Electrolyte, electrochemical device, and electronic device

Abstract

Embodiments of this disclosure provide an electrolyte, an electrochemical device, and an electronic device. The electrolyte comprises a compound represented by Formula I, in which R1, R2, and R3 are each independently selected from any one of substituted or unsubstituted C1-C4 alkyl, substituted or unsubstituted C2-C4 alkenyl, and heteroatoms, wherein the heteroatoms include at least one of O, S, and N atoms, and when substituted, the substituents include at least one of F, sulfonyl, cyano, and alkoxy; R4 is selected from any one of substituted or unsubstituted C1-C4 alkyl, N, P, and B atoms, wherein when substituted, the substituents include at least one of C2-C4 alkenyl, C2-C4 alkynyl, F atoms and their derivatives, sulfonyl, cyano, and alkoxy; and X1 is selected from any one of P atoms, B atoms, and groups containing P or B.

Description

Technical Field

[0001] The exemplary embodiments disclosed herein generally relate to the field of energy storage technology, and particularly to an electrolyte, an electrochemical device, and an electronic device. Background Technology

[0002] With the rapid depletion of fossil fuels and the intensification of the greenhouse effect, lithium-ion batteries, as a new type of energy storage device, are a crucial form of future energy supply. Lithium-ion batteries possess advantages such as high energy density, low memory effect, environmental friendliness, and long lifespan, leading to their increasingly widespread application in electrochemical energy storage. Particularly in the automotive industry, the two most pressing requirements for electric vehicle power batteries are fast charging capability and high safety. Currently, the mainstream strategy for improving the fast charging capability of power batteries is to use high-kinetic electrolytes; however, this often leads to a significant deterioration in cycle life and high-temperature characteristics. Furthermore, flame-retardant electrolytes are also a current industry focus on improving cell safety, but this results in a significant increase in cell impedance, causing a sharp decline in cycle life.

[0003] Therefore, there is an urgent need to develop a solution that simultaneously balances the fast charging capability and high safety of lithium-ion batteries. Summary of the Invention

[0004] The purpose of this disclosure is to provide an electrolyte, an electrochemical device, and an electronic device to at least partially solve the aforementioned problems existing in the prior art.

[0005] According to a first aspect of this disclosure, an electrolyte is provided comprising a compound represented by formula I.

[0006]

[0007] In equation I,

[0008] R1, R2 and R3 are each independently selected from any one of substituted or unsubstituted C1-C4 alkyl, substituted or unsubstituted C2-C4 alkenyl, and heteroatoms, wherein the heteroatoms include at least one of O, S and N atoms, and when substituted, the substituents include at least one of F, sulfonyl, cyano and alkoxy.

[0009] R4 is selected from any one of substituted or unsubstituted C1-C4 alkyl, N, P, and B atoms, wherein when substituted, the substituent includes at least one of C2-C4 alkenyl, C2-C4 alkynyl, F atom and its derivatives, sulfonyl, cyano, and alkoxy; and

[0010] X1 is selected from any one of P atoms, B atoms, and groups containing P or B.

[0011] In some embodiments, the compound represented by Formula I includes at least one of the compounds represented by Formulas I-1 to I-8:

[0012]

[0013] In some embodiments, the mass percentage of the compound represented by Formula I is 0.1%-2% based on the total mass of the electrolyte.

[0014] In some embodiments, the electrolyte further comprises a compound represented by Formula II.

[0015]

[0016] In Formula II, R5 is selected from any one of substituted or unsubstituted C1-C4 alkyl, C2-C4 alkenyl, C2-C4 alkynyl, O atom, S atom and N atom, wherein when substituted, the substituent includes at least one of F atom, sulfonyl and cyano.

[0017] In some embodiments, the compound represented by Formula II includes at least one of the compounds represented by Formulas II-1 to II-8:

[0018]

[0019] In some embodiments, the total mass percentage of the compound represented by Formula I and the compound represented by Formula II is 0.01%-20% based on the total mass of the electrolyte.

[0020] In some embodiments, the mass percentage of the compound represented by Formula I is 0.1%-2% based on the total mass of the electrolyte.

[0021] In some embodiments, the mass percentage of the compound represented by Formula II is 0.1%-5% based on the total mass of the electrolyte.

[0022] According to a second aspect of this disclosure, an electrochemical device is provided, comprising a positive electrode, a negative electrode, a separator, and an electrolyte according to a first aspect of this disclosure.

[0023] According to a third aspect of this disclosure, an electronic device is provided, including an electrochemical device according to a second aspect of this disclosure.

[0024] In embodiments according to this disclosure, by introducing additives such as compounds of Formula I and optionally compounds of Formula II into the electrolyte, fast ion transport channels can be formed at the electrode interface during cell fabrication, thereby significantly reducing the cell impedance. Furthermore, these fast ion transport channels exhibit good thermal and voltage stability at high temperatures, suppressing high-temperature, high-voltage gas generation and inhibiting the cell's self-heating rate during thermal abuse.

[0025] This content section is provided to present the selection of concepts in a simplified form, which will be further described in the detailed embodiments below. This content section is not intended to identify key or primary features of this disclosure, nor is it intended to limit the scope of this disclosure. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this disclosure clearer, the technical solutions of this disclosure will be clearly and completely described below in conjunction with exemplary embodiments. It should be understood that the described embodiments are only some, not all, of the embodiments of this disclosure. The embodiments described herein are illustrative in nature and are intended to provide a basic understanding of this disclosure. The embodiments of this disclosure should not be construed as limiting this disclosure. All other embodiments obtained by those skilled in the art based on the technical solutions and embodiments provided in this disclosure without inventive effort are within the scope of protection of this disclosure.

