Additive composition, electrolyte and lithium ion battery

Abstract

The invention relates to an additive composition, an electrolyte and a lithium ion battery. The additive composition comprises a sulfate compound, a phosphazene compound and a trimethylsilyl ester compound in a mass ratio of (0.1-5): (1-10): (1-5). The phosphazene compound in the additive provided by the invention has flame retardance, so that the thermal stability and safety are greatly improved; besides, the phosphazene compound and the trimethylsilyl ester compound can remove trace water in the electrolyte and inhibit hydrolysis of lithium salt in the electrolyte, so that generation of HF is reduced, increase of acidity and chromaticity in the long-time storage process of the electrolyte can be inhibited, the lithium salt additive and the sulfate additive have a synergistic effect, stable passive films are formed on the surfaces of the positive electrode and the negative electrode, and the service life of the electrolyte is prolonged. Electrolyte decomposition and transition metal ion dissolution are inhibited, and the cycle performance, high-temperature performance and safety of the battery using the additive are improved.

Description

Technical Field

[0001] This application relates to the field of electrolyte additive technology, specifically to an additive composition, an electrolyte, and a lithium-ion battery. Background Technology

[0002] Lithium-ion batteries, with their advantages of high energy density, long cycle life, and high safety, have become the core energy storage medium in portable electronic devices and electric vehicles. Simultaneously, as a key technology for solving the intermittency problem of renewable energy sources such as photovoltaics and wind power, lithium-ion batteries have achieved large-scale engineering applications in energy storage. With the continuous expansion of battery application fields, developing high-energy-density and high-safety lithium-ion battery systems has become an important research direction in energy materials. However, the performance degradation of lithium-ion batteries under high-temperature environments has become a key bottleneck restricting their safety and long cycle life. High temperatures lead to a sharp drop in capacity and accelerated aging, significantly shortening their lifespan. The performance degradation of lithium secondary batteries at high temperatures is caused by multiple factors: on the one hand, the electrolyte is prone to decomposition at high temperatures, destroying its stability; on the other hand, high temperatures cause metal ions in the lithium transition metal oxide of the cathode to dissolve, leading to structural damage to the cathode material; in addition, excessively high local temperatures inside the battery may cause the SEI film to rupture or fail, resulting in increased interfacial impedance and even inducing thermal runaway. Meanwhile, high-voltage cathode materials (such as high-nickel ternary NCM811 and lithium-rich manganese-based materials) have been developed to improve energy density. However, the combined effects of high temperature and high pressure can exacerbate the oxidative decomposition of the electrolyte at the positive electrode interface, thereby accelerating battery failure.

[0003] Electrolyte additives are one of the key means to solve the problem of poor high-temperature stability of batteries, but traditional electrolyte additives often fail to meet complex performance requirements such as safety and high-temperature cycle stability. Summary of the Invention

[0004] Therefore, it is necessary to provide an additive composition, electrolyte, and lithium-ion battery with good safety and high-temperature cycle stability.

[0005] This application provides an additive composition comprising a sulfate ester compound, a phosphazene compound, and a trimethylsilyl ester compound in a mass ratio of (0.1~5):(1~10):(1~5).

[0006] In one embodiment, the sulfate ester compound includes one or more of vinyl sulfate, 4-methyl vinyl sulfate, vinyl disulfide, propylene sulfate, 1,3-propanediol cyclic sulfate, pentaerythritol bicyclic sulfate, diethyl sulfate, and dipropyl sulfate.

[0007] In one embodiment, the chemical formula of the phosphazene compound satisfies the following formula (1-1). Or formula (1-2) ;

[0008] R1~R 11 Each is independently selected from one of halogens, substituted or unsubstituted C1-C5 alkoxy groups, and phenoxy groups.

[0009] In one embodiment, the chemical formula of the phosphazene compound satisfies formula (1-1), wherein R1 to R6 are each independently one of a halogen, a C1 to C3 alkoxy group, and a phenoxy group.

[0010] In one embodiment, the phosphazene compound includes one or more of hexafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, pentafluoro(phenoxy)cyclotriphosphazene, and hexamethoxycyclotriphosphazene.

[0011] In one embodiment, the trimethylsilyl ester compound includes one or more of bis(trimethylsilane) maleate, bis(trimethylsilyl) adipic acid, and bis(trimethylsilyl)butynediate.

