤F/A≤200。在一些实施例中，60≤F/A≤150。在一些实施例中，F/A为20、30、40、50、60、70、80、90、100、110、120、125、150、180、200、240、250或在由上述任意两个数值所组成的范围内。当负极活性物质之间的粘接强度F N/cm 2与负极合剂层的比表面积A m 2/g满足上述关系时，可进一步改善电化学装置的高温存储性能和抗过充性能。
在一些实施例中，所述负极活性物质具有以下特征(a)-(c)中的至少一者：
(a)中值粒径(D50)
负极活性物质的中值粒径(D50)是指通过激光衍射/散射法得到的体积基准的平均粒径。
在一些实施例中，所述负极活性物质具有5μm至30μm的中值粒径。在一些实施例中，所述负极活性物质具有约10μm至约25μm的中值粒径。在一些实施例中，所述负极活性物质具有约15μm至约20μm的中值粒径。在一些实施例中，所述负极活性物质具有约1μm、约3μm、约5μm、约7μm、约10μm、约15μm、约20μm、约25μm、约30μm或在以上任意两个数值的范围内的中值粒径。当负极活性物质的中值粒径在上述范围内时，电化学装置的不可逆容量较小且易于均匀地涂布负极。
负极活性物质的中值粒径(D50)可通过如下方法测定：将负极活性物质分散于聚氧乙烯(20)山梨糖醇酐单月桂酸酯的0.2％水溶液(约10mL)中，利用激光衍射/散射式粒度分布计(堀场制作所社制造LA-700)进行测试。
(b)负极活性物质种类
在一些实施例中，所述负极活性物质包括人造石墨、天然石墨、中间相碳微 球、软碳、硬碳、无定形碳、含硅材料、含锡材料、合金材料中的至少一种；
在一些实施例中，所述负极活性物质的形状包括，但不限于，纤维状、球状、粒状和鳞片状。
在一些实施例中，基于学振法的X射线衍射图谱，所述负极活性物质的晶格面(002面)的层间距离在约0.335nm至约0.360nm的范围内、在约0.335nm至约0.350nm的范围内或在约0.335nm至约0.345nm的范围内。
在一些实施例中，基于学振法的X射线衍射图谱，所述负极活性物质的微晶尺寸(Lc)大于约1.0nm或大于约1.5nm。
在一些实施例中，所述负极活性物质的拉曼R值为大于约0.01、大于约0.03或大于约0.1。在一些实施例中，所述负极活性物质的拉曼R值为小于约1.5、小于约1.2、小于约1.0或小于约0.5。在一些实施例中，所述负极活性物质的拉曼R值在上述任意两个数值所组成的范围内。
所述负极活性物质在1580cm -1附近的拉曼半峰宽没有特别限制。在一些实施例中，所述负极活性物质在1580cm -1附近的拉曼半峰宽为大于约10cm -1或大于约15cm -1。在一些实施例中，所述负极活性物质在1580cm -1附近的拉曼半峰宽为小于约100cm -1、小于约80cm -1、小于约60cm -1或小于约40cm -1。在一些实施例中，所述负极活性物质在1580cm -1附近的拉曼半峰宽在上述任意两个数值所组成的范围内。
在一些实施例中，所述负极活性物质的长厚比为大于约1、大于约2或大于约3。在一些实施例中，所述负极活性物质的长厚比为小于约10、小于约8或小于约5。在一些实施例中，所述负极活性物质的长厚比在上述任意两个数值所组成的范围内。当负极活性物质的长厚比在上述范围内时，可进行更均匀的涂布。
(c)微量元素
在一些实施例中，所述负极活性物质包括金属，所述金属包括钼、铁或铜中的至少一种。这些金属元素可以与负极活性物质中一些导电能力差的有机物反应，从而有利于负极活性物质表面成膜。
在一些实施例中，上述金属元素以微量存在于所述负极合剂层中，以避免形成不导电的副产物并附着于负极的表面。在一些实施例中，基于所述负极合剂层的重量，所述金属的含量为0.05％以下。在一些实施例中，基于所述负极合剂层的重量，所述金属的含量为0.04％以下。在一些实施例中，基于所述负极合剂层 的重量，所述金属的含量为0.03％以下。在一些实施例中，基于所述负极合剂层的重量，所述金属的含量为0.01％以下。当负极合剂层中金属的含量在上述范围内时，可进一步改善电化学装置的高温存储性能和抗过充性能。
在一些实施例中，所述负极合剂层进一步包括含硅材料、含锡材料、合金材料中的至少一种。在一些实施例中，所述负极合剂层进一步包括含硅材料和含锡材料中的至少一种。在一些实施例中，所述负极合剂层进一步包括含硅材料、硅碳复合材料、硅氧材料、合金材料和含锂金属复合氧化物材料中的一种或多种。
在一些实施例中，所述负极合剂层进一步包含其它种类的负极活性物质，例如，一种或多种包含能够与锂形成合金的金属元素和准金属元素的材料。在一些实施例中，所述金属元素和准金属元素的实例包括，但不限于，Mg、B、Al、Ga、In、Si、Ge、Sn、Pb、Bi、Cd、Ag、Zn、Hf、Zr、Y、Pd和Pt。在一些实施例中，所述金属元素和准金属元素的实例包括Si、Sn或其组合。Si和Sn具有优异的脱嵌锂离子的能力，可为锂离子电池提供高能量密度。在一些实施例中，其它种类的负极活性物质还可以包括金属氧化物和高分子化合物中的一种或多种。在一些实施例中，所述金属氧化物包括，但不限于，氧化铁、氧化钌和氧化钼。在一些实施例中，所述高分子化合物包括，但不限于，聚乙炔、聚苯胺和聚吡咯。
负极导电材料