[0027] In this document, a list of items connected by the terms "any one of," "any of," "any of," or other similar terms may mean any one of the listed items. For example, if items A and B are listed, the phrase "any one of A and B" means either A only or B only. In another instance, if items A, B, and C are listed, the phrase "any one of A, B, and C" means either A only; B only; or C only. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0028] In this document, a list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another instance, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0029] In this article, for simplicity, "Cn-Cm" groups refer to groups having "n" to "m" carbon atoms, where "n" and "m" are integers. For example, "C1-C10" alkyl groups refer to alkyl groups having 1 to 10 carbon atoms.

[0030] In this document, the term "alkyl" is contemplated as a straight-chain saturated hydrocarbon structure having 1 to 20 carbon atoms. "alkyl" is also contemplated as a branched or cyclic hydrocarbon structure having 3 to 20 carbon atoms. For example, an alkyl group can be an alkyl group with 1 to 20 carbon atoms, an alkyl group with 1 to 10 carbon atoms, an alkyl group with 1 to 5 carbon atoms, an alkyl group with 5 to 20 carbon atoms, an alkyl group with 5 to 15 carbon atoms, or an alkyl group with 5 to 10 carbon atoms. When an alkyl group with a specific number of carbon atoms is specified, it is contemplated to cover all geometric isomers having that number of carbon atoms; thus, for example, "butyl" means including n-butyl, sec-butyl, isobutyl, tert-butyl, and cyclobutyl; "propyl" includes n-propyl, isopropyl, and cyclopropyl. Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl, n-pentyl, isopentyl, neopentyl, cyclopentyl, methylcyclopentyl, ethylcyclopentyl, n-hexyl, isohexyl, cyclohexyl, n-heptyl, octyl, cyclopropyl, cyclobutyl, norbornyl, etc. Additionally, the alkyl group may optionally be substituted or unsubstituted.

[0031] In this document, the term "alkenyl" refers to a monovalent unsaturated hydrocarbon group that may be straight-chain or branched and has at least one, typically one, two, or three carbon-carbon double bonds. Unless otherwise defined, the alkenyl group typically contains 2 to 20 carbon atoms, for example, it may be an alkenyl group with 2 to 20 carbon atoms, an alkenyl group with 6 to 20 carbon atoms, an alkenyl group with 2 to 10 carbon atoms, or an alkenyl group with 2 to 6 carbon atoms. Representative alkenyl groups include, for example, vinyl, n-propenyl, isopropenyl, n-but-2-enyl, but-3-enyl, n-hex-3-enyl, etc. Additionally, the alkenyl group may optionally be substituted or unsubstituted.

[0032] In this document, the term "alkenyl" encompasses both straight-chain and branched alkenyl groups. When an alkenyl group with a specific number of carbon atoms is specified, it is intended to cover all geometric isomers of that number of carbon atoms. For example, an alkenyl group can be an alkenyl group with 2 to 20 carbon atoms, an alkenyl group with 2 to 15 carbon atoms, an alkenyl group with 2 to 10 carbon atoms, an alkenyl group with 2 to 5 carbon atoms, an alkenyl group with 5 to 20 carbon atoms, an alkenyl group with 5 to 15 carbon atoms, or an alkenyl group with 5 to 10 carbon atoms. Representative alkylene groups include, for example, vinylene, propenylene, butenylene, etc. Additionally, the alkenyl group may optionally be substituted or unsubstituted.

[0033] In this document, the term "alkynyl" refers to a monovalent unsaturated hydrocarbon group that may be straight-chain or branched and has at least one, and typically one, two, or three, carbon-carbon triple bonds. Unless otherwise defined, the alkynyl group typically contains 2 to 20 carbon atoms, for example, it may be an alkynyl group with 2 to 20 carbon atoms, an alkynyl group with 6 to 20 carbon atoms, an alkynyl group with 2 to 10 carbon atoms, or an alkynyl group with 2 to 6 carbon atoms. Representative alkynyl groups include, for example, ethynyl, propynyl-2-alkynyl (n-propynyl), n-butynyl, n-hexyl-3-alkynyl, etc. Additionally, the alkynyl group may optionally be substituted or unsubstituted.

[0034] In this document, the term "heteroatom" refers to an atom other than C and H. For example, a heteroatom may contain at least one of B, N, O, Si, P, and S.

[0035] In this paper, the term "cyano" covers organic compounds containing the organic group -CN.

[0036] In this document, the term "alkoxy" refers to the LO group, where L is an alkyl group. The alkoxy group in this document may be an alkoxy group with 1 to 12 carbon atoms, or it may be an alkoxy group with 1 to 10 carbon atoms, an alkoxy group with 1 to 5 carbon atoms, an alkoxy group with 5 to 12 carbon atoms, or an alkoxy group with 5 to 10 carbon atoms.

[0037] As described above, the two most pressing needs for electric vehicles' power batteries are fast charging capability and high safety.

[0038] To address the fast charging issue, the industry has made numerous efforts, such as employing low-doping coating materials and optimizing particle size for the cathode, and introducing highly kinetic solvents (e.g., ethyl methyl carbonate, dimethyl carbonate) for the electrolyte. Among these, using highly kinetic solvents has the most significant effect on improving the fast charging capability of the battery cell. However, due to the high reactivity of these solvents, the cycle performance and high-temperature storage performance of the battery cell often deteriorate significantly. Using low-doping coating materials also faces similar problems.

[0039] Furthermore, for high-safety battery cells, much of the current industry research focuses on flame-retardant electrolytes. Flame-retardant electrolytes often use additives or solvents containing free radical quenching groups. These additives and solvents have poor compatibility with negative electrode materials, leading to a significant decrease in cycle performance and kinetic performance.