[0012] This application provides an electrolyte, wherein the solvent of the electrolyte comprises an additive composition as described above and an organic solvent in a mass ratio of (1~15):100.

[0013] In one embodiment, the organic solvent includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl formate, ethyl formate, ethyl acetate, ethyl propionate, γ-butyrolactone, ethylene glycol dimethyl ether, and 1,3-dioxane.

[0014] In one embodiment, the electrolyte further includes 0.5 mol / L to 1.5 mol / L of lithium salt.

[0015] This application also provides a lithium-ion battery, including a positive electrode, a negative electrode, a separator, and an electrolyte. The separator is disposed between the positive electrode and the negative electrode. The positive electrode, the negative electrode, and the separator are immersed in the electrolyte, which includes the electrolyte as described above.

[0016] The phosphazene compounds in the additives provided in this application have flame retardant properties, which greatly improve thermal stability and safety. In addition, phosphazene compounds and trimethylsilyl ester compounds can remove trace amounts of water in the electrolyte, inhibit the hydrolysis of lithium salt in the electrolyte to a certain extent, keep the lithium salt within a suitable concentration range, thereby reducing the generation of HF, and inhibiting the increase of acidity and color of the electrolyte during long-term storage. The sulfate ester additives can also form a stable passivation film on the positive and negative electrode surfaces with lithium salts, inhibiting electrolyte decomposition and dissolution of transition metal ions. The three additives work together to improve the high-temperature cycle performance and safety of batteries using the above additives. Detailed Implementation

[0017] Unless otherwise stated or in case of contradiction, the terms or phrases used herein shall have the following meanings:

[0018] In this application, the selection range of "and / or", "or / and", and "and / or" includes any one of two or more related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected using at least two conjunctions selected from "and / or", "or / and", and "and / or", it should be understood that the technical solution undoubtedly includes technical solutions connected by "logical AND", and also undoubtedly includes technical solutions connected by "logical OR". For example, "A and / or B" includes three parallel solutions: A, B, and A+B. For example, the technical solution of "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C, and D (that is, a technical solution that is connected by "logical OR"), as well as any and all combinations of A, B, C, and D, that is, combinations of any two or three of A, B, C, and D, and also combinations of all four of A, B, C, and D (that is, a technical solution that is connected by "logical AND").

[0019] In this application, the terms "multiple", "various", "multiple times", "multi-dimensional", etc., unless otherwise specified, refer to a quantity greater than or equal to 2. For example, "one or more" means one or more or more.

[0020] In this application, the terms "combinations thereof", "any combination thereof", and "any combination thereof" include all suitable combinations of any two or more of the listed items.

[0021] In this application, the term "suitable" as used in phrases such as "suitable combination," "suitable method," and "any suitable method" refers to the ability to implement the technical solution of this application, solve the technical problem of this application, and achieve the expected technical effect of this application.

[0022] In this application, terms such as "preferred," "better," "more suitable," and "ideal" are used only to describe implementation methods or embodiments with better effects, and should be understood not to constitute a limitation on the scope of protection of this application.

[0023] In this application, terms such as "further," "even further," and "particularly" are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0024] In this application, the terms "optionally," "optionally," and "optional" refer to options that are optional, meaning they can be selected from either "with" or "without." If multiple "optional" options appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" option is independent.

[0025] In this application, the terms "first aspect," "second aspect," "third aspect," and "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," and "fourth," etc., serve only a non-exhaustive enumeration purpose and should be understood not to constitute a closed limitation on quantity.

[0026] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0027] In this application, numerical intervals (i.e., numerical ranges) are involved. Unless otherwise specified, the selected numerical distributions within the aforementioned numerical intervals are considered continuous and include the two endpoints (i.e., the minimum and maximum values) of the numerical range, as well as every value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints. In this document, this is equivalent to directly listing every integer. For example, if t is an integer selected from 1 to 10, it means that t is any integer selected from the group of integers consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Furthermore, when multiple ranges are provided to describe features or characteristics, these ranges can be merged. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0028] Unless otherwise specified, the temperature parameters in this application are permitted to be either constant-temperature treatment or variations within a certain temperature range. It should be understood that the constant-temperature treatment allows temperature fluctuations within the precision range of the instrument control, such as ±5℃, ±4℃, ±3℃, ±2℃, or ±1℃.

[0029] In this application, percentage content refers to mass percentage for solid-liquid mixtures and solid-phase-solid mixtures, and volume percentage for liquid-phase-liquid mixtures, unless otherwise specified.

