Non-aqueous electrolyte, lithium ion battery, battery module, battery pack and electric device

Abstract

The invention relates to the technical field of batteries, in particular to a non-aqueous electrolyte, a lithium ion battery, a battery module, a battery pack and an electric device. The non-aqueous electrolyte comprises a non-aqueous organic solvent, a lithium salt and a functional additive, and the functional additive comprises a compound with a structure as shown in a formula I. When the electrolyte additive is used in the lithium ion battery, the internal resistance of the battery can be effectively reduced, the decomposition and gas production of the electrolyte can be inhibited, the high-temperature storage and high-temperature cycle performance of the battery can be effectively improved, and the multiplying power and the low-temperature performance can be considered at the same time.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a non-aqueous electrolyte, a lithium-ion battery, a battery module, a battery pack and an electrical device. Background Art

[0002] Since its commercialization, lithium-ion batteries have been widely used in the field of power batteries due to their high energy density, high power density, long cycle life and green environmental protection. At the same time, due to the variability of the application environment of terminal equipment, consumers have put forward higher and higher requirements for the performance of lithium-ion batteries, such as long cycle life and normal use under high and low temperature conditions. However, performance degradation (such as capacity loss, reduced cycle life) and safety hazards (such as short circuit caused by diaphragm melting) in high temperature environments are the core issues restricting its development. Specifically, high temperature accelerates battery aging. At the same time, due to the poor thermal stability of lithium salts and organic solvents at high temperatures, battery performance will also decline. In this case, the electrolyte is easy to decompose and produce a large amount of gas, causing the battery to swell, which in turn affects its performance and safety. Therefore, it is imperative to develop an electrolyte that can remain stable in a high temperature environment to meet this challenge.

[0003] Organic phosphate flame-retardant electrolytes are the earliest used and most studied flame-retardant electrolytes in lithium-ion batteries. They mainly prevent combustion through free radical elimination reactions, including alkyl phosphates (such as TMP, TEP, etc.), aryl phosphates, phosphites, phosphazenes, phosphorus-fluorine, etc. Among them, fluorine-substituted phosphate compounds may have unique physical and chemical properties because they have both phosphorus atoms and fluorine atoms connected to them and a ring structure. However, due to the large number of functional groups, the large adjustment space for substitution groups and structural changes, and the interaction between various substances in the specific formulation of the electrolyte, the specific direction of the improvement of electrolyte performance by fluorine-substituted phosphate compounds is still unclear. In addition, due to the novel structure of fluorine-substituted compounds and the limitations of the preparation process, their application in electrolytes is not widespread.

[0004] For example, the patent with application publication number CN116063352A discloses trifluorocyclic phosphate compounds, and focuses on the preparation method of such compounds. Although it is mentioned that such compounds can be used as lithium battery electrolyte additives, no actual application conditions are given, and no data are given to illustrate the specific role in improving the performance of the electrolyte. CN116284140A discloses difluorocyclic phosphate compounds, and also focuses on its preparation method. Although it is mentioned that such fluorinated cyclic phosphate compounds can be used as a new type of lithium ion battery electrolyte additive, it helps to improve the cycle life of lithium ion batteries and improve the high temperature cycle performance of lithium ion batteries, such as having higher safety, higher energy density, and higher rate performance, but no experimental data are given to prove the real effect of the above compounds in practical applications. Due to the influence of other functional groups and other substances in the electrolyte formula on fluorine atoms, phosphorus atoms and cyclic structures, there is a defect of limited improvement in various properties of the electrolyte in practical applications. Summary of the invention

[0005] In view of the shortcomings of the prior art mentioned above, the object of the present invention is to provide a non-aqueous electrolyte, a lithium-ion battery, a battery module, a battery pack and an electrical device. When the electrolyte additive of the present invention is used in a lithium-ion battery, it can effectively reduce the internal resistance of the battery, inhibit the decomposition and gas production of the electrolyte, and effectively improve the high-temperature storage and high-temperature cycle performance of the battery, while taking into account both the rate and low-temperature performance.

[0006] To achieve the above-mentioned object and other related objects, the first aspect of the present invention provides a non-aqueous electrolyte, comprising a lithium salt, a non-aqueous organic solvent and a functional additive, wherein the functional additive comprises a compound having a structure shown in Formula I, ; Wherein, R1, R2, R3, and R4 are each independently selected from any one of hydrogen, carbonyl, substituted or unsubstituted C1-C10 straight or branched alkyl, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C2-C10 alkynyl, and substituted or unsubstituted C1-C10 alkoxy; or R3 and R4 are bonded to form a bridged ring; A is selected from O or S.

[0007] A second aspect of the present invention provides a lithium ion battery comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and the non-aqueous electrolyte of the first aspect of the present invention.

[0008] A third aspect of the present invention provides a battery module, comprising the lithium-ion battery described in the second aspect of the present invention.

[0009] A fourth aspect of the present invention provides a battery pack, comprising the battery module described in the third aspect of the present invention.

[0010] The fifth aspect of the present invention provides an electrical device, comprising the lithium-ion battery described in the second aspect of the present invention, wherein the lithium-ion battery is used as a power source for the electrical device, and the electrical device includes a mobile device, an electric vehicle, an electric train, a satellite, a ship, and an energy storage system.

