Electrochemical apparatus and electronic apparatus

Abstract

The present application provides an electrochemical apparatus and an electronic apparatus. The electrochemical apparatus comprises a positive electrode sheet and an electrolyte, and the positive electrode sheet comprises a positive electrode current collector, a first material layer, and a positive electrode material layer. The first material layer comprises inorganic particles, a first binder, and a first conductive agent. The first material layer is disposed on at least one surface of the positive electrode current collector, and the positive electrode material layer is disposed between the positive electrode current collector and the first material layer. The ratio of the length of the first material layer to the length of the positive electrode current collector is X%, where 50≤X≤98. The electrolyte comprises a first component and a second component. The first component comprises at least one of a compound represented by formula I-1 or a compound represented by formula II-1, and the second component comprises a compound represented by formula III. Based on the mass of the electrolyte, the mass percentage content of the first component is A%, and the mass percentage content of the second component is B%, where 40≤A+B≤90. By means of the above configuration, the cycling performance of the electrochemical apparatus under high voltage and high temperature conditions can be improved while thermal safety performance is also maintained.

Description

An electrochemical device and an electronic device Technical Field

[0001] This application relates to the field of electrochemical technology, and in particular to an electrochemical device and an electronic device. Background Technology

[0002] Electrochemical devices, such as lithium-ion batteries, are widely used in electric vehicles and consumer electronics due to their advantages such as high energy density, high output power, long cycle life, and environmental friendliness. As the application scope of lithium-ion batteries continues to expand and their application scenarios become more diverse, the market is placing higher demands on their electrochemical performance. For example, to meet the market demand for high-energy-density batteries, a common technical approach is to increase the upper limit of the charging cutoff voltage. Furthermore, with the diversification of application scenarios, lithium-ion batteries must be able to adapt to various climatic conditions, such as maintaining good cycle performance under high-temperature conditions.

[0003] As one of the key materials in lithium-ion batteries, the performance of the electrolyte determines the maximum performance of other materials in the battery, such as the positive electrode, negative electrode, and separator. To improve the cycle performance of lithium-ion batteries under harsh conditions such as high voltage and high temperature, the composition of the electrolyte is usually optimized. Summary of the Invention

[0004] The purpose of this application is to provide an electrochemical device and an electronic device to improve the cycle performance of the electrochemical device under high voltage and high temperature while taking into account the thermal safety performance of the electrochemical device. The specific technical solution is as follows:

[0005] A first aspect of this application provides an electrochemical device comprising a positive electrode and an electrolyte. The positive electrode comprises a positive current collector, a first material layer, and a positive material layer. The first material layer comprises inorganic particles, a first binder, and a first conductive agent. The first material layer is disposed on at least one surface of the positive current collector, and the positive material layer is disposed between the positive current collector and the first material layer. The ratio of the length of the first material layer to the length of the positive current collector is X%, 50 ≤ X ≤ 98, preferably 80 ≤ X ≤ 98. The electrolyte comprises a first component and a second component. The first component comprises at least one compound of formula I-1 or formula II-1.

[0006] Among them, R 11 and R 12 Each is independently either substituted or unsubstituted C1-C 10 Alkyl, wherein R 11 and R 12 At least one of them has been replaced; R 21 and R 22 Each is independently either substituted or unsubstituted C1-C10 Alkyl, wherein R 21 and R 22 At least one of the components is substituted; when substituted, each substituent is independently a fluorine atom; the second component includes a compound of formula III:

[0007] Among them, R 41 R 42 R 43 R 44 Each is independently H, F, substituted or unsubstituted C1-C3 alkyl group, and when substituted, the substituent is a fluorine atom, R. 41 R 42 R 43 R 44 At least one of the components contains F; based on the mass of the electrolyte, the mass percentage of the first component is A%, and the mass percentage of the second component is B%, satisfying: 40≤A+B≤90. The electrolyte includes the first and second components within the scope of this application, and a first material layer is disposed on the positive electrode current collector, which is beneficial to improving the oxidation resistance of the electrolyte and improving the solvation structure of active metal ions (e.g., lithium ions). In addition, it is beneficial to reduce the direct contact between the electrolyte, the positive electrode active material, and the positive electrode current collector, thereby reducing heat generation. This is beneficial to improving the cycle performance of the electrochemical device under high voltage and high temperature, while also taking into account the thermal safety performance of the electrochemical device.

[0008] In some embodiments of this application, 5 ≤ B ≤ 15. The electrolyte includes a first component and a second component within the scope of this application, and the mass percentage of the second component is controlled within the scope of this application. This facilitates the formation of a stable solid electrolyte interphase (SEI) film on the negative electrode surface. The synergistic effect of the first and second components further improves the cycling performance of the electrochemical device under high voltage and high temperature.

[0009] In some embodiments of this application, 4.3 ≤ A / B ≤ 19. Controlling the A / B ratio within the range of this application can further improve the stability of the positive and negative electrode interfaces and reduce the impedance of the positive and negative electrode interfaces, thereby further improving the cycle performance of the electrochemical device under high voltage and high temperature.

[0010] In some embodiments of this application, the electrolyte includes a third component, which includes at least one of a compound of formula I-2 or a compound of formula II-2:

[0011] Among them, R 13 R 14 R 23 and R 24 Each independently is C1-C 10Alkyl group; based on the mass of the electrolyte, the mass percentage of the third component is C%, 0 < C ≤ 50. Introducing a third component into the electrolyte, which includes the first and second components, and controlling the mass percentage of the third component within the scope of this application, is beneficial for reducing costs, while the electrochemical device still maintains good cycle performance and thermal safety.

[0012] In some embodiments of this application, the compound of formula I-1 includes at least one of the following compounds:

[0013] Compounds of formula II-1 include at least one of the following compounds:

[0014] The electrolyte includes at least one of the compounds of formula I-1 or formula II-1 within the above-mentioned range, which is more conducive to improving the oxidation resistance of the electrolyte and to the dissociation of the electrolyte, providing a good solvation structure for the electrolyte salt, thereby further improving the cycle performance of the electrochemical device under high voltage and high temperature.

[0015] In some embodiments of this application, the compound of formula III includes at least one of the following compounds:

[0016] The electrolyte includes compounds of formula III within the above-mentioned range, which is more conducive to the formation of a stable interfacial film on the negative electrode surface. The first and second components within the scope of this application work synergistically to further improve the cycle performance of the electrochemical device under high voltage and high temperature.

[0017] In some embodiments of this application, the compound of formula I-2 includes at least one selected from methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, or propyl propionate; the compound of formula II-2 includes at least one selected from dimethyl carbonate, diethyl carbonate, or methyl ethyl carbonate. Introducing a third component within the aforementioned range into the electrolyte, which includes the first and second components, helps reduce costs while maintaining good cycle performance and thermal safety of the electrochemical device.

