WO2023056612A1 - 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
WO2023056612A1
WO2023056612A1 PCT/CN2021/122705 CN2021122705W WO2023056612A1 WO 2023056612 A1 WO2023056612 A1 WO 2023056612A1 CN 2021122705 W CN2021122705 W CN 2021122705W WO 2023056612 A1 WO2023056612 A1 WO 2023056612A1
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Prior art keywords
positive electrode
active material
electrode active
material layer
electrochemical device
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PCT/CN2021/122705
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English (en)
French (fr)
Inventor
王可飞
韩冬冬
张青文
刘胜奇
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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 CN202180013405.7A priority Critical patent/CN115336067A/zh
Priority to EP21959704.4A priority patent/EP4398330A1/en
Priority to PCT/CN2021/122705 priority patent/WO2023056612A1/zh
Publication of WO2023056612A1 publication Critical patent/WO2023056612A1/zh
Priority to US18/621,801 priority patent/US20240243265A1/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
    • H01M4/362—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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—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
    • 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
    • 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
    • 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
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • H01M4/623—Binders being polymers fluorinated polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • 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.
  • the safety of the electrochemical device during use can be improved to a certain extent.
  • a safety coating eg, a ceramic layer
  • the contact internal resistance can be increased and the risk of thermal runaway can be reduced.
  • the provision of a safety coating reduces the energy density of the electrochemical device and degrades other electrochemical performances. Therefore, how to improve the energy density and electrochemical performance of electrochemical devices on the basis of ensuring the safety performance of electrochemical devices has received more and more attention.
  • the present application solves the problems existing in the prior art to some extent by improving the configuration of the positive electrode of the electrochemical device and the matching between the positive electrode and the electrolyte.
  • the present application provides an electrochemical device, which includes a positive electrode, a negative electrode and an electrolyte, the positive electrode includes: a current collector; and a positive active material layer, the positive active material layer is located in the collector On at least one surface of the fluid, and including a first positive electrode active material layer and a second positive electrode active material layer, wherein the first positive electrode active material layer is located between the current collector and the second positive electrode active material layer; wherein The binding force between the current collector and the first positive electrode active material layer is F 1 N/m, the cohesion force of the second positive electrode active material layer is F 2 N/m, and the positive electrode satisfies: F 1 /F 2 ⁇ 6.
  • the first positive electrode active material layer includes a first binder, and the first binder satisfies at least one of the following conditions: (1) The first binder has water solubility; (2) the first binder has unsaturated acid functional groups; (3) the first binder includes polyacrylate with polar functional groups; (4) based on the The mass fraction of the first positive electrode active material layer is b%, wherein 2 ⁇ b ⁇ 20.
  • the first positive electrode active material layer includes a first binder, and based on the mass of the first positive electrode active material layer, the mass of the first binder The fraction is b%, where F 1 and b satisfy: F 1 ⁇ 200, 2 ⁇ b ⁇ 20 and F 1 /b ⁇ 10.
  • the second positive electrode active material layer includes a second binder, and the second binder satisfies at least one of the following conditions: (1) The second binder is non-water-soluble; (2) the second binder includes a fluoropolymer; (3) the second binder includes polyvinylidene fluoride with an alpha crystal form; (4) Based on the mass of the second positive electrode active material layer, the mass fraction of the second binder is a%, where 0.5 ⁇ a ⁇ 5.
  • the second positive electrode active material layer includes a second binder; based on the mass of the second positive electrode active material layer, the mass of the second binder The fraction is a%, where the relationship between F 2 and a satisfies: 5 ⁇ F 2 ⁇ 60, 0.5 ⁇ a ⁇ 5 and F 2 /a ⁇ 1.
  • the first positive electrode active material layer includes a water-soluble binder
  • the second positive electrode active material layer includes a water-insoluble binder
  • the first positive electrode active material layer includes a first binder, and based on the mass of the first positive electrode active material layer, the mass of the first binder The fraction is b%;
  • the second positive electrode active material layer includes a second binder, based on the mass of the second positive electrode active material layer, the mass fraction of the second binder is a%; wherein a and b Satisfy: 2.5 ⁇ a+b ⁇ 25; 1 ⁇ b/a ⁇ 40.
  • the thickness of the first positive electrode active material layer is H 1 ⁇ m
  • the thickness of the positive electrode active material layer is H ⁇ m
  • the positive electrode satisfies: H 1 /H ⁇ 0.1.
  • the electrolyte solution includes a compound having a cyano group.
  • the content of the compound having a cyano group is x%, where 0.1 ⁇ x ⁇ 15.
  • the compound having a cyano group includes at least one of the following: succinonitrile, glutaronitrile, adiponitrile, 1,5-dicyano Pentane, 1,6-dicyanohexane, tetramethylsuccinonitrile, 2-methylglutaronitrile, 2,4-dimethylglutaronitrile, 2,2,4,4-tetramethyl Glutaronitrile, 1,4-dicyanopentane, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, ethylene glycol bis(propionitrile) ether , 3,5-dioxa-pimelonitrile, 1,4-bis(cyanoethoxy)butane, diethylene glycol bis(2-cyanoethyl)ether, triethylene glycol bis(2 -cyanoethyl) ether, tetraethylene glycol bis(2-
  • the electrolyte solution includes propylene carbonate.
  • the content of the propylene carbonate is y%, where 2 ⁇ y ⁇ 25.
  • the content of the propylene carbonate is y%, wherein F 2 /y ⁇ 0.5.
  • the electrolyte includes propyl propionate, wherein based on the quality of the electrolyte, the content of the propyl propionate is z%, where 5 ⁇ z ⁇ 50.
  • the electrolyte includes a compound with a cyano group and propyl propionate, wherein based on the quality of the electrolyte, the content of the compound with a cyano group is x %, the content of propyl propionate is z%, wherein 12 ⁇ x+z ⁇ 65, and 0.5 ⁇ z/x ⁇ 50.
  • the electrolyte includes propylene carbonate and propyl propionate, wherein based on the quality of the electrolyte, the content of the propylene carbonate is y%, and the The content of propyl propionate is z%, wherein 15 ⁇ y+z ⁇ 70, and 1 ⁇ z/y ⁇ 5.
  • the electrolyte solution includes at least one of the following: fluoroethylene carbonate, 1,3-propane sultone, vinyl sulfate, ethylene carbonate Vinyl ester or 1-propyl phosphoric acid cyclic anhydride.
  • the present application provides an electronic device, which includes the electrochemical device described in the above embodiments.
  • the ratio of the binding force F1 between the first positive electrode active material layer and the current collector to the cohesive force F2 of the second positive electrode active material layer in an appropriate range, the The possibility of internal short circuit in the electrochemical device is squeezed, needled, overcharged, etc., thereby improving the safety of the electrochemical device; at the same time, it can also effectively improve the cycle performance of the electrochemical device under high pressure and high temperature, and Reduce its DC internal resistance under high pressure and high temperature.
  • 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”.
  • the positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material and a binder.
  • the positive electrode active material may be any substance capable of reversibly intercalating and deintercalating metal ions such as lithium ions and sodium ions.
  • the positive current collector may be a common positive current collector in the art, including, but not limited to, aluminum foil or nickel foil.
  • the present application finds that by coating at least two layers of positive electrode active material layers on at least one surface of the positive electrode current collector, and controlling the cohesion and binding force of the above-mentioned at least two layers of positive electrode active material layers in an appropriate range , can enhance the safety performance of the electrochemical device, and can also reduce the DC internal resistance of the electrochemical device under high temperature and high pressure environment and improve its cycle stability.
  • the present application provides a positive electrode, which includes a current collector and a positive active material layer, the positive active material layer is located on at least one surface of the current collector, and includes a first positive active material layer.
  • the bonding force between them is F 1 N/m
  • the cohesive force of the second positive electrode active material layer is F 2 N/m
  • the positive electrode satisfies: F 1 /F 2 ⁇ 6.
  • the value of F 1 /F 2 can reflect the mechanical stability of the positive electrode of the electrochemical device under abuse conditions such as extrusion, acupuncture, overcharge, or during charge and discharge cycles.
  • the above positive electrode can also reduce the DC internal resistance of the electrochemical device under high temperature and high pressure.
  • F 1 and F 2 satisfy: F 1 /F 2 ⁇ 10. In some embodiments, F 1 and F 2 satisfy: F 1 /F 2 ⁇ 20. In some embodiments, F 1 and F 2 satisfy: F 1 /F 2 ⁇ 30. In some embodiments, F 1 and F 2 satisfy: F 1 /F 2 ⁇ 40. In some embodiments, F 1 and F 2 satisfy: F 1 /F 2 ⁇ 50.
  • performance can be further improved, especially safety stability, cycle performance and impedance performance.
  • F 1 >200. In some embodiments, F 1 >220. In some embodiments, F 1 is 250, 300, 350, 400, 450, 500, 600, 700, 800 or within a range consisting of any two of the above values.
  • the present application finds that at least selecting the type or content of the binder in the first positive electrode active material layer and/or the second positive electrode active material layer helps to further realize F 1 /F 2 ⁇ 6.
  • the first positive electrode active material layer includes a first binder, and the first binder satisfies at least one of the following conditions:
  • the first binder is water-soluble
  • the first binder has an unsaturated acid functional group
  • the first binder includes polyacrylate with polar functional groups
  • the mass fraction of the first binder is b%, where 2 ⁇ b ⁇ 20.
  • Using a water-soluble binder in the first positive electrode active material layer can more effectively improve the performance of the electrochemical device. This may be due to hydrogen bonding or other intermolecular forces occurring between the water-soluble binder and polar functional groups such as hydroxyl groups on the surface of the positive electrode current collector (for example, aluminum foil), thereby increasing the gap between the positive electrode active material layer and the current collector. Excellent adhesion, greatly reducing the risk of the active material layer falling off the current collector, thereby greatly reducing the probability of dislocation or short circuit, effectively improving the safety of the electrochemical device and improving the cycle stability of the electrochemical device under high temperature and high pressure sex.
  • the first positive electrode active material layer satisfies F 1 /b ⁇ 10
  • a positive electrode with better stability can be obtained, thereby further improving the electrochemical performance of the electrochemical device (for example, under high temperature and high pressure) Thermal safety performance, cycle performance and DC internal resistance).
  • F 1 and b simultaneously satisfy: F 1 ⁇ 200, 2 ⁇ b ⁇ 20 and F 1 /b ⁇ 10, the stability of the positive electrode can be further improved.
  • the second positive electrode active material layer includes a second binder, and the second binder satisfies at least one of the following conditions:
  • the second binder is water-insoluble
  • the second binder includes a fluoropolymer
  • the second binder includes polyvinylidene fluoride having an ⁇ crystal form
  • the mass fraction of the second binder is a%, where 0.5 ⁇ a ⁇ 5.
  • the second positive electrode active material layer satisfies F 2 /a ⁇ 1
  • a positive electrode with better stability can be obtained, thereby further improving the electrochemical performance of the electrochemical device (for example, under high temperature and high pressure) Thermal safety performance, cycle performance and DC internal resistance).
  • F 2 and a simultaneously satisfy: 5 ⁇ F 2 ⁇ 60, 0.5 ⁇ a ⁇ 5 and F 2 /a ⁇ 1, the stability of the positive electrode is further improved.
  • the positive electrode satisfies both F 1 /b ⁇ 10 and F 2 /a ⁇ 1. Under this configuration, the stability of the positive electrode is better, and the obtained electrochemical device also exhibits better electrochemical performance. In some embodiments, the positive electrode simultaneously satisfies F 1 ⁇ 200, 2 ⁇ b ⁇ 20, F 1 /b ⁇ 10, 5 ⁇ F 2 ⁇ 60, 0.5 ⁇ a ⁇ 5 and F 2 /a ⁇ 1.
  • the obtained electrochemical device exhibits better thermal safety performance, cycle performance and impedance characteristics under high temperature and high pressure.
  • using a water-soluble binder in the first positive electrode active material layer and using a water-insoluble binder in the second positive electrode active material layer improves the electrochemical performance of the electrochemical device more significantly.
