Electrochemical apparatus and electronic device

Abstract

The present application discloses an electrochemical apparatus and an electronic device. An electrolyte of the electrochemical apparatus comprises the compound of formula (I). A positive electrode active material of a positive electrode sheet comprises Mn and Ni. By means of a combination of the compound of formula I in the electrolyte and the metal elements Mn and Ni in the positive electrode active material, and choosing to make the content A of the compound of formula I and the content C of the metal elements Mn and Ni satisfy the conditional expressions 0.1≤A*C / 1000≤40 and 500 ppm≤C≤5000 ppm, not only can the initial impedance of the electrochemical apparatus be improved, but the impedance growth rate of the electrochemical apparatus during high-temperature charging-discharging cycles can also be improved.

Description

Electrochemical devices and electronic equipment Technical Field

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

[0002] With the rapid development of electronic products such as smartphones, tablets, and smart wearables, higher demands are being placed on the lifespan and safety performance of electrochemical devices, taking into account the varying usage times and operating temperatures of these products. In related technologies, the negative electrode interface of electrochemical devices sometimes experiences the dissolution of transition metals from the positive electrode and their deposition at the negative electrode interface. This results in poor stability of the negative electrode interface, leading to decreased high-temperature charge-discharge cycle performance and increased impedance of the electrochemical device.

[0003] Summary of the Invention

[0004] This application provides an electrochemical device and an electronic device that can improve the problem of poor stability of the negative electrode interface of the electrochemical device, thereby reducing the initial impedance of the electrochemical device and the impedance growth rate during high-temperature charge-discharge cycles.

[0005] In a first aspect, embodiments of this application provide an electrochemical device, including a positive electrode and an electrolyte;

[0006] The electrolyte comprises a compound of formula I:

[0007] Wherein, R is selected from unsubstituted or R0-substituted C2-C6 alkyl, unsubstituted or R0-substituted C2-C6 alkenyl, unsubstituted or R0-substituted C2-C6 alkynyl, and unsubstituted or R0-substituted C5-C6 alkyl. 12 Nitrogen-containing heteroaryl groups, unsubstituted or R0-substituted C6-C 12 Any of the aryl groups, wherein the substituent R0 of each group is independently selected from any of the unsubstituted or substituted C1-C6 alkyl groups, and when substituted, the substituent is fluorine;

[0008] Based on the total mass of the electrolyte, the mass percentage of compound I is A;

[0009] The positive electrode includes a positive electrode active material, which includes a metal element M, specifically Mn and Ni. Based on the mass of the positive electrode active material, the total doping amount of the metal element M is C, where 0.1 ≤ A*C / 1000 ≤ 40, and 500ppm ≤ C ≤ 5000ppm. By controlling the electrolyte to include a compound of formula I, and the metal element M of the positive electrode active material to include Mn and Ni, the mass percentages of the compound of formula I and the metal element M are within the range of this application. This not only improves the initial impedance of the electrochemical device but also improves the impedance growth rate during high-temperature charge-discharge cycles.

[0010] In some embodiments, the electrochemical device satisfies at least one of the following conditions:

[0011] (1) 1 ≤ A*C / 1000 ≤ 13;

[0012] (2) 1000ppm≤C≤3000ppm.

[0013] In some embodiments, based on the mass of the positive electrode active material, the Ni doping amount is C1, with 500ppm ≤ C1 ≤ 1500ppm. By selecting the Ni doping amount within the above range, the initial impedance of the electrochemical device can be effectively improved, and the contents of Mn and Ni can be easily controlled within appropriate ranges to improve the high-temperature charge-discharge cycle performance and impedance growth rate during the high-temperature charge-discharge cycle process of the electrochemical device.

[0014] In some embodiments, 0.1% ≤ A ≤ 10%.

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

[0016] By selecting the above-mentioned Formula I compound, a protective layer can be formed at the negative electrode interface, thereby improving the stability of the negative electrode interface, inhibiting the reduction of metal ions on the negative electrode and the catalytic effect of side reactions, and thus improving the ion channel to improve the impedance growth rate of the electrochemical device cycle process.

[0017] In some embodiments, the particle size Dv of the positive electrode active material 50 Satisfy: 3μm≤Dv 50 ≤30μm. The particle size Dv of the positive electrode active material is selected. 50Meeting the above range ensures that the particle size of the positive electrode active material is appropriate, which helps to shorten the impedance of ion transport and thus helps to reduce the initial impedance. In addition, it also helps the positive electrode active material to have a suitable specific surface area so that the metal dissolution rate of the positive electrode active material is appropriate. This allows it to cooperate with the compound of formula I to inhibit the dissolved metal from reaching the negative electrode and being reduced, thereby improving the stability of the negative electrode interface.

[0018] In some embodiments, the electrolyte further includes propylene carbonate, and the mass percentage of propylene carbonate is E based on the total mass of the electrolyte, where E satisfies: 0.1% ≤ E ≤ 10%. By selecting the content of propylene carbonate within the above range, propylene carbonate can effectively dissociate lithium salts, improve the low-temperature kinetic performance of the electrochemical device, and, since it is present at the negative electrode interface, can compensate for the negative electrode interface not covered by the passivation layer, reducing the probability of negative electrode interface exposure, thereby reducing the contact area between metal ions and the negative electrode interface and protecting the negative electrode sheet. Propylene carbonate can also work with the compound of Formula I to stabilize the passivation layer, thereby improving the impedance increase on the negative electrode side caused by the continuous side reactions of dissolved metal ions.

[0019] In some embodiments, the electrolyte further includes 1,3,6-hexanetrionitrile, and the mass percentage of the 1,3,6-hexanetrionitrile is H based on the total mass of the electrolyte, wherein H satisfies: 2% ≤ H ≤ 4.5%.

