Electrochemical device and electronic device

Abstract

Provided in the present application are an electrochemical device and an electronic device. The electrochemical device comprises a positive electrode sheet, a negative electrode sheet, and an electrolyte. The electrolyte is composed of a compound of formula I and a compound of formula II. The compound of formula I is shown below, and the compound of formula II is shown below, wherein n is 0, 1, or 2. Based on the total mass of the electrolyte, the mass percentage of the compound of formula I is a%, wherein 5≤a≤50. In the present application, by means of controlling the components and the amounts of the components of the electrolyte in the electrochemical device, the cycle performance and storage performance of the electrochemical device at a high temperature can be improved, and the low-temperature loading performance of the electrochemical device can also be improved at the same time.

Description

An electrochemical device and an electronic device

[0001] This application claims priority to Chinese Patent Application No. 202411208205.9, filed on August 30, 2024, entitled "An Electrochemical Device and an Electronic Device", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of energy storage, and more specifically, to an electrochemical device and an electronic device. Background Technology

[0003] Electrochemical devices (such as lithium-ion batteries) are widely used in portable electronic products, electric vehicles, aerospace, and energy storage due to their advantages such as high energy density, good cycle performance, safety, environmental friendliness, and lack of memory effect. With the increasing prevalence of electrochemical devices like lithium-ion batteries in daily life, users require these devices to exhibit good electrical performance under both high and low temperature conditions. However, currently, electrochemical devices like lithium-ion batteries often cannot simultaneously achieve optimal cycle performance at high temperatures, storage performance, and low-temperature load-bearing capacity. Summary of the Invention

[0004] This application provides an electrochemical device and an electronic device. The electrochemical device of this application has excellent cycling performance and storage performance at high temperatures, while also exhibiting good low-temperature tensile performance.

[0005] In a first aspect, embodiments of this application provide an electrochemical device comprising a positive electrode, a negative electrode, and an electrolyte, wherein the electrolyte comprises a compound of formula I and a compound of formula II. Compound of formula I is: R is selected from any one of the following: fluorinated or unsubstituted C2-C6 alkyl groups, C6-C12 nitrogen-containing heterocyclic groups, and fluorinated or unsubstituted C6-C12 aryl groups. Compound II is: Where n is 0, 1, or 2, M is selected from C or O, and X is selected from... or R 21 R 22 Each is independently selected from H, , , , , Any of the following, R 21 and R 22 Not both selected from H, and X, R 21 and R 22 It contains at least one sulfur atom. Based on the total mass of the electrolyte, the mass percentage of compound I is a%, 1≤a≤50%.

[0006] In the above technical solution, the compound of formula I has a low viscosity and, due to its sulfone and fluorinated structure, possesses strong antioxidant capacity. When the electrolyte of the electrochemical device contains more than 1 wt% of compound of formula I, the low-temperature load-bearing performance of the electrochemical device can be significantly improved. However, the inventors discovered that although the compound of formula I in the electrolyte forms a stable film structure on the positive electrode of the electrochemical device, the SEI (Solid Electrolyte Interphase) film formed on the negative electrode is not very stable, which is detrimental to the high-temperature cycling performance and high-temperature storage performance of the electrochemical device. The inventors further discovered that if the content of compound of formula I is controlled to be no more than 50 wt%, and the electrolyte also contains compound of formula II, then compound of formula II will work together with compound of formula I to form a low-impedance and highly stable SEI film on the negative electrode, inhibiting the reaction of compound of formula I on the negative electrode. This can even improve the cycling performance and storage performance of the electrochemical device.

[0007] In one possible implementation, the percentage content of compound II is b%, based on the total mass of the electrolyte, 0.2 ≤ b ≤ 6, and 0.167 ≤ a / b ≤ 125.

[0008] In the above technical solutions, in electrolytes that meet the above conditions, compound II has a more significant inhibitory effect on the reaction of compound I at the negative electrode, and the storage performance and cycling performance of the electrochemical device at high temperature will be better.

[0009] In one possible implementation, the electrolyte satisfies at least one of the following conditions: (1) 2 ≤ a ≤ 10; (2) 0.5 ≤ b ≤ 4; (3) 0.5 ≤ a / b ≤ 20.

[0010] In the above technical solution, in the electrolyte that meets the above conditions, the inhibitory effect of compound II on the reaction of compound I at the negative electrode is more obvious, and the storage performance and cycling performance of the electrochemical device at high temperature will be further improved.

[0011] In one possible implementation, the compound of formula I includes at least one of the following compounds:

[0012]

[0013] In the above technical solution, the compound of formula I with the above structure can better improve the cycling performance, storage performance and low temperature load performance of the electrochemical device at high temperature.

[0014] In one possible implementation, the compound of formula II includes at least one of the following compounds:

[0015]

[0016] In the above technical solution, the compound of formula II with the above structure can work together better with the compound of formula I to improve the cycle performance and storage performance of the electrochemical device at high temperature.

[0017] In one possible implementation, the electrolyte also includes ethylene carbonate and propylene carbonate, with the total content of ethylene carbonate and propylene carbonate being c% based on the total mass of the electrolyte, and 10 ≤ c ≤ 50.

