Electrochemical device and electronic device

Abstract

An electrochemical device and an electronic device, the electrochemical device comprises an electrolyte and a positive pole piece, the electrolyte comprises a compound of formula I: based on the total mass of the electrolyte, the mass percentage A of the compound of formula I is 0.01-7%; the positive pole piece comprises a positive active material layer, the positive active material layer comprises a nickel element, the mass percentage content of the nickel element is B based on the total mass of the positive active material layer, and 0.1 < = 100A / B < = 17.5. The electrochemical device has good high-temperature cycle performance and high-temperature storage performance.

Description

Technical Field

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

[0002] Lithium-ion batteries, with their advantages of high operating voltage, high energy density, compact size, light weight, and environmental friendliness, are currently widely used in smart wearable devices, smartphones, drones, electric vehicles, and other fields. As the operating environments of various products become increasingly complex, higher requirements are placed on the energy density of lithium-ion batteries.

[0003] Ternary nickel cobalt lithium manganese oxide positive electrode active material has the advantages of low cost, good environmental protection, high energy density, and good cycle performance. It is an important high energy density material for lithium-ion batteries. As the nickel content increases, the energy density of the positive electrode active material is higher. However, excessive nickel content will cause the destruction of the positive electrode active material structure and generate microcracks due to anisotropic volume changes during the cycle, increasing the contact area between the positive electrode active material and the electrolyte, causing side reactions and reducing the cycle stability of the positive electrode active material. On the other hand, in the case of high oxidation state Ni 4+ In the presence of ions, the electrolyte is prone to oxidative decomposition, especially under high temperature conditions, where the reaction is exacerbated, causing the lithium-ion battery to expand rapidly and reducing the high-temperature storage and cycle performance of the lithium-ion battery. Therefore, while taking into account the energy density of the lithium-ion battery, improving the high-temperature cycle performance and high-temperature storage performance is of great significance to the application of lithium-ion batteries. Summary of the Invention

[0004] The purpose of the present application is to provide an electrochemical device and an electronic device to improve the high-temperature cycle performance and high-temperature storage performance of the electrochemical device.

[0005] It should be noted that in the invention content of this application, lithium-ion batteries are used as an example of electrochemical devices to explain this application, but the electrochemical devices of this application are not limited to lithium-ion batteries. The specific technical solutions are as follows:

[0006] A first aspect of the present application provides an electrochemical device, comprising an electrolyte and a positive electrode plate, wherein the electrolyte comprises a compound of formula I, and the mass percentage A of the compound of formula I is 0.01% to 7%, preferably 0.1% to 5%, based on the total mass of the electrolyte;

[0007]

[0008] wherein R1, R2, R3, and R4 are each independently selected from C=O or C-R6, and at least one of R1, R2, R3, and R4 is selected from C=O; R5 is selected from hydrogen, C1 to C 10 Alkyl, C2 to C 10Alkenyl, C2 to C 10 Alkynyl or C6 to C 12 R6 is selected from hydrogen atom, C1 to C 10 Alkyl or C6 to C 12 In one embodiment of the present application, R6 in R1, R2, R3, and R4 can be selected from different groups, for example, R6 can be selected from hydrogen atoms, C1 to C 10 Alkyl or C6 to C 12 In one embodiment of the present application, R6 in R1, R2, R3, and R4 can be selected from the same group, for example, R6 can be selected from hydrogen atoms, C1 to C 10 Alkyl or C6 to C 12 The positive electrode sheet includes a positive electrode active material layer, and the positive electrode active material layer includes nickel element. Based on the total mass of the positive electrode active material layer, the mass percentage of nickel element is B, 0.1≤100A / B≤17.5, preferably, 0.2≤100A / B≤12.5. When the mass percentage A and 100A / B values ​​of the compound of formula I are within the scope of this application, a high nickel positive electrode active material and a compound of formula I are used in combination. The compound of formula I can form a stable positive electrode solid interface film with suitable thickness and good ion diffusion performance on the positive electrode surface, improve the structural stability of the positive electrode active material during the cycle process, and inhibit the electrolyte solvent molecules from being oxidized by highly oxidized Ni on the surface of the positive electrode active material. 4+ Oxidative decomposition reduces the side reactions between the electrode active materials and the electrolyte, thereby improving the oxidative decomposition gas production of the electrolyte at high temperatures, and further improving the high-temperature storage performance and high-temperature cycle performance of the electrochemical device.

[0009] In one embodiment of the present application, the positive electrode active material layer includes lithium nickel cobalt manganese oxide. The mass percentage E of the cobalt element in the lithium nickel cobalt manganese oxide is 2.5% to 20% based on the total mass of the positive electrode active material layer, and 2≤B / E≤18. When the mass percentage of the cobalt element in the lithium nickel cobalt manganese oxide and the value of B / E are within the above ranges, the positive electrode active material can have a higher gram capacity and better structural stability, and synergistically act with the electrolyte in the electrochemical device to improve the high-temperature cycling performance and high-temperature storage performance of the electrochemical device.

[0010] In one embodiment of the present application, based on the total mass of the positive electrode active material layer, the mass percentage B of the nickel element is 28% to 60.2%. 2+ →Ni 3+ / Ni 4+When the mass percentage B of the nickel element is within the above range, lithium nickel cobalt manganese oxide has a high theoretical capacity and good structural stability, and has good cycle stability at both room temperature and high temperature, so that the material obtains a higher reversible specific capacity, improves the energy density of the positive electrode active material, and thus improves the high-temperature cycle performance and high-temperature storage performance of the electrochemical device.

[0011] In one embodiment of the present application, the compound of formula I comprises at least one of the following compounds:

[0012]

[0013]

[0014] The compound of formula I includes at least one of the above compounds, which can form a stable positive electrode solid interface film with suitable thickness and good ion diffusion performance on the positive electrode surface, improve the structural stability of the positive electrode active material during the cycle, and inhibit the electrolyte solvent molecules from being oxidized by highly oxidized Ni on the surface of the positive electrode active material. 4+ Oxidative decomposition improves the oxidative decomposition gas production of the electrolyte at high temperature, thereby improving the high-temperature storage performance and high-temperature cycle performance of the electrochemical device.