[0030] In this application, unless otherwise specified, percentage concentrations refer to final concentrations. The final concentration refers to the percentage of the added component in the system after its addition.

[0031] In this application, %(w / w) and wt% both represent weight percentage, %(v / v) refers to volume percentage, and %(w / v) refers to mass-volume percentage.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0033] This application provides an additive composition comprising a sulfate ester compound, a phosphazene compound, and a trimethylsilyl ester compound in a mass ratio of (0.1~5):(1~10):(1~5).

[0034] Furthermore, the additive composition includes sulfate ester compounds, phosphazene compounds, and trimethylsilyl ester compounds in a mass ratio of (1~3):(5~10):(1~3). Further, the additive composition includes sulfate ester compounds, phosphazene compounds, and trimethylsilyl ester compounds in a mass ratio of (1~2):5:(1~2). The resulting additive composition enables a more compact electrode interface film, which is beneficial for improving the high-temperature stability of the battery.

[0035] In a specific example, sulfate compounds include vinyl sulfate. 4-Methylvinyl sulfate, vinyl disulfate One or more of the following: propylene sulfate, 1,3-propanediol sulfate, pentaerythritol disulfide, diethyl sulfate, and dipropyl sulfate.

[0036] In a specific example, the chemical formula of a phosphazene compound satisfies the following equation (1-1). Or formula (1-2) ;

[0037] R1~R 11 Each is independently selected from one of halogens, substituted or unsubstituted C1-C5 alkoxy groups, and phenoxy groups.

[0038] In a specific example, the chemical formula of the phosphazene compound satisfies formula (1-1), wherein R1 to R6 are each independently one of a halogen, a C1 to C3 alkoxy group, and a phenoxy group.

[0039] In one specific example, phosphazene compounds include hexafluorocyclotriphosphazene. ethoxypentafluorocyclotriphosphazene Pentafluoro(phenoxy)cyclotriphosphazene And one or more of hexamethoxycyclotriphosphazenes.

[0040] In one specific example, trimethylsilyl compounds include one or more of bis(trimethylsilane) maleate, bis(trimethylsilyl) adipic acid, and bis(trimethylsilyl)butynediate.

[0041] The phosphazene compounds in the additives provided in this application have flame retardant properties, which greatly improve thermal stability and safety. In addition, phosphazene compounds and trimethylsilyl ester compounds can remove trace amounts of water in the electrolyte, inhibit the hydrolysis of lithium salt in the electrolyte to a certain extent, keep the lithium salt within a suitable range, thereby reducing the generation of HF, and inhibiting the increase of acidity and color of the electrolyte during long-term storage. The sulfate ester additives can also form a stable passivation film on the positive and negative electrode surfaces with lithium salt, inhibiting electrolyte decomposition and dissolution of transition metal ions. The three additives work together to improve the high-temperature cycle performance and safety of batteries using the above additives.

[0042] This application provides an electrolyte, the solvent of which includes the above-mentioned additive composition and an organic solvent in a mass ratio of (1~15):100.

[0043] The electrolyte solvent further comprises the above-mentioned additive composition and an organic solvent in a mass ratio of (3~10):100. Specifically, the mass ratio of the additive composition and the organic solvent may be, but is not limited to, 3:100, 4:100, 5:100, 6:100, 7:100, 8:100, 9:100 or 10:100.

[0044] In one specific example, the organic solvent includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl formate, ethyl formate, ethyl acetate, ethyl propionate, γ-butyrolactone, ethylene glycol dimethyl ether, and 1,3-dioxane.

[0045] In one specific example, the electrolyte also includes 0.5 mol / L to 1.5 mol / L of lithium salt. Specifically, the solute concentration of the electrolyte is 0.5 mol / L to 1.5 mol / L of lithium salt.

[0046] Furthermore, the lithium salt includes one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium perchlorate, lithium difluorooxalate borate, and lithium difluorooxalate borate.

[0047] This application also provides a lithium-ion battery, including a positive electrode, a negative electrode, a separator, and an electrolyte. The separator is disposed between the positive electrode and the negative electrode, and the positive electrode, the negative electrode, and the separator are immersed in the electrolyte, which includes the electrolyte as described above.

