A non-aqueous electrolyte, a lithium ion battery, a battery module, a battery pack, and a power utilization device

Abstract

This invention relates to the field of battery technology, and more particularly to a non-aqueous electrolyte, a lithium-ion battery, a battery module, a battery pack, and an electrical device. The non-aqueous electrolyte comprises a lithium salt, a non-aqueous organic solvent, and functional additives. The functional additives include compounds with the structure shown in Formula I and other additives; R1 and R2 are each independently selected from carbonyl, amide, and dimethylacetamide groups; R3, R4, R5, and R6 are each independently selected from hydrogen and fluorine; n is selected from 1 to 3; other additives are selected from one or more combinations of lithium difluorosulfonylimide, lithium trifluoromethanesulfonate, lithium fluorosulfonate, 2-propynyl methanesulfonate, methanedisulfonate methylene, fluoroethylene carbonate, spiroethylene sulfate, vinylene carbonate, and 1,3-propanesulfonate lactone. This invention, through the synergistic effect of compounds with the structure shown in Formula I and other additives, improves the low-temperature performance, rate performance, and cycle performance of lithium batteries.

Description

Technical Field

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

[0002] Since their commercialization, lithium-ion batteries have been widely used in the power battery field due to their advantages such as high energy density, high power density, long cycle life, and environmental friendliness. At the same time, due to the diverse application environments of end devices, consumers are placing increasingly higher demands on the performance of lithium-ion batteries, such as long cycle life, fast charging, and normal operation under high and low temperature conditions. However, with the increasing market demand for battery performance in low-temperature and fast-charging conditions, traditional electrolytes have revealed numerous problems under these conditions. For example, while traditional carbonate solvents (such as ethylene carbonate) have high dielectric constants, their high viscosity and melting point result in a high desolvation energy barrier for lithium ions during high-rate or low-temperature charging, limiting their rapid migration. Traditional SEI films, mainly composed of lithium carbonate (Li₂CO₃) and alkyl lithium (ROCO₂Li), have poor mechanical strength and ionic conductivity, making them prone to cracking and reconstruction under high-rate charging conditions. This leads to continuous electrolyte decomposition, consuming active lithium ions, reducing battery cycle life, and even triggering lithium plating, resulting in battery capacity decay and safety hazards. Traditional sulfate additives (such as ethylene sulfate) can improve battery performance at low temperatures and rates, but they are prone to absorbing water and hydrolyzing, are thermally unstable, and are difficult to store and transport. Therefore, developing an electrolyte that can meet the requirements for low-temperature and fast-charging performance has become an urgent task to address this challenge. Summary of the Invention

[0003] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a non-aqueous electrolyte, a lithium-ion battery, a battery module, a battery pack, and an electrical device. The non-aqueous electrolyte of this invention, under the synergistic effect of the compound with the structure shown in Formula I and other additives, improves the low-temperature performance, rate performance, and cycle performance of the lithium-ion battery.

[0004] The technical solution of this invention is:

[0005] This invention provides a non-aqueous electrolyte comprising a lithium salt, a non-aqueous organic solvent, and functional additives, wherein the functional additives include compounds with the structure shown in Formula I and other additives.

[0006] ;

[0007] Wherein, R1 and R2 are each independently selected from carbonyl, amide, and dimethylacetamide groups; R3, R4, R5, and R6 are each independently selected from hydrogen and fluorine groups; and n is selected from 1 to 3.

[0008] The other additives are selected from one or more combinations of lithium difluorosulfonylimide, lithium trifluoromethanesulfonate, lithium fluorosulfonate, 2-propynyl methanesulfonate, methylene disulfonate, fluoroethylene carbonate, spiroethylene sulfate, vinylene carbonate, and 1,3-propanesulfonate lactone.

[0009] 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 a non-aqueous electrolyte of the first aspect of the present invention.

[0010] 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.

[0011] A fourth aspect of the present invention provides a battery pack including the battery module described in the third aspect of the present invention.

[0012] A 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 serves as a power source for the electrical device, and the electrical device includes mobile devices, electric vehicles, power tools, electric trains, satellites, ships, and energy storage systems.

