Electrochemical apparatus and electronic device

Abstract

The present application discloses an electrochemical apparatus and an electronic device. A positive electrode active material layer comprises a metal element M, wherein the metal element M comprises at least one of Ca and W. An electrolyte comprises a compound of formula (I). By means of a combination of the compound of formula (I) in the electrolyte and the metal element M in the positive electrode active material, and by selecting content A of the compound of formula (I) and content C of the metal element M to satisfy the conditional expression: 0.1≤A*C / 100≤400, the calendar life of the electrochemical apparatus in a high-temperature environment can be improved, and the impedance increase of the electrochemical apparatus in the high-temperature environment during the entire service life can also be mitigated.

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 requirements are being placed on the lifespan and safety performance of electrochemical devices, taking into account the varying usage time and operating temperatures of these products. In related technologies, electrochemical devices sometimes experience positive electrode metal dissolution and deposition at the negative electrode interface, leading to poor negative electrode interface stability. This, in turn, results in deteriorated high-temperature cycling performance and increased impedance of the electrochemical device.

[0003] Summary of the Invention

[0004] This application provides an electrochemical device and electronic device that can solve the problem of poor stability of the negative electrode interface in electrochemical devices.

[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, wherein the metal element M includes at least one of Ca or W. Based on the mass of the positive electrode active material, the total content of the metal element M is C, wherein A and C satisfy: 0.1 ≤ A*C / 100 ≤ 400. By controlling the electrolyte to include a compound of formula I and the metal element M of the positive electrode active material to include at least one of Ca or W, the mass percentage content of the compound of formula I and the metal element M is within the scope of this application. This not only improves the calendar lifetime (OCPD) of the electrochemical device in a high-temperature environment but also improves the impedance growth in a high-temperature environment throughout the entire service life of the electrochemical device.

[0010] In some embodiments, A and C satisfy: 2≤A*C / 100≤100.

[0011] In some embodiments, the electrochemical device satisfies at least one of the following conditions: (1) A satisfies: 0.1% ≤ A ≤ 10%; (2) C satisfies: 50 ppm ≤ C ≤ 5000 ppm.

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

[0013] By selecting the above-mentioned compound I, a lithium-containing inorganic oxide passivation layer rich in S and F elements can be formed at the electrode interface, which suppresses the damage of the negative electrode to the metal dissolved from the positive electrode. This can improve the stability of the negative electrode interface, improve the impedance of the electrochemical device, and also improve the charge-discharge cycle performance of the electrochemical device by increasing the ionic conductivity.

[0014] In some embodiments, the electrolyte further includes a trinitrile compound, wherein the mass percentage of the trinitrile compound is B, based on the total mass of the electrolyte, and B satisfies: 2% ≤ B ≤ 4.5%. By adjusting the mass percentage B of the trinitrile compound to the above range, the trinitrile compound can effectively inhibit the dissolution of Ca and W metal ions based on a complexation mechanism, while the electrolyte viscosity is appropriate, giving the electrolyte a good ion transport rate, thereby improving the charge-discharge rate performance of the electrochemical device.

[0015] In some embodiments, the trinitrile compound includes at least one selected from 1,3,5-pentanetrionitrile, 1,2,3-propanetrionitrile, 1,3,6-hexanetrionitrile, 1,2,6-hexanetrionitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,2,4-tris(2-cyanoethoxy)butane, and 1,2,5-tris(cyanoethoxy)pentane.

[0016] In some embodiments, the electrolyte further includes propyl propionate, and the mass percentage of propyl propionate is F based on the total mass of the electrolyte, wherein F satisfies: 10% ≤ F ≤ 60%. By adjusting the mass percentage of propyl propionate F within the above range, propyl propionate can further improve the kinetic performance of the electrochemical device and mitigate the negative impact of the presence of trinitrile compounds increasing electrolyte viscosity on the kinetic performance of the electrochemical device.

