Electrolyte additive, electrolyte and lithium ion battery

Abstract

The application relates to an electrolyte additive, an electrolyte and a lithium ion battery. The electrolyte additive comprises a first additive, the first additive comprises a fluorobenzenboronic acid compound, the mass percentage of the fluorobenzenboronic acid compound in the electrolyte is m1%, and m1 is 0.5-10. The scheme provided by the application can form a tough CEI film with high LiF and LiB x O y content on the positive electrode, and the generated LiF is distributed in steps on the positive electrode surface, so that the relative stability of the inner layer CEI film of the cathode can be ensured, and the cycle life of the battery is improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to electrolyte additives, electrolytes and lithium-ion batteries. Background Art

[0002] As the limiting voltage of the positive electrode material continues to increase (especially 4.3V+), the gram capacity of the battery material gradually increases, while the high-temperature performance of the battery deteriorates seriously, and long cycle life cannot be guaranteed. Especially during long-term cyclic charge and discharge under high voltage, the volume of the positive electrode material will expand and cause serious cracks. The solvent in the electrolyte enters the interior of the positive electrode material, destroying the structure, and ultimately causing serious capacity attenuation problems.

[0003] In the related art, it is known that by covering the surface of the positive electrode material with a high-strength CEI film, cracks caused by volume changes can be suppressed or reversibly recovered, which will significantly improve the cycle life of the positive electrode even at high cut-off voltages.

[0004] Therefore, how to form a high-strength CEI film to meet the requirements of high energy density of batteries is a research problem in the battery field. Summary of the Invention

[0005] In order to solve or partially solve the problems existing in the related art, the present application provides an electrolyte additive, an electrolyte and a lithium ion battery, which can form a high LiF and LiB x O y The tough CEI film with high content and the generated LiF are distributed in a stepped manner on the surface of the positive electrode, which can ensure the relative stability of the CEI film in the inner layer of the cathode and improve the cycle life of the battery.

[0006] In a first aspect, the present application provides an electrolyte additive, including a first additive, wherein the first additive comprises a fluorophenylboric acid compound, and the mass percentage of the fluorophenylboric acid compound in the electrolyte is m1%, and m1 is 0.5-10.

[0007] As an optional embodiment, the structural formula of the fluorophenylboronic acid compound is as follows:

[0008]

[0009] In structural formula 1, R1-R5 are each independently selected from one of C1-C10 alkanes, C1-C10 halogenated alkanes, fluorine atoms, cyano groups, and hydrogen atoms, and R1-R5 contain at least one fluorine atom; R6 and R7 are each independently selected from one of C1-C10 alkoxy groups, C1-C10 halogenated alkoxy groups, and hydroxy groups.

[0010] As an optional embodiment, the first additive comprises at least one of the following fluorophenylboronic acid compounds:

[0011]

[0012]

[0013] As an optional embodiment, the electrolyte additive further includes a second additive, and the second additive includes a sultone compound.

[0014] As an optional embodiment, the structural formula of the sultone compound is as follows:

[0015]

[0016] In structural formula 2, R8 and R9 are each independently selected from one of a C1-C10 saturated alkane, a halogen atom, and a hydrogen atom; M and Q are selected from C and O, respectively.

[0017] As an optional embodiment, the second additive comprises at least one of the following sultone compounds:

[0018]

[0019] Compound 2-5.

[0020] As an optional embodiment, the amounts of the fluorophenylboronic acid compound and the sultone compound meet the following requirements:

[0021] 2(m1+m2)≥A

[0022] The molar ratio of Ni element in the positive electrode active material is A, and the mass percentage of the sultone compound in the electrolyte is m2%.

[0023] As a preferred embodiment, A is 1-9.

[0024] As a preferred embodiment, m2 is 1-10.

[0025] In a second aspect, the present application provides an electrolyte comprising a lithium salt, a non-aqueous organic solvent and an additive, wherein the additive comprises the aforementioned electrolyte additive.