[0020] In some embodiments, the electrolyte further includes a dinitrile compound, which includes at least one of succinic anionyl nitrile and adiponitrile; based on the total mass of the electrolyte, the mass percentage of the dinitrile compound is Q, where Q satisfies: 1.5% ≤ Q ≤ 3.0%. By selecting the mass percentages of 1,3,6-hexanetrionitrile and the dinitrile compound within the above range, they can be used to complex with metal ions, inhibiting the dissolution of metal ions from the positive electrode, thereby reducing the impact of the dissolved metal ions on the negative electrode interface.

[0021] In some embodiments, the electrolyte further includes diethyl difluoromethylphosphonate, and the mass percentage of diethyl difluoromethylphosphonate is D based on the total mass of the electrolyte, where D satisfies: 0.1% ≤ D ≤ 0.5%. By selecting the content of diethyl difluoromethylphosphonate within the above range, diethyl difluoromethylphosphonate, based on the positive electrode interface film-forming protection mechanism, can further improve the impedance growth rate during the cycling process of the electrochemical device, and can further achieve the effects of balancing the initial impedance and suppressing the impedance growth during the charge-discharge cycle of the electrochemical device.

[0022] Secondly, this application provides an electronic device including the electrochemical device described above.

[0023] Based on the electrochemical device and electronic device embodiments of this application, the positive electrode active material of the positive electrode of the electrochemical device includes the metal elements Mn and Ni, which is beneficial to reducing the positive electrode impedance, thereby enabling the electrochemical device to have a lower initial impedance. By using a compound of formula I in the electrolyte, a passivation layer can be formed at the negative electrode interface. This passivation layer cuts off the electron pathway, inhibiting the reduction of the metal elements Mn and Ni at the negative electrode and the resulting side reactions. Therefore, during charge and discharge, not only can the negative electrode interface have good stability, but the impedance growth rate during high-temperature charge and discharge cycles of the electrochemical device can also be improved. Detailed Implementation

[0024] The technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only 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.

[0025] This application provides an electrochemical device comprising a positive electrode, a negative electrode, and an electrolyte as described below. By selecting an electrolyte containing a compound of formula I and a positive electrode active material containing the metal elements Mn and Ni, not only can the initial impedance of the electrochemical device be improved, but also the impedance growth rate during the high-temperature charge-discharge cycle of the electrochemical device can be improved.

[0026] The electrolyte of this application includes a compound of formula I:

[0027] Wherein, R is selected from unsubstituted or R0-substituted C2-C6 alkyl, unsubstituted or R0-substituted C2-C6 alkenyl, unsubstituted or R0-substituted C2-C6 alkynyl, and unsubstituted or R0-substituted C5-C6 alkyl. 12 Nitrogen-containing heteroaryl groups, unsubstituted or R0-substituted C6-C 12 Any of the aryl groups, wherein the substituent R0 of each group is independently selected from any of the unsubstituted or substituted C1-C6 alkyl groups, and when substituted, the substituent is fluorine.

[0028] The positive electrode in this electrochemical device includes a positive current collector and a positive electrode material layer disposed on the surface of the positive current collector. The positive electrode material layer includes a positive electrode active material, which is any substance capable of reversibly inserting and deintercalating lithium ions. The positive electrode active material includes a metal element M, which includes Mn and Ni.

[0029] Based on the total mass of the electrolyte, the mass percentage of compound I is A, and based on the mass of the positive electrode active material, the total doping amount of metal element M is C, where 0.1 ≤ A*C / 1000 ≤ 40. For example, A*C / 1000 can be 0.1, 2.0, 10.5, 22.0, 28.5, 30.5, 33.3, 35.8, 40.0, or a range of any two of these values. C satisfies 500ppm ≤ C ≤ 5000ppm, for example, C can be 500ppm, 600ppm, 800ppm, 1000ppm, 1500ppm, 3000ppm, 5000ppm, or a range of any two of these values.

[0030] The positive electrode active materials of electrochemical devices include Mn and Ni, which helps reduce the positive electrode impedance, thus giving the electrochemical device a lower initial impedance. However, if Mn and Ni dissolve and migrate to the negative electrode and are reduced, they will create an electronic pathway, inducing further interfacial side reactions on the negative electrode. These byproducts will hinder ion channels, thereby worsening the impedance growth rate during charge-discharge cycles. By adding a compound of formula I to the electrolyte, this compound can form a lithium-containing inorganic compound passivation layer rich in S and F at the negative electrode interface, improving interfacial stability. This passivation layer also cuts off electronic pathways, inhibiting the reduction of metal ions and the resulting side reactions. Therefore, during charge-discharge, the protection provided by the compound of formula I not only ensures good stability at the negative electrode interface but also inhibits the reduction of metal ions on the negative electrode, effectively reducing the impedance growth rate during charge-discharge cycles. By selecting the mass percentage of compound I and the doping amount of metal element M to satisfy the above conditions, it is easy to control the contents of Mn and Ni within a suitable range relative to the mass percentage of compound I, thereby improving the initial impedance of the electrochemical device and the impedance growth rate during high-temperature charge-discharge cycles. When A*C / 1000 exceeds the upper limit of 40, the content of compound I is too high, the passivation layer formed at the negative electrode interface is too thick, and the ionic conductivity decreases, which will lead to a deterioration of the impedance growth rate during the charge-discharge cycle of the electrochemical device. Alternatively, excessive dissolution of Mn and Ni will worsen the negative electrode impedance. When A*C / 1000 is below the lower limit of 0.1, it is difficult to achieve the effect of improving the initial impedance of the electrochemical device and the impedance growth during high-temperature charge-discharge cycles.

[0031] In some embodiments, the Ni doping amount is C1, based on the mass of the positive electrode active material, where 500ppm ≤ C1 ≤ 1500ppm. For example, C1 can be 500ppm, 600ppm, 700ppm, 800ppm, 1000ppm, 1200ppm, 1500ppm, or a range of any two of these values. By selecting the Ni doping amount within the above range, the initial impedance of the electrochemical device can be effectively improved, and the contents of Mn and Ni can be easily controlled within appropriate ranges to improve the high-temperature charge-discharge cycle performance and impedance growth rate during the high-temperature charge-discharge cycle process of the electrochemical device.