[0017] 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, wherein D satisfies: 0.1% ≤ D ≤ 0.5%. By adjusting the mass percentage D of diethyl difluoromethylphosphonate within the above range, diethyl difluoromethylphosphonate can work with trinitrile compounds to enhance the stability of the positive electrode interface, improve the OCPD of the electrochemical device in a high-temperature environment, and simultaneously ensure appropriate impedance of the electrochemical device, thereby enabling the electrochemical device to have good low-temperature discharge performance.

[0018] In some embodiments, the electrolyte further includes fluoroacetonitrile, and the mass percentage of fluoroacetonitrile is E based on the total mass of the electrolyte, wherein E satisfies: 0.1% ≤ E ≤ 5.0%. By selecting the mass percentage E of fluoroacetonitrile within the above range, fluoroacetonitrile can act on Ca and W. Based on the complexation mechanism of nitrile on metal ions and the low viscosity of fluoroacetonitrile itself, it can synergistically improve the stability of the positive electrode interface while improving the low-temperature discharge performance of the battery, and at the same time reduce the gas generation of the electrolyte at the electrode interface in high-temperature environments, thereby improving the OCPD of the electrochemical device in high-temperature environments.

[0019] Secondly, this application provides an electronic device including the electrochemical device described above.

[0020] Based on the electrochemical device and electronic device of the present application embodiments, by combining the compound of formula I in the electrolyte and the metal element M in the positive electrode active material, and by selecting the content A of the compound of formula I and the content C of the metal element M to satisfy the condition 0.1≤A*C / 100≤400, it is possible not only to improve the calendar life of the electrochemical device in a high-temperature environment, but also to improve the impedance growth rate in a high-temperature environment throughout the entire service life of the electrochemical device. Detailed Implementation

[0021] 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.

[0022] With the development of electric vehicles, battery lifespan is receiving increasing attention. Taking lithium batteries as an example, as the number of charge and discharge cycles increases, their capacity gradually decreases. If the capacity decreases to a certain threshold, the lithium battery can no longer be used normally.

[0023] Battery life primarily includes calendar life (OCPD, One cycle per day) and cycle life. Calendar life refers to the time from the date of manufacture to the end of its lifespan. The end of life typically does not mean the battery can no longer discharge, but rather that the battery capacity has decreased to a certain percentage of its rated capacity (e.g., 70%). Due to the chemical nature of batteries, even without charging or discharging, the calendar life of a battery will decrease over time during periods of inactivity. For example, metals at the positive electrode can dissolve, especially at high temperatures, which accelerates this dissolution. This dissolved metal deposits at the negative electrode interface, leading to poor interface stability and increased battery impedance. Consequently, the calendar life of the electrochemical device is shortened, and its cycle performance deteriorates.

[0024] Based on this, the first aspect of this application provides an electrochemical device comprising a positive electrode, a negative electrode, a separator, and an electrolyte. By selecting an electrolyte comprising a compound of formula I, and a positive electrode active material comprising a metal element M (including at least one of Ca or W), not only can the calendar lifetime (OCPD) of the electrochemical device in a high-temperature environment be improved, but also the impedance growth rate in a high-temperature environment throughout the entire lifespan of the electrochemical device can be improved.

[0025] It should be noted that, in the following explanation, lithium-ion batteries are used as an example of electrochemical devices to illustrate this application; however, the electrochemical devices of this application are not limited to lithium-ion batteries. The specific technical solution is as follows:

[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 electrode current collector and a positive electrode active material layer disposed on the surface of the positive electrode current collector. The positive electrode active material layer of this application includes a positive electrode active material, which is any substance capable of reversibly inserting and deintercalating lithium ions. The positive electrode active material of this application includes a metal element M, and the metal element M includes at least one of Ca or W.

[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. A and C satisfy: 0.1 ≤ A*C / 100 ≤ 400. For example, A*C / 100 can be 0.1, 2.0, 50, 100, 155, 220, 254, 295, 330, 385, 400, or a range of any two of these values.