[0040] To address the aforementioned problems in the prior art, embodiments of this disclosure provide an electrolyte.

[0041] Electrolyte

[0042] The electrolyte in embodiments of this disclosure comprises an organic solvent, an electrolyte, and additives.

[0043] I. Organic solvents

[0044] In the embodiments according to this disclosure, there are no specific limitations on the type of organic solvent, which can be selected and customized according to system requirements. For example, a non-aqueous organic solvent system can be used. The non-aqueous organic solvent system can include any type of carbonate, carboxylic acid ester, nitrile, sulfone, and ether solvent. Carbonates can include cyclic carbonates and chain carboxylic acid esters, and their halogenated derivatives, or mixtures of the two in any proportion. Specifically, the organic solvent can be selected from at least one of ethylene carbonate, propylene carbonate, butene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl carbonate, ethyl formate, ethyl formate, ethyl acetate, propyl propionate, ethyl propionate, γ-butyrolactone, and tetrahydrofuran. It should be understood that various other types of organic solvents are also feasible, and the scope of this disclosure is not strictly limited in this respect.

[0045] II. Electrolytes

[0046] In embodiments according to this disclosure, the electrolyte may be of various available types, such as a solid electrolyte, a gel electrolyte, or a liquid electrolyte.

[0047] In one embodiment, when the electrolyte is a liquid electrolyte, the mass of the liquid electrolyte can be 5%-23% of the total mass of the electrolyte. Preferably, the mass of the liquid electrolyte can be 9%-16% of the total weight of the electrolyte. In one embodiment, the liquid electrolyte can be selected from at least one of lithium salts and sodium salts. There is no specific limitation on the type of lithium salt, which can be selected according to actual needs. Preferably, the lithium salt can include at least LiPF6. The lithium salt can further include at least one of LiBF4, LiClO4, LiAsF6, LiBOB, LiDFOB, LiFSI, LiTFSI, LiPO2F2, LiTFOP, LiN(SO2RF)2, and LiN(SO2F)(SO2RF), wherein RF = C n F2n+1 , where n represents a perfluoroalkyl group, and n is an integer from 1 to 10. There is no specific limitation on the type of sodium salt, which can be selected according to actual needs. Preferably, the sodium salt can be selected from at least one of NaPF6, NaBF4, NaClO, NaAsF6, NaCF3SO3, NaN(CF3SO2)2, NaN(C2F5SO2)2, and NaN(FSO2)2. In other embodiments, the liquid electrolyte can be of types other than lithium and sodium salts, and the scope of this disclosure is not strictly limited in this respect.

[0048] Similarly, in the embodiments according to this disclosure, there are no strict limitations on the types of solid electrolytes and gel electrolytes, and various conventional or future-available solid electrolytes and gel electrolytes are feasible.

[0049] III. Additives

[0050] In some embodiments, the additive includes a first additive, which is a compound represented by Formula I.

[0051]

[0052] In equation I,

[0053] R1, R2 and R3 are each independently selected from any one of substituted or unsubstituted C1-C4 alkyl, substituted or unsubstituted C2-C4 alkenyl, and heteroatoms, wherein the heteroatoms include at least one of O, S and N atoms, and when substituted, the substituents include at least one of F, sulfonyl, cyano and alkoxy.

[0054] R4 is selected from any one of substituted or unsubstituted C1-C4 alkyl, N, P, and B atoms, wherein when substituted, the substituent includes at least one of C2-C4 alkenyl, C2-C4 alkynyl, F atom and its derivatives, sulfonyl, cyano, and alkoxy; and

[0055] X1 is selected from any one of P atoms, B atoms, and groups containing P or B.

[0056] In some embodiments, the first additive comprises at least one of the compounds represented by formulas I-1 to I-8:

[0057]

[0058]

[0059] By adding a first additive to the electrolyte, the impedance of the battery cell can be significantly reduced, the cycle capacity retention rate can be improved, and the high-temperature storage performance can be enhanced.

[0060] In some embodiments, the mass percentage of the first additive is 0.1%-2% based on the total mass of the electrolyte.

[0061] In some embodiments, the electrolyte further comprises a second additive, which is a compound represented by Formula II.

[0062]

[0063] In Formula II, R5 is selected from any one of substituted or unsubstituted C1-C4 alkyl, C2-C4 alkenyl, C2-C4 alkynyl, O atom, S atom and N atom, wherein when substituted, the substituent includes at least one of F atom, sulfonyl and cyano.

[0064] In some embodiments, the second additive comprises at least one of the compounds represented by formulas II-1 to II-8:

[0065]

[0066]

[0067] By introducing a first additive and a second additive into the electrolyte, the first and second additives can work synergistically during the cell fabrication process to form a fast ion transport channel at the electrode interface, thereby significantly reducing the cell's impedance. Furthermore, this fast ion transport channel exhibits good thermal and voltage stability at high temperatures, suppressing gas generation at high temperatures and voltages, and inhibiting the cell's self-heating rate during thermal abuse.

[0068] In some embodiments, the total mass percentage of the first additive and the second additive is 0.01%-20% based on the total mass of the electrolyte.

[0069] In some embodiments, the mass percentage of the first additive is 0.1%-2% based on the total mass of the electrolyte.

[0070] In some embodiments, the mass percentage of the second additive is 0.1%-5% based on the total mass of the electrolyte.