[0026] In a third aspect, the present application provides a lithium-ion battery comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the electrolyte is the electrolyte described above.

[0027] As an optional embodiment, the positive electrode active material of the positive electrode is selected from lithium cobalt oxide LiCoO2, nickel manganese cobalt oxide ternary material N a C b M c, one or more of lithium ferrous phosphate LiFePO4, and manganese oxide LiMn2O4.

[0028] As a preferred embodiment, the positive electrode active material is selected from the ternary material N a C b M c , and the nickel manganese cobalt oxide lithium ternary material N a C b M c Chinese: a+b+c=10.

[0029] More preferably, a / (b+c)>1.

[0030] The technical solution provided by this application may have the following beneficial effects:

[0031] The fluorophenylboronic acid compound contained in the first additive of the present invention is a strong cathode ligand, which can effectively prevent the electrolyte from damaging the cathode material and can participate in the formation of a high-toughness CEI film with a high content of LiF and LiBxOy. In addition, the present invention can make the LiF and LiBxOy content in the generated CEI film high by controlling the mass percentage of the fluorophenylboronic acid compound in the electrolyte to be 0.5% to 10%. x O y The content of LiF and LiB in the inner and outer layers of the cathode surface is distributed in a stepped manner. This is because the formation of the CEI film is not only affected by the film-forming time of the inner and outer layers, but also related to the content of fluorophenylboronic acid compounds. On the one hand, the film-forming stage includes the inner layer film-forming stage and the outer layer film-forming stage. In the film-forming stage, the CEI film is first formed in the inner layer of the cathode, and the film-forming time of the inner layer is relatively short. Therefore, the LiF and LiB in the generated CEI film are relatively high. x O y The content of LiF and LiB in the outer layer is relatively low; subsequently, as the chemical formation proceeds, the outer layer is continuously formed on the basis of the inner layer, and the outer layer takes a relatively long time to form, which will make the outer layer have a relatively low content of LiF and LiB in the inner layer. x O y The content is higher, thus showing the inner layer of LiF and LiB on the cathode surface. x O y The content of LiF and LiBxOy in the outer layer is small, and the content of LiF and LiBxOy in the outer layer is large. x O y A higher content can prevent the inner CEI film from being damaged, improve the stability of the inner CEI, and thus increase the cycle life of the battery; on the other hand, if the content of fluorophenylboronic acid compounds is too low, they will be quickly consumed in the early stage of film formation (inner film formation stage), which may cause the LiF and LiB contained in the outer film to be depleted. x O yIf the content of fluorophenylboronic acid compounds is too high, the fluorophenylboronic acid compounds at the cathode interface will be replenished too quickly, which may lead to excessive replenishment of fluorophenylboronic acid compounds in the inner film-forming stage, which cannot be distinguished from the fluorophenylboronic acid compounds replenished in the outer film-forming stage, making it difficult to form LiF and LiB in the CEI film. x O y Therefore, too high or too low a content is not conducive to the LiF and LiB x O y In addition, phenylboronic acid compounds can reduce the solvation effect between the solvent and Li+, promote the desolvation effect of Li+, and improve the ion transfer rate.

[0032] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. DETAILED DESCRIPTION

[0033] The embodiments of the present application will be described in more detail below. Although the embodiments of the present application are shown, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present application more thorough and complete, and to fully convey the scope of the present application to those skilled in the art.

[0034] The terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit this application. As used in this application and the appended claims, the singular forms "a," "an," "the," and "the" are intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0035] It should be understood that although the terms "first", "second", "third", etc. may be used in this application to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of this application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0036] In related technologies, it is known that coating the surface of cathode materials with a high-strength CEI film can suppress or reversibly recover cracks caused by volume changes, significantly improving the cycle life of the cathode even at high cutoff voltages. Therefore, how to form a high-strength CEI film that meets the requirements of high energy density batteries remains a research challenge in the battery field.

