Electrolyte additive for resisting high voltage and application thereof

Abstract

The invention belongs to the technical field of electrolyte additives, and discloses a high-voltage-resistant electrolyte additive and application thereof.The high-voltage-resistant electrolyte additive is prepared by mixing a cyclic sulfate compound and a fluorinated organic solvent to obtain a mixed solution; adding a fluorinating reagent containing sulfonyl groups into the mixed solution under a low-temperature condition for reaction to obtain an intermediate reaction solution, quenching the intermediate reaction solution, carrying out counter-current extraction on the quenched intermediate reaction solution for several times by using a low-boiling-point alkane solvent, combining organic phases obtained by the counter-current extraction for several times, and carrying out reduced pressure distillation on the combined organic phases; obtaining a crude product based on the combined organic phase, and obtaining the high-voltage-resistant electrolyte additive based on the crude product; the working voltage window of the electrolyte can be greatly improved, the high-temperature cycle performance and safety of the battery are improved, the electrolyte is particularly suitable for a high-voltage positive electrode material system, and key material support is provided for developing a high-energy-density lithium battery.

Description

Technical Field

[0001] This invention relates to the field of electrolyte additives, and more specifically to an electrolyte additive for high voltage resistance and its application. Background Technology

[0002] Supercapacitors are a new type of high-performance energy storage device, falling between traditional capacitors and batteries. Their core advantages lie in their extremely high power density, enabling rapid charging and discharging within seconds, and a cycle life of hundreds of thousands of cycles, far exceeding that of batteries. They store energy through electrostatic adsorption on the electrode surface (double-layer principle) or rapid redox reactions (pseudocapacitance). No chemical reactions occur during charging and discharging, resulting in high efficiency, low heat generation, and good safety. They are primarily used in scenarios requiring instantaneous high power, such as energy recovery in electric vehicles, braking energy storage in rail transit, power compensation in smart grids, and backup power for consumer electronics, overcoming the shortcomings of insufficient battery power and low energy density of traditional capacitors.

[0003] In recent years, high-voltage supercapacitor technology has received widespread attention as a key path to improve the energy density of electrochemical energy storage devices.

[0004] However, traditional supercapacitors are limited by the narrow electrochemical stability window (often below 2.7V) of aqueous or conventional organic electrolytes, resulting in generally low single-cell operating voltages, typically in the range of 2.5V to 2.7V. This low voltage bottleneck directly leads to generally low energy densities (usually <10 Wh / kg), severely limiting their application in critical scenarios such as single-charge range, device miniaturization, and long-term backup power. This forces many systems to adopt complex multi-device series schemes, increasing system cost, size, and reducing overall reliability. Since energy density is proportional to the square of voltage, the low voltage bottleneck becomes a core factor restricting energy density improvement, making it difficult to meet the high-energy storage requirements of high-end applications such as electric vehicles and smart grids.

[0005] Therefore, the industry urgently needs a new material that can solve the problem of not being able to work stably under high voltage. Summary of the Invention

[0006] The purpose of this invention is to provide an electrolyte additive for high-voltage resistance and its application, in order to overcome the problems existing in the prior art. This invention can significantly improve the working voltage window of the electrolyte, improve the high-temperature cycle performance and safety of the battery, and is especially suitable for high-voltage cathode material systems, providing key material support for the development of high-energy-density lithium batteries.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a method for preparing a high-voltage resistant electrolyte additive, comprising the following steps: Step 1: Mix the cyclic sulfate ester compound with a fluorinated organic solvent to obtain a mixed solution. Add a fluorinating agent containing a sulfonyl group to the mixed solution under low temperature conditions to react and obtain an intermediate reaction solution. Step 2: Quench the intermediate reaction solution, and use a low-boiling-point alkane solvent to perform several countercurrent extractions on the quenched intermediate reaction solution, and combine the organic phases from the several countercurrent extractions. Step 3: The combined organic phases are successively subjected to acid washing, alkali washing and water washing until neutral, then molecular sieves are added for preliminary dehydration, and then vacuum distillation is performed to obtain crude product; Step 4: Dissolve the crude product in a crystallization solvent to form a supersaturated solution. Aging the supersaturated solution yields precipitated crystals. Drying the precipitated crystals yields a high-voltage electrolyte additive.