[0018] In the above technical solution, ethylene carbonate and propylene carbonate can improve the solubility of lithium salt in the electrolyte, thereby improving the ion concentration of the electrolyte; therefore, an electrolyte that meets the above conditions can further improve the low-temperature load performance of the electrochemical device.

[0019] In one possible implementation, 0.05 ≤ a / c ≤ 0.5.

[0020] In the above technical solution, when the total amount of ethylene carbonate and propylene carbonate meets the above conditions, the low-temperature load-bearing performance of the electrochemical device can be further improved.

[0021] In one possible implementation, the electrolyte also includes fluoroethylene carbonate, with the content of fluoroethylene carbonate being d% based on the total mass of the electrolyte, and 0.05≤a / d≤50.

[0022] In the above technical solution, fluoroethylene carbonate can work together with compounds of formula I and formula II to form a stable SEI film with low impedance on the surface of the negative electrode, which is beneficial to improving the interface performance of the electrochemical device and thus enhancing the high-temperature cycle performance of the electrochemical device.

[0023] In one possible implementation, 3 ≤ d ≤ 15, and 0.13 ≤ a / d ≤ 3.33.

[0024] In the above technical solution, when the content of fluoroethylene carbonate meets the above conditions, it is more conducive to improving the interfacial performance of the electrochemical device, thereby further improving the high-temperature cycling performance of the electrochemical device.

[0025] In one possible implementation, the electrolyte also includes lithium difluorophosphate, with a mass percentage of lithium difluorophosphate of e%, where 0.2 ≤ e ≤ 2, based on the total mass of the electrolyte.

[0026] In the above technical solution, the electrolyte contains a certain amount of lithium difluorophosphate, which, together with the compound of formula II, forms a protective film with low impedance on the positive electrode of the electrochemical device, thereby further improving the low-temperature load performance of the electrochemical device.

[0027] In one possible implementation, the electrolyte also includes nitriles, with the nitrile mass percentage being f%, 1≤f≤8%, based on the total mass of the electrolyte.

[0028] In the above technical solution, nitriles in the electrolyte can form a protective film on the positive electrode, which can reduce the capacity loss rate of the electrochemical device and further improve the high-temperature cycle performance and high-temperature storage performance of the electrochemical device; however, nitriles have a destructive effect on the negative electrode, and their content should not be too high.

[0029] In one possible implementation, the nitrile includes at least one of dinitrile and trinitrile, and the ratio of the mass percentage of trinitrile to the mass percentage of dinitrile is not greater than 4 based on the total mass of the electrolyte.

[0030] In the above technical solution, the mass percentage ratio of trionitrile and dionitrile is controlled within a range of no more than 4, which is beneficial to further improve the high-temperature storage performance and high-temperature cycling performance of the electrochemical device.

[0031] In one possible implementation, the dinitrile includes at least one of butadionitrile, adiponitrile, glutaronitrile, and heptanonitrile; and / or, the trinitrile includes 1,3,6-propanetrionitrile.

[0032] Secondly, embodiments of this application provide an electronic device that includes the electrochemical device described above.

[0033] The beneficial effects of this application are:

[0034] This application provides an electrochemical device and an electronic device. The electrochemical device includes a positive electrode, a negative electrode, and an electrolyte. The electrolyte includes compounds of formula I and formula II. Based on the total mass of the electrolyte, the mass percentage of compound I is a%, where 1 ≤ a ≤ 50. By adjusting the inclusion of compounds of formula I and formula II in the electrolyte, and ensuring that the types and mass percentages of compounds of formula I and formula II are within the scope of this application, the electrochemical device of this application exhibits excellent cycling performance and storage performance at high temperatures, while also demonstrating good low-temperature load-bearing performance. Embodiments of the present invention

[0035] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0036] The electrochemical and electronic devices of the embodiments of this application will be described in detail below.

[0037] In a first aspect, this application provides an electrochemical device comprising a positive electrode, a negative electrode, and an electrolyte. By defining the specific components and their content in the electrolyte, this application enables the electrochemical device to possess both excellent high-temperature cycling and high-temperature storage performance, as well as excellent low-temperature load-bearing performance.

[0038] The specific structure of the electrochemical device in this application is as follows:

[0039] electrolyte

[0040] The electrolyte plays a role in transporting lithium ions and electrons, ensuring the formation of pathways within the electrochemical device. In this application, the electrolyte includes a compound of formula I: R is selected from any one of fluorinated or unsubstituted C2-C6 alkyl groups, C6-C12 nitrogen-containing heterocyclic groups, and fluorinated or unsubstituted C6-C12 aryl groups.

[0041] The inventors discovered that compounds of formula I have low viscosity and, due to their sulfone and fluorinated structures, possess strong antioxidant capabilities. When the electrolyte of an electrochemical device contains more than 1 wt% of compounds of formula I, the low-temperature load-bearing performance of the electrochemical device can be significantly improved. However, the inventors also found that while compounds of formula I in the electrolyte form a stable film structure on the positive electrode of the electrochemical device, the SEI film formed on the negative electrode is not very stable, which is detrimental to the high-temperature cycling performance and high-temperature storage performance of the electrochemical device.