[0018] In some embodiments of this application, the electrolyte includes a first lithium salt and a second lithium salt. The first lithium salt includes at least one of lithium hexafluorophosphate or lithium bis(fluorosulfonyl)imide, and the second lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, lithium difluorooxalate borate, lithium dioxalate borate, or lithium difluorophosphate. Based on the mass of the electrolyte, the mass percentage of the second lithium salt is D%, 0.1 ≤ D ≤ 5. The electrolyte including the first and second lithium salts within the scope of this application, and controlling the mass percentage of the second lithium salt within the scope of this application, is beneficial for forming a low-resistance and stable interface film on the positive and negative electrode surfaces, which helps to reduce the impedance of the interface film and further improve the cycle performance of the electrochemical device under high voltage and high temperature.

[0019] In some embodiments of this application, the thickness of the first material layer is H μm, where 0.1 ≤ H ≤ 10. By adjusting the thickness of the first material layer within the range of this application, it is beneficial to reduce the direct contact between the electrolyte, the positive electrode active material, and the positive electrode current collector, thereby reducing heat generation and further improving thermal safety performance.

[0020] In some embodiments of this application, the adhesion force between the first material layer and the positive electrode current collector is greater than or equal to 201 N / m. This indicates a strong adhesion between the first material layer and the positive electrode current collector, which helps reduce the shedding of the first material layer, thereby further improving the thermal safety and electrochemical performance of the electrochemical device.

[0021] In some embodiments of this application, the inorganic particles include at least one of alumina, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, gibbsite, barium sulfate, calcium sulfate, or calcium silicate; the first binder includes a copolymer formed by polymerizing acrylate, acrylamide, and acrylonitrile; and the first conductive agent includes at least one of graphene, carbon nanotubes, graphite fibers, or conductive carbon. The first material layer, comprising the inorganic particles, first binder, and first conductive agent within the aforementioned range, is beneficial for further reducing direct contact between the electrolyte, the positive electrode active material, and the positive electrode current collector, reducing heat generation, and further improving thermal safety performance.

[0022] The second aspect of this application provides an electronic device. The electrochemical device provided in the first aspect of this application exhibits good cycle performance under high voltage and high temperature conditions while also possessing good thermal safety performance; therefore, the electronic device provided in the second aspect of this application has excellent usability.

[0023] The beneficial effects of this application are:

[0024] This application provides an electrochemical device and an electronic device, comprising a positive electrode and an electrolyte. The positive electrode includes a positive current collector, a first material layer, and a positive material layer. The first material layer includes inorganic particles, a first binder, and a first conductive agent. The first material layer is disposed on at least one surface of the positive current collector, and the positive material layer is disposed between the positive current collector and the first material layer. The length ratio of the first material layer to the length of the positive current collector is X%, and 50 ≤ X ≤ 98. The electrolyte includes a first component and a second component. The first component includes at least one compound of formula I-1 or formula II-1, and the second component includes a compound of formula III. Based on the mass of the electrolyte, the mass percentage of the first component is A%, and the mass percentage of the second component is B%, and 40 ≤ A + B ≤ 90. This configuration improves the cycling performance of the electrochemical device under high voltage and high temperature while also ensuring thermal safety. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this application clearer, the following embodiments are provided to further illustrate this application in detail. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0026] It should be noted that, in the specific embodiments of this application, a lithium-ion battery is used as an example of an electrochemical device to explain this application; however, the electrochemical device of this application is not limited to lithium-ion batteries. The specific technical solution is as follows:

[0027] The first aspect of this application provides an electrochemical device comprising a positive electrode and an electrolyte. The positive electrode includes a positive current collector, a first material layer, and a positive material layer. The first material layer includes inorganic particles, a first binder, and a first conductive agent. The first material layer is disposed on at least one surface of the positive current collector, and the positive material layer is disposed between the positive current collector and the first material layer. The ratio of the length of the first material layer to the length of the positive current collector is X%, 50 ≤ X ≤ 98, preferably 80 ≤ X ≤ 98. For example, the value of X can be 50, 52, 55, 58, 60, 62, 65, 68, 70, 72, 75, 78, 80, 82, 85, 88, 90, 92, 95, 98, or a range of any two of these values.

[0028] The electrolyte comprises a first component and a second component, wherein the first component comprises at least one of a compound of formula I-1 or a compound of formula II-1:

[0029] Among them, R 11 and R 12Each is independently either substituted or unsubstituted C1-C 10 Alkyl, wherein R 11 and R 12 At least one of them has been replaced; R 21 and R 22 Each is independently either substituted or unsubstituted C1-C 10 Alkyl, wherein R 21 and R 22 At least one of them is substituted; when substituted, each substituent is independently a fluorine atom.

[0030] The second component includes compounds of formula III:

[0031] Among them, R 41 R 42 R 43 R 44 Each is independently H, F, substituted or unsubstituted C1-C3 alkyl group, and when substituted, the substituent is a fluorine atom, R. 41 R 42 R 43 R 44 At least one of the components contains F. Based on the mass of the electrolyte, the mass percentage of the first component is A%, and the mass percentage of the second component is B%, satisfying: 40 ≤ A + B ≤ 90. For example, the value of A + B can be 40, 42, 45, 48, 50, 52, 55, 58, 60, 62, 65, 68, 70, 72, 75, 78, 80, 82, 85, 88, 90, or a range of any two of these values.

[0032] The inventors discovered that the electrolyte simultaneously comprises a first component and a second component, and by controlling the mass percentage of the first and second components within the scope of this application, on the one hand, since the first and second components within the scope of this application have high oxidation potentials, they are beneficial to enhancing the oxidation resistance of the electrolyte, reducing side reactions of the electrolyte under high voltage and high temperature conditions, and reducing gas production; on the other hand, the first and second components play a dominant role in the solvation structure of lithium ions, which is beneficial to the dissociation of electrolyte in the electrolyte, promoting the dissolution of electrolyte and its existence in the electrolyte in the form of active metal ions (such as lithium ions); in addition, the first component is beneficial to the formation of a stable interfacial film at the positive electrode interface, and the second component is beneficial to the formation of a stable interfacial film at the negative electrode. The two work synergistically to improve the cycle performance of the electrochemical device under high voltage and high temperature conditions. When the value of A+B is too small, for example, less than 40, the electrolyte has weak oxidation resistance, and the first and second components cannot play a dominant role in the solvation structure of lithium ions, thus failing to effectively improve the cycle performance of the electrochemical device under high voltage and high temperature conditions. When the value of A+B is too large, for example, greater than 90, the electrolyte viscosity is high and the electrolyte content is low, failing to provide sufficient lithium ions, increasing polarization, and affecting the electrochemical performance of the electrochemical device. Although the electrolyte includes the first component within the scope of this application, which is beneficial to improving the cycle performance of the electrochemical device under high voltage and high temperature, the first component within the scope of this application comes into contact with the positive electrode active material and the positive electrode current collector, generating heat under high temperature conditions, affecting the thermal safety performance of the electrochemical device, especially the heat box performance. Therefore, based on the electrolyte including the first and second components of this application, by setting a first material layer on the surface of the positive electrode current collector and adjusting the ratio X% of the length of the first material layer to the length of the positive electrode current collector within the scope of this application, it is beneficial to reduce the direct contact between the electrolyte, the positive electrode active material, and the positive electrode current collector, reduce heat generation, and improve thermal safety performance. This application, by setting a first material layer and using it in conjunction with the first and second components in the electrolyte, improves the cycle performance of the electrochemical device under high voltage and high temperature while also ensuring the thermal safety performance of the electrochemical device. In this application, high voltage refers to a voltage greater than or equal to 4.2V, and high temperature refers to a temperature greater than or equal to 40℃.

