WO2023123029A1 - 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
WO2023123029A1
WO2023123029A1 PCT/CN2021/142399 CN2021142399W WO2023123029A1 WO 2023123029 A1 WO2023123029 A1 WO 2023123029A1 CN 2021142399 W CN2021142399 W CN 2021142399W WO 2023123029 A1 WO2023123029 A1 WO 2023123029A1
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Prior art keywords
positive electrode
active material
electrochemical device
electrode active
electrolyte
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PCT/CN2021/142399
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English (en)
French (fr)
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王可飞
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宁德新能源科技有限公司
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Priority to PCT/CN2021/142399 priority Critical patent/WO2023123029A1/zh
Priority to CN202180030797.8A priority patent/CN115552678A/zh
Publication of WO2023123029A1 publication Critical patent/WO2023123029A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—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
    • 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
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/381—Alkaline or alkaline earth metals elements
    • 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
    • H01M4/623—Binders being polymers fluorinated polymers
    • 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, especially a lithium ion battery.
  • the embodiments of the present application solve the problems existing in the prior art to some extent by providing an electrochemical device and an electronic device with improved high-temperature cycle performance and safety.
  • the present application provides an electrochemical device, which includes: a positive electrode, a negative electrode and an electrolyte, the positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, the The positive electrode active material layer includes a positive electrode active material and a binder, wherein: the positive electrode active material has a first element, the first element includes at least one of aluminum, magnesium, titanium, zirconium or tungsten, and the binder The density of the binder is a g/cm 3 , and the value of a ranges from 0.6 to 1.5.
  • the value range of a is 0.6 to 1.2, 0.7 to 1.0 or 0.7 to 0.9.
  • the porosity of the binder is b%, the value of b ranges from 20 to 50, and a and b satisfy: 17 ⁇ a ⁇ b ⁇ 60.
  • the binder includes a fluoropolymer, preferably polyvinylidene fluoride.
  • the electrochemical device satisfies at least one of the following:
  • said first element comprises aluminum and at least one of magnesium, titanium, zirconium or tungsten;
  • said first element comprises tungsten and at least one of magnesium, titanium, zirconium or aluminum;
  • the first element includes aluminum and tungsten, based on the weight of the positive electrode active material, the contents of aluminum and tungsten are x% and y%, respectively, and x and y satisfy: 1 ⁇ x/y ⁇ 5;
  • the content of the first element is 0.01 to 2%.
  • the first element includes aluminum, the content of aluminum is x% based on the weight of the positive electrode active material, and x and a satisfy 0.2 ⁇ x/a ⁇ 1.
  • the electrolyte includes a compound having a sulfur-oxygen double bond, based on the weight of the electrolyte, the content of the compound having a sulfur-oxygen double bond is c%, and the range of c is 0.01 to 5.
  • c and a satisfy: 0.5 ⁇ c/a ⁇ 3.
  • the electrolyte includes a trinitrile compound, and the content of the trinitrile compound is d% based on the weight of the electrolyte, and the value of d ranges from 0.01 to 5.
  • d and a satisfy: 0.2 ⁇ d/a ⁇ 4.
  • the electrolyte includes succinonitrile, adiponitrile, ethylene glycol bis(2-cyanoethyl) ether, fluoroethylene carbonate, vinylene carbonate or 1-propyl phosphoric acid at least one of the cyclic anhydrides.
  • the present application provides an electronic device comprising the electrochemical device according to the present application.
  • the combination of the positive electrode active material containing doping elements and the low-density binder used in the present application effectively improves the interface stability of the positive electrode, thereby significantly improving the high-temperature cycle performance and safety of the electrochemical device.
  • a list of items linked by the term "at least one of” may mean any combination of the listed items.
  • the phrase "at least one of A and B” means only A; only B; or A and B.
  • the phrase "at least one of A, B, and C” means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C.
  • Item A may contain a single element or multiple elements.
  • Item B may contain a single element or multiple elements.
  • Item C may contain a single element or multiple elements.
  • the term "at least one of" has the same meaning as the term "at least one of”.
  • Commonly used methods to increase the energy density of electrochemical devices include the use of high-voltage (4.4V and above) lithium cobaltate cathode active materials and high-capacity, high-density graphite anode materials.
  • high-voltage (4.4V and above) lithium cobaltate cathode active materials and high-capacity, high-density graphite anode materials.
  • SEI solid electrolyte interface
  • the electrolyte is prone to oxidative decomposition on the surface of the positive electrode to generate a large amount of gas, which will lead to the swelling of the lithium-ion battery and the destruction of the electrode interface, thereby deteriorating the performance of the lithium-ion battery.
  • the side reaction between it and the electrolyte is intensified, so that the decomposition products of the electrolyte are continuously deposited on the surface of the positive electrode, which will further increase the lithium-ion battery.
  • Internal resistance which adversely affects the high-temperature cycle performance of lithium-ion batteries. These factors also make lithium-ion batteries have great potential safety hazards.
  • the industry usually uses aluminum, magnesium, titanium, zirconium or tungsten doping in positive electrode active materials (such as lithium cobalt oxide or ternary materials), in which aluminum and magnesium elements are more easily doped into the crystal structure of the material, while titanium and zirconium Elements tend to be enriched on the particle surface, and tungsten is used to improve conductivity.
  • positive electrode active materials such as lithium cobalt oxide or ternary materials
  • aluminum and magnesium elements are more easily doped into the crystal structure of the material
  • titanium and zirconium Elements tend to be enriched on the particle surface
  • tungsten is used to improve conductivity.
  • the binder density currently used in the positive electrode slurry is mostly above 1.7g/cm 3 .
  • the present application unexpectedly solves problems related to high temperature cycling and safety performance of electrochemical devices by using a positive active material comprising at least one of aluminum, magnesium, titanium, zirconium, or tungsten, and a low-density binder.
  • a positive active material comprising at least one of aluminum, magnesium, titanium, zirconium, or tungsten, and a low-density binder.
  • Doping at least one element of aluminum, magnesium, titanium, zirconium or tungsten in the positive electrode active material can effectively improve the lattice stability, thereby suppressing the volume change of the particles in the charge-discharge cycle under high temperature or low temperature conditions, and Reduce particle cracks and breakage, and at the same time, it can also improve the interface stability of the positive electrode.
  • the low-density binder can achieve a good binding effect, and at the same time, it is less affected by the compaction density during the preparation of the positive electrode, which helps to improve the surface properties of the positive electrode.
  • the specific combination of the positive electrode active material and the binder of the present application can not only effectively improve the high-temperature cycle performance of the electrochemical device, but also significantly improve the safety of the electrochemical device (eg, short-circuit safety and thermal abuse safety, etc.).
  • the positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector.
  • the positive active material layer may be one or more layers.
  • the positive active material layer includes positive active materials, and each layer of the multilayer positive active materials may contain the same or different positive active materials.
  • the positive electrode active material layer includes a positive electrode active material and a binder, and the positive electrode active material has a first element, and the first element includes aluminum, magnesium, titanium, zirconium or At least one of tungsten, and the density of the binder is a g/cm 3 , and the value of a ranges from 0.6 to 1.5. In some embodiments, a ranges from 0.6 to 1.2. In some embodiments, a ranges from 0.7 to 1.0. In some embodiments, a ranges from 0.7 to 0.9.
  • the density of the positive electrode binder commonly used in the battery field is usually greater than 1.7 g/cm 3 to ensure sufficient binding force.
  • the inventors of the present application unexpectedly found that when the density of the positive electrode binder is greater than 1.5 g/cm 3 , it will affect the flexibility of the positive electrode to a certain extent, making it prone to fracture during the winding process; When the density of the positive electrode binder is less than 0.6 g/cm 3 , the binding force of the binder is insufficient, thereby adversely affecting the electrochemical stability of the electrochemical device.
  • the positive electrode binder has a more porous structure, which is beneficial to improving the strength of the electrode and accelerating the infiltration of the electrolyte. When the density of the positive electrode binder is controlled within the above range, not only good binding properties can be achieved, but also the high-temperature cycle performance and safety of the electrochemical device can be significantly improved.
  • the porosity of the binder is b%, and the value of b ranges from 20 to 50. In some embodiments, b ranges from 25 to 45. In some embodiments, b is 20, 22, 25, 30, 35, 40, 45, 50 or within a range consisting of any two values above. When the porosity of the binder is within the above range, it is helpful to further improve the high-temperature cycle performance and safety of the electrochemical device.
  • a and b satisfy: 17 ⁇ a ⁇ b ⁇ 60. In some embodiments, a and b satisfy the following relationship: 20 ⁇ a ⁇ b ⁇ 50. In some embodiments, a ⁇ b is 17, 18, 19, 20, 25, 30, 35, 40, 45, 50, 55, 60 or within a range consisting of any two values above. When the density and porosity of the binder meet the above relationship, it is helpful to further improve the high-temperature cycle performance and safety of the electrochemical device.
  • the binder includes a fluoropolymer.
  • the fluoropolymer includes polyvinylidene fluoride.
  • the content of the first element is 0.01 to 2%. In some embodiments, based on the weight of the positive electrode active material, the content of the first element is 0.05 to 1%. In some embodiments, based on the weight of the positive electrode active material, the content of the first element is 0.1 to 0.5%. In some embodiments, based on the weight of the positive electrode active material, the content of the first element is 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, or any two of the above values. In the range.
  • the content of the first element in the positive electrode active material satisfies the above relationship, the surface defects of the crystal structure of the positive electrode active material can be reduced, the continuous destruction of the positive electrode surface passivation layer in the charge and discharge cycle of the electrochemical device can be effectively suppressed, the number of repairs can be reduced, and the improvement can be fully improved.
  • the interfacial stability of the positive electrode active material layer further improves the high-temperature cycle performance and safety of the electrochemical device.
  • the first element includes at least two of aluminum, magnesium, titanium, zirconium, or tungsten.
  • the positive active material has higher stability under high temperature and high pressure, and its combination with a low-density binder can further improve the high-temperature cycle performance and safety of the electrochemical device.
  • the first element further includes aluminum and at least one of magnesium, titanium, zirconium or tungsten.
  • the first element further includes tungsten and at least one of magnesium, titanium, zirconium or aluminum.
  • the first element includes aluminum and tungsten, based on the weight of the positive electrode active material, the contents of aluminum and tungsten are x% and y%, respectively, and x and y satisfy: 1 ⁇ x/y ⁇ 5 . In some embodiments, x and y satisfy the following relationship: 1.5 ⁇ x/y ⁇ 4.5. In some embodiments, x/y is 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 or within a range consisting of any two of the above values.