[0042] The inventors also discovered that if the electrolyte contains no more than 50 wt% of compound I, and also contains compound II: In this case, compound II will work together with compound I to form a low-impedance and highly stable SEI film on the negative electrode, inhibiting the reaction of compound I on the negative electrode. This not only ensures that the cycle performance and storage performance of the electrochemical device are not affected at high temperatures, but may even improve them. In compound II, n is 0, 1, or 2, M is selected from C or O, and X is selected from... or R 21 R 22 Each is independently selected from H, , , , , Any of the following, R 21 and R 22 Not both selected from H, and X, R 21 and R 22 It contains at least one sulfur atom.

[0043] As shown above, based on the total mass of the electrolyte, the mass percentage of compound I is a%, where 1 ≤ a ≤ 50. Specifically, the mass percentage of compound I can be 1%, 2%, 4%, 7%, 10%, 15%, 20%, 25%, 30%, 40%, 50%, etc., or within a range consisting of any two of the above values, such as 10% to 30%.

[0044] In some other embodiments, based on the total mass of the electrolyte, the mass percentage of the compound of formula II in this application is b%, where 0.2 ≤ b ≤ 6, and 0.167 ≤ a / b ≤ 125. This compound of formula II exhibits a significant inhibitory effect on the reaction of the compound of formula I at the negative electrode, resulting in better storage performance and cycling performance of the electrochemical device at high temperatures. Specifically, the mass percentage of the compound of formula II can be 0.2%, 0.5%, 1%, 1.5%, 2%, 3%, 4%, 5%, 6%, or within any range of two of the above values. Specifically, a / b can be 0.167, 0.33, 0.4, 0.5, 0.67, 1, 1.33, 2, 4, 7, 10, 15, 20, 30, 40, 50, 100, 125, or within any range of two of the above values; for example, a / b can be any value from 0.5 to 20.

[0045] In addition, in order to make the inhibitory effect of compound II on the reaction of compound I at the negative electrode more obvious, and to further improve the storage performance and cycling performance of the electrochemical device at high temperature, the electrolyte in the embodiments of this application can meet at least one of the following conditions: (1) 2≤a≤10; (2) 0.5≤b≤4; (3) 0.5≤a / b≤20.

[0046] Specifically, in some embodiments of this application, the compound of formula I in the electrolyte component may include at least one of the following compounds:

[0047]

[0048] These Formula I compounds can better improve the cycling performance, storage performance and low-temperature load performance of electrochemical devices at high temperatures.

[0049] Specifically, in some embodiments of this application, the compound of formula II in the electrolyte component may include at least one of the following compounds:

[0050]

[0051] These Formula II compounds can work better with Formula I compounds to improve the cycling and storage performance of electrochemical devices at high temperatures.

[0052] In some embodiments of this application, the electrolyte further comprises ethylene carbonate and propylene carbonate, wherein the total mass percentage of ethylene carbonate and propylene carbonate is c%, based on the total mass of the electrolyte, and 10 ≤ c ≤ 50. Ethylene carbonate and propylene carbonate can improve the solubility of lithium salts in the electrolyte, thereby improving the ion concentration of the electrolyte and enhancing the low-temperature load-bearing performance of the electrochemical device. Specifically, the total mass percentage of ethylene carbonate and propylene carbonate can be 10%, 20%, 30%, 40%, 50%, etc., or within the range of any two of the above values, preferably 0.05 ≤ a / c ≤ 0.5.

[0053] In some embodiments of this application, the electrolyte further includes fluoroethylene carbonate, and the mass percentage of fluoroethylene carbonate is d% based on the total mass of the electrolyte, with a mass ratio of 0.05 ≤ a / d ≤ 50. Fluoroethylene carbonate can interact with compounds of Formula I and Formula II to form a stable and low-impedance SEI film on the surface of the negative electrode, which is beneficial for improving the interfacial performance of the electrochemical device, thereby enhancing its high-temperature cycling performance. Specifically, a / d can be 0.05, 0.1, 0.13, 0.2, 0.29, 0.67, 2, 2.5, 5, 10, 20, 30, 40, 50, etc., or within a range consisting of any two of the above values. More specifically, the content of fluoroethylene carbonate can be 3% to 15%, and the a / d range is 0.13 to 3.33, which is more conducive to improving the interfacial performance of the electrochemical device, thereby further enhancing its high-temperature cycling performance.

[0054] In some embodiments of this application, the electrolyte further includes lithium difluorophosphate, with the mass percentage of lithium difluorophosphate being e%, where 0.2 ≤ e ≤ 2, based on the total mass of the electrolyte. In this case, the lithium difluorophosphate in the electrolyte can work together with the compound of Formula II to form a protective film with low impedance on the positive electrode of the electrochemical device, thereby improving the low-temperature load-bearing performance of the electrochemical device. Specifically, the content of lithium difluorophosphate can be 0.2%, 0.5%, 0.7%, 1%, 1.5%, 2%, etc., or within a range consisting of any two of the above values.

