Method for preparing an electrolyte additive and electrolyte additive

Abstract

The present application relates to the technical field of lithium ion batteries, and particularly relates to a preparation method of an electrolyte additive and the electrolyte additive. The preparation method provided by the present application comprises the following steps: providing a cyano-containing halogenated alkane and sodium hydrosulfide; performing a nucleophilic substitution reaction on the cyano-containing halogenated alkane and the sodium hydrosulfide to obtain a cyano-containing mercapto compound; providing a mercapto-functionalized reagent; reacting the cyano-containing mercapto compound with the mercapto-functionalized reagent to obtain an intermediate containing a sulfide bond; performing an oxidation reaction on the intermediate containing the sulfide bond and an oxidizing agent, so that the sulfide bond is converted into a sulfonyl group, and a sulfonyl intermediate is obtained; and selecting a type of the mercapto-functionalized reagent to obtain an electrolyte additive. Based on the above scheme, the problem that an existing electrolyte additive is difficult to balance high-pressure stability and high-rate performance is solved.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a method for preparing an electrolyte additive and the electrolyte additive itself. Background Technology

[0002] The development of lithium-ion batteries towards higher voltage, higher energy density, and higher rate capability has become a trend. However, under these extreme conditions, traditional electrolytes are prone to oxidative decomposition and transition metal dissolution on the positive electrode side, while the negative electrode side faces a significant ion desolvation energy barrier and the risk of lithium plating, severely limiting battery life and safety. Therefore, developing an electrolyte additive capable of simultaneously constructing a stable, low-impedance, and high-voltage-tolerant interfacial protective layer on both the positive and negative electrodes has become a research hotspot in this field.

[0003] In existing technologies, electrolyte additives are typically bifunctional additives. These additives can only form a homogeneous structure during film formation, where density and ion conductivity are mutually constrained and cannot be optimized simultaneously. If the film is too dense, while it enhances high-voltage oxidation resistance, it significantly blocks lithium-ion transport channels, leading to a sharp increase in interfacial impedance and deteriorating rate performance. Conversely, if the film is too sparse, although it facilitates ion conduction, the loose structure is unable to withstand continuous oxidative erosion by the electrolyte under high voltage, making the film prone to rupture and failure. This contradiction makes it difficult for existing additives to achieve a balance between performance under extreme conditions of high voltage and high rate. Summary of the Invention

[0004] To address the problem that existing additives cannot simultaneously achieve high-pressure stability and high-rate performance, this invention provides a method for preparing an electrolyte additive and the electrolyte additive itself.

[0005] This invention provides a method for preparing an electrolyte additive, comprising the following steps: providing a cyano-containing haloalkane and sodium hydrosulfide; performing a nucleophilic substitution reaction between the cyano-containing haloalkane and sodium hydrosulfide to obtain a cyano-containing thiol compound; providing a thiol functionalizing reagent; reacting the cyano-containing thiol compound with the thiol functionalizing reagent to obtain an intermediate containing a thioether bond; subjecting the intermediate containing the thioether bond to an oxidizing agent to an oxidation reaction, converting the thioether bond to a sulfonyl group to obtain a sulfonyl intermediate; selecting the type of thiol functionalizing reagent; if the thiol functionalizing reagent is trifluoroethyl iodide... Alternatively, trifluoromethyl iodide, trifluoroethyl iodide, or the trifluoromethyl group in trifluoromethyl iodide may be introduced via a nucleophilic substitution reaction, followed by oxidation to obtain a sulfonyl intermediate. The sulfonyl intermediate is an electrolyte additive comprising cyano, sulfonyl, and trifluoromethyl functional groups. Alternatively, if the thiol functionalizing agent is 2-chloroethanesulfonyl chloride, the sulfonyl chloride group of 2-chloroethanesulfonyl chloride may be introduced into the sulfonyl intermediate via a sulfonylation reaction to provide a fluorinating agent. The sulfonyl intermediate and the fluorinating agent react to obtain a fluorinated product, wherein the chlorine atom is replaced by a fluorine atom to obtain a sulfonyl fluoride group. The fluorinated product is an electrolyte additive comprising cyano, sulfonyl, and sulfonyl fluoride functional groups.