[0033] This application does not impose any particular limitation on the coating area of ​​the first material layer on the surface of the positive electrode current collector, as long as the purpose of this application can be achieved. In some embodiments of this application, the first material layer is disposed at one end of the positive electrode current collector, and no first material layer is disposed at the other end. In other embodiments of this application, the first material layer is disposed in the middle region of the positive electrode current collector, and no first material layer is disposed at either end of the positive electrode current collector. Preferably, the first material layer is disposed at one end of the positive electrode current collector, and no first material layer is disposed at the other end, and the end of the positive electrode sheet with the first material layer is close to the center of the wound electrode assembly.

[0034] In some embodiments of this application, 5 ≤ B ≤ 15. For example, the value of B can be 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or a range of any two of these values. Including the first and second components within the scope of this application in the electrolyte, and controlling the mass percentage of the second component within the scope of this application, is beneficial for forming a stable solid electrolyte interphase (SEI) film on the negative electrode surface. The synergistic effect of the first and second components further improves the cycle performance of the electrochemical device under high voltage and high temperature.

[0035] In some embodiments of this application, 4.3 ≤ A / B ≤ 19. For example, the value of A / B can be 4.3, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or a range of any two of these values. The electrolyte includes a first component and a second component. The first component is beneficial for forming a stable interfacial film at the positive electrode, and the second component is beneficial for forming a stable interfacial film at the negative electrode. Controlling the A / B ratio within the range of this application can further improve the stability of the positive and negative electrode interfaces and reduce the impedance of the positive and negative electrode interfaces, thereby further improving the cycle performance of the electrochemical device under high voltage and high temperature.

[0036] In some embodiments of this application, the electrolyte includes a third component, which includes at least one of a compound of formula I-2 or a compound of formula II-2:

[0037] Among them, R 13 R 14 R 23 and R 24 Each independently is C1-C 10 Alkyl group; the mass percentage of the third component is C%, based on the mass of the electrolyte, with 0 < C ≤ 50. For example, the value of C can be 0.5, 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, or a range of any two of these values. Introducing a third component into the electrolyte, which includes the first and second components, and controlling the mass percentage of the third component within the range specified in this application, helps reduce costs while maintaining good cycle performance and thermal safety of the electrochemical device.

[0038] In some embodiments of this application, the compound of formula I-1 includes at least one of the following compounds:

[0039] Compounds of formula II-1 include at least one of the following compounds:

[0040] The electrolyte includes at least one of the compounds of formula I-1 or formula II-1 within the above-mentioned range, which is more conducive to improving the oxidation resistance of the electrolyte and to the dissociation of the electrolyte, providing a good solvation structure for the electrolyte salt, thereby further improving the cycle performance of the electrochemical device under high voltage and high temperature.

[0041] In some embodiments of this application, the compound of formula III includes at least one of the following compounds:

[0042] The electrolyte includes compounds of formula III within the above-mentioned range, which is more conducive to the formation of a stable interfacial film on the negative electrode surface. The first and second components within the scope of this application work synergistically to further improve the cycle performance of the electrochemical device under high voltage and high temperature.

[0043] In some embodiments of this application, the compound of formula I-2 includes at least one selected from methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, or propyl propionate; the compound of formula II-2 includes at least one selected from dimethyl carbonate, diethyl carbonate, or methyl ethyl carbonate. Introducing a third component within the aforementioned range into the electrolyte, which includes the first and second components, helps reduce costs while maintaining good cycle performance and thermal safety of the electrochemical device.

[0044] In some embodiments of this application, the electrolyte includes a first lithium salt and a second lithium salt. The first lithium salt includes at least one of lithium hexafluorophosphate or lithium bis(fluorosulfonyl)imide, and the second lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, lithium difluorooxalate borate, lithium dioxalate borate, or lithium difluorophosphate. Based on the mass of the electrolyte, the mass percentage of the second lithium salt is D%, 0.1 ≤ D ≤ 5, preferably 0.5 ≤ D ≤ 1.5. For example, the mass percentage D of the second lithium salt can be 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, or a range of any two of these values. This application does not impose any particular limitation on the mass percentage of the first lithium salt, as long as the purpose of this application is achieved. For example, based on the mass of the electrolyte, the mass percentage of the first lithium salt is 8% to 15%. The electrolyte includes a second lithium salt within the scope of this application, and the mass percentage of the second lithium salt is controlled within the scope of this application. This is beneficial for forming a low-impedance and stable interface film on the positive and negative electrode surfaces, which helps to reduce the impedance of the interface film and further improve the cycle performance of the electrochemical device under high voltage and high temperature.

[0045] In some embodiments of this application, the thickness of the first material layer is H μm, where 0.1 ≤ H ≤ 10. For example, the value of H can be 0.1, 0.2, 0.5, 0.8, 1, 1.2, 1.5, 1.8, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, or a range of any two of these values. By adjusting the thickness of the first material layer within the range specified in this application, it is beneficial to reduce the direct contact between the electrolyte, the positive electrode active material, and the positive electrode current collector, thereby reducing heat generation and further improving thermal safety performance.

[0046] In some embodiments of this application, the adhesion force between the first material layer and the positive electrode current collector is greater than or equal to 201 N / m. Within the range of adhesion forces achievable in the art, a higher adhesion force is better; for example, it can be 201 N / m, 250 N / m, 300 N / m, 500 N / m, or a range consisting of any two of these. An adhesion force between the first material layer and the positive electrode current collector greater than or equal to 201 N / m indicates a strong bond between them, which helps reduce the shedding of the first material layer and thus further improves the thermal safety and electrochemical performance of the electrochemical device.

[0047] Generally, the adhesion between the first material layer and the positive electrode current collector can be changed by altering the mass percentage of the first adhesive in the first material layer. With other conditions remaining constant, increasing the mass percentage of the first adhesive in the first material layer increases the adhesion between the first material layer and the positive electrode current collector, while decreasing the mass percentage of the first adhesive in the first material layer decreases the adhesion between the first material layer and the positive electrode current collector.

[0048] In some embodiments of this application, the inorganic particles include at least one of alumina, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, gibbsite, barium sulfate, calcium sulfate, or calcium silicate; the first binder includes a copolymer formed by polymerizing acrylate, acrylamide, and acrylonitrile, wherein the acrylate may include, but is not limited to, at least one of lithium acrylate, sodium acrylate, or potassium acrylate; the first conductive agent includes at least one of graphene, carbon nanotubes, graphite fibers, or conductive carbon. The first material layer, comprising the inorganic particles, first binder, and first conductive agent within the above-mentioned range, is beneficial for further reducing direct contact between the electrolyte, positive electrode active material, and positive electrode current collector, reducing heat generation, and further improving thermal safety performance. This application does not impose any particular limitation on the mass percentage of the inorganic particles, first binder, and first conductive agent in the first material layer, as long as the purpose of this application is achieved.