  • the content of aluminum and tungsten in the positive electrode active material satisfies the above relationship, it can reduce the decomposition and regeneration of the passivation layer on the surface of the positive electrode during the cycle of the electrochemical device, fully improve the interface stability of the positive electrode active material layer, and help to further improve the battery life. High temperature cycling performance and safety of chemical plants.
  • the first element includes aluminum
  • the content of aluminum is x% based on the weight of the positive electrode active material
  • x and a satisfy 0.2 ⁇ x/a ⁇ 1.
  • x/a is 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 or within a range consisting of any two of the above values.
  • x ranges from 0.01 to 1. In some embodiments, x ranges from 0.05 to 0.5. In some embodiments, x ranges from 0.1 to 0.3. In some embodiments, x is 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 or within a range consisting of any two values above.
  • the value of y ranges from 0.01 to 1. In some embodiments, y ranges from 0.05 to 0.5. In some embodiments, y ranges from 0.1 to 0.3. In some embodiments, y is 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 or within a range consisting of any two values above.
  • the type of positive electrode active material is not particularly limited, as long as it can store and release metal ions (for example, lithium ions) electrochemically.
  • the positive active material is a material containing lithium and at least one transition metal.
  • positive active materials may include, but are not limited to, lithium transition metal composite oxides and lithium transition metal phosphate compounds.
  • a substance different from its composition may be attached to the surface of the positive electrode active material.
  • surface attachment substances may include, but are not limited to: oxides such as alumina, silica, titania, zirconia, magnesia, calcium oxide, boron oxide, antimony oxide, bismuth oxide; lithium sulfate, sodium sulfate, potassium sulfate , magnesium sulfate, calcium sulfate, aluminum sulfate and other sulfates; lithium carbonate, calcium carbonate, magnesium carbonate and other carbonates; carbon, etc.
  • a positive electrode active material having a composition different from the positive electrode active material attached to the surface of the positive electrode active material is also referred to as a "positive electrode active material".
  • the positive electrode active material includes at least one of lithium cobalt oxide or lithium nickel cobalt manganese oxide.
  • the shape of the positive electrode active material particles includes, but is not limited to, block shape, polyhedron shape, spherical shape, ellipsoidal shape, plate shape, needle shape and columnar shape.
  • the positive active material particles include primary particles, secondary particles, or a combination thereof. In some embodiments, primary particles may agglomerate to form secondary particles.
  • positive electrode conductive material is not limited, and any known conductive material can be used.
  • positive electrode conductive materials may include, but are not limited to, graphite such as natural graphite and 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 positive electrode conductive materials can be used alone or in any combination.
  • the kind of 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, conductive material, positive electrode binder, and thickener used as needed.
  • the solvent used to form the positive electrode slurry may include any one of aqueous solvents and organic solvents.
  • aqueous media may include, but are not limited to, water, mixed media of alcohol and water, and the like.
  • organic media may include, but are not limited to, aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; acetone, methyl ethyl ketones such as 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; amides such as N-methylpyrrolidone (NMP), dimethylformamide, and dimethylacetamide; aprotic polar solvents such as hexamethylphosphoramide and dimethyl sulfoxide, etc.
  • aliphatic hydrocarbons such as hexane
  • aromatic hydrocarbons such as benz
  • Thickeners are generally used to adjust the viscosity of the slurry.
  • thickeners and styrene-butadiene rubber (SBR) emulsions 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, carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch , casein and their salts, etc.
  • the above-mentioned thickeners can be used alone or in any combination.
  • the type of the positive electrode collector is not particularly limited, and it can be any known material suitable for use as the positive electrode collector.
  • the positive current collector may include, but are not limited to, metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum; carbon materials such as carbon cloth and carbon paper.
  • the positive current collector is a metal material.
  • the positive current collector is aluminum.
  • 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 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 manufacture of the positive electrode using the positive electrode active material can be carried out by a conventional method, that is, the positive electrode active material and the binder, as well as the conductive material and thickener as required, etc. are dry mixed, made into a sheet, and the obtained The sheet is pressed onto the positive current collector; or these materials are dissolved or dispersed in a liquid medium to make a slurry, and the slurry is coated on the positive current collector and dried to form a positive electrode current collector.
  • a positive electrode active material layer whereby a positive electrode can be obtained.
  • the mass fraction of the positive active material in the positive active material layer is 95%, preferably 96%, and more preferably 97%. In some embodiments, the mass fraction of the positive active material in the positive active material layer is 98%. In some embodiments, the mass fraction of the positive active material in the positive active material layer is 99%. When the mass fraction of the positive active material in the positive active material layer is within the above range, the energy density of the electrochemical device can be significantly improved.
  • the average particle size of the positive electrode active material refers to the primary particle size of the positive electrode active material particle.
  • the average particle diameter of the positive electrode active material particles refers to the secondary particle diameter of the positive electrode active material particles.
  • the average particle size of the positive active material is D ⁇ m, and the value of D ranges from 5 to 30. In some embodiments, D ranges from 10 to 25. In some embodiments, D ranges from 12 to 20. In some embodiments, D is 5, 7, 9, 10, 12, 15, 18, 20, 25, 30 or within a range consisting of any two of the above values.
  • the positive electrode active material with high tap density can be obtained, the reduction of the performance of the electrochemical device can be suppressed, and it can be used in the preparation process of the positive electrode of the electrochemical device (that is, the positive electrode active When materials, conductive materials, adhesives, etc. are slurried with a solvent and coated in a film form), problems such as streaks can be prevented.
  • the filling property during positive electrode preparation can be further improved.
  • the average particle size of the positive electrode active material can be measured by a laser diffraction/scattering particle size distribution measuring device: when using LA-920 manufactured by HORIBA Corporation as a particle size distribution meter, use 0.1% sodium hexametaphosphate aqueous solution as the particle size used in the measurement. The dispersion medium was measured after ultrasonic dispersion for 5 minutes with the measurement refractive index set to 1.24.
  • the average particle size of the positive active material can also be measured by a laser diffraction particle size analyzer (Shimadzu SALD-2300) and a scanning electron microscope (ZEISS EVO18, the number of samples is not less than 100).
  • the electrolytic solution used in the electrochemical device of the present application includes an electrolyte and a solvent for dissolving the electrolyte.
  • the electrolyte solution further includes a compound having a sulfur-oxygen double bond.
  • the compound having a sulfur-oxygen double bond includes at least one of the following compounds: cyclic sulfate, chain sulfate, chain sulfonate, cyclic sulfonate, chain sulfurous acid esters or cyclic sulfites.
  • the cyclic sulfates include, but are not limited to, one or more of the following: 1,2-ethanediol sulfate, 1,2-propanediol sulfate, 1,3-propanediol sulfate ester, 1,2-butanediol sulfate, 1,3-butanediol sulfate, 1,4-butanediol sulfate, 1,2-pentanediol sulfate, 1,3-pentanediol sulfate ester, 1,4-pentanediol sulfate and 1,5-pentanediol sulfate, etc.
  • the chain sulfates include, but are not limited to, one or more of the following: dimethyl sulfate, ethyl methyl sulfate, diethyl sulfate, and the like.
  • the chain sulfonate includes, but is not limited to, one or more of the following: fluorosulfonate such as methyl fluorosulfonate and ethyl fluorosulfonate, methyl methanesulfonate, Ethyl methanesulfonate, butyl dimethanesulfonate, methyl 2-(methylsulfonyloxy)propionate, ethyl 2-(methylsulfonyloxy)propionate, and the like.
  • fluorosulfonate such as methyl fluorosulfonate and ethyl fluorosulfonate
  • methyl methanesulfonate methyl methanesulfonate
  • Ethyl methanesulfonate butyl dimethanesulfonate
  • 2-(methylsulfonyloxy)propionate ethyl 2-(methylsulfonyloxy)propionate
  • the cyclic sulfonate includes, but is not limited to, one or more of the following: 1,3-propane sultone, 1-fluoro-1,3-propane sultone , 2-fluoro-1,3-propane sultone, 3-fluoro-1,3-propane sultone, 1-methyl-1,3-propane sultone, 2-methyl-1 ,3-propane sultone, 3-methyl-1,3-propane sultone, 1-propene-1,3-sultone, 2-propene-1,3-sultone, 1-fluoro-1-propene-1,3-sultone, 2-fluoro-1-propene-1,3-sultone, 3-fluoro-1-propene-1,3-sultone , 1-fluoro-2-propene-1,3-sultone, 2-fluoro-2-propene-1,3-sultone, 3-fluoro-2-propene-1,3-sultone
  • the chain sulfites include, but are not limited to, one or more of the following: dimethyl sulfite, ethyl methyl sulfite, diethyl sulfite, and the like.
  • the cyclic sulfites include, but are not limited to, one or more of the following: 1,2-ethanediol sulfite, 1,2-propanediol sulfite, 1,3 -Propylene glycol sulfite, 1,2-butanediol sulfite, 1,3-butanediol sulfite, 1,4-butanediol sulfite, 1,2-pentanediol sulfite, 1,3-pentanediol sulfite, 1,4-pentanediol sulfite, 1,5-pentanediol sulfite, etc.
  • the compound containing a sulfur-oxygen double bond includes a compound of formula I:
  • Each L is independently selected from a single bond or methylene
  • n 1, 2, 3 or 4;
  • n 0, 1 or 2;
  • p 0, 1, 2, 3, 4, 5 or 6.
  • the compound of formula I includes at least one of the following:
  • the bicyclic sultones include compounds of formula II:
  • a 1 , A 2 , A 3 and A 4 are each independently selected from substituted or unsubstituted C1-3 alkylene, and when substituted, the substituent is selected from C1-5 alkyl, halogen or halogenated C1-5 alkyl.
  • the compound of formula II includes at least one of the following:
  • the content of the compound having a sulfur-oxygen double bond is c%, and the value of c ranges from 0.01 to 5.
  • c is in the range of 0.01-3.
  • c is in the range of 0.1-2.
  • c is 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.8, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 or between any two of the above values. composition range.
  • the content of the compound having a sulfur-oxygen double bond in the electrolyte is within the above range, it is helpful to further improve the high-temperature cycle performance and safety of the electrochemical device.
  • c and a satisfy: 0.5 ⁇ c/a ⁇ 3. In some embodiments, c and a satisfy: 0.8 ⁇ c/a ⁇ 2. In some embodiments, c and a satisfy: 1 ⁇ c/a ⁇ 2.5. In some embodiments, c/a is 0.5, 0.6, 07, 0.8, 1, 1.2, 1.5, 2, 2.5, 3 or within a range consisting of any two of the above values.
  • the electrolyte solution further includes a trinitrile compound.