[0032] In some embodiments, A satisfies: 0.1% ≤ A ≤ 10%. For example, A can be 0.1%, 0.5%, 1.5%, 3.0%, 5.5%, 65%, 8.5%, 10.0%, or a range consisting of any two of these values. By selecting the content A of compound I within the above range, the thickness of the passivation layer formed by compound I at the negative electrode interface is appropriate, which can effectively improve the stability of the negative electrode interface, while also improving the ionic conductivity and impedance of the negative electrode interface, further improving the stability of the negative electrode interface while achieving a small increase in the impedance on the negative electrode side.

[0033] In some embodiments, the compound represented by Formula I includes at least one of the following compounds:

[0034] Propylene carbonate has a low freezing point and good dissociation properties for lithium salts, which can improve the low-temperature kinetic performance of electrochemical devices. Based on this, in some embodiments, propylene carbonate can be added to the electrolyte, with the mass percentage of propylene carbonate, E, being 0.1% ≤ E ≤ 10% based on the total mass of the electrolyte. For example, E can be 0.1%, 0.5%, 1.0%, 3.5%, 5.0%, 7.5%, 8.0%, 10%, or a range of any two of these values. By selecting the mass percentage E of propylene carbonate within the above range, propylene carbonate can effectively exert its dissociation effect on lithium salts, improving the low-temperature kinetic performance of the electrochemical device. Simultaneously, the presence of propylene carbonate at the negative electrode interface can compensate for any areas not covered by the passivation layer, reducing the probability of negative electrode interface exposure and thus reducing the contact area between metal ions and the negative electrode interface, effectively protecting the negative electrode. Propylene carbonate can also work with compounds of formula I to stabilize the passivation layer, thereby improving the impedance increase on the negative electrode side caused by the continuous side reactions of dissolved metal ions.

[0035] In some embodiments, the electrolyte further includes 1,3,6-hexanetrionitrile, wherein the mass percentage of 1,3,6-hexanetrionitrile is H based on the total mass of the electrolyte, and H satisfies: 2% ≤ H ≤ 4.5%. For example, H can be 2%, 2.3%, 2.5%, 2.6%, 2.9%, 3.2%, 3.8%, 4.2%, 4.5%, or a range of any two of these values.

[0036] In some embodiments, the electrolyte further includes a dinitrile compound, which includes at least one selected from succinic anhydride and adiponitrile. Based on the total mass of the electrolyte, the mass percentage of the dinitrile compound is Q, where 1.5% ≤ Q ≤ 3.0%. For example, Q can be 1.5%, 1.6%, 1.7%, 1.8%, 2.0%, 2.2%, 2.5%, 2.8%, 3.0%, or a range of any two of these values. In the embodiments of this application, 1,3,6-hexanetrionitrile and the dinitrile compound can complex with metal ions, inhibiting the dissolution of metal ions from the positive electrode, thereby reducing the impact of the dissolved metal ions on the negative electrode interface. Among them, the trinitrile compound and the dinitrile compound, as nitrile compounds, can suppress the dissolution of Ni and Mn on the positive electrode side based on the complexation mechanism. At the same time, the compound of formula I forms a passivation layer on the negative electrode side to cut off the electron pathway, and together suppress the reduction of Ni and Mn metal ions on the negative electrode side. Therefore, the compound of formula I can work synergistically with at least one of the trinitrile compound and the dinitrile compound to improve the stability of the negative electrode interface of the electrochemical device and suppress the increase of impedance during the charge and discharge cycle of the electrochemical device.

[0037] In some embodiments, the electrolyte further includes diethyl difluoromethylphosphonate, and the mass percentage of diethyl difluoromethylphosphonate is D, based on the total mass of the electrolyte, where 0.1% ≤ D ≤ 0.5%. For example, D can be 0.1%, 0.20%, 0.33%, 0.38%, 0.1%, 0.41%, 0.45%, 0.50%, or a range of any two of these values. By selecting the content D of diethyl difluoromethylphosphonate within the above range, diethyl difluoromethylphosphonate, based on the positive electrode interface film-forming protection mechanism, can further improve the impedance growth rate during the cycling process of the electrochemical device, and can further achieve the effects of balancing the initial impedance and suppressing the impedance growth during the charge-discharge cycle of the electrochemical device.

[0038] In this application, the characteristics of the different components contained in the electrolyte can be combined, and the implementation methods covered by the above combinations are all within the protection scope of this application.

[0039] In this application, the electrolyte also includes a non-aqueous organic solvent. This application does not impose any particular limitation on the non-aqueous organic solvent, as long as it achieves the purpose of this application. For example, the non-aqueous organic solvent may contain at least one of carbonate compounds, carboxylic acid ester compounds, ether compounds, or other organic solvents. The aforementioned carbonate compounds may include, but are not limited to, at least one of chain carbonate compounds and cyclic carbonate compounds. The aforementioned chain carbonate compounds may include, but are not limited to, at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), or methyl ethyl carbonate (EMC). The aforementioned cyclic carbonate compounds may include, but are not limited to, at least one of ethylene carbonate (EC), butyl carbonate (BC), or vinyl ethylene carbonate (VEC). The aforementioned carboxylic acid ester compounds may include, but are not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, or propyl propionate. The aforementioned ether compounds may include, but are not limited to, at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. The other organic solvents mentioned above may include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, or phosphate esters. This application does not impose any particular limitation on the mass percentage of non-aqueous organic solvents in the electrolyte, as long as the purpose of this application is achieved. For example, based on the total mass of the electrolyte, the mass percentage of non-aqueous organic solvents may be from 10% to 70%.

[0040] The preparation method of the electrolyte for the electrochemical device in this application is not particularly limited, and any method used in the art to prepare the electrolyte is applicable to this application.