[0015] In one embodiment of the present application, the electrolyte further includes a first additive, the first additive including at least one of fluoroethylene carbonate, vinylene carbonate, vinyl sulfate, or 1,3-propane sultone; based on the total mass of the electrolyte, the mass percentage C of the first additive is 0.01% to 15%, preferably 0.5% to 5%. When the mass percentage C of the first additive is within the above range, the first additive can form a positive electrode solid interface (SEI) film at the positive electrode interface before the compound of formula I, thereby reducing side reactions between the electrolyte and the surface of the positive electrode active material and reducing the consumption of the compound of formula I. As a result, the compound of formula I can form a stable SEI film at the positive electrode interface in the late stage of the cycle, thereby ensuring the electrochemical stability of the electrochemical device in the late stage of the cycle, thereby improving the high temperature cycle performance and high temperature storage performance of the electrochemical device.

[0016] In one embodiment of the present application, the electrolyte includes a lithium salt additive, the lithium salt additive including at least one of lithium difluorophosphate, lithium tetrafluoroborate, lithium trifluoromethanesulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium bisoxalatoborate, or lithium difluorooxalatoborate; based on the total mass of the electrolyte, the mass percentage D of the lithium salt additive is 0.01% to 5%, preferably 0.2% to 2%. When the mass percentage D of the lithium salt additive is within the above range, the positive electrode solid interface film can be made more stable and not easily decomposed during charge and discharge cycles, thereby improving the high-temperature cycling performance and high-temperature storage performance of the electrochemical device.

[0017] A second aspect of the present application provides an electronic device, which includes the electrochemical device according to any one of the aforementioned embodiments.

[0018] Beneficial effects of this application:

[0019] The present application provides an electrochemical device and an electronic device. The electrochemical device includes an electrolyte and a positive electrode plate, wherein the electrolyte includes a compound of formula I, and the mass percentage of the compound of formula I based on the total mass of the electrolyte is A; the positive electrode plate includes a positive electrode active material layer, and the positive electrode active material layer includes nickel, and the mass percentage of nickel based on the total mass of the positive electrode active material layer is B. High nickel positive electrode active materials generally have high energy density, which is mainly due to the fact that nickel can realize Ni 2+ →Ni 3+ / Ni 4+ The reversible transformation enables the material to obtain a higher reversible specific capacity, thereby improving the energy density of the positive electrode active material, and as the nickel content increases, the energy density of the positive electrode active material is higher. On the one hand, the anhydride group in the compound of formula I can adsorb trace water in the electrolyte, and on the other hand, the acidic substance can neutralize the residual base group of the positive electrode, reduce the decomposition effect of the base on the carbonate, and increase the stability of the electrolyte. Without being limited to any theory, the inventors of the present application found that the combination of high nickel positive electrode active materials and compounds of formula I can form a stable positive electrode solid interface film with suitable thickness and good ion diffusion performance on the surface of the positive electrode, improve the structural stability of the positive electrode active material during the cycle, and inhibit the electrolyte solvent molecules from being absorbed by the highly oxidized Ni on the surface of the positive electrode active material. 4+ Oxidative decomposition reduces the side reactions between the electrode active materials and the electrolyte, thereby improving the oxidative decomposition gas production of the electrolyte at high temperatures, and further improving the high-temperature storage performance and high-temperature cycle performance of the electrochemical device.

[0020] Of course, it is not necessary to achieve all the advantages described above at the same time when implementing any product or method of the present application. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the embodiments described are only part of the embodiments of the present application, not all of the embodiments. All other embodiments obtained by those skilled in the art based on the present application are within the scope of protection of the present application.

[0022] It should be noted that, in the specific embodiments of the present application, a lithium-ion battery is used as an example of an electrochemical device to explain the present application, but the electrochemical device of the present application is not limited to a lithium-ion battery.

[0023] A first aspect of the present application provides an electrochemical device, comprising an electrolyte and a positive electrode plate, wherein the electrolyte comprises a compound of formula I, and the mass percentage A of the compound of formula I is 0.01% to 7%, preferably 0.1% to 5%, based on the total mass of the electrolyte;

[0024]

[0025] wherein R1, R2, R3, and R4 are each independently selected from C=O or C-R6, and at least one of R1, R2, R3, and R4 is selected from C=O; R5 is selected from hydrogen, C1 to C 10 Alkyl, C2 to C 10 Alkenyl, C2 to C 10 Alkynyl or C6 to C 12 R6 is selected from hydrogen atom, C1 to C 10 Alkyl or C6 to C 12 In one embodiment of the present application, R6 in R1, R2, R3, and R4 can be selected from different groups, for example, R6 can be selected from hydrogen atoms, C1 to C 10 Alkyl or C6 to C 12 In one embodiment of the present application, R6 in R1, R2, R3, and R4 can be selected from the same group, for example, R6 can be selected from hydrogen atoms, C1 to C 10 Alkyl or C6 to C 12 of aromatic groups.