  • the trinitrile compounds include 1,3,5-pentanetricarbonitrile, 1,2,3-propanetricarbonitrile, 1,3,6-hexanetricarbonitrile, 1,2,6-hexanetricarbonitrile Nitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,2,4-tris(2-cyanoethoxy)butane, 1,1,1-tris(cyanoethyl) oxymethylene)ethane, 1,1,1-tris(cyanoethoxymethylene)propane, 3-methyl-1,3,5-tris(cyanoethoxymethylene)pentane, 1,2,7-tris(cyanoethoxy)heptane, 1,2,6-tris(cyanoethoxy)hexane or 1,2,5-tris(cyanoethoxy)pentane at least one of the
  • the content of the trinitrile compound is d%, and the value of d ranges from 0.01 to 5.
  • d is in the range of 0.01-3.
  • d is in the range of 0.1-2.
  • d is 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.8, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 or between any two of the above values. composition range.
  • the content of the trinitrile compound in the electrolyte is within the above range, it is helpful to further improve the high-temperature cycle performance and safety of the electrochemical device.
  • d and a satisfy: 0.2 ⁇ d/a ⁇ 4. In some embodiments, d and a satisfy: 0.5 ⁇ d/a ⁇ 3.5. In some embodiments, d and a satisfy: 1 ⁇ c/a ⁇ 3.5. In some embodiments, d/a is 0.2, 0.3, 0.5, 0.6, 07, 0.8, 1, 1.2, 1.5, 2, 2.5, 3, 3.5, 4 or within a range consisting of any two of the above values . When the content of the trinitrile compound in the electrolyte and the density of the binder meet the above relationship, it will help to further improve the high-temperature cycle performance and safety of the electrochemical device.
  • the electrolyte also includes succinonitrile, adiponitrile, ethylene glycol bis(2-cyanoethyl) ether, fluoroethylene carbonate, vinylene carbonate or 1-propyl phosphoric acid at least one of the cyclic anhydrides.
  • the content of the above compound is 0.1%-6%.
  • the content of the above compound is 0.5%-5%.
  • the content of the above compound is 1%-3%.
  • the electrolyte solution further comprises any non-aqueous solvent known in the prior art as a solvent for the electrolyte solution.
  • the non-aqueous solvent includes, but is not limited to, one or more of the following: cyclic carbonate, chain carbonate, cyclic carboxylate, chain carboxylate, cyclic Ethers, chain ethers, phosphorus-containing organic solvents, sulfur-containing organic solvents, and aromatic fluorinated solvents.
  • examples of the cyclic carbonate may include, but are not limited to, one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate.
  • the cyclic carbonate has 3-6 carbon atoms.
  • examples of the chain carbonate may include, but are not limited to, one or more of the following: dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate (DEC), methyl carbonate Chain carbonates such as ethyl n-propyl carbonate, ethyl n-propyl carbonate, di-n-propyl carbonate, etc.
  • chain carbonates substituted with fluorine may include, but are not limited to, one or more of the following: bis(fluoromethyl)carbonate, bis(difluoromethyl)carbonate, bis(trifluoromethyl)carbonate base) carbonate, bis(2-fluoroethyl)carbonate, bis(2,2-difluoroethyl)carbonate, bis(2,2,2-trifluoroethyl)carbonate, 2-fluoroethyl methyl carbonate, 2,2-difluoroethyl methyl carbonate and 2,2,2-trifluoroethyl methyl carbonate, etc.
  • examples of the cyclic carboxylate may include, but are not limited to, one or more of the following: one or more of ⁇ -butyrolactone and ⁇ -valerolactone.
  • some of the hydrogen atoms of the cyclic carboxylate may be replaced by fluorine.
  • examples of the chain carboxylate may include, but are not limited to, one or more of the following: methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate ester, sec-butyl acetate, isobutyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, methyl butyrate, ethyl butyrate, butyric acid Propyl ester, methyl isobutyrate, ethyl isobutyrate, methyl valerate, ethyl valerate, methyl pivalate and ethyl pivalate, etc.
  • part of the hydrogen atoms of the chain carboxylate may be substituted by fluorine.
  • examples of fluorine-substituted chain carboxylic acid esters may include, but are not limited to, methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, and trifluoroacetic acid 2,2,2-trifluoroethyl ester, etc.
  • examples of the cyclic ether may include, but are not limited to, one or more of the following: tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 2-methyl 1,3-dioxolane, 4-methyl 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane and dimethoxypropane.
  • examples of the chain ethers may include, but are not limited to, one or more of the following: dimethoxymethane, 1,1-dimethoxyethane, 1,2- Dimethoxyethane, diethoxymethane, 1,1-diethoxyethane, 1,2-diethoxyethane, ethoxymethoxymethane, 1,1-ethoxy Methoxyethane and 1,2-ethoxymethoxyethane, etc.
  • examples of the phosphorus-containing organic solvent may include, but are not limited to, one or more of the following: trimethyl phosphate, triethyl phosphate, dimethyl ethyl phosphate, methyl phosphate Diethyl ester, ethylene methyl phosphate, ethylene ethyl phosphate, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, triphenyl phosphite, tris(2,2,2- phosphate Trifluoroethyl) ester and tris(2,2,3,3,3-pentafluoropropyl) phosphate, etc.
  • examples of the sulfur-containing organic solvent may include, but are not limited to, one or more of the following: sulfolane, 2-methylsulfolane, 3-methylsulfolane, dimethylsulfone, disulfone Ethyl sulfone, ethyl methyl sulfone, methyl propyl sulfone, dimethyl sulfoxide, methyl methanesulfonate, ethyl methanesulfonate, methyl ethanesulfonate, ethyl ethanesulfonate, dimethyl sulfate , diethyl sulfate and dibutyl sulfate.
  • some hydrogen atoms of the sulfur-containing organic solvent may be replaced by fluorine.
  • the aromatic fluorinated solvent includes, but is not limited to, one or more of the following: fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene and trifluoromethylbenzene.
  • the solvent used in the electrolyte of the present application includes cyclic carbonates, chain carbonates, cyclic carboxylates, chain carboxylates, and combinations thereof.
  • the solvent used in the electrolyte of the present application comprises an organic solvent selected from the group consisting of ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, 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 .
  • the electrolyte is not particularly limited, and any known substance as an electrolyte can be used arbitrarily.
  • lithium salts are generally used.
  • electrolytes may include, but are not limited to, inorganic lithium salts such as LiPF 6 , LiBF 4 , LiClO 4 , LiAlF 4 , LiSbF 6 , LiWF 7 ; lithium tungstates such as LiWOF 5 ; HCO 2 Li, CH 3 CO 2 Li, CH 2 FCO 2 Li, CHF 2 CO 2 Li, CF 3 CO 2 Li, CF 3 CH 2 CO 2 Li, CF 3 CF 2 CO 2 Li, CF 3 CF 2 CO 2 Li, CF 3 CF 2 CF 2 CO 2 Li, CF 3 CF 2 CF 2 Lithium carboxylate salts such as CF 2 CO 2 Li; FSO 3 Li, CH 3 SO 3 Li, CH 2 FSO 3 Li, CHF 2 SO 3 Li, CF 3 SO 3 Li, CF 3 CF 2 SO 3 Li, CF 3
  • the electrolyte is selected from LiPF 6 , LiSbF 6 , FSO 3 Li, CF 3 SO 3 Li, LiN(FSO 2 ) 2 , LiN(FSO 2 )(CF 3 SO 2 ), LiN(CF 3 SO 2 ) 2 , LiN(C 2 F 5 SO 2 ) 2 , cyclic lithium 1,2-perfluoroethanebissulfonimide, cyclic lithium 1,3-perfluoropropanebissulfonimide, LiC(FSO 2 ) 3 , LiC(CF 3 SO 2 ) 3 , LiC(C 2 F 5 SO 2 ) 3 , LiBF 3 CF 3 , LiBF 3 C 2 F 5 , LiPF 3 (CF 3 ) 3 , LiPF 3 (C 2 F 5 ) 3.
  • Lithium difluorooxalate borate, lithium bis(oxalate)borate or lithium difluorobis(oxalato)phosphate which help to improve the output power characteristics, high-rate charge 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 effect of the present application is not impaired.
  • the total molar concentration of lithium in the electrolyte is greater than 0.3 mol/L, greater than 0.4 mol/L or greater than 0.5 mol/L.
  • the total molar concentration of lithium in the electrolyte is less than 3 mol/L, less than 2.5 mol/L or less than 2.0 mol/L.
  • the total molar concentration of lithium in the electrolyte is within the range formed by any two values above. When the electrolyte concentration is within the above range, the lithium as charged particles will not be too small, and the viscosity can be kept in an appropriate range, so it is easy to ensure good electrical conductivity.
  • the electrolyte includes at least one salt selected from the group consisting of monofluorophosphate, borate, oxalate and fluorosulfonate.
  • the electrolyte includes a salt selected from the group consisting of monofluorophosphate, oxalate, and fluorosulfonate.
  • the electrolyte includes a lithium salt.
  • the salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate is present at greater than 0.01% or greater than 0.1% by weight of the electrolyte.
  • the salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate comprises less than 20% or less than 10% by weight of the electrolyte. In some embodiments, the content of the salt selected from the group consisting of monofluorophosphate, borate, oxalate and fluorosulfonate is within the range formed by any two of the above values.
  • the electrolyte includes one or more substances selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate and one or more salts other than these.
  • 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 additional salt is LiPF 6
  • the additional salts are present at greater than 0.01% or greater than 0.1% by weight of the electrolyte. In some embodiments, the additional salts are present at less than 20%, less than 15%, or less than 10% by weight of the electrolyte. In some embodiments, the content of other salts is within the range formed by any two values above. Salts other than these having the above content contribute to the balance of the electrical conductivity and viscosity of the electrolytic solution.
  • the negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on one or both surfaces of the negative electrode current collector, and the negative electrode active material layer contains the negative electrode active material.
  • the negative electrode active material layer may be one or more layers, and each layer of the multilayer negative electrode active material may contain the same or different negative electrode active materials.
  • the negative electrode active material is any material capable of reversibly intercalating and deintercalating metal ions such as lithium ions.
  • the chargeable capacity of the negative active material is greater than the discharge capacity of the positive active material, so as to prevent unintentional precipitation of lithium metal on the negative electrode during charging.
  • any known current collector can be used arbitrarily.
  • negative electrode current collectors include, but are not limited to, metal materials such as aluminum, copper, nickel, stainless steel, and nickel-plated steel. In some embodiments, the negative current collector is copper.
  • the form of the negative electrode current collector may include, but is not limited to, metal foil, metal cylinder, metal strip, metal plate, metal film, expanded metal, stamped metal, foamed metal, etc.
  • the negative electrode current collector is a metal film.
  • the negative electrode current collector is copper foil.
