WO2023123353A1 - 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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WO2023123353A1
WO2023123353A1 PCT/CN2021/143675 CN2021143675W WO2023123353A1 WO 2023123353 A1 WO2023123353 A1 WO 2023123353A1 CN 2021143675 W CN2021143675 W CN 2021143675W WO 2023123353 A1 WO2023123353 A1 WO 2023123353A1
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Prior art keywords
positive electrode
active material
electrochemical device
electrode active
lithium
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PCT/CN2021/143675
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English (en)
French (fr)
Inventor
刘胜奇
王可飞
蔡小虎
郭俊
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东莞新能源科技有限公司
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Priority to CN202180042402.6A priority Critical patent/CN116097473A/zh
Priority to PCT/CN2021/143675 priority patent/WO2023123353A1/zh
Publication of WO2023123353A1 publication Critical patent/WO2023123353A1/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
    • 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
    • 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
    • H01M4/62—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
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • 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 present application at least provides an electrochemical device with improved high-temperature performance by improving the positive electrode of the electrochemical device, so as to solve the problems existing in the prior art to some extent.
  • the present application provides an electrochemical device, which includes a positive electrode, and the positive electrode includes: a positive electrode current collector; a positive electrode active material layer, and the positive electrode active material layer is formed on at least the positive electrode current collector.
  • the positive electrode active material layer includes a positive electrode active material and a binder, the binder has a density of a g/cm 3 and 0.6 ⁇ a ⁇ 1.5; and an insulating layer, the insulating layer forms In the edge region on the at least one surface of the positive current collector, the insulating layer contains aluminum element.
  • the insulating layer includes the adhesive.
  • the positive electrode active material layer and the insulating layer overlap each other to form an interaction region, and the width of the interaction region is W mm and 0 ⁇ W ⁇ 4.
  • the positive electrode active material layer and the insulating layer do not overlap.
  • the content of the aluminum element is x%, wherein 20 ⁇ x ⁇ 65.
  • the porosity of the binder is b%, 17 ⁇ b ⁇ 60, and 14 ⁇ b/a ⁇ 55.
  • the mass fraction of the positive electrode active material is M%, wherein 90 ⁇ M ⁇ 99.5 and 64 ⁇ M/a ⁇ 170.
  • the electrochemical device further includes an electrolyte, and the electrolyte includes an ether nitrile compound, wherein based on the total weight of the electrolyte, the mass fraction of the ether nitrile compound is c%, wherein 0.01 ⁇ c ⁇ 8.
  • the ether nitrile compound includes ethylene glycol bis(2-cyanoethyl) ether, 1,2,3-tris(2-cyanoethoxy)propane, 1,2,4 -Tris(2-cyanoethoxy)butane, 1,1,1-tris(cyanoethoxymethylene)ethane, 1,1,1-tris(cyanoethoxymethylene) ) propane, 3-methyl-1,3,5-tris(cyanoethoxy)pentane, 1,2,7-tris(cyanoethoxy)heptane, 1,2,6-tris( At least one of cyanoethoxy)hexane or 1,2,5-tris(cyanoethoxy)pentane.
  • the present application provides an electronic device comprising the electrochemical device according to the present application.
  • This application can significantly improve the structural stability of the positive electrode under high temperature and high pressure by providing an insulating layer with aluminum elements in the positive electrode and using a low-density binder in the positive electrode active material layer, thereby significantly improving the high temperature performance of the electrochemical device , especially to improve the overcharge safety performance of electrochemical devices and reduce their voltage drop under high temperature storage conditions.
  • Fig. 1 is a schematic top view of a positive electrode according to some embodiments of the present application, wherein an insulating layer and a positive electrode active material layer are arranged along the width direction of the positive electrode.
  • Fig. 2 is a schematic top view of the positive electrode according to other embodiments of the present application, wherein the insulating layer and the positive electrode active material layer are arranged along the length direction of the positive electrode.
  • Fig. 3 is a schematic top view of the positive electrode according to some other embodiments of the present application, wherein the insulating layer and the positive electrode active material layer are arranged along the width and length directions of the positive electrode.
  • Fig. 4 is a schematic top view of a positive electrode according to some embodiments of the present application, wherein the positive electrode active material layer does not overlap with the insulating layer.
  • 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 under high temperature and high pressure, the electrolyte is prone to oxidative decomposition on the surface of the positive electrode to generate a large amount of gas, causing the electrochemical device to bulge and destroy the electrode interface, thereby deteriorating the electrochemical performance of the electrochemical device.
  • 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 efficiency of the electrochemical device.
  • Internal resistance reduces high temperature cycle capacity retention and high temperature storage cell residual capacity.
  • the present application overcomes the above-mentioned defects in the prior art by providing an insulating layer with aluminum elements in the positive electrode and using a low-density binder in the positive electrode active material layer.
  • the positive electrode described in the present application includes a positive electrode current collector and a positive electrode active material layer, wherein the positive electrode active material layer contains a positive electrode active material and is formed in a central region on at least one surface of the positive electrode current collector.
  • the positive active material layer may be one or more layers. Each layer of the multilayer positive active material may contain the same or different positive active material.
  • the positive electrode further includes an insulating layer containing an aluminum element, wherein the insulating layer is formed on an edge region on the at least one surface of the positive electrode current collector; and the positive electrode
  • the active material layer further includes a binder, and the density of the binder is a g/cm 3 , where 0.6 ⁇ a ⁇ 1.5.
  • the term "central region” refers to a region at a certain distance from the edge of the positive electrode current collector along the width direction of the positive electrode or along the length direction of the positive electrode.
  • the edge of the central region is 2mm-80mm from the edge of the positive electrode collector and extends along the length direction of the positive electrode, the central region can have the same length as the positive electrode collector or be shorter than the length of the positive electrode collector (for example, 2mm-500mm).
  • the edge of the central region is 2mm-80mm away from the edge of the positive electrode collector and extends along the width direction of the positive electrode.