[0013] By adopting the aforementioned technical solution, the beneficial effects of the present invention are:

[0014] (1) This invention uses a compound with the structure shown in Formula I as an electrolyte additive. The amide / dimethylacetamide structure in its structure can form a coordination bond with lithium ions, changing the coordination structure of lithium ion solvation in the electrolyte, promoting the participation of anions in the main solvation sheath of lithium ions, and forming an anion-derived SEI film. This SEI film is rich in inorganic components such as LiF, has low impedance and high ionic conductivity, which helps to reduce the desolvation energy barrier of lithium ions and improve ion transport efficiency. The fluorosulfonic acid structure can preferentially form a dense and low-impedance interface film containing F and S elements on the negative electrode surface, which can effectively suppress the occurrence of side reactions and construct a fast lithium ion transport channel. When the compound with the structure shown in Formula I is applied to the lithium-ion battery electrolyte, the various groups interact to further improve the lithium ion transport rate, thereby improving the rate capability and low-temperature performance of the lithium-ion battery.

[0015] (2) Other additives, such as spiroethylene sulfate, also improve low-temperature and rate performance to some extent; vinylene carbonate can polymerize into a film on the negative electrode surface. The compound with the structure shown in Formula I preferentially forms a film on the negative electrode surface compared with other additives. Other additives superimpose and repair the SEI film formed by the compound with the structure shown in Formula I, making the negative electrode interface film more dense and stable, and further improving the low-temperature performance, rate performance and cycle performance of lithium-ion batteries. Detailed Implementation

[0016] The following details the implementation methods of the non-aqueous electrolyte, lithium-ion battery, battery module, battery pack, and electrical device provided by the present invention.

[0017] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for a specific parameter, it is also expected that ranges of 60~110 and 80~120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this application, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0018] [Non-aqueous electrolyte]

[0019] This invention provides a non-aqueous electrolyte comprising a lithium salt, a non-aqueous organic solvent, and functional additives, wherein the functional additives include compounds with the structure shown in Formula I and other additives.

[0020] ;

[0021] R1 and R2 are each independently selected from carbonyl, amide, and dimethylacetamide groups.

[0022] R3, R4, R5, and R6 are each independently selected from hydrogen and fluorine. Optionally, R3, R4, R5, and R6 are each independently selected from hydrogen.

[0023] n is selected from 1 to 3, for example, n is 1, 2, 3. Alternatively, n is selected from 1 to 2, for example, 1, 2.

[0024] This application describes the use of compounds with the structure shown in Formula I in non-aqueous electrolytes for lithium-ion batteries. These compounds exhibit a synergistic effect with other additives, preferentially forming a dense, stable, and low-resistivity interfacial film on the negative electrode surface, effectively suppressing side reactions and accelerating lithium-ion transport. Furthermore, the compounds with the structure shown in Formula I alter the lithium-ion solvation structure in the electrolyte, lowering the lithium-ion desolvation energy barrier and further accelerating lithium-ion transport at the electrode / electrolyte interface. The synergistic effect of these compounds with other additives improves the low-temperature performance, rate performance, and cycle performance of lithium-ion batteries.

[0025] In some embodiments of the present invention, the compound with the structure shown in Formula I is selected from any one or more of the following structures:

[0026] ; ; ; .

[0027] In some embodiments of the present invention, the mass percentage of the compound with the structure shown in Formula I in the non-aqueous electrolyte is 0.5% to 1.5% and any value between them or any two values, optionally 0.5% to 1.0% or 1.0% to 1.5%. The advantage of this range is that it can alter the lithium-ion solvation structure, effectively reduce the lithium-ion desolvation energy barrier, improve the lithium-ion transport rate, and stably form a film on the negative electrode surface. If the proportion of the compound with the structure shown in Formula I is too low (<0.5wt%), it may result in an inability to effectively reduce the lithium-ion desolvation energy barrier and a failure to stably form a film on the negative electrode surface. If the proportion of the compound with the structure shown in Formula I is too high (>1.5wt%), it may increase the electrolyte viscosity, affect lithium-ion transport, thicken the negative electrode film, increase the lithium-ion battery impedance, and degrade performance.