[0026] The positive electrode sheet includes a positive electrode active material layer, and the positive electrode active material layer includes nickel element. Based on the total mass of the positive electrode active material layer, the mass percentage of nickel element is B, 0.1≤100A / B≤17.5, preferably, 0.2≤100A / B≤12.5. For example, the mass percentage A of the compound of formula I can be 0.01%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7% or a range consisting of any two values ​​therein; the value of 100A / B can be 0.1, 0.2, 1, 2.5, 5, 7.5, 10, 12.5, 15, 17.5 or a range consisting of any two values ​​therein. High nickel positive electrode active materials generally have high energy density, which is mainly due to the fact that nickel element can realize Ni 2+ →Ni 3+ / Ni 4+The reversible transformation enables the material to obtain a higher reversible specific capacity, thereby improving the energy density of the positive electrode active material, and as the nickel content increases, the energy density of the positive electrode active material is higher. On the one hand, the anhydride group in the compound of formula I can adsorb trace water in the electrolyte, and on the other hand, the acidic substance can neutralize the residual base group of the positive electrode, reduce the decomposition effect of the base on the carbonate, and increase the stability of the electrolyte. Without being limited to any theory, the inventors of the present application found that when the mass percentage A of the compound of formula I and the value of 100A / B are within the scope of this application, a high nickel positive electrode active material and a compound of formula I are used in combination, and the compound of formula I can form a stable positive electrode solid interface film with suitable thickness and good ion diffusion performance on the surface of the positive electrode, thereby improving the structural stability of the positive electrode active material during the cycle process and inhibiting the electrolyte solvent molecules from being absorbed by the highly oxidized Ni on the surface of the positive electrode active material. 4+ Oxidative decomposition reduces the side reactions between the electrode active material and the electrolyte, thereby improving the oxidative decomposition gas production of the electrolyte at high temperature, and further improving the high-temperature storage performance and high-temperature cycle performance of the electrochemical device. When the value of 100A / B is too high, the film formation impedance is relatively large, which in turn leads to an increase in the impedance of the electrochemical device, affecting the cycle performance of the electrochemical device to a certain extent; when the value of 100A / B is too low, it is not enough to form a relatively good interface protection, which affects the improvement of the cycle performance of the electrochemical device to a certain extent. In this application, "high temperature" refers to a temperature ≥ 60°C.

[0027] In one embodiment of the present application, the positive electrode active material layer includes lithium nickel cobalt manganese oxide, and the mass percentage E of the cobalt element in the lithium nickel cobalt manganese oxide is 2.5% to 20% based on the total mass of the positive electrode active material layer, and 2≤B / E≤18. For example, the mass percentage E of the cobalt element in the lithium nickel cobalt manganese oxide can be 2.5%, 5%, 8%, 11%, 14%, 17%, 20% or a range consisting of any two values ​​therein; the value of B / E can be 2, 4, 6, 8, 10, 12, 14, 16, 18 or a range consisting of any two values ​​therein. When the mass percentage of the cobalt element in the lithium nickel cobalt manganese oxide and the value of B / E are within the above ranges, the positive electrode active material can have a higher gram capacity and better structural stability, and synergize with the electrolyte in the electrochemical device to improve the high temperature cycle performance and high temperature storage performance of the electrochemical device. In the present application, lithium nickel cobalt manganese oxide may include but is not limited to, LiNi 0.5 Co 0.2 Mn 0.3 O2、LiNi 0.6 Co 0.1 Mn 0.3 O2、LiNi 0.6 Co 0.2 Mn 0.2 O2、LiNi0.8 Co 0.1 Mn 0.1 O2 or LiNi 0.9 Co 0.05 Mn 0.05 At least one of O2.

[0028] In one embodiment of the present application, the mass percentage B of the nickel element is 28% to 60.2% based on the total mass of the positive electrode active material layer. For example, the mass percentage B of the nickel element can be 28%, 30%, 35%, 40%, 45%, 50%, 55%, 60.2% or a range consisting of any two of these values. Nickel can achieve Ni 2+ →Ni 3+ / Ni 4+ When the mass percentage B of the nickel element is within the above range, lithium nickel cobalt manganese oxide has a high theoretical capacity and good structural stability, and has good cycle stability at both room temperature and high temperature, so that the material obtains a higher reversible specific capacity, improves the energy density of the positive electrode active material, and thus improves the high-temperature cycle performance and high-temperature storage performance of the electrochemical device.

[0029] In one embodiment of the present application, the compound of formula I comprises at least one of the following compounds:

[0030]

[0031]

[0032] The compound of formula I includes at least one of the above compounds, which can form a stable positive electrode solid interface film with suitable thickness and good ion diffusion performance on the positive electrode surface, improve the structural stability of the positive electrode active material during the cycle, and inhibit the electrolyte solvent molecules from being oxidized by highly oxidized Ni on the surface of the positive electrode active material. 4+ Oxidative decomposition improves the oxidative decomposition gas production of the electrolyte at high temperature, thereby improving the high-temperature storage performance and high-temperature cycle performance of the electrochemical device.

[0033] In one embodiment of the present application, the electrolyte includes a first additive, the first additive including at least one of fluoroethylene carbonate (FEC), vinylene carbonate, vinyl sulfate or 1,3-propane sultone; based on the total mass of the electrolyte, the mass percentage C of the first additive is 0.01% to 15%, preferably 0.5% to 5%. For example, the mass percentage C of the first additive can be 0.01%, 0.5%, 1%, 3%, 5%, 7%, 9%, 11%, 13%, 15% or a range consisting of any two values ​​therein. When the mass percentage C of the first additive is within the above range, the first additive can form an SEI film at the positive electrode interface before the compound of formula I, reducing the side reaction between the electrolyte and the surface of the positive electrode active material, while reducing the consumption of the compound of formula I, so that the compound of formula I can form a stable SEI film at the positive electrode interface in the later stage of the cycle, providing a guarantee for the electrochemical stability of the electrochemical device in the later stage of the cycle, thereby improving the high temperature cycle performance and high temperature storage performance of the electrochemical device.

[0034] In one embodiment of the present application, the electrolyte includes a lithium salt additive, and the lithium salt additive includes at least one of lithium difluorophosphate, lithium tetrafluoroborate, lithium trifluoromethanesulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium bisoxalatoborate, or lithium difluorooxalatoborate; based on the total mass of the electrolyte, the mass percentage D of the lithium salt additive is 0.01% to 5%, preferably 0.2% to 2%. For example, the mass percentage D of the lithium salt additive can be 0.01%, 0.2%, 0.5%, 1%, 2%, 3%, 4%, 5%, or a range consisting of any two of these values. When the mass percentage D of the lithium salt additive is within the above range, the positive electrode solid interface film can be made more stable and not easily decomposed during the charge and discharge cycle, thereby improving the high-temperature cycle performance and high-temperature storage performance of the electrochemical device.