  • the central region can have the same width as the positive electrode collector or be narrower than the width of the positive electrode collector (for example, 4mm-160mm).
  • the term "edge area" refers to all or part of the area along the width direction of the positive electrode or along the length direction of the positive electrode except for the central area of the positive electrode current collector.
  • the edge region When along the width direction of the positive electrode, the edge region has at least the same length as the central region; when along the length direction of the positive electrode, the edge region has at least the same width as the central region.
  • the edge region (insulating layer) and the center region (positive electrode active material layer) are arranged along the width direction of the positive electrode. As shown in FIG.
  • the edge region (insulating layer) and the center region (positive electrode active material layer) are arranged along the length direction of the positive electrode. As shown in FIG. 3 , the edge region (insulating layer) and the center region (positive electrode active material layer) are arranged along the width and length directions of the positive electrode.
  • the insulating layer when the insulating layer and the positive active material layer are arranged along the width direction of the positive electrode, the insulating layer is at least as long as the positive active material layer. In some embodiments, when the insulating layer and the positive active material layer are arranged along the length direction of the positive electrode, the insulating layer is at least as wide as the positive active material layer.
  • the present application provides an insulating layer containing aluminum element at the edge region of the positive electrode current collector to enhance the structural stability of the positive electrode, thereby improving the electrochemical performance of the electrochemical device at high temperature.
  • the binder used in the positive active material layer of the present application has a lower density than conventionally used binders (the density is generally greater than 1.5 g/cm 3 ).
  • the density of the positive electrode binder When the density of the positive electrode binder is greater than 1.5g/ cm3 , it will affect the flexibility of the positive electrode to a certain extent, making it easy to break during the winding process; and when the density of the positive electrode binder is less than 0.6g/cm3 When 3 , the cohesive force of the binder is insufficient, thereby adversely affecting the electrochemical stability of the electrochemical device. Controlling the density of the positive electrode binder within the range of 0.6 g/ cm3 to 1.5 g/ cm3 not only achieves good adhesion, but also enhances the flexibility of the positive electrode and reduces the risk of fracture during the winding process. risk.
  • the low-density binder used in this application is easy to form a cavity structure with the surrounding active materials, which can accommodate the electrolyte.
  • This structure improves the wettability of the electrolyte and the positive active material to a certain extent, and effectively reduces the The side reaction produced by the interaction between the electrolyte and the active material.
  • the low-density binder can also be coated on the surface of the positive electrode active material particles to improve the stability of the interface of the positive electrode active material particles.
  • the combination of an insulating layer containing aluminum and a positive electrode active material layer containing a low-density binder not only helps to improve the high-temperature safety performance (for example, high-temperature overcharge performance) of the electrochemical device, but also helps to reduce its high-temperature storage performance. under the voltage drop.
  • 0.8 ⁇ a ⁇ 1.2 In some embodiments, a may be 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5 or within a range consisting of any two values above.
  • the insulating layer includes the low density adhesive described above.
  • the above-mentioned low-density binder in the insulating layer can promote the more uniform mixing of the binder and the aluminum element, optimize the bonding effect, and reduce the risk of the insulating layer falling off the current collector, thereby improving the use safety of the electrochemical device sex.
  • the above configuration also helps to improve the thermal stability of the insulating layer, so as to better play the role of the insulating layer. Based on at least the above factors, including the above-mentioned low-density binder in the insulating layer can further improve the safety performance of the battery cell such as voltage drop and overcharge deformation rate.
  • the insulating layer and the positive electrode active material layer overlap each other to form an interaction region, and the width of the interaction region is W mm, where 0 ⁇ W ⁇ 4.
  • the positive electrode active material layer is in contact with the insulating layer so that the components of the positive electrode active material layer and the components of the insulating layer co-exist at the interface (that is, overlap), and the formed area is called " Interactive Zone".
  • W may be 0.05, 0.01, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, or within a range consisting of any two of the foregoing values.
  • the existence of the interaction region can improve the stability of the boundary between the active material layer and the insulating layer and reduce the safety risk.
  • the insulating layer and the positive electrode active material layer do not overlap, as shown in FIG. 4 .
  • the content of the aluminum element is x%, wherein 20 ⁇ x ⁇ 65. In some embodiments, 35 ⁇ x ⁇ 0. In some embodiments, 40 ⁇ x ⁇ 50. In some embodiments, x may be 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, or within a range consisting of any two of the foregoing values.
  • the content of the aluminum element in the insulating layer is within the above range, the insulating layer is not easy to fall off during the cell manufacturing process or in the electrochemical device, and has good adhesion with the positive electrode current collector, which is conducive to improving the electrochemical device. High temperature storage voltage drop and safety performance.
  • the insulating layer includes at least one of Al 2 O 3 , AlF 3 , AlCl 3 , or AlN.
  • x/a is 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70 or is within a range consisting of any two values above.
  • x/a satisfies the above relationship, it can not only promote the more uniform distribution of the binder in the insulating layer, and promote the firm bonding of the insulating layer on the current collector, but also ensure that the insulating layer contains enough aluminum elements to avoid insulating The layer shrinks during the preparation process, and under the joint action of the above two, the safety performance of the electrochemical device can be further improved and the voltage drop in a high-temperature storage environment can be reduced.
  • the binder has a porosity of b%, where 17 ⁇ b ⁇ 60. In some embodiments, 25 ⁇ b ⁇ 55. In some embodiments, b may be 17, 20, 25, 30, 35, 40, 45, 50, 55, 60 or within a range consisting of any two values above.
  • the porosity of the binder is within the above range, the binder has good wettability and stability in the positive electrode active material slurry, which helps the positive electrode active material layer to be evenly coated on the positive electrode current collector, Thus improving the electrochemical consistency and electrochemical performance of the electrochemical device.
  • the density a and porosity b of the binder satisfy: 14 ⁇ b/a ⁇ 55. In some embodiments, 14 ⁇ b/a ⁇ 50.