[0028] In some embodiments of the present invention, the other additives are selected from a range of 1.5% to 3% by mass of the non-aqueous electrolyte, or any value between these ranges, or any two values ​​thereof, and may be 1.5% to 2.5%, 2.5% to 3%, 1.5% to 2%, or 2% to 3%. The advantage of these ranges is that they can effectively form a film and improve low-temperature and rate performance. If the proportion of other additives is too low (<1.5wt%), the improvement on lithium-ion battery performance is not significant; if the proportion of other additives is too high (>3wt%), it may increase the electrolyte viscosity, resulting in a thicker film, increased lithium-ion battery impedance, and degraded performance.

[0029] In some embodiments of the present invention, the other additives are selected from one or more combinations of lithium difluorosulfonylimide, lithium trifluoromethanesulfonate, lithium fluorosulfonate, 2-propynyl methanesulfonate, methylene disulfonate, fluoroethylene carbonate, spiroethylene sulfate, vinylene carbonate, and 1,3-propanesulfonate lactone. Optionally, the other additives are selected from one or more combinations of methylene disulfonate, fluoroethylene carbonate, spiroethylene sulfate, vinylene carbonate, and 1,3-propanesulfonate lactone. Preferably, the other additives are selected from spiroethylene sulfate and / or vinylene carbonate.

[0030] In some embodiments of the present invention, the lithium salt is selected from one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium hexafluorosilicate, lithium aluminum chloride, lithium bis(oxalato)borate, lithium chloride, lithium bromide, lithium iodide, lithium trifluoromethanesulfonate, and lithium bis(trifluoromethanesulfonate)imide. Preferably, the lithium salt is selected from lithium hexafluorophosphate (LiPF6).

[0031] In some embodiments of the present invention, the concentration of the lithium salt in the non-aqueous electrolyte is 0.5~2 mol / L and any value or range between therewith, preferably 0.5~1 mol / L, 1~1.2 mol / L, or 1.2~2 mol / L. Preferably, the concentration of the lithium salt in the non-aqueous electrolyte is 1~1.2 mol / L. The lithium salt is a lithium salt in the electrolyte. + The amount of lithium salt is the main source of its influence on the energy density, power density, wide electrochemical window, cycle life, and safety performance of lithium batteries. Too much lithium salt will increase the viscosity of the electrolyte, while too little will fail to provide an adequate amount of lithium ions, both of which will lead to a decrease in ionic conductivity.

[0032] In some embodiments of the present invention, the non-aqueous organic solvent is selected from cyclic carbonates and / or chain carbonates. Preferably, the non-aqueous organic solvent is selected from one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, and γ-butyrolactone. Preferably, the solvent is selected from methyl ethyl carbonate (EMC), ethylene carbonate (EC), and diethyl carbonate (DEC). More preferably, the volume ratio of methyl ethyl carbonate (EMC), ethylene carbonate (EC), and diethyl carbonate (DEC) is (4~6):(2~4):(1~3). The volume ratio of ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) is 5:3:2.

[0033] Further, the solvent in the non-aqueous electrolyte comprises 72 wt% to 92 wt% by mass, or any value between them or any two values, optionally 72 wt% to 80 wt% or 80 wt% to 92 wt%. The electrolyte solvent is mainly composed of a mixture of cyclic carbonate solvents and chain carbonate solvents in a certain proportion. Cyclic carbonate solvents have a higher dielectric constant, which is beneficial for the dissociation of lithium ions, but a large amount will increase the viscosity of the electrolyte and reduce the ionic conductivity. Chain carbonate solvents have a lower viscosity and better electrochemical stability, but a large amount will lead to poorer dissociation of lithium ions.

[0034] The present invention also provides a lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and the non-aqueous electrolyte described in the first aspect of the present invention.

[0035] The positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed 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 may further include a conductive agent and a binder. The positive electrode active material may be selected from 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. Lithium nickel cobalt manganese oxide is preferred. Those skilled in the art can select conductive agents and binders suitable for lithium-ion batteries. The conductive agent may include, for example, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The adhesive may include, for example, at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0036] In some embodiments, the positive electrode can be prepared by dispersing the above-mentioned components for preparing the positive electrode, such as the positive electrode material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode after drying, cold pressing and other processes.