  • the negative electrode current collector is a rolled copper foil based on a rolling method or an electrolytic copper foil based on an electrolytic method.
  • the thickness of the negative electrode current collector is greater than 1 ⁇ m or greater than 5 ⁇ m. In some embodiments, the thickness of the negative electrode current collector is less than 100 ⁇ m or less than 50 ⁇ m. In some embodiments, the thickness of the negative electrode current collector is within the range formed by any two values above.
  • the negative electrode active material is not particularly limited as long as it can reversibly store and release lithium ions.
  • Examples of negative electrode active materials may include, but are not limited to, carbon materials such as natural graphite and artificial graphite; metals such as silicon (Si) and tin (Sn); or oxides of metal elements such as Si and Sn.
  • the negative electrode active materials can be used alone or in combination.
  • the negative active material layer may further include a negative binder.
  • the negative electrode binder can improve the combination of the negative electrode active material particles and the combination of the negative electrode active material and the current collector.
  • the type of negative electrode binder is not particularly limited, as long as it is a material stable to the electrolyte solution or the solvent used in electrode production.
  • the negative binder includes a resin binder.
  • resin binders include, but are not limited to, fluororesins, polyacrylonitrile (PAN), polyimide resins, acrylic resins, polyolefin resins, and the like.
  • the negative electrode binder When using a water-based solvent to prepare the negative electrode mixture slurry, the negative electrode binder includes, but is not limited to, carboxymethyl cellulose (CMC) or its salt, styrene-butadiene rubber (SBR), polyacrylic acid (PAA) or Its salt, polyvinyl alcohol, etc.
  • CMC carboxymethyl cellulose
  • SBR styrene-butadiene rubber
  • PAA polyacrylic acid
  • Its salt polyvinyl alcohol, etc.
  • the negative electrode can be prepared by the following method: coating the negative electrode mixture slurry comprising negative electrode active material, resin binder, etc. on the negative electrode current collector, after drying, calendering to form negative electrode active material layers on both sides of the negative electrode current collector, thus Negative pole is available.
  • a separator is usually provided between the positive electrode and the negative electrode.
  • the electrolytic solution of the present application is usually used by permeating the separator.
  • the material and shape of the separator are not particularly limited as long as the effect of the present application is not significantly impaired.
  • the separator can be resin, glass fiber, inorganic material, etc. formed of materials stable to the electrolyte solution of the present application.
  • the separator includes a porous sheet or a non-woven fabric-like substance with excellent liquid retention properties.
  • the material of the resin or fiberglass separator may include, but are not limited to, polyolefin, aramid, polytetrafluoroethylene, polyethersulfone, and the like.
  • the polyolefin is polyethylene or polypropylene.
  • the polyolefin is polypropylene.
  • the materials for the above separators can be used alone or in any combination.
  • the isolation film can also be a material formed by laminating the above materials, examples of which include, but not limited to, a three-layer isolation film formed by laminating polypropylene, polyethylene, and polypropylene in this order.
  • Examples of materials of inorganic substances may include, but are not limited to, oxides such as aluminum oxide and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, sulfates (eg, barium sulfate, calcium sulfate, etc.).
  • Inorganic forms may include, but are not limited to, granular or fibrous.
  • the form of the separator may be in the form of a film, examples of which include, but are not limited to, non-woven fabrics, woven fabrics, microporous films, and the like.
  • the pore diameter of the isolation membrane is 0.01 ⁇ m to 1 ⁇ m, and the thickness is 5 ⁇ m to 50 ⁇ m.
  • the following separator can also be used: a separator formed by forming a composite porous layer containing the above-mentioned inorganic particles on the surface of the positive electrode and/or negative electrode using a resin-based binder,
  • a separator is formed by using a fluororesin as a binder to form porous layers on both sides of the positive electrode with 90% of the alumina particles having a particle size of less than 1 ⁇ m.
  • the thickness of the separator is arbitrary. In some embodiments, the thickness of the isolation film is greater than 1 ⁇ m, greater than 5 ⁇ m, or greater than 8 ⁇ m. In some embodiments, the thickness of the isolation film is less than 50 ⁇ m, less than 40 ⁇ m or less than 30 ⁇ m. In some embodiments, the thickness of the isolation film is within the range formed by any two values above. When the thickness of the separator is within the above range, insulation and mechanical strength can be ensured, and rate characteristics and energy density of the electrochemical device can be ensured.
  • the porosity of the separator is arbitrary.
  • the isolation membrane has a porosity greater than 10%, greater than 15%, or greater than 20%.
  • the separator has a porosity of less than 60%, less than 50%, or less than 45%.
  • the porosity of the isolation membrane is within the range formed by any two values above. When the porosity of the separator is within the above range, insulation and mechanical strength can be ensured, and membrane resistance can be suppressed, so that the electrochemical device has good safety characteristics.
  • the average pore diameter of the separator is also arbitrary. In some embodiments, the average pore size of the isolation membrane is less than 0.5 ⁇ m or less than 0.2 ⁇ m. In some embodiments, the average pore size of the isolation membrane is greater than 0.05 ⁇ m. In some embodiments, the average pore diameter of the isolation membrane is within the range formed by any two values above. When the average pore diameter of the separator exceeds the above-mentioned range, short circuits are likely to occur. When the average pore diameter of the isolation membrane is within the above range, the electrochemical device has good safety characteristics.
  • the electrochemical device assembly includes an electrode group, a current collecting structure, an outer casing and a protection element.
  • the electrode group may have either a laminated structure in which the positive electrode and the negative electrode are laminated with the separator interposed therebetween, or a structure in which the positive electrode and the negative electrode are wound in a spiral shape with the separator interposed therebetween.
  • the ratio of the mass of the electrode group to the internal volume of the battery is greater than 40% or greater than 50%.
  • the electrode set occupancy is less than 90% or less than 80%.
  • the occupancy of the electrode group is within the range formed by any two values above. When the electrode group occupancy ratio is within the above range, the capacity of the electrochemical device can be ensured, and at the same time, the decrease in characteristics such as repeated charge-discharge performance and high-temperature storage due to an increase in internal pressure can be suppressed.
  • the current collecting structure is not particularly limited. In some embodiments, the current collecting structure is a structure that reduces the resistance of the wiring portion and the bonding portion.
  • the electrode group has the above-mentioned laminated structure, it is suitable to use a structure in which the metal core portions of the electrode layers are bundled and welded to the terminal.
  • the internal resistance increases, so it is also suitable to provide two or more terminals in the electrode to reduce the resistance.
  • the electrode group has the above-mentioned winding structure, the internal resistance can be reduced by providing two or more lead wire structures on the positive electrode and the negative electrode respectively, and bundling them on the terminals.
  • the material of the outer case is not particularly limited, as long as it is stable to the electrolyte solution used.
  • metals such as nickel-plated steel sheets, stainless steel, aluminum or aluminum alloys, and magnesium alloys, or laminated films of resin and aluminum foil can be used, but not limited to.
  • the outer casing is aluminum or aluminum alloy metal or a laminated film.
  • Metal exterior cases include, but are not limited to, encapsulation and sealing structures formed by welding metals together by laser welding, resistance welding, or ultrasonic welding; or riveted structures using the above-mentioned metals through resin spacers.
  • the exterior case using the above-mentioned laminated film includes, but is not limited to, a package sealing structure formed by thermally bonding resin layers to each other, and the like. In order to improve the sealability, a resin different from the resin used in the laminated film may be interposed between the above-mentioned resin layers.
  • a resin having a polar group or a modified resin into which a polar group is introduced can be used as the interposed resin due to the bonding between the metal and the resin.
  • the shape of the exterior body is also arbitrary, and for example, any of cylindrical, square, laminated, button-shaped, large, and the like may be used.
  • Protection elements can use positive temperature coefficient (PTC) whose resistance increases when abnormal heat generation or excessive current flows, temperature fuses, thermistors, cut off by causing the internal pressure of the battery or the internal temperature to rise sharply at the time of abnormal heat generation A valve (current cut-off valve) for the current flowing in the circuit, etc.
  • PTC positive temperature coefficient
  • the above-mentioned protection elements can be selected under the condition that they do not work in the normal use of high current, and can also be designed in such a way that abnormal heat dissipation or thermal runaway will not occur even if there is no protection element.
  • the electrochemical device of the present application includes any device that undergoes an electrochemical reaction, and specific examples thereof include a lithium metal secondary battery or a lithium ion secondary battery.
  • the present application further provides an electronic device, which includes the electrochemical device according to the present application.
  • the application of the electrochemical device of the present application is not particularly limited, and it can be used in any electronic device known in the prior art.
  • the electrochemical device of the present application can be used in, but not limited to, notebook computers, pen-based computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-worn Stereo headphones, VCRs, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic organizers, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, automobiles, motorcycles, power assist Bicycles, bicycles, lighting equipment, toys, game consoles, clocks, electric tools, flashlights, cameras, large household storage batteries and lithium-ion capacitors, etc.
  • the lithium ion battery is taken as an example below and the preparation of the lithium ion battery is described in conjunction with specific examples. Those skilled in the art will understand that the preparation method described in this application is only an example, and any other suitable preparation methods are described in this application. within range.
  • Co 3 O 4 and LiOH powders were weighed, thoroughly mixed and ground in an agate mortar, and then calcined at 900° C. for 10 hours. Add oxides, sulfates or nitrates with the first element in a specific metered ratio to the calcined mixture, and use alcohol as a solvent. After ball milling for 10 hours, calcinate at 800°C for 10 hours to obtain the first element. Lithium Cobalt Oxide.
  • the positive electrode active material (with/without lithium cobaltate of the first element), carbon nanotubes and polyvinylidene fluoride is mixed with N-methylpyrrolidone (NMP) according to the mass ratio of 97:1:2, and stirred evenly to obtain Positive slurry.
  • NMP N-methylpyrrolidone
  • the positive electrode slurry was coated on a 12 ⁇ m aluminum foil, dried, cold pressed, cut into pieces, and tabs were welded to obtain a positive electrode.
  • a polyethylene porous polymer film is used as a separator.
  • the electrolyte solution is poured from the liquid injection port, packaged, and then the lithium-ion battery is produced through processes such as formation and capacity.
  • the lithium-ion battery was charged to 4.7V with a constant current of 1C, then charged at a constant voltage of 4.7V to a current of 0.05C, and then discharged to 3.0V at a constant current of 1C. This was the first cycle.
  • the lithium-ion battery was subjected to 500 cycles according to the above conditions. "1C" refers to the current value that fully discharges the battery capacity within 1 hour.
  • the capacity retention rate of the lithium-ion battery after cycling is calculated by the following formula:
  • Capacity retention rate after cycle (discharge capacity after cycle/discharge capacity in first cycle) ⁇ 100%.