[0071] When the mass of the first additive accounts for 0.1%-2% of the electrolyte and the mass of the second additive accounts for 0.1%-5% of the electrolyte, due to the coupling difference of the redox potential, the two can synergistically form a film on the positive and negative electrode surfaces. The interface film formed by the two is rich in fast ion conducting groups such as N and B, which can significantly reduce impedance. Moreover, the interface film formed by the two is relatively uniform and has good high-temperature stability, suppressing side reactions at high temperatures and suppressing the temperature rise associated with side reactions. Both the first and second additives can capture free Lewis acids, reducing the reactivity of the electrolyte itself.

[0072] IV. Preparation of Electrolyte

[0073] In some embodiments, the electrolyte can be prepared using the following process: In a dry argon glove box, an organic solvent, additives, and electrolyte are mixed in the desired amounts. Specifically, the organic solvent is first added to the dry argon glove box, followed by the additives. After dissolving and thoroughly stirring, the electrolyte is added and mixed evenly to obtain the electrolyte.

[0074] It should be understood that, in the embodiments according to this disclosure, electrolytes may also be prepared by other methods or under other conditions, and the scope of this disclosure is not strictly limited in this respect.

[0075] [Electrochemical device]

[0076] Embodiments of this disclosure provide an electrochemical device, such as a primary battery or a secondary battery. A secondary battery is, for example, a lithium-ion battery, a sodium-ion battery, a zinc-ion battery, or a supercapacitor. In the embodiments of this disclosure, a lithium-ion battery is used only as an example to illustrate the principles of this disclosure, but the scope of this disclosure is not limited thereto.

[0077] The electrochemical device includes the electrolyte of embodiments of this disclosure. Furthermore, the electrochemical device may also include a positive electrode, a negative electrode, a separator, and a housing, etc.

[0078] I. Positive Electrode

[0079] A positive electrode is a known type of positive electrode that can be used in electrochemical devices. In some embodiments, a positive electrode includes a positive current collector and a layer of positive active material.

[0080] The positive current collector is a conductive support layer that does not react with other components of the electrochemical device. In some embodiments, the positive current collector comprises a metal, including but not limited to aluminum foil.

[0081] A positive electrode active material layer is disposed on the surface of the positive electrode current collector. The positive electrode active material layer contains a positive electrode active material, and may also contain a binder and a conductive agent. The positive electrode active material can be a material known in the art that can be used as an electrochemical device for lithium ion insertion / extraction.

[0082] In some embodiments, the positive electrode active material may be selected from LiMnO2, LiMn2O4, or LiNi. 1-x Co x O2, LiCo 1- x Mn x O2, LiNi 1-x Mn x O2 (0 < x < 1), Li (Ni) x Co y Mn z )O4(0<x<1, 0<y<1, 0<z<1, 0<x+y+z<1), LiMn 2-a Ni a O4, LiMn 2-a Co a O4 (0 < a < 2), LiMPO4 (M can be selected from at least one of Co, Ni, Fe, Mn, V), spinel-type material LiMn2O4, layered material lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), Li a Ni x A y B (1-x-y) O2 (0.95≤a≤1, A and B can be independently selected from any one of Co, Mn, and Al, and A and B are different, 0<x<1, 0<y<1, 0<x+y<1). In some embodiments, the positive electrode active material may also include at least one of sulfides, selenides, and halides.

[0083] In some embodiments, the positive electrode active material further has a coating layer on its surface, or is mixed with a material having a coating layer. In some embodiments, the coating layer comprises at least one coating element compound selected from oxides, hydroxides, hydroxyoxides, oxycarbonates, and basic carbonates of a coating element. In some embodiments, the compound used for the coating layer may be crystalline or amorphous. In some embodiments, the coating element used for the coating layer includes Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or any mixture thereof. In some embodiments, the coating layer may be formed by any method, as long as including the element in the compound does not negatively affect the properties of the positive electrode active material.

[0084] In some embodiments, the positive electrode active material layer further includes a positive electrode binder and a positive electrode conductive agent. The positive electrode binder is used to improve the adhesion between the positive electrode active material particles and between the positive electrode active material particles and the positive electrode current collector. In some embodiments, the positive electrode binder includes at least one of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, styrene-butadiene rubber of acrylate, epoxy resin, and nylon. The positive electrode conductive agent is used to provide conductivity to the electrode and may include any conductive material as long as it does not chemically react with the active material. In some embodiments, the positive electrode conductive agent is at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, metal powder, metal fiber, and polyphenylene derivatives. In some embodiments, the metal in the metal powder or metal fiber includes at least one of copper, nickel, aluminum, and silver.

[0085] In some embodiments, the method for preparing the positive electrode sheet is a well-known method in the art for preparing positive electrode sheets that can be used in electrochemical devices. For example, the positive electrode active material, conductive agent, and binder can be mixed in a predetermined ratio as needed and stirred; then, a non-aqueous solvent is added, stirred and dispersed to obtain the target slurry; then, it is coated, dried, and rolled to obtain the target positive electrode sheet.

[0086] In some embodiments, the positive electrode sheet can be prepared using the following process (environmental requirements: humidity below 10%, temperature 20-30°C):

[0087] First, a super-P conductive solution with a solid content of 65% is uniformly coated onto the surface of the positive electrode aluminum foil to obtain an aluminum foil with a conductive coating: active material Li(Ni 0.8 Co 0.1 Mn 0.1 O2, conductive agent Super-P, and binder polyvinylidene fluoride were mixed in a mass ratio of 96:2.2:1.8, N-methylpyrrolidone was added, and the mixture was stirred and dispersed to obtain the target slurry. The resulting slurry was then uniformly coated onto aluminum foil.

[0088] The coated aluminum foil is dried at high temperature, then cold-pressed, cut into sheets, and slit. Finally, it is dried under vacuum at 85°C for 12 hours to obtain the positive electrode sheet.