[0037] In view of the above problems, the present invention provides an electrolyte additive that can form a high LiF and LiB electrolyte at the positive electrode of the battery. x O y The tough CEI film with high content and the generated LiF are distributed in a stepped manner on the surface of the positive electrode, which can ensure the relative stability of the CEI film in the inner layer of the cathode and improve the cycle life of the battery.

[0038] An embodiment of the present application provides an electrolyte additive, including a first additive, the first additive containing a fluorophenylboric acid compound, and the mass percentage of the fluorophenylboric acid compound in the electrolyte is m1%, where m1 is 0.5-10.

[0039] The fluorophenylboronic acid compound contained in the first additive in the embodiment of the present application is a strong cathode ligand, which can effectively prevent the electrolyte from damaging the cathode material and can participate in the formation of a high-toughness CEI film with a high content of LiF and LiBxOy. In addition, the embodiment of the present application controls the mass percentage of the fluorophenylboronic acid compound in the electrolyte to be 0.5% to 10%, which can make the LiF and LiB in the generated CEI film x O y The content of LiF and LiB in the inner and outer layers of the cathode surface is distributed in a stepped manner. This is because the formation of the CEI film is not only affected by the film-forming time of the inner and outer layers, but also related to the content of fluorophenylboronic acid compounds. On the one hand, the film-forming stage includes the inner layer film-forming stage and the outer layer film-forming stage. In the film-forming stage, the CEI film is first formed in the inner layer of the cathode, and the film-forming time of the inner layer is relatively short. Therefore, the LiF and LiB in the generated CEI film are relatively high. x O y The content of LiF and LiB in the outer layer is relatively low; subsequently, as the chemical formation proceeds, the outer layer is continuously formed on the basis of the inner layer, and the outer layer takes a relatively long time to form, which will make the outer layer have a relatively low content of LiF and LiB in the inner layer. x O y The content is higher, thus showing the inner layer of LiF and LiB on the cathode surface. x O y The content of LiF and LiBxOy in the outer layer is small, and the content of LiF and LiBxOy in the outer layer is large. x O yA higher content can prevent the inner CEI film from being damaged, improve the stability of the inner CEI, and thus increase the cycle life of the battery; on the other hand, if the content of fluorophenylboronic acid compounds is too low, they will be quickly consumed in the early stage of film formation (inner film formation stage), which may cause the LiF and LiB contained in the outer film to be depleted. x O y If the content of fluorophenylboronic acid compounds is too high, the fluorophenylboronic acid compounds at the cathode interface will be replenished too quickly, which may lead to excessive replenishment of fluorophenylboronic acid compounds in the inner film-forming stage, which cannot be distinguished from the fluorophenylboronic acid compounds replenished in the outer film-forming stage, making it difficult to form LiF and LiB in the CEI film. x O y Therefore, too high or too low a content is not conducive to the LiF and LiB x O y In addition, phenylboronic acid compounds can reduce the solvation effect between the solvent and Li+, promote the desolvation effect of Li+, and improve the ion transfer rate.

[0040] As an optional embodiment, the structural formula of the fluorophenylboronic acid compound is as follows:

[0041]

[0042]

[0043] In structural formula 1, R1-R5 are each independently selected from one of C1-C10 alkanes, C1-C10 halogenated alkanes, fluorine atoms, cyano groups, and hydrogen atoms, and R1-R5 contain at least one fluorine atom; R6 and R7 are each independently selected from one of C1-C10 alkoxy groups, C1-C10 halogenated alkoxy groups, and hydroxy groups.

[0044] In the embodiment of the present application, R1, R2, R3, R4, and R5 can be the same or different groups, but at least one of R1, R2, R3, R4, and R5 is selected from a fluorine atom, so that the film-formed product contains LiF. R6 and R7 can also be the same or different groups.

[0045] As a preferred embodiment, the first additive comprises at least one of the following fluorophenylboronic acid compounds:

[0046]

[0047]

[0048] In the examples of the present application, compounds 1-4, 1-5, and 1-7 have better improvements on the high-temperature cycle performance and high-temperature storage performance of the battery, and compound 1-5 has the best performance improvement on the battery. This is because compound 1-5 contains more F atoms, and the molar ratio of F atoms is larger at the same content, which makes it easier to generate LiF that is beneficial to the CEI film.