[0055] In some embodiments of this application, the electrolyte further includes nitrile compounds, with the nitrile content at a mass percentage of f%, 1 ≤ f ≤ 8, based on the total mass of the electrolyte. In the electrolyte of this application, an appropriate amount of nitrile compounds can form a protective film on the positive electrode while essentially not damaging the negative electrode, thus reducing the capacity loss rate of the electrochemical device and improving its high-temperature cycling and storage performance. Specifically, in the embodiments of this application, the nitrile content can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, or within any two of the above values. Furthermore, in specific embodiments of this application, the nitrile compounds include at least one of dinitrile and trinitrile, and the mass percentage ratio of trinitrile to dinitrile is not greater than 4 based on the total mass of the electrolyte, which is beneficial for further improving the high-temperature storage and cycling performance of the electrochemical device. Specifically, dinitrile includes at least one of butadienenitrile, adiponitrile, glutaronitrile, and heptanilide, and trinitrile includes at least one of 1,3,6-propanetrionitrile and 1,2,3-tris(2-cyanoxy)propane.

[0056] Positive electrode sheet

[0057] The positive electrode includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector. Specifically, in this application, the positive active material layer can be disposed on one surface or on two surfaces along the thickness direction of the positive current collector. Furthermore, in this application, the "surface of the positive current collector" can be the entire area of ​​the positive current collector or a portion of it; there are no particular limitations, as long as the purpose of this application is achieved.

[0058] [Amended according to Rule 26, 10.09.2025] The components of the positive electrode active material layer include the positive electrode active material, which can be any substance capable of reversibly intercalating and deintercalating Li. + Na + Substances containing alkali metal ions are used to ensure the normal charging and discharging of the electrochemical device. For example, positive electrode active materials include, but are not limited to, at least one of lithium iron phosphate (LiFePO4), lithium cobalt oxide (LiCoO2), lithium manganese oxide, lithium nickel oxide, and ternary materials. Ternary materials include, but are not limited to, LiNi x Co y Mn z O2, LiNi x Co y Al z At least one of O2, etc., and the contents of Ni, Co, Mn, Al, etc., can be adjusted to ensure that x+y+z=1. For example, the ternary material can be LiNi. 0.6 Co 0.2 Mn 0.2O2, LiNi 0.88 Co 0.08 Mn 0.04 O2, LiNi 0.8 Co 0.15 Mn 0.05 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.88 Co 0.1 Mn 0.02 O2, LiNi 0.8 Co 0.15 Al 0.05 O2, LiNi 0.88 Co 0.1 Al 0.02 O2, etc.

[0059] In some embodiments, the positive electrode active material layer further includes a positive electrode conductive agent; this application does not limit the type of positive electrode conductive agent, and any known conductive material can be used. Specifically, the positive electrode conductive agent includes, but is not limited to, at least one of the following: acetylene black, Super-P carbon black, or amorphous carbon such as needle coke, or carbon nanotubes, or graphene.

[0060] In some embodiments, the positive electrode active material layer generally also contains a positive electrode binder. There are no particular restrictions on the type of positive electrode binder used in the manufacture of the positive electrode active material layer. In the case of the coating method, any material that can be dissolved or dispersed in the liquid medium used in the electrode manufacturing process is acceptable. Positive electrode binders include, but are not limited to, any one or at least two of the following: resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose; rubber-like polymers such as styrene-butadiene rubber (SBR), nitrile rubber (NBR), fluororubber, isoprene rubber, polybutadiene rubber, and ethylene-propylene rubber; thermoplastic elastomers such as styrene-butadiene-styrene block copolymers or their hydrides, ethylene-propylene-diene terpolymers (EPDM), styrene-ethylene-butadiene-ethylene copolymers, and styrene-isoprene-styrene block copolymers or their hydrides; soft resin-like polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymers, and propylene-α-olefin copolymers; fluorinated polymers such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene-ethylene copolymers; and polymer compositions with ion conductivity of alkali metal ions (especially lithium ions).

[0061] In the positive electrode sheet, there are no particular restrictions on the type of positive current collector; it can be any known material suitable for use as a positive current collector. Materials for the positive current collector include, but are not limited to, metals such as aluminum, stainless steel, nickel plating, titanium, and tantalum. Furthermore, to reduce the electronic contact resistance between the positive current collector and the positive active material layer, conductive additives or conductive coatings can be applied to the surface of the positive current collector. Conductive additives include, but are not limited to, carbon and precious metals such as gold, platinum, and silver. The conductive coating can be a mixture of inorganic oxides, conductive agents, and positive electrode binders.

[0062] In preparing the positive electrode sheet, the components of the aforementioned positive active material layer can be dissolved or dispersed in a liquid solvent to form a positive electrode slurry. This slurry is then coated onto a positive current collector and dried, thereby forming the positive active material layer on the current collector, thus obtaining the positive electrode sheet. When preparing the positive electrode sheet using this method, there are no particular limitations on the solvent in the positive electrode slurry, as long as it can dissolve or disperse the aforementioned components. Specifically, the solvent in the positive electrode slurry includes, but is not limited to, N-methylpyrrolidone (NMP) and ethylene carbonate (EC). Alternatively, in preparing the positive electrode sheet, the components of the positive active material layer can be dry-mixed to form a sheet, which is then pressed onto the positive current collector.