[0049] This application does not impose any particular limitation on the preparation method of the first binder. Preparation methods known to those skilled in the art can be used. For example, the preparation method of the first binder is as follows: Distilled water is added to a reaction vessel, the stirrer is started, nitrogen gas is introduced to remove oxygen, then acrylate, acrylamide, and acrylonitrile are added. The mixture is heated to 60°C to 70°C under an inert atmosphere and kept at a constant temperature. Then, an initiator is added to initiate the reaction. After reacting for 18 to 22 hours, an alkaline solution is added to the reaction vessel to adjust the pH of the solution to 6.5 to 9. The reactants are then filtered, washed, dried, pulverized, and sieved to obtain the first binder. This application does not impose any particular limitation on the type of initiator, as long as it achieves the purpose of this application. For example, it can be a 20% ammonium sulfate solution. This application does not impose any particular limitation on the amount of distilled water and initiator, as long as it enables the polymerization reaction of acrylate, acrylamide, and acrylonitrile.

[0050] In some embodiments of this application, the first material layer may further include a leveling agent. This application does not impose any particular limitation on the type of leveling agent, as long as it achieves the purpose of this application. Leveling agents include, but are not limited to, at least one of polyethoxypropoxypropylene, polysiloxane, polymethyl methacrylate, polyethylene glycol, sodium polycarboxylate, or polyacryl alcohol. This application does not impose any particular limitation on the mass percentage of the leveling agent in the first material layer, as long as it achieves the purpose of this application.

[0051] This application does not impose any particular restrictions on the positive electrode current collector, as long as it can achieve the purpose of this application. For example, it may include aluminum foil, aluminum alloy foil, or composite current collector (such as aluminum-carbon composite current collector).

[0052] In this application, the positive electrode material layer includes a positive electrode active material. This application does not particularly limit the type of positive electrode active material, as long as it can achieve the purpose of this application. The positive electrode active material includes compounds that reversibly insert and extract lithium ions. In some embodiments, the positive electrode material layer includes a positive electrode active material with an operating potential of 4.5V or higher relative to metallic lithium. That is, the positive electrode active material of this application can operate under high voltage. In some embodiments, the positive electrode active material may include at least one of lithium nickel cobalt manganese oxide (NCM), lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide, lithium manganese oxide, or lithium manganese iron phosphate. Lithium nickel cobalt manganese oxide may include, but is not limited to, LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 1 / 3 Co1 / 3 Mn 1 / 3 O2 (NCM333) or LiNi 0.9 Co 0.05 Mn 0.05 At least one of O2 (NCM955).

[0053] The positive electrode material layer may also include a conductive agent and a binder. This application does not impose any particular limitation on the types of conductive agents and binders, as long as they achieve the purpose of this application. For example, the conductive agent may include, but is not limited to, at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon fibers, flake graphite, graphene, metallic materials, or conductive polymers. The aforementioned carbon nanotubes may include, but are not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The aforementioned carbon fibers may include, but are not limited to, vapor-grown carbon fibers (VGCF) and / or carbon nanofibers. The aforementioned metallic materials may include, but are not limited to, metal powders and / or metal fibers; specifically, the metal may include, but is not limited to, at least one of copper, nickel, aluminum, or silver. The aforementioned conductive polymer may include, but is not limited to, at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene, or polypyrrole. The binder may include, but is not limited to, at least one of polyacrylic acid, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyvinyl alcohol, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyimide, polyamide-imide, styrene-butadiene rubber, or polyvinylidene fluoride. This application does not impose any particular restrictions on the mass ratio of positive electrode active material, conductive agent, and binder in the positive electrode material layer. Those skilled in the art can choose according to actual needs, as long as the purpose of this application can be achieved.

[0054] This application does not impose any particular limitations on the thickness of the positive electrode current collector and the positive electrode material layer, as long as the purpose of this application can be achieved. For example, the thickness of the positive electrode current collector can be 5 μm to 20 μm, and the thickness of the single-sided positive electrode material layer can be 30 μm to 120 μm.

[0055] In this application, the positive electrode material layer can be disposed on one surface or on two surfaces along the thickness direction of the positive electrode current collector. It should be noted that "surface" here can refer to the entire surface of the positive electrode current collector or only a portion thereof; this application has no particular limitation, as long as the purpose of this application is achieved. The first material layer is coated between the positive electrode material layer and the positive electrode current collector. It can be understood that in areas of the positive electrode current collector not coated with the first material layer, the positive electrode material layer is in direct contact with the positive electrode current collector.

[0056] In this application, there are no particular limitations on the preparation method of the positive electrode sheet, as long as the purpose of this application can be achieved. For example, it can be prepared by the following method: Inorganic particles, a first binder, and a first conductive agent are mixed, deionized water is added, and the mixture is stirred evenly to obtain a first material layer slurry with a solid content of 10% to 50%. The first material layer slurry is coated on the surface area of ​​the positive electrode current collector, and after drying, a positive electrode current collector with a single-sided coating of the first material layer is obtained. Then, the above coating steps are repeated on the other surface of the positive electrode current collector, and after drying, a positive electrode current collector with a double-sided coating of the first material layer is obtained. Then, the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder are mixed, and N-methylpyrrolidone (NMP) is added and stirred evenly to obtain a positive electrode slurry with a solid content of 65wt% to 85wt%. The positive electrode slurry is uniformly coated on one surface of the positive electrode current collector coated with the first material layer, and after drying, a positive electrode sheet with a single-sided coating of the positive electrode material layer is obtained. Then, repeat the above coating steps on the other surface of the positive current collector coated with the first material layer. After drying, a positive electrode sheet with a double-sided coated positive material layer is obtained. After coating, the positive electrode sheet is obtained by cold pressing and cutting.

[0057] In this application, the electrochemical device further includes a negative electrode sheet, which comprises a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. The phrase "the negative electrode material layer is disposed on at least one surface of the negative electrode current collector" means that the negative electrode material layer can be disposed on one surface of the negative electrode current collector along its thickness direction, or on two surfaces of the negative electrode current collector along its thickness direction. It should be noted that the term "surface" here can refer to the entire surface area of ​​the negative electrode current collector, or only a portion thereof; this application does not impose any particular limitation, as long as the purpose of this application is achieved.

[0058] This application does not impose any particular restrictions on the negative electrode current collector, as long as it can achieve the purpose of this application. For example, it may include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or composite current collector. For example, the composite current collector may be lithium copper composite current collector, carbon copper composite current collector, nickel copper composite current collector, titanium copper composite current collector, etc.

[0059] The negative electrode material layer includes a negative electrode active material. This application does not impose any particular limitation on the negative electrode active material, as long as it can achieve the purpose of this application. For example, the negative electrode active material may include, but is not limited to, natural graphite, artificial graphite, mesophase micro carbon spheres, hard carbon, soft carbon, silicon, silicon-carbon composites, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO2, and spinel-structured lithiated TiO2-Li4Ti5O. 12 Or at least one of Li-Al alloys.

[0060] The negative electrode active material layer of this application may further include a conductive agent and a binder. This application does not impose any particular limitations on the conductive agent and binder, as long as they achieve the purpose of this application. For example, the binder and conductive agent may include, but are not limited to, at least one of the substances selected for the positive electrode material layer described above. This application does not impose any particular limitations on the mass ratio of the negative electrode active material, conductive agent, and binder in the negative electrode material layer; those skilled in the art can select them according to actual needs, as long as the purpose of this application is achieved.