[0089] The obtained electrode sheets are rolled, slit, and cut to obtain the target electrode sheets.

[0090] II. Negative electrode sheet

[0091] A negative electrode is a known type of negative electrode that can be used in electrochemical devices. In some embodiments, a negative electrode includes a negative current collector and a negative active material layer.

[0092] The negative electrode current collector is a conductive support layer that does not react with other components of the electrochemical device. In some embodiments, the negative electrode current collector comprises a metal, including but not limited to copper foil.

[0093] A negative electrode active material layer is disposed on the surface of the negative electrode current collector. The negative electrode active material layer contains a negative electrode active material. The negative electrode active material can be any of the negative electrode active materials known in the art that can be used as electrochemical devices. The active material includes, for example, a substance capable of reversibly inserting and de-intercalating active ions or a substance capable of reversibly doping and de-doping active ions.

[0094] In some embodiments, the negative electrode active material comprises at least one selected from lithium metal, lithium metal alloy, carbon material, and silicon-based material. In some embodiments, the lithium metal alloy comprises an alloy of lithium with a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, In, Zn, Ba, Ra, Ge, Al, and Sn. The carbon material may be any carbon material known in the art that can be used as a carbon-based negative electrode active material in electrochemical devices. In some embodiments, the carbon material comprises at least one selected from crystalline carbon and amorphous carbon. In some embodiments, the crystalline carbon is natural graphite or artificial graphite. In some embodiments, the crystalline carbon is in the shape of an amorphous, plate-like, flake-like, spherical, or fibrous form. In some embodiments, the crystalline carbon is low-crystallinity carbon or high-crystallinity carbon. In some embodiments, low-crystallinity carbon comprises at least one selected from soft carbon and hard carbon. In some embodiments, high-crystallinity carbon comprises at least one selected from natural graphite, crystalline graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesophase carbon microspheres, mesophase pitch, and high-temperature calcined carbon. In some embodiments, the high-temperature calcined carbon is petroleum or coke derived from coal tar pitch. In some embodiments, the amorphous carbon comprises at least one of soft carbon, hard carbon, mesophase pitch carbonization products, and calcined coke. In some embodiments, the negative electrode active material comprises a transition metal oxide. In some embodiments, the negative electrode active material comprises Si or SiO. x (0 < x < 2), Si / C composite, Si-Q alloy, Sn, SnO zThe alloy comprises at least one of Sn-C composites and Sn-R alloys, wherein Q is selected from at least one of alkali metals, alkaline earth metals, elements from Group 13 to Group 16, transition elements, and rare earth elements, and Q is not Si; R is selected from at least one of alkali metals, alkaline earth metals, elements from Group 13 to Group 16, transition elements, and rare earth elements, and R is not Sn. In some embodiments, Q and R comprise at least one of Mg, Ca, Sr, Ba, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, and Po.

[0095] In some embodiments, the negative electrode active material layer further comprises a negative electrode binder and a negative electrode conductive agent. In some embodiments, the negative electrode binder comprises at least one of the following: ethylene difluoroethylene-hexafluoropropylene copolymer (PVDF-Co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, styrene-butadiene rubber of acrylate, epoxy resin, and nylon. In some embodiments, the negative electrode conductive agent is used to provide conductivity to the electrode and may comprise any conductive material as long as it does not react with other components of the electrochemical device. In some embodiments, the negative electrode conductive agent comprises any one or a mixture of carbon-based materials, metal-based materials, and conductive polymers. In some embodiments, the carbon-based material comprises at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, and carbon fiber. In some embodiments, the metal-based material comprises at least one of metal powders or metal fibers selected from copper, nickel, aluminum, silver, etc. In some embodiments, the conductive polymer comprises a polyphenylene derivative.

[0096] In some embodiments, the method for preparing the negative electrode sheet is a method known in the art for preparing negative electrode sheets that can be used in electrochemical devices. In some embodiments, during the preparation of the negative electrode slurry, a solvent is typically added, and the negative electrode active material is added to a binder, and conductive materials and thickeners are added as needed, and then dissolved or dispersed in the solvent to form the negative electrode slurry. The solvent is removed by evaporation during the drying process. The solvent is a solvent known in the art that can be used as a layer of negative electrode active material, including but not limited to water. The thickener is a thickener known in the art that can be used as a layer of negative electrode active material, including but not limited to sodium carboxymethyl cellulose.

[0097] The embodiments of this disclosure do not impose any particular restrictions on the mixing ratio of the negative electrode active material, binder, and thickener in the negative electrode active material layer, and the mixing ratio can be controlled according to the desired performance of the electrochemical device.

[0098] In some embodiments, the negative electrode can be prepared using the following process:

[0099] The negative electrode active material artificial graphite, conductive agent Super-P, thickener sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber were mixed in a mass ratio of 96.2:2:0.8:1, deionized water was added, and the negative electrode slurry was obtained under the action of a vacuum mixer, wherein the solid content of the negative electrode slurry was 54wt%.

[0100] The negative electrode slurry is uniformly coated onto the negative electrode current collector copper foil;

[0101] The coated copper foil is dried at high temperature, then cold-pressed, cut, and slit, and then dried under vacuum at 120°C for 12 hours to obtain the negative electrode sheet.

[0102] III. Separating membrane

[0103] The separator is a separator known in the art that can be used in electrochemical devices, including but not limited to microporous membranes of polyolefins. In some embodiments, the separator comprises at least one of polyethylene (PE), ethylene-propylene copolymer, polypropylene (PP), ethylene-butene copolymer, ethylene-hexene copolymer, and ethylene-methacrylate copolymer.

[0104] In some embodiments, the separator is a single-layer separator or a multi-layer separator.