[0011] Compared with the prior art, the beneficial effects of the present invention are: (1) The present invention uses a cyclic fluorinated oxythiophosphorus compound having a structure shown in Formula I as an electrolyte additive, which has good film-forming properties and can form a dense and stable passivation film on the positive and negative electrodes, and can introduce P and S elements into the passivation film, thereby improving ionic conductivity, reducing interfacial impedance, and effectively improving the cycle performance of lithium-ion batteries; and the cyclic fluorinated oxythiophosphorus compound has a low oxidation potential and can preferentially polymerize on the surface of the positive electrode to form a stable electrolyte interface (CEI film), which can significantly reduce the interfacial impedance of the positive electrode and is beneficial to the migration of lithium ions. The formed CEI film can effectively inhibit the side reaction between the electrolyte and the positive electrode, inhibit the dissolution of transition metal ions, and improve the interfacial stability of the positive electrode; (2) In addition to forming a film preferentially at the positive electrode, the cyclic fluorinated oxythiophosphorus compounds also have a high reduction potential and can preferentially form a thin and stable electrolyte interface (SEI film) at the negative electrode. The SEI film is mainly composed of inorganic components and can provide high interfacial chemical stability and interfacial stability; the cyclic ether structure can decompose at the negative electrode to form a polymer structure similar to PEO, which is conducive to the rapid transmission of lithium ions, thereby reducing impedance. The formed SEI film can effectively isolate the electrolyte from the negative electrode material, inhibit the decomposition of the electrolyte and produce gas, and further improve the high temperature performance; (3) The cyclic fluorinated oxythion phosphorus compounds used in the present invention are used in combination with other additives to regulate the reduction potential of other additives, inhibit the film-forming reaction of other additives, protect other additives, and allow other additives to continue to function in the electrolyte, thereby improving long-cycle performance. The synergistic effect of these additives can reduce the impedance of lithium-ion batteries, increase ion conductivity, improve initial efficiency, and improve high-temperature storage performance and high-temperature cycle performance. DETAILED DESCRIPTION

[0012] Hereinafter, embodiments of the non-aqueous electrolyte, lithium-ion battery, battery module, battery pack, and electrical device provided by the present invention will be described in detail.

[0013] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that a range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In the present application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, wherein a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0014] The present invention provides a non-aqueous electrolyte and a lithium-ion battery, a battery module, a battery pack and an electrical device. In the non-aqueous electrolyte of the present application, the additive components cooperate with each other, can effectively reduce the internal resistance of the battery, inhibit the decomposition and gas production of the electrolyte, effectively improve the high-temperature storage and high-temperature cycle performance of the battery, and can take into account both the rate and low-temperature performance. On this basis, the present application is completed.

[0015]

Non-aqueous electrolyte

[0016] The compound of the structure shown in Formula I is: ; Wherein, R1, R2, R3, and R4 are each independently selected from any one of hydrogen, carbonyl, substituted or unsubstituted C1-C10 straight or branched alkyl, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C2-C10 alkynyl, and substituted or unsubstituted C1-C10 alkoxy; or R3 and R4 are bonded to form a bridged ring; A is selected from O or S.

[0017] The compound of the structure shown in Formula I of the present invention has good film-forming properties, can form a dense and stable passivation film on the positive and negative electrodes, and can introduce P and S elements into the passivation film, thereby improving the ionic conductivity, reducing the interface impedance, and effectively improving the cycle performance of the lithium-ion battery; and the cyclic fluorinated oxythiophosphorus compound of the structure shown in Formula I has a lower oxidation potential, can preferentially polymerize on the surface of the positive electrode to form a stable electrolyte interface (CEI film), can significantly reduce the interface impedance of the positive electrode, is beneficial to the migration of lithium ions, and the formed CEI film can effectively inhibit the side reaction between the electrolyte and the positive electrode, inhibit the dissolution of transition metal ions, and improve the stability of the positive electrode interface.

[0018] In the compound of the structure represented by formula I of the present invention, R1, R2, R3 and R4 are independently selected from hydrogen.

[0019] In the compound of the structure represented by formula I of the present invention, R1, R2, R3 and R4 are each independently selected from a carbonyl group.

[0020] In the compound of the structure shown in Formula I of the present invention, R1, R2, R3, and R4 are each independently selected from substituted or unsubstituted C1-C10 straight or branched alkyl groups. In a specific embodiment, R1, R2, R3, and R4 are each independently selected from substituted or unsubstituted C1-C8, C1-C6, C1-C4, or C1-C2 straight or branched alkyl groups. Optionally, R1, R2, R3, and R4 are each independently selected from methyl, ethyl, propyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, or sec-butyl. Optionally, the alkyl group may be substituted, and the substituent may be, for example, fluorine, chlorine, bromine, iodine, methoxy, siloxane, trifluoromethyl, trifluoromethoxy, cyano, and the like.

[0021] In the compound of the structure shown in Formula I of the present invention, R1, R2, R3, and R4 are each independently selected from substituted or unsubstituted C2-C10 alkenyl groups. In a specific embodiment, R1, R2, R3, and R4 are each independently selected from substituted or unsubstituted C2-C8, C2-C6, or C2-C4 alkenyl groups. Optionally, R1, R2, R3, and R4 are each independently selected from vinyl, propenyl, isopropenyl, butenyl, isobutenyl, tert-butenyl, or sec-butenyl. Optionally, the alkenyl group may be substituted, and the substituent may be, for example, fluorine, chlorine, bromine, iodine, methoxy, siloxane, trifluoromethyl, trifluoromethoxy, cyano, and the like.