  • b/a is 14, 15, 20, 25, 30, 35, 40, 45, 50, 55 or within a range consisting of any two of the above values.
  • the binder includes polyvinylidene fluoride (PVDF).
  • PVDF polyvinylidene fluoride
  • the mass fraction of the positive active material is M%, where 90 ⁇ M ⁇ 99.5. In some embodiments, 95 ⁇ M ⁇ 99. In some embodiments, M may be 90, 92, 94, 95, 96, 97, 98 or 99, or within a range consisting of any two of the above values.
  • the density a of the binder and the mass fraction M% of the positive electrode active material satisfy: 64 ⁇ M/a ⁇ 170. In some embodiments, 70 ⁇ M/a ⁇ 160. In some embodiments, M/a is 64, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, 150, 160, 170 or between any two values above. composition range.
  • the electrochemical device satisfies the above relationship, it can promote the dissolution of the binder in the positive electrode slurry, and it is more conducive to the uniform distribution of the binder in the positive electrode active material, improving the consistency of the electrode structure, thereby further improving the electrochemical performance. The safety performance of the device and reduce its voltage drop in high temperature storage environment.
  • 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.
  • the transition metals in the lithium transition metal composite oxide include V, Ti, Cr, Mn, Fe, Co, Ni, Cu, and the like.
  • lithium transition metal composite oxides include lithium cobalt composite oxides such as LiCoO 2 , lithium nickel composite oxides such as LiNiO 2 , lithium manganese composite oxides such as LiMnO 2 , LiMn 2 O 4 , Li 2 MnO 4 , lithium nickel manganese cobalt composite oxides such as LiNi 1/3 Mn 1/3 Co 1/3 O 2 , LiNi 0.5 Mn 0.3 Co 0.2 O 2 , etc., in which a part of the transition metal atom which is the main body of these lithium transition metal composite oxides is Na, K, B, F, Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, W and other elements substituted .
  • lithium transition metal composite oxides may include, but are not limited to, LiNi 0.5 Mn 0.5 O 2 , LiNi 0.85 Co 0.10 Al 0.05 O 2 , LiNi 0.33 Co 0.33 Mn 0.33 O 2 , LiNi 0.45 Co 0.10 Al 0.45 O 2 , LiMn 1.8 Al 0.2 O 4 and LiMn 1.5 Ni 0.5 O 4 etc.
  • combinations of lithium transition metal composite oxides include, but are not limited to, combinations of LiCoO 2 and LiMn 2 O 4 , wherein a part of Mn in LiMn 2 O 4 may be replaced by transition metals (for example, LiNi 0.33 Co 0.33 Mn 0.33 O 2 ), part of Co in LiCoO 2 can be replaced by transition metals.
  • the transition metals in the lithium-containing transition metal phosphate compound include V, Ti, Cr, Mn, Fe, Co, Ni, Cu, and the like.
  • lithium-containing transition metal phosphate compounds include iron phosphates such as LiFePO 4 , Li 3 Fe 2 (PO 4 ) 3 , LiFeP 2 O 7 , and cobalt phosphates such as LiCoPO 4 , wherein as these lithium transition metal phosphate compounds Some of the transition metal atoms of the main body are replaced by other elements such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si, etc.
  • 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.
  • a positive electrode active material having a material different from its composition adhered to the surface of the positive electrode active material is also referred to as a "positive electrode active material”.
  • lithium cobalt oxide or lithium nickel cobalt manganese oxide may be used as the "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 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.
  • the aqueous medium may include, but are not limited to, water, a mixed medium 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 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 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 average particle diameter of the positive electrode active material is within the above-mentioned range, a high tap density positive electrode active material can be obtained, and the decrease in the performance of the electrochemical device can be suppressed.
  • the preparation process of the positive electrode of the electrochemical device that is, when the positive electrode active material, the conductive material, the binder, etc. are slurried in a solvent and coated in the form of a film
  • problems such as the occurrence of streaks can be prevented.
  • the filling property at the time of 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 electrochemical device of the present application further includes an electrolytic solution, wherein the electrolytic solution includes an electrolyte, a solvent for dissolving the electrolyte, and an additive.
  • the electrolyte includes ether nitrile compounds.
  • the ether nitrile functional groups on the surface of the ether nitrile compound can form hydrogen bonds with the surface functional groups of the binder, promote the infiltration of the electrolyte and form an SEI film, and reduce the occurrence of side reactions while protecting the structural stability of the positive electrode, thereby improving the performance of the battery.
  • the ether nitrile compound includes ethylene glycol bis(2-cyanoethyl) ether, 1,2,3-tris(2-cyanoethoxy)propane, 1,2,4- Tris(2-cyanoethoxy)butane, 1,1,1-tris(cyanoethoxymethylene)ethane, 1,1,1-tris(cyanoethoxymethylene) Propane, 3-methyl-1,3,5-tris(cyanoethoxy)pentane, 1,2,7-tris(cyanoethoxy)heptane, 1,2,6-tris(cyanoethoxy) at least one of ethoxy)hexane or 1,2,5-tris(cyanoethoxy)pentane.
  • ether nitrile compounds can be used alone or in any combination. If the electrolyte contains two or more ether nitrile compounds, the content of the ether nitrile compound described in this application refers to the total content of the two or more ether nitriles in the electrolyte.
  • the mass fraction of the ether nitrile compound is c%, wherein 0.01 ⁇ c ⁇ 8. In some embodiments, 0.1 ⁇ c ⁇ 5. In some embodiments, c can be 0.01, 0.05, 0.1, 0.2, 0.3, 0.5, 0.6, 0.8, 1, 2, 3, 4, 5, 6, 7, 8 or any two of the above values. In the range.
  • the mass fraction c% of the ether nitrile compound and the density a of the binder satisfy: 0.4 ⁇ c/a ⁇ 12. In some embodiments, 0.5 ⁇ c/a ⁇ 10. In some embodiments, c/a can be 0.4, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 7, 8, 9, 10, 11, 12 or between Within the range formed by any two of the above values.