[0037] 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 can be a metal foil or a composite current collector. For example, copper foil can be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The negative electrode active material layer includes a negative electrode active material, and may further include a plasticizer, a conductive agent, and a binder. The negative electrode active material can be selected from one or more of silicon-carbon, silicon-oxygen, natural graphite, artificial graphite, lithium titanate, amorphous carbon, and lithium metal; preferably, the negative electrode active material can be selected from artificial graphite. Those skilled in the art can select plasticizers, conductive agents, and binders suitable for lithium-ion batteries. The conductive agent can 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 adhesive 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).

[0038] In some embodiments, the negative electrode can be prepared by dispersing the components used to prepare the negative electrode, such as the negative electrode material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode after drying, cold pressing and other processes.

[0039] The lithium-ion battery provided in the second aspect of the present invention can be prepared using methods known in the art. For example, a positive electrode, a separator, and a negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes, and then the layers are stacked to obtain a bare cell; the bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte, and after vacuum sealing, settling, formation, shaping, and other processes, a lithium-ion battery is obtained.

[0040] Battery Module

[0041] A third aspect of the present invention provides a battery module comprising any one or more lithium-ion batteries described in the second aspect of the present invention. The number of lithium-ion batteries in the battery module can be adjusted according to the application and capacity of the battery module.

[0042] Battery Pack

[0043] A fourth aspect of the present invention provides a battery pack comprising any one or more battery modules described in the third aspect of the present invention. That is, the battery pack comprises any one or more lithium-ion batteries described in the second aspect of the present invention.

[0044] The number of battery modules in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0045] Electrical appliances

[0046] A fifth aspect of the present invention provides an electrical device comprising any one or more lithium-ion batteries described in the second aspect of the present invention. The lithium-ion batteries can be used as a power source for the electrical device. Preferably, the electrical device may be, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0047] The beneficial effects of the present invention will be further illustrated below with reference to the embodiments.

[0048] To make the inventive objectives, technical solutions, and beneficial effects of this invention clearer, the invention is further described in detail below with reference to embodiments. However, it should be understood that the embodiments of this invention are merely for illustrative purposes and not for limiting the invention, and the embodiments are not limited to those given in the specification. Unless otherwise specified, specific experimental or operational conditions in the embodiments were prepared under conventional conditions or according to the conditions recommended by the material supplier.

[0049] Furthermore, it should be understood that the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, does not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise stated. It should also be understood that the combined connection relationship between one or more devices / apparatus mentioned in this invention does not preclude the existence of other devices / apparatus before or after the combined devices / apparatus, or the insertion of other devices / apparatus between these explicitly mentioned devices / apparatus, unless otherwise stated. Moreover, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or limiting the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0050] In the following embodiments, unless otherwise specified, all the raw materials of the present invention are commercially available or prepared according to conventional methods in the art.

[0051] Unless otherwise specified, all reagents, materials and instruments used in the following embodiments are commercially available.

[0052] The lithium-ion battery positive electrode material used in the comparative examples and embodiments of this invention is lithium nickel cobalt manganese oxide, wherein 0.5 ≤ molar fraction of nickel < 1, and artificial graphite is used as the negative electrode. The electrolyte injection amount of each battery is 4g. The following different electrolytes are selected as comparative examples and embodiments.

[0053] Example 1

[0054] Electrolyte preparation:

[0055] Electrolyte was prepared in a dry room (environmental dew point below -40°C). Ethyl carbonate was liquefied in a 60°C oven and then prepared by mixing ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and liquid ethylene carbonate (EC) at 60°C in a volume ratio of 5:2:3 at room temperature as an organic solvent, totaling 100 mL. LiPF6 with a lithium salt molar concentration of 1.1 M / L was added to this solvent. Compound 1 (structural formula shown in Formula 1), 0.5% spiroethylene sulfate (0.5% SDTD), and 1% vinylene carbonate (1% VC) were added to the above electrolyte, and stirred until completely dissolved to obtain the lithium-ion battery electrolyte of Example 1. The prepared electrolyte was injected into a pouch cell, and after standing, formation, and capacity testing, lithium-ion battery A was obtained.