[0063] Negative electrode sheet

[0064] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. The composition of the negative electrode active material layer includes the negative electrode sheet active material. That is, in this application, the negative electrode active material layer can be disposed on one surface or on two surfaces in the thickness direction of the negative electrode current collector. Moreover, in this application, the "surface of the negative electrode current collector" can be the entire area of ​​the negative electrode current collector or a part of the negative electrode current collector. This application has no particular limitation, as long as the purpose of this application can be achieved.

[0065] The negative electrode active material layer generally contains a negative electrode active material, and this application does not impose any particular limitation on the negative electrode active material. Specifically, the negative electrode active material may include at least one of carbon materials or silicon-based materials. More specifically, carbon materials include, but are not limited to, at least one of natural graphite, artificial graphite, mesophase microcarbon spheres, hard carbon, or soft carbon; silicon-based materials include, but are not limited to, at least one of silicon, silicon-oxygen composite materials, or silicon-carbon composite materials.

[0066] In some embodiments, the negative electrode active material layer typically also contains a negative electrode conductive agent. This application does not particularly limit the type of negative electrode conductive agent, as long as it achieves the purpose of this application. For example, negative electrode conductive agents include, but are not limited to, at least one of acetylene black, Ketjen black, carbon nanotubes, carbon fibers, carbon dots, or graphene.

[0067] In some embodiments, the negative electrode active material layer may also contain a negative electrode binder and a thickener. This application does not impose any particular limitation on the types of negative electrode binders and thickeners, as long as they can achieve the purpose of this application. For example, the negative electrode binder may include, but is not limited to, at least one of polyvinyl alcohol, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, styrene-butadiene rubber, or acrylated styrene-butadiene rubber; the thickener in the negative electrode slurry may include, but is not limited to, at least one of sodium carboxymethyl cellulose or lithium carboxymethyl cellulose.

[0068] In the negative electrode sheet, the material of the negative electrode current collector includes, but is not limited to, copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or a polymer substrate coated with a conductive metal, etc., and this application does not have any particular limitations. Among them, the conductive metal includes, but is not limited to, copper, nickel, or titanium, and the material of the polymer substrate includes, but is not limited to, at least one of polyethylene, polypropylene, ethylene propylene copolymer, polyethylene terephthalate, polyethylene terephthalate, or poly(p-phenylene terephthalamide).

[0069] Furthermore, this application does not impose any particular limitations on the thickness of the negative electrode current collector and the negative electrode active material layer, as long as the purpose of this application can be achieved. For example, the thickness of the negative electrode current collector is 4 μm to 12 μm, and the thickness of the single-sided negative electrode active material layer is 30 μm to 160 μm.

[0070] Furthermore, similar to the preparation of the positive electrode sheet, the preparation of the negative electrode sheet can be achieved either by preparing a negative electrode slurry, coating the slurry onto a negative electrode current collector, and drying it to form a negative electrode active material layer on the current collector, thus obtaining the negative electrode sheet; or by dry mixing the components of the negative electrode active material layer to form a sheet, which is then pressed onto the negative electrode current collector to form the negative electrode active material layer, thereby obtaining the negative electrode sheet. The solvent in the negative electrode slurry includes any one of aqueous solvents and organic solvents. Aqueous solvents include, but are not limited to, mixtures of alcohol and water or water itself. Organic solvents include, but are not limited to, aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N,N-dimethylaminopropylamine; ethers such as diethyl ether, propylene oxide, and tetrahydrofuran (THF); amides such as N-methylpyrrolidone (NMP), dimethylformamide, and dimethylacetamide; and aprotic polar solvents such as hexamethylphosphoramide and dimethyl sulfoxide. In some other embodiments, when using aqueous solvents, the negative electrode slurry composition may also include a thickener and styrene-butadiene rubber (SBR) emulsion to slurry the negative electrode slurry, thereby adjusting its viscosity. The types of thickeners in the positive electrode slurry include, but are not limited to, at least one of carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and their salts.

[0071] Separating membrane

[0072] To prevent short circuits, a separator is typically placed between the positive and negative electrodes. In this case, the electrolyte of this application is typically used after penetrating into the separator.

[0073] There are no particular limitations on the material and shape of the separator, as long as it does not significantly impair the effectiveness of this application. The separator material can be resin, glass fiber, inorganic materials, etc., formed from materials stable to the electrolyte of this application. In some embodiments, the separator includes a porous sheet or non-woven fabric-like material with excellent liquid retention properties. Examples of resin or glass fiber separator materials include, but are not limited to, polyolefins, aromatic polyamides, polyimide (PI), polyamide (PA), polytetrafluoroethylene, polyethersulfone, spandex, or aramid. In some embodiments, the polyolefin is polyethylene or polypropylene. In some embodiments, the polyolefin is polypropylene. The above-mentioned separator materials can be used alone or in any combination.

[0074] The separator can also be a material formed by laminating the above-mentioned materials, examples of which include, but are not limited to, a three-layer separator formed by laminating polypropylene, polyethylene, and polypropylene in that order.

[0075] Inorganic materials include, but are not limited to, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates (e.g., barium sulfate, calcium sulfate, etc.). The forms of inorganic materials include, but are not limited to, particulate or fibrous forms.