  • the electrochemical device satisfies the above relationship, the safety performance of the electrochemical device can be further improved and its voltage drop in a high-temperature storage environment can be reduced.
  • 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 Ether, chain ether, phosphorus-containing organic solvent, sulfur-containing organic solvent, or aromatic fluorinated solvent.
  • examples of the cyclic carbonate may include, but are not limited to, one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), or 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 or 2,2,2-trifluoroethyl methyl carbonate, etc.
  • examples of the cyclic carboxylate may include, but not limited to, one or more of ⁇ -butyrolactone or ⁇ -valerolactone. In some embodiments, 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 or 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, or 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 or 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 or 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 or 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 or 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 or 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 acetate, n-propyl acetate, ethyl acetate or combinations thereof.
  • the solvent used in the electrolyte of the present application comprises: ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, ⁇ -butyrolactone or a combination 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 at least one surface of the negative electrode current collector, wherein 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.
  • 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 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 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 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 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 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.
  • PVDF Polyvinylidene fluoride
  • the positive electrode active material lithium cobaltate (Hunan Shanshan LC9000E), carbon nanotubes and PVDF of different densities are mixed with N-methylpyrrolidone (NMP) according to the mass ratio of 97%:1%:2%, and stirred evenly to obtain the positive electrode slurry.
  • NMP N-methylpyrrolidone
  • Aluminum oxide or aluminum nitride and PVDF of different densities are mixed with NMP according to the mass ratio of 90%:10% to obtain the insulating layer slurry.
  • the positive electrode slurry and the insulating layer slurry were 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.
  • Voltage drop voltage before storage - voltage after storage.
  • the overcharge deformation rate of the lithium-ion battery is calculated according to the following formula:
  • Overcharge deformation rate [(T 2 -T 1 )/T 1 ] ⁇ 100%.
  • Table 1 shows the influence of the aluminum element content in the positive electrode insulating layer and the density of the binder in the positive electrode active material layer on the voltage drop and overcharge safety performance of lithium-ion batteries under high temperature storage.
  • the content x of the aluminum element is adjusted by adjusting the mass ratio of the aluminum-containing material in the slurry in the insulating layer to the binder.
  • the positive electrode includes an insulating layer with an aluminum element and a positive active material layer with a binder having a density in the range of 0.6 g/ cm to 1.5 g/cm 3 , the resulting electrochemical device exhibits Excellent high temperature safety performance, and has smaller voltage drop under high temperature storage.