在一些实施例中，所述负极合剂层进一步包含负极导电材料，该导电材料可以包括任何导电材料，只要它不引起化学变化即可。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)、导电聚合物(例如，聚亚苯基衍生物)和它们的混合物。
负极粘合剂
在一些实施例中，所述负极合剂层还包括负极粘合剂。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。
负极粘合剂的实例包括，但不限于，聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯、聚甲基丙烯酸甲酯、芳香族聚酰胺、聚酰亚胺、纤维素、硝酸纤维素等树脂系高分子；丁苯橡胶(SBR)、异戊二烯橡胶、聚丁橡胶、氟橡胶、丙烯腈·丁二烯橡胶(NBR)、乙烯·丙烯橡胶等橡胶状高分子；苯乙烯·丁二烯·苯乙烯嵌段共 聚物或其氢化物；乙烯·丙烯·二烯三元共聚物(EPDM)、苯乙烯·乙烯·丁二烯·苯乙烯共聚物、苯乙烯·异戊二烯·苯乙烯嵌段共聚物或其氢化物等热塑性弹性体状高分子；间规-1,2-聚丁二烯、聚乙酸乙烯酯、乙烯·乙酸乙烯酯共聚物、丙烯·α-烯烃共聚物等软质树脂状高分子；聚偏二氟乙烯、聚四氟乙烯、氟化聚偏二氟乙烯、聚四氟乙烯·乙烯共聚物等氟系高分子；具有碱金属离子(例如，锂离子)的离子传导性的高分子组合物等。上述负极粘合剂可以单独使用，也可以任意组合使用。
在负极合剂层含有氟系高分子(例如，聚偏二氟乙烯)的情况下，在一些实施例中，基于负极合剂层的重量，所述负极粘合剂的含量为大于约1％、大于约2％或大于约3％。在一些实施例中，基于负极合剂层的重量，所述负极粘合剂的含量为小于约10％、小于约8％或小于约5％。基于负极合剂层的重量，所述负极粘合剂的含量在上述任意两个数值所组成的范围内。
溶剂
用于形成负极浆料的溶剂的种类没有特别限制，只要是能够溶解或分散负极活性物质、负极粘合剂、以及根据需要使用的增稠剂和导电材料的溶剂即可。在一些实施例中，用于形成负极浆料的溶剂可以使用水系溶剂和有机系溶剂中的任一种。水系溶剂的实例可包括，但不限于，水、醇等。有机系溶剂的实例可包括，但不限于，N-甲基吡咯烷酮(NMP)、二甲基甲酰胺、二甲基乙酰胺、甲基乙基酮、环己酮、乙酸甲酯、丙烯酸甲酯、二乙基三胺、N,N-二甲氨基丙胺、四氢呋喃(THF)、甲苯、丙酮、二乙醚、六甲基磷酰胺、二甲基亚砜、苯、二甲苯、喹啉、吡啶、甲基萘、己烷等。上述溶剂可以单独使用或任意组合使用。
增稠剂
增稠剂通常是为了调节负极浆料的粘度而使用的。增稠剂的种类没有特别限制，其实例可包括，但不限于，羧甲基纤维素、甲基纤维素、羟甲基纤维素、乙基纤维素、聚乙烯醇、氧化淀粉、磷酸化淀粉、酪蛋白和它们的盐等。上述增稠剂可以单独使用，也可以任意组合使用。
在一些实施例中，基于负极合剂层的重量，所述增稠剂的含量为大于约0.1％、大于约0.5％或大于约0.6％。在一些实施例中，基于负极合剂层的重量，所述增稠剂的含量为小于约5％、小于约3％或小于约2％。当增稠剂的含量在上述范围没时，可以抑制电化学装置的容量降低及电阻的增大，同时可以确保负极 浆料具有良好的涂布性。
表面被覆
在一些实施例中，负极合剂层的表面可附着有与其组成不同的物质。负极合剂层的表面附着物质的实例包括，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、碳酸镁等碳酸盐等。
负极活性物质的含量
在一些实施例中，基于负极合剂层的重量，负极活性物质的含量为大于约80％、大于约82％或大于约84％。在一些实施例中，基于负极合剂层的重量，负极活性物质的含量为小于约99％或小于约98％。在一些实施例中，基于负极合剂层的重量，负极活性物质的含量在上述任意两个数组所组成的范围内。
负极活性物质的密度
在一些实施例中，负极合剂层中的负极活性物质的密度为大于约1g/cm 3、大于约1.2g/cm 3或大于约1.3g/cm 3。在一些实施例中，负极合剂层中的负极活性物质的密度为小于约2.2g/cm 3、小于约2.1g/cm 3、小于约2.0g/cm 3或小于约1.9g/cm 3。在一些实施例中，负极合剂层中的负极活性物质的密度在上述任意两个数值所组成的范围内。
当负极活性物质的密度在上述范围内时，可防止负极活性物质颗粒的破坏，可以抑制电化学装置初期不可逆容量的增加或电解液在负极集流体/负极活性物质界面附近的渗透性降低所导致的高电流密度充放电特性恶化，还可以抑制电化学装置的容量降低及电阻增大。
2、负极集流体
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约1μm或大于约5μm。在一些实施例中，负极集流体的厚度为小于约100μm或小于约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。
负极合剂层与负极集流体的厚度比是指单面负极合剂层的厚度除以负极集流体的厚度，其数值没有特别限制。在一些实施例中，厚度比为50以下。在一些实施例中，厚度比为30以下。在一些实施例中，厚度比为20以下。在一些实施例中，厚度比为10以下。在一些实施例中，厚度比为1以上。在一些实施例中，厚度比在由上述任意两个数值所组成的范围内。当厚度比在上述范围内时，可以确保电化学装置的容量，同时可以抑制高电流密度充放电时的负极集流体的放热。