[0022] In the compound of the structure shown in Formula I of the present invention, R1, R2, R3, and R4 are each independently selected from substituted or unsubstituted C2-C10 alkynyl groups. In a specific embodiment, R1, R2, R3, and R4 are each independently selected from substituted or unsubstituted C2-C8, C2-C6, or C2-C4 alkynyl groups. Optionally, R1, R2, R3, and R4 are each independently selected from ethynyl, propynyl, isopropynyl, butynyl isobutynyl, tert-butynyl, or sec-butynyl. Optionally, the alkynyl group may be substituted, and the substituent may be, for example, fluorine, chlorine, bromine, iodine, methoxy, siloxane, trifluoromethyl, trifluoromethoxy, cyano, and the like.

[0023] In the compound of the structure shown in Formula I of the present invention, R1, R2, R3, and R4 are each independently selected from substituted or unsubstituted C1-C10 alkoxy groups. In a specific embodiment, R1, R2, R3, and R4 are each independently selected from substituted or unsubstituted C1-C8, C1-C6, C1-C4, or C1-C2 alkoxy groups. Optionally, the alkoxy group may be substituted, and the substituent may be, for example, fluorine, chlorine, bromine, iodine, siloxane, trifluoromethyl, trifluoromethoxy, cyano, etc.

[0024] In the compound of the structure represented by formula I of the present invention, R3 and R4 are bonded to form a bridge ring.

[0025] In the compound of the structure represented by formula I of the present invention, A is selected from O or S.

[0026] The cyclic ether structure can decompose at the negative electrode to form a polymer structure similar to PEO, which is conducive to the rapid transmission of lithium ions, thereby reducing impedance. The formed SEI film can effectively isolate the electrolyte from the negative electrode material, inhibit the decomposition of the electrolyte and produce gas, and further improve the high temperature performance.

[0027] In some optional embodiments of the present invention, R1, R2, R3, and R4 are each independently selected from any one of hydrogen, carbonyl, substituted or unsubstituted C1-C4 straight or branched alkyl, substituted or unsubstituted C2-C4 alkenyl, substituted or unsubstituted C2-C4 alkynyl, and substituted or unsubstituted C1-C4 alkoxy; or R3 and R4 are bonded to form a bridged ring.

[0028] In some optional embodiments of the present invention, R1, R2, R3, and R4 are each independently selected from any one of hydrogen, carbonyl, substituted or unsubstituted C1-C2 straight or branched alkyl, substituted or unsubstituted C2-C3 alkenyl, substituted or unsubstituted C2-C3 alkynyl, and substituted or unsubstituted C1-C2 alkoxy; or R3 and R4 are bonded to form a bridged ring.

[0029] In some optional embodiments of the present invention, R1, R2, R3, and R4 are each independently selected from any one of hydrogen, carbonyl, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, sec-butyl, methoxy-substituted methyl, vinyl, propenyl, ethynyl, propynyl, methoxy, and ethoxy; or R3 and R4 are bonded to form a bridged ring.

[0030] In some optional embodiments of the present invention, R1, R2, R3, and R4 are each independently selected from hydrogen, carbonyl, methyl, ethyl, vinyl, ethynyl, methoxy, and methoxy-substituted methyl, or R3 and R4 are bonded to form a bridged ring.

[0031] In the non-aqueous electrolyte provided by the present invention, further, the compound of the structure represented by formula I is selected from the following structures: ; ; .

[0032] In the non-aqueous electrolyte provided by the present invention, the functional additive in the non-aqueous electrolyte may include the compound represented by Formula I, or may include any one or more combinations of the compounds represented by Compounds 1 to 17 above.

[0033] In the non-aqueous electrolyte provided by the present invention, the mass proportion of the compound of the structure shown in Formula I in the non-aqueous electrolyte is 0.5% to 2%. In some embodiments, the mass proportion of the compound of the structure shown in Formula I in the non-aqueous electrolyte may also be 0.5% to 1%, 0.5% to 1.5%, 0.5% to 2%, 1% to 1.5%, 1% to 2% or 1.5% to 2%. Within the above range, the compound of the structure shown in Formula I can preferentially form a stable and dense passivation film on the surface of the positive and negative electrodes, reduce the interface impedance, inhibit the decomposition and gas production of the electrolyte, and improve the high temperature performance of the battery core; if the proportion of the compound of the structure shown in Formula I is too high (the mass proportion in the non-aqueous electrolyte is higher than 2%), the film will be too thick, the interface impedance will be increased, and the performance of the battery core will be deteriorated. If the proportion of the compound of the structure shown in Formula I is too low (the mass proportion in the non-aqueous electrolyte is lower than 0.5%), the film formation effect will be poor, and there will be no obvious improvement on the high temperature performance.

[0034] In the non-aqueous electrolyte provided by the present invention, the functional additives also include other additives, and the other additives are selected from lithium bis(fluorosulfonyl)imide, tetravinylsilane, lithium trifluoromethanesulfonate, lithium fluorosulfonate, methanesulfonic acid-2-propynyl alcohol, methanedisulfonic acid methylene ester, N-methyldi(fluorosulfonyl)imide, 4,5-dicyano-2-methylimidazole and 4,5-dicyano-2-ethylimidazole. Optionally, the other additives are selected from lithium bis(fluorosulfonyl)imide, lithium fluorosulfonate, methanesulfonic acid-2-propynyl alcohol, methanedisulfonic acid methylene ester, 4,5-dicyano-2-methylimidazole and 4,5-dicyano-2-ethylimidazole. Preferably, the other additives are selected from lithium bis(fluorosulfonyl)imide (LiFSI), methanesulfonic acid-2-propynyl alcohol (PMS), lithium fluorosulfonate (LiOf), and methanedisulfonic acid methylene ester (MMDS). For example, it can be a combination of lithium bis(fluorosulfonyl)imide (LiFSI), 2-propynyl methanesulfonate (PMS), a combination of 2-propynyl methanesulfonate (PMS) and lithium fluorosulfonate, or a combination of lithium fluorosulfonate (LiOf) and methylene disulfonate (MMDS). When the compound of the structure shown in Formula I is used in conjunction with other additives in the electrolyte, the performance of the lithium-ion battery can be further improved. Specifically: The other additives of the present invention can have a significant synergistic effect when used in conjunction with the compound of the structure shown in Formula I, can regulate the reduction potential of other additives, inhibit the film-forming reaction of other additives, play a role in protecting other additives, and allow other additives to continue to act in the electrolyte to improve long-cycle performance; these additives can work synergistically to reduce the impedance of lithium-ion batteries, improve ionic conductivity, improve the first effect, and improve high-temperature storage performance and high-temperature cycle performance.