  • Example 1-1 Comparing Example 1-1 and Comparative Example 1-4, it can be seen that by disposing an insulating layer containing aluminum on the positive electrode, the voltage drop and overcharge deformation rate of the electrochemical device described in Example 1-1 under high-temperature storage are both has been significantly reduced.
  • Table 2 shows the effect of the density and porosity of the cathode binder on the voltage drop and overcharge safety performance of Li-ion batteries under high-temperature storage.
  • Table 3 shows the influence of the mass fraction of the positive active material in the positive active material layer and the density of the binder in the positive active material layer on the voltage drop and overcharge safety performance of lithium-ion batteries stored at high temperatures.
  • the difference between Examples 3-1 to 3-9 in Table 3 and Example 1-1 lies in the parameters listed in Table 3.
  • Table 4 shows the effects of the content of ether nitrile compounds in the electrolyte and the density of the binder in the positive electrode active material layer on the voltage drop and overcharge safety performance of lithium-ion batteries stored at high temperatures.
  • the difference between Examples 4-1 to 4-22 in Table 4 and Example 1-1 lies in the parameters listed in Table 4.
  • Table 5 shows the effect of the binder in the insulating layer on the voltage drop and overcharge safety performance of Li-ion batteries under high-temperature storage.
  • the difference between Examples 5-1 to 5-6 in Table 5 and Example 1-1 lies in the parameters listed in Table 5.
  • the insulating layer When the insulating layer includes a low-density binder, it helps to further reduce the voltage drop and overcharge deformation rate of the electrochemical device under high temperature storage.
  • 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，所述正极包括：正极集流体；正极活性物质层，所述正极活性物质层形成在所述正极集流体的至少一个表面上的中心区域，所述正极活性物质层包括正极活性物质和粘结剂，所述粘结剂的密度为a g/cm 3且0.6≤a≤1.5；以及绝缘层，所述绝缘层形成在所述正极集流体的所述至少一个表面上的边缘区域，且所述绝缘层含有铝元素。本申请对正极的上述配置能够改善电化学装置的高温存储电压降和安全性能。

Description

电化学装置和电子装置 技术领域
本申请涉及储能领域，具体涉及一种电化学装置和电子装置，特别是锂离子电池。
背景技术
近年来，随着智能手机、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，消费者对电化学装置(例如，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能会明显恶化。同时，随着全球变暖等恶劣环境加剧(如印度、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
本申请至少通过改进电化学装置的正极来提供一种具有改进的高温性能的电化学装置，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，所述正极包括：正极集流体；正极活性物质层，所述正极活性物质层形成在所述正极集流体的至少一个表面上的中心区域，所述正极活性物质层包括正极活性物质和粘结剂，所述粘结剂的密度为a g/cm 3且0.6≤a≤1.5；以及绝缘层，所述绝缘层形成在所述正极集流体的所述至少一个表面上的边缘区域，且所述绝缘层含有铝元素。
根据本申请的实施例，所述绝缘层包括所述粘结剂。
根据本申请的实施例，所述正极活性物质层和所述绝缘层相互交叠以形成交互区，所述交互区的宽度为W mm且0＜W≤4。
根据本申请的实施例，所述正极活性物质层和所述绝缘层不交叠。
根据本申请的实施例，基于所述绝缘层的重量，所述铝元素的含量为x％， 其中20≤x≤65。
根据本申请的实施例，20≤x/a≤70。
根据本申请的实施例，0.8≤a≤1.2。
根据本申请的实施例，所述粘结剂的孔隙率为b％，17≤b≤60，且14≤b/a≤55。
根据本申请的实施例，基于所述正极活性物质层的总重量，所述正极活性物质的质量分数为M％，其中90≤M≤99.5且64≤M/a≤170。
根据本申请的实施例，所述电化学装置还包括电解液，所述电解液包括醚腈化合物，其中基于所述电解液的总重量，所述醚腈化合物的质量分数为c％，其中0.01≤c≤8。
根据本申请的实施例，所述醚腈化合物包括乙二醇二(2-氰基乙基)醚、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。
根据本申请的实施例，0.4≤c/a≤2。
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。
本申请通过在正极中设置具有铝元素的绝缘层并在正极活性物质层中采用低密度粘结剂可显著改善正极在高温高压下的结构稳定性，由此可显著改进电化学装置的高温性能，尤其是提升电化学装置的过充安全性能并降低其在高温存储条件下的电压降。
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。
附图说明
图1是根据本申请一些实施例的正极的俯视示意图，其中绝缘层和正极活性物质层沿正极的宽度方向设置。
图2是根据本申请另一些实施例的正极的俯视示意图，其中绝缘层和正极活性物质层沿正极的长度方向设置。
图3是根据本申请又一些实施例的正极的俯视示意图，其中绝缘层和正极活 性物质层沿正极的宽度和长度方向设置。