[0049] As an optional embodiment, the electrolyte additive further includes a second additive, and the second additive includes a sultone compound.

[0050] The second additive in the embodiments of the present application comprises a sultone compound, a sulfur-based compound that primarily participates in the formation of the SEI film during the surface formation phase of the negative electrode, forming sulfur compounds such as lithium alkylsulfonates. These compounds prevent the electrolyte from undergoing continuous reduction and decomposition on the negative electrode surface and provide pathways for the insertion and removal of lithium ions. Furthermore, the first and second additives act synergistically. The first additive participates in the formation of the CEI film, inhibiting the dissolution of cathode transition metals and reducing the content of Ni, Co, and Mn metal ions in the anode. The second additive forms a stable interfacial film, preventing damage to the anode from small amounts of transition metals. The synergistic use of these two additives enhances the stability of the anode cycle.

[0051] As a preferred embodiment, the structural formula of the sultone compound is as follows:

[0052]

[0053] In structural formula 2, R8 and R9 are each independently selected from one of a C1-C10 saturated alkane, a halogen atom, and a hydrogen atom; M and Q are selected from C and O, respectively.

[0054] In the embodiment of the present application, R8 and R9 can be selected from the same group or different groups, and the present application does not limit this.

[0055] As a preferred embodiment, the second additive comprises at least one of the following sultone compounds:

[0056]

[0057]

[0058] Compound 2-5.

[0059] In the embodiments of the present application, compound 2-1, compound 2-2 and compound 2-4 work synergistically with compound 1-5 to better improve the high-temperature cycling performance and high-temperature storage performance of the battery. Compound 2-1 works synergistically with compound 1-5 to best improve the performance of the battery. This is because compound 2-1 can help generate a denser and more stable SEI film.

[0060] As an optional embodiment, the amounts of the fluorophenylboronic acid compound and the sultone compound meet the following requirements:

[0061] 2(m1+m2)≥A

[0062] The molar ratio of Ni element in the positive electrode active material is A, and the mass percentage of the sultone compound in the electrolyte is m2%.

[0063] In the embodiment of the present application, the molar ratio A of the Ni element in the ternary positive electrode active material refers to the molar ratio of the Ni element. For example, the positive electrode active material is a lithium nickel manganese cobalt ternary material N a C b M c , the molar ratio A of Ni element in the positive electrode active material is a.

[0064] Since the higher the Ni content in the positive electrode active material, the stronger the oxidizing property of the electrolyte and the easier it is to oxidize the electrolyte, m1+m2 represents the synergistic effect of the fluorophenylboric acid compound and the sultone compound in the first additive and the second additive. When 2(m1+m2)≥A, it means that after the values ​​of m1, m2, and A are determined, the synergistic effect of the fluorophenylboric acid compound and the sultone compound in the first additive and the second additive is not less than the oxidizing effect of the Ni content on the electrolyte, and then the electrolyte has a better protective effect on the positive electrode.

[0065] Preferably, A is 1-9.

[0066] In the embodiments of the present application, A can be 1, 3, 5, 6, 8, 9 or any value within the above-defined range, and the present application does not impose any limitation on this.

[0067] Preferably, m2 is 1-10.

[0068] In the embodiment of the present application, m2 can be 1, 2, 5, 10 or any value within the above-defined range, and the present application does not impose any limitation on this.

[0069] If m2 is too large, the impedance will deteriorate significantly and the cycle capacity will deteriorate; if m2 is too small, the positive electrode protection effect will be poor.

[0070] Corresponding to the aforementioned application function implementation method embodiment, the present application also provides an electrolyte, a lithium-ion battery and corresponding embodiments.

[0071] An embodiment of the present application provides an electrolyte comprising a lithium salt, a non-aqueous organic solvent, and an additive, wherein the additive comprises the aforementioned electrolyte additive.