[0030] In this application, the positive electrode active material may include a lithium-containing active material, with Ca and W doped into it. Since W and Ca have large ionic radii, they cause lattice expansion in the lithium-containing active material, which helps reduce charge transfer resistance, decrease polarization, and suppress phase transitions. However, Ca and W pose a risk of dissolution. The dissolved Ca and W reach the negative electrode, damaging the negative electrode interface stability and thus worsening OCPD and impedance growth during the OCPD process. By adding a compound of formula I, the higher reduction potential of formula I can preferentially form a lithium-containing inorganic compound negative electrode interface passivation layer rich in S and F elements at the negative electrode, suppressing the damage of W and Ca to the negative electrode interface and improving the negative electrode interface stability. Formula I compound can also form a lithium-containing inorganic compound positive electrode interface passivation layer rich in S and F elements at the positive electrode interface, improving the positive electrode interface stability. Therefore, this application, by selecting both formula I compound and metal element M synergistically, simultaneously improves the stability of the positive and negative electrode interfaces, not only improving the calendar lifetime (OCPD) of the electrochemical device at high temperatures but also improving the impedance growth rate at high temperatures throughout the entire lifespan of the electrochemical device. When A*C / 100 exceeds the upper limit of 400, the content of Formula I compound is too high, leading to excessive inorganic components in the passivation layer at the positive and / or negative electrode interfaces. This makes the passivation layers at the positive and negative electrode interfaces prone to fragmentation, reducing interface stability and affecting the cycle performance of the electrochemical device. Alternatively, excessive metal element M content can easily dissolve and damage the stability of the negative electrode interface. When A*C / 100 is below the lower limit of 0.1, the content of Formula I compound is too low, making it impossible to form a lithium-containing inorganic compound negative electrode interface passivation layer rich in S and F elements. This results in insufficient protection of the negative electrode and an inability to improve OCPD and impedance growth during the OCPD process.

[0031] In some embodiments, 0.1% ≤ A ≤ 10%, for example, A can be 0.1%, 1.5%, 2.6%, 3.5%, 4.2%, 6.4%, 8.8%, 10%, or a range of any two of these values. By adjusting A within the above range, the compound of Formula I can form a lithium-containing inorganic compound passivation layer of suitable thickness at the negative electrode interface, which can effectively suppress the contact between the metal dissolved from the positive electrode and the negative electrode, effectively improve the stability of the negative electrode interface, prevent the accumulation of metal dissolved from the positive electrode at the negative electrode leading to the deterioration of the negative electrode impedance, and thus improve the impedance growth during OCPD and the OCPD process.

[0032] In some embodiments, C satisfies: 50ppm ≤ C ≤ 5000ppm. For example, C can be 50ppm, 100ppm, 500ppm, 800ppm, 2000ppm, 3500ppm, 5000ppm, or a range of any two of these values. By adjusting C within the above range, the contents of W and Ca are made appropriate. This allows the large ionic radii of W and Ca to expand the lattice of the lithium-containing active material, thereby reducing charge transfer resistance, decreasing polarization, and suppressing phase transitions. Simultaneously, it prevents excessive W and Ca leaching and deposition at the negative electrode interface, which could negatively impact battery lifespan.

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

[0034] In some embodiments, the electrolyte further includes a trinitrile compound, the mass percentage of which is B, based on the total mass of the electrolyte, and B satisfies: 2% ≤ B ≤ 4.5%. For example, B can be 2.0, 2.2, 2.5, 2.8, 3.2, 3.4, 3.5, 3.8, 4.2, 4.5, or a range of any two of these values. By introducing the trinitrile compound, the CN functional group of the trinitrile compound can complex with Ca and W metal ions in the positive electrode active material, thereby inhibiting metal dissolution from the positive electrode side and reducing damage to the negative electrode. By adjusting the mass percentage B of the trinitrile compound within the above range, the trinitrile compound can effectively inhibit the dissolution of Ca and W metal ions, while the electrolyte viscosity is suitable, giving the electrolyte a good ion transport rate, thereby improving the charge / discharge rate performance of the electrochemical device.