[0076] The separator can be in the form of a thin film, including but not limited to non-woven fabric, woven fabric, and microporous membranes. In the thin film form, the pore size of the separator is 0.01 μm to 1 μm, and the thickness is 5 μm to 50 μm. In addition to the above-mentioned independent thin film separators, the following separators can also be used: separators formed by using a resin-based adhesive to form a composite porous layer containing the above-mentioned inorganic particles on the surface of the positive electrode and / or negative electrode, for example, a separator formed by using fluororesin as an adhesive to form a porous layer of alumina particles with a particle size of less than 1 μm on both sides of the positive electrode.

[0077] The thickness of the separator is arbitrary. In some embodiments, the thickness of the separator is greater than 1 μm, greater than 5 μm, or greater than 8 μm. In some embodiments, the thickness of the separator is less than 50 μm, less than 40 μm, or less than 30 μm. When the thickness of the separator is within the above ranges, insulation and mechanical strength can be ensured, and the rate capability and energy density of the electrochemical device can be ensured.

[0078] 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).

[0079] The electrochemical device of this application also includes a packaging bag for containing the positive electrode, the separator, the negative electrode, and the 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.

[0080] Secondly, this application also provides an electronic device that includes an electrochemical device according to this application.

[0081] The application of the electrochemical device in this application is not particularly limited, and it can be used in any electronic device known in the prior art. In some embodiments, the electrochemical device of this application can be used in, 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, household large-capacity batteries, and lithium-ion capacitors, etc.

[0082] Example

[0083] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0084] Test methods and equipment:

[0085] Cyclic performance test:

[0086] <Performance and Preparation of Electrochemical Devices>

[0087] High temperature (45℃) cycle performance test

[0088] The cycling performance of an electrochemical device is evaluated by the capacity retention rate after 400 cycles at 45°C. A higher capacity retention rate after 400 cycles at 45°C indicates better cycling performance of the electrochemical device.

[0089] The electrochemical device was placed in a 45°C constant temperature chamber and allowed to stand for 30 minutes to reach a constant temperature. The device was then charged at a constant current of 0.2C to 4.5V at 45°C, followed by a constant voltage charge at 4.5V to 0.05C. After standing for 5 minutes, it was discharged at a constant current of 0.2C to 3.0V and allowed to stand for 5 minutes. The initial discharge capacity C0 of the electrochemical device was then measured. Next, it was charged at a constant current of 1.8C to 4.15V, followed by a constant voltage charge at 4.15V to 1C. It was then charged at a constant current of 1C to 4.25V, followed by a constant voltage charge at 4.25V to 0.8C. It was then charged at a constant current of 0.8C to 4.5V, followed by a constant voltage charge at 4.5V to 0.05C. After standing for 5 minutes, it was discharged at a constant current of 1C to 3.0V and allowed to stand for 5 minutes. This completes one charge-discharge cycle. The electrochemical device was cycled 400 times according to the above charging / discharging cycle steps, and the discharge capacity C1 after 400 cycles was measured.

[0090] Capacity retention rate after 400 cycles at 45℃ = C1 / C0 × 100%.

[0091] High-temperature (80℃) storage performance test

[0092] The electrochemical device, i.e., the battery, is charged to 4.5V at a constant current of 1.8C at room temperature (25℃), and then charged to the cutoff current of 0.02C at a constant voltage of 4.5V. The thickness is measured at five different points, and the average of the five measurements is recorded as the initial thickness L1. The electrochemical device is then placed in an 80℃ oven and left to stand for 7 hours. Subsequently, the battery thickness is measured at five different points, and the average of the five measurements is recorded as L2. The thickness growth rate is calculated as (L2 / L1-1)×100%.

[0093] The smaller the thickness growth rate, the better the high-temperature storage performance.

[0094] Low-temperature (-20℃) tensile performance test

[0095] The electrochemical device was charged to 4.5V at 0.2C at 25℃, then charged to the cutoff current of 0.02C at a constant voltage of 4.5V, and then discharged at a constant current of 0.2C for 4 hours. The temperature was then adjusted to -20℃ and held for 30 minutes. The device was then discharged at 0.4C for 1 second and 0.1C for 2 seconds. The process of "discharging at 0.4C for 1 second and discharging at 0.1C for 2 seconds" was repeated until the voltage dropped below 3V. The number of cycles at this point was recorded as the low-temperature load count.

[0096] A higher low-temperature load number indicates better low-temperature discharge performance; specific data on the low-temperature load performance of the electrochemical devices in each embodiment and comparative example are shown in the table.

[0097] Example 1-1

[0098] <Preparation of Electrolyte>

[0099] In an argon-atmospheric glove box with a water content of <10 ppm, methyl ethyl carbonate and ethyl acetate were mixed at a mass ratio of 1:1 to prepare a base solvent. Then, lithium hexafluorophosphate (LiPF6), compound I, and compound II were added to form an electrolyte. Based on the total mass of the electrolyte, the mass percentage of LiPF6 was 12.5%, and the mass percentages of compounds I and II are shown in Table 1. The remainder was the base solvent.

[0100] In addition, the compounds referred to by the codes in the table can be found in the above content of this article.