[0056] Example 2

[0057] Electrolyte preparation:

[0058] Unlike Example 1, 1% of Compound 1 was replaced with 1% of Compound 2 (structural formula shown in Formula 2) to obtain the lithium-ion battery electrolyte of Example 2. The prepared electrolyte was injected into a soft-pack battery, and after standing, formation and capacity testing, lithium-ion battery B was obtained.

[0059] Example 3

[0060] Electrolyte preparation:

[0061] Unlike Example 1, 1% of Compound 1 was replaced with 1% of Compound 3 (structural formula shown in Formula 3) to obtain the lithium-ion battery electrolyte of Example 3. The prepared electrolyte was injected into a soft-pack battery, and after standing, formation and capacity testing, lithium-ion battery C was obtained.

[0062] Example 4

[0063] Electrolyte preparation:

[0064] Unlike Example 1, 1% of compound 1 was replaced with 1% of compound 4 (structural formula shown in Formula 4) to obtain the lithium-ion battery electrolyte of Example 4. The prepared electrolyte was injected into a soft-pack battery, and after standing, formation and capacity testing, lithium-ion battery D was obtained.

[0065] Example 5

[0066] Electrolyte preparation:

[0067] Unlike Example 2, no 1% vinylene carbonate (1% VC) was added, resulting in the lithium-ion battery electrolyte of Example 5. The prepared electrolyte was injected into a pouch cell, and after standing, formation, and capacity testing, lithium-ion battery E was obtained.

[0068] Example 6

[0069] Electrolyte preparation:

[0070] Unlike Example 2, 0.5% spiroethylene sulfate (0.5% SDTD) was not added, resulting in the lithium-ion battery electrolyte of Example 6. The prepared electrolyte was injected into a pouch cell, and after standing, formation and capacity testing, lithium-ion battery F was obtained.

[0071] Example 7

[0072] Electrolyte preparation:

[0073] Unlike Example 2, 1% of Compound 2 was replaced with 0.5% of Compound 2 to obtain the lithium-ion battery electrolyte of Example 7. The prepared electrolyte was injected into a soft-pack battery, and after standing, formation and capacity testing, lithium-ion battery G was obtained.

[0074] Example 8

[0075] Electrolyte preparation:

[0076] Unlike Example 2, 1% of Compound 2 was replaced with 1.5% of Compound 2 to obtain the lithium-ion battery electrolyte of Example 8. The prepared electrolyte was injected into a soft-pack battery, and after standing, formation and capacity testing, lithium-ion battery H was obtained.

[0077] Comparative Example 1

[0078] Electrolyte preparation:

[0079] Electrolyte was prepared in a dry room (environmental dew point below -40℃). Ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and ethylene carbonate (EC) were mixed in a volume ratio of 5:2:3 as an organic solvent, yielding 100 mL. LiPF6 with a lithium salt molar concentration of 1.1 M / L was added to this solvent. Compound 2, comprising 1% of the total mass of the solvent and lithium salt, was then added to the electrolyte and stirred until completely dissolved, yielding the lithium-ion battery electrolyte of Comparative Example 1. The prepared electrolyte was injected into a pouch cell, and after standing, formation, and capacity testing, lithium-ion battery I was obtained.

[0080] Comparative Example 2

[0081] Electrolyte preparation:

[0082] Unlike Comparative Example 1, 0.5% spiroethylene sulfate (0.5% SDTD) and 1% vinylene carbonate (1% VC) by total mass of solvent and lithium salt were added to the above electrolyte 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 testing, lithium-ion battery J was obtained.

[0083] Comparative Example 3

[0084] Electrolyte preparation:

[0085] Unlike Comparative Example 2, 0.1% of Compound 2 was added 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 testing, lithium-ion battery K was obtained.

[0086] Comparative Example 4

[0087] Electrolyte preparation:

[0088] Unlike Comparative Example 2, 3% of Compound 2 needs to be added to obtain the lithium-ion battery electrolyte of Comparative Example 4. The prepared electrolyte is injected into a soft-pack battery, and after standing, formation and capacity testing, lithium-ion battery L is obtained.