  • the binder cannot realize the deintercalation of metal ions, adding too much will sacrifice the energy density of the electrochemical device.
  • the content of the binder is too low, the active material layer cannot be firmly pasted on the positive electrode current collector, thereby increasing the risk of stripping. Therefore, by adjusting the content of the first binder and the second binder in the first positive electrode active material layer and the second positive electrode active material layer respectively, the energy density and other electrochemical performances (for example, safety) of the electrochemical device can be taken into account. performance, cycling stability, and low impedance).
  • the mass fractions b% and a% of the first binder and the second binder satisfy 2.5 ⁇ a+b ⁇ 25 and 1 ⁇ b/a ⁇ 40.
  • a and b satisfy: 3 ⁇ a+b ⁇ 20 and 2 ⁇ b/a ⁇ 30. In some embodiments, a and b satisfy: 3.5 ⁇ a+b ⁇ 15 and 5 ⁇ b/a ⁇ 20. In some embodiments, a and b satisfy: 6 ⁇ a+b ⁇ 12 and 5 ⁇ b/a ⁇ 10.
  • a satisfies 0.5 ⁇ a ⁇ 5. In some embodiments, a satisfies 1 ⁇ a ⁇ 4. In some embodiments, a is 0.8, 1, 1.2, 1.5, 1.8, 2, 2.5, 3, 3.5, 4, 4.5, 5 or is in a range consisting of any two values above.
  • b satisfies 2 ⁇ b ⁇ 20. In some embodiments, b satisfies 3 ⁇ b ⁇ 18. In some embodiments, b is 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 18, 20 or is in a range consisting of any two of the above values.
  • the electrochemical performance of the electrochemical device can also be further improved by adjusting the thickness of the first positive electrode active material layer, wherein the thickness mentioned here refers to the thickness of the positive electrode active material layer along the direction perpendicular to the current collector.
  • the thickness of the first positive electrode active material layer is H 1 ⁇ m
  • the thickness of the positive electrode active material layer is H ⁇ m
  • the positive electrode satisfies: H 1 /H ⁇ 0.1.
  • the thickness H 1 ⁇ m of the first positive electrode active material layer is in the range of 0.1 ⁇ H 1 ⁇ 5.
  • the thickness H 1 ⁇ m of the first positive electrode active material layer is in the range of 0.1 ⁇ H 1 ⁇ 3.
  • controlling the thickness of the first positive electrode active material layer within the above range can further optimize the performance of the electrochemical device.
  • positive electrode active material there is no particular limitation on the type of positive electrode active material, as long as it can absorb and release metal ions (eg, lithium ions, sodium ions) electrochemically.
  • metal ions eg, lithium ions, sodium ions
  • the positive electrode active materials applicable to the first positive electrode active material layer and the second positive electrode active material layer in the present application may independently be lithium-containing oxides, and may be the same or different.
  • a lithium-containing transition metal oxide can be used as the lithium-containing oxide.
  • 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-containing transition metal oxides and lithium-containing transition metal phosphate compounds.
  • the transition metal in the lithium-containing transition metal oxide includes V, Ti, Cr, Mn, Fe, Co, Ni, Cu, and the like.
  • lithium-containing transition metal oxides include lithium-cobalt composite oxides such as LiCoO 2 , lithium-nickel composite oxides such as LiNiO 2 , lithium-manganese composite oxides such as LiMnO 2 , LiMn 2 O 4 , Li 2 MnO 4 , lithium nickel manganese cobalt composite oxides such as LiNi 1/3 Mn 1/3 Co 1/3 O 2 , LiNi 0.5 Mn 0.3 Co 0.2 O 2 , etc., in which a part of the transition metal atom which is the host of these lithium-containing transition metal oxides is Na, K, B, F, Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, W and other elements substituted .
  • lithium-containing transition metal oxides may include, but are not limited to, LiNi 0.5 Mn 0.5 O 2 , LiNi 0.85 Co 0.10 Al 0.05 O 2 , LiNi 0.33 Co 0.33 Mn 0.33 O 2 , LiNi 0.45 Co 0.10 Al 0.45 O 2 , LiMn 1.8 Al 0.2 O 4 and LiMn 1.5 Ni 0.5 O 4 etc.
  • combinations of lithium-containing transition metal 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 can be replaced by transition metals (e.g., LiNi 0.33 Co 0.33 Mn 0.33 O 2 ), part of Co in LiCoO 2 can be replaced by transition metals.
  • transition metals e.g., LiNi 0.33 Co 0.33 Mn 0.33 O 2
  • part of Co in LiCoO 2 can be replaced by transition metals.
  • the transition metals in the lithium-containing transition metal phosphate compound include V, Ti, Cr, Mn, Fe, Co, Ni, Cu, and the like.
  • lithium-containing transition metal phosphate compounds include iron phosphates such as LiFePO 4 , Li 3 Fe 2 (PO 4 ) 3 , LiFeP 2 O 7 , and cobalt phosphates such as LiCoPO 4 , wherein as these lithium transition metal phosphate compounds Some of the transition metal atoms of the main body are replaced by other elements such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si, etc.
  • lithium phosphate is included in the positive active material, which can improve the continuous charging characteristics of the electrochemical device.
  • the use of lithium phosphate is not limited.
  • the positive electrode active material and lithium phosphate are used in combination.
  • the content of lithium phosphate is greater than 0.1%, greater than 0.3% or greater than 0.5% relative to the mass 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 mass of the positive electrode active material and lithium phosphate.
  • the content of lithium phosphate is within the range formed by any two values above.
  • a substance having a different composition may adhere to the surface of the positive electrode active material.
  • surface attachment substances may include, but are not limited to: oxides such as alumina, silica, titania, zirconia, magnesia, calcium oxide, boron oxide, antimony oxide, bismuth oxide; lithium sulfate, sodium sulfate, potassium sulfate , magnesium sulfate, calcium sulfate, aluminum sulfate and other sulfates; lithium carbonate, calcium carbonate, magnesium carbonate and other carbonates; carbon, etc.
  • These surface attachment substances can be attached to the surface of the positive electrode active material by the following methods: dissolving or suspending the surface attachment substances in a solvent and infiltrating into the positive electrode active material and drying them; dissolving or suspending the surface attachment substance precursors In a solvent, after infiltrating and adding to the positive electrode active material, the method of making it react by heating or the like; and the method of firing while adding to the positive electrode active material precursor, etc.
  • attaching carbon a method of mechanically attaching a carbon material (for example, activated carbon, etc.) can also be used.
  • the content of the surface attachment substance is greater than 0.1 ppm, greater than 1 ppm or greater than 10 ppm. In some embodiments, based on the mass of the positive electrode active material layer, the content of the surface attachment substance is less than 10%, less than 5% or less than 2%. In some embodiments, based on the mass of the positive electrode active material layer, the content of the surface attachment substance is within the range formed by any two values above.
  • the oxidation reaction of the electrolyte solution on the surface of the positive electrode active material can be suppressed, and the life of the electrochemical device can be improved.
  • the amount of the surface-attached substance is too small, the effect cannot be fully expressed; when the amount of the surface-attached substance is too large, it will hinder the entry and exit of lithium ions, so the resistance may increase.
  • a positive electrode active material having a composition different from the positive electrode active material attached to the surface of the positive electrode active material is also referred to as a "positive electrode active material”.
  • the shape of the positive electrode active material particles includes, but is not limited to, block shape, polyhedron shape, spherical shape, ellipsoidal shape, plate shape, needle shape, columnar shape, and the like.
  • the positive active material particles include primary particles, secondary particles, or a combination thereof.
  • primary particles may agglomerate to form secondary particles.
  • the tap density of the positive active material is greater than 0.5 g/cm 3 , greater than 0.8 g/cm 3 or greater than 1.0 g/cm 3 .
  • the tap density of the positive electrode active material is within the above range, the required amount of dispersion medium and conductive material and positive electrode binder can be suppressed when the positive electrode active material layer is formed, thereby ensuring the filling of the positive electrode active material rate and capacity of the electrochemical device.
  • a composite oxide powder having a high tap density a high-density positive electrode active material layer can be formed. The larger the tap density is generally, the more preferable it is, and there is no particular upper limit.
  • the tap density of the positive active material is less than 4.0 g/cm 3 , less than 3.7 g/cm 3 or less than 3.5 g/cm 3 .
  • the tap density of the positive electrode active material has the upper limit as described above, a decrease in load characteristics can be suppressed.
  • the tap density of the positive active material can be calculated in the following way: put 5g to 10g of positive active material powder into a 10mL glass measuring cylinder, and vibrate 200 times with a stroke of 20mm to obtain the powder packing density (tap density ).
  • the median diameter (D50) of the positive electrode active material particles refers to the primary particle diameter of the positive electrode active material particles.
  • the median diameter (D50) of the positive electrode active material particles refers to the secondary particle diameter of the positive electrode active material particles.
  • the median diameter (D50) of the positive electrode active material particles is greater than 0.3 ⁇ m, greater than 0.5 ⁇ m, greater than 0.8 ⁇ m or greater than 1.0 ⁇ m. In some embodiments, the median diameter (D50) of the positive electrode active material particles is less than 30 ⁇ m, less than 27 ⁇ m, less than 25 ⁇ m or less than 22 ⁇ m. In some embodiments, the median diameter (D50) of the positive electrode active material particles is within the range formed by any two values above. When the median diameter (D50) of the positive electrode active material particles is within the above-mentioned range, a positive electrode active material with a high tap density can be obtained, and a decrease in the performance of the electrochemical device can be suppressed.
  • the positive electrode active material particle median diameter (D50) can be measured by a laser diffraction/scattering particle size distribution analyzer: in the case of using LA-920 manufactured by HORIBA Corporation as a particle size distribution meter, use 0.1% sodium hexametaphosphate aqueous solution as The dispersion medium used in the measurement was measured after 5 minutes of ultrasonic dispersion with the refractive index set to 1.24.
  • the present application also provides a method of manufacturing the above-mentioned positive electrode, the method comprising:
  • the first positive electrode active material layer applied on one side of the positive electrode current collector The thickness and loading of the second positive electrode active material layer may be the same as or different from the thickness and loading of the second positive electrode current collector.
  • the electrolytic solution used in the electrochemical device of the present application includes an electrolyte and a solvent for dissolving the electrolyte. In some embodiments, the electrolyte solution used in the electrochemical device of the present application further includes additives.
  • the electrolyte solution described herein includes a compound having a cyano group.
  • the compound having a cyano group can form a stable protective film on the surface of the positive electrode active material, thereby improving the thermal safety, cycle performance and impedance characteristics of the electrochemical device under high temperature and high pressure.
  • the compound having a cyano group includes, but is not limited to, at least one 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-dioxa-pimelonitrile, 1,4-bis(cyanoethoxy)butane, diethylene glycol bis(2-cyanoethyl) ether, triethylene glycol bis(2-cyano Ethyl) ether, tetraethylene glycol bis(2-cyanoethy
  • the above-mentioned compounds having a cyano group may be used alone or in any combination.
  • the content of the compounds having cyano groups refers to the total content of the two or more compounds having cyano groups.
  • the protective effect of the compound with cyano group has a certain correlation with its dosage.
  • the content of the compound having a cyano group is x%, wherein 0.1 ⁇ x ⁇ 15.
  • x is in the range of 0.5 ⁇ x ⁇ 10, 1 ⁇ x ⁇ 8, or 3 ⁇ x ⁇ 5.
  • x can be, but not limited to, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15 or in a range consisting of any two of the above values .
  • the electrochemical device can be further compensated for during charging and discharging.
  • the particle breakage caused by the cycle process further improves the thermal safety performance and cycle performance of the electrochemical device under high temperature and high pressure, and reduces its DC internal resistance.
  • F 1 and x satisfy: F 1 /x ⁇ 13.33. In some embodiments, F 1 and x satisfy: F 1 /x ⁇ 25.