[0006] Preferably, after providing the thiol-functionalized reagent, the process specifically includes: providing a sulfonating solvent, an organic solvent, and an acid-binding agent; mixing the sulfonating solvent, organic solvent, and acid-binding agent to obtain the thiol-functionalized reagent; if the thiol-functionalized reagent is trifluoroethyl iodide or trifluoromethyl iodide, mixing the trifluoroethyl iodide or trifluoromethyl iodide, a cyano-containing thiol compound, an organic solvent, and an acid-binding agent to perform a nucleophilic substitution reaction, wherein the cyano-containing thiol compound contains a thiol group, and the trifluoroethyl iodide or trifluoromethyl iodide contains an iodoalkyl group; through a nucleophilic substitution reaction, the thiol group is coupled to the iodoalkyl group of the trifluoroethyl iodide to form a thioether bond, obtaining a first thioether intermediate; providing an oxidizing agent, mixing the first thioether intermediate and the organic solvent, and then reacting with the oxidizing agent... An oxidation reaction is performed to oxidize the thioether bond to a sulfonyl group to obtain an electrolyte additive; or, if the sulfonation solvent is 2-chloroethanesulfonyl chloride, a cyano-containing thiol compound, 2-chloroethanesulfonyl chloride, an organic solvent, and an acid-binding agent are mixed for sulfonation, wherein the cyano-containing thiol compound contains a thiol group, and the 2-chloroethanesulfonyl chloride contains a sulfonyl chloride group. The sulfonation reaction couples the thiol group with the sulfonyl chloride group to form a thioether bond, obtaining a second thioether intermediate; an oxidizing agent is provided, and the second thioether intermediate and the organic solvent are mixed and then subjected to an oxidation reaction with the oxidizing agent to oxidize the thioether bond to a sulfonyl group to obtain a sulfonyl intermediate; a fluorinating agent is provided, and the sulfonyl intermediate is subjected to an exchange reaction with the fluorinating agent to obtain an electrolyte additive.

[0007] Preferably, the cyano-containing haloalkane is chloroacetonitrile or 3-chloropropionitrile; the organic solvent includes dichloromethane, anhydrous acetonitrile, or tetrahydrofuran; the oxidant includes any one or a combination of several of m-chloroperoxybenzoic acid, hydrogen peroxide, potassium persulfate, potassium permanganate, sodium hypochlorite, sodium chlorite, dimethyldioxyethylene, or sodium perborate; and the acid-binding agent includes any one or a combination of several of triethylamine, pyridine, N,N-diisopropylethylamine, 4-dimethylaminopyridine, N-methylmorpholine, 2,6-dimethylpyridine, or potassium carbonate.

[0008] Preferably, the method of obtaining a cyano-containing thiol compound by nucleophilic substitution reaction of a cyano-containing haloalkane with sodium hydrosulfide comprises: providing an alcohol solvent; mixing the cyano-containing haloalkane and the alcohol solvent at 0°C-5°C, and then adding sodium hydrosulfide to obtain a mixed solution, wherein the molar ratio of the cyano-containing haloalkane to sodium hydrosulfide in the mixed solution is 1:(1.1-1.2); heating the mixed solution to 35°C-40°C and reacting for 1.5-2.0 hours; and filtering and distilling the mixed solution after the reaction to obtain the cyano-containing thiol compound. If the cyano-containing haloalkane is chloroacetonitrile, the distillation process involves collecting the fraction distilled at a temperature between 80°C and 85°C under a vacuum of 10 mmHg-20 mmHg to obtain a cyano-containing mercapto compound, wherein the cyano-containing mercapto compound is mercaptoacetonitrile; if the cyano-containing haloalkane is 3-chloropropionitrile, the distillation process involves collecting the fraction distilled at a temperature between 95°C and 100°C under a vacuum of 10 mmHg-20 mmHg to obtain a cyano-containing mercapto compound, wherein the cyano-containing mercapto compound is 3-mercaptopropionitrile.

[0009] Preferably, if the thiol-functionalizing agent is trifluoroethyl iodine: the cyano-containing thiol compound is mercaptoacetonitrile, the organic solvent is tetrahydrofuran, and the acid-binding agent is anhydrous potassium carbonate; mercaptoacetonitrile and tetrahydrofuran are mixed to form a first solution, anhydrous potassium carbonate is added to the first solution to obtain a pre-solution, trifluoroethyl iodine and tetrahydrofuran are mixed under an inert gas atmosphere at a temperature of 0°C-5°C to form a second solution, the second solution is added dropwise to the first solution to obtain a mixed solution, wherein the molar ratio of mercaptoacetonitrile:trifluoroethyl iodine:anhydrous potassium carbonate in the mixed solution is 1:(1.0~1.1):(1.1~1.3); the mixed solution is heated to 20°C-25°C and reacted for 5-8 hours, and the mixed solution after reaction is washed and dried to obtain a first sulfide intermediate. The first sulfide intermediate is 2,2,2-trifluoroethyl thioacetonitrile (NC-CH2-S-CH2-CF3); after obtaining the first sulfide intermediate, the method further includes: mixing 2,2,2-trifluoroethyl thioacetonitrile (NC-CH2-S-CH2-CF3) and dichloromethane, and then adding an oxidant at 0°C-5°C to obtain a mixed solution, wherein the molar ratio of the first sulfide intermediate to the oxidant in the mixed solution is 1:(2.4~3.0); heating the mixed solution to 20°C-25°C and reacting for 10-14 hours, and washing and drying the mixed solution after the reaction to obtain an electrolyte additive, which is (2,2,2-trifluoroethyl)sulfonyl acetonitrile (NC-CH2-SO2-CH2-CF3).