[0072] In the embodiment of the present application, the lithium salt is selected from at least one of an organic lithium salt and an inorganic lithium salt.

[0073] Preferably, the lithium salt is selected from at least one of compounds containing fluorine and lithium.

[0074] Preferably, the lithium salt is selected from at least one of hexafluorophosphate, hexafluoroarsenate, perchlorate, trifluorosulfonyl lithium, difluoro(trifluoromethylsulfonyl)imide lithium, tris(trifluoromethylsulfonyl)methyl lithium, and bis(trifluoromethylsulfonyl)imide lithium.

[0075] Preferably, the lithium salt concentration is 0.5 M to 1.5 M. If the lithium salt concentration is too low, the conductivity of the electrolyte is low, which will affect the rate and cycle performance of the entire battery system; if the lithium salt concentration is too high, the viscosity of the electrolyte is too high, which will also affect the rate of the entire battery system.

[0076] More preferably, the concentration of the lithium salt is 0.8M to 1.3M.

[0077] Preferably, the non-aqueous organic solvent is selected from at least two of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl formate, ethyl formate, ethyl propionate, propyl propionate, methyl butyrate, and tetrahydrofuran.

[0078] The additive further includes at least one of a sulfonate compound, a fluorocarbonate compound, and a nitrile compound.

[0079] An embodiment of the present application also provides a lithium-ion battery, comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the electrolyte is the electrolyte described above.

[0080] In the embodiments of the present application, the positive electrode includes a positive electrode current collector and a positive electrode active slurry layer located on the positive electrode current collector, wherein the positive electrode active slurry layer includes a positive electrode active material; the negative electrode includes a negative electrode current collector and a negative electrode active slurry layer located on the negative electrode current collector, wherein the negative electrode active slurry layer includes a negative electrode active material. The specific types of the positive electrode active material, positive electrode binder, and negative electrode active material are not subject to specific limitations and can be selected based on requirements.

[0081] As an optional embodiment, the negative electrode active material can be selected from graphite and / or silicon, such as natural graphite, artificial graphite, mesophase microcarbon beads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel structured lithiated TiO2-Li4Ti5O 12 , Li-Al alloys can be used as negative electrode active materials.

[0082] As an optional embodiment, the positive electrode active material of the positive electrode is selected from lithium cobalt oxide LiCoO2, nickel manganese cobalt oxide ternary material N a C b M c, one or more of lithium ferrous phosphate LiFePO4, and manganese oxide LiMn2O4.

[0083] Preferably, the positive electrode active material is selected from the ternary material N a C b M c , and the nickel manganese cobalt oxide lithium ternary material N a C b M c Chinese: a+b+c=10.

[0084] Nickel manganese cobalt oxide lithium ternary material N a C b M c For example, a+b+c=10, and the molar ratio A of the Ni element in the positive electrode active material is a.

[0085] More preferably, a / (b+c)>1.

[0086] For example, when a=8, b=1, c=1, a / (b+c)>1; when a=6, b=2, c=2, a / (b+b)>1; when a=5, b=2, c=3, a / (b+c)=1; when a=3.33, b=3.33, c=3.33, a / (b+c)<1.

[0087] In order to further understand the present invention, the present application is described below in conjunction with examples. These examples are only used to illustrate the present application and are not used to limit the scope of the present application.

[0088] 1. Preparation of batteries

[0089] (1) Preparation of electrolyte

[0090] EC / PC / EMC were mixed in a mass ratio of 2 / 1 / 7 to serve as the organic solvent. The additive FEC was added to the organic solvent and mixed thoroughly. LiPF6 was then added to obtain a mixed solution with a LiPF6 concentration of 1.1 mol / L, which served as the electrolyte for Comparative Example 1 in Table 1. The first and second additives were then added to the mixed solution according to the formula in Table 1 to prepare the electrolytes for the various Examples and Comparative Examples. FEC is fluoroethylene carbonate.