  • F 1 and x satisfy: F 1 /x ⁇ 33.33. In some embodiments, F 1 and x satisfy: F 1 /x ⁇ 50. In some embodiments, F 1 and x satisfy: F 1 /x ⁇ 100. In particular, in the above embodiments, controlling F 1 above 200 N/m can achieve better electrochemical performance.
  • 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.
  • the electrolyte includes propylene carbonate.
  • propylene carbonate By controlling the content of propylene carbonate in the electrolyte, an electrochemical device with excellent thermal safety performance and cycle performance and low DC resistance under high temperature and high pressure can be obtained.
  • the content of propylene carbonate is y%, wherein 2 ⁇ y ⁇ 25.
  • y may be, but not limited to, 6, 7, 8, 10, 12, 14, 18, 20, 22, 25 or within a range consisting of any two values above.
  • the present application found that by controlling the relationship between the cohesive force F2 of the second positive electrode active material layer and the content y% of propylene carbonate, the thermal safety performance, cycle performance and DC resistance of the electrochemical device can be further optimized.
  • propylene carbonate can easily cause swelling of the positive electrode, and may damage the interface between the positive electrode and the electrolyte, resulting in side reactions.
  • the cohesive force of the second positive electrode active material layer increases, although the swelling decreases, the side reaction of the electrolyte being oxidized by the positive electrode increases; and when the cohesive force of the second positive electrode active material layer decreases, although the side reaction weakens, it will cause swelling. Increase.
  • F 2 and y satisfy: F 2 /y ⁇ 0.5. In some embodiments, F 2 and y satisfy: F 2 /y ⁇ 1. In some embodiments, F 2 and y satisfy: F 2 /y ⁇ 2. In some embodiments, F 2 and y satisfy: F 2 /y ⁇ 5. In some embodiments, F 2 and y satisfy: F 2 /y ⁇ 6.
  • the electrolyte includes propyl propionate.
  • the resulting electrochemical device exhibits excellent thermal safety performance and cycle performance at high temperature and pressure; in addition, unexpectedly, the low temperature rate of the obtained electrochemical device Performance can also be greatly improved.
  • the content of propyl propionate is z%, wherein 5 ⁇ z ⁇ 50. In some embodiments, z may be, but not limited to, 6, 8, 10, 20, 25, 30, 35, 40 or within a range consisting of any two of the above values.
  • the electrolyte contains the compound with cyano group and propyl propionate at the same time, by controlling the relationship between the content of the compound with cyano group and propyl propionate in the electrolyte, it can also obtain excellent performance under high temperature and high pressure. Excellent thermal safety performance and cycle performance and electrochemical device with low DC resistance.
  • x and z satisfy: 12 ⁇ x+z ⁇ 65, and 0.5 ⁇ z/x ⁇ 50.
  • y and z satisfy: 15 ⁇ y+z ⁇ 70; and 1 ⁇ z/y ⁇ 5.
  • the electrolyte solution further includes at least one of fluoroethylene carbonate, 1,3-propane sultone, vinyl sulfate, vinylene carbonate, and 1-propyl phosphoric acid cyclic anhydride.
  • fluoroethylene carbonate 1,3-propane sultone
  • vinyl sulfate vinylene carbonate
  • 1-propyl phosphoric acid cyclic anhydride When using a compound having a cyano group, propylene carbonate, propyl propionate, fluoroethylene carbonate, 1,3-propane sultone, vinyl sulfate, vinylene carbonate, 1-propyl phosphoric acid cyclic anhydride
  • the interface between the electrode and the electrolyte can be further stabilized, thereby improving the thermal safety performance and cycle performance of the electrochemical device under high temperature and high pressure, especially the storage performance at high temperature will be greatly improved.
  • the electrolyte is not particularly limited, and any known substance as an electrolyte can be used arbitrarily.
  • lithium salts are generally used.
  • electrolytes may include, but are not limited to, inorganic lithium salts such as LiPF 6 , LiBF 4 , LiClO 4 , LiAlF 4 , LiSbF 6 , LiWF 7 ; lithium tungstates such as LiWOF 5 ; HCO 2 Li, CH 3 CO 2 Li, CH 2 FCO 2 Li, CHF 2 CO 2 Li, CF 3 CO 2 Li, CF 3 CH 2 CO 2 Li, CF 3 CF 2 CO 2 Li, CF 3 CF 2 CO 2 Li, CF 3 CF 2 CF 2 CO 2 Li, CF 3 CF 2 CF 2 Lithium carboxylate salts such as CF 2 CO 2 Li; FSO 3 Li, CH 3 SO 3 Li, CH 2 FSO 3 Li, CHF 2 SO 3 Li, CF 3 SO 3 Li, CF 3 CF 2 SO 3 Li, CF 3
  • the electrolyte is selected from LiPF 6 , LiSbF 6 , FSO 3 Li, CF 3 SO 3 Li, LiN(FSO 2 ) 2 , LiN(FSO 2 )(CF 3 SO 2 ), LiN(CF 3 SO 2 ) 2 , LiN(C 2 F 5 SO 2 ) 2 , cyclic lithium 1,2-perfluoroethanebissulfonimide, cyclic lithium 1,3-perfluoropropanebissulfonimide, LiC(FSO 2 ) 3 , LiC(CF 3 SO 2 ) 3 , LiC(C 2 F 5 SO 2 ) 3 , LiBF 3 CF 3 , LiBF 3 C 2 F 5 , LiPF 3 (CF 3 ) 3 , LiPF 3 (C 2 F 5 ) 3.
  • Lithium difluorooxalate borate, lithium bis(oxalate)borate or lithium difluorobis(oxalato)phosphate which help to improve the output power characteristics, high-rate charge-discharge characteristics, and high-temperature storage characteristics of electrochemical devices and cycle characteristics, etc.
  • the present application has no particular limitation on the content of the electrolyte, as long as the effect of the present application is not impaired.
  • the total molar concentration of lithium in the electrolyte is above 0.3 mol/L, above 0.4 mol/L or above 0.5 mol/L. In some embodiments, the total molar concentration of lithium in the electrolyte is below 3.0 mol/L, below 2.5 mol/L or below 2.0 mol/L. In some embodiments, the total molar concentration of lithium in the electrolyte is within the range formed by any two values above. When the electrolyte concentration is within the above range, the lithium as charged particles will not be too small, and the viscosity can be kept in an appropriate range, so it is easy to ensure good electrical conductivity.
  • the electrolyte includes at least one salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate.
  • the electrolyte includes a salt selected from the group consisting of monofluorophosphate, oxalate, and fluorosulfonate.
  • the electrolyte includes a lithium salt.
  • the content of the salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate is greater than 0.01% or greater than 0.1%, based on the mass of the electrolyte.
  • the content of the salt selected from the group consisting of monofluorophosphate, borate, oxalate and fluorosulfonate is less than 20% or less than 10% based on the mass of the electrolyte. In some embodiments, the content of the salt selected from the group consisting of monofluorophosphate, borate, oxalate and fluorosulfonate is within the range formed by any two values above.
  • 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 content of other salts is greater than 0.01% or greater than 0.1% based on the mass of the electrolyte. In some embodiments, the content of other salts is less than 20%, less than 15%, or less than 10%, based on the mass of the electrolyte. In some embodiments, the content of other salts is within the range formed by any two values above. 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 at least one surface of the negative electrode current collector, and the negative electrode active material layer contains a negative electrode active material.
  • the negative electrode active material layer may be one or more layers, and each layer of the multilayer negative electrode active material may contain the same or different negative electrode active materials.
  • the negative electrode active material is any material capable of reversibly intercalating and deintercalating metal ions such as lithium ions and sodium ions.
  • the charge capacity of the negative active material is greater than the discharge capacity of the positive active material, so as to prevent unintentional deposition of lithium metal on the negative electrode during charging.
  • the negative electrode current collector may be a negative electrode current collector commonly used in the art, including, but not limited to, metal materials such as aluminum, copper, nickel, stainless steel, and nickel-plated steel.
  • the form of the negative electrode current collector may include, but not limited to, metal foil, metal cylinder, metal strip, metal plate, metal film, expanded metal, stamped metal, foamed metal, etc.
  • the negative electrode current collector is a metal film.
  • the negative electrode current collector is copper foil.
  • the negative electrode current collector is a rolled copper foil based on a rolling method or an electrolytic copper foil based on an electrolytic method.
  • the thickness of the negative electrode current collector is greater than 1 ⁇ m or greater than 5 ⁇ m. In some embodiments, the thickness of the negative electrode current collector is less than 100 ⁇ m or less than 50 ⁇ m. In some embodiments, the thickness of the negative electrode current collector is within the range formed by any two values above.
  • the negative electrode active material is not particularly limited as long as it can reversibly store and release lithium ions or sodium 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 electrode active material layer also includes a negative electrode 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 application provides an electrochemical device, which includes a positive pole, a negative pole, an electrolyte, and a separator between the positive pole and the negative pole.
  • the positive electrode includes the positive electrode described in the above-mentioned embodiments of the present application.
  • the electrolyte includes the electrolyte described in the above-mentioned embodiments of the present application.
  • the present application has no particular limitation on the material and shape of the separator, as long as the effect of the present application is not significantly impaired.
  • the separator can be resin, glass fiber, inorganic material, etc. formed of materials stable to the electrolyte solution of the present application.
  • the separator includes a porous sheet or a non-woven fabric-like substance with excellent liquid retention properties.
  • the material of the resin or fiberglass separator may include, but are not limited to, polyolefin, aramid, polytetrafluoroethylene, polyethersulfone, and the like.
  • the polyolefin is polyethylene or polypropylene.
  • the polyolefin is polypropylene.
  • the materials for the above separators may be used alone or in any combination.
  • the isolation film can also be a material formed by laminating the above materials, examples of which include, but not limited to, a three-layer isolation film formed by laminating polypropylene, polyethylene, and polypropylene in this order.
  • Examples of materials of inorganic substances may include, but are not limited to, oxides such as aluminum oxide and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, sulfates (eg, barium sulfate, calcium sulfate, etc.).
  • Inorganic forms may include, but are not limited to, granular or fibrous.
  • the form of the separator may be in the form of a film, examples of which include, but are not limited to, non-woven fabrics, woven fabrics, microporous films, and the like.
  • the pore diameter of the isolation membrane is 0.01 ⁇ m to 1 ⁇ m, and the thickness is 5 ⁇ m to 50 ⁇ m.
  • the following separator can also be used: a separator formed by forming a composite porous layer containing the above-mentioned inorganic particles on the surface of the positive electrode and/or negative electrode using a resin-based binder,
  • a separator is formed by using fluororesin as a binder to form porous layers on both sides of the positive electrode with 90% of the alumina particles having a particle size of less than 1 ⁇ m.
  • the thickness of the separator is arbitrary. In some embodiments, the thickness of the isolation film is greater than 1 ⁇ m, greater than 5 ⁇ m, or greater than 8 ⁇ m. In some embodiments, the thickness of the isolation film is less than 50 ⁇ m, less than 40 ⁇ m or less than 30 ⁇ m. In some embodiments, the thickness of the isolation film is within the range formed by any two values above. When the thickness of the separator is within the above range, insulation and mechanical strength can be ensured, and rate characteristics and energy density of the electrochemical device can be ensured.
  • the porosity of the separator is arbitrary.
  • the isolation membrane has a porosity greater than 10%, greater than 15%, or greater than 20%.
  • the separator has a porosity of less than 60%, less than 50%, or less than 45%.
  • the porosity of the isolation membrane is within the range formed by any two values above. When the porosity of the separator is within the above range, insulation and mechanical strength can be ensured, and film 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 of the present application includes any device that undergoes an electrochemical reaction, and its specific examples include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors.
  • the electrochemical device is a lithium secondary battery, including a lithium metal secondary battery or a lithium ion secondary battery.
  • the present application further provides an electronic device, which includes the electrochemical device according to the present application.
  • the application of the electrochemical device of the present application is not particularly limited, and it can be used in any electronic device known in the prior art.