[0010] Preferably, the thiol-functionalizing reagent is trifluoromethyl iodine; the cyano-containing thiol compound is 3-mercaptopropionitrile; the organic solvent is anhydrous acetonitrile; and the acid-binding agent is anhydrous potassium carbonate. 3-mercaptopropionitrile and anhydrous acetonitrile are mixed to form a first solution. Anhydrous potassium carbonate is added to the first solution to obtain a pre-solution. Trifluoromethyl iodine is passed through the pre-solution under an inert gas atmosphere at 0°C-5°C to obtain a mixed solution, wherein the molar ratio of 3-mercaptopropionitrile:trifluoromethyl iodine:anhydrous potassium carbonate in the mixed solution is 1:(1.1~1.2):(1.3~1.5). The mixed solution is heated to 20°C-25°C and reacted for 6-8 hours. The reacted mixed solution is washed and dried to obtain the first thioether intermediate. The first sulfide intermediate is 3-(trifluoromethylthio)propionitrile (NC-CH2CH2-S-CF3); after obtaining the first sulfide intermediate, the method further includes: mixing 3-(trifluoromethylthio)propionitrile (NC-CH2CH2-S-CF3) and dichloromethane, and then adding an oxidant at 0°C-5°C to obtain a mixed solution, wherein the molar ratio of the first sulfide intermediate to the oxidant in the mixed solution is 1:(2.4~3.0); heating the mixed solution to 20°C-25°C and reacting for 12-15 hours, and washing and drying the mixed solution after the reaction to obtain an electrolyte additive, the electrolyte additive being 3-(trifluoromethylsulfonyl)propionitrile (NC-CH2CH2-SO2-CF3).

[0011] Preferably, if the sulfonation solvent is 2-chloroethanesulfonyl chloride: the cyano-containing thiol compound is mercaptoacetonitrile, the organic solvent is dichloromethane, and the acid-binding agent is triethylamine; mercaptoacetonitrile and dichloromethane are mixed to form a first solution, and the acid-binding agent is added to the first solution to obtain a pre-solution; 2-chloroethanesulfonyl chloride and dichloromethane are mixed under an inert gas atmosphere at a temperature of 0°C-5°C to form a second solution; the second solution is added dropwise to the first solution at a rate maintaining the reaction solution temperature not exceeding 5°C to obtain a mixed solution, wherein the mixed solution contains mercaptoacetonitrile: The molar ratio of 2-chloroethanesulfonyl chloride to triethylamine is 1:(1.0~1.1):(1.1~1.2); the mixed solution is heated to 20°C-25°C and reacted for 4-5 hours. The mixed solution after reaction is washed and dried to obtain the first sulfide intermediate, which is 2-(cyanomethylthio)ethanesulfonyl chloride (NC-CH2-S-CH2CH2-SO2-Cl); after obtaining the first sulfide intermediate, the process further includes: reacting 2-(cyanomethylthio)ethanesulfonyl chloride (NC-CH2) with triethylamine. The mixture of 2-(cyanomethylsulfonyl)ethane and dichloromethane was then subjected to an oxidant at 0°C-5°C to obtain a mixed solution, wherein the molar ratio of the first sulfide intermediate to the oxidant in the mixed solution was 1:(2.4~3.0). The mixed solution was heated to 20°C-25°C and reacted for 10-12 hours. The resulting mixed solution was washed and dried to obtain a sulfonyl intermediate, which was 2-(cyanomethylsulfonyl)ethanesulfonyl chloride (NC-CH2-SO2-CH2CH2-S). O2-Cl); potassium fluoride and a polar solvent are provided. The sulfonyl intermediate and the polar solvent are mixed and then potassium fluoride is added to obtain a mixed solution, wherein the molar ratio of sulfonyl intermediate to potassium fluoride in the mixed solution is 1:(3.0~3.5); the mixed solution is heated to 60-65°C and reacted for 4-5 hours. The mixed solution after reaction is washed and dried to obtain an electrolyte additive, which is 2-(cyanomethylsulfonyl)ethanesulfonyl fluoride (NC-CH2-SO2-CH2CH2-SO2-F).

[0012] The present invention also provides an electrolyte additive, which is prepared based on the above-described method for preparing electrolyte additives, wherein the electrolyte additive is (2,2,2-trifluoroethyl)sulfonyl acetonitrile, 3-(trifluoromethylsulfonyl)propionitrile, or 2-(cyanomethylsulfonyl)ethanesulfonyl fluoride.