  • the lithium-ion battery was then short-circuited at 100 m ⁇ for 10 seconds, and then the thickness T 2 of the lithium-ion battery was measured.
  • the high-temperature short-circuit deformation rate of lithium-ion batteries is calculated by the following formula:
  • Short-circuit deformation rate [(T 2 -T 1 )/T 1 ] ⁇ 100%.
  • Table 1 shows the impact of positive active materials and binders on the high-temperature cycle performance and safety of lithium-ion batteries.
  • the positive electrode active material is lithium cobaltate containing/not containing the first element.
  • Comparative Example 1-1 when the positive electrode active material is not doped, even if the low-density positive electrode binder of the present application is used, the lithium-ion battery has a lower high-temperature cycle capacity retention rate and a higher short-circuit deformation rate .
  • Comparative Examples 1-2 and 1-3 when the positive electrode active material includes at least one doping element in aluminum, magnesium, titanium, zirconium or tungsten but the density of the positive electrode binder is too high (greater than 1.5g/cm 3 ) or too low (less than 0.6g/cm 3 ), the lithium-ion battery still has a low high-temperature cycle capacity retention rate and a high short-circuit deformation rate.
  • the positive electrode active material includes at least one doping element in aluminum, magnesium, titanium, zirconium or tungsten and the positive electrode binder has a density of 0.6-1.5 g/ cm , can significantly improve the high-temperature cycle capacity retention rate of lithium-ion batteries and significantly reduce their short-circuit deformation rate.
  • Table 2 shows the effect of binder porosity and its relationship with density on the high-temperature cycle performance and safety of Li-ion batteries. Except for the parameters listed in Table 2, the settings of Examples 2-1 to 2-16 are the same as those of Example 1-1.
  • Table 3 shows the influence of the content of aluminum and tungsten in the positive active material on the high-temperature cycle performance and safety of lithium-ion batteries. Except for the parameters listed in Table 3, the settings of Examples 3-1 to 3-9 are the same as those of Example 1-1.
  • the positive electrode active material includes aluminum and tungsten elements and the aluminum content x% and tungsten content y% satisfy 1 ⁇ x/y ⁇ 5, the high-temperature cycle capacity retention rate of the lithium-ion battery can be further improved and its short-circuit deformation rate can be reduced .
  • Table 4 shows the influence of the relationship between the content of aluminum in the positive electrode active material and the density of the binder on the high-temperature cycle performance and safety of the lithium-ion battery. Except for the parameters listed in Table 4, the settings of Examples 4-1 to 4-10 are the same as those of Example 1-1.
  • the positive electrode active material includes aluminum and the aluminum content x% and the binder density a g/ cm3 meet 0.2 ⁇ x/a ⁇ 1, the high-temperature cycle capacity retention rate of the lithium-ion battery can be further improved and its short circuit can be reduced Deformation rate.
  • Table 5 shows the influence of compounds with sulfur-oxygen double bonds in the electrolyte and their relationship with the binder density on the high-temperature cycle performance and safety of lithium-ion batteries. Except for the parameters listed in Table 5, the settings of Examples 5-1 to 5-14 are the same as those of Example 1-1.
  • the high-temperature cycle capacity retention rate of the lithium-ion battery can be further improved and reduced Its short-circuit deformation rate.
  • Table 6 shows the effect of the trinitrile compound in the electrolyte and its relationship with the binder density on the high-temperature cycle performance and safety of lithium-ion batteries. Except for the parameters listed in Table 6, the settings of Examples 6-1 to 6-14 are the same as those of Example 1-1.
  • the electrolyte also includes 0.01%-5% of the trinitrile compound, the high-temperature cycle capacity retention rate of the lithium-ion battery can be further improved and the short-circuit deformation rate can be reduced.
  • the high-temperature cycle capacity retention rate of the lithium-ion battery can be further improved and reduced Its short-circuit deformation rate.
  • Table 7 shows the effects of additives in the electrolyte on the high-temperature cycle performance and safety of lithium-ion batteries. Except for the parameters listed in Table 7, the settings of Examples 7-1 to 7-10 are the same as those of Example 1-1.
  • the electrolyte contains at least In one case, the high-temperature cycle capacity retention rate of lithium-ion batteries can be further improved and the short-circuit deformation rate can be reduced.
  • references to “embodiment”, “partial embodiment”, “an embodiment”, “another example”, “example”, “specific example” or “partial example” in the entire specification mean that At least one embodiment or example in the present application includes a specific feature, structure, material or characteristic described in the embodiment or example.
  • descriptions that appear throughout the specification such as: “in some embodiments”, “in an embodiment”, “in one embodiment”, “in another example”, “in an example In”, “in a particular example” or “example”, they are not necessarily referring to the same embodiment or example in this application.