[0035] In some embodiments, the trinitrile compound includes at least one selected from 1,3,5-pentanetricarbonitrile, 1,2,3-propanetricarbonitrile, 1,3,6-hexanetricarbonitrile, 1,2,6-hexanetricarbonitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,2,4-tris(2-cyanoethoxy)butane, and 1,2,5-tris(cyanoethoxy)pentane.

[0036] In some embodiments, the electrolyte further includes propyl propionate, wherein the mass percentage of propyl propionate is F, based on the total mass of the electrolyte, and 10% ≤ F ≤ 60%. For example, F can be 10%, 15%, 25%, 30%, 35%, 40%, 45%, 50%, 60%, or a range of any two of these values. Propyl propionate can further improve the kinetic performance of the electrochemical device and mitigate the negative impact of the increased electrolyte viscosity due to the presence of trinitrile compounds on the kinetic performance of the electrochemical device.

[0037] In some embodiments, the electrolyte further includes diethyl difluoromethylphosphonate, which can be used to improve the deterioration of high-temperature storage performance of the electrochemical device due to the presence of propyl propionate. The mass percentage of diethyl difluoromethylphosphonate is D, based on the total mass of the electrolyte, where D satisfies: 0.1% ≤ D ≤ 0.5%. For example, D can be 0.10%, 0.22%, 0.25%, 0.31%, 0.35%, 0.40%, 0.43%, 0.50%, or a range of any two of these values. By adjusting the mass percentage D of diethyl difluoromethylphosphonate within the above range, diethyl difluoromethylphosphonate can, together with the trinitrile compound, enhance the stability of the positive electrode interface, improve the OCPD of the electrochemical device in a high-temperature environment, and simultaneously ensure appropriate impedance of the electrochemical device, thus enabling the electrochemical device to have good low-temperature discharge performance.

[0038] In some embodiments, the electrolyte further includes fluoroacetonitrile, which helps improve the kinetic performance of the electrochemical device. The mass percentage of fluoroacetonitrile is E, based on the total mass of the electrolyte, where 0.1% ≤ E ≤ 5.0%. For example, E can be 0.1%, 0.2%, 1.2%, 1.8%, 2.3%, 2.9%, 3.2%, 4.1%, 4.5%, 5.0%, or a range of any two of these values. By selecting the mass percentage E of fluoroacetonitrile within the above range, fluoroacetonitrile can act on Ca and W, improving the low-temperature discharge performance of the battery while synergistically enhancing the stability of the positive electrode interface based on the complexation mechanism of nitrile on metal ions and the low viscosity of fluoroacetonitrile itself. Simultaneously, it reduces the gas generation at the electrode interface in high-temperature environments, improving the OCPD of the electrochemical device in high-temperature environments.

[0039] The electrolyte also includes lithium salts. This application does not impose any particular limitation on the type of lithium salt in the electrolyte, as long as it achieves the purpose of this application. For example, it may include, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium bis(fluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(oxalateborate)borate (LiBOB), or lithium difluorooxalateborate (LiDFOB). Based on the total mass of the electrolyte, the mass percentage of lithium salts can be from 8% to 15%, for example, the mass percentage of lithium salts can be 8%, 9%, 10%, 11%, 12.5%, 13%, 15%, or a range consisting of any two of these values.

[0040] 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.

[0041] 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 include 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), propylene carbonate (PC), 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%.

[0042] 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.

[0043] 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.

[0044] The cathode material layer of this application includes a cathode active material, which can be one or more layers. Each layer in a multilayer cathode material layer can contain the same or different cathode active materials. This application does not impose any particular limitation on the cathode active material, as long as it can achieve the purpose of this application. For example, the cathode active material can include, but is not limited to, at least one of lithium nickel cobalt manganese oxide (e.g., NCM811, NCM622, NCM523, NCM111), lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide (LiCoO2), lithium manganese oxide, lithium manganese iron phosphate, or lithium titanate. A metal element M (including at least one of Ca and W) is doped into the above-mentioned cathode active material.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] In this application, the electrochemical device further includes a negative electrode, which comprises a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. The phrase "a 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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).