[0008] In some embodiments, the cyclic sulfate compounds include one of ethylene carbonate, vinylene carbonate, and fluoroethylene carbonate; The fluorinated organic solvent includes one or two of fluorinated ethers and fluorinated esters; The fluorinating agent containing a sulfonyl group includes one of fluorosulfonic anhydride and N-fluorobisbenzenesulfonyl imide.

[0009] In some embodiments, the molar ratio of the cyclic sulfate compound to the fluorinated organic solvent is 1:(1 to 1.5). The mass ratio of the cyclic sulfate compound to the fluorinating agent containing a sulfonyl group is 1:(3-10).

[0010] In some embodiments, the low temperature condition is -10°C to 10°C; The reaction temperature is 0℃~25℃, and the reaction time is 2-8 h.

[0011] In some embodiments, quenching the intermediate reaction solution specifically includes: The intermediate reaction solution was transferred to an ice-water mixture below 0°C for quenching; The countercurrent extraction is performed 3 to 5 times.

[0012] In some embodiments, the low-boiling-point alkane solvent includes one or both of n-hexane and cyclohexane.

[0013] In some embodiments, the pickling is performed using dilute hydrochloric acid or dilute sulfuric acid with a concentration of 0.1-0.5 mol / L; The alkaline washing uses a sodium bicarbonate or sodium carbonate solution with a concentration of 0.1-0.5 mol / L; The molecular sieve has a density of 3–4 Å. The vacuum distillation temperature is 25–35°C, the vacuum distillation pressure is 1–3 kPa, and the vacuum distillation time is 2–4 h.

[0014] In some embodiments, the crystallization solvent includes one of diethyl ether and methyl tert-butyl ether; The temperature of the crystallization solvent is -20℃ to -40℃; The aging temperature is -5℃ to 5℃, and the aging time is 2 to 6 hours; The drying process involves a vacuum degree of 80–100 Pa, a drying temperature of 30–40°C, and a drying time of 4–12 hours.

[0015] Secondly, the present invention provides an electrolyte additive for high voltage resistance, which is obtained based on the preparation method of the electrolyte additive for high voltage resistance described above.

[0016] Thirdly, the present invention provides an application of electrolyte additives for high voltage resistance in supercapacitors.

[0017] The above technical solution has the following advantages or beneficial effects: Firstly, this invention provides a method for preparing a high-voltage resistant electrolyte additive. The high-voltage resistant electrolyte additive prepared by this method significantly enhances the electrochemical stability and high-voltage tolerance of its molecular structure through the precise reaction of cyclic sulfate esters with fluorinated reagents. The introduced sulfonyl and fluorinated groups synergistically improve the additive's antioxidant properties, effectively suppressing electrolyte decomposition and electrode interface side reactions under high voltage. The use of countercurrent extraction and multi-step purification processes results in high product purity and low impurity residue, which helps to form a stable and dense SEI / CEI film in lithium-ion batteries. The obtained additive can significantly increase the working voltage window of the electrolyte, improve the high-temperature cycle performance and safety of the battery, and is particularly suitable for high-voltage cathode material systems, providing key material support for the development of high-energy-density lithium batteries.

[0018] In some embodiments, cyclic sulfates, preferably ethylene carbonate or other common compounds with specific cyclic structures, are used to ensure both good reactivity and electrochemical functionality of subsequent derivatives. Fluorinated organic solvents, such as ethers or esters, are selected to ensure complete dissolution of the reactants and maintain suitable reaction conditions at low temperatures. The fluorinating agent is specifically a sulfonyl group, which is the necessary reaction center for introducing key fluorinated functional groups and constructing a high-pressure stable structure of the target molecule. The selection of these specific substances makes the preparation process more operable and reproducible, providing a clear material basis for the high purity and expected high-pressure performance of the final additive.