[0035] In the present application, the electrolyte also includes a lithium salt. There is no particular limitation on the lithium salt in the present application. Any lithium salt known in the art can be used, as long as the purpose of the present application can be achieved. For example, the lithium salt can be selected from at least one of lithium hexafluorophosphate (LiPF6), LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiC(SO2CF3)3, or Li2SiF6. Based on the total mass of the electrolyte, the mass percentage of the lithium salt can be 8% to 20%, for example, the mass percentage of the lithium salt can be 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 18%, 20%, or a range consisting of any two of these values. In the present application, the electrolyte also includes a non-aqueous solvent. There is no particular limitation on the non-aqueous solvent in the present application, as long as the purpose of the present application can be achieved. For example, the non-aqueous solvent can include, but is not limited to, at least one of a carbonate compound, a carboxylate compound, an ether compound, or other organic solvent.

[0036] Above-mentioned carbonate compound can include but not limited to at least one in linear carbonate compound, cyclic carbonate compound.Above-mentioned linear carbonate compound can include but not limited to at least one in dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC) or methyl ethyl carbonate (MEC).Above-mentioned cyclic carbonate compound can include but not limited to at least one in ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC) or vinyl ethylene carbonate (VEC).Above-mentioned carboxylate compound can include but not limited to at least one in methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, gamma-butyrolactone, decanolactone, valerolactone or caprolactone. The ether compound may include, but is not limited to, at least one of dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. The other organic solvent may include, but is not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate.

[0037] The present application does not particularly limit the content of the non-aqueous solvent in the electrolyte, as long as the objectives of the present application can be achieved. For example, based on the total mass of the electrolyte, the mass percentage of the non-aqueous solvent is 58% to 91.99%. For example, the mass percentage of the non-aqueous solvent can be 58%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91.99%, or a range consisting of any two of these values.

[0038] In one embodiment of the present application, the electrolyte may include a compound of Formula I, a lithium salt, and a non-aqueous solvent, wherein the weight percentages of the compound of Formula I and the lithium salt are as described above, and the weight percentage of the non-aqueous solvent is 78% to 91.99%. An electrochemical device including the above electrolyte has good high-temperature cycling performance and high-temperature storage performance.

[0039] In one embodiment of the present application, the electrolyte may include a compound of Formula I, a first additive, a lithium salt, and a non-aqueous solvent. The weight percentages of the compound of Formula I, the first additive, and the lithium salt are as described above, and the weight percentage of the non-aqueous solvent is 63% to 91.98%. An electrochemical device including the above electrolyte has good high-temperature cycling performance and high-temperature storage performance.

[0040] In one embodiment of the present application, the electrolyte may include a compound of Formula I, a lithium salt additive, a lithium salt, and a non-aqueous solvent, wherein the weight percentages of the compound of Formula I, the lithium salt additive, and the lithium salt are as described above, and the weight percentage of the non-aqueous solvent is 73% to 91.98%. An electrochemical device including the above electrolyte has good high-temperature cycling performance and high-temperature storage performance.

[0041] In one embodiment of the present application, the electrolyte may include a compound of Formula I, a first additive, a lithium salt additive, a lithium salt, and a non-aqueous solvent, wherein the weight percentages of the compound of Formula I, the first additive, the lithium salt additive, and the lithium salt are as described above, and the weight percentage of the non-aqueous solvent is 58% to 91.97%. An electrochemical device including the above electrolyte has good high-temperature cycling performance and high-temperature storage performance.

[0042] The present application does not particularly limit the preparation method of lithium nickel cobalt manganese oxide, as long as the purpose of the present application can be achieved. For example, the preparation method of lithium nickel cobalt manganese oxide may include, but is not limited to, the following steps: uniformly mixing a cobalt-containing compound, a nickel-containing compound, a manganese-containing compound, and a lithium-containing compound, and then heat-treating the mixture in an air atmosphere to obtain lithium nickel cobalt manganese oxide. The nickel-containing compound may include, but is not limited to, at least one of NiCO3, NiO, Ni(OH)2, NiSO4, Ni(NO3)2, or Ni(CH3COO)2; the cobalt-containing compound may include, but is not limited to, at least one of CoSO4, Co(NO3)2, or Co(CH3COO)2; the manganese-containing compound may include, but is not limited to, at least one of MnSO4, Mn(NO3)2, or Mn(CH3COO)2; and the lithium-containing compound may include, but is not limited to, at least one of LiCH3COO, Li2CO3, LiOH, or LiNO3. The present application has no particular restrictions on the temperature, time and heating rate of the above-mentioned heat treatment, as long as the purpose of the present application can be achieved. For example, the heat treatment temperature is 650°C to 850°C, the time is 22h to 26h, and the heating rate is 2°C / min to 8°C / min.

[0043] In the present application, the mass percentage B of the nickel element and the mass percentage E of the cobalt element in the positive electrode active material layer can be controlled by adjusting the mass ratio of the cobalt-containing compound, the nickel-containing compound, and the manganese-containing compound during the preparation of the lithium nickel cobalt manganese oxide. For example, when the mass percentage of the nickel element remains unchanged, the amount of the manganese-containing compound added is reduced and the amount of the cobalt-containing compound added is increased, and the mass ratio of the cobalt-containing compound, the nickel-containing compound, and the manganese-containing compound changes accordingly, the mass percentage of the cobalt element increases, and the mass percentage of the manganese element decreases; increasing the amount of the manganese-containing compound added and reducing the amount of the cobalt-containing compound added, the mass ratio of the cobalt-containing compound, the nickel-containing compound, and the manganese-containing compound changes accordingly, the mass percentage of the cobalt element decreases, and the mass percentage of the manganese element increases. When the mass percentage of the cobalt element remains unchanged, the amount of the manganese-containing compound added is reduced and the amount of the nickel-containing compound added is increased, the mass ratio of the cobalt-containing compound, the nickel-containing compound and the manganese-containing compound changes accordingly, the mass percentage of the nickel element increases, and the mass percentage of the manganese element decreases; when the amount of the manganese-containing compound added is increased and the amount of the nickel-containing compound added is reduced, the mass ratio of the cobalt-containing compound, the nickel-containing compound and the manganese-containing compound changes accordingly, the mass percentage of the nickel element decreases, and the mass percentage of the manganese element increases.