[0105] In some embodiments, the separator is coated with a coating. In some embodiments, the coating comprises at least one of an organic coating and an inorganic coating, wherein the organic coating is selected from at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polyimide, acrylonitrile-butadiene copolymer, acrylonitrile-styrene-butadiene copolymer, polymethyl methacrylate, polymethyl acrylate, polyethyl acrylate, acrylic-styrene copolymer, polydimethylsiloxane, sodium polyacrylate, and sodium carboxymethyl cellulose, and the inorganic coating is selected from at least one of SiO2, Al2O3, CaO, TiO2, ZnO2, MgO, ZrO2, and SnO2.

[0106] The embodiments disclosed herein do not impose any particular limitations on the morphology and thickness of the separator. The method for preparing the separator is a well-known method in the art for preparing separators that can be used in electrochemical devices.

[0107] In an embodiment according to this disclosure, the separator membrane can be prepared by the following process: a 9 μm thick polyethylene separator membrane is selected, and after coating and drying with PVDF slurry and inorganic particles (the mass ratio of lamellar boehmite and Al2O3 is 70:30), the final separator membrane is obtained with a coating thickness of 3 μm and a membrane porosity of 55%.

[0108] IV. Preparation of Electrochemical Devices

[0109] In some embodiments, the electrochemical device (e.g., a lithium-ion battery) can be prepared using the following process: A positive electrode, a separator, and a negative electrode are stacked sequentially, with the separator acting as a separator between the positive and negative electrodes; then, the positive electrode, separator, and negative electrode are wound together to obtain a bare cell; after welding tabs, the obtained bare cell is placed in an aluminum-plastic film for outer packaging; the electrolyte according to embodiments of this disclosure is injected into the dried bare cell; and after vacuum sealing, settling, formation (e.g., constant current charging at 0.02C to 3.3V, then constant current charging at 0.1C to 3.6V), shaping, and capacity testing, the target cell, i.e., the electrochemical device, is obtained.

[0110] [Electrochemical device electrical performance testing]

[0111] In the following description, a lithium-ion battery will be used as an example to illustrate the electrical performance test results of the electrochemical device. This lithium-ion battery includes a positive electrode, a negative electrode, a separator, and an electrolyte according to embodiments of this disclosure.

[0112] Unless otherwise specified, all reagents, materials, and instruments used in the following examples and comparative examples are commercially available or synthesized. The specific reagents used in the electrolyte are as follows:

[0113] First additive:

[0114]

[0115] Second additive:

[0116]

[0117] Organic solvents: ethylene carbonate (EC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC);

[0118] Electrolyte: Lithium salt.

[0119] Both the first and second additives are commercially available or can be synthesized using methods known and conventional in the art.

[0120] The lithium-ion batteries of Examples 1-12 and Comparative Examples 1-7 described in Tables 1 to 3 below can all be prepared according to the following methods.

[0121] (1) Preparation of the positive electrode: In an environment with humidity below 10% and temperature of 20-30℃, a super-P conductive solution with a solid content of 65% is uniformly coated on the surface of the positive electrode aluminum foil to obtain an aluminum foil with a conductive coating. Specifically, the active material Li(Ni) is coated with the conductive material Li(Ni) 0.8 Co 0.1 Mn 0.1 O2, conductive agent Super-P, and binder polyvinylidene fluoride were mixed in a mass ratio of 96:2.2:1.8. N-methylpyrrolidone was added and the mixture was stirred and dispersed to obtain the target slurry. The slurry was uniformly coated onto aluminum foil. The coated aluminum foil was dried at high temperature, then cold-pressed, cut, and slit. It was then dried under vacuum at 85°C for 12 hours to obtain the positive electrode sheet. The obtained electrode sheet was rolled, slit, and cut to obtain the target electrode sheet.

[0122] (2) Preparation of negative electrode sheet: The negative electrode active material artificial graphite, conductive agent Super-P, thickener sodium carboxymethyl cellulose (CMC) and binder styrene-butadiene rubber are mixed in a mass ratio of 96.2:2:0.8:1, deionized water is added, and a negative electrode slurry is obtained under the action of a vacuum stirrer, wherein the solid content of the negative electrode slurry is 54wt%; the negative electrode slurry is uniformly coated on the negative electrode current collector copper foil; the coated copper foil is dried at high temperature, and after cold pressing, cutting and slitting, it is dried under vacuum at 120℃ for 12h to obtain the negative electrode sheet.

[0123] (3) Electrolyte preparation: In a dry argon glove box, organic solvent (at a mass ratio of EC / DEC / EMC = 3 / 2 / 5), additives, and lithium salt electrolyte are mixed according to the required content. Specifically, organic solvent is added first in a dry argon glove box, followed by additives. After dissolving and stirring thoroughly, lithium salt electrolyte is added and mixed evenly to obtain the electrolyte.

[0124] (4) Preparation of the separator: A polyethylene separator with a thickness of 9 μm was selected. After coating and drying with PVDF slurry and inorganic particles (the mass ratio of plate boehmite and Al2O3 is 70:30), the final separator was obtained with a coating thickness of 3 μm and a separator porosity of 55%.

[0125] (5) Preparation of lithium-ion battery: The positive electrode, separator and negative electrode are stacked in sequence, so that the separator is between the positive electrode and the negative electrode to play a role in isolation; then the positive electrode, separator and negative electrode are wound to obtain a bare cell, and after welding the tabs, the obtained bare cell is placed in the aluminum-plastic film of the outer packaging; the electrolyte according to the embodiment of this disclosure is injected into the dried bare cell, and the target cell is obtained by vacuum sealing, standing, formation (e.g., charging to 3.3V at 0.02C constant current, and then charging to 3.6V at 0.1C constant current), shaping, capacity testing and other processes.