II、电解液
本申请的电化学装置中的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，本申请的电化学装置中的使用的电解液进一步包括添加剂。
本申请的电化学装置的另一个主要特征在于所述电解液包括丙酸酯。
在一些实施例中，所述丙酸酯包括式2化合物：
Figure PCTCN2020121179-appb-000004
其中：
R 1选自乙基或卤代乙基，
R 2选自C 1-C 6烷基或C 1-C 6卤代烷基。
在一些实施例中，所述丙酸酯包括，但不限于，丙酸甲酯、丙酸乙酯、丙酸丙酯、丙酸丁酯、丙酸戊酯、卤代丙酸甲酯、卤代丙酸乙酯、卤代丙酸丙酯、卤代丙酸丁酯和卤代丙酸戊酯。在一些实施例中，所述丙酸酯选自丙酸甲酯、丙酸乙酯、丙酸丙酯、丙酸丁酯和丙酸戊酯中的至少一种。在一些实施例中，所述卤代丙酸甲酯、卤代丙酸乙酯、卤代丙酸丙酯、卤代丙酸丁酯和卤代丙酸戊酯中的卤素基团选自氟基团(-F)、氯基团(-Cl)、溴基团(-Br)和碘基团(-I)中的一种或多种。在一些实施例中，所述卤素基团为氟基团(-F)，其可实现更为优异的效果。
在一些实施例中，基于所述电解液的重量，所述丙酸酯的含量为X％，X在5至65的范围内。在一些实施例中，X在10至60的范围内。在一些实施例中，X在15至50的范围内。在一些实施例中，X在20至40的范围内。在一些实施例中，X为5、10、15、20、25、30、35、40、45、50、55、60、65或在由上述任意两个数值所组成的范围内。当电解液中丙酸酯的含量在上述范围内时，可进一步改善电化学装置的高温存储性能和抗过充性能。
在一些实施例中，电解液中丙酸酯的含量X％与粘接强度F N/cm 2满足：1.6≤F/X≤100。在一些实施例中，2≤F/X≤80。在一些实施例中，3≤F/X≤70。在一些实施例中，5≤F/X≤60。在一些实施例中，6≤F/X≤50。在一些实施例中，F/X为1.6、3、5、7、8、10、15、20、30、40、50、60、70、80、90、100或在以上任意两个数值的范围内。当电解液中丙酸酯的含量X％与粘接强度F N/cm 2满足上述关系时，可进一步改善电化学装置的高温存储性能和抗过充性能。在一些实施例中，所述电解液进一步包括以下化合物中的至少一种：
i)氟代碳酸酯；
ii)具有氰基的化合物；
iii)二氟磷酸锂；
iv)式1化合物：
Figure PCTCN2020121179-appb-000005
其中：
R 1、R 2、R 3、R 4、R 5和R 6各自独立地为氢或C 1-C 10烷基；
L 1和L 2各自独立地为-(CR 7R 8) n-；
R 7和R 8各自独立地为氢或C 1-C 10烷基；以及
n为1、2或3。
i)氟代碳酸酯
在电化学装置充电/放电时，氟代碳酸酯可与丙酸酯共同作用以在负极的表面上形成稳定的保护膜，从而抑制电解液的分解反应。
在一些实施例中，所述氟代碳酸酯具有式C＝O(OR x)(OR y)，其中R x和R y各 自选自具有1-6个碳原子的烷基或卤代烷基，其中R x和R y中的至少一者选自具有1-6个碳原子的氟代烷基，且R x和R y任选地连同其所连接的原子形成5元至7元环。
在一些实施例中，所述氟代碳酸酯的实例可包括，但不限于，以下的一种或多种：氟代碳酸乙烯酯、顺式4,4-二氟碳酸乙烯酯、反式4,4-二氟碳酸乙烯酯、4,5-二氟碳酸乙烯酯、4-氟-4-甲基碳酸乙烯酯、4-氟-5-甲基碳酸乙烯酯、碳酸三氟甲基甲酯、碳酸三氟乙基甲酯和碳酸乙基三氟乙酯等。
在一些实施例中，基于所述电解液的重量，所述氟代碳酸酯的含量在0.1％至10％的范围内。在一些实施例中，基于所述电解液的重量，所述氟代碳酸酯的含量在0.5％至8％的范围内。在一些实施例中，基于所述电解液的重量，所述氟代碳酸酯的含量在1％至5％的范围内。在一些实施例中，基于所述电解液的重量，所述氟代碳酸酯的含量为0.1％、0.5％、1％、2％、3％、4％、5％、6％、7％、8％、9％、10％或在以上任意两个数值的范围内。
ii)具有氰基的化合物
在一些实施例中，具有氰基的化合物包括，但不限于，以下的一种或多种：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)己烷和1,2,5-三(氰基乙氧基)戊烷。
上述具有氰基的化合物可单独使用或任意组合使用。若电解液含两种或多种具有氰基的化合物时，具有氰基的化合物的含量是指两种或多种具有氰基的化合 物的总含量。
在一些实施例中，基于所述电解液的重量，所述具有氰基的化合物的含量为b％，b在0.01至10的范围内。在一些实施例中，b在0.05至8的范围内。在一些实施例中，b在0.1至5的范围内。在一些实施例中，b在0.5至3的范围内。在一些实施例中，b在1至2的范围内。在一些实施例中，b为0.01、0.05、0.1、0.5、1、2、5、8、10或在以上任意两个数值的范围内。当电解液中具有氰基的化合物的含量在上述范围内时，可进一步改善电化学装置的高温存储性能和抗过充性能。