[0019] In some embodiments, this ratio limit optimizes the reaction process and yield by precisely controlling the ratio between reactants; the molar ratio of cyclic sulfate to solvent is set to 1:(1-1.5) to ensure that the reactants reach a suitable concentration in the fluorinated solvent, ensuring sufficient contact reaction while avoiding difficulties in subsequent separation and purification due to excessive solvent; the cyclic sulfate and fluorinating agent are added in a specific ratio of 1 mol:(3-10) g, which is sufficient to drive the complete introduction of fluorination and sulfonyl groups into the reaction, while effectively controlling costs and potential side reactions; this optimized material ratio is the key to achieving efficient and selective synthesis of intermediates, providing a guarantee for subsequent purification and obtaining high purity and consistency of the final product, thereby ensuring the stable and reliable performance of the additive.

[0020] In some embodiments, precise control of the reaction temperature and time is crucial to the selectivity, purity, and final performance of the product. Limiting the initial mixing and reaction process to a low temperature range (-10°C to 25°C) effectively suppresses side reactions such as ring-opening of cyclic sulfates and decomposition of fluorinating agents, ensuring that the sulfonyl fluorination reaction proceeds efficiently and specifically. Setting the reaction time to 2-8 hours provides sufficient kinetic conditions for this specific reaction, ensuring complete reaction while avoiding product degradation or other cascade reactions due to excessive time. These mild and controlled process conditions are key to achieving high-yield and highly selective synthesis of the target intermediate, laying a reliable foundation for ultimately obtaining a structurally well-defined and stable high-voltage electrolyte additive.

[0021] In some embodiments, the quenching and extraction process is designed to safely and efficiently separate and purify heat-sensitive intermediates. Quenching in ice water below 0°C rapidly terminates the reaction of highly reactive fluorinating agents, preventing over-reaction or product hydrolysis and ensuring operational safety. The use of 3–5 countercurrent extractions fully utilizes the selectivity of low-boiling-point alkane solvents, efficiently extracting the target intermediate from the complex aqueous reaction mixture through multi-stage, counter-current liquid-liquid contact, while also providing good separation of polar impurities and unreacted raw materials. This combined process significantly improves the recovery rate and purity of intermediates, reduces product loss, and lightens the burden on subsequent purification steps, making it a key operational step in ensuring high yield and high quality of the final additive product.

[0022] In some embodiments, this feature further optimizes the type of solvent used for countercurrent extraction. Both n-hexane and cyclohexane are typical low-boiling-point alkanes with good chemical inertness, and will not undergo side reactions with heat-sensitive fluorinated intermediates. At the same time, they have good selective solubility for the target intermediate, while having very low solubility for impurities such as polar byproducts, residual catalysts, or inorganic salts that may be present in the reaction. Their low-boiling-point characteristics facilitate separation and recovery from the product in subsequent vacuum distillation, reducing purification energy consumption and residual solvent risks. Using these two solvents for countercurrent extraction can achieve efficient and gentle separation and enrichment of intermediates, providing a reliable guarantee for obtaining high-purity crude products, and is an important part of the entire purification process.

[0023] In some embodiments, these process parameters provide precise operating standards for the deep purification of the crude product. Sequential washing with dilute acid and dilute alkali solutions effectively neutralizes and removes trace amounts of alkaline or acidic impurities and catalyst residues remaining in the organic phase after extraction. Using a 3–4 Å molecular sieve selectively adsorbs trace amounts of water and small-molecule alcohol impurities in the organic phase, achieving preliminary deep dehydration. Vacuum distillation is carried out under strict low-temperature (25–35°C) and low-vacuum (1–3 kPa) conditions for 2–4 hours, aiming to gently remove low-boiling-point alkane solvents and other volatile impurities while avoiding the decomposition or polymerization of heat-sensitive target products due to high temperatures. These steps work synergistically to significantly improve the purity of the crude product, laying a solid foundation for subsequent crystallization to obtain high-purity crystalline products.