[0091] (2) Production of positive electrode:

[0092] The nickel-cobalt-manganese ternary positive electrode active material, conductive agent CNT, and binder polyvinylidene fluoride were thoroughly stirred in N-methylpyrrolidone at a ratio of 97:1.5:1.5 by weight to form a uniform positive electrode slurry. This slurry was coated onto an aluminum foil positive electrode current collector, dried, and cold-pressed to produce a positive electrode sheet. The molar ratio of Ni in the nickel-cobalt-manganese ternary positive electrode active material was set according to Table 1.

[0093] (3) Production of negative electrode sheet:

[0094] Graphite (the negative electrode active material), acetylene black (the conductive agent), styrene-butadiene rubber (the binder), and sodium carboxymethyl cellulose (the thickener) were thoroughly mixed in a suitable amount of deionized water at a mass ratio of 95:2:2:1 to form a uniform negative electrode slurry. This slurry was then applied to the negative electrode current collector, Cu foil, dried, and cold-pressed to obtain the negative electrode sheet.

[0095] (4) Production of lithium-ion batteries:

[0096] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator positioned between the positive and negative electrodes to provide isolation. The cells are then wound together to form a bare cell. The bare cell is placed in an outer packaging bag. The electrolytes listed in Table 1 are then injected into the dried cells. After vacuum packaging, resting, formation, and shaping, the lithium-ion battery is complete.

[0097] Table 1 Recipe

[0098]

[0099]

[0100] 2. Performance Testing

[0101] (1) High temperature cycle test of batteries

[0102] Test method: Place the battery in an environment of 45±2 degrees, follow the standard charge and discharge cycle, cycle rate 1C, charging voltage 3.0-4.3V, and calculate the capacity retention rate of the battery after the cycle. The calculation formula is as follows:

[0103] The n-th cycle capacity retention rate (%) = (n-th cycle discharge capacity) / (first cycle discharge capacity)*100%.

[0104] (2) High temperature storage test of batteries:

[0105] Test method: Charge the divided battery cells to 4.3V at room temperature with a current of 0.5C. Place the fully charged battery in an environment of 85 degrees for 12 hours, measure the thickness expansion rate, and after returning to room temperature, discharge the battery cells to 3.0V with a current of 0.5C and record the discharge capacity.

[0106] The battery test results are shown in Table 2.

[0107] Table 2 Test results

[0108]

[0109]

[0110]

[0111] Combining the data in Tables 1 and 2, it can be seen from the data of Examples 1 to 14 that when a fluorophenylboronic acid compound is selected as the first additive and a sultone compound is selected as the second additive, the high-temperature cycling and high-temperature storage performance of the battery can be improved. Further combining the data of Examples 15 to 18, and Comparative Examples 1 to 7, it can be seen that when m1 is 0.5 to 10 and m2 is 1 to 10, the high-temperature cycling and high-temperature storage performance of the battery can be effectively improved. Further combining the data of Examples 20 to 23, and Comparative Example 8, it can be seen that when 2(m1+m2)-A≥0 is satisfied, the high-temperature cycling and high-temperature storage performance of the battery can be further effectively improved.

[0112] According to the data of Example 23, Comparative Examples 9 and 10, the selected nickel manganese cobalt lithium ternary material N a C b M c In the embodiment, when a / (b+c)>1 is satisfied, the high-temperature cycle and high-temperature storage performance of the battery can be effectively improved.

[0113] 3. ICP test of negative electrode

[0114] ICP test of negative electrode sheets was performed on Example 5, Example 15 to Example 17, and Comparative Example 1 and Comparative Example 2. The test process is as follows:

[0115] First, the cycled and stored battery cells were discharged to 3.0 V, the battery cells were disassembled to remove the negative electrode sheets, 0.2 g of the electrode sheet powder was scraped off, and an ICP test was performed after strong acid digestion. The test results are shown in Table 3.