在一些实施例中，电解液中丙酸酯的含量X％与具有氰基的化合物的含量b％满足：0.5≤X/b≤200。在一些实施例中，1≤X/b≤150。在一些实施例中，5≤X/b≤100。在一些实施例中，10≤X/b≤80。在一些实施例中，30≤X/b≤50。在一些实施例中，X/b为0.5、1、5、10、20、50、80、100、120、150、180、200或在以上任意两个数值的范围内。当电解液中丙酸酯的含量X％与具有氰基的化合物的含量b％满足上述关系时，可进一步改善电化学装置的高温存储性能和抗过充性能。
iii)二氟磷酸锂(LiPO 2F 2)
在一些实施例中，基于所述电解液的重量，所述二氟磷酸锂的含量为0.01％至1.5％。在一些实施例中，基于所述电解液的重量，所述二氟磷酸锂的含量为0.05％至1.2％。在一些实施例中，基于所述电解液的重量，所述二氟磷酸锂的含量为0.1％至1.0％。在一些实施例中，基于所述电解液的重量，所述二氟磷酸锂的含量为0.5％至0.8％。在一些实施例中，基于所述电解液的重量，所述二氟磷酸锂的含量为0.01％、0.05％、0.1％、0.15％、0.2％、0.25％、0.3％、0.35％、0.4％、0.45％、0.5％、0.8％、1％、1.5％或在由上述任意两个数值所组成的范围内。
iv)式1化合物
在一些实施例中，所述式1化合物包括以下化合物中的至少一种：
Figure PCTCN2020121179-appb-000006
Figure PCTCN2020121179-appb-000007
在一些实施例中，基于所述电解液的重量，所述式1化合物的含量在0.01％至5％的范围内。在一些实施例中，基于所述电解液的重量，所述式1化合物的含量在0.05％至4％的范围内。在一些实施例中，基于所述电解液的重量，所述式1化合物的含量在0.1％至3％的范围内。在一些实施例中，基于所述电解液的重量，所述式1化合物的含量在0.5％至2％的范围内。在一些实施例中，基于所述电解液的重量，所述式1化合物的含量在1％至1.5％的范围内。在一些实施例中，基于所述电解液的重量，所述式1化合物的含量为0.01％、0.05％、0.1％、0.5％、1％、2％、3％、4％、5％或在以上任意两个数值的范围内。当电解液中式1化合物的含量在上述范围内时，可进一步改善电化学装置的高温存储性能和抗过充性能。
溶剂
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：碳酸亚乙酯(EC)、碳酸亚丙酯(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：碳酸亚乙酯、碳酸亚丙酯、碳酸二乙酯、丙酸乙酯、丙酸丙酯、乙酸正丙酯、乙酸乙酯及其组合。在一些实施例中，本申请的电解液中使用的溶剂包含：碳酸亚乙酯、碳酸亚丙酯、碳酸二乙酯、丙酸乙酯、丙酸丙酯、γ-丁内酯及其组合。
添加剂
在一些实施例中，所述添加剂的实例可包括，但不限于，以下的一种或多种：氟代碳酸酯、含碳碳双键的碳酸乙烯酯、含硫氧双键的化合物和酸酐。
在一些实施例中，基于所述电解液的重量，所述添加剂的含量为0.01％至15％、0.1％至10％或1％至5％。
根据本申请的实施例，基于所述电解液的重量，所述丙酸酯的含量为所述添加剂的1.5至30倍、1.5至20倍、2至20倍或5至20倍。
在一些实施例中，所述添加剂包含一种或多种含碳碳双键的碳酸乙烯酯。所述含碳碳双键的碳酸乙烯酯的实例可包括，但不限于，以下的一种或多种：碳酸亚乙烯酯、碳酸甲基亚乙烯酯、碳酸乙基亚乙烯酯、碳酸-1,2-二甲基亚乙烯酯、碳酸-1,2-二乙基亚乙烯酯、碳酸氟亚乙烯酯、碳酸三氟甲基亚乙烯酯；碳酸乙烯基亚乙酯、碳酸-1-甲基-2-乙烯基亚乙酯、碳酸-1-乙基-2-乙烯基亚乙酯、碳酸-1-正丙基-2-乙烯基亚乙酯、碳酸1-甲基-2-乙烯基亚乙酯、碳酸-1,1-二乙烯基亚乙酯、碳酸-1,2-二乙烯基亚乙酯、碳酸-1,1-二甲基-2-亚甲基亚乙酯和碳酸-1,1-二乙基-2-亚甲基亚乙酯等。在一些实施例中，所述含碳碳双键的碳酸乙烯酯包括碳酸亚乙烯酯，其易于获得并可实现更为优异的效果。
在一些实施例中，所述添加剂为氟代碳酸酯与含碳碳双键的碳酸乙烯酯的组合。在一些实施例中，所述添加剂为氟代碳酸酯与含硫氧双键的化合物的组合。在一些实施例中，所述添加剂为氟代碳酸酯与具有2-4个氰基的化合物的组合。在一些实施例中，所述添加剂为氟代碳酸酯与环状羧酸酯的组合。在一些实施例中，所述添加剂为氟代碳酸酯与环状磷酸酐的组合。在一些实施例中，所述添加剂为氟代碳酸酯与羧酸酐的组合。在一些实施例中，所述添加剂为氟代碳酸酯与璜酸酐的组合。在一些实施例中，所述添加剂为氟代碳酸酯与羧酸璜酸酐的组合。
电解质
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，基于电解质的重量，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，基于电解质的重量，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除此以外的一种以上的盐。作为除此以外的盐，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，基于电解质的重量，除此以外的盐的含量为大于0.01％或大于0.1％。在一些实施例中，基于电解质的重量，除此以外的盐的含量为小于20％、小于15％或小于10％。在一些实施例中，除此以外的盐的含量在上述任意两个数值所组成的范围内。具有上述含量的除此以外的盐有助于平衡电解液的电导率和粘度。