  • the particular features, structures, materials, or characteristics herein may be combined in any suitable manner in one or more embodiments or examples.

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Abstract

本申请涉及一种电化学装置和电子装置。具体而言，本申请提供一种电化学装置，其包括：正极、负极和电解液，所述正极包括正极集流体和形成在所述正极集流体上的正极活性物质层，所述正极活性物质层包括正极活性物质和低密度粘结剂，其中所述正极活性物质具有第一元素，所述第一元素包括铝、镁、钛、锆或钨中的至少一种。本申请的电化学装置具有改善的高温循环性能和安全性。

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，随着智能手机、平板电脑和智能穿戴等电子产品的快速发展，考虑到电子产品的使用时长和工作环境的不同，消费者对锂离子电池的能量密度的要求越来越高。目前，主要通过采用高电压(4.4V及以上)的钴酸锂正极活性物质和高容、高压实密度的石墨负极材料来提高锂离子电池的能量密度。然而，随着温度和电压的升高，这类锂离子电池的循环性能和安全性会明显恶化。同时，随着全球变暖的恶劣环境加剧(如面对印度、非洲等特殊使用地区)，这对电池的高温性能提出了更高的要求。
有鉴于此，确有必要提供一种具有改进的高温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善的高温循环性能和安全性的电化学装置和电子装置以在某种程度上解决存在于现有技术的问题。
在本申请的一方面，本申请提供一种电化学装置，其包括：正极、负极和电解液，所述正极包括正极集流体和形成在所述正极集流体上的正极活性物质层，所述正极活性物质层包括正极活性物质和粘结剂，其中：所述正极活性物质具有第一元素，所述第一元素包括铝、镁、钛、锆或钨中的至少一种，并且所述粘结剂的密度为a g/cm 3，a的取值范围为0.6至1.5。
根据本申请的实施例，a的取值范围为0.6至1.2、0.7至1.0或0.7至0.9。
根据本申请的实施例，所述粘结剂的孔隙率为b％，b的取值范围为20至50，且a和b满足：17≤a×b≤60。
根据本申请的实施例，所述粘结剂包括含氟聚合物，优选聚偏氟乙烯。
根据本申请的实施例，所述电化学装置满足如下中的至少一者：
a.所述第一元素包括铝以及镁、钛、锆或钨中的至少一种；
b.所述第一元素包括钨以及镁、钛、锆或铝中的至少一种；
c.所述第一元素包括铝和钨，基于所述正极活性物质的重量，铝和钨的含量分别为x％和y％，x和y满足：1≤x/y≤5；
d.基于所述正极活性物质的重量，所述第一元素的含量为0.01至2％。
根据本申请的实施例，所述第一元素包括铝，基于所述正极活性物质的重量，铝的含量为x％，且x和a满足0.2≤x/a≤1。
根据本申请的实施例，所述电解液包括具有硫氧双键的化合物，基于所述电解液的重量，所述具有硫氧双键的化合物的含量为c％，c的取值范围为0.01至5。
根据本申请的实施例，c和a满足：0.5≤c/a≤3。
根据本申请的实施例，所述电解液包括三腈化合物，基于所述电解液的重量，所述三腈化合物的含量为d％，d的取值范围为0.01至5。
根据本申请的实施例，d和a满足：0.2≤d/a≤4。
根据本申请的实施例，所述电解液包括丁二腈、己二腈、乙二醇二(2-氰基乙基)醚、氟代碳酸乙烯酯、碳酸亚乙烯酯或1-丙基磷酸环酐中的至少一种。
在本申请的另一方面，本申请提供一种电子装置，其包括根据本申请的电化学装置。
本申请使用的含掺杂元素的正极活性物质和低密度粘结剂的组合有效地改善了正极的界面稳定性，由此显著改善了电化学装置的高温循环性能和安全性。
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。
I、正极
常用的提高电化学装置(例如，锂离子电池)的能量密度的方法包括采用高电压(4.4V及以上)的钴酸锂正极活性物质和高容量、高压实密度的石墨负极材料。然而，随着温度和电压的升高，钴酸锂的结构稳定性变差，金属离子易从正极溶出并在负极表面还原沉积，从而破坏负极固体电解质界面(SEI)膜的结构，导致负极阻抗和电池厚度不断增大，从而导致锂离子电池的容量损失和循环性能的劣化。此外，在高温和高压下，电解液容易在正极表面发生氧化分解产生大量的气体，从而导致锂离子电池鼓胀和电极界面破坏，从而恶化锂离子电池性能。同时，在高温高电压下，由于钴酸锂的氧化活性较高，其与电解液之间的副反应加剧，使得电解液的分解产物在正极表面不断沉积，这会进一步增大锂离子电池的内阻，从而不利影响锂离子电池的高温循性能。这些因素还使得锂离子电池存在极大的安全隐患。
业界通常在正极活性物质(如钴酸锂或三元材料)中使用铝、镁、钛、锆或钨掺杂，其中铝和镁元素更容易掺杂进入材料的晶体结构中，而钛和锆元素则倾向于在颗粒表面富集，钨元素用来提高导电性。然而，尚未发现这些元素用于改善电化学装置的安全性的报道。此外，目前在正极浆料中使用的粘结剂密度大都在1.7g/cm 3以上。基于已有的认知，无法预料到同时使用包括铝、镁、钛、锆或钨中的至少一种的正极活性物质和低密度粘结剂会对电化学装置的高温循环和安全性能提升发挥重要作用。
本申请通过使用包括含有铝、镁、钛、锆或钨中的至少一种的正极活性物质以及低密度粘结剂意外解决了电化学装置的高温循环和安全性能的相关问题。在正极活性物质中掺杂铝、镁、钛、锆或钨中的至少一种元素可有效地提高晶格稳定性，从而抑制在高温或低温条件下充放电循环中的颗粒的体积变化，以减少颗粒裂纹、破碎，同时其还可提高正极的界面稳定性。低密度粘结剂可实现良好粘结效果，同时在制备正极过程中受压实密度的影响较小，有助于提高正极的表面性能。本申请的正极活性物质与粘结剂的特定组合不仅能够有效地改善电化学装置的高温循环性能，还可以显著提升电化学装置的安全性(例如，短路安全性和 热滥用安全性等)。
正极包括正极集流体和形成在所述正极集流体上的正极活性物质层。正极活性物质层可以是一层或多层。正极活性物质层包括正极活性物质，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。
本申请的电化学装置的主要特征在于：所述正极活性物质层包括正极活性物质和粘结剂，所述正极活性物质具有第一元素，所述第一元素包括铝、镁、钛、锆或钨中的至少一种，并且所述粘结剂的密度为a g/cm 3，a的取值范围为0.6至1.5。在一些实施例中，a的取值范围为0.6至1.2。在一些实施例中，a的取值范围为0.7至1.0。在一些实施例中，a的取值范围为0.7至0.9。
电池领域常用的正极粘结剂的密度通常大于1.7g/cm 3，以保证其具有足够的粘结力。然而，本申请发明人出乎意料地发现，当正极粘结剂的密度大于1.5g/cm 3时，会在一定程度上影响正极的柔韧性，使其在卷绕过程中易发生断裂；当正极粘结剂的密度小于0.6g/cm 3时，粘结剂的粘结力不足，从而不利影响电化学装置的电化学稳定性。且所述正极粘结剂具有较多的孔结构，有利于改善电极的强度和加速电解液的浸润。将正极粘结剂的密度控制在上述范围内时，不仅可实现良好的粘结性，还有助于显著提升电化学装置的高温循环性能和安全性。
在一些实施例中，所述粘结剂的孔隙率为b％，b的取值范围为20至50。在一些实施例中，b的取值范围为25至45。在一些实施例中，b为20、22、25、30、35、40、45、50或在由上述任意两个数值所组成的范围内。当粘结剂的孔隙率在上述范围内时，有助于进一步提升电化学装置的高温循环性能和安全性。
在一些实施例中，a和b满足：17≤a×b≤60。在一些实施例中，a和b满足如下关系：20≤a×b≤50。在一些实施例中，a×b为17、18、19、20、25、30、35、40、45、50、55、60或在由上述任意两个数值所组成的范围内。当粘结剂的密度和孔隙率满足上述关系时，有助于进一步提升电化学装置的高温循环性能和安全性。
在一些实施例中，所述粘结剂包括含氟聚合物。在一些实施例中，所述含氟聚合物包括聚偏氟乙烯。
在一些实施例中，基于所述正极活性物质的重量，所述第一元素的含量为0.01至2％。在一些实施例中，基于所述正极活性物质的重量，所述第一元素的含量为0.05至1％。在一些实施例中，基于所述正极活性物质的重量，所述第一 元素的含量为0.1至0.5％。在一些实施例中，基于所述正极活性物质的重量，所述第一元素的含量为0.01％、0.05％、0.1％、0.5％、1％、2％或在由上述任意两个数值所组成的范围内。当正极活性物质中第一元素的含量满足上述关系时，可以减少正极活性物质晶体结构的表面缺陷，有效抑制电化学装置充放电循环中正极表面钝化层的不断破坏，减少修复次数，充分改善正极活性物质层的界面稳定性，从而进一步提升电化学装置的高温循环性能和安全性。
在一些实施例中，所述第一元素包括铝、镁、钛、锆或钨中的至少两种。在这种情况下，正极活性物质在高温高压下具有更高的稳定性，其与低密度粘结剂的组合可进一步提升电化学装置的高温循环性能和安全性。
在一些实施例中，所述第一元素进一步包括铝以及镁、钛、锆或钨中的至少一种。
在一些实施例中，所述第一元素进一步包括钨以及镁、钛、锆或铝中的至少一种。
在一些实施例中，所述第一元素包括铝和钨，基于所述正极活性物质的重量，铝和钨的含量分别为x％和y％，x和y满足：1≤x/y≤5。在一些实施例中，x和y满足如下关系：1.5≤x/y≤4.5。在一些实施例中，x/y为1、1.5、2、2.5、3、3.5、4、4.5、5或在由上述任意两个数值所组成的范围内。当正极活性物质中铝和钨的含量满足上述关系时，可以减少电化学装置循环过程中正极表面钝化层的分解和再生，充分改善正极活性物质层的界面稳定性，有助于进一步提升电化学装置的高温循环性能和安全性。
在一些实施例中，所述第一元素包括铝，基于所述正极活性物质的重量，铝的含量为x％，且x和a满足0.2≤x/a≤1。在一些实施例中，x/a为0.2、0.3、0.4、0.5、0.6、0.7、0.8、0.9、1或在由上述任意两个数值所组成的范围内。当正极活性物质中铝的含量和粘结剂密度满足上述关系时，可以减少电化学装置循环过程中正极表面钝化层的分解和再生，充分改善正极活性物质层的界面稳定性，有助于进一步提升电化学装置的高温循环性能和安全性。
在一些实施例中，其中x的取值范围为0.01至1。在一些实施例中，x的取值范围为0.05至0.5。在一些实施例中，x的取值范围为0.1至0.3。在一些实施例中，x为0.01、0.05、0.1、0.2、0.3、0.4、0.5、0.6、0.7、0.8、0.9、1或在由上述任意两个数值所组成的范围内。
在一些实施例中，其中y的取值范围为0.01至1。在一些实施例中，y的取值范围为0.05至0.5。在一些实施例中，y的取值范围为0.1至0.3。在一些实施例中，y为0.01、0.05、0.1、0.2、0.3、0.4、0.5、0.6、0.7、0.8、0.9、1或在由上述任意两个数值所组成的范围内。
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，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。通过在正极活性物质表面附着物质，可以抑制正极活性物质表面的电解液的氧化反应，可以提高电化学装置的寿命。当表面附着物质的量过少时，其效果无法充分表现；当表面附着物质的量过多时，会阻碍锂离子的出入，因而电阻有时会增加。本申请中，将在正极活性物质的表面附着有与其组成不同的物质的正极活性物质也称为“正极活性物质”。
在一些实施例中，所述正极活性物质包括钴酸锂或镍钴锰酸锂中的至少一种。
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。
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。
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。
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。