  • the electrochemical device of the present application can be used in, but not limited to, notebook computers, pen-based computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-worn Stereo headphones, VCRs, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic organizers, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, automobiles, motorcycles, power assist Bicycles, bicycles, lighting equipment, toys, game consoles, clocks, electric tools, flashlights, cameras, large household storage batteries and lithium-ion capacitors, etc.
  • the lithium ion battery is taken as an example below and the preparation of the lithium ion battery is described in conjunction with specific examples. Those skilled in the art will understand that the preparation method described in this application is only an example, and any other suitable preparation methods are described in this application. within range.
  • Electrolyte preparation In a dry argon environment, EC and DEC were mixed at a mass ratio of 1:1, and LiPF 6 was added to mix evenly to form a basic electrolyte, in which the concentration of LiPF 6 was 1.15mol/L.
  • the electrolytes of the examples and comparative examples described in this application were obtained by adding different contents of additives into the basic electrolyte.
  • Cohesion test Take the disassembled pole piece of the battery, select a single-sided coated pole piece (or double-sided coated pole piece processed by a scraper), and cut the sample to be tested with a length of 100mm and a width of 10mm. Take a stainless steel plate with a width of 25mm, paste 3M double-sided adhesive (width 11mm), and paste the sample to be tested on the 3M double-sided adhesive on the stainless steel plate, in which the current collector is bonded to the double-sided adhesive; use a 2000g pressure roller on the sample The surface is rolled back and forth three times (300mm/min).
  • a tape with a width of 10 mm and a thickness of 50 ⁇ m (model NITTO.NO5000NS) was pasted on the surface of the active material layer, and a 2000 g pressure roller was used to roll back and forth on the surface three times (300 mm/min).
  • Adhesion test take the disassembled pole piece of the battery, cut it into a test sample with a size of 20mm ⁇ 10cm, and stick it on a clean stainless steel plate with a 20mm wide double-sided adhesive (model NITTO.NO5000NS) .
  • a tensile testing machine was used to perform a 180° peel test, and the tensile speed of the tensile machine was 50mm/min.
  • the average value of the peeling force collected when the first positive electrode active material layer is completely peeled off from the positive electrode current collector is the bonding force F between the positive electrode current collector and the first positive electrode active material layer.
  • the thickness expansion rate of the lithium-ion battery is calculated by the following formula:
  • Temperature-rise thickness expansion rate [(T 2 -T 1 )/T 1 ] ⁇ 100%.
  • Capacity retention (C 800 /C 1 ) ⁇ 100%.
  • the high-temperature storage thickness expansion rate of lithium-ion batteries is calculated by the following formula:
  • High temperature storage thickness expansion ratio [(T 4 -T 3 )/T 3 ] ⁇ 100%.
  • the lithium ion batteries of Examples 1-1 to 1-8 and Comparative Examples 1-1 to 1-4 were prepared according to the above preparation method, the difference lies in the binder content, the first binder is water-soluble polyacrylate, the second The second binder is oil-soluble PVDF.
  • Table 1 has shown the cohesive force F 1 between positive electrode current collector and the first positive electrode active material layer and the cohesive force F 2 of the second positive electrode active material layer to the thermal safety performance of lithium-ion battery under high temperature and pressure, DC internal resistance and effect on cycle performance.
  • the positive electrodes in Examples 1-1 to 1-8 of the present application all satisfy F 1 /F 2 ⁇ 6,
  • the corresponding electrochemical device has lower thickness expansion at high temperature, and has lower DC resistance and higher capacity retention rate during high temperature and high pressure charge and discharge.
  • the data of Examples 1-5 to 1-8 it can be seen that with the increase of the bonding force F1 between the positive electrode current collector and the first positive electrode active material layer, the corresponding electrochemical device obtained under high temperature and high pressure or Under abuse conditions, the less risk of internal short circuit, the higher the thermal safety performance.
  • Table 2 shows the impact of the first binding agent and the second binding agent on the thermal safety performance, DC internal resistance and cycle performance of lithium-ion batteries under high temperature and high pressure, wherein Examples 2-1 to 2-14 and Example 1-1 differ only in the parameters listed in Table 2.
  • Example 2-9 Comparing the data of Examples 2-9 and Examples 2-12 in Table 2, it can be seen that when the first positive electrode active material layer uses a water-soluble binder, the corresponding electrochemical performance of the obtained electrochemical device is better. Comparing Example 2-8 with Example 2-11, the same conclusion can be drawn. This may be due to hydrogen bonding or other intermolecular forces between the water-soluble binder and the polar functional groups such as hydroxyl groups on the surface of the positive electrode current collector aluminum foil, thereby increasing the binding force.
  • Examples 2-13 and 2-14 comparing Examples 2-9, it can be seen that under the same binder used, when the content of the first binder and the second binder When 2.5 ⁇ a+b ⁇ 25 and 1 ⁇ b/a ⁇ 40 are satisfied, the structure of the positive electrode is more stable, and the performance of the electrochemical device can be further improved.
  • Examples 1-1 and 2-1 to 2-12 it can be seen that when other binders are used and the content of other binders satisfies 2.5 ⁇ a+b ⁇ 25 and 1 ⁇ b/a ⁇ 40 , can also obtain a more stable positive electrode.