[0013] The present invention also provides a battery comprising a positive electrode, an electrolyte layer and a negative electrode stacked together, wherein the electrolyte layer comprises electrolyte additives as described above.

[0014] The present invention also provides an electronic device, including a device body and the battery described above, wherein the solid-state battery is disposed within the device body.

[0015] Compared with the prior art, the preparation method and electrolyte additive provided by the present invention have the following beneficial effects: 1. The preparation method of the electrolyte additive provided in this invention relies heavily on pre-prepared complex aromatic sulfonyl chlorides as functional group donors. These methods have fixed skeletons, limited derivatization, and the introduced aromatic rings do not benefit electrolyte performance. This invention proposes a self-assembly route based on thiol-functionalized reagents. Starting from cyano-containing haloalkanes, key thiol intermediates are synthesized. Then, by flexibly switching electrophilic reagents, such as choosing trifluoroethyl iodide or trifluoromethyl iodide to directly introduce trifluoromethyl groups, or choosing 2-chloroethanesulfonyl chloride to obtain sulfonyl fluoride groups via subsequent fluorination, different fluorinated functional groups can be efficiently introduced on the same platform. This embodiment integrates cyano, sulfonyl, and fluorinated functional groups simultaneously through a two-step nucleophilic substitution-oxidation reaction. The simplified steps are more conducive to constructing a dense and thin stable interfacial film on the electrode surface. Among them, the sulfonyl group can form a flexible interfacial framework containing sulfur-oxygen bonds, which has good lithium-ion conductivity. As the voltage is further increased, the cyano group is further oxidized and polymerized on the positive electrode surface, and crosslinked on the sulfonyl group framework to form a dense protective layer rich in carbon-nitrogen triple bond features. The sulfonyl group provides ion conduction channels and a flexible substrate, while the cyano group provides an antioxidant barrier and mechanical strength, thus constructing a gradient positive electrode interfacial film with an inner flexible ion conduction layer and an outer dense antioxidant layer. At the same time, the fluorine-containing functional group is reduced and decomposed on the negative electrode surface to generate a solid electrolyte interfacial film rich in lithium fluoride. This film has high mechanical strength and a wide electrochemical window, which can effectively suppress the side reactions between the negative electrode and the electrolyte. Meanwhile, the high electronegativity of the fluorine-containing functional group helps to reduce the lithium-ion desolvation energy barrier and improve the charge transfer efficiency at the interface. The three functional groups work in an orderly and synergistic manner in the electrochemical reaction, enabling the positive electrode to obtain an interface layer with both anti-oxidation and ion conduction functions, and the negative electrode to obtain a stable and low-impedance protective layer. This simultaneously improves the battery's cycle stability at high voltage and its discharge capability at high rate, solving the problem that existing electrolyte additives cannot achieve both high-voltage stability and high-rate performance.

[0016] 2. The electrolyte additive prepared by this method contains three types of functional groups: cyano, sulfonyl, and fluorine-containing functional groups. During the operation of the lithium-ion battery, the cyano group, as a high-voltage stabilizing group, preferentially adsorbs on the positive electrode surface and undergoes oxidative polymerization as the charging voltage increases, forming a dense interfacial protective layer rich in carbon-nitrogen triple bonds. This layer can effectively inhibit the direct contact and oxidative decomposition of the electrolyte on the positive electrode surface, and simultaneously chelate the transition metal ions dissolved from the positive electrode through coordination, thus slowing down the structural degradation of the positive electrode material. The sulfonyl group generates a flexible interfacial component containing sulfur-oxygen bonds through oxidation. This component constructs a framework structure with lithium-ion conductivity at the positive electrode interface, avoiding the blockage of lithium-ion transport channels by an overly dense single cyano film layer, thereby balancing interfacial density and ion conductivity. Fluorine-containing functional groups undergo reduction and decomposition on the negative electrode surface, generating a lithium fluoride-rich solid electrolyte interfacial film. This film possesses high mechanical strength and a wide electrochemical window, effectively suppressing side reactions between the negative electrode and the electrolyte. Simultaneously, the fluorine-containing functional groups participate in the regulation of the lithium-ion solvation sheath, lowering the lithium-ion desolvation energy barrier and improving charge transfer efficiency at the interface. The synergistic effect of the three functional groups jointly solves the problem of existing additives failing to simultaneously achieve high-voltage stability and high-rate performance.