[0101] <Preparation of the positive electrode>

[0102] Lithium cobalt oxide, conductive carbon black, and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 95:2:3. N-methylpyrrolidone (NMP) was added, and the mixture was stirred evenly under vacuum to obtain a positive electrode slurry with a solid content of 70 wt%. The positive electrode slurry was uniformly coated on the upper and lower surfaces of a 9 μm thick aluminum foil for the positive electrode current collector. After drying and pressure treatment, the foil was cut into the specified size to obtain the positive electrode sheet.

[0103] <Preparation of Negative Electrode Sheets>

[0104] Artificial graphite, styrene-butadiene rubber (SBR), polyacrylic acid (PAA), carbon nanotubes (CNTs): carboxymethyl cellulose (CMC) were mixed in a mass ratio of 95.8:2.4:0.5:0.5:0.8. Deionized water was then added as a solvent and the mixture was stirred until homogeneous, resulting in a negative electrode slurry with a solid content of 45 wt%. The negative electrode slurry was uniformly coated onto the upper and lower surfaces of a 6 μm thick copper foil current collector. After drying and pressure treatment, the foil was cut into specified sizes to obtain the negative electrode sheet.

[0105] <Isolation membrane>

[0106] A porous polyethylene film with a thickness of 15μm was used as the separator.

[0107] <Preparation of Electrochemical Devices>

[0108] The prepared positive electrode, separator, negative electrode, and separator are stacked in sequence, with the separator positioned between the positive and negative electrodes to act as a separator. The electrodes are then wound to obtain the electrode assembly. After welding the tabs, the electrode assembly is placed in an aluminum-plastic film packaging bag and dried in an 85°C vacuum oven for 12 hours to remove moisture. The prepared electrolyte is then injected, and the battery undergoes vacuum sealing, settling, formation, shaping, and capacity testing to obtain a lithium-ion battery (i.e., an electrochemical device).

[0109] Examples 1-2 to Examples 1-10

[0110] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as in Examples 1-1. Specifically, when the mass percentage of compound I changes, the mass percentage of lithium salt remains unchanged.

[0111] Examples 1-11 to Examples 1-18

[0112] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as in Examples 1-2. Specifically, when the mass percentage of compound II changes, the mass percentage of lithium salt remains unchanged.

[0113] Examples 1-19

[0114] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as in Examples 1-1. However, when the mass percentage of compound II changes, the mass percentage of lithium salt remains unchanged.

[0115] Examples 1-20

[0116] Except for adjustments to the preparation methods described in Table 1, the rest of the process is the same as in Examples 1-12. Note that the mass percentage of lithium salt remains constant when the mass percentage of compound I changes.

[0117] Examples 1-21

[0118] Except for adjustments to the preparation methods described in Table 1, the rest of the process is the same as in Examples 1-11. Note that the mass percentage of lithium salt remains constant when the mass percentage of compound I changes.

[0119] Examples 1-22 to Examples 1-28

[0120] Except for adjusting the relevant preparation descriptions according to Table 1, the rest is the same as in Examples 1-2.

[0121] Table 1

[0122]

[0123] Examples 2-1 to 2-5

[0124] Except for the addition of ethylene carbonate and propylene carbonate in the <Electrolyte Preparation> section and the adjustment of the relevant preparation parameters according to Table 2, the rest is the same as in Examples 1-2. The mass percentage of LiPF6 remains unchanged when the mass percentages of ethylene carbonate and propylene carbonate change.

[0125] Examples 2-6

[0126] Except for the addition of ethylene carbonate and propylene carbonate in the <Preparation of Electrolyte> and the adjustment of the relevant preparation parameters according to Table 2, the rest is the same as in Examples 1-5.

[0127] Table 2

[0128]

[0129] Examples 3-1 to 3-15

[0130] Except for the addition of fluoroethylene carbonate and adjustment of the relevant preparation parameters according to Table 3 in the <Preparation of Electrolyte> section, the rest is the same as in Examples 1-2. The mass percentage of LiPF6 remains unchanged when the mass percentages of Formula I compound and fluoroethylene carbonate change.

[0131] Table 3

[0132]

[0133] Examples 4-1 to 4-6

[0134] Except for the addition of lithium difluorophosphate and adjustment of the relevant preparation parameters according to Table 4 in the <Electrolyte Preparation> section, the rest is the same as in Examples 1-2. The mass percentage of LiPF6 remains unchanged when the mass percentage of lithium difluorophosphate changes.

[0135] Table 4

[0136]

[0137] Examples 5-1 to 5-13

[0138] Except for the addition of nitrile compounds and adjustment of the relevant preparation parameters according to Table 5 in the <Electrolyte Preparation> section, the rest is the same as in Examples 1-2. The mass percentage of LiPF6 remains unchanged when the mass percentage of nitrile compounds changes.

[0139] Table 5

[0140]

[0141] Comparative Example 1

[0142] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as in Examples 1-11. The content of LiPF6 remains unchanged when the mass percentage of compound I changes.

[0143] Comparative Example 2

[0144] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as in Examples 1-10. The content of LiPF6 remains unchanged when the mass percentage of compound I changes.