在电解液中，除了含有上述溶剂、添加剂和电解质盐以外，可以根据需要含有负极被膜形成剂、正极保护剂、防过充电剂等额外添加剂。作为添加剂，可使用一般在非水电解质二次电池中使用的添加剂，其实例可包括，但不限于，碳酸亚乙烯酯、琥珀酸酐、联苯、环己基苯、2,4-二氟苯甲醚、丙烷磺内酯、丙烯磺内酯等。这些添加剂可以单独使用或任意组合使用。另外，电解液中的这些添加剂的含量没有特别限制，可以根据该添加剂的种类等适当地设定即可。在一些实施例中，基于电解液的重量，添加剂的含量为小于5％、在0.01％至5％的范围内或在0.2％至5％的范围内。
III、正极
正极包括正极集流体和设置在所述正极集流体的一个或两个表面上的正极活性物质层。
1、正极活性物质层
正极活性物质层包含正极活性物质。所述正极活性物质层可以是一层或多层。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。
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重量，磷酸锂的含量为大于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重量，磷酸锂的含量为小于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。
表面被覆
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，基于正极活性物质层的重量，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重量，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重量，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”。
形状
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。
振实密度
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)。
中值粒径(D50)
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。
平均一次粒径
在正极活性物质颗粒的一次颗粒凝集而形成二次颗粒的情况下，在一些实施例中，正极活性物质的平均一次粒径为大于0.05μm、大于0.1μm或大于0.5μm。在一些实施例中，正极活性物质的平均一次粒径为小于5μm、小于4μm、小于3μm或小于2μm。在一些实施例中，正极活性物质的平均一次粒径在上述任意两个数值所组成的范围内。当正极活性物质的平均一次粒径在上述范围内时，可以确保粉体填充性和比表面积、抑制电池性能的降低、并得到适度的结晶性，由此可以确保电化学装置充放电的可逆性。
正极活性物质的平均一次粒径可通过对扫描电子显微镜(SEM)得到的图像进行观察而得出：在倍率为10000倍的SEM图像中，对于任意50个一次颗粒，求出由相对于水平方向直线的一次颗粒的左右边界线所得到的切片的最长值，求出其平均值，由此得到平均一次粒径。
比表面积(BET)
在一些实施例中，正极活性物质的比表面积(BET)为大于0.1m 2/g、大于0.2m 2/g或大于0.3m 2/g。在一些实施例中，正极活性物质的比表面积(BET)为小于50m 2/g、小于40m 2/g或小于30m 2/g。在一些实施例中，正极活性物质的比表面积(BET)在上述任意两个数值所组成的范围内。当正极活性物质的比表面积(BET)在上述范围内时，可以确保电化学装置的性能，同时可以使正极活性物质具有良好的涂布性。
正极活性物质的比表面积(BET)可通过如下方法测量：使用表面积计(例如，大仓理研制造的全自动表面积测定装置)，在氮气流通下于150℃对试样进行30分钟预干燥，然后使用氮气相对于大气压的相对压力值准确调节为0.3的氮氦混合气体，通过采用气体流动法的氮吸附BET单点法进行测定。
正极导电材料
正极导电材料的种类没有限制，可以使用任何已知的导电材料。正极导电材料的实例可包括，但不限于，天然石墨、人造石墨等石墨；乙炔黑等炭黑；针状焦等无定形碳等碳材料；碳纳米管；石墨烯等。上述正极导电材料可单独使用或任意组合使用。
在一些实施例中，基于正极活性物质层的重量，正极导电材料的含量为大于0.01％、大于0.1％或大于1％。在一些实施例中，基于正极活性物质层的重量，正极导电材料的含量为小于10％、小于8％以下或小于5％。当正极导电材料的 含量在上述范围内时，可以确保充分的导电性和电化学装置的容量。
正极粘合剂