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] Example

[0062] 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.

[0063] Test methods

[0064] 1. 40℃ OCPD charge-discharge cycle test method

[0065] The test temperature was set to a constant 40°C. The lithium-ion battery was charged at a constant current of 0.5C to 4.5V, then charged at a constant voltage of 4.5V to 0.05C, left to stand for 12 hours, and then discharged at a constant current of 0.2C to 3.0V, left to stand for 5 hours. This constitutes one charge-discharge cycle, with a total time of 24 hours. This is the first cycle, and the discharge capacity of the first cycle is recorded. The lithium-ion battery was cycled using the above method, and the discharge capacity of each cycle was recorded until the discharge capacity of the lithium-ion battery decreased to 80% of the discharge capacity of the first cycle. This is the entire process of the 40°C calendar life (OCPD) of the lithium-ion battery.

[0066] The number of charge-discharge cycles during the entire process of the 40℃ OCPD is recorded, which is the number of charge-discharge cycles of the 40℃ OCPD.

[0067] 2. Impedance growth rate test method for OCPD at 40℃

[0068] (1) Adjust the test temperature to a constant 25℃. Use an OCV / IMP voltage internal resistance tester to test the lithium-ion battery at 20% SOC. Record the first AC impedance of the lithium-ion battery at 1KHz, in mΩ.

[0069] (2) Place the lithium-ion battery after the first AC impedance test in (1) in an environment of 40°C. Charge the lithium-ion battery with a constant current of 0.5C to 4.5V, charge it with a constant voltage of 4.5V to 0.05C, let it stand for 12 hours, and then discharge it with a constant current of 0.2C to 3.0V and let it stand for 5 hours. This is one charge-discharge cycle, with a total time of 24 hours. This is the first cycle, and the discharge capacity of the first cycle is recorded. Perform charge-discharge cycles on the lithium-ion battery according to the above method, and record the discharge capacity of each cycle until the discharge capacity of the lithium-ion battery decays to 80% of the discharge capacity of the first cycle. This is the entire process of the 40°C calendar life (OCPD) of the lithium-ion battery. Record the AC impedance of the lithium-ion battery at 1KHz when the discharge capacity is reduced to 80%, and record it as the OCPD AC impedance, in mΩ.

[0070] The impedance growth rate of an OCPD at 40℃ = (initial AC impedance / initial AC impedance) * 100%

[0071] Example 1-1

[0072] (1) Preparation of the positive electrode

[0073] 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 current collector, dried at 85°C, and cold-pressed to obtain a positive electrode with a single-sided coating thickness of 95 μm. The above steps were then repeated on the other surface of the aluminum foil to obtain a positive electrode with a double-sided coating. After cutting and welding the positive electrode tabs, a positive electrode 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 .

[0074] Among them, metal element M is incorporated into the positive electrode active material. The doping types and doping amounts of metal element M in the positive electrode active material are shown in Table 1.

[0075] (2) Preparation of negative electrode

[0076] Artificial graphite (anode 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%. The 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 with a single-sided coating thickness of 132 μm. The above steps were repeated on the other surface of the same copper foil to obtain a negative electrode with a double-sided coating. After cutting and welding of negative electrode tabs and nickel tabs, a negative electrode with dimensions of 76 mm × 867 mm was obtained for use. The compaction density of the negative electrode material layer was 1.80 g / cm³. 3 .

[0077] (3) Preparation of the separating membrane

[0078] A porous polyethylene (PE) membrane with a thickness of 5 μm was used.

[0079] (4) Preparation of electrolyte

[0080] 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.

[0081] The mass percentages of compounds of Formula I are shown in Table 1, with the remainder being the base solvent.