[0145] Referring to Table 1, as can be seen from the examples and comparative examples, in the electrochemical device of this application, when the electrolyte contains both Formula II compound and 1% to 50% Formula I compound, the electrochemical device exhibits excellent high-temperature cycling and storage performance, as well as good low-temperature load-bearing performance. In particular, when the mass percentage of Formula I compound is 2% to 10%, the mass percentage of Formula II compound is 0.5% to 4%, and the mass percentage ratio of Formula I compound to Formula II compound is between 0.5 and 20, the high-temperature storage performance and high-temperature cycling performance of the electrochemical device are further improved.

[0146] Referring to Table 2, it can be seen from Examples 1-2, 2-5 to 2-4 that when the total mass percentage of ethylene carbonate and propylene carbonate is between 10% and 50%, it can be combined with compounds of Formula I and Formula II to better improve the low-temperature load-bearing performance of the electrochemical device.

[0147] Referring to Table 3, it can be seen from Examples 1-2, 3-1 to 3-15 that when the electrolyte contains fluoroethylene carbonate (content d%) and a / d is 0.05~50, fluoroethylene carbonate can work together with compounds of Formula I and Formula II to improve the high-temperature cycling performance of the electrochemical device; when 3≤d≤15 and 0.13≤a / d≤3.33, the improvement in the high-temperature cycling performance of the electrochemical device is more significant.

[0148] Referring to Table 4, as can be seen from Examples 1-2, 3-1 to 3-5, lithium difluorophosphate and the compound of formula II work together to form a protective film with low impedance on the positive electrode of the electrochemical device, thereby further improving the low-temperature load performance of the electrochemical device.

[0149] Referring to Table 5, as shown in Examples 1-2 and 4-1 to 4-13, when the electrolyte in the electrochemical device simultaneously contains compounds of Formula I, Formula II, and nitriles, the high-temperature cycling performance and high-temperature storage performance of the electrochemical device can be further improved. In particular, when the electrolyte simultaneously contains dinitrile and trinitrile, and the mass ratio of trinitrile to dinitrile is not greater than 4, the improvement in high-temperature storage performance and cycling performance is especially significant.

[0150] The above are merely embodiments of this application and are not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. An electrochemical device comprising a positive electrode, a negative electrode, and an electrolyte, characterized in that, The electrolyte comprises a compound of formula I and a compound of formula II, wherein the compound of formula I is: R is selected from any one of fluorinated or unsubstituted C2-C6 alkyl, C6-C12 nitrogen-containing heterocyclic group, and fluorinated or unsubstituted C6-C12 aryl group; The compound of formula II is: Where n is 0, 1, or 2, M is selected from C or O, and X is selected from... or R 21 R 22 Each is independently selected from H, 、 、 、 、 Any of the following, R 21 and R 22 Not simultaneously selected from H, and X, R 21 and R 22 It contains at least one sulfur atom; Based on the total mass of the electrolyte, the mass percentage of the compound of formula I is a%, 1≤a≤50.

2. The electrochemical device according to claim 1, characterized in that, Based on the total mass of the electrolyte, the mass percentage of the compound of formula II is b%, 0.2≤b≤6, and 0.167≤a / b≤125.

3. The electrochemical device according to claim 2, characterized in that, The electrolyte satisfies at least one of the following conditions: （1）2≤a≤10； （2）0.5≤b≤4； (3) 0.5≤a / b≤20.

4. The electrochemical device according to claim 1, characterized in that, The compound of formula I includes at least one of the following compounds:

5. The electrochemical device according to claim 1, characterized in that, The compound of formula II includes at least one of the following compounds:

6. The electrochemical device according to claim 1, characterized in that, The electrolyte also includes ethylene carbonate and propylene carbonate, and the total mass percentage of ethylene carbonate and propylene carbonate is c%, based on the total mass of the electrolyte, with 10 ≤ c ≤ 50.

7. The electrochemical device according to claim 6, characterized in that, 0.05≤a / c≤0.

5.

8. The electrochemical device according to claim 1, characterized in that, The electrolyte also includes fluoroethylene carbonate, and the mass percentage of fluoroethylene carbonate is d% based on the total mass of the electrolyte, 0.05≤a / d≤50.

9. The electrochemical device according to claim 8, characterized in that, 3≤d≤15, and 0.13≤a / d≤3.

33.

10. The electrochemical device according to claim 2, characterized in that, The electrolyte also includes lithium difluorophosphate, and the mass percentage of lithium difluorophosphate is e% based on the total mass of the electrolyte, with a content of 0.2 ≤ e ≤ 2.

11. The electrochemical device according to claim 2, characterized in that, The electrolyte also includes nitriles, and the mass percentage of the nitriles is f% based on the total mass of the electrolyte, 1≤f≤8%.

12. The electrochemical device according to claim 11, characterized in that, The nitrile includes at least one of dinitrile and trinitrile, and the mass percentage ratio of the trinitrile to the dinitrile is not greater than 4 based on the total mass of the electrolyte.

13. The electrochemical device according to claim 12, characterized in that, The dinitrile includes at least one of butadionitrile, adiponitrile, glutaronitrile, and heptanonitrile; and / or, the trinitrile includes at least one of 1,3,6-propanetrionitrile and 1,2,3-tris(2-cyanoxy)propane.

14. An electronic device, characterized in that, It includes the electrochemical device according to any one of claims 1 to 13.

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