[0024] In some embodiments, the precise setting of crystallization and drying conditions is crucial for obtaining a high-purity, high-crystallinity final product. Choosing diethyl ether or methyl tert-butyl ether as the crystallization solvent provides good solubility and temperature sensitivity for the target additive, facilitating the formation of a supersaturated solution. Preparing the solution at a low temperature of -20°C to -40°C and aging it at -5°C to 5°C for 2-6 hours allows for slow and orderly nucleation and growth of crystals, effectively eliminating co-soluble impurities and significantly improving product purity. Subsequent drying under mild vacuum conditions of 30-40°C and 80-100 Pa for 4-12 hours thoroughly removes trace amounts of solvent remaining on the crystal surface and in the crystal lattice, preventing solvent molecules from affecting the electrochemical performance of the additive in the electrolyte, ultimately ensuring excellent product stability and batch consistency.

[0025] Secondly, this invention provides an electrolyte additive for high-voltage resistance. Key functional groups such as sulfonyl and fluorine atoms are successfully introduced into its molecular structure, giving the product excellent oxidation stability and high-voltage tolerance. Thanks to the strictly controlled synthesis and purification process, the additive has high purity, low impurities and excellent crystal morphology, which can effectively inhibit electrolyte decomposition under high voltage and promote the formation of a stable interface film, thereby significantly improving the working voltage and cycle life of lithium batteries.

[0026] Thirdly, this invention provides an application of a high-voltage resistant electrolyte additive in supercapacitors. This high-voltage resistant electrolyte additive can be used in supercapacitors, and its excellent high-voltage resistance and oxidation resistance help to broaden the working voltage window of the electrolyte, thereby significantly improving the energy density of the device. At the same time, it can effectively suppress the decomposition side reactions at the electrode / electrolyte interface at high potentials, enhance cycle stability and high-temperature reliability, and provide key material support for the development of higher-performance supercapacitors. Attached Figure Description

[0027] Figure 1 This is a schematic flowchart illustrating a method for preparing high-voltage resistant electrolyte additives according to some embodiments of this specification. Detailed Implementation

[0028] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0029] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] The purpose of this invention is to provide an electrolyte additive for high-voltage resistance and its application, in order to overcome the problems existing in the prior art. This invention can significantly improve the working voltage window of the electrolyte, improve the high-temperature cycle performance and safety of the battery, and is especially suitable for high-voltage cathode material systems, providing key material support for the development of high-energy-density lithium batteries.

[0032] Example 1: This embodiment provides a method for preparing a high-voltage resistant electrolyte additive, including the following steps: Step 1: Mix 1 mol of ethylene carbonate with 1 mol of fluoroether to obtain a mixed solution. Add 3 g of fluorosulfonic anhydride to the mixed solution at a low temperature of -10℃ and react at 0℃ for 2 h to obtain an intermediate reaction solution. Step 2: Transfer the intermediate reaction solution to an ice-water mixture below 0°C for quenching. Perform three countercurrent extractions of the quenched intermediate reaction solution using n-hexane. Combine the organic phases from the three countercurrent extractions. Step 3: The combined organic phases were acid-washed with 0.1 mol / L dilute hydrochloric acid, alkaline-washed with 0.1 mol / L sodium bicarbonate, and then washed with water until neutral. Then, a molecular sieve with a pore size of 3 Å was added for preliminary dehydration, and then vacuum distilled at 25℃ and 1 kPa for 2 h to obtain the crude product. Step 4: Dissolve the crude product in diethyl ether at -20℃ to form a supersaturated solution. Aging the supersaturated solution at -5℃ for 2 h yields precipitated crystals. Dry the precipitated crystals at 80 Pa and 30℃ for 4 h to obtain a high-voltage electrolyte additive.

[0033] This embodiment also provides an application of a high-voltage resistant electrolyte additive in a supercapacitor, applying the high-voltage resistant electrolyte additive prepared in Example 1 to a supercapacitor. Specifically, 1.0 wt% of the additive was added to a 1.0 M tetraethylammonium tetrafluoroborate (TEABF4) / acetonitrile (AN) electrolyte as the working electrolyte, and a symmetrical activated carbon electrode supercapacitor was assembled and tested. The results showed that using the electrolyte containing the additive successfully increased the rated operating voltage of the device from 2.7 V to 3.0 V. Within the 3.0 V voltage window, at 1 A g… -1 Constant current charge-discharge cycle tests were conducted at a current density that significantly outperformed devices using the basic electrolyte (retention rate after cycling was approximately 82%). Simultaneously, the additives effectively suppressed gas evolution and electrolyte decomposition under high voltage, significantly improving the high-voltage cycle stability and lifespan of the supercapacitor.