[0041] In the electrochemical device of this application, the positive electrode material layer is disposed on at least one surface of the positive electrode current collector. The phrase "the positive electrode material layer is disposed on at least one surface of the positive electrode current collector" means that the positive electrode material layer can be disposed on one surface of the positive electrode current collector along its own thickness direction, or on two surfaces of the positive electrode current collector along its own thickness direction. It should be noted that the "surface" here can be the entire area of ​​the positive electrode current collector, or a portion of it; this application has no particular limitation, as long as the purpose of this application is achieved.

[0042] The positive electrode material layer of this application includes a positive electrode active material. In some embodiments, the particle size Dv of the positive electrode active material is... 50 Satisfy: 3μm≤Dv 50 ≤30μm, for example, Dv50 The particle size Dv can be 3μm, 8μm, 13μm, 18μm, 25μm, 28μm, 30μm, or any combination of two of these values. The particle size Dv of the positive electrode active material is selected by... 50 Meeting the above range ensures that the particle size of the positive electrode active material is appropriate, which helps to shorten the impedance of ion transport and thus helps to reduce the initial impedance. In addition, it also helps the positive electrode active material to have a suitable specific surface area so that the metal dissolution rate of the positive electrode active material is appropriate. This allows it to cooperate with the compound of formula I to inhibit the dissolved metal from reaching the negative electrode and being reduced, thereby improving the stability of the negative electrode interface.

[0043] The positive electrode active material of this application embodiment may include at least one of lithium cobalt oxide, lithium iron phosphate, and lithium titanate, and the metal element M (Mn and Ni) is doped into the above material.

[0044] The positive electrode material layer of this application also includes a conductive agent and a binder. This application does not impose any particular limitations on the conductive agent and binder in the positive electrode material layer, as long as they can 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, carbon nanotubes (CNTs), carbon fibers, flake graphite, graphene, metallic materials, or conductive polymers. The aforementioned conductive carbon black may include, but is not limited to, Super P, acetylene black, or Ketjen black. 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 polyacrylate, polyimide, polyamide, polyamide-imide, polyvinylidene fluoride, polystyrene-butadiene copolymer (styrene-butadiene rubber, SBR), sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethyl cellulose (CMC-Na), potassium carboxymethyl cellulose, sodium carboxymethyl cellulose, or potassium carboxymethyl cellulose. This application does not impose any particular limitation on the mass ratio of the positive electrode active material, conductive agent, and binder in the positive electrode material layer; those skilled in the art can select according to actual needs, as long as the purpose of this application is achieved.

[0045] This application does not impose any particular limitation on the positive electrode current collector, as long as it achieves the purpose of this application. For example, it may include aluminum foil, aluminum alloy foil, or composite current collectors (such as aluminum-carbon composite current collectors). This application does not impose any particular limitation on the thickness of the positive electrode current collector, as long as it achieves the purpose of this application. For example, the thickness of the positive electrode current collector is 5 μm to 20 μm, preferably 6 μm to 18 μm. This application does not impose any particular limitation on the thickness of the positive electrode material layer, as long as it achieves the purpose of this application. For example, the thickness of a single-sided positive electrode material layer is 30 μm to 120 μm.

[0046] Optionally, the positive electrode may further include a conductive layer, which is located between the positive electrode current collector and the positive electrode material layer. This application does not impose any particular limitation on the composition of the conductive layer, and it can be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. This application does not impose any particular limitation on the conductive agent and binder in the conductive layer, and it can be at least one of the aforementioned conductive agents and binders. This application does not impose any particular limitation on the mass ratio of the conductive agent and binder in the conductive layer; those skilled in the art can choose according to actual needs, as long as the purpose of this application can be achieved.

[0047] 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 aforementioned "negative electrode material layer 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 "surface" here can be the entire area of ​​the negative electrode current collector or only a portion thereof; this application does not have any particular limitation, as long as the purpose of this application is achieved.

[0048] The negative electrode material layer of this application 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 natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composites, SiO₂, etc. x (0.5 < x < 1.6), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel-structured lithium titanate Li4Ti5O 12 At least one of Li-Al alloys or metallic lithium.

[0049] The negative electrode material layer of this application also includes a binder. This application does not impose any particular limitation on the binder in the negative electrode material layer, as long as it achieves the purpose of this application. For example, the binder can be at least one of the binders described above. The negative electrode material layer of this application also includes a conductive agent. This application does not impose any particular limitation on the conductive agent in the negative electrode material layer, as long as it achieves the purpose of this application. For example, the conductive agent can be at least one of the conductive agents described above. This application does not impose any particular limitation on the mass ratio of the negative electrode active material, binder, and conductive agent in the negative electrode material layer. Those skilled in the art can choose according to actual needs, as long as the purpose of this application is achieved.

[0050] This application does not impose any particular limitation on the negative electrode current collector, as long as it achieves 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 collectors. This application does not impose any particular limitation on the thickness of the negative electrode current collector, as long as it achieves the purpose of this application. For example, the thickness of the negative electrode current collector may be 5 μm to 16 μm. This application does not impose any particular limitation on the thickness of the negative electrode material layer, as long as it achieves the purpose of this application. For example, the thickness of a single-sided negative electrode material layer may be 30 μm to 120 μm.

[0051] Optionally, the negative electrode may further include a conductive layer, which is located between the negative electrode current collector and the negative electrode material layer. This application does not impose any particular limitation on the composition of the conductive layer, and it can be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. This application does not impose any particular limitation on the conductive agent and binder in the conductive layer, and it can be at least one of the aforementioned conductive agents and binders. This application does not impose any particular limitation on the mass ratio of the conductive agent to the binder in the conductive layer; those skilled in the art can choose according to actual needs, as long as the purpose of this application is achieved. This application does not impose any particular limitation on the thickness of the conductive layer, as long as the purpose of this application is achieved; for example, the thickness of the conductive layer is 1 μm to 10 μm.