图4是根据本申请一些实施例的正极的俯视示意图，其中正极活性物质层与绝缘层不交叠。
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，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，从而导致电化学装置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，导致电化学装置鼓胀并破坏电极界面，从而恶化电化学装置的电化学性能。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，这会进一步增大电化学装置的内阻，降低高温循环容量保持率和高温储存电芯残余容量。上述这些因素会使得电化学装置存在极大的安全隐患。
在至少一个方面，本申请通过在正极中设置具有铝元素的绝缘层并在正极活性物质层中采用低密度粘结剂以克服现有技术存在的上述缺陷。
具体地，本申请所述的正极包括正极集流体和正极活性物质层，其中所述正 极活性物质层包含正极活性物质，且形成在所述正极集流体的至少一个表面上的中心区域。所述正极活性物质层可以是一层或多层。多层正极活性物质中的每层可以包含相同或不同的正极活性物质。
本申请所述的正极的主要特征在于，所述正极还包括含有铝元素的绝缘层，其中所述绝缘层形成在所述正极集流体的所述至少一个表面上的边缘区域；以及所述正极活性物质层还包括粘结剂，所述粘结剂的密度为a g/cm 3，其中0.6≤a≤1.5。
如本文中所使用，术语“中心区域”是指沿正极的宽度方向或沿正极的长度方向上距离正极集流体边缘一定距离的区域。当沿正极的宽度方向时，中心区域边缘距离正极集流体的边缘2mm-80mm且沿正极的长度方向延伸，中心区域可与正极集流体具有相同的长度或比正极集流体的长度短(例如，2mm-500mm)。当沿正极的长度方向时，中心区域边缘距离正极集流体的边缘2mm-80mm且沿正极的宽度方向延伸，中心区域可与正极集流体具有相同的宽度或比正极集流体的宽度窄(例如，4mm-160mm)。如本文中所使用，术语“边缘区域”是指沿正极的宽度方向或沿正极的长度方向上除正极集流体的中心区域以外的全部或部分区域。当沿正极的宽度方向时，边缘区域具有至少与中心区域相同的长度；当沿正极的长度方向时，边缘区域具有至少与中心区域相同的宽度。如图1所示，边缘区域(绝缘层)和中心区域(正极活性物质层)沿正极的宽度方向设置。如图2所示，边缘区域(绝缘层)和中心区域(正极活性物质层)沿正极的长度方向设置。如图3所示，边缘区域(绝缘层)和中心区域(正极活性物质层)沿正极的宽度和长度方向设置。
在一些实施例中，当绝缘层和正极活性物质层沿正极的宽度方向设置时，所述绝缘层至少与所述正极活性物质层等长。在一些实施例中，当绝缘层和正极活性物质层沿正极的长度方向设置时，所述绝缘层至少与所述正极活性物质层等宽。
一方面，本申请在正极集流体的边缘区域处设置含有铝元素的绝缘层可增强正极的结构稳定性，由此可改善电化学装置在高温下的电化学性能。另一方面，本申请在正极活性物质层中使用的粘结剂相较于常规使用的粘结剂(密度通常大于1.5g/cm 3)具有更低的密度。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；而当正极粘结剂的 密度小于0.6g/cm 3时，粘结剂的粘结力不足，从而不利地影响电化学装置的电化学稳定性。将正极粘结剂的密度控制在0.6g/cm 3至1.5g/cm 3的范围内，不仅可实现良好的粘结性，还能增强正极的柔韧度，降低其在卷绕过程中断裂的风险。同时，本申请使用的低密度粘结剂易与周边活性材料形成腔型结构，其中可容纳电解液，该结构在一定程度上改善电解液与正极活性材料的浸润性的同时，还有效减少了电解液与活性材料作用产生的副反应。另外，所述低密度粘结剂还能够包覆在正极活性物质颗粒的表面，改善正极活性物质颗粒界面的稳定性。含有铝元素的绝缘层与含有低密度粘结剂的正极活性物质层的组合不仅有助于提升电化学装置的高温安全性能(例如，高温过充性能)，还有助于降低其在高温存储下的电压降。
在一些实施例中，0.8≤a≤1.2。在一些实施例中，a可以为0.6、0.7、0.8、0.9、1.0、1.1、1.2、1.3、1.4、1.5或者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，绝缘层包括上述低密度粘结剂。通过在绝缘层中使用上述低密度粘结剂，能够促进粘结剂与铝元素更均匀地混合，优化粘结效果，降低绝缘层从集流体上脱落的风险，从而改善电化学装置的使用安全性。另外，上述配置还有助于提升绝缘层的热稳定性，从而更好地发挥绝缘层的作用。至少基于上述因素，在绝缘层中包括上述低密度粘结剂能够进一步改善电芯的电压降及过充变形率等安全性能。
在一些实施例中，绝缘层和正极活性物质层相互交叠以形成交互区，所述交互区的宽度为W mm，其中0＜W≤4。如图1-3所示，正极活性物质层与绝缘层相接触使得正极活性物质层的组分和绝缘层的组分共同存在于界面处(即，相交叠)，所形成的区域称为“交互区”。在一些实施例中，W可以为0.05、0.01、0.5、1、1.5、2、2.5、3、3.5、4或者处于由上述数值中的任何两者组成的范围内。交互区的存在可以改善活性物质层和绝缘层边界稳定性，降低安全风险。
在一些实施例中，绝缘层和正极活性物质层不交叠，如图4所示。
在一些实施例中，基于所述绝缘层的重量，所述铝元素的含量为x％，其中20≤x≤65。在一些实施例中，35≤x≤0。在一些实施例中，40≤x≤50。在一些实施例中，x可以为20、25、30、35、40、45、50、55、60、65或者处于由上述数值中的任何两者组成的范围内。当绝缘层中铝元素的含量在上述范围内时，绝缘层在电芯制造过程或在电化学装置内不易脱落，且与正极集流体之间具有良 好的粘结性，有利于改善电化学装置的高温存储电压降和安全性能。
在一些实施例中，绝缘层包括Al 2O 3、AlF 3、AlCl 3或AIN中的至少一者。
在一些实施例中，20≤x/a≤70。在一些实施例中，30≤x/a≤55。在一些实施例中，x/a为20、25、30、35、40、45、50、55、60、65、70或者处于由上述任意两个数值所组成的范围内。当x/a满足上述关系时，不仅能够促进粘结剂在绝缘层中更均匀的分布，促使绝缘层牢固地粘结在集流体上，而且能够确保绝缘层中含有足够的铝元素，避免绝缘层在制备过程中发生收缩，在上述二者的共同作用下能够进一步改善电化学装置的安全性能并降低其在高温存储环境下的电压降。
在一些实施例中，所述粘结剂的孔隙率为b％，其中17≤b≤60。在一些实施例中，25≤b≤55。在一些实施例中，b可以为17、20、25、30、35、40、45、50、55、60或者处于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，粘结剂在正极活性物质浆料中具有良好的浸润性和稳定性，有助于正极活性物质层可均匀地涂布在正极集流体上，从而改善电化学装置的电化学一致性和电化学性能。在一些实施例中，所述粘结剂的密度a和其孔隙率b满足：14≤b/a≤55。在一些实施例中，14≤b/a≤50。在一些实施例中，b/a为14、15、20、25、30、35、40、45、50、55或者处于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，更有利于粘结剂在正极浆料中的浸润和分散，并且更有利于正极浆料容纳于粘结剂的腔型结构中，从而能够进一步改善电化学装置的安全性能并降低其在高温存储环境下的电压降。
在一些实施例中，所述粘结剂包括聚偏二氟乙烯(PVDF)。
在一些实施例中，基于所述正极活性物质层的总重量，所述正极活性物质的质量分数为M％，其中90≤M≤99.5。在一些实施例中，95≤M≤99。在一些实施例中，M可以为90、92、94、95、96、97、98或99，或者处于由上述任意两个数值所组成的范围内。当正极活性物质在正极活性物质层中的质量分数满足上述关系时，能够显著提高电化学装置的能量密度。