[0034] Example 2: This embodiment provides a method for preparing a high-voltage resistant electrolyte additive, including the following steps: Step 1: Mix 1 mol of vinylene carbonate with 1.2 mol of fluoroester to obtain a mixed solution. Add 6 g of fluorosulfonic anhydride to the mixed solution at a low temperature of 0°C and react at 15°C for 5 h to obtain an intermediate reaction solution. Step 2: Transfer the intermediate reaction solution to an ice-water mixture below 0°C for quenching. Perform four countercurrent extractions of the quenched intermediate reaction solution with n-hexane. Combine the organic phases from the four countercurrent extractions. Step 3: The combined organic phases were acid-washed with 0.3 mol / L dilute hydrochloric acid, alkaline-washed with 0.3 mol / L sodium bicarbonate, and then washed with water until neutral. Molecular sieves with a pore size of 4 Å were added for preliminary dehydration, and then vacuum distilled at 30℃ and 2 kPa for 3 h to obtain the crude product. Step 4: Dissolve the crude product in diethyl ether at -30℃ to form a supersaturated solution. Aging the supersaturated solution at 0℃ for 4 h yields precipitated crystals. Dry the precipitated crystals at 90 Pa and 35℃ for 8 h to obtain a high-voltage electrolyte additive.

[0035] This embodiment also provides an application of a high-voltage electrolyte additive in a supercapacitor. The high-voltage electrolyte additive prepared in Example 2 is applied to a supercapacitor. Specifically, 1.5 wt% of the additive is added to a 1.5 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) / propylene carbonate (PC) electrolyte as the working electrolyte for the supercapacitor. A button-type supercapacitor based on an activated carbon electrode is then assembled and tested. Results show that the addition of the additive significantly increases the oxidation potential of the electrolyte, and the stable operating voltage window of the device widens from 2.8 V to 3.2 V. At 3.2 V, with a voltage of 5 A g... -1 High current density constant current charge-discharge cycle testing showed that the device maintained a capacity retention of 93%, and the energy density was improved by approximately 20% compared to devices using the base electrolyte. Simultaneously, the additive promoted the formation of a more stable interfacial film on the positive electrode surface, effectively reducing leakage current and improving the device's long-term cycling stability at high temperatures (60°C).

[0036] Example 3: This embodiment provides a method for preparing a high-voltage resistant electrolyte additive, including the following steps: Step 1: Mix 1 mol of fluoroethylene carbonate with a mixture of 1.5 mol of fluoroether and fluoroester to obtain a mixed solution. Add 10 g of N-fluorobisbenzenesulfonamide to the mixed solution at a low temperature of 10℃ and react at 25℃ for 8 h to obtain an intermediate reaction solution. Step 2: Transfer the intermediate reaction solution to an ice-water mixture below 0°C for quenching. Perform five countercurrent extractions of the quenched intermediate reaction solution using cyclohexane. Combine the organic phases from the five countercurrent extractions. Step 3: The combined organic phases were acid-washed with 0.5 mol / L dilute sulfuric acid, then with 0.5 mol / L sodium carbonate solution, and then washed with water until neutral. Molecular sieves with a pore size of 4 Å were added for preliminary dehydration, and then vacuum distilled at 35℃ and 3 kPa for 4 h to obtain the crude product. Step 4: Dissolve the crude product in methyl tert-butyl ether at -40℃ to form a supersaturated solution. Aging the supersaturated solution at 5℃ for 6 h yields precipitated crystals. Dry the precipitated crystals at 100 Pa and 40℃ for 12 h to obtain a high-voltage electrolyte additive.