[0082] (5) Assembly of lithium-ion electrons

[0083] The positive electrode tab is installed on the positive electrode, and the negative electrode tab is installed on the negative electrode. The positive electrode with the positive electrode tab, the separator, and the negative electrode with the negative electrode tab are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The electrode assembly is then wound to obtain the electrode assembly. The electrode assembly is placed in an outer aluminum-plastic film package, and after dehydration at 80°C, the electrolyte is injected and the assembly is sealed. Then, the lithium-ion battery is obtained through processes such as settling, formation (0.2C constant current charging to 3.5V, then 1C constant current charging to 3.9V), capacity testing, degassing, and edge trimming.

[0084] Examples 1-2 to 1-21 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 type and content C of metal element M in the preparation of the cathode are 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.

[0085] Comparative Example 1-1 was identical to Example 1-1 except that no compound of Formula I was added to the electrolyte. The mass percentage of the base solvent was changed, while the mass percentage of the lithium salt remained constant.

[0086] Comparative Examples 1-2 are the same as Examples 1-1, except that the positive electrode active material is not doped with metal element M.

[0087] Comparative Examples 1-3 to 1-4 were identical to Example 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 cathode 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.

[0088] Examples 2-1 to 2-9 are identical to Examples 1-5, except that a trinitrile 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.

[0089] Examples 3-1 to 3-5 are identical to Examples 1-5, except that diethyl difluoromethylphosphonate 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.

[0090] Examples 3-6 to 3-8 are identical to Examples 1-5, except that diethyl difluoromethylphosphonate and trinitrile compounds are 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.

[0091] Examples 4-1 to 4-5, except that fluoroacetonitrile was added during the preparation of the electrolyte as shown in Table 4, were otherwise the same.

[0092] Examples 1-5 are identical. The only difference is the mass percentage of the base solvent, which varies, while the mass percentage of the lithium salt remains constant.

[0093] Examples 4-6 to 4-11 are identical to Examples 1-5, except that fluoroacetonitrile, diethyl difluoromethylphosphonate, and trionitrile compounds 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.

[0094] Examples 5-1 to 5-4 are identical to Examples 1-5, except that propyl propionate is added during the preparation of 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 5-5 to 5-7 are identical to Examples 1-5, except that propyl propionate, fluoroacetonitrile, diethyl difluoromethylphosphonate, and trionitrile compounds 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] The preparation parameters and performance parameters of Examples 1-1 to 1-21 and Comparative Examples 1-1 to 1-4 are shown in Table 1.

[0097] Table 1

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

[0099] In this application, the larger the number of 40℃ OCPD charge-discharge cycles, the better the 40℃ OCPD charge-discharge cycle performance of the lithium-ion battery; the smaller the 40℃ OCPD impedance growth rate, the better the improvement effect on the 40℃ OCPD impedance growth rate of the lithium-ion battery.

[0100] As can be seen from Examples 1-1 to 1-21 and Comparative Examples 1-1 to 1-4, the lithium-ion batteries of this application, by adding a compound of Formula I to the electrolyte and a metal element M of the positive electrode active material including at least one of Ca or W, and the mass percentage A of the compound of Formula I and the doping content C of the metal element M satisfying the condition 0.1≤A*C / 100≤400, exhibit a larger number of 40℃ OCPD charge-discharge cycles and a smaller 40℃ OCPD impedance growth rate. This indicates that adding a compound of Formula I and the metal element M to the electrolyte has a good effect on improving the 40℃ OCPD charge-discharge cycle performance and the 40℃ OCPD impedance growth rate of the lithium-ion battery.

[0101] As can be seen from Examples 1-1 to 1-15, Comparative Examples 1-3 and 1-4, when the mass percentage A of the compound of Formula I and the doping content C of the metal element M exceed the range of 0.1≤A*C / 100≤400, it is difficult to select the mass percentage A of the compound of Formula I and the doping content C of the metal element M within a suitable range. For example, in Comparative Examples 1-3, the product of the mass percentage A of the compound of Formula I and the doping content C of the metal element M is less than 0.10, which makes it difficult to improve the 40℃ OCPD charge-discharge cycle performance and the 40℃ OCPD impedance growth rate of the lithium-ion battery. In Comparative Examples 1-4, the product of the mass percentage A of the compound of Formula I and the doping content C of the metal element M is higher than 400, which easily leads to at least one of the two contents being too high, thus bringing negative effects and causing the 40℃ OCPD charge-discharge cycle performance and the 40℃ OCPD impedance growth rate of the lithium-ion battery to deteriorate.