[0052] In this application, the electrochemical device also includes a diaphragm, which separates the positive and negative electrodes, prevents short circuits within the electrochemical device, allows electrolyte ions to pass freely, and does not affect the electrochemical charging and discharging process. 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 diaphragm type may include at least one of woven membrane, nonwoven membrane, microporous membrane, composite membrane, rolled membrane, or spun membrane.

[0053] In this application, the diaphragm may include a substrate and a surface treatment layer. The substrate may be a nonwoven fabric or composite membrane with a porous structure, and the material of the substrate 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. Optionally, a surface treatment layer is provided on at least one surface of the substrate. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing polymers and inorganic materials. For example, the inorganic layer includes inorganic particles and a binder. This application does not have any particular limitation on the aforementioned inorganic particles, and may 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, or barium sulfate. This application does not have any particular limitation on the aforementioned binders, and may include at least one of the aforementioned binders. The polymer layer contains a polymer, the polymer material of which includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, or poly(vinylidene fluoride-hexafluoropropylene).

[0054] The electrochemical device of this application also includes a packaging bag for containing the positive electrode, diaphragm, negative electrode, and electrolyte, as well as other components known in the art in the electrochemical device. This application does not limit the aforementioned other components. This application does not have any particular limitation on the packaging bag; it can be any packaging bag known in the art, as long as it can achieve the purpose of this application.

[0055] This application does not impose any particular limitation on the type of electrochemical device, which may include any device in which an electrochemical reaction occurs. In this application, the electrochemical device may include, but is not limited to: lithium metal electrochemical device, lithium-ion electrochemical device (lithium-ion battery), lithium polymer electrochemical device, or lithium-ion polymer electrochemical device (lithium-ion polymer battery), etc.

[0056] The preparation process of the electrochemical device of this application is well known to those skilled in the art, and this application has no 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 in a packaging bag; injecting electrolyte into the packaging bag and sealing it to obtain the electrochemical device; or 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 in a packaging bag; injecting electrolyte into the packaging bag and sealing it to obtain the electrochemical device. In addition, overcurrent protection elements, conductive plates, etc., may be placed in the packaging bag as needed to prevent pressure rise and overcharging / discharging inside the electrochemical device.

[0057] This application also provides an electronic device that includes the electrochemical device in any of the foregoing embodiments. Therefore, the electronic device provided by this application has good performance.

[0058] This application does not specifically limit the type of electronic device, which 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.

[0059] The preparation of the electrochemical device is described below with reference to specific embodiments. Those skilled in the art will understand that the preparation methods described in this application are merely examples, and any other suitable preparation methods are within the scope of this application.

[0060] Example

[0061] The following examples, using lithium-ion batteries as an example, provide more specific illustrations of the implementation methods of the electrochemical device of this application. Those skilled in the art will understand that the preparation methods described in this application are merely examples, and any other suitable preparation methods are within the scope of this application. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" refer to mass measurements.

[0062] Impedance Testing Methods

[0063] (1) Place the battery with 20% SOC at 25℃±3℃ for 2 hours, and then use an OCV / IMP voltage internal resistance tester to record the AC impedance of the battery at 1KHz, which is recorded as the initial impedance in mΩ.

[0064] (2) After testing the initial impedance, place the lithium-ion battery in a 40°C environment, charge the lithium-ion battery at a constant current of 0.5C to 4.5V, then charge it at a constant voltage of 4.5V to 0.05C, and then discharge it at a constant current of 0.2C to 3.0V. This is one charge-discharge cycle. Perform 500 charge-discharge cycles on the lithium-ion battery according to the above method. After the cycle is completed, place the lithium-ion battery at 25°C±3°C for 2 hours, and then use an OCV / IMP voltage internal resistance tester to record the AC impedance of the battery at 1KHz. This impedance is recorded as the impedance after 500cls of cycling at 40°C, in mΩ.

[0065] (3) Impedance growth rate during 500cls of charge-discharge cycle at 40℃

[0066] The impedance growth rate after 500cls of charge-discharge cycles at 40℃ = (impedance after 500cls of charge-discharge cycles at 40℃ - initial impedance) / initial impedance * 100%.

[0067] Example 1-1

[0068] (1) Preparation of positive electrode sheet

[0069] Lithium cobalt oxide (LiCoO2) as the positive electrode active material, conductive carbon black as the conductive agent, and polyvinylidene fluoride (PVDF) as the binder were mixed at a mass ratio of 97.9:0.9:1.2. N-methylpyrrolidone (NMP) was added as a solvent, and the mixture was stirred evenly under vacuum to obtain a positive electrode slurry with a solid content of 75 wt%. The positive electrode slurry was uniformly coated onto one surface of a 9 μm thick aluminum foil used as a positive electrode current collector. The foil was then dried at 85°C and cold-pressed to obtain a positive electrode sheet with a single-sided coating thickness of 95 μm. The above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided coating. After cutting and welding positive electrode tabs, a positive electrode sheet with dimensions of 74 mm × 851 mm was obtained for use. The compaction density of the positive electrode material layer was 4.20 g / cm³. 3 .

[0070] Among them, metal element M is incorporated into lithium cobalt oxide (LiCoO2). The doping types and doping amounts of metal element M in the positive electrode active material are shown in Table 1.

[0071] (2) Preparation of negative electrode sheet

[0072] Artificial graphite (negative electrode active material), styrene-butadiene rubber (SBR) binder, and sodium carboxymethyl cellulose (CMC) thickener were mixed at a mass ratio of 97.4:1.4:1.2. Deionized water was then added as a solvent, and the mixture was stirred evenly under vacuum to obtain a negative electrode slurry with a solid content of 50 wt%. This negative electrode slurry was uniformly coated onto one surface of a 10 μm thick copper foil current collector. The foil was then dried at 85°C and cold-pressed to obtain a negative electrode sheet with a single-sided coating thickness of 130 μm. The above steps were repeated on the other surface of the same copper foil to obtain a negative electrode sheet with a double-sided coating. After cutting and welding of the negative electrode nickel tabs, a negative electrode sheet with dimensions of 76 mm × 867 mm was obtained for later use. The compaction density of the negative electrode material layer was 1.80 g / cm³. 3 .