[0017] 3. The battery provided by the present invention contains the above-mentioned trifunctional electrolyte additives in its electrolyte layer, which can synergistically construct a gradient-distributed and functionally complementary interface protective film on the positive and negative electrode surfaces. The cyano group enhances the high-voltage oxidation resistance, the sulfonyl group provides a flexible ion conduction channel, and the fluorinated alkyl group forms a dense and stable fluorine-rich interface on the negative electrode, thereby effectively reducing the interface impedance, suppressing side reactions, and significantly improving the cycle stability, rate performance and safety of the battery under high voltage and high rate conditions.

[0018] 4. The electronic device provided by the present invention uses the above-mentioned high-performance battery, and the device can still maintain a stable and reliable power supply under the conditions of high-power fast charging, wide temperature range and long-term cycle use, thus meeting the dual requirements of battery life and safety. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic flowchart of the preparation method of the electrolyte additive provided in the first embodiment of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0022] In the embodiments provided by this invention, it should be understood that "B corresponding to A" means that B is associated with A, and B can be determined based on A. However, it should also be understood that determining B based on A does not mean determining B solely based on A; B can also be determined based on A and / or other information.

[0023] It should be understood that the phrase "one embodiment" or "an embodiment" throughout the specification means that a specific feature, structure, or characteristic related to the embodiment is included in at least one embodiment of the invention. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Those skilled in the art should also recognize that the embodiments described in the specification are optional embodiments, and the actions and modules involved are not necessarily essential to the invention.

[0024] In various embodiments of the present invention, it should be understood that the sequence number of each process does not necessarily imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0025] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of this application. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, or they may sometimes be executed in reverse order, depending on the functions involved. It is particularly important to note that each block in a block diagram and / or flowchart, and combinations of blocks in block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0026] Please refer to the figure. The first embodiment of the present invention provides a method for preparing an electrolyte additive, which includes the following steps: Step S1: Provide a cyano-containing haloalkane and sodium hydrosulfide, and perform a nucleophilic substitution reaction between the cyano-containing haloalkane and sodium hydrosulfide to obtain a cyano-containing mercapto compound. Step S2: Provide a thiol-functionalized reagent, and react a cyano-containing thiol compound with the thiol-functionalized reagent to obtain an intermediate containing a thioether bond; Step S3: The intermediate containing the thioether bond is oxidized with an oxidizing agent to convert the thioether bond into a sulfonyl group, thereby obtaining a sulfonyl intermediate; Step S4: Select the type of thiol functionalizing agent; Step S5: If the thiol-functionalizing agent is trifluoroethyl iodide or trifluoromethyl iodide, the trifluoromethyl group in the trifluoroethyl iodide or trifluoromethyl iodide is introduced through a nucleophilic substitution reaction, and after oxidation, a sulfonyl intermediate is obtained. The sulfonyl intermediate is an electrolyte additive including cyano, sulfonyl, and trifluoromethyl functional groups; or Step S6: If the thiol functionalizing agent is 2-chloroethanesulfonyl chloride, the sulfonyl chloride group of 2-chloroethanesulfonyl chloride is introduced into the sulfonyl intermediate through a sulfonylation reaction to provide a fluorinating agent. The sulfonyl intermediate and the fluorinating agent react to obtain a fluorinated product, wherein the chlorine atom is replaced by a fluorine atom to obtain a sulfonyl fluoride group. The fluorinated product is an electrolyte additive including cyano, sulfonyl, and sulfonyl fluoride functional groups.

[0027] It should be understood that this embodiment first converts a cyano-containing haloalkane into a cyano-containing mercapto compound via a nucleophilic substitution reaction. Then, a mercapto-functionalizing agent is used to introduce a fluorinated alkyl group at the mercapto site, forming an intermediate containing a thioether bond. This thioether bond is then converted to a sulfonyl group via oxidation, yielding an intermediate containing a sulfonyl group. It should be noted that when obtaining the intermediate containing a sulfonyl group, depending on the type of cyano-containing haloalkane selected and the type of mercapto-functionalizing agent used, an electrolyte additive can be selectively obtained directly or through a fluorination reaction. Specifically, the choice of mercapto-functionalizing agent determines the structure of the final product. When the mercapto-functionalizing agent is trifluoroethyl iodide or trifluoromethyl iodide, the trifluoromethyl group in trifluoroethyl iodide or trifluoromethyl iodide is directly introduced into the molecular skeleton via a nucleophilic substitution reaction. After oxidation, the intermediate containing a sulfonyl group will have three functional groups: cyano, trifluoromethyl, and sulfonyl, and this intermediate can be directly used as an electrolyte additive. When the thiol-functionalizing agent is 2-chloroethanesulfonyl chloride, the sulfonyl chloride group is introduced into the molecular skeleton through a sulfonylation reaction to form a thioether bond. Following an oxidation reaction, the thioether bond is oxidized to a sulfonyl group. Then, a halogen exchange reaction is carried out using a fluorinating agent to convert the sulfonyl chloride group into a sulfonyl fluoride group, thus obtaining an electrolyte additive containing a sulfonyl fluoride group. This electrolyte additive possesses three functional groups: cyano, sulfonyl, and sulfonyl fluoride. Specifically, using a cyano-containing haloalkane as the starting material, the cyano functional group in its molecule remains stable throughout the subsequent reaction process and does not participate in nucleophilic substitution, sulfonation, oxidation, or fluorination reactions. Therefore, the cyano structure is completely preserved in the final additive product. This cyano functional group can form coordination with transition metal ions at the positive electrode interface of a lithium-ion battery, inhibiting the dissolution of high-valence transition metals and improving the cycle stability of the battery under high-voltage conditions. The oxidation step converts the thioether bond into a sulfonyl group. The sulfonyl group has strong electron-withdrawing properties, giving the intermediate containing the sulfonyl group strong antioxidant capacity and interfacial film-forming activity. On the positive electrode surface, it can oxidatively polymerize to form a flexible interfacial layer containing sulfur-oxygen bonds. This interfacial layer has good lithium-ion conductivity, reducing the transport impedance of lithium ions at the interface between the positive electrode and the electrolyte, thereby improving the battery's rate performance. Meanwhile, trifluoromethyl or sulfonyl fluoride groups are both fluorine-containing functional groups, and on the negative electrode surface, they can be reduced and decomposed to generate a solid electrolyte interfacial film rich in lithium fluoride.