正极活性物质层的制造中使用的正极粘合剂的种类没有特别限制，在涂布法的情况下，只要是在电极制造时使用的液体介质中可溶解或分散的材料即可。正极粘合剂的实例可包括，但不限于，以下中的一种或多种：聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯、聚甲基丙烯酸甲酯、聚酰亚胺、芳香族聚酰胺、纤维素、硝酸纤维素等树脂系高分子；丁苯橡胶(SBR)、丁腈橡胶(NBR)、氟橡胶、异戊二烯橡胶、聚丁橡胶、乙烯-丙烯橡胶等橡胶状高分子；苯乙烯·丁二烯·苯乙烯嵌段共聚物或其氢化物、乙烯·丙烯·二烯三元共聚物(EPDM)、苯乙烯·乙烯·丁二烯·乙烯共聚物、苯乙烯·异戊二烯·苯乙烯嵌段共聚物或其氢化物等热塑性弹性体状高分子；间规-1,2-聚丁二烯、聚乙酸乙烯酯、乙烯·乙酸乙烯酯共聚物、丙烯·α-烯烃共聚物等软质树脂状高分子；聚偏二氟乙烯(PVDF)、聚四氟乙烯、氟化聚偏二氟乙烯、聚四氟乙烯·乙烯共聚物等氟系高分子；具有碱金属离子(特别是锂离子)的离子传导性的高分子组合物等。上述正极粘合剂可单独使用或任意组合使用。
在一些实施例中，基于正极活性物质层的重量，正极粘合剂的含量为大于0.1％、大于1％或大于1.5％。在一些实施例中，基于正极活性物质层的重量，正极粘合剂的含量为小于10％、小于5％、小于4％或小于3％。当正极粘合剂的含量在上述范围内时，可使正极具有良好的导电性和足够的机械强度，并保证电化学装置的容量。
溶剂
用于形成正极浆料的溶剂的种类没有限制，只要是能够溶解或分散正极活性物质、导电材料、正极粘合剂和根据需要使用的增稠剂的溶剂即可。用于形成正极浆料的溶剂的实例可包括水系溶剂和有机系溶剂中的任一种。水系介质的实例可包括，但不限于，水和醇与水的混合介质等。有机系介质的实例可包括，但不限于，己烷等脂肪族烃类；苯、甲苯、二甲苯、甲基萘等芳香族烃类；喹啉、吡啶等杂环化合物；丙酮、甲基乙基酮、环己酮等酮类；乙酸甲酯、丙烯酸甲酯等酯类；二亚乙基三胺、N,N-二甲氨基丙胺等胺类；二乙醚、环氧丙烷、四氢呋喃(THF)等醚类；N-甲基吡咯烷酮(NMP)、二甲基甲酰胺、二甲基乙酰胺等酰胺类；六甲基磷酰胺、二甲基亚砜等非质子性极性溶剂等。
增稠剂
增稠剂通常是为了调节浆料的粘度而使用的。在使用水系介质的情况下，可使用增稠剂和丁苯橡胶(SBR)乳液进行浆料化。增稠剂的种类没有特别限制，其实例可包括，但不限于，羧甲基纤维素、甲基纤维素、羟甲基纤维素、乙基纤维素、聚乙烯醇、氧化淀粉、磷酸化淀粉、酪蛋白和它们的盐等。上述增稠剂可单独使用或任意组合使用。
在一些实施例中，基于正极活性物质层的重量，增稠剂的含量为大于0.1％、大于0.2％或大于0.3％。在一些实施例中，基于正极活性物质层的重量，增稠剂的含量为小于5％、小于3％或小于2％。在一些实施例中，基于正极活性物质层的重量，增稠剂的含量在上述任意两个数值所组成的范围内。当增稠剂的含量在上述范围内时，可使正极浆料具有良好的涂布性，同时可以抑制电化学装置的容量降低及电阻增大。
正极活性物质的含量
在一些实施例中，基于正极活性物质层的重量，正极活性物质的含量为大于80％、大于82％或大于84％。在一些实施例中，基于正极活性物质层的重量，正极活性物质的含量为小于99％或小于98％。在一些实施例中，基于正极活性物质层的重量，正极活性物质的含量在上述任意两个数组所组成的范围内。当正极活性物质的含量在上述范围内时，可以确保正极活性物质层中的正极活性物质的电容量，同时可以保持正极的强度。
正极活性物质层的密度
对于通过涂布、干燥而得到的正极活性物质层，为了提高正极活性物质的填充密度，可通过手动压机或辊压机等进行压紧处理。在一些实施例中，正极活性物质层的密度为大于1.5g/cm 3、大于2g/cm 3或大于2.2g/cm 3。在一些实施例中，正极活性物质层的密度为小于5g/cm 3、小于4.5g/cm 3或小于4g/cm 3。在一些实施例中，正极活性物质层的密度在上述任意两个数值所组成的范围内。当正极活性物质层的密度在上述范围内时，可使电化学装置具有良好的充放电特性，同时可以抑制电阻的增大。
正极活性物质层的厚度
正极活性物质层的厚度是指正极活性物质层在正极集流体的任意一侧上的厚度。在一些实施例中，正极活性物质层的厚度为大于10μm或大于20μm。在 一些实施例中，正极活性物质层的厚度为小于500μm或小于450μm。
正极活性物质的制造法
正极活性物质可使用制造无机化合物的常用方法来制造。为了制作球状或椭圆球状的正极活性物质，可采用以下制造方法：将过渡金属的原料物质溶解或粉碎分散于水等溶剂中，边搅拌边调节pH，制作球状的前体并回收，根据需要对其进行干燥后，加入LiOH、Li 2CO 3、LiNO 3等Li源，在高温下进行烧制，得到正极活性物质。
2、正极集流体
正极集流体的种类没有特别限制，其可为任何已知适于用作正极集流体的材质。正极集流体的实例可包括，但不限于，铝、不锈钢、镍镀层、钛、钽等金属材料；碳布、碳纸等碳材料。在一些实施例中，正极集流体为金属材料。在一些实施例中，正极集流体为铝。
正极集流体的形式没有特别限制。当正极集流体为金属材料时，正极集流体的形式可包括，但不限于，金属箔、金属圆柱、金属带卷、金属板、金属箔、金属板网、冲压金属、发泡金属等。当正极集流体为碳材料时，正极集流体的形式可包括，但不限于，碳板、碳薄膜、碳圆柱等。在一些实施例中，正极集流体为金属箔。在一些实施例中，所述金属箔为网状。所述金属箔的厚度没有特别限制。在一些实施例中，所述金属箔的厚度为大于1μm、大于3μm或大于5μm。在一些实施例中，所述金属箔的厚度为小于1mm、小于100μm或小于50μm。在一些实施例中，所述金属箔的厚度在上述任意两个数值所组成的范围内。