在一些实施例中，所述粘结剂的密度a和所述正极活性物质的质量分数M％满足：64≤M/a≤170。在一些实施例中，70≤M/a≤160。在一些实施例中，M/a为64、65、70、75、80、85、90、95、100、110、120、130、140、150、160、170或者处于由上述任意两个数值所组成的范围内。当电化学装置满足上述关系时，能够促进粘结剂在正极浆料中的溶解，并且更有利于粘结剂均匀地分布在正 极活性物质中，改善电极结构的一致性，从而进一步改善电化学装置的安全性能并降低其在高温存储环境下的电压降。
正极活性物质的种类没有特别限制，只要是能够以电化学方式吸藏和释放金属离子(例如，锂离子)即可。在一些实施例中，正极活性物质为含有锂和至少一种过渡金属的物质。正极活性物质的实例可包括，但不限于，锂过渡金属复合氧化物和含锂过渡金属磷酸化合物。
在一些实施例中，锂过渡金属复合氧化物中的过渡金属包括V、Ti、Cr、Mn、Fe、Co、Ni、Cu等。在一些实施例中，锂过渡金属复合氧化物包括LiCoO 2等锂钴复合氧化物、LiNiO 2等锂镍复合氧化物、LiMnO 2、LiMn 2O 4、Li 2MnO 4等锂锰复合氧化物、LiNi 1/3Mn 1/3Co 1/3O 2、LiNi 0.5Mn 0.3Co 0.2O 2等锂镍锰钴复合氧化物，其中作为这些锂过渡金属复合氧化物的主体的过渡金属原子的一部分被Na、K、B、F、Al、Ti、V、Cr、Mn、Fe、Co、Li、Ni、Cu、Zn、Mg、Ga、Zr、Si、Nb、Mo、Sn、W等其它元素所取代。锂过渡金属复合氧化物的实例可包括，但不限于，LiNi 0.5Mn 0.5O 2、LiNi 0.85Co 0.10Al 0.05O 2、LiNi 0.33Co 0.33Mn 0.33O 2、LiNi 0.45Co 0.10Al 0.45O 2、LiMn 1.8Al 0.2O 4和LiMn 1.5Ni 0.5O 4等。锂过渡金属复合氧化物的组合的实例包括，但不限于，LiCoO 2与LiMn 2O 4的组合，其中LiMn 2O 4中的一部分Mn可被过渡金属所取代(例如，LiNi 0.33Co 0.33Mn 0.33O 2)，LiCoO 2中的一部分Co可被过渡金属所取代。
在一些实施例中，含锂过渡金属磷酸化合物中的过渡金属包括V、Ti、Cr、Mn、Fe、Co、Ni、Cu等。在一些实施例中，含锂过渡金属磷酸化合物包括LiFePO 4、Li 3Fe 2(PO 4) 3、LiFeP 2O 7等磷酸铁类、LiCoPO 4等磷酸钴类，其中作为这些锂过渡金属磷酸化合物的主体的过渡金属原子的一部分被Al、Ti、V、Cr、Mn、Fe、Co、Li、Ni、Cu、Zn、Mg、Ga、Zr、Nb、Si等其它元素所取代。
在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，“正极活性物质”可以使用钴酸锂或镍钴锰酸锂。
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。
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，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。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还包括电解液，其中所述电解液包括电解质、溶解所述电解质的溶剂和添加剂。
在一些实施例中，所述电解液包括醚腈化合物。醚腈化合物表面的醚腈官能 团能够与粘结剂表面官能团形成氢键，促进电解液的浸润并形成SEI膜，在保护正极结构稳定性的同时降低副反应的发生，从而改善电芯性能。
在一些实施例中，所述醚腈化合物包括乙二醇二(2-氰基乙基)醚、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。
上述醚腈化合物可单独使用，也可经任意组合使用。若电解液中含有两种或更多种醚腈化合物时，本申请所述的醚腈化合物的含量是指该两种或更多种醚腈在电解液中的总含量。
在一些实施例中，基于电解液的总重量，所述醚腈化合物的质量分数为c％，其中0.01≤c≤8。在一些实施例中，0.1≤c≤5。在一些实施例中，c可以为0.01、0.05、0.1、0.2、0.3、0.5、0.6、0.8、1、2、3、4、5、6、7、8或者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，所述醚腈化合物的质量分数c％和粘结剂的密度a满足：0.4≤c/a≤12。在一些实施例中，0.5≤c/a≤10。在一些实施例中，c/a可以为0.4、0.5、1、1.5、2、2.5、3、3.5、4、4.5、5、5.5、6、7、8、9、10、11、12或者处于由上述任意两个数值所组成的范围内。当电化学装置满足上述关系时，能够进一步改善电化学装置的安全性能并降低其在高温存储环境下的电压降。
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、含硫有机溶剂或芳香族含氟溶剂。
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)或碳酸亚丁酯。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或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γ-丁内酯或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、特戊酸甲酯或特戊酸乙酯等。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、三氟乙酸丁酯或三氟乙酸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、1,4-二氧六环或二甲氧基丙烷。
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-乙氧基甲氧基乙烷或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)酯或磷酸三(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、硫酸二乙酯或硫酸二丁酯。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、六氟苯或三氟甲基苯。
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、乙酸乙酯或其组合。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-丁内酯或其组合。
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至少一个表面上的负极活 性物质层，其中所述负极活性物质层包含负极活性物质。负极活性物质层可以是一层或多层，多层负极活性物质中的每层可以包含相同或不同的负极活性物质。负极活性物质为任何能够可逆地嵌入和脱出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
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。
VI、电子装置
本申请另提供了一种电子装置，其包括根据本申请所述的电化学装置。
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。
一、锂离子电池的制备
1、负极的制备
将人造石墨、丁苯橡胶和羧甲基纤维素钠按照96％:2％:2％的质量比例与去离子水混合，搅拌均匀，得到浆料。将浆料涂布在9μm的铜箔上。干燥，冷压，再经过裁片、焊接极耳，得到负极。
2、正极的制备
通过控制阶梯升温速度和压力以及各阶梯的时间，合成具有不同密度的聚偏 氟乙烯(PVDF)。
将正极活性材料钴酸锂(湖南杉杉LC9000E)、碳纳米管和不同密度的PVDF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。将氧化铝或者氮化铝和不同密度的PVDF按照90％:10％的质量比例与NMP混合，得到绝缘层浆料。将所述正极浆料和所述绝缘层浆料涂布在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％。根据需要，在基础电解液中加入不同含量的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 乙二醇二(2-氰基乙基)醚 EDN