[0126] In Examples 1-12 and Comparative Examples 1-7, the types and contents of the first and second additives used are shown in Tables 1, 2 and 3, where the contents of each additive are weight percentages calculated based on the total mass of the electrolyte.

[0127] The following section describes the performance testing process and results of lithium-ion batteries.

[0128] I. High-Temperature Cycling Test of Lithium-ion Batteries:

[0129] The lithium-ion battery was placed in a 45°C constant temperature oven and charged at a constant current of 2.0C to 4.2V, then charged at a constant voltage to a current of 0.05C, and left to stand for 5 minutes. It was then discharged at a constant current of 1C to 3.0V and left to stand for 10 minutes. This constitutes one cycle. The discharge capacity of the first cycle is recorded as C0, and the discharge capacity after 1000 cycles is recorded as C1000.

[0130] Capacity retention rate (%) of lithium-ion battery after 1000 cycles at 45℃ = C1000 / C0*100%.

[0131] II. High-Temperature Storage Test of Lithium-ion Batteries:

[0132] Before storage, the lithium-ion battery was charged to 3.65V at a constant current of 0.5C. Then, the thickness of the lithium-ion battery was measured using a plate thickness gauge to obtain the thickness L1. The battery was then charged to 4.2V at a constant current of 0.5C and charged to 0.05C at a constant voltage. The lithium-ion battery was then placed in a 60℃ high-temperature oven for 30 days. After the lithium-ion battery cooled down, the thickness L30 of the lithium-ion battery was measured again.

[0133] The growth rate of high-temperature storage cell thickness for lithium-ion batteries = (L30-L1) / L1*100%.

[0134] III. DCR Test of Lithium-ion Batteries:

[0135] The lithium-ion battery was placed in a constant temperature chamber at 25°C for 2 hours. The lithium-ion battery was charged at a constant current of 0.5C to 4.2V, charged at a constant voltage of 0.05C, left to stand for 5 minutes, and discharged at a constant current of 0.1C to 3.0V, which was recorded as capacity C2. The battery was discharged at a constant current of 0.2C2 for 2.5 hours, and the terminal voltage U0 was recorded. The battery was discharged at 1C2 for 1 second, and the terminal voltage U1 was recorded.

[0136] The formula for calculating the DC internal resistance (DCR) of a lithium-ion battery is as follows: DCR=(U0-U1) / (0.9C2).

[0137] IV. Cell heating experiment:

[0138] Place each group of 5 lithium-ion batteries in a 25°C constant temperature chamber and let them stand for 30 minutes to allow them to reach a constant temperature. Then, discharge them at a constant current of 0.5C to 3V, let them stand for 5 minutes, charge them at a constant current of 0.5C to 4.2V, charge them at a constant voltage of 0.05C, let them stand for 5 minutes, and then raise the temperature to 130°C at a rate of 5°C / min and hold them at that temperature for 60 minutes. Observe and record the state of the samples and take photos. If the samples do not ignite or explode, they are considered to have passed the heating test.

[0139] Table 1 below shows the capacity retention rates of various lithium-ion batteries after 1000 cycles. In various lithium-ion batteries, the content of the first and second additives refers to the mass percentage relative to the total mass of the electrolyte. In Comparative Example 1, the content of both the first and second additives was 0, meaning no first or second additives were added to the electrolyte, and the capacity retention rate was 81%. In Comparative Example 2, the first additive represented by Formula I-4 was used at a content of 0.01%, while the content of the second additive was 0, resulting in a capacity retention rate of 82%. In Comparative Example 5, the second additive represented by Formula II-7 was used at a content of 0.01%, while the content of the first additive was 0, resulting in a capacity retention rate of 81%. In Example 1, the first additive represented by Formula I-4 was used at a content of 0.1%, and the second additive represented by Formula II-7 was used at a content of 0.5%, resulting in a capacity retention rate of 83%. The types and contents of the first and second additives in other examples and comparative examples, as well as the corresponding capacity retention rates, are shown in Table 1 in the same manner and will not be repeated here.

[0140] Table 1 Capacity retention of lithium-ion batteries

[0141]

[0142] Table 1 shows the high-temperature cycling capacity retention data for Comparative Examples 1 to 7. Within the implementation scope, both the first and second additives can form an interface film on the electrode material surface, suppressing phase transitions in the cathode material and lithium source loss caused by polarization, thus improving the high-temperature cycling retention rate. Compared to the second additive, the interface film formed by the first additive is more uniform and dense, resulting in a more significant improvement in cycling performance. A comparison of the retention rate data from Examples 1-12 with those from Comparative Examples 1-7 shows that when the first and second additives coexist, the resulting interface film has a synergistic effect. Their redox potentials are coupled, and the resulting interface film is rich in multi-scale inorganic components, exhibiting superior cycling improvement. Example 3, in particular, achieves the highest capacity retention rate compared to other examples and comparative examples.

[0143] Table 2 below shows the DCR test results and thickness retention rate after 30 days of storage at 60°C for various lithium-ion batteries. In various lithium-ion batteries, the content of the first and second additives refers to the mass percentage relative to the total mass of the electrolyte. In Comparative Example 1, the content of both the first and second additives was 0, meaning no first or second additives were added to the electrolyte; the DCR was 44 mohm, and the thickness growth rate was 25%. In Comparative Example 2, the first additive represented by Formula I-4 was used at a content of 0.01%, while the content of the second additive was 0; the DCR was 44 mohm, and the thickness growth rate was 22%. In Comparative Example 5, the second additive represented by Formula II-7 was used at a content of 0.01%, while the content of the first additive was 0; the DCR was 44 mohm, and the thickness growth rate was 24%. In Example 1, the first additive represented by Formula I-4 was used at a content of 0.1%, and the second additive represented by Formula II-7 was used at a content of 0.5%; the DCR was 42 mohm, and the thickness growth rate was 19%. The types and contents of the first and second additives in other embodiments and comparative examples, as well as the corresponding DCR and thickness growth rates, are shown in Table 2 in the same manner, and will not be repeated here.