[0061] In this application, there are no particular limitations on the thickness of the negative electrode current collector and the negative electrode active material layer, as long as the purpose of this application can be achieved. For example, the thickness of the negative electrode current collector is 4 μm to 12 μm, and the thickness of the single-sided negative electrode active material layer is 30 μm to 130 μm.

[0062] In this application, there are no particular limitations on the preparation method of the negative electrode sheet, as long as it achieves the purpose of this application. For example, it can be prepared by the following method: mixing negative electrode active material, negative electrode binder, and negative electrode dispersant, adding deionized water and stirring evenly to obtain a negative electrode slurry with a solid content of 55wt% to 70wt%. The negative electrode slurry is uniformly coated on one surface of the negative electrode current collector, and after drying, a negative electrode sheet with a single-sided negative electrode material layer is obtained. Then, the above coating steps are repeated on the other surface of the negative electrode current collector, and after drying, a negative electrode sheet with a double-sided negative electrode material layer is obtained. After coating, the negative electrode sheet is obtained by cold pressing and cutting.

[0063] The electrochemical device of this application also includes a diaphragm to separate the positive and negative electrode plates, prevent internal short circuits, allow electrolyte ions to pass freely, and not affect the electrochemical charging and discharging process. In this application, the electrochemical device also includes a diaphragm. This application does not impose any particular limitation on the diaphragm, as long as it achieves the purpose of this application. For example, the diaphragm material may include, but is not limited to, at least one of polyethylene (PE), polyolefins (PO) primarily composed of polypropylene (PP), polyester (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex, or aramid. The type of diaphragm may include at least one of woven membrane, nonwoven membrane, microporous membrane, composite membrane, rolled membrane, or spun membrane.

[0064] In some embodiments of this application, the diaphragm may include a substrate layer and a surface treatment layer. The substrate layer may be a nonwoven fabric, membrane, or composite membrane with a porous structure, and the material of the substrate layer may include at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. Optionally, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane may be used.

[0065] Optionally, a surface treatment layer is provided on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing polymers and inorganic substances.

[0066] In some embodiments of this application, the inorganic layer comprises inorganic particles and a binder. This application does not particularly limit the inorganic particles; for example, the inorganic particles may include at least one selected from alumina, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. This application does not particularly limit the binder; for example, the binder may be at least one of the binders described above. In some embodiments of this application, the polymer layer comprises a polymer, the polymer material of which includes at least one selected from polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, or polyvinylidene fluoride or poly(vinylidene fluoride-hexafluoropropylene).

[0067] In this application, there is no particular limitation on the thickness of the diaphragm, as long as it can achieve the purpose of this application. For example, the thickness of the diaphragm can be from 3 μm to 30 μm.

[0068] The electrochemical device of this application also includes a housing for accommodating the positive electrode, the separator, the negative electrode, and the electrolyte, as well as other components known in the field of electrochemical devices. This application does not limit the scope of these other components. This application does not impose any particular limitation on the housing; it can be a housing known in the art, as long as it achieves the purpose of this application. For example, the housing can be a rigid housing or a flexible housing. The material of the rigid housing can be metal; this application does not limit the type of metal and can use known metal rigid housings, as long as they achieve the purpose of this application. The flexible housing can be a metal-plastic film, such as aluminum-plastic film, steel-plastic film, etc.

[0069] The electrochemical device described in this application is not particularly limited and may include any device in which an electrochemical reaction occurs. In one embodiment of this application, the electrochemical device may include, but is not limited to, lithium-ion batteries, sodium-ion batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries.

[0070] The preparation process of the electrochemical device described in this application is well known to those skilled in the art, and this application does not impose any particular limitations. For example, it may include, but is not limited to, the following steps: stacking the positive electrode, separator, and negative electrode in sequence, and performing operations such as winding and folding as needed to obtain a wound electrode assembly; placing the electrode assembly into a housing; injecting electrolyte into the housing and sealing it to obtain the electrochemical device. Alternatively, stacking the positive electrode, separator, and negative electrode in sequence, and then fixing the four corners of the entire stacked structure with tape to obtain a stacked electrode assembly; placing the electrode assembly into a housing; injecting electrolyte into the housing and sealing it to obtain the electrochemical device. In addition, overcurrent protection elements, conductive plates, etc., may be placed in the housing as needed to prevent pressure rise and overcharging / discharging inside the electrochemical device.

[0071] The second aspect of this application provides an electronic device that includes the electrochemical device provided in the first aspect of this application. The electrochemical device provided in the first aspect of this application exhibits good cycle performance under high voltage and high temperature conditions, while also possessing good thermal performance; therefore, the electronic device provided in the second aspect of this application has excellent usability.

[0072] The electronic device described in this application is not particularly limited and can be any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0073] Example

[0074] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0075] Test methods and equipment:

[0076] Testing of the ratio X of the length of the first material layer to the length of the positive electrode current collector.

[0077] Under an environment of (25±3)℃, the lithium-ion battery was disassembled to obtain the positive electrode sheet. The residual electrolyte on the surface of the positive electrode sheet was wiped off with lint-free paper. The positive electrode material layer was wiped along the length of the electrode strip with anhydrous ethanol to expose the first material layer. The length of the first material layer and the current collector length were measured, and their ratio X was calculated.

[0078] Testing the thickness H of the first material layer

[0079] The lithium-ion secondary battery was disassembled at (25±3)℃. The positive electrode sheet was soaked in DMC and then baked in an oven at 80℃ for 30 minutes. Three samples (width: 20mm, length: 20mm) were taken from the positive electrode sheet at 10mm intervals. The cross-section of the positive electrode sheet was treated by ion polishing. The cross-section was sputtered with gold. The cross-section was photographed with SEM and the thickness of the single-layer coating (excluding aluminum foil) at different positions was measured using the software's built-in measurement tool. Three positions were taken as cross-sections for each sample, and three measurement points were taken for each cross-section. The average value was calculated to obtain the thickness H of the bottom coating.

[0080] Test of the adhesion between the first material layer and the positive electrode current collector

[0081] 1) Sampling: Disassemble the lithium-ion battery at (25±3)℃ to obtain the positive electrode plate, and wipe away the residual electrolyte on the surface of the positive electrode plate with lint-free paper;

[0082] 2) Sample preparation: Take the positive electrode sheet to be tested, and cut a sample of the positive electrode sheet coated with the first material layer with a width x (20mm) and a length y (190mm) using a blade. The size can be selected according to the actual size of the electrode sheet removed.

[0083] 3) Apply double-sided tape to a steel plate with a width of 30mm and a length of 200mm. The width of the double-sided tape is 20mm and the length is y (190mm).

[0084] 4) Attach the positive electrode material layer of the positive electrode sample cut in step 2 to double-sided tape, with the test side facing down. Fix the steel plate and the positive electrode sample with a clamp and peel off the positive electrode material layer with a high-speed rail AI-3000 tensile tester.