[0073] (3) Preparation of the separating membrane

[0074] A porous polyethylene (PE) membrane with a thickness of 5 μm was used.

[0075] (4) Preparation of electrolyte

[0076] In an argon-atmospheric glove box with a water content of less than 10 ppm, ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) were mixed in a mass ratio of 1:1:1 to obtain a base solvent. Then, compound I and lithium hexafluorophosphate (LiPF6) were dissolved in the base solvent to obtain the electrolyte. The mass percentage of LiPF6 was 12.5% ​​based on the total mass of the electrolyte.

[0077] The mass percentages of compounds of Formula I are shown in Table 1, with the remainder being the base solvent.

[0078] (5) Assembly of lithium-ion batteries

[0079] The separator, positive electrode, separator, and negative electrode prepared above are stacked and wound in sequence to obtain a wound electrode assembly. The electrode assembly is placed in an aluminum-plastic film packaging bag, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, capacity testing, degassing, and edge trimming, a lithium-ion battery is obtained.

[0080] Examples 1-2 to 19 are identical to Example 1-1, except that the type and content A of compound I in the preparation of the electrolyte are adjusted according to Table 1, and the content C of metal element M in the preparation of the positive electrode is adjusted according to Table 1. The mass percentage of the base solvent is changed accordingly, while the mass percentage of the lithium salt remains unchanged.

[0081] Examples 1-20 to 1-21 are the same as in Example 1-1, except that the content of metal element Ni C1 is adjusted according to Table 1 in the preparation of the positive electrode sheet.

[0082] Examples 1-22 to 1-24 are the same as in Example 1-1, except that the particle size Dv50 of the positive electrode active material is adjusted as shown in Table 1 during the preparation of the positive electrode sheet.

[0083] Comparative Example 1-1 was identical to Examples 1-7 except that no compound of Formula I was added to the electrolyte. The mass percentage of the base solvent was changed accordingly, while the mass percentage of the lithium salt remained unchanged.

[0084] Comparative Examples 1 and 2 are the same as in Example 17, except that the positive electrode active material does not contain the metal element M.

[0085] Comparative Examples 1-3 to 1-6 were identical to Examples 1-1, except that the content A of compound I in the electrolyte preparation was adjusted according to Table 1, and the content C of metal element M in the positive electrode preparation was adjusted according to Table 1. The mass percentage of the base solvent was changed accordingly, while the mass percentage of the lithium salt remained unchanged.

[0086] Examples 2-1 to 2-7 are identical to Examples 1-7, except that a dinitrile compound is added during the preparation of the electrolyte as shown in Table 2. The mass percentage of the base solvent is varied, while the mass percentage of the lithium salt remains unchanged.

[0087] Examples 3-1 to 3-8 are identical to Examples 1-7, except that propylene carbonate is added to the electrolyte as shown in Table 3. The mass percentage of the base solvent is varied, while the mass percentage of the lithium salt remains unchanged.

[0088] Examples 4-1 to 4-5 are identical to Examples 1-7, except that 1,3,6-hexanetrionitrile is added to the electrolyte as shown in Table 4. The mass percentage of the base solvent is varied, while the mass percentage of the lithium salt remains unchanged.

[0089] Examples 4-6 and 4-7 are identical to Examples 1-7, except that 1,3,6-hexanetrionitrile and butadionitrile are added to the electrolyte as shown in Table 4. The mass percentage of the base solvent is varied, while the mass percentage of the lithium salt remains unchanged.

[0090] Examples 4-8 and 4-9 are identical to Examples 1-7, except that 1,3,6-hexanetrionitrile and propylene carbonate are added to the electrolyte as shown in Table 4. The mass percentage of the base solvent is varied, while the mass percentage of the lithium salt remains unchanged.

[0091] Examples 4-10 and 4-11 are identical to Examples 1-7, except that 1,3,6-hexanetrionitrile, propylene carbonate, and succinic anionylene are added to the electrolyte as shown in Table 4. The mass percentage of the base solvent is varied, while the mass percentage of the lithium salt remains unchanged.

[0092] Examples 5-1 to 5-6 are identical to Examples 1-7, except that diethyl difluoromethylphosphonate is added to the electrolyte as shown in Table 5. The mass percentage of the base solvent is varied, while the mass percentage of the lithium salt remains unchanged.

[0093] Examples 5-7 are identical to Examples 1-7, except that 1,3,6-hexanetrionitrile and diethyl difluoromethylphosphonate are added to the electrolyte as shown in Table 5. The mass percentage of the base solvent is changed accordingly, while the mass percentage of the lithium salt remains unchanged.

[0094] Examples 5-8 are identical to Examples 1-7, except that propylene carbonate and diethyl difluoromethylphosphonate are added to the electrolyte as shown in Table 5. The mass percentage of the base solvent is varied, while the mass percentage of the lithium salt remains unchanged.

[0095] Examples 5-9 are identical to Examples 1-7, except that 1,3,6-hexanetrionitrile, propylene carbonate, and diethyl difluoromethylphosphonate are added to the electrolyte as shown in Table 5. The mass percentage of the base solvent is varied, while the mass percentage of the lithium salt remains unchanged.

[0096] Examples 5-10 are identical to Examples 1-7, except that the preparation of the electrolyte also includes a dinitrile compound, 1,3,6-hexanetrionitrile, propylene carbonate, and diethyl difluoromethylphosphonate as shown in Table 5. The mass percentage of the base solvent is varied, while the mass percentage of the lithium salt remains unchanged.

[0097] The preparation parameters and performance parameters of Examples 1-1 to 1-24 and Comparative Examples 1-1 to 1-4 are shown in Table 1.

[0098] Table 1 Note: " / " in Table 1 indicates that there is no corresponding parameter.