为了降低正极集流体和正极活性物质层的电子接触电阻，正极集流体的表面可包括导电助剂。导电助剂的实例可包括，但不限于，碳和金、铂、银等贵金属类。
正极活性物质层与正极集流体的厚度比是指单面的正极活性物质层的厚度除以正极集流体的厚度，其数值没有特别限制。在一些实施例中，厚度比为小于50、小于30或小于20。在一些实施例中，厚度比为大于0.5、大于0.8或大于1。在一些实施例中，厚度比在上述任意两个数值所组成的范围内。当厚度比在上述范围内时，可以抑制高电流密度充放电时的正极集流体的放热，可以确保电化学装置的容量。
3、正极的制作法
正极可以通过在集流体上形成含有正极活性物质和粘结剂的正极活性物质层来制作。使用正极活性物质的正极的制造可以通过常规方法来进行，即，将正极活性物质和粘结剂、以及根据需要的导电材料和增稠剂等进行干式混合，制成片状，将所得到的片状物压接至正极集流体上；或者将这些材料溶解或分散于液体介质中而制成浆料，将该浆料涂布到正极集流体上并进行干燥，从而在集流体上形成正极活性物质层，由此可以得到正极。
IV、隔离膜
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。
V、电化学装置组件
电化学装置组件包括电极组、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。
VI、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。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、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，得到负极浆料。将该负极浆料涂布在12μm的集流体上。干燥，冷压，再经过裁片、焊接极耳，得到负极。
橡胶 名称
1 丁苯橡胶(SBR)
2 丙烯酸酯丁苯橡胶共聚物
3 苯乙烯丙烯酸酯共聚物
4 氯三氟乙烯-丁苯橡胶共混
5 HFP(六氟丙烯)丁苯橡胶共混
2、正极的制备
将钴酸锂(LiCoO 2)、导电材料(Super-P)和聚偏氟乙烯(PVDF)按照95％:2％:3％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、PC和DEC(重量比1:1:1)混合，加入LiPF 6混合均匀，形成基础电解液，其中LiPF 6的浓度为1.15mol/L。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。
电解液中组分的缩写及其名称如下表所示：
Figure PCTCN2020121179-appb-000008
Figure PCTCN2020121179-appb-000009
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、锂离子电池的高温存储膨胀率的测试方法
在25℃下，将锂离子电池静置30分钟，然后以0.5C倍率恒流充电至4.45V，再在4.45V下恒压充电至0.05C，静置5分钟，测量锂离子电池的厚度。在60℃下存储21天后再次测量锂离子电池的厚度。通过下式计算锂离子电池的高温存储膨胀率：
高温存储膨胀率＝[(存储后厚度-存储前厚度)/存储前厚度]×100％。
2、锂离子电池的过充变形率的测试方法
在25℃下，将锂离子电池静置30分钟，然后以0.5C倍率恒流充电至4.45V，再在4.45V下恒压充电至0.05C，静置60分钟，测量锂离子电池的厚度T1。然后以0.1C倍率恒流充电60分钟，静置30分钟，重复该步骤5次，使锂离子电池达到150％荷电状态(SOC)，测量锂离子电池厚度T2。
过充变形率＝[(T2-T1)/T1]×100％。
三、测试结果
表1展示了负极活性物质之间的粘接强度以及电解液中丙酸酯对锂离子电池的高温存储膨胀率和过充变形率的影响。
表1
Figure PCTCN2020121179-appb-000010
Figure PCTCN2020121179-appb-000011
“/”表示不添加或不具备该特征
结果表明，当负极活性物质之间的粘接强度为100N/cm 2至500N/cm 2且电解液包括丙酸酯时，能够抑制充放电过程导致的负极膨胀/收缩，稳定负极合剂层与电解液之间界面，从而显著降低锂离子电池的高温存储膨胀率和过充变形率。
当负极活性物质之间的粘接强度F N/cm 2与电解液中丙酸酯的含量X％满足1.6≤F/X≤100时，可进一步降低锂离子电池的高温存储膨胀率和过充变形率。
表2展示了负极合剂层的比表面积对锂离子电池性能的高温存储膨胀率和过充变形率的影响。实施例2-1至2-6与实施例1-1或实施例1-5的区别仅在于表2所列参数。
表2
Figure PCTCN2020121179-appb-000012
结果表明，当负极合剂层的比表面积为2m 2/g至5m 2/g时，可进一步降低锂离子电池的高温存储膨胀率和过充变形率。当负极合剂层的比表面积A m 2/g与负极活性物质之间的粘接强度F N/cm 2满足20≤F/A≤250时，可进一步降低锂离子电池的高温存储膨胀率和过充变形率。