[0089] Comparative Example 5

[0090] Electrolyte preparation:

[0091] Unlike Comparative Example 1, 0.2% spiroethylene sulfate (0.2% SDTD) and 0.2% vinylene carbonate (0.2% VC) are added 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 capacity testing, lithium-ion battery M is obtained.

[0092] Comparative Example 6

[0093] Electrolyte preparation:

[0094] Unlike Comparative Example 1, 2% spiroethylene sulfate (2% SDTD) and 4% vinylene carbonate (4% VC) are added 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 capacity testing, lithium-ion battery N is obtained.

[0095] The lithium-ion battery cathode material used in this experiment is LiNi. 0.6 Co 0.2 Mn 0.2 O2 (the positive electrode material is lithium nickel cobalt manganese oxide, where 0.5 ≤ molar fraction of nickel < 1), and the negative electrode is artificial graphite. The following experiments were conducted on the batteries obtained from Comparative Examples 1 to 6 and all Examples 1 to 8, and the test results are shown in Table 2.

[0096] 1. Low-temperature performance test: The batteries obtained in Examples 1-8 and Comparative Examples 1-6 were charged at 25°C with a constant current and constant voltage of 1C to a voltage of 4.4V and a cutoff current of 0.05C, and then discharged at 1C with a constant current to 2.75V. The discharge capacity Q1 was recorded. At 25°C, the batteries were charged at 25°C with a constant current and constant voltage of 1C to a voltage of 4.4V and a cutoff current of 0.05C, and then discharged at -20°C with a constant current of 1C to 2.75V. The discharge capacity Q2 was recorded. The low-temperature discharge capacity retention rate of the batteries was calculated.

[0097] 2. Rate performance test: The batteries obtained in Examples 1-8 and Comparative Examples 1-6 were charged to 4.4V by constant current at 1C, 2C, and 4C respectively, and discharged to 2.75V by constant current at 1C to complete the rate performance test. The batteries were then charged to 4.4V by constant current and constant voltage at 1C with a cutoff current of 0.05C, and discharged to 2.75V by constant current at 1C, 3C, and 5C respectively to complete the rate performance test. The charge and discharge capacity retention rate of the batteries was calculated.

[0098] 3. High-Temperature Cycling Performance Test: The batteries obtained in Examples 1-8 and Comparative Examples 1-6 were charged at 45°C with a constant current and constant voltage of 1C to a voltage of 4.4V and a cutoff current of 0.05C. After resting for 10 minutes, they were discharged at a constant current of 1C to 2.75V. This constituted one charge-discharge cycle. The obtained batteries were then subjected to cyclic charge-discharge at 45°C, and the cycle was terminated when the discharge capacity was lower than 80% of the initial discharge capacity.

[0099] The calculation formulas are as follows:

[0100] -20℃ discharge capacity retention rate = Q2 / Q1 × 100%; Double charge capacity retention rate = (any charge rate capacity / 1C charge capacity) × 100%; Double discharge capacity retention rate = (any discharge rate capacity / 1C discharge capacity) × 100%;

[0101] The electrolyte formulations for Examples 1-8 and Comparative Examples 1-6 are shown in Table 1:

[0102] Table 1

[0103]

[0104] Table 2

[0105]

[0106] Comparing Examples 1-8, it can be seen that the compound with the structure shown in Formula I of the present invention, combined with SDTD and / or VC as additives, can effectively improve the high-temperature cycle performance, low-temperature discharge performance, and high-rate charge-discharge performance of the battery, and the combined use of the three has the best effect. Comparing Comparative Examples 1-2, it can be seen that using the compound with the structure shown in Formula I alone or without using the compound with the structure shown in Formula I is not as effective as using the compound with the structure shown in Formula I in combination with other additives. Comparing Examples 2, 7-8 and Comparative Examples 3-4, it can be seen that the amount of the compound with the structure shown in Formula I added needs to be within the optimal addition range to effectively improve the cell performance, while too much or too little of the compound with the structure shown in Formula I will lead to the battery performance being less than expected. Comparing Examples 2 and Comparative Examples 5-6, it can be seen that the amount of other additives is also very important, and too much or too little of them will also affect the performance.