[0044] In the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. The above-mentioned "positive electrode active material layer disposed on at least one surface of the positive electrode current collector" means that the positive electrode active material layer can be disposed on one surface of the positive electrode current collector along its thickness direction, or it can be disposed on two surfaces of the positive electrode current collector along its thickness direction. It should be noted that the "surface" here can be the entire area of ​​the positive electrode current collector surface or a partial area of ​​the positive electrode current collector surface. This application is not particularly limited, as long as the purpose of this application can be achieved.

[0045] The present application has no particular limitation on the positive electrode current collector, as long as the purpose of the present application can be achieved. For example, it can include aluminum foil, aluminum alloy foil or a composite current collector (such as an aluminum-carbon composite current collector).

[0046] In the present application, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes lithium nickel cobalt manganese oxide. The positive electrode active material layer may also include a conductive agent and a binder. The present application does not particularly limit the types of the conductive agent and the binder, as long as the purpose of the present application can be achieved. The present application does not particularly limit the mass ratio of the positive electrode active material, the conductive agent, and the binder in the positive electrode active material layer. Those skilled in the art can choose according to actual needs, as long as the purpose of the present application can be achieved. For example, the mass ratio of the positive electrode active material, the conductive agent, and the binder in the positive electrode active material layer can be (93 to 97): (1 to 3): (2 to 5).

[0047] The present application has no particular limitation on the binder, as long as the purpose of the present application can be achieved. For example, the binder may include but is not limited to at least one of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, styrene-acrylate copolymer, styrene-butadiene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinyl acetate, polyvinyl pyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene.

[0048] The present application does not particularly limit the conductive agent, as long as it can achieve the purpose of the present application. For example, the conductive agent may include, but is not limited to, at least one of conductive carbon black, flake graphite, graphene, carbon nanotubes, or carbon fibers. In the present application, the conductive carbon black includes at least one of acetylene black and Ketjen black.

[0049] The thickness of the positive electrode current collector and the positive electrode active material layer is not particularly limited in this application, as long as the purpose of this application can be achieved. For example, the thickness of the positive electrode current collector is 5 μm to 20 μm, and the thickness of the single-sided positive electrode active material layer is 30 μm to 120 μm.

[0050] Optionally, the positive electrode sheet may further include a conductive layer positioned between the positive electrode current collector and the positive electrode active material layer. The composition of the conductive layer is not particularly limited and may be any commonly used conductive layer in the art. The conductive layer includes a conductive agent and a binder. The present application does not particularly limit the conductive agent and binder in the conductive layer; for example, the conductive layer may be at least one of the aforementioned conductive agents and binders.

[0051] In the present application, the electrochemical device also includes an isolation membrane. The present application has no particular restrictions on the isolation membrane, as long as the purpose of the present application can be achieved. For example, the material of the isolation membrane may include but is not limited to polyethylene (PE), polypropylene (PP)-based polyolefins (PO), polyesters (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex or aramid. The type of isolation membrane may include at least one of a woven membrane, a non-woven membrane, a microporous membrane, a composite membrane, a rolled membrane or a spun membrane.

[0052] In some embodiments of the present application, the separator may include a substrate layer and a surface treatment layer. The substrate layer may be a non-woven fabric or a composite film having 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 film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric, or a polypropylene-polyethylene-polypropylene porous composite film may be used.

[0053] 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 a polymer and an inorganic layer.

[0054] In some embodiments of the present application, the inorganic layer includes inorganic particles and a binder. The application is not particularly limited to inorganic particles. For example, inorganic particles can 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 or barium sulfate. The application is not particularly limited to the binder. For example, the binder can be at least one of the above-mentioned binders. In some embodiments of the present application, the polymer layer includes polymer, and the material of the polymer includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinyl pyrrolidone, polyvinyl ether or polyvinylidene fluoride or poly (vinylidene fluoride-hexafluoropropylene).

[0055] In some embodiments of the present application, the inorganic layer may further include a thickening agent and a wetting agent. There are no particular limitations on the types of the thickening agent and the wetting agent in the present application, as long as the objectives of the present application can be achieved. For example, the thickening agent may include, but is not limited to, at least one of sodium carboxymethyl cellulose or lithium carboxymethyl cellulose; the wetting agent may include, but is not limited to, at least one of dimethyl silicone, sodium dodecyl sulfate, trialkyl phosphate, methyl decanoate or dodecyl acetate.

[0056] In the present application, there is no particular limitation on the thickness of the separator membrane, as long as the objectives of the present application can be achieved. For example, the thickness of the separator membrane may be 4 μm to 30 μm.

[0057] In the present application, the electrochemical device further includes a negative electrode sheet, which includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector. The above "negative electrode active material layer provided on at least one surface of the negative electrode current collector" means that the negative electrode active material layer may be provided on one surface of the negative electrode current collector along its own thickness direction, or may be provided on both surfaces of the negative electrode current collector along its own thickness direction. It should be noted that the "surface" here may be the entire area of the surface of the negative electrode current collector, or may be a partial area of the surface of the negative electrode current collector. There are no particular limitations in the present application, as long as the objectives of the present application can be achieved.

[0058] There are no particular limitations on the negative electrode current collector in the present application, as long as the objectives of the present application can be achieved. For example, it may include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam or a composite current collector. Exemplarily, the composite current collector may be a lithium-copper composite current collector, a carbon-copper composite current collector, a nickel-copper composite current collector, a titanium-copper composite current collector, etc.