[0102] As can be seen from Examples 1-5, Examples 1-12 to Examples 1-15, when the mass percentage A of compound I satisfies the condition 0.1% ≤ A ≤ 10%, it can further improve the 40℃ OCPD charge-discharge cycle performance and the 40℃ OCPD impedance growth rate of lithium-ion batteries.

[0103] As can be seen from Examples 1-1 to 1-11, when the doping content C of metal element M in the positive electrode active material satisfies the condition 50ppm≤C≤5000ppm, the content of metal element M can be better controlled within a suitable range, reducing the damage caused by the dissolution of metal element M to the negative electrode, and thus further improving the 40℃ OCPD charge-discharge cycle performance and 40℃ OCPD impedance growth rate of lithium-ion batteries.

[0104] The preparation parameters and performance parameters of Examples 2-1 to 2-9 are shown in Table 2.

[0105] Table 2

[0106] Note: " / " in Table 2 indicates that there is no corresponding parameter.

[0107] As can be seen from Examples 2-1 to 2-9 and Examples 1-5, the lithium-ion batteries of this application, by adding a trinitrile compound to the electrolyte, wherein the mass percentage B of the trinitrile compound satisfies the condition 2% ≤ B ≤ 4.5%, the CN functional group of the trinitrile compound can complex with Ca and W metal ions in the positive electrode active material, inhibiting the dissolution of the positive electrode metal and reducing damage to the negative electrode, thereby further improving the 40℃ OCPD charge-discharge cycle performance and the 40℃ OCPD impedance growth rate of the lithium-ion battery.

[0108] The preparation parameters and performance parameters of Examples 3-1 to 3-8 are shown in Table 3.

[0109] Table 3

[0110] Note: " / " in Table 3 indicates that there is no corresponding parameter.

[0111] As can be seen from Examples 1-5 and Examples 3-1 to 3-5, adding diethyl difluoromethylphosphonate to the electrolyte and selecting a content D of diethyl difluoromethylphosphonate in the range of 0.1% ≤ D ≤ 0.5% can improve the 40℃ OCPD charge-discharge cycle performance and the 40℃ OCPD impedance growth rate of lithium-ion batteries.

[0112] As can be seen from Examples 3-1 to 3-5 and Examples 3-6 to 3-8, compared with Examples 3-1 to 3-5, the lithium-ion batteries in Examples 3-6 to 3-8 have a larger number of 40°C OCPD charge-discharge cycles and a smaller 40°C OCPD impedance growth rate. This indicates that the lithium-ion batteries of this application, by adding diethyl difluoromethylphosphonate and trinitrile compounds to the electrolyte, can have diethyl difluoromethylphosphonate and trinitrile compounds jointly enhance the positive electrode interface stability, thereby further optimizing the 40°C OCPD charge-discharge cycle performance and 40°C OCPD impedance growth rate of the lithium-ion battery.

[0113] The preparation parameters and performance parameters of Examples 4-1 to 4-11 are shown in Table 4.

[0114] Table 4

[0115] Note: " / " in Table 4 indicates that there is no corresponding parameter.

[0116] Adding fluoroacetonitrile to the electrolyte can improve the gas generation at the electrode interface of the electrolyte in high-temperature environments, based on the complexation mechanism of nitrile on metal ions and the low viscosity of fluoroacetonitrile itself. This can improve the OCPD of lithium-ion batteries in high-temperature environments. As can be seen from Examples 1-5 and Examples 4-1 to 4-5, the addition of fluoroacetonitrile to the electrolyte further increases the number of 40℃ OCPD charge-discharge cycles of lithium-ion batteries and further reduces the 40℃ OCPD impedance growth rate, indicating that fluoroacetonitrile improves the 40℃ OCPD charge-discharge cycle performance and the 40℃ OCPD impedance growth rate of lithium-ion batteries.