[0048] The phosphazene compounds in the additives provided in this application have flame retardancy, which greatly improves thermal stability and safety. In addition, the phosphazene compounds and trimethylsilyl ester compounds can remove trace water in the electrolyte, inhibit the hydrolysis of lithium salts in the electrolyte, and thus reduce the generation of HF. They can also inhibit the increase of acidity and color during long-term storage of the electrolyte. The lithium salt additives and sulfate ester additives work synergistically to form a stable passivation film on the positive and negative electrode surfaces, inhibiting electrolyte decomposition and the dissolution of transition metal ions, and improving the cycle performance, high-temperature performance and safety of batteries using the above additives.

[0049] This application also provides a lithium-ion battery, including a positive electrode, a negative electrode, a separator, and an electrolyte. The separator is disposed between the positive electrode and the negative electrode. The positive electrode, the negative electrode, and the separator are immersed in the electrolyte. The material of the negative electrode includes the electrode materials described above.

[0050] The lithium-ion battery provided in this application can effectively improve the cycle stability of the battery and significantly enhance its safety performance by using the above-mentioned electrolyte.

[0051] In this application, the specific appearance and specifications of the lithium-ion battery are not strictly limited, and various battery forms commonly used in the art can be adopted, such as pouch batteries, aluminum-cased batteries, or cylindrical batteries.

[0052] In this application, there are no particular restrictions on the active materials used for the positive and negative electrodes; conventional positive and negative electrode active materials in the art can be used. For example, positive electrode active materials may include, but are not limited to, lithium transition metal oxides, lithium iron phosphate, lithium manganese oxide, etc.; negative electrode active materials may include, but are not limited to, graphite, soft carbon, hard carbon, silicon-based materials, lithium titanate, etc.

[0053] To make the objectives, technical solutions, and advantages of this application clearer and more concise, the following specific embodiments are used for illustration, but this application is by no means limited to these embodiments. The embodiments described below are merely preferred embodiments of this application and can be used to describe this application, but should not be construed as limiting the scope of this application. It should be noted that any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

[0054] To better illustrate this application, the following description, in conjunction with specific embodiments, further explains its content. The following are specific embodiments.

[0055] Example 1

[0056] This embodiment provides an electrolyte additive composition, an electrolyte, and a lithium-ion battery.

[0057] The additive composition consists of vinyl sulfate, ethoxypentafluorocyclotriphosphazene and maleic acid bis(trimethylsilane) ester in a mass ratio of 2:5:1.

[0058] The electrolyte and its preparation method are as follows:

[0059] 1) Ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) were mixed in a mass ratio of EC:DMC:DEC = 3:5:2, and purified by molecular sieve to remove impurities and water, thus obtaining the basic solvent;

[0060] 2) Add 2 wt% vinyl sulfate, 5 wt% ethoxypentafluorocyclotriphosphazene, and 1 wt% bis(trimethylsilane) maleate to the base solvent obtained in 1), and stir until homogeneous.

[0061] 3) At room temperature, 12.5 wt% lithium hexafluorophosphate (approximately 1 mol / L) based on the total mass of the above organic solvent and additive composition was added to 2) above to obtain a basic electrolyte system with added additives.

[0062] The electrolyte obtained in this embodiment was used in lithium iron phosphate / graphite soft-pack batteries to test their cycle stability at high temperature (45°C), and the safety of the battery was tested by furnace temperature pass rate.

[0063] The preparation of the lithium iron phosphate positive electrode sheet involves mixing lithium iron phosphate, conductive agent Super P, binder PVDF, and carbon nanotubes (CNT) at a mass ratio of 97.5:0.5:1:1 to form a lithium-ion battery positive electrode slurry of a certain viscosity. This slurry is coated onto an aluminum foil current collector, dried at high temperature, and then cold-pressed. The slitting and slicing process is followed by vacuum drying. The preparation of the graphite negative electrode sheet involves mixing artificial graphite with conductive agent Super P, thickener CMC, and binder SBR (styrene-butadiene rubber emulsion) at a mass ratio of 95:1.5:1.0:2.5 to form a slurry. This slurry is coated onto both sides of a copper foil, dried, and rolled to obtain the negative electrode sheet. The negative electrode sheet is then dried in a vacuum at 85°C for 4 hours to produce a qualified lithium-ion battery negative electrode sheet. The lithium-ion battery is then manufactured by stacking or winding the positive and negative electrode sheets prepared according to the above process. After vacuum drying, the electrolyte is injected to complete the battery fabrication.