[0059] The negative electrode active material layer of the present application includes a negative electrode active material. There are no particular limitations on the type of the negative electrode active material in the present application, as long as the objectives of the present application can be achieved. For example, the negative electrode active material may include natural graphite, artificial graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO x (0 < x < 2), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel-structured lithium titanate Li4Ti5O 12 , Li-Al alloy or metallic lithium, etc.

[0060] There are no particular limitations on the thickness of the negative electrode current collector and the negative electrode active material layer in the present application, as long as the objectives of the present application can be achieved. For example, the thickness of the negative electrode current collector is 4 μm to 15 μm, and the thickness of the negative electrode active material layer is 30 μm to 120 μm.

[0061] In some embodiments of the present application, the negative electrode active material layer may further include a conductive agent, a binder and a thickener. The present application does not particularly limit the types of the conductive agent, binder and thickener, as long as the purpose of the present application can be achieved. For example, the binder may include but is not limited to at least one of styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), water-based acrylic resin or carboxymethyl cellulose (CMC). The conductive agent may include but is not limited to at least one of conductive carbon black, lamellar graphite, graphene, carbon nanotubes, carbon fibers or carbon nanowires. In the present application, the conductive carbon black includes at least one of acetylene black and Ketjen black. The thickener may include but is not limited to at least one of carboxymethyl cellulose (CMC), sodium carboxymethyl cellulose or lithium carboxymethyl cellulose.

[0062] The present application does not particularly limit the mass ratio of the negative electrode active material, binder, and thickener in the negative electrode active material layer. Those skilled in the art can select according to actual needs, as long as the purpose of the present application can be achieved. For example, the mass ratio of the negative electrode active material, binder, and thickener in the negative electrode active material layer can be (93 to 97): (1 to 3): (2 to 5).

[0063] The electrochemical device also includes a housing for accommodating the positive electrode sheet, separator, negative electrode sheet, and electrolyte, as well as other components known in the field of electrochemical devices. This application does not limit these other components. This application does not particularly limit the housing, and it can be any housing known in the art, as long as it can achieve the purpose of this application. For example, the housing can be a hard shell housing or a flexible shell housing. The material of the hard shell housing can be metal. This application does not limit the type of metal, and a metal hard shell housing known in the art can be used, as long as it can achieve the purpose of this application. The flexible shell can be a metal plastic film, such as an aluminum plastic film, a steel plastic film, etc.

[0064] The preparation process of the electrochemical device of the present application is well known to those skilled in the art and is not particularly limited in the present application. For example, the preparation process of the electrochemical device may include but is not limited to the following steps: stacking the positive electrode sheet, the separator and the negative electrode sheet in order, and winding, folding and other operations as needed to obtain an electrode assembly with a wound structure, placing the electrode assembly in a shell, injecting the electrolyte into the shell and sealing it to obtain the electrochemical device. Alternatively, stacking the positive electrode sheet, the separator and the negative electrode sheet in order, and then fixing the four corners of the entire stacked structure with tape to obtain an electrode assembly with a stacked structure, placing the electrode assembly in a shell, injecting the electrolyte into the shell and sealing it to obtain the electrochemical device. In addition, as needed, overcurrent protection elements, guide plates, etc. can also be placed in the shell to prevent pressure rise and overcharging and discharging inside the electrochemical device.

[0065] A second aspect of the present application provides an electronic device, which includes the electrochemical device according to any one of the aforementioned embodiments.

[0066] The electronic device of the present application is not particularly limited and can be any electronic device known in the art. In some embodiments, the electronic device may include, but is not limited to, a laptop computer, a pen-type computer, a mobile computer, an electronic book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a headset, a video recorder, an LCD television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flashlight, a camera, a large household battery, and a lithium-ion capacitor.

[0067] Example

[0068] The following examples and comparative examples are provided to more specifically illustrate the embodiments of the present invention. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0069] Test methods and equipment:

[0070] Ni and Co element content test

[0071] After the lithium-ion battery was discharged to 3V at 0.2C, the positive electrode sheet was removed and cut into 10 small discs with a diameter of 16mm. The positive active material layer was scraped off from the positive current collector of a single small disc with a knife to obtain a powder. 0.2g of the powder was weighed and digested with 10mL of aqua regia and diluted to volume with deionized water in a 100mL volumetric flask. Then, an inductively coupled plasma analyzer (ICP, model AVIO-200) was used, with the radio frequency generator (RF) frequency set to 40.68MHz, the argon secondary pressure to 0.6MPa, the RF power to 1400W, and the pump speed to 1.0mL / min. The content of each element in the positive active material layer of a single small disc was tested, and the content of each element obtained from the above 10 small discs was averaged to obtain the content of Co and Ni elements in the positive active material layer. Wherein, aqua regia was obtained by mixing concentrated nitric acid and concentrated hydrochloric acid in a volume ratio of 1:1.

[0072] Electrolyte composition test

[0073] The lithium-ion battery was discharged at 0.2C to 3V and then disassembled to obtain the positive and negative electrode sheets. The positive and negative electrode sheets were placed in a centrifuge tube and centrifuged to obtain an electrolyte. The centrifuged electrolyte was then analyzed using gas chromatography-mass spectrometry (GC-MS) to determine the mass percentage of various substances (e.g., the compound of Formula I, additives, and lithium salt additives) in the electrolyte.

[0074] High temperature cycle performance test

[0075] At 60°C, the lithium-ion battery is charged to 4.3V at a constant current of 1C, charged to 0.05C at a constant voltage of 4.3V, and then discharged to 3V at a constant current of 4C. This is one charge and discharge cycle, and the charge and discharge cycle is carried out under this condition for 1000 cycles. The discharge capacity after 1 cycle is recorded as the initial discharge capacity C0, and the discharge capacity after 1000 cycles is recorded as C1. The high-temperature cycle performance of the lithium-ion battery is characterized by the cycle capacity retention rate of the lithium-ion battery after 1000 cycles at 60°C. The greater the cycle capacity retention rate of the lithium-ion battery after 1000 cycles at 60°C, the better the high-temperature cycle performance of the lithium-ion battery. Cycle capacity retention rate (%) = C1 / C0×100%.