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。
在一些实施例中，所述正极活性物质层中所述正极活性物质的质量分数为95％，优选为96％，进一步优选为97％。在一些实施例中，所述正极活性物质层中所述正极活性物质的质量分数为98％。在一些实施例中，所述正极活性物质层中所述正极活性物质的质量分数为99％。当正极活性物质层中所述正极活性物质的质量分数在上述范围内时，可显著提高电化学装置的能量密度。
当正极活性物质为一次颗粒时，正极活性物质的平均粒径指的是正极活性物 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平均粒径指的是正极活性物质颗粒二次粒径。
在一些实施例中，正极活性物质的平均粒径为Dμm，D的取值范围为5至30。在一些实施例中，其中D的取值范围为10至25。在一些实施例中，D的取值范围为12至20。在一些实施例中，D为5、7、9、10、12、15、18、20、25、30或在由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粒径在上述范围内时，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，并且可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)，防止条纹产生等问题。通过将具有不同平均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。
正极活性物质的平均粒径可利用激光衍射/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。正极活性物质的平均粒径也可以由激光衍射式粒度分析测量仪(岛津SALD-2300)及扫面电镜(ZEISS EVO18，取样数不少于100个)测得。
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，所述电解液还包括具有硫氧双键的化合物。
在一些实施例中，所述具有硫氧双键的化合物包括以下化合物中的至少一者：环状硫酸酯、链状硫酸酯、链状磺酸酯、环状磺酸酯、链状亚硫酸酯或环状亚硫酸酯。
在一些实施例中，所述环状硫酸酯包括，但不限于，以下的一种或多种：1,2-乙二醇硫酸酯、1,2-丙二醇硫酸酯、1,3-丙二醇硫酸酯、1,2-丁二醇硫酸酯、1,3-丁二醇硫酸酯、1,4-丁二醇硫酸酯、1,2-戊二醇硫酸酯、1,3-戊二醇硫酸酯、1,4-戊二醇硫酸酯和1,5-戊二醇硫酸酯等。
在一些实施例中，所述链状硫酸酯包括，但不限于，以下的一种或多种：硫酸二甲酯、硫酸甲乙酯和硫酸二乙酯等。
在一些实施例中，所述链状磺酸酯包括，但不限于，以下的一种或多种：氟 磺酸甲酯和氟磺酸乙酯等氟磺酸酯、甲磺酸甲酯、甲磺酸乙酯、二甲磺酸丁酯、2-(甲磺酰氧基)丙酸甲酯和2-(甲磺酰氧基)丙酸乙酯等。
在一些实施例中，所述环状磺酸酯包括，但不限于，以下的一种或多种：1,3-丙磺酸内酯、1-氟-1,3-丙磺酸内酯、2-氟-1,3-丙磺酸内酯、3-氟-1,3-丙磺酸内酯、1-甲基-1,3-丙磺酸内酯、2-甲基-1,3-丙磺酸内酯、3-甲基-1,3-丙磺酸内酯、1-丙烯-1,3-磺酸内酯、2-丙烯-1,3-磺酸内酯、1-氟-1-丙烯-1,3-磺酸内酯、2-氟-1-丙烯-1,3-磺酸内酯、3-氟-1-丙烯-1,3-磺酸内酯、1-氟-2-丙烯-1,3-磺酸内酯、2-氟-2-丙烯-1,3-磺酸内酯、3-氟-2-丙烯-1,3-磺酸内酯、1-甲基-1-丙烯-1,3-磺酸内酯、2-甲基-1-丙烯-1,3-磺酸内酯、3-甲基-1-丙烯-1,3-磺酸内酯、1-甲基-2-丙烯-1,3-磺酸内酯、2-甲基-2-丙烯-1,3-磺酸内酯、3-甲基-2-丙烯-1,3-磺酸内酯、1,4-丁磺酸内酯、1,5-戊磺酸内酯、甲烷二磺酸亚甲酯和甲烷二磺酸亚乙酯等。
在一些实施例中，所述链状亚硫酸酯包括，但不限于，以下的一种或多种：亚硫酸二甲酯、亚硫酸甲乙酯和亚硫酸二乙酯等。
在一些实施例中，所述环状亚硫酸酯包括，但不限于，以下的一种或多种：1,2-乙二醇亚硫酸酯、1,2-丙二醇亚硫酸酯、1,3-丙二醇亚硫酸酯、1,2-丁二醇亚硫酸酯、1,3-丁二醇亚硫酸酯、1,4-丁二醇亚硫酸酯、1,2-戊二醇亚硫酸酯、1,3-戊二醇亚硫酸酯、1,4-戊二醇亚硫酸酯和1,5-戊二醇亚硫酸酯等。
在一些实施例中，所述含硫氧双键的化合物包括式I化合物：
Figure PCTCN2021142399-appb-000001
其中：
W选自
Figure PCTCN2021142399-appb-000002
L各自独立地选自单键或亚甲基；
m为1、2、3或4；
n为0、1或2；且
p为0、1、2、3、4、5或6。
在一些实施例中，所述式I化合物包括以下中的至少一种：
Figure PCTCN2021142399-appb-000003
在一些实施例中，所述双环磺内酯包括式II化合物：
Figure PCTCN2021142399-appb-000004
其中A 1、A 2、A 3和A 4各自独立地选自经取代或未经取代的C1-3亚烷基，当经取代时，取代基选自C1-5烷基、卤素或卤代C1-5烷基。
在一些实施例中，所述式II化合物包括以下中的至少一种：
Figure PCTCN2021142399-appb-000005
Figure PCTCN2021142399-appb-000006
在一些实施例中，基于所述电解液的重量，所述具有硫氧双键的化合物的含量为c％，c的取值范围为0.01至5。在一些实施例中，c在0.01至3的范围内。在一些实施例中，c在0.1至2的范围内。在一些实施例中，c为0.01、0.05、0.1、0.2、0.3、0.4、0.5、0.8、1、1.5、2、2.5、3、3.5、4、4.5、5或在由上述任意两个数值所组成的范围内。当电解液中具有硫氧双键的化合物的含量在上述范围内时，有助于进一步改善电化学装置的高温循环性能和安全性。
在一些实施例中，c和a满足：0.5≤c/a≤3。在一些实施例中，c和a满足：0.8≤c/a≤2。在一些实施例中，c和a满足：1≤c/a≤2.5。在一些实施例中，c/a为0.5、0.6、07、0.8、1、1.2、1.5、2、2.5、3或在由上述任意两个数值所组成的范围内。当电解液中具有硫氧双键的化合物的含量和粘结剂的密度满足上述关系时，有助于进一步改善电化学装置的高温循环性能和安全性。
在一些实施例中，所述电解液还包括三腈化合物。
在一些实施例中，所述三腈化合物包括1,3,5-戊三甲腈、1,2,3-丙三甲腈、1,3,6-己三甲腈、1,2,6-己三甲腈、1,2,3-三(2-氰基乙氧基)丙烷、1,2,4-三(2-氰基乙氧基)丁烷、1,1,1-三(氰基乙氧基亚甲基)乙烷、1,1,1-三(氰基乙氧基亚甲基)丙烷、3-甲基-1,3,5-三(氰基乙氧基)戊烷、1,2,7-三(氰基乙氧基)庚烷、1,2,6-三(氰基乙氧基)己烷或1,2,5-三(氰基乙氧基)戊烷中的至少一种。
在一些实施例中，基于所述电解液的重量，所述三腈化合物的含量为d％，d的取值范围为0.01至5。在一些实施例中，d在0.01至3的范围内。在一些实施例中，d在0.1至2的范围内。在一些实施例中，d为0.01、0.05、0.1、0.2、0.3、0.4、0.5、0.8、1、1.5、2、2.5、3、3.5、4、4.5、5或在由上述任意两个数值所组成的范围内。当电解液中三腈化合物的含量在上述范围内时，有助于进一步改善电化学装置的高温循环性能和安全性。
在一些实施例中，d和a满足：0.2≤d/a≤4。在一些实施例中，d和a满足：0.5≤d/a≤3.5。在一些实施例中，d和a满足：1≤c/a≤3.5。在一些实施例中，d/a为0.2、0.3、0.5、0.6、07、0.8、1、1.2、1.5、2、2.5、3、3.5、4或在由上述任 意两个数值所组成的范围内.当电解液中三腈化合物的含量和粘结剂的密度满足上述关系时，有助于进一步改善电化学装置的高温循环性能和安全性。
在一些实施例中，所述电解液还包括丁二腈、己二腈、乙二醇二(2-氰基乙基)醚、氟代碳酸乙烯酯、碳酸亚乙烯酯或1-丙基磷酸环酐中的至少一种。在一些实施例中，基于所述电解液的质量，上述化合物的含量为0.1％-6％。在一些实施例中，基于所述电解液的质量，上述化合物的含量为0.5％-5％。在一些实施例中，基于所述电解液的质量，上述化合物的含量为1％-3％。这些化合物有助于稳定正极和电解液的界面，从而进一步改善电化学装置在高温高压下的循环性能和安全性。
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。
在一些实施例中，电解质没有特别限制，可以任意地使用作为电解质公知的 物质。在锂二次电池的情况下，通常使用锂盐。电解质的实例可包括，但不限于，LiPF 6、LiBF 4、LiClO 4、LiAlF 4、LiSbF 6、LiWF 7等无机锂盐；LiWOF 5等钨酸锂类；HCO 2Li、CH 3CO 2Li、CH 2FCO 2Li、CHF 2CO 2Li、CF 3CO 2Li、CF 3CH 2CO 2Li、CF 3CF 2CO 2Li、CF 3CF 2CF 2CO 2Li、CF 3CF 2CF 2CF 2CO 2Li等羧酸锂盐类；FSO 3Li、CH 3SO 3Li、CH 2FSO 3Li、CHF 2SO 3Li、CF 3SO 3Li、CF 3CF 2SO 3Li、CF 3CF 2CF 2SO 3Li、CF 3CF 2CF 2CF 2SO 3Li等磺酸锂盐类；LiN(FCO) 2、LiN(FCO)(FSO 2)、LiN(FSO 2) 2、LiN(FSO 2)(CF 3SO 2)、LiN(CF 3SO 2) 2、LiN(C 2F 5SO 2) 2、环状1,2-全氟乙烷双磺酰亚胺锂、环状1,3-全氟丙烷双磺酰亚胺锂、LiN(CF 3SO 2)(C 4F 9SO 2)等酰亚胺锂盐类；LiC(FSO 2) 3、LiC(CF 3SO 2) 3、LiC(C 2F 5SO 2) 3等甲基化锂盐类；双(丙二酸根合)硼酸锂盐、二氟(丙二酸根合)硼酸锂盐等(丙二酸根合)硼酸锂盐类；三(丙二酸根合)磷酸锂、二氟双(丙二酸根合)磷酸锂、四氟(丙二酸根合)磷酸锂等(丙二酸根合)磷酸锂盐类；以及LiPF 4(CF 3) 2、LiPF 4(C 2F 5) 2、LiPF 4(CF 3SO 2) 2、LiPF 4(C 2F 5SO 2) 2、LiBF 3CF 3、LiBF 3C 2F 5、LiBF 3C 3F 7、LiBF 2(CF 3) 2、LiBF 2(C 2F 5) 2、LiBF 2(CF 3SO 2) 2、LiBF 2(C 2F 5SO 2) 2等含氟有机锂盐类；二氟草酸硼酸锂、双(草酸)硼酸锂等草酸硼酸锂盐类；四氟草酸根合磷酸锂、二氟双(草酸根合)磷酸锂、三(草酸根合)磷酸锂等草酸根合磷酸锂盐类等。
在一些实施例中，电解质选自LiPF 6、LiSbF 6、FSO 3Li、CF 3SO 3Li、LiN(FSO 2) 2、LiN(FSO 2)(CF 3SO 2)、LiN(CF 3SO 2) 2、LiN(C 2F 5SO 2) 2、环状1,2-全氟乙烷双磺酰亚胺锂、环状1,3-全氟丙烷双磺酰亚胺锂、LiC(FSO 2) 3、LiC(CF 3SO 2) 3、LiC(C 2F 5SO 2) 3、LiBF 3CF 3、LiBF 3C 2F 5、LiPF 3(CF 3) 3、LiPF 3(C 2F 5) 3、二氟草酸硼酸锂、双(草酸)硼酸锂或二氟双(草酸根合)磷酸锂，其有助于改善电化学装置的输出功率特性、高倍率充放电特性、高温保存特性和循环特性等。
电解质的含量没有特别限制，只要不损害本申请的效果即可。在一些实施例中，电解液中的锂的总摩尔浓度为大于0.3mol/L以上、大于0.4mol/L或大于0.5mol/L。在一些实施例中，电解液中的锂的总摩尔浓度为小于3mol/L、小于2.5mol/L或小于2.0mol/L以下。在一些实施例中，电解液中的锂的总摩尔浓度在上述任意两个数值所组成的范围内。当电解质浓度在上述范围内时，作为带电粒子的锂不会过少，并且可以使粘度处于适当的范围，因而容易确保良好的电导率。
当使用两种以上的电解质的情况下，电解质包括至少一种为选自由单氟磷酸 盐、硼酸盐、草酸盐和氟磺酸盐组成的组中的盐。在一些实施例中，电解质包括选自由单氟磷酸盐、草酸盐和氟磺酸盐组成的组中的盐。在一些实施例中，电解质包括锂盐。在一些实施例中，基于电解质的重量，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。