[0028] Specifically, the electrolyte additive of this invention contains three types of functional groups: cyano, sulfonyl, and fluorine-containing functional groups, wherein the fluorine-containing functional group can be trifluoromethyl or sulfonyl fluoride. During lithium-ion battery charging, the sulfonyl group can form a flexible interfacial framework containing sulfur-oxygen bonds, exhibiting good lithium-ion conductivity. As the voltage further increases, the cyano group further oxidizes and polymerizes on the positive electrode surface, crosslinking on the sulfonyl group to form a dense protective layer rich in carbon-nitrogen triple bonds. The sulfonyl group provides ion conduction channels and a flexible substrate, while the cyano group provides an antioxidant barrier and mechanical strength, constructing a gradient positive electrode interfacial film with an inner flexible ion-conducting layer and an outer dense antioxidant layer. Simultaneously, the fluorine-containing functional group is reduced and decomposed on the negative electrode surface, generating a solid electrolyte interfacial film rich in lithium fluoride. This film has high mechanical strength and a wide electrochemical window, effectively suppressing side reactions between the negative electrode and the electrolyte; at the same time, the high electronegativity of the fluorine-containing functional group helps to reduce the lithium-ion desolvation energy barrier and improve the charge transfer efficiency at the interface. The three functional groups work in an orderly and synergistic manner in the electrochemical reaction, enabling the positive electrode to obtain an interface layer with both anti-oxidation and ion conduction functions, and the negative electrode to obtain a stable and low-impedance protective layer. This simultaneously improves the battery's cycle stability at high voltage and its discharge capability at high rate, solving the problem that existing electrolyte additives cannot achieve both high-voltage stability and high-rate performance.

[0029] Specifically, after providing the thiol-functionalized reagent, the specific steps include: A sulfonating solvent, dichloromethane, and an acid-binding agent are provided. The sulfonating solvent, dichloromethane, and acid-binding agent are mixed to obtain a mercapto-functionalized reagent. It should be noted that in this embodiment, two different fluorinated functionalized solid electrolyte additive products can be prepared by switching the type of sulfonating solvent, as detailed below: In one possible implementation, if the thiol-functionalizing agent is trifluoroethyl iodide or trifluoromethyl iodide, a cyano-containing thiol compound, trifluoroethyl iodide or trifluoromethyl iodide, an organic solvent, and an acid-binding agent are mixed and subjected to a nucleophilic substitution reaction. The cyano-containing thiol compound contains a thiol group, and the trifluoroethyl iodide or trifluoromethyl iodide contains an iodoalkyl group. The thiol group is coupled to the iodoalkyl group of the trifluoroethyl iodide through the nucleophilic substitution reaction to form a thioether bond, thus obtaining a first thioether intermediate. An oxidant is provided, and the first thioether intermediate and the organic solvent are mixed and subjected to an oxidation reaction with the oxidant to oxidize the thioether bond to a sulfonyl group to obtain an electrolyte additive.