[0099] As can be seen from Examples 1-1 to 1-11 and Comparative Examples 1-1 to 1-6, the lithium-ion batteries of this application, by adding a compound of Formula I to the electrolyte and the metal element M of the positive electrode active material including Mn and Ni, and the mass percentage A of the compound of Formula I and the doping content C of the metal element M satisfying the conditions 0.1≤A*C / 1000≤40 and 500ppm≤C≤5000ppm, have lower initial impedance and impedance after 500cls of charge-discharge cycle at 40°C. This indicates that the compound of Formula I and the metal element M have a good effect on improving the initial impedance and impedance after 500cls of charge-discharge cycle at 40°C of lithium-ion batteries. When A*C / 1000 exceeds the lower or upper limit, it becomes difficult to control the mass percentage A of compound I and the doping content C of metal element M within a suitable range. This can easily lead to a large initial impedance of the lithium-ion battery or a large impedance during 500cls of charge-discharge cycles at 40°C. For example, in Comparative Examples 1-3, if A*C / 1000 is too small, it has almost no effect on improving the initial impedance of the lithium-ion battery or the impedance during 500cls of charge-discharge cycles at 40°C. The initial impedance of the lithium-ion battery and the impedance during 500cls of charge-discharge cycles at 40°C are still large. In Comparative Examples 1-4, if A*C / 1000 is too large, it is easy for the content of compound I to be too high or for the dissolution of Mn and Ni to be too large, which will lead to a deterioration in the impedance of the lithium-ion battery during 500cls of charge-discharge cycles at 40°C.

[0100] As can be seen from Examples 1-7, 1-20 to 1-21, by selecting the Ni doping amount C1 to satisfy the condition 500ppm≤C1≤1500ppm, the initial impedance and the impedance of the lithium-ion battery after 500cls of charge-discharge cycle at 40℃ are both relatively small. This indicates that the Ni doping amount C1 meets the range of the above condition, which makes it easier to control the contents of Mn and Ni within appropriate ranges, effectively improving the initial impedance of the lithium-ion battery, as well as improving the 40℃ charge-discharge cycle performance and the impedance after 500cls of charge-discharge cycle at 40℃.

[0101] As can be seen from Examples 1-7 and Examples 1-22 to 1-24, the initial impedance and the impedance after 500 cls of charge-discharge cycling at 40°C are both relatively small, indicating that the particle size Dv of the positive electrode active material is relatively small. 50 The initial impedance and the impedance after 500 cls of charge-discharge cycles at 40℃ are affected by the particle size Dv50 of the positive electrode active material, which is ≤ 3 μm. 50 Within the range of ≤30μm, the smaller the particle size Dv50 of the positive electrode active material, the smaller the initial impedance of the lithium-ion battery. As the particle size Dv50 of the positive electrode active material gradually increases, the impedance improvement effect on the lithium-ion battery after 500cls of charge-discharge cycles at 40℃ is even better.

[0102] The preparation parameters and performance parameters of Examples 2-1 to 2-7 are shown in Table 2.

[0103] Table 2 Note: " / " in Table 2 indicates that there is no corresponding parameter.

[0104] Dinitrile compounds can complex with Mn and Ni, inhibiting the dissolution of Mn and Ni and reducing the side reactions that occur when Mn and Ni come into contact with the negative electrode. As can be seen from Examples 2-1 to 2-7 and Examples 1-7, the addition of dinitrile compounds to the electrolyte further reduces the impedance growth rate of lithium-ion batteries during 500cls of charge-discharge cycles at 40°C, indicating that nitrile compounds can further improve the impedance growth rate of lithium-ion batteries during 500cls of charge-discharge cycles at 40°C.

[0105] The preparation parameters and performance parameters of Examples 3-1 to 3-8 are shown in Table 3.

[0106] Table 3 Note: " / " in Table 3 indicates that there is no corresponding parameter.

[0107] Propylene carbonate can compensate for the negative electrode interface not covered by the passivation layer. Propylene carbonate and the compound of Formula I work together to form a stable passivation layer, thereby improving the impedance increase on the negative electrode side caused by the continuous side reactions of dissolved metal ions. As can be seen from Examples 1-7 and Examples 3-1 to 3-5, by adding propylene carbonate to the electrolyte, the impedance growth rate of the lithium-ion battery during a 500cls charge-discharge cycle at 40°C is further reduced, indicating that propylene carbonate can effectively improve the impedance growth rate of the lithium-ion battery during a 500cls charge-discharge cycle at 40°C.

[0108] As can be seen from Examples 3-6 to 3-8, the simultaneous addition of dinitrile compound and propylene carbonate to the electrolyte further reduces the impedance growth rate of lithium-ion battery during 500cls of charge-discharge cycle at 40°C, indicating that dinitrile compound and propylene carbonate can further improve the impedance growth rate of lithium-ion battery during 40°C charge-discharge cycle.

[0109] The preparation parameters and performance parameters of Examples 4-1 to 4-11 are shown in Table 4.

[0110] Table 4 Note: " / " in Table 4 indicates that there is no corresponding parameter.

[0111] 1,3,6-Hexanetrionitrile can complex with Mn and Ni, suppressing the side reactions of Mn and Ni at the negative electrode interface. As can be seen from Examples 1-7 and Examples 4-1 to 4-5, by adding 1,3,6-hexanetrionitrile to the electrolyte, the impedance growth rate of the lithium-ion battery during 500cls of charge-discharge cycle at 40°C is further reduced, indicating that the addition of 1,3,6-hexanetrionitrile can further improve the impedance growth rate of the lithium-ion battery during charge-discharge at 40°C.

[0112] As can be seen from Examples 1-7 and Examples 4-6 to 4-7, by adding 1,3,6-hexanetrionitrile and dionitrile compounds to the electrolyte, the impedance growth rate during the charge-discharge process of lithium-ion batteries at 40°C is significantly reduced. This indicates that both the dionitrile compound and 1,3,6-hexanetrionitrile are complexed with transition metals, and the synergistic effect of the two can significantly improve the impedance growth rate during the charge-discharge process of lithium-ion batteries at 40°C.