[0085] 5) Attach the first material layer of the electrode sample with the positive electrode material layer peeled off to the double-sided tape. Fix the steel plate and the electrode sample with the positive electrode material layer peeled off with a clamp. Test its adhesion with a high-speed rail AI-3000 tensile testing machine. The tensile speed is 50 mm / min. The tensile displacement can be determined according to the sample length. Calculate the adhesion force between the functional layer and the positive electrode current collector F2 = f1 / x (electrode width) based on the tensile force value f1 (N) when the curve is flat. Unit: N / m.

[0086] Cyclic performance test

[0087] At 45℃ and ambient pressure (0.1MPa), the lithium-ion battery was charged at a constant current of 0.5C to a voltage of 4.55V, then charged at a constant voltage of 4.55V to a current of 0.02C, and then allowed to stand for 5 minutes. Next, it was discharged at a constant current of 1C to a voltage of 3.0V, and allowed to stand for 5 minutes. This constitutes one charge-discharge cycle, and the discharge capacity of the first cycle was recorded. The lithium-ion battery was subjected to N charge-discharge cycle tests using the above method, and the discharge capacity of the Nth cycle was measured. The capacity retention rate (%) after N cycles of the lithium-ion battery = discharge capacity of the Nth cycle / discharge capacity of the first cycle × 100%. The number of cycles when the capacity retention rate of the lithium-ion battery reached 80% was recorded. A higher number of cycles indicates better cycle performance of the lithium-ion battery under high voltage and high temperature.

[0088] Hot box test

[0089] At 25℃, the lithium-ion battery is charged at a constant current of 0.5C to a voltage of 4.55V, and then charged at a constant voltage of 4.55V to a current of 0.02C. This fully charged lithium-ion battery is then placed in a test chamber according to the test methods specified in GB 31241-2022 "Safety Technical Specifications for Lithium-ion Batteries and Battery Packs for Portable Electronic Products". The test chamber is heated at a rate of 5℃ / min ± 2℃ / min. Once the temperature inside the chamber reaches the predetermined temperature (e.g., 130℃ ± 2℃), it is held at this temperature for 30 minutes, observing whether the battery ignites or explodes. A battery that does not ignite or explode is considered to have passed; otherwise, it is considered to have failed. The higher the maximum pass temperature value in the hot chamber test, the better the thermal performance of the lithium-ion battery, i.e., the better its thermal safety performance.

[0090] Example 1-1

[0091] <Preparation of the First Adhesive>

[0092] Distilled water was added to the reactor and stirring was started. After purging with nitrogen for 2 hours to remove oxygen, the following monomers—acrylonitrile, lithium acrylate, and acrylamide—were added to the reactor at a mass ratio of 45:45:10. The reactor was heated to 65°C under an inert atmosphere and maintained at a constant temperature. Then, a 20% ammonium persulfate solution was added as an initiator to start the reaction. After 22 hours of reaction, the precipitate was removed, and the pH was neutralized to 6.5 with alkali solution. The mass ratio of distilled water, monomers, and initiator was 89.5:10:0.5. After the reaction, the reaction product was filtered, washed, dried, pulverized, and sieved to obtain the first binder.

[0093] <Preparation of the positive electrode>

[0094] Preparation of the first material layer: Inorganic alumina particles, the first binder prepared above, and the first conductive agent, conductive carbon (Super P), were mixed at a mass ratio of 92:1.5:6.5. NMP was added to prepare a first material layer slurry with a solid content of 40%. The first material layer slurry was uniformly coated onto one surface of a 3μm thick positive electrode current collector aluminum foil using a gravure coating method. The length of the first material layer was 50% of the length of the positive electrode current collector aluminum foil, meaning that 50% of the aluminum foil at the other end was not coated with the first material layer. The mixture was dried at 80°C to obtain a single-sided coating weight of 5mg / 1540.25mm. 2 Then, repeat the above steps on the other surface of the aluminum foil to obtain an aluminum foil with the first material layer coated on both sides. It should be noted that the areas on both surfaces of the aluminum foil coated with the first material layer are at the same end.

[0095] Preparation of the positive electrode material layer: Lithium cobalt oxide (LiCoO2), the positive electrode conductive agent Super P, and the positive electrode binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 97.3:1.1:1.6. N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 75%, and the mixture was stirred evenly. The positive electrode material layer slurry was applied along one end of the aluminum foil coated with the first material layer, with the length of the positive electrode material layer to the length of the aluminum foil being 98%, meaning the positive electrode material layer was coated on the surface of the first material layer. The coating was then dried at 110°C to obtain a positive electrode sheet with a single-sided positive electrode material layer. The above steps were then repeated on the other surface of the positive electrode sheet to obtain a positive electrode sheet with a double-sided positive electrode active material coating. After cold pressing and slitting, positive electrode sheets with a specification of 1400mm×70mm are obtained for use (the coating size of the first material layer on the surface of the positive electrode sheet is 700mm×68mm, and the coating size of the positive electrode material layer on the surface of the positive electrode sheet is 1372mm×68mm). Among them, the thickness of the first material layer on one side is 3μm, the thickness of the positive electrode material layer on one side with the first material layer is 27μm, and the thickness of the positive electrode material layer on one side without the first material layer is 30μm.

[0096] <Preparation of Negative Electrode Sheets>

[0097] Artificial graphite, styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) were mixed at a mass ratio of 97:1.5:1.5. Deionized water was then added as a solvent to prepare a slurry with a solid content of 45 wt%, which was stirred thoroughly. The slurry was uniformly coated onto one surface of a 5 μm thick copper foil, dried at 110°C, and cold-pressed to obtain a single-sided coated negative electrode sheet with a 50 μm thick negative electrode material layer. The above steps were repeated on the other surface of the copper foil to obtain a double-sided coated negative electrode sheet. The negative electrode sheet was cut to a size of 1400 mm × 70 mm and tabs were welded on for later use.

[0098] <Preparation of Electrolyte>

[0099] In an argon-filled glove box (moisture <10ppm, oxygen <1ppm), the first component (Formula I-3A), the second component (Formula III-1), and the third component (diethyl carbonate) were mixed uniformly at a mass ratio of 72:8:5.5. Then, lithium hexafluorophosphate (LiPF6), adiponitrile (ADN), and 1,3,6-hexanetrionitrile (HTCN) were added to the solvent and mixed uniformly to obtain the electrolyte. Based on the mass of the electrolyte, the mass percentage of LiPF6 was 12.5%, the mass percentage of adiponitrile was 1%, the mass percentage of 1,3,6-hexanetrionitrile was 1%, the mass percentage of the first component (Formula I-3A) was 72%, the mass percentage of the second component (Formula III-1) was 8%, and the mass percentage of diethyl carbonate was 5.5%, i.e., the value of A+B was 80%.

[0100] <Septum>

[0101] A 5μm thick porous polyethylene (PE) membrane (manufacturer: Celgard Membrane Inc., USA) was used as the separator.