[0144] Table 2. DCR test results and thickness retention of lithium-ion batteries

[0145]

[0146] Table 2 shows the DCR and thickness retention rates of Comparative Examples 1 to 7, indicating that within the scope of implementation, both the first and second additives can improve high-temperature storage performance while reducing impedance. The interfacial film formed by the first and second additives exhibits excellent ionic conductivity, and the high-temperature electrochemical stability and mechanical modulus of this interfacial film are also excellent. A comparison of the DCR and thickness retention rate data of Examples 1-12 with those of Comparative Examples 1-7 shows that, within the scope of implementation, the composition of the first and second additives directly determines the composition and thickness of the interfacial film. After optimizing their content, the thickness and size of the optimized interfacial film can simultaneously suppress high-temperature side reaction gas generation and more rapidly promote lithium-ion conduction, reducing interfacial impedance. In particular, Example 3 achieves the lowest DCR and thickness growth rate compared to other examples and comparative examples.

[0147] Table 3 below shows the heating test results for various lithium-ion batteries. In various lithium-ion batteries, the content of the first and second additives refers to the mass percentage relative to the total mass of the electrolyte. In Comparative Example 1, the content of both the first and second additives was 0, meaning no first or second additives were added to the electrolyte. The heating test pass rate was 0 / 5, meaning all five lithium-ion batteries in this group failed the heating test. In Comparative Example 2, the first additive represented by Formula I-4 was used at a content of 0.01%, while the content of the second additive was 0. The heating test pass rate was 0 / 5, meaning all five lithium-ion batteries in this group failed the heating test. In Comparative Example 6, the second additive represented by Formula II-7 was used at a content of 4%, while the content of the first additive was 0. The heating test pass rate was 2 / 5, meaning two of the five lithium-ion batteries in this group passed the heating test, and three failed. In Example 2, the first additive represented by Formula I-4 was used at a content of 0.5%, and the second additive represented by Formula II-7 was used at a content of 1%. The heating test pass rate was 3 / 5, meaning three of the five lithium-ion batteries in this group passed the heating test, and two failed. The types and contents of the first and second additives in other embodiments and comparative examples, as well as the corresponding heating test pass rates, are shown in Table 3 in the same manner, and will not be repeated here.

[0148] Table 3. Heating Experiment Results of Lithium-ion Batteries

[0149]

[0150]

[0151] The heating test results of Comparative Examples 1, 3, 4, 6, and 7 in Table 3 show that adding a certain amount of the first and second additives to the electrolyte can improve the heating test pass rate of lithium-ion batteries. The heating test pass rate data of Examples 1-12 show that the optimized combination of the first and second additives has a very significant effect on improving the heating test pass rate. This is mainly because the interface film formed by the optimized first and second additives is more uniform, suppressing the overall heat generation rate; and the components of this interface film have better high-temperature stability. Both factors combined improve the heating test pass rate of lithium-ion batteries. In particular, Examples 3 and 8 achieved the highest heating test pass rate of 5 / 5 compared to other examples and comparative examples, meaning that all five lithium-ion batteries in the corresponding groups passed the heating test.

[0152] [Electronic Devices]

[0153] Embodiments of this disclosure also provide an electronic device, which can be any electronic device, including but not limited to automobiles, motorcycles, skateboards, airplanes, buses, motors, backup power supplies, large household batteries, lithium-ion capacitors, computers, mobile phones, e-readers, fax machines, copiers, flashlights, televisions, VR, AR, etc. It should be noted that the electrochemical device of the embodiments of this disclosure is applicable not only to the electronic devices exemplified above, but also to electronic devices such as energy storage power stations, maritime transport vehicles, and air transport vehicles. Air transport vehicles include air transport devices within the atmosphere and air transport devices outside the atmosphere.

[0154] The electronic devices in embodiments of this disclosure may include the electrochemical devices described above.

[0155] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, and are not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. An electrolyte comprising a compound represented by Formula I and a compound represented by Formula II, Formula I, Formula II, in, The compound represented by Formula I includes at least one of the compounds represented by Formulas I-1 to I-8: Formula I-1, Formula I-2, Formula I-3, Equation I-4, Equation I-5, Formula I-6, Equation I-7, Formula I-8; The compound represented by Formula II includes at least one of the compounds represented by Formula II-1 to Formula II-8: Formula II-1, Formula II-2, Formula II-3, Formula II-4, Formula II-5, Formula II-6, Formula II-7, Formula II-8.

2. The electrolyte according to claim 1, wherein, Based on the total mass of the electrolyte, the total mass percentage of the compound represented by Formula I and the compound represented by Formula II is 0.01%-20%.

3. The electrolyte according to claim 2, wherein, Based on the total mass of the electrolyte, the mass percentage of the compound represented by Formula I is 0.1%-2%.

4. The electrolyte according to claim 2, wherein, The mass percentage of the compound represented by Formula II is 0.1%-5% based on the total mass of the electrolyte.

5. An electrochemical device comprising a positive electrode, a negative electrode, a separator, and an electrolyte according to any one of claims 1 to 4.

6. An electronic device comprising the electrochemical device according to claim 5.

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