III、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活性物质层，负极活性物质层包含负极活性物质。负极活性物质层可以是一层或多层，多层负极活性物质中的每层可以包含相同或不同的负极活性物质。负极活性物质为任何能够可逆地嵌入和脱嵌锂离子等金属离子的物质。在一些实施例中，负极活性物质的可充电容量大于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。
作为保持负极活性物质的集流体，可以任意使用公知的集流体。负极集流体的实例包括，但不限于，铝、铜、镍、不锈钢、镀镍钢等金属材料。在一些实施例中，负极集流体为铜。
在负极集流体为金属材料的情况下，负极集流体形式可包括，但不限于，金 属箔、金属圆柱、金属带卷、金属板、金属薄膜、金属板网、冲压金属、发泡金属等。在一些实施例中，负极集流体为金属薄膜。在一些实施例中，负极集流体为铜箔。在一些实施例中，负极集流体为基于压延法的压延铜箔或基于电解法的电解铜箔。
在一些实施例中，负极集流体的厚度为大于1μm或大于5μm。在一些实施例中，负极集流体的厚度为小于100μm或小于50μm。在一些实施例中，负极集流体的厚度在上述任意两个数值所组成的范围内。
负极活性物质没有特别限制，只要能够可逆地吸藏、放出锂离子即可。负极活性物质的实例可包括，但不限于，天然石墨、人造石墨等碳材料；硅(Si)、锡(Sn)等金属；或Si、Sn等金属元素的氧化物等。负极活性物质可以单独使用或组合使用。
负极活性物质层还可包括负极粘合剂。负极粘合剂可提高负极活性物质颗粒彼此间的结合和负极活性物质与集流体的结合。负极粘合剂的种类没有特别限制，只要是对于电解液或电极制造时使用的溶剂稳定的材料即可。在一些实施例中，负极粘合剂包括树脂粘合剂。树脂粘合剂的实例包括，但不限于，氟树脂、聚丙烯腈(PAN)、聚酰亚胺树脂、丙烯酸系树脂、聚烯烃树脂等。当使用水系溶剂制备负极合剂浆料时，负极粘合剂包括，但不限于，羧甲基纤维素(CMC)或其盐、苯乙烯-丁二烯橡胶(SBR)、聚丙烯酸(PAA)或其盐、聚乙烯醇等。
负极可以通过以下方法制备：在负极集流体上涂布包含负极活性物质、树脂粘合剂等的负极合剂浆料，干燥后，进行压延而在负极集流体的两面形成负极活性物质层，由此可以得到负极。
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。
本申请的电化学装置包括发生电化学反应的任何装置，它的具体实例包括锂金属二次电池或锂离子二次电池。
本申请另提供了一种电子装置，其包括根据本申请所述的电化学装置。
本申请的电化学装置的用途没有特别限定，其可用于现有技术中已知的任何电子装置。在一些实施例中，本申请的电化学装置可用于，但不限于，笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
下面以锂离子电池为例并且结合具体的实施例说明锂离子电池的制备，本领域的技术人员将理解，本申请中描述的制备方法仅是实例，其他任何合适的制备方法均在本申请的范围内。
实施例
一、锂离子电池的制备
1、负极的制备
将人造石墨、丁苯橡胶和羧甲基纤维素钠按照96％:2％:2％的质量比例与去离子水混合，搅拌均匀，得到负极浆料。将该负极浆料涂布在9μm的铜箔上，干燥，冷压，再经过裁片、焊接极耳，得到负极。
2、正极的制备
称取一定量的Co 3O 4以及LiOH粉末，在玛瑙研钵中进行充分混合研磨后，然后在900℃下煅烧10小时。将煅烧后的混合物中加入特定计量比的具有第一元素的氧化物、硫酸盐或硝酸盐，并以醇作为溶剂，球磨10小时后，在800℃下煅烧10小时，得到具有第一元素的钴酸锂。
将正极活性物质(具有/不具有第一元素的钴酸锂)、碳纳米管和聚偏氟乙烯按照97:1:2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12.5％。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：
材料名称 缩写 材料名称 缩写
碳酸乙烯酯 EC 碳酸乙烯酯 PC
碳酸二乙酯 DEC 氟代碳酸乙烯酯 FEC
丁二腈 SN 己二腈 ADN
乙二醇二(2-氰基乙基)醚 EDN 1,3,6-己烷三腈 HTCN
1,2,3-三(2-氰基乙氧基)丙烷 TCEP 1,3-丙磺酸内酯 PS
式I-1化合物 式I-1 式1-3化合物 式I-3
式I-4化合物 式I-4 式II-1化合物 式II-1
式II-4化合物 式II-4 式II-5化合物 式II-5
1-丙基磷酸环酐 T3P 硫酸乙烯酯 DTD
碳酸乙烯亚乙酯 VC    
4、隔离膜的制备
以聚乙烯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、锂离子电池的高温循环容量保持率的测试方法
在65℃下，将锂离子电池以1C恒流充电至4.7V，然后恒压4.7V充电至电流为0.05C，再以1C恒流放电至3.0V，此为首次循环。按照上述条件对锂离子电池进行500次循环。“1C”指的是在1小时内将电池容量完全放完的电流值。
通过下式计算锂离子电池的循环后容量保持率：
循环后容量保持率＝(循环后的放电容量/首次循环的放电容量)×100％。
2、锂离子电池的高温短路变形率的测试方法
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4.7V，再在4.7V下恒压充电至0.05C，静置60分钟，测量锂离子电池的厚度T 1。然后以100mΩ使锂离子电池短路10秒钟，然后测量锂离子电池的厚度T 2。通过下式计算锂离子电池高温短路变形率：
短路变形率＝[(T 2-T 1)/T 1]×100％。
三、测试结果
表1展示了正极活性物质和粘结剂对锂离子电池的高温循环性能和安全性的影响。在各实施例和对比例中，正极活性物质为含有/不含有第一元素的钴酸锂。
表1
Figure PCTCN2021142399-appb-000007
Figure PCTCN2021142399-appb-000008
如对比例1-1所示，当正极活性物质未经掺杂时，即使采用本申请的低密度正极粘结剂，锂离子电池具有较低的高温循环容量保持率和较高的短路变形率。如对比例1-2和1-3所示，当正极活性物质包括铝、镁、钛、锆或钨中的至少一种掺杂元素但正极粘结剂的密度过高(大于1.5g/cm 3)或过低(小于0.6g/cm 3)时，锂离子电池依然具有较低的高温循环容量保持率和较高的短路变形率。
如实施例1-1至1-24所示，当正极活性物质包括铝、镁、钛、锆或钨中的至少一种掺杂元素且正极粘结剂具有0.6-1.5g/cm 3的密度时，可显著提升锂离子电池的高温循环容量保持率并显著降低其短路变形率。
表2展示了粘结剂的孔隙率及其与密度的关系对锂离子电池的高温循环性能和安全性的影响。除表2中所列参数以外，实施例2-1至2-16与实施例1-1的设置相同。
表2
Figure PCTCN2021142399-appb-000009
Figure PCTCN2021142399-appb-000010
结果表明，当粘结剂的孔隙率为20％-50％且粘结剂的孔隙率b％与密度a g/cm 3满足17≤a×b≤60时，可进一步提升锂离子电池的高温循环容量保持率并降低其短路变形率。
表3展示了正极活性物质中铝和钨的含量对锂离子电池的高温循环性能和安全性的影响。除表3中所列参数以外，实施例3-1至3-9与实施例1-1的设置相同。
表3
Figure PCTCN2021142399-appb-000011
结果表明，当正极活性物质包括铝和钨元素且铝含量x％与钨含量y％满足1≤x/y≤5时，可进一步提升锂离子电池的高温循环容量保持率并降低其短路变形率。
表4展示了正极活性物质中铝的含量与粘结剂密度的关系对锂离子电池的高温循环性能和安全性的影响。除表4中所列参数以外，实施例4-1至4-10与实施例1-1的设置相同。
表4
Figure PCTCN2021142399-appb-000012
结果表明，当正极活性物质包括铝元素且铝含量x％与粘结剂密度a g/cm 3满足0.2≤x/a≤1时，可进一步提升锂离子电池的高温循环容量保持率并降低其短路变形率。
表5展示了电解液中具有硫氧双键化合物及其与粘结剂密度的关系对锂离子电池的高温循环性能和安全性的影响。除表5中所列参数以外，实施例5-1至5-14与实施例1-1的设置相同。
表5
Figure PCTCN2021142399-appb-000013
Figure PCTCN2021142399-appb-000014
结果表明，当电解液还包括0.01％-5％的具有硫氧双键的化合物时，可进一步提升锂离子电池的高温循环容量保持率并降低其短路变形率。
当电解液中具有硫氧双键的化合物的含量c％与正极粘结剂的密度a g/cm 3满足0.5≤c/a≤3时，可进一步提升锂离子电池的高温循环容量保持率并降低其短路变形率。
表6展示了电解液中三腈化合物及其与粘结剂密度的关系对锂离子电池的高温循环性能和安全性的影响。除表6中所列参数以外，实施例6-1至6-14与实施例1-1的设置相同。
表6
Figure PCTCN2021142399-appb-000015
结果表明，当电解液还包括0.01％-5％的三腈化合物时，可进一步提升锂离子电池的高温循环容量保持率并降低其短路变形率。
当电解液中具有硫氧双键的化合物的含量d％与正极粘结剂的密度a g/cm 3满足0.2≤d/a≤4时，可进一步提升锂离子电池的高温循环容量保持率并降低其短路变形率。
表7展示了电解液中添加剂对锂离子电池的高温循环性能和安全性的影响。 除表7中所列参数以外，实施例7-1至7-10与实施例1-1的设置相同。
表7
Figure PCTCN2021142399-appb-000016
结果表明，当电解液包含丁二腈、己二腈、乙二醇二(2-氰基乙基)醚、氟代碳酸乙烯酯、碳酸亚乙烯酯或1-丙基磷酸环酐中的至少一种时，可进一步提升锂离子电池的高温循环容量保持率并降低其短路变形率。
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 (12)

  1. 一种电化学装置，其包括：正极、负极和电解液，所述正极包括正极集流体和形成在所述正极集流体上的正极活性物质层，所述正极活性物质层包括正极活性物质和粘结剂，其中：
    所述正极活性物质具有第一元素，所述第一元素包括铝、镁、钛、锆或钨中的至少一种，并且
    所述粘结剂的密度为a g/cm 3，a的取值范围为0.6至1.5。
  2. 根据权利要求1所述的电化学装置，其中a的取值范围为0.6至1.2、0.7至1.0或0.7至0.9。
  3. 根据权利要求1所述的电化学装置，其中所述粘结剂的孔隙率为b％，b的取值范围为20至50，且a和b满足：17≤a×b≤60。
  4. 根据权利要求1所述的电化学装置，其中所述粘结剂包括含氟聚合物，优选聚偏氟乙烯。
  5. 根据权利要求1所述的电化学装置，其中所述电化学装置满足如下中的至少一者：
    a.所述第一元素包括铝以及镁、钛、锆或钨中的至少一种；
    b.所述第一元素包括钨以及镁、钛、锆或铝中的至少一种；
    c.所述第一元素包括铝和钨，基于所述正极活性物质的重量，铝和钨的含量分别为x％和y％，x和y满足：1≤x/y≤5；
    d.基于所述正极活性物质的重量，所述第一元素的含量为0.01至2％。
  6. 根据权利要求1所述的电化学装置，其中所述第一元素包括铝，基于所述正极活性物质的重量，铝的含量为x％，且x和a满足0.2≤x/a≤1。
  7. 根据权利要求1所述的电化学装置，其中所述电解液包括具有硫氧双键 的化合物，基于所述电解液的重量，所述具有硫氧双键的化合物的含量为c％，c的取值范围为0.01至5。
  8. 根据权利要求7所述的电化学装置，其中c和a满足：0.5≤c/a≤3。
  9. 根据权利要求1所述的电化学装置，其中所述电解液包括三腈化合物，基于所述电解液的重量，所述三腈化合物的含量为d％，d的取值范围为0.01至5。
  10. 根据权利要求9所述的电化学装置，其中d和a满足：0.2≤d/a≤4。
  11. 根据权利要求1所述的电化学装置，其中所述电解液包括丁二腈、己二腈、乙二醇二(2-氰基乙基)醚、氟代碳酸乙烯酯、碳酸亚乙烯酯或1-丙基磷酸环酐中的至少一种。
  12. 一种电子装置，其包括根据权利要求1-11中任一项所述的电化学装置。
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