表3展示了负极活性物质中微量金属对锂离子电池的高温存储膨胀率和过充变形率的影响。实施例3-1至3-8与实施例1-1的区别仅在于表3中所列参数。
表3
Figure PCTCN2020121179-appb-000013
结果表明，当负极活性物质中存在微量金属元素(铁、钼和/或铜)时，可进一步降低锂离子电池的高温存储膨胀率和过充变形率。
表4展示了电解液组分对锂离子电池的高温存储膨胀率和过充变形率的影响。实施例4-1至4-31与实施例1-1的区别仅在于表4中所列参数。
表4
Figure PCTCN2020121179-appb-000014
Figure PCTCN2020121179-appb-000015
“/”表示不添加或不具备该特征
结果表明，在当负极活性物质之间的粘接强度为100N/cm 2至500N/cm 2且电解液包括丙酸酯的基础上，当电解液进一步包含氟代碳酸酯、具有氰基的有机化合物、二氟磷酸锂和/或式1化合物时，可进一步降低锂离子电池的高温存储膨胀率和过充变形率。
表5展示了电解液中丙酸酯的含量X％与具有氰基的有机化合物b％之间的关系对锂离子电池的高温存储膨胀率和过充变形率的影响。实施例5-1至5-8与实施例1-1或实施例4-3的区别仅在于表5中所列参数。
表5
Figure PCTCN2020121179-appb-000016
Figure PCTCN2020121179-appb-000017
“/”表示不添加或不具备该特征
结果表明，当电解液中具有氰基的有机化合物的含量为0.01％至10％时，可进一步降低锂离子电池的高温存储膨胀率和过充变形率。当电解液中丙酸酯的含量X％与具有氰基的有机化合物的含量b％满足0.5≤X/b≤200时，可进一步降低锂离子电池的高温存储膨胀率和过充变形率。
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 (14)

  1. 一种电化学装置，其包括正极、负极和电解液，所述负极包括负极集流体和形成在所述负极集流体上的负极合剂层，所述负极合剂层包括负极活性物质，其中：
    所述负极活性物质之间的粘接强度为F N/cm 2，F在100至500的范围内；
    所述电解液包括丙酸酯。
  2. 根据权利要求1所述的电化学装置，其中所述负极合剂层包括橡胶，所述橡胶包括丁苯橡胶、异戊二烯橡胶、丁二烯橡胶、氟橡胶、丙烯腈-丁二烯橡胶、苯乙烯-丙烯橡胶中的至少一种。
  3. 根据权利要求2所述的电化学装置，其中所述橡胶进一步包括丙烯酸官能团、氯三氟乙烯官能团或六氟丙烯官能团中的至少一种。
  4. 根据权利要求1所述的电化学装置，其中基于所述电解液的重量，所述丙酸酯的含量为X％，X在5至65的范围内。
  5. 根据权利要求4所述的电化学装置，其中F与X满足：1.6≤F/X≤100。
  6. 根据权利要求1所述的电化学装置，其中所述负极合剂层的比表面积为A m 2/g，A在2至5的范围内。
  7. 根据权利要求6所述的电化学装置，其中F与A满足：20≤F/A≤250。
  8. 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具有以下特征中的至少一者：
    (a)具有5μm至30μm的中值粒径；
    (b)包括人造石墨、天然石墨、中间相碳微球、软碳、硬碳、无定形碳、含硅材料、含锡材料、合金材料中的至少一种；
    (c)包括金属，所述金属包括钼、铁或铜中的至少一种，并且基于所述负极合剂层的重量，所述金属的含量为0.05％以下。
  9. 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以下化合物中的至少一种：
    a)氟代碳酸酯；
    b)具有氰基的化合物；
    c)二氟磷酸锂；
    d)式1化合物：
    Figure PCTCN2020121179-appb-100001
    其中：
    R 1、R 2、R 3、R 4、R 5和R 6各自独立地为氢或C 1-C 10烷基；
    L 1和L 2各自独立地为-(CR 7R 8) n-；
    R 7和R 8各自独立地为氢或C 1-C 10烷基；以及
    n为1、2或3。
  10. 根据权利要求9所述的电化学装置，其中所述式1化合物包括以下化合物中的至少一种：
    Figure PCTCN2020121179-appb-100002
  11. 根据权利要求9所述的电化学装置，其中基于所述电解液的重量，所述式1化合物的含量在0.01％至5％的范围内。
  12. 根据权利要求9所述的电化学装置，其中基于所述电解液的重量，所述具有氰基的化合物的含量为b％，b在0.01至10的范围内。
  13. 根据权利要求12所述的电化学装置，其中基于所述电解液的重量，所述丙酸酯的含量为X％，X在5至65的范围内且0.5≤X/b≤200。
  14. 一种电子装置，其包括根据权利要求1-13中任一项所述的电化学装置。
PCT/CN2020/121179 2020-10-15 2020-10-15 电化学装置和电子装置 WO2022077350A1 (zh)

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