  • Table 3 shows the effects of F 1 /b and F 2 /a on the thermal safety performance, DC internal resistance and cycle performance of electrochemical devices under high temperature and high pressure. The difference between Examples 3-1 to 3-6 and Example 1-1 lies in the parameters listed in Table 3.
  • Table 4 shows the influence of the total thickness H of the positive electrode active material layer and the thickness H1 of the first positive electrode active material layer on the thermal safety performance, DC internal resistance and cycle performance of the electrochemical device under high temperature and high pressure.
  • the difference between Examples 4-1 to 4-5 and Example 1-1 lies in the parameters listed in Table 4.
  • Table 5 shows the effects of the compounds with cyano groups contained in the electrolyte on the thermal safety performance, DC internal resistance and cycle performance of the electrochemical device under high temperature and high pressure. The difference between Examples 5-1 to 5-25 and Example 1-1 lies in the parameters listed in Table 5.
  • Table 6 shows the effect of propylene carbonate in the electrolyte on the thermal safety performance, DC internal resistance and cycle performance of the electrochemical device under high temperature and high pressure. The only difference between Examples 6-1 to 6-8 and Example 1-1 lies in the parameters listed in Table 6.
  • Table 7 shows the effects of the content of the compound with cyano group and propyl propionate on the thermal safety performance, DC internal resistance and cycle performance of the electrochemical device under high temperature and high pressure. The only difference between Examples 7-1 to 7-16 and Example 1-1 lies in the parameters listed in Table 7.
  • Table 8 shows the effects of the content of propylene carbonate and propyl propionate on the thermal safety performance, low-temperature rate performance and cycle performance of electrochemical devices under high temperature and high pressure. The difference between Examples 8-1 to 8-8 and Example 1-1 lies in the parameters listed in Table 8.
  • Table 9 shows the effects of solvents and additives in the electrolyte on the thermal safety performance and cycle performance of electrochemical devices under high temperature and high pressure. The difference between Examples 9-1 to 9-17 and Example 1-1 lies in the parameters listed in Table 9.
  • 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

一种电化学装置和电子装置。电化学装置包括正极，正极包括集流体和正极活性物质层，正极活性物质层位于集流体的至少一个表面上，且包括第一正极活性物质层和第二正极活性物质层。其中第一正极活性物质层位于集流体和第二正极活性物质层之间，其中集流体与第一正极活性物质层之间的粘结力为F 1 N/m，第二正极活性物质层的内聚力为F 2 N/m，正极满足：F 1/F 2≥6。将上述正极应用于电化学装置中，不仅能够增强电化学装置的安全性能，还能够充分抑制电化学装置在高压高温下的直流内阻并改善其循环性能。

Description

电化学装置和电子装置 技术领域
本申请涉及储能领域，具体涉及一种电化学装置和电子装置。
背景技术
近年来，人们对电化学装置能量密度的要求越来越高。然而，在追求高能量密度的同时，所带来的安全问题也日益突出。例如，当电化学装置在挤压、针刺、过充等滥用的情况下，其内部容易发生短路，积累大量热量，导致热失控，进而出现起火、爆炸等问题。
通过改变电化学装置中的极片配置能够在一定程度上提高电化学装置在使用过程中的安全性。例如，在现有技术中，通过在极片表面设置安全涂层，能够增加接触内阻，降低热失控的风险。然而，安全涂层(例如，陶瓷层)的设置会降低电化学装置的能量密度，并使其它电化学性能变差。因此，如何在保证电化学装置安全性能的基础上，提高电化学装置的能量密度和电化学性能受到了越来越多的关注。
发明内容
本申请通过改进电化学装置的正极配置以及正极与电解液之间的匹配以在某种程度上解决现有技术所存在的问题。
根据本申请的一个方面，本申请提供了一种电化学装置，其包括正极、负极和电解液，所述正极包括：集流体；以及正极活性物质层，所述正极活性物质层位于所述集流体的至少一个表面上，且包括第一正极活性物质层和第二正极活性物质层，其中所述第一正极活性物质层位于所述集流体和所述第二正极活性物质层之间；其中所述集流体与所述第一正极活性物质层之间的粘结力为F 1N/m，所述第二正极活性物质层的内聚力为F 2N/m，所述正极满足：F 1/F 2≥6。
根据本申请的实施例，在上述电化学装置中，F 1≥200。
根据本申请的实施例，在上述电化学装置中，所述第一正极活性物质层包括第一粘结剂，所述第一粘结剂满足如下条件中的至少一者：(1)所述第一粘结剂具有水溶性；(2)所述第一粘结剂具有不饱和酸官能团；(3)所述第一粘结剂包括具有极性官能团的聚丙烯酸酯；(4)基于所述第一正极活性物质层的质量，所述第一粘结剂的质量分数为b％，其中2≤b≤20。
根据本申请的实施例，在上述电化学装置中，所述第一正极活性物质层包括第一粘结剂，基于所述第一正极活性物质层的质量，所述第一粘结剂的质量分数为b％，其中F 1和b满足：F 1≥200，2≤b≤20且F 1/b≥10。
根据本申请的实施例，在上述电化学装置中，所述第二正极活性物质层包括第二粘结剂，所述第二粘结剂满足如下条件中的至少一者：(1)所述第二粘结剂具有非水溶性；(2)所述第二粘结剂包括含氟聚合物；(3)所述第二粘结剂包括具有α晶型的聚偏氟乙烯；(4)基于所述第二正极活性物质层的质量，所述第二粘结剂的质量分数为a％，其中0.5≤a≤5。
根据本申请的实施例，在上述电化学装置中，所述第二正极活性物质层包括第二粘结剂；基于所述第二正极活性物质层的质量，所述第二粘结剂的质量分数为a％，其中F 2和a的关系满足：5≤F 2≤60，0.5≤a≤5且F 2/a≥1。
根据本申请的实施例，在上述电化学装置中，所述第一正极活性物质层包括水溶性粘结剂，且所述第二正极活性物质层包括非水溶性粘结剂。
根据本申请的实施例，在上述电化学装置中，所述第一正极活性物质层包括第一粘结剂，基于所述第一正极活性物质层的质量，所述第一粘结剂的质量分数为b％；所述第二正极活性物质层包括第二粘结剂，基于所述第二正极活性物质层的质量，所述第二粘结剂的质量分数为a％；其中a和b满足：2.5≤a+b≤25；1≤b/a≤40。
根据本申请的实施例，在上述电化学装置中，所述第一正极活性物质层的厚度为H 1μm，所述正极活性物质层的厚度为Hμm，所述正极满足：H 1/H≤0.1。
根据本申请的实施例，在上述电化学装置中，0.1≤H 1≤5。
根据本申请的实施例，在上述电化学装置中，所述电解液包括具有氰基的化合物。
根据本申请的实施例，在上述电化学装置中，基于所述电解液的质量，所述 具有氰基的化合物的含量为x％，其中0.1≤x≤15。
根据本申请的实施例，在上述电化学装置中，F 1≥200，且F 1/x≥13.33。
根据本申请的实施例，在上述电化学装置中，所述具有氰基的化合物包括以下各者中的至少一者：丁二腈、戊二腈、己二腈、1,5-二氰基戊烷、1,6-二氰基己烷、四甲基丁二腈、2-甲基戊二腈、2,4-二甲基戊二腈、2,2,4,4-四甲基戊二腈、1,4-二氰基戊烷、1,2-二氰基苯、1,3-二氰基苯、1,4-二氰基苯、乙二醇双(丙腈)醚、3,5-二氧杂-庚二腈、1,4-二(氰基乙氧基)丁烷、二乙二醇二(2-氰基乙基)醚、三乙二醇二(2-氰基乙基)醚、四乙二醇二(2-氰基乙基)醚、1,3-二(2-氰基乙氧基)丙烷、1,4-二(2-氰基乙氧基)丁烷、1,5-二(2-氰基乙氧基)戊烷、乙二醇二(4-氰基丁基)醚、1,4-二氰基-2-丁烯、1,4-二氰基-2-甲基-2-丁烯、1,4-二氰基-2-乙基-2-丁烯、1,4-二氰基-2,3-二甲基-2-丁烯、1,4-二氰基-2,3-二乙基-2-丁烯、1,6-二氰基-3-己烯、1,6-二氰基-2-甲基-3-己烯、1,3,5-戊三甲腈、1,2,3-丙三甲腈、1,3,6-己三甲腈、1,2,6-己三甲腈、1,2,3-三(2-氰基乙氧基)丙烷、1,2,4-三(2-氰基乙氧基)丁烷、1,1,1-三(氰基乙氧基亚甲基)乙烷、1,1,1-三(氰基乙氧基亚甲基)丙烷、3-甲基-1,3,5-三(氰基乙氧基)戊烷、1,2,7-三(氰基乙氧基)庚烷、1,2,6-三(氰基乙氧基)己烷或1,2,5-三(氰基乙氧基)戊烷。
根据本申请的实施例，在上述电化学装置中，所述电解液包括碳酸丙烯酯。
根据本申请的实施例，在上述电化学装置中，基于所述电解液的质量，所述碳酸丙烯酯的含量为y％，其中2≤y≤25。
根据本申请的实施例，在上述电化学装置中，基于所述电解液的质量，所述碳酸丙烯酯的含量为y％，其中F 2/y≥0.5。
根据本申请的实施例，在上述电化学装置中，所述电解液包括丙酸丙酯，其中基于所述电解液的质量，所述丙酸丙酯的含量为z％，其中5≤z≤50。
根据本申请的实施例，在上述电化学装置中，所述电解液包括具有氰基的化合物和丙酸丙酯，其中基于所述电解液的质量，所述具有氰基的化合物的含量为x％，所述丙酸丙酯的含量为z％，其中12≤x+z≤65，且0.5≤z/x≤50。
根据本申请的实施例，在上述电化学装置中，所述电解液包括碳酸丙烯酯和丙酸丙酯，其中基于所述电解液的质量，所述碳酸丙烯酯的含量为y％，所述丙酸丙酯的含量为z％，其中15≤y+z≤70，且1≤z/y≤5。
根据本申请的实施例，在上述电化学装置中，所述电解液包括以下各者中的 至少一者：氟代碳酸乙烯酯、1,3-丙磺酸内酯、硫酸乙烯酯、碳酸亚乙烯酯或1-丙基磷酸环酐。
根据本申请的一个方面，本申请提供了一种电子装置，其包括上述实施例所述的电化学装置。
在至少一个方面，通过控制第一正极活性物质层与所述集流体之间的粘结力F 1和第二正极活性物质层的内聚力F 2的比值在合适的范围内，能够有效地降低在电化学装置被挤压、针刺、过充等滥用情况下发生内部短路的几率，从而改善电化学装置的安全性；同时，还能够有效地提高电化学装置在高压高温下的循环性能，并降低其在高压高温下的直流内阻。
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。在本申请说明书全文中，将相同或相似的组件以及具有相同或相似的功能的组件通过类似附图标记来表示。在此所描述的有关附图的实施例为说明性质的、图解性质的且用于提供对本申请的基本理解。本申请的实施例不应该被解释为对本申请的限制。
在本文中以范围格式呈现量、比率和其它数值。应理解，此类范围格式是用于便利及简洁起见，且应灵活地理解，不仅包含明确地指定为范围限制的数值，而且包含涵盖于所述范围内的所有个别数值或子范围，如同明确地指定每一数值及子范围一般。