[0116] Table 3 ICP test results of negative electrode

[0117]

[0118]

[0119] Further combined with the data in Table 3, it can be seen that the high-temperature cycling and high-temperature storage performance of Example 5 are the best, that is, the combination of 1% compound 1-5 and 5% additive 2-1 has the best effect, and after high-temperature cycling and high-temperature storage under this combination, the dissolution level of transition metal ions in the positive electrode sheet is the lowest, and the protection effect on the positive electrode is the best.

[0120] Although the present application has been described with reference to preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for the elements thereof without departing from the scope of the present application. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present application without departing from the essential scope of the present application. Therefore, the present application is not intended to be limited to the particular embodiment disclosed as the best mode contemplated for carrying out the present application, but rather, the present application is intended to include all embodiments falling within the scope of the appended claims.

[0121] All ranges disclosed in this application are inclusive of the endpoints, and the endpoints are combinable with each other.

[0122] The embodiments of the present application have been described above. The above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is selected to best explain the principles of the embodiments, their practical applications, or improvements to the technology in the market, or to enable other persons skilled in the art to understand the embodiments disclosed herein.

Claims

1. An electrolyte additive, characterized in that The electrolyte comprises a first additive, wherein the first additive comprises a fluorophenylboric acid compound, and the mass percentage of the fluorophenylboric acid compound in the electrolyte is m1%, where m1 is 0.5 to 10; the structural formula of the fluorophenylboric acid compound is as follows: Structural formula 1 In structural formula 1, R1-R5 are each independently selected from one of a C1-C10 alkane, a C1-C10 halogenated alkane, a fluorine atom, a cyano group, and a hydrogen atom, and R1-R5 contain at least one fluorine atom; R6 and R7 are each independently selected from one of a C1-C10 alkoxy group, a C1-C10 halogenated alkoxy group, and a hydroxyl group; The electrolyte additive further includes a second additive, the second additive comprising a sultone compound; the structural formula of the sultone compound is as follows: Structural Formula 2 In structural formula 2, R8 and R9 are each independently selected from a C1-C10 saturated alkane, a halogen atom, and a hydrogen atom; M and Q are each selected from C and O; The amounts of the fluorophenylboronic acid compound and the sultone compound satisfy: 2(m1+m2)≥A The molar ratio of Ni element in the positive electrode active material is A, and the mass percentage of the sultone compound in the electrolyte is m2%.

2. The electrolyte additive according to claim 1, characterized in that The first additive comprises at least one of the following fluorophenylboronic acid compounds: Compound 1-1 Compound 1-2 Compounds 1-3 Compounds 1-4 Compounds 1-5 Compounds 1-6 Compounds 1-7 Compounds 1-8 Compounds 1-9 Compounds 1-10.

3. The electrolyte additive according to claim 1, characterized in that The second additive comprises at least one of the following sultone compounds: Compound 2-1 Compound 2-2 Compound 2-3 Compounds 2-4 Compound 2-5.

4. The electrolyte additive according to claim 1, characterized in that A is 1 to 9; and / or m2 is 1 to 10.

5. An electrolyte, characterized in that The electrolyte comprises a lithium salt, a non-aqueous organic solvent and an additive, wherein the additive comprises the electrolyte additive according to any one of claims 1 to 4.

6. A lithium-ion battery, characterized in that: A positive electrode, a negative electrode, a separator and an electrolyte, wherein the electrolyte is the electrolyte according to claim 5.

7. The lithium-ion battery according to claim 6, characterized in that The positive electrode active material of the positive electrode is selected from lithium cobalt oxide LiCoO2, nickel manganese cobalt oxide lithium ternary material N a C b M c , one or more of lithium ferrous phosphate LiFePO4, and manganese oxide LiMn2O4.

8. The lithium-ion battery according to claim 7, characterized in that The positive electrode active material is selected from the nickel manganese cobalt lithium ternary material N a C b M c , and the nickel manganese cobalt oxide lithium ternary material N a C b M c Chinese: a+b+c=10.

9. The lithium-ion battery according to claim 8, characterized in that a / (b+c)>1.

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