[0030] It should be understood that when trifluoroethyl iodine is used as the thiol-functionalizing agent, the pathway only requires two consecutive steps: nucleophilic substitution and oxidation, eliminating the need for an additional fluorination step and simplifying the overall synthetic process. Since the nucleophilic substitution reaction can be carried out in organic solvent systems such as tetrahydrofuran or acetonitrile, and the oxidation reaction can be carried out in a dichloromethane system, and the acid-binding agent can effectively neutralize the hydrogen iodide produced in the reaction, maintaining a neutral environment in the reaction system and avoiding impurities and material losses that may be introduced during the separation and purification of intermediates, the oxidant can be directly added to the reaction vessel containing the intermediates, achieving two consecutive steps, shortening the total reaction time, reducing solvent consumption and energy input, and helping to improve production efficiency and reduce preparation costs. Meanwhile, trifluoroethyl iodide, as a thiol-functionalized reagent, inherently possesses a trifluoromethyl functional group. This group is directly introduced into the first thioether intermediate framework during nucleophilic substitution coupling and is completely retained in the final product after oxidation, eliminating the need for additional grafting via subsequent fluorination reactions. This avoids potential side reactions and functional group tolerance issues caused by halogen exchange reactions, resulting in a more defined target product structure and easier purification. Specifically, the final electrolyte additive contains cyano, sulfonyl, and trifluoromethyl functional groups. The cyano group preferentially adsorbs on the cathode surface and undergoes oxidative polymerization at high potentials, forming an interfacial protective layer rich in carbon-nitrogen triple bonds. This protective layer has a dense structure and good antioxidant capacity, inhibiting the oxidative decomposition of the electrolyte on the cathode surface and suppressing the dissolution of transition metal ions through coordination. The sulfonyl group participates in constructing a flexible framework containing sulfur-oxygen bonds at the cathode interface. This framework possesses lithium-ion conductivity, reducing interfacial impedance and preventing the obstruction of ion transport caused by an overly dense single cyano film layer. Trifluoromethyl groups can be reduced and decomposed on the negative electrode surface to generate a lithium fluoride-rich solid electrolyte interfacial film. This film exhibits high mechanical strength and electrochemical stability, effectively suppressing negative electrode side reactions. Simultaneously, the strong electronegativity of trifluoromethyl groups helps regulate the lithium-ion solvation sheath structure, lowering the desolvation energy barrier when lithium ions cross the interface. The three functional groups are spatially separated within the molecule, forming an ordered synergy in electrochemical response. This results in the positive electrode acquiring an interfacial layer with both antioxidant and ion-conducting functions, and the negative electrode acquiring a stable and low-impedance protective layer, thereby simultaneously improving the battery's cycle stability at high voltages and its discharge capability at high rates.

[0031] In another possible implementation, if the sulfonating agent is 2-chloroethanesulfonyl chloride, a sulfonylation reaction is carried out by mixing a cyano-containing thiol compound, 2-chloroethanesulfonyl chloride, dichloromethane, and an acid-binding agent, so that the thiol group is coupled with the sulfonyl chloride group to form a thioether bond, thereby obtaining a second thioether intermediate; an oxidizing agent is provided, and the second thioether intermediate and dichloromethane are mixed and then subjected to an oxidation reaction with the oxidizing agent to oxidize the thioether bond to a sulfonyl group to obtain a sulfonyl intermediate; a fluorinating agent is provided, and the sulfonyl intermediate is subjected to an exchange reaction with the fluorinating agent to obtain an electrolyte additive.

[0032] Specifically, the two-step route used in this embodiment first obtains a sulfonyl intermediate, and then further converts the sulfonyl chloride group into a sulfonyl fluoride group through a fluorination exchange reaction. The sulfonyl fluoride functional group can also participate in the reduction and decomposition process at the lithium-ion battery anode interface, generating a lithium fluoride-rich solid electrolyte interface film. This film has high mechanical strength and a wide electrochemical window, effectively suppressing side reactions between the anode and the electrolyte, and improving the long-term stability of the anode interface. Simultaneously, the sulfur-fluorine bond in the sulfonyl fluoride group has a higher bond energy and lower reactivity than the sulfur-chlorine bond in the sulfonyl chloride group, enhancing the chemical and storage stability of the final product in the electrolyte, making it less prone to hydrolysis or side reactions with other electrolyte components, thus extending the electrolyte's lifespan. Furthermore, the 2-chloroethanesulfonyl chloride raw material has different reactivity and spatial structure compared to trifluoroethyl iodine. The ethylene linking chain in its molecule endows the second sulfide intermediate with a longer bridging structure. After subsequent oxidation and fluorination reactions, the ethylene linking chain becomes the spacer unit between the cyano group and the sulfonyl fluoride group functional group, which increases the spatial distance between the cyano group and the sulfonyl fluoride group in the final product molecule. This is beneficial for the spatial separation of the cyano group on the positive electrode surface and the sulfonyl fluoride group on the negative electrode surface, and reduces the mutual interference between the two functional groups during the reaction at the electrode interface. The two-step synthesis route introduces sulfonyl fluoride functional groups through the 2-chloroethanesulfonyl chloride pathway and subsequent fluorination exchange reaction. The resulting electrolyte additive contains three functional groups: cyano, sulfonyl, and sulfonyl fluoride. The cyano functional group plays an antioxidant role on the positive electrode surface, the sulfonyl group provides interfacial lithium-ion conduction channels, and the sulfonyl fluoride functional group constructs a stable lithium fluoride interfacial film on the negative electrode. The three functional groups form a spatially separated and potential-responsive synergistic system, which improves the battery's high-voltage cycle stability and high-rate discharge performance.