在具体实施方式及权利要求书中，由术语“中的至少一者”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
在本申请中，正极包括正极集流体和设置在正极集流体的至少一个表面上的正极活性物质层，其中正极活性物质层包括正极活性材料和粘结剂。在本申请中，正极活性材料可以为能够可逆地嵌入和脱出锂离子、钠离子等金属离子的任何物质。在一些实施例中，正极集流体可以是本领域常用的正极集流体，其包括，但不限于，铝箔或镍箔。
在至少一个方面，本申请发现通过将至少两层正极活性物质层涂覆在正极集流体的至少一个表面上，并控制上述至少两层正极活性物质层的内聚力和粘结力在合适的范围内，能够增强电化学装置的安全性能，同时还能够降低电化学装置在高温高压环境下的直流内阻并改善其循环稳定性。
具体地，在一些实施例中，本申请提供了一种正极，其包括集流体和正极活性物质层，所述正极活性物质层位于所述集流体的至少一个表面上，且包括第一正极活性物质层和第二正极活性物质层；其中所述第一正极活性物质层位于所述集流体和所述第二正极活性物质层之间；其中所述集流体与所述第一正极活性物质层之间的粘结力为F 1N/m，所述第二正极活性物质层的内聚力为F 2N/m，所述正极满足：F 1/F 2≥6。
电化学装置的极片的不同层之间以及各个层内部均具有作用力。例如，在电化学装置充放电循环过程中，由于活性金属离子(例如，锂离子)在活性物质颗粒中的脱嵌，会造成活性物质颗粒的膨胀或破裂，从而导致极片的集流体、第一活性物质层和第二活性物质层之间存在相互作用力。F 1/F 2的值能够反映电化学装置在挤压、针刺、过充等滥用情况下或者在充放电循环过程中正极的力学稳定性。当F 1/F 2的值满足关系式F 1/F 2≥6时，极片和集流体的应力均匀化，受到挤压或针刺时或者在高温高压下充放电循环过程中，发生错位或短路的几率更低，从而有效地提升电化学装置的安全性，并且有效地改善电化学装置在高温高压下的循环性能。另外，出乎意料的是，上述正极还能够降低电化学装置在高温高压下的直流内阻。
在一些实施例中，F 1和F 2满足：F 1/F 2≥10。在一些实施例中，F 1和F 2满足：F 1/F 2≥20。在一些实施例中，F 1和F 2满足：F 1/F 2≥30。在一些实施例中，F 1和F 2满足：F 1/F 2≥40。在一些实施例中，F 1和F 2满足：F 1/F 2≥50。当电化学装置满足 上述关系时，能够进一步改善性能，尤其是安全稳定性、循环性能和阻抗表现。
随着正极集流体与第一正极活性物质层之间的粘结力F 1的增大，正极活性物质层和集流体之间发生脱膜的概率越小，因此在电化学装置经受高温、高压或被滥用的情况下，其内发生短路的风险越小，热安全性能越高。在一些实施例中，F 1≥200。在一些实施例中，F 1≥220。在一些实施例中，F 1为250、300、350、400、450、500、600、700、800或处于由上述任意两个数值所组成的范围内。
在一些实施例中，5≤F 2≤100。在一些实施例中，15≤F 2≤80。在一些实施例中，F 2为20、25、30、35、40、45、50、60、70、80、90、100或处于由上述任意两个数值所组成的范围内。
本申请发现至少通过选择第一正极活性物质层和/或第二正极活性物质层中的粘结剂的种类或含量有助于进一步实现F 1/F 2≥6。在一些实施例中，所述第一正极活性物质层包括第一粘结剂，第一粘结剂满足如下条件中的至少一者：
(1)所述第一粘结剂具有水溶性；
(2)所述第一粘结剂具有不饱和酸官能团；
(3)所述第一粘结剂包括具有极性官能团的聚丙烯酸酯；
(4)基于所述第一正极活性物质层的质量，所述第一粘结剂的质量分数为b％，其中2≤b≤20。
在第一正极活性物质层中使用水溶性粘结剂，能够更有效地改善电化学装置的性能。这可能是由于水溶性粘结剂与正极集流体(例如，铝箔)表面的羟基等极性官能团之间发生氢键作用或其他分子间力作用，从而增大正极活性物质层与集流体之间的粘结力，大大降低活性物质层从集流体脱落的风险，从而大幅度地降低发生错位或短路的几率，有效地提升电化学装置的安全性并改善电化学装置在高温高压下的循环稳定性。
在一些实施例中，当第一正极活性物质层满足F 1/b≥10时，能够获得稳定性更好的正极，从而能够进一步提高电化学装置的电化学性能(例如，在高温高压下的热安全性能、循环性能和直流内阻)。特别地，当F 1和b同时满足：F 1≥200，2≤b≤20且F 1/b≥10，正极的稳定性能够得到进一步的提升。
在一些实施例中，第二正极活性物质层包括第二粘结剂，第二粘结剂满足如下条件中的至少一者：
(1)所述第二粘结剂具有非水溶性；
(2)所述第二粘结剂包括含氟聚合物；
(3)所述第二粘结剂包括具有α晶型的聚偏氟乙烯；
(4)基于所述第二正极活性物质层的质量，所述第二粘结剂的质量分数为a％，其中0.5≤a≤5。
在一些实施例中，当第二正极活性物质层满足F 2/a≥1时，能够获得稳定性更好的正极，从而能够进一步提高电化学装置的电化学性能(例如，在高温高压下的热安全性能、循环性能和直流内阻)。特别地，当F 2和a同时满足：5≤F 2≤60，0.5≤a≤5且F 2/a≥1，正极的稳定性能得到进一步的提升。
在一些实施例中，正极同时满足F 1/b≥10且F 2/a≥1。在该配置下，正极的稳定性更好，所获得的电化学装置也表现出更优异的电化学性能。在一些实施例中，正极同时满足，F 1≥200，2≤b≤20，F 1/b≥10，5≤F 2≤60，0.5≤a≤5且F 2/a≥1。
当第一正极活性物质层和第二正极活性物质层使用不同溶解性的粘结剂时，所获得的电化学装置在高温高压下表现出更优异的热安全性能、循环性能和阻抗特性。尤其是，在第一正极活性物质层中使用水溶性粘结剂，而在第二正极活性物质层中使用非水溶性粘结剂，对电化学装置的电化学性能的改善更为明显。
由于粘结剂无法实现金属离子的脱嵌，因此过多添加会牺牲电化学装置的能量密度。而当粘结剂的含量过低时，无法使得活性物质层牢固地粘贴在正极集流体上，从而增加脱膜的风险。因此，通过调整第一粘结剂和第二粘结剂分别在第一正极活性物质层和第二正极活性物质层中的含量能够兼顾电化学装置的能量密度与其他电化学性能(例如，安全性能、循环稳定性和低阻抗)。在一些实施例中，第一粘结剂和第二粘结剂的质量分数b％和a％满足2.5≤a+b≤25且1≤b/a≤40。在一些实施例中，a和b满足：3≤a+b≤20且2≤b/a≤30。在一些实施例中，a和b满足：3.5≤a+b≤15且5≤b/a≤20。在一些实施例中，a和b满足：6≤a+b≤12且5≤b/a≤10。
在一些实施例中，a满足0.5≤a≤5。在一些实施例中，a满足1≤a≤4。在一些实施例中，a为0.8、1、1.2、1.5、1.8、2、2.5、3、3.5、4、4.5、5或处于由上述任意两个数值所组成的范围内。
在一些实施例中，b满足2≤b≤20。在一些实施例中，b满足3≤b≤18。在一些实施例中，b为3、4、5、6、7、8、9、10、12、15、18、20或处于由上述任意两个数值所组成的范围内。
内聚力和粘结力测试参考本申请在具体实施例部分的具体描述进行测定。
通过调整第一正极活性物质层的厚度也能够进一步改善电化学装置的电化学表现，其中这里所提的厚度是指正极活性物质层沿垂直于集流体方向的厚度。在一些实施例中，第一正极活性物质层的厚度为H 1μm，正极活性物质层的厚度为Hμm，所述正极满足：H 1/H≤0.1。在一些实施例中，第一正极活性物质层的厚度H 1μm处于0.1≤H 1≤5的范围内。在一些实施例中，第一正极活性物质层的厚度H 1μm处于0.1≤H 1≤3的范围内。特别的，当在第一正极活性物质层中使用水溶性粘结剂时，控制第一正极活性物质层的厚度在上述范围内，能够进一步优化电化学装置的性能。
本申请对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收和释放金属离子(例如，锂离子、钠离子)即可。另外，本申请适用于第一正极活性物质层和第二正极活性物质层的正极活性材料可独立地为含锂氧化物，并且可以相同或不同。可使用含锂过渡金属氧化物作为含锂氧化物。
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，含锂过渡金属氧化物和含锂过渡金属磷酸化合物。
在一些实施例中，含锂过渡金属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，含锂过渡金属氧化物包括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，其中作为这些含锂过渡金属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。含锂过渡金属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。含锂过渡金属氧化物的组合的实例包括，但不限于，LiCoO 2与LiMn 2O 4的组合，其中LiMn 2O 4中的一部分Mn可被过渡金属所取代(例如，LiNi 0.33Co 0.33Mn 0.33O 2)，LiCoO 2中的一部分Co可被过渡金属所取代。
在一些实施例中，含锂过渡金属磷酸化合物中的过渡金属包括V、Ti、Cr、Mn、Fe、Co、Ni、Cu等。在一些实施例中，含锂过渡金属磷酸化合物包括LiFePO 4、 Li 3Fe 2(PO 4) 3、LiFeP 2O 7等磷酸铁类、LiCoPO 4等磷酸钴类，其中作为这些锂过渡金属磷酸化合物的主体的过渡金属原子的一部分被Al、Ti、V、Cr、Mn、Fe、Co、Li、Ni、Cu、Zn、Mg、Ga、Zr、Nb、Si等其它元素所取代。
在一些实施例中，正极活性物质中包含磷酸锂，其可提高电化学装置的连续充电特性。磷酸锂的使用没有限制。在一些实施例中，正极活性物质和磷酸锂混合使用。在一些实施例中，相对于上述正极活性物质与磷酸锂的质量，磷酸锂的含量为大于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质量，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。
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质量，表面附着物质的含量为大于0.1ppm、大于1ppm或大于10ppm。在一些实施例中，基于正极活性物质层的质量，表面附着物质的含量为小于10％、小于5％或小于2％。在一些实施例中，基于正极活性物质层的质量，表面附着物质的含量在上述任意两个数值所组成的范围内。
通过在正极活性物质表面附着物质，可以抑制正极活性物质表面的电解液的氧化反应，可以提高电化学装置的寿命。当表面附着物质的量过少时，其效果无法充分表现；当表面附着物质的量过多时，会阻碍锂离子的出入，因而电阻有时会增加。
本申请中，将在正极活性物质的表面附着有与其组成不同的物质的正极活性物质也称为“正极活性物质”。
在一些实施例中，正极活性物质颗粒的形状包括，但不限于，块状、多面体状、球状、椭圆球状、板状、针状和柱状等。在一些实施例中，正极活性物质颗粒包括一次颗粒、二次颗粒或其组合。在一些实施例中，一次颗粒可以凝集而形成二次颗粒。
在一些实施例中，正极活性物质的振实密度为大于0.5g/cm 3、大于0.8g/cm 3或大于1.0g/cm 3。当正极活性物质的振实密度在上述范围内时，可以抑制正极活性物质层形成时所需要的分散介质量及导电材料和正极粘合剂的所需量，由此可以确保正极活性物质的填充率和电化学装置的容量。通过使用振实密度高的复合氧化物粉体，可以形成高密度的正极活性物质层。振实密度通常越大越优选，没有特别的上限。在一些实施例中，正极活性物质的振实密度为小于4.0g/cm 3、小于3.7g/cm 3或小于3.5g/cm 3。当正极活性物质的振实密度的具有如上所述的上限时，可以抑制负荷特性的降低。
正极活性物质的振实密度可通过以下方式计算：将5g至10g的正极活性物质粉体放入10mL的玻璃制量筒中，进行200次冲程20mm的振动，得出粉体填充密度(振实密度)。
当正极活性物质颗粒为一次颗粒时，正极活性物质颗粒的中值粒径(D50)指的是正极活性物质颗粒一次粒径。当正极活性物质颗粒的一次颗粒凝集而形成二次颗粒时，正极活性物质颗粒的中值粒径(D50)指的是正极活性物质颗粒二次粒径。
在一些实施例中，正极活性物质颗粒的中值粒径(D50)为大于0.3μm、大于0.5μm、大于0.8μm或大于1.0μm。在一些实施例中，正极活性物质颗粒的中值粒径(D50)为小于30μm、小于27μm、小于25μm或小于22μm。在一些实施例中，正极活性物质颗粒的中值粒径(D50)在上述任意两个数值所组成的范围内。当正极活性物质颗粒的中值粒径(D50)在上述范围内时，可得到高振实密度的正极活性物质，可以抑制电化学装置性能的降低。另一方面，在电化学装置的正极的制备过程中(即，将正极活性物质、导电材料和粘合剂等用溶剂浆料化而以薄膜状涂布时)，可以防止条纹产生等问题。此处，通过将具有不同中值粒径的两种以上的正极活性物质进行混合，可以进一步提高正极制备时的填充性。
正极活性物质颗粒中值粒径(D50)可利用激光衍射/散射式粒度分布测定装 置测定：在使用HORIBA社制造的LA-920作为粒度分布计的情况下，使用0.1％六偏磷酸钠水溶液作为测定时使用的分散介质，在5分钟的超声波分散后将测定折射率设定为1.24而进行测定。
在至少一个方面，本申请还提供了一种制造上述正极的方法，所述方法包括：
将第一正极活性物质、第一导电材料和第一粘合剂分散在溶剂中制备成浆料用于第一正极活性物质层，并将第二正极活性物质、第二导电材料和第二粘合剂分散在溶剂中制备成浆料用于第二正极活性物质层；
将用于第一正极活性物质层的浆料施加至正极集流体的至少一个表面上，并在第一正极活性物质层干燥之前或之后再在其上施加用于第二正极活性物质层的浆料。
在上述方法中，若在正极集流体的两个表面上均施加用于第一和第二正极活性物质层的浆料，那么施加在所述正极集流体一侧上的第一正极活性物质层和第二正极活性物质层的厚度和负载量与施加在所述正极集流体另一侧上的厚度和负载量可以相同，也可以不同。
II、电解液