[0117] As can be seen from Examples 4-6 to 4-11, the addition of fluoroacetonitrile and trinitrile compounds to the electrolyte can simultaneously improve the 40°C OCPD charge-discharge cycle performance and the 40°C OCPD impedance growth rate of lithium-ion batteries; the addition of fluoroacetonitrile and diethyl difluoromethylphosphonate to the electrolyte has an even better effect on improving the 40°C OCPD charge-discharge cycle performance of lithium-ion batteries.

[0118] The preparation parameters and performance parameters of Examples 5-1 to 5-7 are shown in Table 5.

[0119] Table 5

[0120] Note: " / " in Table 5 indicates that there is no corresponding parameter.

[0121] Propyl propionate has a low viscosity. Adding propyl propionate to the electrolyte can further improve the kinetic performance of lithium-ion batteries. As can be seen from Examples 1-5, 5-1 to 5-7, when propyl propionate is added to the electrolyte and the mass percentage F of propyl propionate satisfies the condition 10% ≤ F ≤ 60%, the lithium-ion battery exhibits a larger number of 40°C OCPD charge-discharge cycles and a smaller 40°C OCPD impedance growth rate. This indicates that the addition of propyl propionate helps to further improve the 40°C OCPD charge-discharge cycle performance and the 40°C OCPD impedance growth rate of lithium-ion batteries.

[0122] As can be seen from Examples 5-5 to 5-7, in the presence of propyl propionate in the electrolyte, the addition of at least one of trinitrile compound, diethyl difluoromethylphosphonate, and fluoroacetonitrile can further improve the 40°C OCPD charge-discharge cycle performance and the 40°C OCPD impedance growth rate of lithium-ion batteries.

[0123] 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.

[0124] 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.

[0125] 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, Including 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 compound I is A; The positive electrode includes a positive electrode active material, which includes a metal element M, and the metal element M includes at least one of Ca or W. Based on the mass of the positive electrode active material, the total content of the metal element M is C, wherein A and C satisfy: 0.1≤A*C / 100≤400.

2. The electrochemical device according to claim 1, characterized in that, A and C satisfy: 2≤A*C / 100≤100.

3. The electrochemical device according to claim 1 or 2, characterized in that, The electrochemical device satisfies at least one of the following conditions: (1) 0.1% ≤ A ≤ 10%; (2) 50 ppm ≤ C ≤ 5000 ppm.

4. The electrochemical device according to claim 1, characterized in that, Compounds of Formula I include at least one of the following compounds:

5. The electrochemical device according to claim 1, characterized in that, The electrolyte also includes a trinitrile compound, and the mass percentage of the trinitrile compound is B based on the total mass of the electrolyte, wherein B satisfies: 2% ≤ B ≤ 4.5%.

6. The electrochemical device according to claim 5, characterized in that, The trinitrile compound includes at least one selected from 1,3,5-pentanetricarbonitrile, 1,2,3-propanetricarbonitrile, 1,3,6-hexanetricarbonitrile, 1,2,6-hexanetricarbonitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,2,4-tris(2-cyanoethoxy)butane, and 1,2,5-tris(cyanoethoxy)pentane.

7. The electrochemical device according to claim 1, characterized in that, The electrolyte also includes propyl propionate, and the mass percentage of propyl propionate is F based on the total mass of the electrolyte, where F satisfies: 10% ≤ F ≤ 60%.

8. 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%.

9. The electrochemical device according to claim 1, characterized in that, The electrolyte also includes fluoroacetonitrile, and the mass percentage of fluoroacetonitrile based on the total mass of the electrolyte is E, where E satisfies: 0.1% ≤ E ≤ 5.0%.

10. An electronic device, characterized in that, The electrochemical device includes any one of claims 1-9.

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