[0107] In summary, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0108] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any form or substance. It should be noted that those skilled in the art can make various improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention. Any modifications, alterations, and equivalent changes made by those skilled in the art based on the above-disclosed technical content without departing from the spirit and scope of the present invention are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, and evolutions made to the above embodiments based on the essential technology of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A non-aqueous electrolyte, characterized in that, It includes lithium salts, non-aqueous organic solvents, and functional additives, wherein the functional additives include compounds with the structure shown in Formula I and other additives. ； Wherein, R1 and R2 are each independently selected from carbonyl, amide, and dimethylacetamide groups; R3, R4, R5, and R6 are each independently selected from hydrogen and fluorine groups; and n is selected from 1 to 3. The other additives are selected from one or more combinations of lithium difluorosulfonylimide, lithium trifluoromethanesulfonate, lithium fluorosulfonate, 2-propynyl methanesulfonate, methylene disulfonate, fluoroethylene carbonate, spiroethylene sulfate, vinylene carbonate, and 1,3-propanesulfonate lactone.

2. The non-aqueous electrolyte according to claim 1, characterized in that, It also includes one or more of the following conditions: A1) R3, R4, R5, and R6 are each independently selected from hydrogen; A2) n is selected from 1 to 2.

3. The non-aqueous electrolyte according to claim 1, characterized in that, The compound with the structure shown in Formula I is selected from any one or more of the following structures: ； ； ； 。 4. The non-aqueous electrolyte according to claim 1, characterized in that, It also includes one or more of the following conditions: B1) The compound with the structure shown in Formula I accounts for 0.5% to 1.5% of the mass of the non-aqueous electrolyte; B2) The other additives mentioned herein account for 1.5% to 3% of the mass of the non-aqueous electrolyte; B3) The other additives are selected from one or more combinations of methylene disulfonate, fluoroethylene carbonate, spiroethylene sulfate, and 1,3-propanesulfonate lactone.

5. The non-aqueous electrolyte according to claim 1, characterized in that, It also includes one or more of the following conditions: C1) The lithium salt is selected from one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium hexafluorosilicate, lithium aluminum chloride, lithium bis(oxalato)borate, lithium chloride, lithium bromide, lithium iodide, lithium trifluoromethanesulfonate, and lithium bis(trifluoromethanesulfonate)imide. C2) The concentration of the lithium salt in the non-aqueous electrolyte is 0.5 mol / L to 2 mol / L; C3) The non-aqueous organic solvent is selected from cyclic carbonates and / or chain carbonates; The non-aqueous organic solvent in C4) accounts for 72% to 92% of the mass of the non-aqueous electrolyte.

6. The non-aqueous electrolyte according to claim 5, characterized in that, In feature C3), the non-aqueous organic solvent is selected from one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, and γ-butyrolactone.

7. A lithium-ion battery, characterized in that, The invention comprises a positive electrode, a negative electrode, a separator membrane spaced between the positive and negative electrodes, and a non-aqueous electrolyte, characterized in that the non-aqueous electrolyte is the non-aqueous electrolyte according to any one of claims 1 to 6.

8. The lithium-ion battery according to claim 7, characterized in that, It also includes one or more of the following conditions: D1) The negative electrode includes a negative electrode active material, which is selected from one or more combinations of silicon carbon, silicon oxide, natural graphite, artificial graphite, lithium titanate, amorphous carbon and lithium metal; D2) The positive electrode includes a positive electrode active material, which is selected from one or more combinations 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.

9. A battery module, characterized in that, Including the lithium-ion battery according to claim 7 or 8.

10. A battery pack, characterized in that, Includes the battery module according to claim 9.

11. An electrical appliance, characterized in that, Includes a lithium-ion battery according to claim 7 or 8, wherein the lithium-ion battery is used as a power source for the device, and the device includes mobile devices, electric vehicles, electric trains, satellites, ships, and energy storage systems.

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