本申请的电化学装置所使用的电解液包括电解质和溶解电解质的溶剂。在一些实施例中，本申请的电化学装置所使用的电解液还包括添加剂。
在一些实施例中，本申请所述的电解液包括具有氰基的化合物。所述具有氰基的化合物能够在正极活性物质的表面形成稳定的保护膜，从而改善电化学装置在高温高压下的热安全性、循环性能和阻抗特性。
在一些实施例中，所述具有氰基的化合物包括，但不限于，以下各者中的至少一者：丁二腈、戊二腈、己二腈、1,5-二氰基戊烷、1,6-二氰基己烷、四甲基丁二腈、2-甲基戊二腈、2,4-二甲基戊二腈、2,2,4,4-四甲基戊二腈、1,4-二氰基戊烷、1,2-二氰基苯、1,3-二氰基苯、1,4-二氰基苯、乙二醇双(丙腈)醚、3,5-二氧杂-庚二腈、1,4-二(氰基乙氧基)丁烷、二乙二醇二(2-氰基乙基)醚、三乙二醇二(2-氰基乙基)醚、四乙二醇二(2-氰基乙基)醚、1,3-二(2-氰基乙氧基)丙烷、1,4-二(2-氰基乙氧基)丁烷、1,5-二(2-氰基乙氧基)戊烷、乙二醇二(4-氰基丁基)醚、1,4-二氰基-2-丁烯、1,4-二氰基-2-甲基-2-丁烯、1,4-二氰基-2-乙基-2-丁烯、1,4-二氰基 -2,3-二甲基-2-丁烯、1,4-二氰基-2,3-二乙基-2-丁烯、1,6-二氰基-3-己烯、1,6-二氰基-2-甲基-3-己烯、1,3,5-戊三甲腈、1,2,3-丙三甲腈、1,3,6-己三甲腈、1,2,6-己三甲腈、1,2,3-三(2-氰基乙氧基)丙烷、1,2,4-三(2-氰基乙氧基)丁烷、1,1,1-三(氰基乙氧基亚甲基)乙烷、1,1,1-三(氰基乙氧基亚甲基)丙烷、3-甲基-1,3,5-三(氰基乙氧基)戊烷、1,2,7-三(氰基乙氧基)庚烷、1,2,6-三(氰基乙氧基)己烷或1,2,5-三(氰基乙氧基)戊烷。
上述具有氰基的化合物可以单独使用，也可以任意组合使用。当电解液中含有两种或更多种具有氰基的化合物时，具有氰基的化合物的含量是指这两种或更多种具有氰基的化合物的总含量。
具有氰基的化合物的保护效果与其用量有一定的相关性。在一些实施例中，基于所述电解液的质量，所述具有氰基的化合物的含量为x％，其中0.1≤x≤15。在一些实施例中，x处于0.5≤x≤10、1≤x≤8或者3≤x≤5的范围内。在一些实施例中，x可以，但不限于，为1、2、3、4、5、6、7、8、9、10、12、15或处于由上述任意两个数值所组成的范围内。
由于具有氰基的化合物能够在正极活性物质的表面形成稳定的保护膜，这对于颗粒破裂部位的修复尤为重要。本申请进一步发现当控制集流体与第一正极活性物质层之间的粘结力F 1与具有氰基的化合物的含量x％满足如下实施例的关系时，能够进一步弥补电化学装置在充放电循环过程中导致的颗粒破裂，从而进一步改善电化学装置在高温高压下的热安全性能和循环性能，并降低其直流内阻。在一些实施例中，F 1和x满足：F 1/x≥13.33。在一些实施例中，F 1和x满足：F 1/x≥25。在一些实施例中，F 1和x满足：F 1/x≥33.33。在一些实施例中，F 1和x满足：F 1/x≥50。在一些实施例中，F 1和x满足：F 1/x≥100。特别地，在上述实施例中，控制F 1在200N/m以上，能够实现更好的电化学性能。
在一些实施例中，所述电解液进一步包含现有技术中已知的任何可作为电解液的溶剂的非水溶剂。
在一些实施例中，所述非水溶剂包括，但不限于，以下中的一种或多种：环状碳酸酯、链状碳酸酯、环状羧酸酯、链状羧酸酯、环状醚、链状醚、含磷有机溶剂、含硫有机溶剂和芳香族含氟溶剂。
在一些实施例中，所述环状碳酸酯的实例可包括，但不限于，以下中的一种或多种：碳酸乙烯酯(EC)、碳酸丙烯酯(PC)和碳酸亚丁酯。在一些实施例中， 所述环状碳酸酯具有3-6个碳原子。
在一些实施例中，所述电解液包含碳酸丙烯酯。通过控制碳酸丙烯酯在电解液中的含量，能够获得在高温高压下具有优异的热安全性能和循环性能以及低直流阻抗的电化学装置。在一些实施例中，基于电解液的质量，碳酸丙烯酯的含量为y％，其中2≤y≤25。在一些实施例中，y可以，但不限于，为6、7、8、10、12、14、18、20、22、25或处于由上述任意两个数值所组成的范围内。
另外，本申请发现通过控制第二正极活性物质层的内聚力F 2与碳酸丙烯酯的含量y％之间的关系，能够进一步优化电化学装置的热安全性能、循环性能和直流阻抗。在高温高压条件下，碳酸丙烯酯容易引起正极溶胀，且可能破坏正极和电解液之间的界面，发生副反应。当第二正极活性物质层的内聚力提高时，虽然溶胀减少，但电解液被正极氧化的副反应增加；而当第二正极活性物质层的内聚力降低时，虽然副反应减弱，但又会导致溶胀增加。因此控制F 2和y满足一定关系能够更好地平衡溶胀和副反应，从而进一步提升电化学装置的性能。在一些实施例中，F 2和y满足：F 2/y≥0.5。在一些实施例中，F 2和y满足：F 2/y≥1。在一些实施例中，F 2和y满足：F 2/y≥2。在一些实施例中，F 2和y满足：F 2/y≥5。在一些实施例中，F 2和y满足：F 2/y≥6。
在一些实施例中，所述电解液包括丙酸丙酯。通过控制丙酸丙酯在电解液中的含量，所得到的电化学装置在高温高压下表现出优异的热安全性能和循环性能；另外，意想不到的是，所得到的电化学装置的低温倍率性能也能得到大幅提高。在一些实施例中，基于电解液的质量，所述丙酸丙酯的含量为z％，其中5≤z≤50。在一些实施例中，z可以，但不限于，为6、8、10、20、25、30、35、40或处于由上述任意两个数值所组成的范围内。
当电解液中同时包括具有氰基的化合物和丙酸丙酯时，通过控制具有氰基的化合物和丙酸丙酯在电解液中的含量之间的关系，亦能获得在高温高压下具有优异的热安全性能和循环性能以及低直流阻抗的电化学装置。在一些实施例中，x和z满足：12≤x+z≤65，且0.5≤z/x≤50。
当电解液中同时包括碳酸丙烯酯和丙酸丙酯时，通过控制碳酸丙烯酯和丙酸丙酯在电解液中的含量之间的关系，亦能获得在高温高压下具有优异的热安全性能和循环性能以及低温倍率性能的电化学装置。在一些实施例中，y和z满足：15≤y+z≤70；且1≤z/y≤5。
在一些实施例中，所述电解液还包括氟代碳酸乙烯酯、1,3-丙磺酸内酯、硫酸乙烯酯、碳酸亚乙烯酯、1-丙基磷酸环酐中的至少一种。当组合使用具有氰基的化合物、碳酸丙烯酯、丙酸丙酯、氟代碳酸乙烯酯、1,3-丙磺酸内酯、硫酸乙烯酯、碳酸亚乙烯酯、1-丙基磷酸环酐时，则能够进一步稳定电极与电解液之间的界面，从而改善电化学装置在高温高压下的热安全性能和循环性能，尤其是高温下的存储性能会得到大幅提升。
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。
本申请对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在0.3mol/L以上、0.4mol/L以上或0.5mol/L以上。在一些实施例中，电解液中的锂的总摩尔浓度在3.0mol/L以下、2.5mol/L以下或2.0mol/L以下。在一些实施例中，电解液中的锂的总摩尔浓度在上述任意两个数值所组成的范围内。当电解质浓度在上述范围内时，作为带电粒子的锂不会过少，并且可以使粘度处于适当的范围，因而容易确保良好的电导率。
当使用两种以上的电解质的情况下，电解质包括至少一种为选自由单氟磷酸盐、硼酸盐、草酸盐和氟磺酸盐组成的组中的盐。在一些实施例中，电解质包括选自由单氟磷酸盐、草酸盐和氟磺酸盐组成的组中的盐。在一些实施例中，电解质包括锂盐。在一些实施例中，基于电解质的质量，选自由单氟磷酸盐、硼酸盐、草酸盐和氟磺酸盐组成的组中的盐的含量为大于0.01％或大于0.1％。在一些实施例中，基于电解质的质量，选自由单氟磷酸盐、硼酸盐、草酸盐和氟磺酸盐组成的组中的盐的含量为小于20％或小于10％。在一些实施例中，选自由单氟磷酸盐、硼酸盐、草酸盐和氟磺酸盐组成的组中的盐的含量在上述任意两个数值所组成的范围内。
在一些实施例中，电解质包含选自由单氟磷酸盐、硼酸盐、草酸盐和氟磺酸盐组成的组中的一种以上物质和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，基于电解质的质量，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，基于电解质的质量，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至少一个表面上的负极活 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、钠离子等金属离子的物质。在一些实施例中，负极活性物质的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。
在一些实施例中，负极集流体可以是本领域常用的负极集流体，其包括，但不限于，铝、铜、镍、不锈钢、镀镍钢等金属材料。
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、放出锂离子或钠离子即可。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。
IV、电化学装置
在至少一个方面，本申请提供了一种电化学装置，其包括正极、负极、电解 液以及位于所述正极和所述负极之间的隔离膜。在一些实施例中，所述正极包括本申请上述实施例所述的正极。在一些实施例中，所述电解液包括本申请上述实施例所述的电解液。
本申请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、应用
本申请的电化学装置包括发生电化学反应的任何装置，它的具体实例包括所有种类的一次电池、二次电池、燃料电池、太阳能电池或电容器。特别地，该电化学装置是锂二次电池，包括锂金属二次电池或锂离子二次电池。
本申请另提供了一种电子装置，其包括根据本申请所述的电化学装置。
本申请的电化学装置的用途没有特别限定，其可用于现有技术中已知的任何电子装置。在一些实施例中，本申请的电化学装置可用于，但不限于，笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
下面以锂离子电池为例并且结合具体的实施例说明锂离子电池的制备，本领域的技术人员将理解，本申请中描述的制备方法仅是实例，其他任何合适的制备方法均在本申请的范围内。
具体实施例
(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％的质量比与去离子水混合，搅拌均匀，得到浆料。将浆料涂布在9μm的铜箔上。干燥，冷压，再经过裁片、焊接极耳，得到负极。
(2)正极的制备：将磷酸铁锂、导电炭黑Super-P和第一粘结剂按照96.5％：1％：b％的质量比与去离子水混合，搅拌均匀，制备第一正极活性物质层浆料；将钴酸锂、导电炭黑Super-P和第二粘结剂按照97.5％：1％：a％的质量比与N-甲基吡咯烷酮(NMP)混合，搅拌均匀，制备第二正极活性物质层浆料。将第一正极活性物质层浆料涂布在由铝箔制成的正极集流体的正反面上，厚度为5μm；再在其上涂布第二正极活性物质层浆料，厚度为50μm，单面涂布总厚度为55μm。然后，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和DEC按照质量比1：1混合，同时加入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的添加剂得到本申请所述的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 碳酸丙烯酯 PC
碳酸二乙酯 DEC 丙酸丙酯 PP
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 氟代碳酸乙烯酯 FEC
1,3-丙磺酸内酯 PS 硫酸乙烯酯 DTD
碳酸亚乙烯酯 VC 1-丙基磷酸环酐 T3P
(4)隔离膜的制备：采用8μm聚乙烯膜作为隔离膜。
(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)正极和锂离子电池的测试方法
(1)内聚力测试：取电池拆解出来的极片，选取单面涂布极片(或将双面涂布通过刮刀处理为单面极片)，裁成长100mm、宽10mm的待测样品。取一条宽度25mm的不锈钢板，贴3M双面胶(宽度11mm)，将待测样品粘贴在不锈钢板上的3M双面胶上，其中集流体与双面胶粘接；用2000g压辊在样品表面来回滚压三次(300mm/min)。之后在活性物质层表面粘贴宽10mm、厚50μm的胶带(型号NITTO.NO5000NS)，用2000g压辊在其表面来回滚压三次(300mm/min)。将胶 带180度弯折，手动将胶带与活性物质层剥开25mm，将该样品固定在Instron 336型拉力试验机上，使剥离面与试验机力线保持一致(即进行180°剥离)，以300mm/min连续剥离，得到内聚力曲线，取平稳段的均值作为剥离力F 0，则被测试极片的内聚力为：F 2＝F 0/待测样品的宽度，F 2的计量单位：N/m。
(2)粘结力测试：取电池拆解出来的极片，裁成20mm×10cm尺寸大小的测试样条，用20mm宽的双面胶(型号NITTO.NO5000NS)粘附在洁净的不锈钢板上。采用拉力测试机对其进行180°剥离测试，拉力机拉伸速度为50mm/min。第一正极活性物质层从正极集流体上完全剥离时所采集的剥离力的平均值即为正极集流体与所述第一正极活性物质层之间的粘结力F。被测试极片的粘结力为：F 1＝F/待测样品的宽度，F 1的计量单位：N/m。
(3)热安全温升测试
在25℃下，将锂离子电池静置30分钟，测量厚度为T 1，然后以5℃/min的升温速度升温至130℃，保持30分钟，测量厚度为T 2。通过下式计算锂离子电池的厚度膨胀率：
温升厚度膨胀率＝[(T 2-T 1)/T 1]×100％。
(4)高温高压下的直流内阻测试
在65℃下，将锂离子电池以1.5C恒流充电至4.7V，再以4.7V恒压充电至0.05C，静置30分钟。以0.1C放电10秒，记录电压值为U 1，以1C放电360秒，记录电压值为U 2。重复充放电步骤5次。“1C”是在1小时内将锂离子电池容量完全放完的电流值。