[0113] As can be seen from Examples 1-7 and Examples 4-8 to 4-9, by adding 1,3,6-hexanetrionitrile and propylene carbonate to the electrolyte, the impedance growth rate during the charge-discharge process of lithium-ion batteries at 40°C is reduced, indicating that the synergistic effect of propylene carbonate and 1,3,6-hexanetrionitrile can further improve the impedance growth rate during the charge-discharge process of lithium-ion batteries at 40°C.

[0114] As can be seen from Examples 1-7 and Examples 4-10 to 4-11, the addition of 1,3,6-hexanetrionitrile, dionitrile compounds, and propylene carbonate to the electrolyte further reduces the impedance growth rate during the 40°C charge-discharge process of the lithium-ion battery. This indicates that the synergistic effect of 1,3,6-hexanetrionitrile, dionitrile compounds, and propylene carbonate can further improve the impedance growth rate during the 40°C charge-discharge process of the lithium-ion battery. This is because, while 1,3,6-hexanetrionitrile and dionitrile compounds inhibit the contact between metal ions and the negative electrode interface, propylene carbonate can fill the area not covered by the passivation layer formed by compound I, providing more adequate protection for the negative electrode interface. This prevents side reactions of transition metal ions at the negative electrode interface from multiple aspects, thereby significantly improving the impedance growth rate during the 40°C charge-discharge cycle of the lithium-ion battery.

[0115] The preparation parameters and performance parameters of Examples 5-1 to 5-10 are shown in Table 5.

[0116] Table 5 Note: " / " in Table 5 indicates that there is no corresponding parameter.

[0117] As can be seen from Examples 1-7 and Examples 5-1 to 5-6, by adding diethyl difluoromethylphosphonate to the electrolyte, the impedance growth rate of the lithium-ion battery during a 500cls charge-discharge cycle at 40°C is further reduced, indicating that diethyl difluoromethylphosphonate can further improve the impedance growth rate of the lithium-ion battery during a 500cls charge-discharge cycle at 40°C. Specifically, diethyl difluoromethylphosphonate, based on the positive electrode interface film protection mechanism, can improve the stability of the positive electrode interface of the lithium-ion battery and further balance the initial impedance of the lithium-ion battery, suppressing the impedance growth rate of the lithium-ion battery during a 500cls charge-discharge cycle at 40°C.

[0118] As can be seen from Examples 1-7 and Examples 5-7 to Examples 5-10, the addition of dinitrile compounds, 1,3,6-hexanetrionitrile, propylene carbonate and diethyl difluoromethylphosphonate to the electrolyte significantly reduced the impedance growth rate of the lithium-ion battery during 500cls of charge-discharge cycles at 40°C, indicating that the impedance growth rate of the lithium-ion battery during 500cls of charge-discharge cycles at 40°C was significantly improved.

[0119] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover 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 elements inherent to such a process, method, or article.

[0120] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0121] 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, characterized in that, Includes the positive electrode and the electrolyte; The electrolyte comprises a compound of formula I: Wherein, R is selected from unsubstituted or R0-substituted C2-C6 alkyl, unsubstituted or R0-substituted C2-C6 alkenyl, unsubstituted or R0-substituted C2-C6 alkynyl, and unsubstituted or R0-substituted C5-C6 alkyl. 12 Nitrogen-containing heteroaryl groups, unsubstituted or R0-substituted C6-C 12 Any of the aryl groups, wherein the substituent R0 of each group is independently selected from any of the unsubstituted or substituted C1-C6 alkyl groups, and when substituted, the substituent is fluorine; Based on the total mass of the electrolyte, the mass percentage of the compound of formula I is A; The positive electrode sheet includes a positive electrode active material, which includes a metal element M, which includes Mn and Ni. Based on the mass of the positive electrode active material, the total doping amount of the metal element M is C, where 0.1≤A*C / 1000≤40 and 500ppm≤C≤5000ppm.

2. The electrochemical device according to claim 1, characterized in that, The electrochemical device satisfies at least one of the following conditions: (1) 1 ≤ A*C / 1000 ≤ 13; (2) 1000ppm ≤ C ≤ 3000ppm.

3. The electrochemical device according to claim 1 or 2, characterized in that, Based on the mass of the positive electrode active material, the Ni doping amount is C1, 500ppm≤C1≤1500ppm.

4. The electrochemical device according to claim 1 or 2, characterized in that, 0.1％≤A≤10％。 5. The electrochemical device according to claim 1, characterized in that, Compounds of Formula I include at least one of the following compounds:

6. The electrochemical device according to claim 1, characterized in that, The particle size Dv of the positive electrode active material 50 Satisfy: 3μm≤Dv 50 ≤30μm.

7. The electrochemical device according to claim 1, characterized in that, The electrolyte also includes propylene carbonate, and the mass percentage of propylene carbonate is E based on the total mass of the electrolyte, where E satisfies: 0.1% ≤ E ≤ 10%.

8. The electrochemical device according to claim 1, characterized in that, The electrolyte also includes 1,3,6-hexanetrionitrile, and the mass percentage of the 1,3,6-hexanetrionitrile based on the total mass of the electrolyte is H, where H satisfies: 2% ≤ H ≤ 4.5%.

9. The electrochemical device according to claim 1, characterized in that, The electrolyte also includes a dinitrile compound, which includes at least one of butadionitrile and adiponitrile. Based on the total mass of the electrolyte, the mass percentage of the dinitrile compound is Q, where Q satisfies: 1.5% ≤ Q ≤ 3.0%.

10. The electrochemical device according to claim 1, characterized in that, The electrolyte also includes diethyl difluoromethylphosphonate, and the mass percentage of diethyl difluoromethylphosphonate is D based on the total mass of the electrolyte, where D satisfies: 0.1% ≤ D ≤ 0.5%.

11. An electronic device, characterized in that, The electrochemical device includes any one of claims 1-10.

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