[0035] In the non-aqueous electrolyte provided by the present invention, the other additives account for 1% to 5% of the mass of the non-aqueous electrolyte. In some embodiments, the other additives may also account for 1% to 4%, 1% to 3%, 2% to 4%, 1% to 2%, 2% to 3%, 3% to 4% or 4% to 5% by mass of the non-aqueous electrolyte, etc. Within the above range, other additives can modify the positive and negative electrode interface films, inhibit gas production, reduce impedance, etc. If the proportion of the other additives is too high (the mass proportion in the non-aqueous electrolyte is higher than 5%), it may cause the film to be too thick, increase impedance, etc. If the proportion of the other additives is too low (the mass proportion in the non-aqueous electrolyte is lower than 1%), the film-forming effect is poor, the interface impedance cannot be effectively reduced, and the improvement of the battery performance is not obvious.

[0036] Further optionally, when the other additive is selected from lithium bis(fluorosulfonyl)imide (LiFSI), 2-propynyl methanesulfonate (PMS), lithium fluorosulfonate (LiOf) or methylene disulfonate (MMDS), the mass proportion of the lithium bis(fluorosulfonyl)imide in the non-aqueous electrolyte is 0.5% to 3%, which can be selected from 0.5% to 1%, 0.5% to 1.5%, 0.5% to 2%, 0.5% to 2.5%, 1% to 1.5%, 1% to 2%, 1% to 2.5%, 1% to 3%, 1.5% to 2.5%, 1.5% to 2%, 2% to 2.5% or 2.5% to 3%, etc. The mass proportion of 2-propynyl methanesulfonate in the non-aqueous electrolyte is 0.5% to 2%, which can be selected from 0.5% to 1%, 0.5% to 1.5%, 1% to 1.5%, 1% to 2% or 1.5% to 2%, etc. The mass proportion of the lithium fluorosulfonate in the non-aqueous electrolyte is 0.5% to 3%, which can be 0.5% to 1%, 0.5% to 1.5%, 0.5% to 2%, 0.5% to 2.5%, 1% to 1.5%, 1% to 2%, 1% to 2.5%, 1% to 3%, 1.5% to 2.5%, 1.5% to 2%, 2% to 2.5% or 2.5% to 3%, etc. The mass proportion of the methylene disulfonate in the non-aqueous electrolyte is 0.5% to 2%, which can be 0.5% to 1%, 0.5% to 1.5%, 1% to 1.5%, 1% to 2% or 1.5% to 2%, etc.

[0037] In the non-aqueous electrolyte provided by the present invention, the lithium salt is selected from one or more combinations of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium hexafluorosilicate, lithium aluminum tetrachloride, lithium bis(oxalatoborate), lithium chloride, lithium bromide, lithium iodide, lithium trifluoromethanesulfonate, and lithium bis(trifluoromethanesulfonic acid)imide. Preferably, the lithium salt is selected from lithium hexafluorophosphate (LiPF6).

[0038] In the non-aqueous electrolyte provided by the present invention, the concentration of the lithium salt in the non-aqueous electrolyte is 0.5 mol / L to 2 mol / L. In some embodiments, the concentration of the lithium salt in the non-aqueous electrolyte may also be 0.5 mol / L to 1 mol / L, 1 mol / L to 1.5 mol / L or 1.5 mol / L to 2 mol / L, etc. Within the above range, high lithium ion conductivity and stable lithium ion transmission can be guaranteed. If the proportion of the lithium salt is too high (the content in the non-aqueous electrolyte is higher than 2 mol / L), the lithium salt will be incompletely dissociated, and the viscosity of the electrolyte will be too high, which will hinder the transmission of lithium ions and reduce the rate performance and low temperature performance. If the proportion of the lithium salt is too low (the content in the non-aqueous electrolyte is lower than 0.5 mol / L), the electrolyte will have poor electrochemical stability.

[0039] In the non-aqueous electrolyte provided by the present invention, the non-aqueous organic solvent is selected from cyclic carbonates and / or chain carbonates. Optionally, the non-aqueous organic solvent is selected from one or more of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, and γ-butyrolactone. Further optionally, the non-aqueous organic solvent is selected from ethyl methyl carbonate (EMC), diethyl carbonate (DEC) and ethylene carbonate (EC), and the volume ratio of ethyl methyl carbonate (EMC), diethyl carbonate (DEC) and ethylene carbonate (EC) is (4-6): (1-3): (2-4), for example, it can be 5: (1-3): (2-4), (4-6): 2: (2-4) or (4-6): (1-3): 3.