[0076] High temperature storage performance test

[0077] Take the lithium-ion battery to be tested and measure the original thickness d0 of the lithium-ion battery. At 25°C, charge the lithium-ion battery to 4.3V at a constant current of 0.5C, and charge it to 0.05C at a constant voltage of 4.3V. The lithium-ion battery is in a fully charged state. Then place the lithium-ion battery in a 60°C constant temperature box for high-temperature storage for 15 days. Use a micrometer to measure the thickness d1 of the lithium-ion battery after storage. The high-temperature storage performance of the lithium-ion battery is characterized by the thickness expansion rate of the lithium-ion battery stored at 60°C for 15 days. The smaller the thickness expansion rate of the lithium-ion battery stored at 60°C for 15 days, the better the high-temperature storage performance of the lithium-ion battery. Thickness expansion rate (%) = (d1-d0) / d0×100%.

[0078] Example 1-1

[0079] <Preparation of positive electrode sheet>

[0080] Lithium nickel cobalt manganese oxide LiNi 0.6 Co 0.1 Mn 0.3O2, conductive agent carbon nanotubes (CNT), and binder polyvinylidene fluoride are mixed in a mass ratio of 95:2:3, and N-methylpyrrolidone (NMP) is added as a solvent. The mixture is stirred in a vacuum mixer until the system becomes a uniform positive electrode slurry with a solid content of 75wt%. The positive electrode slurry is evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10μm and dried at 120℃ to obtain a positive electrode sheet with a single-sided positive electrode active material layer. The coating weight of the positive electrode active material layer is 267.8mg / 1540mm 2 Repeat the above steps on the other surface of the aluminum foil to obtain a positive electrode sheet coated with a positive electrode active material layer on both sides. After drying at 120°C and cold pressing, the sheet is cut and the tabs are welded to obtain a positive electrode sheet with a size of 74mm×867mm for use. The compacted density of the positive electrode active material layer is 4.15g / cm 3 .

[0081] <Preparation of negative electrode sheet>

[0082] The negative electrode active materials, artificial graphite, styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC), were mixed in a mass ratio of 95:2:3. Deionized water was then added as a solvent to form a slurry with a solid content of 70 wt%. The mixture was then stirred evenly in a vacuum mixer to obtain a negative electrode slurry. The negative electrode slurry was evenly coated on one surface of a 6 μm thick negative electrode current collector copper foil and dried at 120°C to obtain a negative electrode sheet coated with a negative electrode active material layer on one side. The coating weight of the negative electrode active material layer was 142 mg / 1540 mm. 2 Repeat the above steps on the other surface of the copper foil to obtain a negative electrode sheet coated with a negative electrode active material layer on both sides. After drying at 120°C and cold pressing, the sheet is cut and the tabs are welded to obtain a negative electrode sheet with a size of 78mm×875mm for use. The compacted density of the negative electrode active material layer is 1.74g / cm 3 .

[0083] <Preparation of Electrolyte>

[0084] In an argon atmosphere glove box with a water content of less than 10 ppm, the carbonate compounds ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) were uniformly mixed in a weight ratio of 10:30:60 to obtain a base solvent, to which the compound of formula I-1 and the lithium salt LiPF6 were added and stirred to obtain an electrolyte. The mass percentage A of the compound of formula I, based on the total mass of the electrolyte, was 2%, the mass percentage of the lithium salt LiPF6 was 12.5%, and the balance was the base solvent.

[0085] <Isolation Film>

[0086] A polyethylene porous polymer film with a thickness of 15 μm (manufacturer: Celgard Membrane Co., Ltd., USA) was used as a separator.

[0087] <Preparation of lithium-ion batteries>

[0088] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator positioned between the positive and negative electrodes to provide insulation. The electrode assembly is then wound and placed in an aluminum-plastic film packaging bag. The bag is then dehydrated at 80°C and filled with the prepared electrolyte. The battery is vacuum packaged, allowed to stand, formed, and shaped to produce a lithium-ion battery. The upper limit of the formation voltage is 4.15V, the formation temperature is 70°C, and the formation standing time is 2 hours.

[0089] Example 1-2 to Example 1-5

[0090] Except that the type and mass percentage of the compound of formula I in <Preparation of electrolyte> are adjusted according to Table 1, the mass percentage of the base solvent is changed accordingly, the mass ratio of the components of the base solvent remains unchanged, and the mass percentage of the lithium salt remains unchanged, the rest is the same as Example 1-1.

[0091] Example 1-6 to Example 1-15

[0092] Except for adjusting the relevant parameters in <Preparation of Positive Electrode Sheet> according to Table 1, the rest is the same as Example 1-1.

[0093] Example 2-1 to Example 2-17

[0094] In addition to adding the first additive and / or the lithium salt additive in <Preparation of the Electrolyte>, and adjusting the type and mass percentage of the first additive and the type and mass percentage of the lithium salt additive, the mass percentage of the base solvent is changed accordingly, the mass ratio of the components of the base solvent remains unchanged, and the mass percentage of the lithium salt remains unchanged, the rest is the same as Example 1-1.

[0095] Comparative Example 1

[0096] The preparation process is the same as Example 1-1 except that the compound of formula I is not added in the preparation of the electrolyte, the mass percentage of the base solvent is changed accordingly, the mass ratio of the components of the base solvent remains unchanged, and the mass percentage of the lithium salt remains unchanged.

[0097] Comparative Example 2

[0098] Except that the mass percentage of the compound of Formula I in <Preparation of Electrolyte> is adjusted according to Table 1, the mass percentage of the base solvent is changed accordingly, the mass ratio of the components of the base solvent remains unchanged, and the mass percentage of the lithium salt remains unchanged, the rest is the same as Example 1-1.

[0099] The preparation parameters and performance parameters of each embodiment and comparative example are shown in Tables 1 and 2.

[0100] Table 1

[0101]

[0102] Note: “ / ” in Table 1 indicates that there is no corresponding preparation parameter or substance.