[0102] <Preparation of Lithium-ion Batteries>

[0103] The prepared positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator positioned between the positive and negative electrode sheets to provide isolation. Simultaneously, one end of the positive electrode sheet coated with the first material layer is ensured to be close to the center of the pre-wound electrode assembly. The assembly is then wound into an electrode assembly, placed in an aluminum-plastic film packaging bag, and dried in an 85°C vacuum oven for 12 hours to remove moisture. Electrolyte is then injected, and the battery undergoes vacuum sealing, settling, formation, degassing, edge trimming, and shaping processes to obtain a lithium-ion secondary battery. The upper limit of the formation voltage is 4.5V, the formation temperature is 85°C, and the settling time is 2 hours.

[0104] Examples 1-2 to Examples 1-5

[0105] Except for adjusting the ratio of the length of the first material layer to the length of the positive electrode current collector according to Table 1 in the <Preparation of Positive Electrode Sheet>, the rest is the same as in Example 1-1.

[0106] Examples 1-6 to Examples 1-8

[0107] Except for the adjustment of the mass percentages of the first and second components according to Table 1 in the <Preparation of Electrolyte>, the mass percentages of the first and second components in Examples 1-6 and 1-7 are reduced, the mass percentage of diethyl carbonate is increased accordingly, and the mass percentages of LiPF6, adiponitrile, and 1,3,6-hexanetrionitrile remain unchanged, and the rest are the same as in Examples 1-5; the electrolyte in Examples 1-8 does not include diethyl carbonate, the mass percentage of LiPF6 is 8%, the mass percentage of adiponitrile is 1%, the mass percentage of 1,3,6-hexanetrionitrile is 1%, and the rest are the same as in Examples 1-5.

[0108] Examples 1-9 to Examples 1-15

[0109] Except for adjusting the type and mass percentage of the first or second component according to Table 1 in the <Preparation of Electrolyte>, the rest is the same as in Examples 1-5.

[0110] Examples 1-16 to Examples 1-20

[0111] Except for adjusting the mass percentages of the first and second components according to Table 1 in the <Preparation of Electrolyte>, the rest is the same as in Examples 1-5.

[0112] Examples 2-1 to 2-4

[0113] Except for adjusting the mass percentage of the first component and the mass percentage and type of the third component according to Table 2 in the <Preparation of Electrolyte>, the rest is the same as in Examples 1-5.

[0114] Examples 2-5

[0115] Except for the following in <Preparation of Electrolyte>, where the mass percentages of the first and third components are adjusted according to Table 2, the electrolyte does not include diethyl carbonate, the mass percentage of LiPF6 is 8%, the mass percentage of adiponitrile is 1%, and the mass percentage of 1,3,6-hexanetrionitrile is 1%, the rest is the same as in Example 2-1.

[0116] Examples 2-6 to 2-12

[0117] Except for the addition of a second lithium salt to the electrolyte and adjustment of the type and mass percentage of the second lithium salt according to Table 2 in the <Preparation of Electrolyte>, where the mass percentage of diethyl carbonate in the electrolyte is changed accordingly, the rest is the same as in Examples 1-5.

[0118] Example 2-13

[0119] Except for the addition of a second lithium salt to the electrolyte according to Table 2 in the <Preparation of Electrolyte> section, where the mass percentage of diethyl carbonate in the electrolyte is changed accordingly, the rest is the same as in Example 2-1.

[0120] Examples 3-1 to 3-5

[0121] Except for adjusting the thickness of the first material layer according to Table 3 in the <Preparation of Positive Electrode>, the rest is the same as in Examples 1-5.

[0122] Examples 3-6 to 3-7

[0123] Except for the adjustment of the mass percentage of the first binder in the first material layer according to Table 3 in the <Preparation of the Positive Electrode>, and the change in the mass percentage of the inorganic particles, the rest is the same as in Examples 1-5.

[0124] Examples 3-8 to 3-10

[0125] Except for adjusting the types of inorganic particles, first binder, and first conductive agent in the first material layer according to Table 3 in the <Preparation of Positive Electrode Sheet> section, the rest is the same as in Examples 1-5. Among them, the <Preparation of First Binder> in Examples 3-9 is the same as the preparation method of the first binder in Examples 1-1, except for changing the mass ratio of each monomer added to the reactor.

[0126] Comparative Example 1

[0127] Except for the fact that in the <Preparation of Positive Electrode Sheet>, the first material layer was not coated on the positive current collector and the thickness of the single-sided positive electrode material layer was 30 μm, the rest was the same as in Example 1-1.

[0128] Comparative Example 2

[0129] Except for adjusting the mass percentage of the first component according to Table 1 in the <Preparation of Electrolyte> section, and excluding the second component in the electrolyte, the rest is the same as in Examples 1-5.

[0130] Comparative Example 3

[0131] Except for the <Preparation of Electrolyte>, where the mass percentages of the first and second components are adjusted according to Table 1, wherein the mass percentages of the first and second components are reduced, the mass percentage of diethyl carbonate is increased accordingly, and the mass percentage of LiPF6 remains unchanged, the rest are the same as in Examples 1-5.

[0132] Comparative Example 4

[0133] Except for the preparation of the electrolyte, in which the mass percentages of the first and second components are adjusted according to Table 1, and the electrolyte does not contain diethyl carbonate and the mass percentage of LiPF6 is 5%, the rest are the same as in Examples 1-5.

[0134] The relevant parameters and performance tests of each embodiment and comparative example are shown in Tables 1 to 3.

[0135] Table 1 Note: In Table 1, " / " indicates that the corresponding substance or parameter does not exist.

[0136] As can be seen from Examples 1-1 to 1-20 and Comparative Examples 1 to 4, the positive electrode sheet includes a first material layer, and the ratio X of the length of the first material layer to the length of the positive current collector is adjusted within the range of this application. The electrolyte includes a first component and a second component, and the value of A+B is adjusted within the range of this application. This allows the lithium-ion battery to have a higher number of cycles and a higher hot box test pass temperature, indicating that the lithium-ion battery has good cycle performance and good thermal safety performance under high voltage and high temperature conditions. Comparative Example 1 does not have a first material layer, and although its lithium-ion battery has a high number of cycles, its hot box test pass temperature is low, indicating that the thermal safety performance of the lithium-ion battery is poor. The electrolyte of Comparative Example 2 does not include a second component, and its lithium-ion battery has a lower number of cycles, indicating that the cycle performance of the lithium-ion battery under high voltage and high temperature conditions is poor. The values ​​of A+B in the electrolytes of Comparative Examples 3 and 4 are not within the range of this application, and their lithium-ion batteries have a lower number of cycles, indicating that the cycle performance of the lithium-ion batteries under high voltage and high temperature conditions is poor.

[0137] The type of the first component typically affects the cycle performance of lithium-ion batteries under high voltage and high temperature conditions. As can be seen from Examples 1-5, 1-9 to 1-13, when the first component within the scope of this application is selected, the lithium-ion battery exhibits a higher number of cycle cycles and a higher hot box test pass temperature, indicating that the lithium-ion battery has good cycle performance under high voltage and high temperature conditions, as well as good thermal safety performance.

[0138] The type of the second component typically affects the cycle performance of lithium-ion batteries under high voltage and high temperature conditions. As can be seen from Examples 1-5, 1-14, and 1-15, when the second component within the scope of this application is selected, the lithium-ion battery exhibits a higher number of cycle cycles and a higher hot box test pass temperature, indicating that the lithium-ion battery has good cycle performance under high voltage and high temperature conditions, as well as good thermal safety performance.