[0040] In the non-aqueous electrolyte provided by the present invention, the mass proportion of the non-aqueous organic solvent in the non-aqueous electrolyte is 73% to 93%. In some embodiments, the mass proportion of the non-aqueous organic solvent in the non-aqueous electrolyte may also be 73% to 75%, 75% to 85%, or 85% to 93%, etc. Within the above range, lithium salts and additives can be dissolved well. If the proportion of the non-aqueous organic solvent is too high (the mass proportion in the non-aqueous electrolyte is higher than 93%), the electrochemical stability of the electrolyte will be poor. If the proportion of the non-aqueous organic solvent is too low (the mass proportion in the non-aqueous electrolyte is lower than 73%), the lithium salt will be incompletely dissociated and the viscosity of the electrolyte will be too high.

[0041]

Lithium-ion battery

[0042] The positive electrode includes a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector. The positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The positive electrode active material layer includes a positive electrode active material, and the positive electrode active material layer may also include a conductive agent and a binder. The positive electrode active material may be selected from a combination of one or more of lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate and lithium iron manganese phosphate. Preferably, the positive electrode active material used in this experiment is selected from lithium nickel cobalt manganese oxide, wherein 0.5≤the molar fraction of nickel is <1. Specifically, the nickel cobalt manganese oxide ternary material may be selected from LiNi 0.5 Co 0.2 Mn 0.3 O2、LiNi 0.65 Co 0.15 Mn 0.2O2 and LiNi 0.8 Co 0.1 Mn 0.1 O2, etc. One or more. Those skilled in the art can select conductive agents and binders suitable for lithium ion batteries in the art. Among them, the conductive agent can include, for example, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers. The binder can include, for example, at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.

[0043] In some embodiments, the positive electrode can be prepared in the following manner: the components for preparing the positive electrode, such as the positive electrode material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode can be obtained.

[0044] The negative electrode 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 negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material. The negative electrode active material layer includes a negative electrode active material, and the negative electrode active material layer may also include a plasticizer, a conductive agent and a binder. The negative electrode active material may be selected from a combination of one or more of silicon carbon, silicon oxygen, natural graphite, artificial graphite, lithium titanate, amorphous carbon and lithium metal. Those skilled in the art may select plasticizers, conductive agents and binders suitable for lithium ion batteries in the art. Among them, the conductive agent may be selected, for example, from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), carboxymethyl chitosan (CMCS), and sodium carboxymethyl cellulose (CMC-Na).

[0045] In some embodiments, the negative electrode can be prepared in the following manner: the above-mentioned components for preparing the negative electrode, such as the negative electrode material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode can be obtained.

[0046] The lithium-ion battery provided in the second aspect of the present invention can be prepared by a method known in the art. For example, the positive electrode, the separator, and the negative electrode are stacked in order, so that the separator is between the positive and negative electrodes to play an isolating role, and then the sheets are stacked to obtain a bare cell; the bare cell is placed in an outer packaging shell, dried, and then injected with a non-aqueous electrolyte, and a lithium-ion battery is obtained through vacuum packaging, standing, forming, shaping, and other processes.

[0047]

Battery module

[0048]

Battery Pack

[0049] The number of battery modules in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0050]

Electrical devices

[0051] The beneficial effects of the present invention are further illustrated below in conjunction with embodiments.

[0052] In order to make the invention purpose, technical scheme and beneficial technical effect of the present invention clearer, the present invention is further described in detail below in conjunction with examples. However, it should be understood that the examples of the present invention are only for explaining the present invention, not for limiting the present invention, and the examples of the present invention are not limited to the examples given in the specification. The specific experimental conditions or operating conditions not specified in the examples are made under conventional conditions, or are made under the conditions recommended by the material supplier.

[0053] In addition, it should be understood that one or more method steps mentioned in the present invention do not exclude the existence of other method steps before or after the combination step or the insertion of other method steps between these explicitly mentioned steps, unless otherwise specified; it should also be understood that the combination connection relationship between one or more devices / electrical devices mentioned in the present invention does not exclude the existence of other devices / devices before or after the combination device / device or the insertion of other devices / devices between these two explicitly mentioned devices / devices, unless otherwise specified. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or the scope of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of the present invention without substantially changing the technical content.

[0054] In the following examples, the reagents, materials and instruments used are all commercially available unless otherwise specified.

[0055] The positive electrode material of the lithium-ion battery used in the embodiments and comparative examples of the present invention is LiNi 0.5 Co 0.2 Mn 0.3 O2 (lithium nickel cobalt manganese oxide, where 0.5≤ molar fraction of nickel <1), artificial graphite is selected as the negative electrode, the electrolyte injection amount of each battery is 4g, and the following different electrolytes are selected as examples, and comparative example 1 is a conventional electrolyte.

[0056] Example 1 Preparation of electrolyte: Prepare electrolyte in a dry room (the dew point of the preparation environment is lower than -40°C), mix ethyl methyl carbonate (EMC), diethyl carbonate (DEC) and ethylene carbonate (EC) in a volume ratio of 5:2:3 as an organic solvent, and prepare a total of 100 mL. Add lithium salt LiPF6 to the solvent to make its molar concentration 1.1M / L, add 1% of the total mass of the above electrolyte, 1% of lithium bis(fluorosulfonyl)imide (1% LiFSI) and 0.5% of 2-propynyl methanesulfonate (0.5% PMS), respectively, stir until completely dissolved, and obtain the lithium ion battery electrolyte of Example 1. Inject the prepared electrolyte into a soft pack battery, and after standing, forming and volume separation, obtain lithium ion battery A.