[0064] The test conditions for a 45℃ high-temperature environment are as follows: 2.5~3.65V, 1C rate charge and discharge cycle performance.

[0065] At 45℃, discharge at a standard 1C constant current until the discharge termination voltage is 2.5V, and let it rest for 30 minutes; then charge at a standard 1C constant current and constant voltage until the charging limit voltage is 3.65V, the cutoff current is 0.05C, and let it rest for 30 minutes; discharge at a standard 1C constant current until the discharge termination voltage is 2.5V, and let it rest for 30 minutes; repeat the above full charge and discharge steps until the capacity decays to 80% of the initial capacity. The number of repeats is the cycle number, which is used to evaluate the cycle performance of the battery in a high-temperature environment.

[0066] The safety test conditions are as follows: the battery safety performance was tested at a furnace temperature of 130℃ for 30 minutes after being fully charged.

[0067] After the battery is fully charged (charged at 0.5C standard constant current and constant voltage to the charging limit voltage of 3.65V, cut-off current of 0.05C), the battery is placed in a forced-air drying oven and heated from room temperature to (130±2)℃ at a rate of (5±2)℃ / min. The temperature is then maintained at this temperature for 30 minutes. If the battery does not catch fire, explode, or leak after 30 minutes, the test is considered passed. 100 samples are tested, and each sample is observed to see if it passes the test.

[0068] Example 2

[0069] Compared with Example 1, the difference in Example 2 is that the sulfate ester compound added to the basic electrolyte prepared in step (2) is ethylene disulfate, and its amount is 2% of the total mass of the basic solvent.

[0070] Example 3

[0071] Compared with Example 1, the difference in Example 2 is that the pentafluoro(phenoxy)cyclotriphosphazene added to the basic electrolyte prepared in step (2) is used in an amount of 5% of the mass of the basic solvent.

[0072] Example 4

[0073] Compared with Example 1, the difference in Example 4 is that the trimethylsilyl ester compound added to the basic electrolyte prepared in step (2) is bis(trimethylsilyl)butynediate, and its amount is 1% of the total mass of the solvent.

[0074] Comparative Example 1

[0075] Compared with Example 1, the difference between this comparative example and Example 1 is that the basic electrolyte prepared in step (2) does not contain the electrolyte additive combination described in this application.

[0076] Comparative Example 2

[0077] Compared with Example 1, the difference between this comparative example and Example 1 is that the basic electrolyte prepared in step (2) contains ethylene sulfate additive, which is 2% of the total mass of the solvent, and ethoxypentafluorocyclotriphosphazene additive, which is 5% of the total mass of the solvent.

[0078] Comparative Example 3

[0079] Compared with Example 1, the difference between this comparative example and Example 1 is that the ethoxypentafluorocyclotriphosphazene additive used in the basic electrolyte prepared in step (2) is 5% of the total mass of the solvent, and the maleic acid bis(trimethylsilane) additive is 1% of the total mass of the solvent.

[0080] Comparative Example 4

[0081] Compared with Example 1, the difference of Comparative Example 1 is that the amount of maleic acid bis(trimethylsilane) additive in the basic electrolyte prepared in step (2) is 1% of the total mass of the solvent, and the amount of vinyl sulfate additive is 2% of the total mass of the solvent.

[0082] Table 1 shows the comparison results of high-temperature cycling tests of lithium-ion batteries in each embodiment and comparative example.

[0083] Table 1

[0084] Solvent composition of electrolyte Capacity retention rate after 800 cycles (%) Furnace temperature test pass rate (%) Example 1 Base solvent + 2 wt% vinyl sulfate + 5% ethoxypentafluorocyclotriphosphazene + 1% bis(trimethylsilane) maleate 88.61 100 Example 2 Base solvent + 2 wt% vinyl disulfate + 5% ethoxypentafluorocyclotriphosphazene + 1% bis(trimethylsilane) maleate 88.65 100 Example 3 Base solvent + 2 wt% vinyl sulfate + 5% pentafluoro(phenoxy)cyclotriphosphazene + 1% bis(trimethylsilane) maleate 88.61 100 Example 4 Base solvent + 2 wt% vinyl sulfate + 5% pentafluoro(phenoxy)cyclotriphosphazene + 1% bis(trimethylsilyl)butynediate 88.97 100 Comparative Example 1 Basic solvent 86.54 60 Comparative Example 2 Base solvent + 2 wt% vinyl sulfate + 5% ethoxypentafluorocyclotriphosphazene 87.39 90 Comparative Example 3 Base solvent + 5% ethoxypentafluorocyclotriphosphazene + 1% bis(trimethylsilane) maleate 87.48 95 Comparative Example 4 Base solvent + 2 wt% vinyl sulfate + 1% bis(trimethylsilane) maleate 87.56 80