[0103] As can be seen from Examples 1-1 to 1-15 and Comparative Examples 1 to 2, when an electrolyte containing a compound of Formula I and a positive electrode sheet containing nickel are combined and applied to a lithium-ion battery, when the mass percentage A of the compound of Formula I and the values ​​of 100A / B are within the ranges of this application, the lithium-ion battery has a high cycle capacity retention rate and a low thickness expansion rate, indicating that the high-temperature cycle performance and high-temperature storage performance of the lithium-ion battery are improved. In Comparative Examples 1 to 2, when the mass percentage A of the compound of Formula I and / or the values ​​of 100A / B are outside the ranges of this application, the resulting lithium-ion battery has a low cycle capacity retention rate and a high thickness expansion rate, indicating that the lithium-ion battery has poor high-temperature cycle performance and high-temperature storage performance.

[0104] It can be seen from Examples 1-1 and 1-6 to 1-9 that when the mass percentage B of the nickel element is within the range of this application, the cycle capacity retention rate of the lithium-ion battery is high and the thickness expansion rate is low, indicating that the high-temperature cycle performance and high-temperature storage performance of the lithium-ion battery are improved.

[0105] It can be seen from Example 1-1, Example 1-10 to Example 1-11, and Example 1-14 to Example 1-15 that when the mass percentage E of the cobalt element and the ratio B / E of the mass percentage of the nickel element to the mass percentage of the cobalt element are within the range of this application, the cycle capacity retention rate of the lithium-ion battery is high and the thickness expansion rate is low, indicating that the high-temperature cycle performance and high-temperature storage performance of the lithium-ion battery are improved.

[0106] Table 2

[0107]

[0108] Note: “ / ” in Table 2 indicates that there is no corresponding preparation parameter or substance.

[0109] The type and weight percentage C of the first additive generally affect the high-temperature cycling and storage performance of lithium-ion batteries. As can be seen from Examples 2-1 to 2-7, when the type and weight percentage C of the first additive are within the ranges of this application, the lithium-ion battery exhibits a high cycle capacity retention rate and a low thickness expansion rate, indicating that the high-temperature cycling and storage performance of the lithium-ion battery are improved.

[0110] The type and weight percentage D of the lithium salt additive generally affect the high-temperature cycling and storage performance of lithium-ion batteries. As can be seen from Examples 2-8 to 2-14, when the type and weight percentage D of the lithium salt additive are within the ranges of this application, the lithium-ion battery exhibits a high cycle capacity retention rate and a low thickness expansion rate, indicating that the high-temperature cycling and storage performance of the lithium-ion battery are improved.

[0111] Different types and contents of additives and lithium salt additives generally affect the high-temperature cycling and storage performance of lithium-ion batteries. Examples 2-15 to 2-17 show that when the first additive and lithium salt additive within the scope of this application are used in combination, the cycle capacity retention rate of the lithium-ion battery is further improved and the thickness expansion rate is further reduced, indicating that the lithium-ion battery has good high-temperature cycling and storage performance.

[0112] The terms "comprises," "comprising," or any other variations thereof are intended to cover a non-exclusive inclusion such that a process, method, or article that comprises a list of elements includes not only those elements but also other elements not expressly listed or inherent to such process, method, or article.

[0113] Each embodiment in this specification is described in a related manner. The same or similar parts between the embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0114] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. An electrochemical device comprising an electrolyte and a positive electrode plate, wherein the electrolyte comprises a compound of formula I, and the mass percentage A of the compound of formula I is 0.01% to 7% based on the total mass of the electrolyte; in, R1, R2, R3, R4 are each independently selected from C=O or C-R6, at least one of R1, R2, R3 or R4 is selected from C=O; R5 is selected from hydrogen atom, C1 to C 10 Alkyl, C2 to C 10 alkenyl, C2 to C 10 Alkynyl or C6 to C 12 R6 is selected from hydrogen atom, C1 to C 10 Alkyl or C6 to C 12 aromatic groups; The positive electrode plate includes a positive electrode active material layer, the positive electrode active material layer includes nickel element, and based on the total mass of the positive electrode active material layer, the mass percentage of the nickel element is B, and 0.1≤100A / B≤17.

5.

2. The electrochemical device according to claim 1, wherein The mass percentage A of the compound of formula I is 0.1% to 5%.

3. The electrochemical device according to claim 1, wherein 0.2≤100A / B≤12.

5.

4. The electrochemical device according to claim 1, wherein The positive electrode active material layer includes lithium nickel cobalt manganese oxide. Based on the total mass of the positive electrode active material layer, the mass percentage E of cobalt element in the lithium nickel cobalt manganese oxide is 2.5% to 20%, and 2≤B / E≤18.

5. The electrochemical device according to claim 1, wherein Based on the total mass of the positive electrode active material layer, the mass percentage B of the nickel element is 28% to 60.2%.

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

7. The electrochemical device according to any one of claims 1 to 6, wherein The electrolyte includes a first additive, which includes at least one of fluoroethylene carbonate, vinylene carbonate, vinyl sulfate or 1,3-propane sultone; based on the total mass of the electrolyte, the mass percentage C of the first additive is 0.01% to 15%.

8. The electrochemical device according to claim 7, wherein Based on the total mass of the electrolyte, the mass percentage C of the first additive is 0.5% to 5%.

9. The electrochemical device according to any one of claims 1 to 6, wherein The electrolyte includes a lithium salt additive, which includes at least one of lithium difluorophosphate, lithium tetrafluoroborate, lithium trifluoromethanesulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium bisoxalatoborate or lithium difluorooxalatoborate; based on the total mass of the electrolyte, the mass percentage D of the lithium salt additive is 0.01% to 5%.

10. The electrochemical device according to claim 9, wherein Based on the total mass of the electrolyte, the mass percentage D of the lithium salt additive is 0.2% to 2%. 11 . An electronic device comprising the electrochemical device according to claim 1 .

Images