[0057] Example 2 Preparation of electrolyte: The difference from Example 1 is that 1% of Compound 1 is replaced by 0.5% of Compound 1 to obtain the lithium ion battery electrolyte of Example 2, and the prepared electrolyte is injected into the soft-pack battery. After standing, forming and capacity separation, lithium ion battery B is obtained.

[0058] Example 3 Preparation of electrolyte:

[0059] Different from Example 1, 1% of Compound 1 is replaced by 2% of Compound 1 to obtain the lithium ion battery electrolyte of Example 3, and the prepared electrolyte is injected into the soft-pack battery. After standing, formation and capacity separation, lithium ion battery C is obtained.

[0060] Example 4 Preparation of electrolyte: Different from Example 1, 1% lithium bis(fluorosulfonyl)imide (1% LiFSI) and 0.5% 2-propynyl methanesulfonate (0.5% PMS) were replaced with 2% lithium bis(fluorosulfonyl)imide (2% LiFSI) and 1% 2-propynyl methanesulfonate (1% PMS) to obtain the lithium ion battery electrolyte of Example 4, and the prepared electrolyte was injected into the soft pack battery, and after standing, formation and capacity separation processes, a lithium ion battery D was obtained.

[0061] Example 5 Preparation of electrolyte: Different from Example 1, 1% lithium bis(fluorosulfonyl)imide (1% LiFSI) and 0.5% 2-propynyl methanesulfonate (0.5% PMS) were replaced with 1% lithium fluorosulfonate (1% LiOf) and 0.5% methylene disulfonate (0.5% MMDS) to obtain the lithium ion battery electrolyte of Example 5, and the prepared electrolyte was injected into the soft pack battery, and after standing, formation and capacity separation processes, a lithium ion battery E was obtained.

[0062] Example 6 Preparation of electrolyte: The difference from Example 1 is that 1% of Compound 1 is replaced by 1% of Compound 9 to obtain the lithium ion battery electrolyte of Example 6, and the prepared electrolyte is injected into a soft-pack battery, and after standing, formation and capacity separation processes, a lithium ion battery F is obtained.

[0063] Example 7 Preparation of electrolyte: Different from Example 1, 1% of Compound 1, 1% of lithium bis(fluorosulfonyl)imide (1% LiFSI) and 0.5% of 2-propynyl methanesulfonate (0.5% PMS) were replaced with 0.5% of Compound 9, 0.5% of lithium bis(fluorosulfonyl)imide (0.5% LiFSI) and 0.5% of 2-propynyl methanesulfonate (0.5% PMS) to obtain the lithium ion battery electrolyte of Example 7, and the prepared electrolyte was injected into the soft pack battery, and after standing, formation and capacity separation processes, a lithium ion battery G was obtained.

[0064] Example 8 Preparation of electrolyte: Different from Example 1, 1% of Compound 1, 1% of lithium bis(fluorosulfonyl)imide (1% LiFSI) and 0.5% of 2-propynyl methanesulfonate (0.5% PMS) were replaced with 2% of Compound 9, 1% of lithium fluorosulfonate (1% LiOf) and 0.5% of 2-propynyl methanesulfonate (0.5% PMS) to obtain the lithium ion battery electrolyte of Example 8, and the prepared electrolyte was injected into the soft pack battery, and after standing, formation and capacity division processes, a lithium ion battery H was obtained.

[0065] Example 9 Preparation of electrolyte: Different from Example 1, 1% of Compound 1, 1% of lithium bis(fluorosulfonyl)imide (1% LiFSI) and 0.5% of 2-propynyl methanesulfonate (0.5% PMS) were replaced with 1% of Compound 13, 1% of lithium bis(fluorosulfonyl)imide (1% LiFSI) and 1% of 2-propynyl methanesulfonate (1% PMS) to obtain the lithium ion battery electrolyte of Example 9, and the prepared electrolyte was injected into a soft-pack battery, and after standing, formation and capacity division processes, lithium ion battery I was obtained.

[0066] Example 10 Preparation of electrolyte: Different from Example 1, 1% of Compound 1, 1% of lithium bis(fluorosulfonyl)imide (1% LiFSI) and 0.5% of 2-propynyl methanesulfonate (0.5% PMS) were replaced with 0.5% of Compound 13, 3% of lithium bis(fluorosulfonyl)imide (3% LiFSI) and 2% of 2-propynyl methanesulfonate (2% PMS) to obtain the lithium ion battery electrolyte of Example 10, and the prepared electrolyte was injected into a soft-pack battery. After standing, formation and capacity separation, lithium ion battery J was obtained.

[0067] Embodiment 11 Preparation of electrolyte: Different from Example 1, 1% of Compound 1, 1% of lithium bis(fluorosulfonyl)imide (1% LiFSI) and 0.5% of 2-propynyl methanesulfonate (0.5% PMS) were replaced with 2% of Compound 13, 1% of lithium fluorosulfonate (1% LiOf) and 0.5% of methylene disulfonate (0.5% MMDS) to obtain the lithium ion battery electrolyte of Example 11, and the prepared electrolyte was injected into a soft-pack battery. After standing, formation and capacity separation, a lithium ion battery K was obtained.