[0139] The mass percentage ratio A / B of the first and second components typically affects the cycle performance and thermal safety of lithium-ion batteries under high voltage and high temperature conditions. As can be seen from Examples 1-5, 1-16 to 1-20, by adjusting the value of A / B within the range of this application, the lithium-ion battery exhibits a higher number of cycle cycles and a higher thermal chamber test pass temperature, indicating that the lithium-ion battery possesses both good cycle performance and good thermal safety performance under high voltage and high temperature conditions.

[0140] Table 2 Note: In Table 2, " / " indicates that the corresponding substance or parameter does not exist.

[0141] The type and mass percentage of the third component typically affect the cycle performance and thermal safety performance of lithium-ion batteries under high voltage and high temperature conditions. As can be seen from Examples 1-5 and Examples 2-1 to 2-5, when the electrolyte includes the third component within the scope of this application, the lithium-ion battery exhibits a higher number of cycle cycles and a higher thermal chamber test pass temperature, indicating that the lithium-ion battery possesses both good cycle performance and good thermal safety performance under high voltage and high temperature conditions.

[0142] The type and mass percentage of the second lithium salt typically affect the cycle performance of lithium-ion batteries under high voltage and high temperature conditions. As can be seen from Examples 1-5, 2-6 to 2-12, and Examples 2-1 and 2-13, when the electrolyte includes the second lithium salt within the scope of this application and the mass percentage of the second lithium salt is controlled within this scope, the lithium-ion battery exhibits a higher number of cycle cycles and a higher hot box test pass temperature. This indicates that the lithium-ion battery possesses good cycle performance under high voltage and high temperature conditions, while also exhibiting good thermal safety performance.

[0143] Table 3

[0144] The thickness of the first material layer typically affects the cycle performance and thermal safety performance of lithium-ion batteries under high voltage and high temperature conditions. As can be seen from Examples 1-5 and Examples 3-1 to 3-5, by adjusting the thickness of the first material layer within the range of this application, the lithium-ion battery exhibits a higher number of cycle cycles and a higher thermal chamber test pass temperature, indicating that the lithium-ion battery possesses both good cycle performance and good thermal safety performance under high voltage and high temperature conditions.

[0145] The adhesion between the first material layer and the positive electrode current collector typically affects the cycle performance and thermal safety performance of lithium-ion batteries under high voltage and high temperature conditions. As can be seen from Examples 1-5 and Examples 3-1 to 3-10, within the range of adhesion between the first material layer and the positive electrode current collector in this application, the lithium-ion battery exhibits a higher number of cycle cycles and a higher thermal chamber test pass temperature, indicating that the lithium-ion battery possesses both good cycle performance and good thermal safety performance under high voltage and high temperature conditions.

[0146] The type of inorganic particles, the type of the first binder, and the type of the first conductive agent typically affect the cycle performance and thermal safety performance of lithium-ion batteries under high voltage and high temperature conditions. As can be seen from Examples 1-5 and Examples 3-8 to 3-10, by selecting the inorganic particles, first binder, and first conductive agent within the scope of this application, the lithium-ion battery exhibits a higher number of cycle cycles and a higher thermal chamber test pass temperature, indicating that the lithium-ion battery possesses both good cycle performance and good thermal safety performance under high voltage and high temperature conditions.

[0147] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. An electrochemical device comprising a positive electrode and an electrolyte, wherein the positive electrode comprises a positive current collector, a first material layer, and a positive material layer, the first material layer comprising inorganic particles, a first binder, and a first conductive agent, the first material layer being disposed on at least one surface of the positive current collector, and the positive material layer being disposed between the positive current collector and the first material layer; the ratio of the length of the first material layer to the length of the positive current collector is X%, and 50 ≤ X ≤ 98; The electrolyte comprises a first component and a second component, wherein the first component comprises at least one of a compound of formula I-1 or a compound of formula II-1: in, R 11 and R 12 Each is independently either substituted or unsubstituted C1-C 10 Alkyl, wherein R 11 and R 12 At least one of them has been replaced; R 21 and R 22 Each is independently either substituted or unsubstituted C1-C 10 Alkyl, wherein R 21 and R 22 At least one of them is substituted; when substituted, each substituent is independently a fluorine atom; The second component includes a compound of formula III: Among them, R 41 R 42 R 43 R 44 Each is independently H, F, substituted or unsubstituted C1-C3 alkyl group, and when substituted, the substituent is a fluorine atom, R. 41 R 42 R 43 R 44 At least one of them contains F; Based on the mass of the electrolyte, the mass percentage of the first component is A%, and the mass percentage of the second component is B%, satisfying: 40≤A+B≤90.

2. The electrochemical device according to claim 1, wherein, 5≤B≤15。 3. The electrochemical device according to claim 1, wherein, 4.3≤A / B≤19.

4. The electrochemical device according to claim 1, wherein, The electrolyte includes a third component, which comprises at least one of a compound of formula I-2 or a compound of formula II-2: Among them, R 13 R 14 R 23 and R 24 Each independently is C1-C 10 Alkyl group; based on the mass of the electrolyte, the mass percentage of the third component is C%, 0 < C ≤ 50%.

5. The electrochemical device according to claim 1, wherein, The compound of formula I-1 includes at least one of the following compounds: The compound of formula II-1 includes at least one of the following compounds:

6. The electrochemical device according to claim 1, wherein, The compound of formula III includes at least one of the following compounds:

7. The electrochemical device according to claim 4, wherein, The compound of formula I-2 includes at least one of methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, or propyl propionate; the compound of formula II-2 includes at least one of dimethyl carbonate, diethyl carbonate, or methyl ethyl carbonate.

8. The electrochemical device according to any one of claims 1 to 7, wherein, The electrolyte comprises a first lithium salt and a second lithium salt. The first lithium salt comprises at least one of lithium hexafluorophosphate or lithium bis(fluorosulfonyl)imide, and the second lithium salt comprises at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, lithium difluorooxalate borate, lithium dioxalate borate, or lithium difluorophosphate. Based on the mass of the electrolyte, the mass percentage of the second lithium salt is D%, 0.1 ≤ D ≤ 5%.

9. The electrochemical device according to any one of claims 1 to 7, wherein, 80≤X≤98。 10. The electrochemical device according to any one of claims 1 to 7, wherein, The thickness of the first material layer is H μm, where 0.1 ≤ H ≤ 10.

11. The electrochemical device according to any one of claims 1 to 7, wherein, The adhesion force between the first material layer and the positive electrode current collector is greater than or equal to 201 N / m.

12. The electrochemical device according to any one of claims 1 to 7, wherein, The inorganic particles include at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, gibbsite, barium sulfate, calcium sulfate, or calcium silicate; the first binder includes a copolymer formed by polymerizing acrylate, acrylamide, and acrylonitrile; the first conductive agent includes at least one of graphene, carbon nanotubes, graphite fibers, or conductive carbon.

13. An electronic device comprising the electrochemical device according to any one of claims 1 to 12.

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