直流电阻R＝(U 2-U 1)/(1C-0.1C)。
(5)高温高压下的容量保持率测试
在45℃下，将锂离子电池以1C恒流充电至4.7V，然后恒压充电至电流为0.05C，再用1C恒流放电至3.0V，此时为首次循环，记录首次循环的放电容量C 1。按照上述条件对锂离子电池进行800次充放电循环，记录800次循环后的放电容量C 800。循环后的容量保持率按照下式进行计算：
容量保持率＝(C 800/C 1)×100％。
(6)低温倍率性能测试
在25℃下，以0.5C恒流充电到4.7V，恒压充电至0.05C截止，然后以0.5C恒流放电到3.0V截止，记录25℃下的放电容量为C(25℃)。在25℃下，以0.5C 恒流充电到4.7V，恒压充电至0.05C截止，之后将电池置于-20℃恒温箱中，静置2小时，再以0.5C恒流放电到3.0V截止，记录-20℃下的放电容量为C(-20℃)。通过下式计算锂离子电池在低温下相较于常温下的容量保持率：
容量保持率＝[C(-20℃)/C(25℃)]×100％。
(7)高温存储性能测试
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5分钟，测量电池厚度为T 3。在60℃下存储21天后测量电池厚度为T 4。通过下式计算锂离子电池的高温存储厚度膨胀率：
高温存储厚度膨胀率＝[(T 4-T 3)/T 3]×100％。
(三)测试结果
按照上述制备方法制备实施例1-1至1-8以及对比例1-1至1-4的锂离子电池，其差异在于粘结剂含量，第一粘结剂为水溶性聚丙烯酸酯，第二粘结剂为油溶性PVDF。表1展示了正极集流体与第一正极活性物质层之间的粘结力F 1和第二正极活性物质层的内聚力F 2对锂离子电池在高温高压下的热安全性能、直流内阻和循环性能的影响。
表1
Figure PCTCN2021122705-appb-000001
参见表1中的电化学测试结果可以看出，相较于对比例1-1至1-4，本申请实施例1-1至1-8中的正极均满足F 1/F 2≥6，而对应得到的电化学装置在高温下具有较低的厚度膨胀，并且在高温高压充放电过程中具有较低的直流阻抗和较高的 容量保持率。另外，参见实施例1-5至1-8的数据可知，随着正极集流体与第一正极活性物质层之间的粘结力F 1的增大，对应得到的电化学装置在高温高压或被滥用条件下，内部短路的风险越小，热安全性能越高。
表2展示了第一粘结剂和第二粘结剂对锂离子电池在高温高压下的热安全性能、直流内阻和循环性能的影响，其中实施例2-1至2-14与实施例1-1的区别仅在于表2所列参数。
表2
Figure PCTCN2021122705-appb-000002
Figure PCTCN2021122705-appb-000003
对比表2中的实施例2-9和实施例2-12的数据可以看出，当第一正极活性物质层使用水溶性粘结剂时，对应得到的电化学装置的电化学性能更佳。将实施例2-8与实施例2-11进行对比，可以得出相同的结论。这可能是由于水溶性粘结剂与正极集流体铝箔表面的羟基等极性官能团之间发生氢键作用或其他分子间力作用，从而使得粘结力增加。另外，将实施例2-13和2-14与实施例2-9进行对比，可以看出，在使用的粘结剂相同的情况下，当第一粘结剂和第二粘结剂的含量满足2.5≤a+b≤25且1≤b/a≤40时，正极的结构更稳定，能够进一步改善电化学装置的性能。此外，参见实施例1-1和2-1至2-12的数据可知，当采用其它粘结剂且其它粘结剂的含量满足2.5≤a+b≤25且1≤b/a≤40时，同样能够获得更稳定的正极。
表3展示了F 1/b和F 2/a对电化学装置在高温高压下的热安全性能、直流内阻和循环性能的影响。实施例3-1至3-6与实施例1-1的区别仅在于表3所列参数。
表3
Figure PCTCN2021122705-appb-000004
Figure PCTCN2021122705-appb-000005
参见表3中的电化学测试结果可以看出，当正极进一步满足F 1/b≥10且F 2/a≥1时，对应得到的电化学装置在高温高压下具有较低的厚度膨胀、较低的直流内阻以及较高的容量保持率。
表4展示了正极活性物质层的总厚度H和第一正极活性物质层的厚度H 1对电化学装置在高温高压下的热安全性能、直流内阻和循环性能的影响。实施例4-1至4-5与实施例1-1的区别仅在于表4所列参数。
表4
Figure PCTCN2021122705-appb-000006
参见表4中的电化学测试结果可以看出，当正极进一步满足H 1/H≤0.1时，对应得到的电化学装置在高温高压下具有较低的厚度膨胀、较低的直流内阻以及较高的容量保持率。
表5展示了电解液中包含的具有氰基的化合物对电化学装置在高温高压下的热安全性能、直流内阻和循环性能的影响。实施例5-1至5-25与实施例1-1的区别仅在于表5所列参数。
表5
Figure PCTCN2021122705-appb-000007
Figure PCTCN2021122705-appb-000008
参见表5中的电化学测试结果可以看出，当电解液中添加具有氰基的化合物时，能够进一步改善电化学装置在高温高压下的热安全性、循环性能和阻抗特性。尤其是当F 1和x满足F 1/x≥13.33时，对电化学装置的电化学性能的改善更为突出。
表6展示了电解液中的碳酸丙烯酯对电化学装置在高温高压下的热安全性能、直流内阻和循环性能的影响。实施例6-1至6-8与实施例1-1的区别仅在于表6所列参数。
表6
Figure PCTCN2021122705-appb-000009
Figure PCTCN2021122705-appb-000010
参见表6中的电化学测试结果可以看出，当电解液添加碳酸丙烯酯，尤其是F 2和y进一步满足F 2/y≥0.5时，对应得到的电化学装置在高温高压下不仅表现出优异的热安全性能和循环性能，其直流阻抗还出乎意料地大幅降低。
表7展示了具有氰基的化合物和丙酸丙酯的含量对电化学装置在高温高压下的热安全性能、直流内阻和循环性能的影响。实施例7-1至7-16与实施例1-1的区别仅在于表7所列参数。
表7
Figure PCTCN2021122705-appb-000011
参见表7中的电化学测试结果可以看出，当在电解液中同时添加具有氰基的 化合物和丙酸丙酯，尤其是上述二者在电解液中的含量满足12≤x+z≤65且0.5≤z/x≤50时，能够进一步优化电化学装置在高温高压下的热安全性能、循环性能和阻抗特性。
表8展示了碳酸丙烯酯和丙酸丙酯的含量对电化学装置在高温高压下的热安全性能、低温倍率性能和循环性能的影响。实施例8-1至8-8与实施例1-1的区别仅在于表8所列参数。
表8
Figure PCTCN2021122705-appb-000012
参见表8中的电化学测试结果可以看出，相较于实施例8-7和8-8，实施例1-1和8-1至8-6在电解液中同时添加了碳酸丙烯酯和丙酸丙酯，其对应得到的电化学装置在高温高压下表现出更为优异的热安全性能、低温倍率性能和循环性能。而相较于实施例8-4至8-6，实施例8-1至8-3中的碳酸丙烯酯和丙酸丙酯的含量同时满足15≤y+z≤70且1≤z/y≤5，其对应得到的电化学装置在高温高压下的电化学性能有了进一步的改进，尤其是低温倍率性能有了大幅度的提升。
表9展示了电解液中的溶剂和添加剂对电化学装置在高温高压下的热安全性能和循环性能的影响。实施例9-1至9-17与实施例1-1的区别仅在于表9所列参数。
表9
Figure PCTCN2021122705-appb-000013
Figure PCTCN2021122705-appb-000014
参见表9中的电化学测试结果可以看出，当在电解液中组合使用具有氰基的化合物、碳酸丙烯酯、丙酸丙酯、氟代碳酸乙烯酯、1,3-丙磺酸内酯、硫酸乙烯酯、碳酸亚乙烯酯、1-丙基磷酸环酐时，所得到的电化学装置在高温高压下表现出非常优异的热安全性能、高温下的存储性能和循环性能。
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 (22)

  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：
    集流体；以及
    正极活性物质层，所述正极活性物质层位于所述集流体的至少一个表面上，且包括第一正极活性物质层和第二正极活性物质层，其中所述第一正极活性物质层位于所述集流体和所述第二正极活性物质层之间；
    其中所述集流体与所述第一正极活性物质层之间的粘结力为F 1N/m，所述第二正极活性物质层的内聚力为F 2N/m，所述正极满足：F 1/F 2≥6。
  2. 根据权利要求1所述的电化学装置，其中F 1≥200。
  3. 根据权利要求1所述的电化学装置，其中所述第一正极活性物质层包括第一粘结剂，所述第一粘结剂满足如下条件中的至少一者：
    (1)所述第一粘结剂具有水溶性；
    (2)所述第一粘结剂具有不饱和酸官能团；
    (3)所述第一粘结剂包括具有极性官能团的聚丙烯酸酯；
    (4)基于所述第一正极活性物质层的质量，所述第一粘结剂的质量分数为b％，其中2≤b≤20。
  4. 根据权利要求1所述的电化学装置，其中所述第一正极活性物质层包括第一粘结剂，基于所述第一正极活性物质层的质量，所述第一粘结剂的质量分数为b％，其中F 1和b满足：F 1≥200，2≤b≤20且F 1/b≥10。
  5. 根据权利要求1所述的电化学装置，其中所述第二正极活性物质层包括第二粘结剂，所述第二粘结剂满足如下条件中的至少一者：
    (1)所述第二粘结剂具有非水溶性；
    (2)所述第二粘结剂包括含氟聚合物；
    (3)所述第二粘结剂包括具有α晶型的聚偏氟乙烯；
    (4)基于所述第二正极活性物质层的质量，所述第二粘结剂的质量分数为a％，其中0.5≤a≤5。
  6. 根据权利要求1所述的电化学装置，其中所述第二正极活性物质层包括第二粘结剂；基于所述第二正极活性物质层的质量，所述第二粘结剂的质量分数 为a％，其中F 2和a的关系满足：5≤F 2≤60，0.5≤a≤5且F 2/a≥1。
  7. 根据权利要求1所述的电化学装置，其中所述第一正极活性物质层包括水溶性粘结剂，而所述第二正极活性物质层包括非水溶性粘结剂。
  8. 根据权利要求1所述的电化学装置，其中所述第一正极活性物质层包括第一粘结剂，基于所述第一正极活性物质层的质量，所述第一粘结剂的质量分数为b％；所述第二正极活性物质层包括第二粘结剂，基于所述第二正极活性物质层的质量，所述第二粘结剂的质量分数为a％；其中a和b满足：2.5≤a+b≤25；1≤b/a≤40。
  9. 根据权利要求1所述的电化学装置，其中所述第一正极活性物质层的厚度为H 1μm，所述正极活性物质层的厚度为Hμm，所述正极满足：H 1/H≤0.1。
  10. 根据权利要求9所述的电化学装置，其中0.1≤H 1≤5。
  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具有氰基的化合物。
  12. 根据权利要求11所述的电化学装置，其中基于所述电解液的质量，所述具有氰基的化合物的含量为x％，其中0.1≤x≤15。
  13. 根据权利要求11所述的电化学装置，其中F 1≥200，且F 1/x≥13.33。
  14. 根据权利要求11所述的电化学装置，其中所述具有氰基的化合物包括以下各者中的至少一者：丁二腈、戊二腈、己二腈、1,5-二氰基戊烷、1,6-二氰基己烷、四甲基丁二腈、2-甲基戊二腈、2,4-二甲基戊二腈、2,2,4,4-四甲基戊二腈、1,4-二氰基戊烷、1,2-二氰基苯、1,3-二氰基苯、1,4-二氰基苯、乙二醇双(丙腈)醚、3,5-二氧杂-庚二腈、1,4-二(氰基乙氧基)丁烷、二乙二醇二(2-氰基乙基)醚、三乙二醇二(2-氰基乙基)醚、四乙二醇二(2-氰基乙基)醚、1,3-二(2-氰基乙氧基)丙烷、1,4-二(2-氰基乙氧基)丁烷、1,5-二(2-氰基乙氧基)戊烷、乙二醇二(4-氰基丁基)醚、1,4-二氰基-2-丁烯、1,4-二氰基-2-甲基-2-丁烯、1,4-二氰基-2-乙基-2-丁烯、1,4-二氰基-2,3-二甲基-2-丁烯、1,4-二氰基-2,3-二乙基-2-丁烯、1,6-二氰基-3-己烯、1,6-二氰基-2-甲基-3-己烯、1,3,5-戊三甲腈、1,2,3-丙三甲腈、1,3,6-己三甲腈、1,2,6-己三甲腈、1,2,3-三(2-氰基乙氧基)丙烷、1,2,4-三(2-氰基乙氧基)丁烷、1,1,1-三(氰基乙氧基亚甲基)乙烷、1,1,1-三(氰基乙氧基亚甲基)丙烷、3-甲基-1,3,5-三(氰基乙氧基)戊烷、1,2,7-三(氰基乙氧基)庚烷、1,2,6-三(氰基乙氧基)己烷或1,2,5-三(氰基乙氧基)戊烷。
  15. 根据权利要求1所述的电化学装置，其中所述电解液包括碳酸丙烯酯。
  16. 根据权利要求15所述的电化学装置，其中基于所述电解液的质量，所述碳酸丙烯酯的含量为y％，其中2≤y≤25。
  17. 根据权利要求15所述的电化学装置，其中基于所述电解液的质量，所述碳酸丙烯酯的含量为y％，其中F 2/y≥0.5。
  18. 根据权利要求1所述的电化学装置，其中所述电解液包括丙酸丙酯，其中基于所述电解液的质量，所述丙酸丙酯的含量为z％，其中5≤z≤50。
  19. 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氰基的化合物和丙酸丙酯，其中基于所述电解液的质量，所述具有氰基的化合物的含量为x％，所述丙酸丙酯的含量为z％，其中12≤x+z≤65，且0.5≤z/x≤50。
  20. 根据权利要求1所述的电化学装置，其中所述电解液包括碳酸丙烯酯和丙酸丙酯，其中基于所述电解液的质量，所述碳酸丙烯酯的含量为y％，所述丙酸丙酯的含量为z％，其中15≤y+z≤70，且1≤z/y≤5。
  21. 根据权利要求1所述的电化学装置，其中所述电解液包括以下各者中的至少一者：氟代碳酸乙烯酯、1,3-丙磺酸内酯、硫酸乙烯酯、碳酸亚乙烯酯或1-丙基磷酸环酐。
  22. 一种电子装置，其包括根据权利要求1-21中任一项所述的电化学装置。
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