[0068] Comparative Example 1 Preparation of electrolyte: Prepare electrolyte in a dry room (the dew point of the preparation environment is lower than -40°C), mix ethyl methyl carbonate (EMC), diethyl carbonate (DEC) and ethylene carbonate (EC) in a volume ratio of 5:2:3 as an organic solvent, and prepare a total of 100 mL. Add LiPF6 to the solvent to make its molar concentration 1.1M / L, add 1% of the total mass of the electrolyte lithium bis(fluorosulfonyl)imide (1% LiFSI) and 0.5% of methanesulfonic acid-2-propynyl alcohol (0.5% PMS), respectively, stir until completely dissolved, and obtain the lithium ion battery electrolyte of comparative example 1. Inject the prepared electrolyte into a soft pack battery, and after standing, formation and volume separation, obtain lithium ion battery L.

[0069] Comparative Example 2 Preparation of electrolyte: Different from Comparative Example 1, 1% of lithium bis(fluorosulfonyl)imide (1% LiFSI) and 0.5% of 2-propynyl methanesulfonate (0.5% PMS) were replaced with 1% of compound 1, and the mixture was stirred until completely dissolved to obtain the lithium ion battery electrolyte of Comparative Example 2. The prepared electrolyte was injected into a soft-pack battery, and after standing, formation and capacity separation processes, a lithium ion battery M was obtained.

[0070] Comparative Example 3 Preparation of electrolyte: Different from Comparative Example 1, 1% of lithium bis(fluorosulfonyl)imide (1% LiFSI) and 0.5% of 2-propynyl methanesulfonate (0.5% PMS) were replaced with 1% of compound 1 and 1% of lithium bis(fluorosulfonyl)imide (1% LiFSI), and the mixture was stirred until completely dissolved to obtain the lithium ion battery electrolyte of Comparative Example 3. The prepared electrolyte was injected into a soft-pack battery, and after standing, formation and capacity separation processes, a lithium ion battery N was obtained.

[0071] Comparative Example 4 Preparation of electrolyte: Different from Comparative Example 1, 1% of lithium bis(fluorosulfonyl)imide (1% LiFSI) and 0.5% of 2-propynyl methanesulfonate (0.5% PMS) were replaced with 1% of compound 1 and 0.5% of 2-propynyl methanesulfonate (0.5% PMS), and the mixture was stirred until completely dissolved to obtain the lithium ion battery electrolyte of Comparative Example 4. The prepared electrolyte was injected into a soft-pack battery, and after standing, formation and capacity separation processes, a lithium ion battery O was obtained.

[0072] Comparative Example 5 Preparation of electrolyte: Different from Comparative Example 1, 1% of 2,2,2-trifluoro-1,3,2-dioxaphosphine heterocyclopentane (structural formula shown below) is further added and stirred until completely dissolved to obtain the lithium ion battery electrolyte of Comparative Example 5. The prepared electrolyte is injected into a soft-pack battery, and after standing, formation and volume separation, a lithium ion battery P is obtained;

[0073] Comparative Example 6 Preparation of electrolyte: Different from Comparative Example 1, 1% of 2,2-difluoro-2-(2,2,2-trifluoroethoxy)-1,3,2-dioxaphosphine heterocyclopentane (structural formula shown below) is further added and stirred until completely dissolved to obtain the lithium ion battery electrolyte of Comparative Example 6. The prepared electrolyte is injected into a soft-pack battery, and after standing, formation and volume separation, a lithium ion battery Q is obtained;

[0074] The positive electrode material of the lithium-ion battery used in this experiment is LiNi 0.5 Co 0.2 Mn 0.3 O2 (the positive electrode material is lithium nickel cobalt manganese oxide, wherein 0.5≤ the molar fraction of nickel is <1), and the negative electrode is artificial graphite. The following experiments are carried out on the batteries obtained in Comparative Examples 1 to 6 and all Examples 1 to 11. The test results are shown in Table 2.

[0075] 1. DC internal resistance test: After the capacity division, the batteries obtained in the examples and comparative examples were subjected to a DC internal resistance test using a DC internal resistance tester.

[0076] 2. High temperature cycle performance test: The batteries obtained in Examples 1 to 11 and Comparative Examples 1 to 6 were charged at 45°C with a constant current and constant voltage of 1C to a voltage of 4.4V and a cut-off current of 0.05C, left for 10 minutes, and discharged at a constant current of 1C to 2.75V. The above is one charge and discharge cycle. The obtained batteries were cyclically charged and discharged at 45°C, and the cycle was terminated when the discharge capacity was less than 80% of the initial discharge capacity.

[0077] 3. High temperature storage performance test: The batteries obtained in Examples 1 to 11 and Comparative Examples 1 to 6 were charged at 1C constant current and constant voltage to a voltage of 4.4V and a cut-off current of 0.05C at 25°C, and the 1C capacity Q and the battery thickness H were recorded respectively; the fully charged battery was stored at 60°C for 28 days, and the battery 1C discharge capacity Q1 and the battery thickness H1 were recorded at 25°C. The battery was charged at 1C constant current and constant voltage to a voltage of 4.4V and a cut-off current of 0.05C, and then discharged at 1C constant current to 2.75V, and the 1C discharge capacity Q2 was recorded, and the capacity retention rate, recovery rate and battery expansion rate of the battery after storage were calculated; The calculation formulas are as follows: Storage capacity retention rate = Q1 / Q×100%; storage capacity recovery rate = Q2 / Q×100%; storage battery expansion rate = (H1-H) / H×100%.