[0085] As shown in Table 1, compared with electrolytes without additives or with only one additive, the combination of three additives—sulfate compounds, phosphazene compounds, and trimethylsilyl ester compounds—in this application improves the high-temperature cycle performance of the battery. Lithium-ion secondary batteries made using the electrolyte containing this additive combination can operate stably at high voltages above 4.5V, significantly improving the battery's specific capacity and energy density. Comparing the battery safety test results in Table 1, it can be seen that the safety of the electrolyte with added phosphazene compounds is significantly improved compared to the basic electrolyte and the electrolyte without added phosphazene compounds. The combination of three additives—sulfate compounds, phosphazene compounds, and trimethylsilyl ester compounds—in this application exhibits the best safety performance, confirming the synergistic effect of the three additives. The phosphazene compound in the additive composition of this application has flame retardant properties. The electrolyte containing this additive composition has good thermal stability and flame retardancy, and cannot be ignited by open flame, greatly improving battery safety. In addition, the phosphazene compound and trimethylsilyl ester compound can remove trace water in the electrolyte, inhibit the hydrolysis of electrolyte lithium salts such as LiPF6, reduce HF generation, and thus inhibit the increase in acidity and color of the electrolyte during long-term storage (especially for electrolytes containing vinyl sulfate, inhibiting discoloration of vinyl sulfate and increase in electrolyte acidity and color). At the same time, the lithium salt and sulfate ester additives work synergistically to form a stable passivation film on the positive and negative electrode surfaces, inhibiting electrolyte decomposition and dissolution of transition metal ions, improving battery cycle performance, high-temperature performance, and safety.

[0086] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0087] The embodiments described above merely illustrate several implementation methods of this application to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. An additive composition, characterized in that, This includes sulfate esters, phosphazene compounds, and trimethylsilyl esters in a mass ratio of (0.1~5): (1~10): (1~5).

2. The additive composition according to claim 1, characterized in that, The sulfate ester compounds include one or more of vinyl sulfate, 4-methyl vinyl sulfate, divinyl sulfate, propylene sulfate, 1,3-propanediol cyclic sulfate, pentaerythritol bicyclic sulfate, diethyl sulfate, and dipropyl sulfate.

3. The additive composition according to claim 1, characterized in that, The chemical formula of the phosphazene compounds satisfies the following equation (1-1). Or formula (1-2) ; R1~R 11 Each is independently selected from one of halogens, substituted or unsubstituted C1-C5 alkoxy groups, and phenoxy groups.

4. The additive composition according to claim 3, characterized in that, The chemical formula of the phosphazene compound satisfies formula (1-1), wherein R1 to R6 are each independently one of halogen, C1 to C3 alkoxy group and phenoxy group.

5. The additive composition according to claim 3 or 4, characterized in that, The phosphazene compounds include one or more of hexafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, pentafluoro(phenoxy)cyclotriphosphazene, and hexamethoxycyclotriphosphazene.

6. The additive composition according to any one of claims 1 to 4, characterized in that, The trimethylsilyl ester compounds include one or more of bis(trimethylsilane) maleate, bis(trimethylsilyl) adipic acid, and bis(trimethylsilyl)butynediate.

7. An electrolyte, characterized in that, The solvent of the electrolyte comprises the additive composition as described in any one of claims 1 to 6 and an organic solvent in a mass ratio of (1 to 15):

100.

8. The electrolyte as described in claim 7, characterized in that, The organic solvent includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl formate, ethyl formate, ethyl acetate, ethyl propionate, γ-butyrolactone, ethylene glycol dimethyl ether, and 1,3-dioxane.

9. The electrolyte as described in claim 7 or 8, characterized in that, The electrolyte also includes lithium salts with a concentration of 0.5 mol / L to 1.5 mol / L.

10. A lithium-ion battery, characterized in that, The device includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the separator is disposed between the positive electrode and the negative electrode, and the positive electrode, the negative electrode, and the separator are immersed in the electrolyte, wherein the electrolyte includes the electrolyte as described in any one of claims 7 to 9.

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