1,2,3-三(2-氰基乙氧基)丙烷 TCEP 1,2,4-三(2-氰基乙氧基)丁烷 MJ-2
1,1,1-三(氰基乙氧基亚甲基)乙烷 MJ-3 1,1,1-三(氰基乙氧基亚甲基)丙烷 MJ-4
3-甲基-1,3,5-三(氰基乙氧基)戊烷 MJ-5 1,2,7-三(氰基乙氧基)庚烷 MJ-6
1,2,6-三(氰基乙氧基)己烷 MJ-7 1,2,5-三(氰基乙氧基)戊烷 MJ-8
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、锂离子电池在高温存储下的电压降测试
在25℃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3.2V，静置5分钟，然后测试电压。在85℃下存储24小时后，复测电压。锂离子电池在高温下存储的电压降按照下式进行计算：
电压降＝存储前电压-存储后电压。
2、锂离子电池的过充变形率测试
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60分钟，测量锂离子电池的厚度T 1。然后 以0.1C倍率恒流充电60分钟，静置30分钟，重复这一步骤5次，使锂离子电池达到150％荷电状态(SOC)，测量锂离子电池的厚度T 2。锂离子电池的过充变形率按照下式进行计算：
过充变形率＝[(T 2-T 1)/T 1]×100％。
三、测试结果
表1展示了正极绝缘层中铝元素含量和正极活性物质层中粘结剂的密度对锂离子电池在高温存储下的电压降和过充安全性能的影响。其中，各实施例中，通过调整绝缘层中浆料中的含铝材料与粘结剂的质量比调节铝元素含量x。
表1
Figure PCTCN2021143675-appb-000001
上述结果表明，当正极包括具有铝元素的绝缘层，同时包括具有密度处于0.6g/cm 3至1.5g/cm 3的范围的粘结剂的正极活性物质层时，得到的电化学装置表现出优异的高温安全性能，且在高温存储下具有更小的电压降。
将实施例1-1与对比例1-4可知，通过在正极上设置含有铝元素的绝缘层，实施例1-1所述的电化学装置在高温存储下的电压降和过充变形率均得到了显著 的下降。
此外，将实施例1-8至1-15与对比例1-1和1-2进行对比，可以看出，在绝缘层相同的情况下，当正极活性物质层采用的粘结剂的密度处于0.6g/cm 3至1.5g/cm 3的范围时，得到的电化学装置在高温存储下的电压降和过充变形率显著下降。
将实施例1-1至1-6进行对比，可以看出，当铝元素在绝缘层中的含量处于20％至65％范围内时，对应得到的电化学装置表现出更优异的高温安全性能，且在高温存储下具有更小的电压降。
此外，从表1还可以看出，当20≤x/a≤70时，能够进一步优化电化学装置的电化学性能。
表2展示了正极粘结剂的密度和孔隙率对锂离子电池在高温存储下的电压降和过充安全性能的影响。表2中的实施例2-1至2-12与实施例1-1的区别仅在于表2所列参数。
表2
Figure PCTCN2021143675-appb-000002
参见表2中的电化学测试结果可以看出，当正极粘结剂的密度a g/cm 3和孔隙率b％满足17≤b≤60且14≤b/a≤55时，得到的电化学装置表现出更优异的高温安全性能，且在高温存储下具有更小的电压降。
表3展示了正极活性物质层中的正极活性物质的质量分数和正极活性物质层中粘结剂的密度对锂离子电池在高温下存储的电压降和过充安全性能的影响。 表3中的实施例3-1至3-9与实施例1-1的区别仅在于表3所列参数。
表3
Figure PCTCN2021143675-appb-000003
参见表3中的电化学测试结果可以看出，当正极活性物质的质量分数M％和正极活性物质层中粘结剂的密度a g/cm 3满足64≤M/a≤170时，得到的电化学装置表现出更优异的高温安全性能，且在高温存储下具有更小的电压降。
表4展示了电解液中的醚腈化合物含量和正极活性物质层中粘结剂的密度对锂离子电池在高温下存储的电压降和过充安全性能的影响。表4中的实施例4-1至4-22与实施例1-1的区别仅在于表4所列参数。
表4
Figure PCTCN2021143675-appb-000004
Figure PCTCN2021143675-appb-000005
参见表4中的电化学测试结果可以看出，在电解液中添加醚腈化合物后，对应得到的电化学装置在高温存储下的电压降以及过充变形率均得以显著下降。进一步的，当电解液中醚腈化合物的质量分数c％与粘结剂的密度为a g/cm 3满足0.4≤c/a≤12时，电化学装置的性能改善更为明显。
表5展示了绝缘层中的粘结剂对锂离子电池在高温存储下的电压降和过充安全性能的影响。表5中的实施例5-1至5-6与实施例1-1的区别仅在于表5所列参数。
表5
Figure PCTCN2021143675-appb-000006
当绝缘层包括低密度粘结剂时，有助于进一步降低电化学装置在高温存储下的电压降以及过充变形率。
整个说明书中对“实施例”、“部分实施例”、“一个实施例”、“另一举例”、“举例”、“具体举例”或“部分举例”的引用，其所代表的意思是在本申请中的至少一个实施例或举例包含了该实施例或举例中所描述的特定特征、结构、材料或特性。因此，在整个说明书中的各处所出现的描述，例如：“在一些实施例中”、“在实施例中”、“在一个实施例中”、“在另一个举例中”，“在一个举例中”、“在特定举例中”或“举例”，其不必然是引用本申请中的相同的实施例或示例。此 外，本文中的特定特征、结构、材料或特性可以以任何合适的方式在一个或多个实施例或举例中结合。
尽管已经演示和描述了说明性实施例，本领域技术人员应该理解上述实施例不能被解释为对本申请的限制，并且可以在不脱离本申请的精神、原理及范围的情况下对实施例进行改变，替代和修改。

Claims (13)

  1. 一种电化学装置，其包括正极，所述正极包括：
    正极集流体；
    正极活性物质层，所述正极活性物质层形成在所述正极集流体的至少一个表面上的中心区域，所述正极活性物质层包括正极活性物质和粘结剂，所述粘结剂的密度为a g/cm 3且0.6≤a≤1.5；以及
    绝缘层，所述绝缘层形成在所述正极集流体的所述至少一个表面上的边缘区域，且所述绝缘层含有铝元素。
  2. 根据权利要求1所述的电化学装置，其中所述绝缘层包括所述粘结剂。
  3. 根据权利要求1所述的电化学装置，其中所述正极活性物质层和所述绝缘层相互交叠以形成交互区，所述交互区的宽度为W mm且0＜W≤4。
  4. 根据权利要求1所述的电化学装置，其中所述正极活性物质层和所述绝缘层不交叠。
  5. 根据权利要求1所述的电化学装置，其中基于所述绝缘层的重量，所述铝元素的含量为x％，其中20≤x≤65。
  6. 根据权利要求5所述的电化学装置，其中20≤x/a≤70。
  7. 根据权利要求1所述的电化学装置，其中0.8≤a≤1.2。
  8. 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％，17≤b≤60，且14≤b/a≤55。
  9. 根据权利要求1所述的电化学装置，其中基于所述正极活性物质层的总重量，所述正极活性物质的质量分数为M％，其中90≤M≤99.5且64≤M/a≤170。
  10. 根据权利要求1所述的电化学装置，其中所述电化学装置还包括电解液，所述电解液包括醚腈化合物，其中基于所述电解液的总重量，所述醚腈化合物的质量分数为c％，其中0.01≤c≤8。
  11. 根据权利要求10所述的电化学装置，其中所述醚腈化合物包括乙二醇二(2-氰基乙基)醚、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。
  12. 根据权利要求10所述的电化学装置，其中0.4≤c/a≤12。
  13. 一种电子装置，其包括根据权利要求1-12中任一项所述的电化学装置。
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