[0078] The electrolyte formulas of Examples 1 to 11 and Comparative Examples 1 to 6 are as follows: Table 1 Table 1

[0079] Table 2

[0080] By comparing Examples 1 to 11 with Comparative Example 1 in conjunction with Table 2, it can be seen that the compound of the structure shown in Formula I of the present invention combined with other additives can effectively reduce the internal resistance of the battery, reduce the thickness expansion rate after storage, inhibit gas production, and improve the high temperature performance of the battery; by comparing Examples 1 to 11 with Comparative Examples 1 to 4, it can be seen that the performance of adding a certain additive alone is far inferior to the electrolyte formula applied for by the present invention; by comparing Examples 1 to 11 with Comparative Examples 5 to 6, it can be seen that the compound of the structure shown in Formula I of the present invention has better performance than the cyclic phosphate compounds mentioned in the background technology.

[0081] The above is only a preferred embodiment of the present invention, and is not any formal or substantial limitation of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the method of the present invention, and these improvements and supplements should also be regarded as the protection scope of the present invention. Any technician familiar with this profession, without departing from the spirit and scope of the present invention, can make some changes, modifications and evolutions of the technical content disclosed above, which are equivalent embodiments of the present invention; at the same time, any changes, modifications and evolutions of any equivalent changes made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A non-aqueous electrolyte, characterized in that: The invention comprises a lithium salt, a non-aqueous organic solvent and a functional additive, wherein the functional additive comprises a compound having a structure shown in formula I, ； in, R1, R2, R3, and R4 are each independently selected from any one of hydrogen, carbonyl, substituted or unsubstituted C1-C10 straight or branched alkyl, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C2-C10 alkynyl, and substituted or unsubstituted C1-C10 alkoxy; or R3 and R4 are bonded to form a bridged ring; A is selected from O or S.

2. The non-aqueous electrolyte according to claim 1, characterized in that R1, R2, R3, and R4 are each independently selected from any one of hydrogen, carbonyl, substituted or unsubstituted C1-C4 straight or branched alkyl, substituted or unsubstituted C2-C4 alkenyl, substituted or unsubstituted C2-C4 alkynyl, and substituted or unsubstituted C1-C4 alkoxy; or R3 and R4 are bonded to form a bridged ring.

3. The non-aqueous electrolyte according to claim 1, characterized in that R1, R2, R3, and R4 are each independently selected from any one of hydrogen, carbonyl, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, sec-butyl, methoxy-substituted methyl, vinyl, propenyl, ethynyl, propynyl, methoxy, and ethoxy; or R3 and R4 are bonded to form a bridged ring.

4. The non-aqueous electrolyte according to any one of claims 1 to 3, characterized in that The compound represented by the formula I is selected from any one or more of the following structures: ； ； 。 5. The non-aqueous electrolyte according to claim 1, characterized in that The functional additives also include other additives, which are selected from one or more combinations of lithium bis(fluorosulfonyl)imide, tetravinylsilane, lithium trifluoromethanesulfonate, lithium fluorosulfonate, 2-propynyl methanesulfonate, methylene disulfonate, N-methyldi(fluorosulfonyl)imide, 4,5-dicyano-2-methylimidazole and 4,5-dicyano-2-ethylimidazole.

6. The non-aqueous electrolyte according to claim 5, characterized in that The other additives are selected from one or more combinations of lithium bis(fluorosulfonyl)imide, lithium fluorosulfonate, 2-propynyl methanesulfonate, methylene methanedisulfonate, 4,5-dicyano-2-methylimidazole and 4,5-dicyano-2-ethylimidazole; And / or, the other additives account for 1% to 5% by mass of the non-aqueous electrolyte.

7. The non-aqueous electrolyte according to claim 1, characterized in that The mass proportion of the compound represented by the structure of Formula I in the non-aqueous electrolyte is 0.5% to 2%; And / or, the lithium salt is selected from the group consisting of one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium hexafluorosilicate, lithium aluminum tetrachloride, lithium bis(oxalatoborate), lithium chloride, lithium bromide, lithium iodide, lithium trifluoromethanesulfonate, and lithium bis(trifluoromethanesulfonate)imide; and / or, the concentration of the lithium salt in the non-aqueous electrolyte is 0.5 mol / L to 2 mol / L; And / or, the non-aqueous organic solvent is selected from cyclic carbonates and / or chain carbonates; And / or, the mass proportion of the non-aqueous organic solvent in the non-aqueous electrolyte is 73% to 93%.

8. The non-aqueous electrolyte according to claim 7, characterized in that The non-aqueous organic solvent is selected from one or more of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, and γ-butyrolactone.

9. A lithium ion battery, characterized in that: The invention comprises a positive electrode, a negative electrode, a separator arranged between the positive electrode and the negative electrode, and a non-aqueous electrolyte, wherein the non-aqueous electrolyte is the non-aqueous electrolyte according to any one of claims 1 to 8.

10. The lithium-ion battery according to claim 9, characterized in that: The negative electrode comprises a negative electrode active material, and the negative electrode active material is selected from a combination of one or more of silicon carbon, silicon oxygen, natural graphite, artificial graphite, lithium titanate, amorphous carbon and lithium metal; And / or, the positive electrode includes a positive electrode active material, and the positive electrode active material is selected from a combination of one or more of lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate and lithium iron manganese phosphate.

11. A battery module, characterized in that: Comprising the lithium ion battery according to claim 9 or 10.

12. A battery pack, characterized in that: Comprising the battery module according to claim 11.

13. An electrical device, characterized in that: It comprises a lithium-ion battery according to claim 9 or 10, wherein the lithium-ion battery is used as a power source for the device, and the power-consuming device includes a mobile device, an electric vehicle, an electric train, a satellite, a ship and an energy storage system.

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