[0037] This embodiment also provides an application of a high-voltage electrolyte additive in a supercapacitor. The high-voltage electrolyte additive prepared in Example 3 is applied to a supercapacitor. Specifically, 2.0 wt% of the additive is added to the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) as the working electrolyte for the high-voltage supercapacitor. This is then used in a supercapacitor with activated carbon / graphene hybrid electrodes. Test results show that, thanks to the additive's excellent high-voltage stability and interface modulation capabilities, the stable operating voltage window of the device is significantly broadened to 3.5 V. At a high voltage of 3.5 V, with a flow rate of 10 A g... - ¹ Cyclic testing at ultra-high rates showed a capacity retention of 97%. Furthermore, the system exhibited excellent electrochemical stability across a wide temperature range of -20°C to 80°C, significantly improving the energy density, power density, and environmental adaptability of the supercapacitor.

[0038] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the scope of the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0039] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing an electrolyte additive for high voltage resistance, characterized in that, Includes the following steps: A cyclic sulfate ester compound is mixed with a fluorinated organic solvent to obtain a mixed solution. A fluorinating agent containing a sulfonyl group is added to the mixed solution under low temperature conditions to carry out the reaction and obtain an intermediate reaction solution. The intermediate reaction solution was quenched, and the quenched intermediate reaction solution was subjected to several countercurrent extractions using a low-boiling-point alkane solvent. The organic phases from the several countercurrent extractions were then combined. The combined organic phases were successively subjected to acid washing, alkali washing and water washing until neutral, then molecular sieves were added for preliminary dehydration, and then vacuum distillation was carried out to obtain crude product. The crude product is dissolved in a crystallization solvent to form a supersaturated solution. The supersaturated solution is aged to obtain precipitated crystals. The precipitated crystals are then dried to obtain a high-voltage electrolyte additive.

2. The method for preparing a high-voltage resistant electrolyte additive according to claim 1, characterized in that, The cyclic sulfate compounds include one of ethylene carbonate, vinylene carbonate, and fluoroethylene carbonate. The fluorinated organic solvent includes one or two of fluorinated ethers and fluorinated esters; The fluorinating agent containing a sulfonyl group includes one of fluorosulfonic anhydride and N-fluorobisbenzenesulfonyl imide.

3. The method for preparing a high-voltage resistant electrolyte additive according to claim 1, characterized in that, The molar ratio of the cyclic sulfate compound to the fluorinated organic solvent is 1:(1 to 1.5). The ratio of the cyclic sulfate compound to the fluorinating agent containing a sulfonyl group is 1 mol: (3-10) g.

4. The method for preparing a high-voltage resistant electrolyte additive according to claim 1, characterized in that, The low temperature conditions are -10℃ to 10℃; The reaction temperature is 0℃~25℃, and the reaction time is 2-8 h.

5. The method for preparing a high-voltage resistant electrolyte additive according to claim 1, characterized in that, The quenching of the intermediate reaction solution specifically includes: The intermediate reaction solution was transferred to an ice-water mixture below 0°C for quenching; The countercurrent extraction is performed 3 to 5 times.

6. The method for preparing a high-voltage resistant electrolyte additive according to claim 1, characterized in that, The low-boiling-point alkane solvent includes one or both of n-hexane and cyclohexane.

7. A method for preparing a high-voltage resistant electrolyte additive according to claim 1, characterized in that, The pickling process uses dilute hydrochloric acid or dilute sulfuric acid with a concentration of 0.1-0.5 mol / L. The alkaline washing uses a sodium bicarbonate or sodium carbonate solution with a concentration of 0.1-0.5 mol / L; The molecular sieve has a density of 3–4 Å. The vacuum distillation temperature is 25–35°C, the vacuum distillation pressure is 1–3 kPa, and the vacuum distillation time is 2–4 h.

8. The method for preparing a high-voltage resistant electrolyte additive according to claim 1, characterized in that, The crystallization solvent includes one of diethyl ether and methyl tert-butyl ether; The temperature of the crystallization solvent is -20℃ to -40℃; The aging temperature is -5℃ to 5℃, and the aging time is 2 to 6 hours; The drying process involves a vacuum degree of 80–100 Pa, a drying temperature of 30–40°C, and a drying time of 4–12 h.

9. An electrolyte additive for high-voltage resistance, characterized in that, This is obtained based on the preparation method of a high-voltage resistant electrolyte additive according to any one of claims 1-8.

10. An application of the electrolyte additive for high voltage resistance as described in claim 9 in a supercapacitor.

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