[0033] Specifically, the cyano-containing haloalkanes are chloroacetonitrile or 3-chloropropionitrile. It should be understood that the specific choice of chloroacetonitrile or 3-chloropropionitrile for the cyano-containing haloalkanes is due to the presence of an active chlorine atom that can undergo a highly efficient nucleophilic substitution reaction with the mercapto anion of sodium hydrosulfide. After the chlorine atom is replaced by the mercapto group, a carbon-sulfur bond is formed, yielding the corresponding mercaptoacetonitrile or mercaptopropionitrile. Chloroacetonitrile and 3-chloropropionitrile are widely available industrial raw materials, inexpensive, and stable in storage. Furthermore, the cyano group in their molecular structure remains inert under nucleophilic substitution reaction conditions and does not participate in side reactions. Therefore, they can generate the target cyano-containing mercapto compound with high selectivity under mild conditions, providing a high-purity key intermediate for the subsequent sulfonation step and avoiding the impact of insufficient intermediate purity on the efficiency of subsequent reactions. Furthermore, the carbon chain lengths of chloroacetonitrile and 3-chloropropionitrile are one and two methylene units, respectively, resulting in different spacing between the cyano and mercapto groups in the final cyano-thiol-containing compounds. This chain length difference can regulate the spatial distance and electron transfer effect between the cyano and sulfonyl groups in the final electrolyte additive.

[0034] Specifically, oxidants include any one or a combination of several of the following: m-chloroperoxybenzoic acid, hydrogen peroxide, potassium persulfate complex salt, potassium permanganate, sodium hypochlorite, sodium chlorite, dimethyldioxyethylene, or sodium perborate. It should be understood that all oxidants possess moderate oxidizing power, capable of selectively oxidizing the thioether bonds in the first or second thioether intermediate to sulfonyl groups without over-oxidizing cyano groups or other functional groups such as carbon-carbon bonds in the molecule. Among these, m-chloroperoxybenzoic acid, as an organic peroxyacid, exhibits good solubility in dichloromethane, making it suitable for oxidation reactions in heterogeneous systems. Hydrogen peroxide and potassium persulfate complex salt provide convenient options for oxidation in aqueous systems. Users can flexibly select the appropriate oxidant type based on actual reaction conditions and equipment configuration. The diversity of oxidant types provides adaptability at different production scales; in industrial production, the optimal oxidant can be selected based on cost.

[0035] Specifically, acid-binding agents include any one or a combination of several of triethylamine, pyridine, N,N-diisopropylethylamine, 4-dimethylaminopyridine, N-methylmorpholine, 2,6-dimethylpyridine, or potassium carbonate. It should be understood that these acid-binding agents are all basic compounds capable of effectively neutralizing the hydrogen chloride byproduct generated from the coupling reaction between the thiol group and the sulfonyl chloride group during the sulfonation reaction. If the hydrogen chloride is not neutralized in time, it will increase the acidity of the reaction system, potentially causing the thiol group in the cyano-containing thiol compound to protonate and reduce its nucleophilic activity. Under acidic conditions, the sulfonyl chloride may also undergo hydrolysis to generate sulfonic acid, consuming reactants and reducing the yield of the target product. The addition of an acid-binding agent maintains the reaction system in a weakly alkaline to neutral environment, ensuring that the sulfonation reaction proceeds under optimal conditions. Furthermore, the diversity of acid-binding agents allows for the selection of a suitable agent based on the reactivity of the sulfonation solvent and the required reaction temperature. For example, triethylamine and pyridine are commonly used organic bases, offering advantages such as low cost and easy removal after the reaction. 4-Dimethylaminopyridine, on the other hand, exhibits stronger catalytic activity and is suitable for systems with lower reactivity. This embodiment demonstrates high selectivity and adaptability in various implementation scenarios.

[0036] In step S1 above, the nucleophilic substitution reaction of a cyano-containing haloalkane with sodium hydrosulfide to obtain a cyano-containing mercapto compound includes: An alcohol solvent is provided. A cyano-containing haloalkane and an alcohol solvent are mixed at 0°C-5°C, and then sodium hydrosulfide is added to obtain a mixed solution, wherein the molar ratio of the cyano-containing haloalkane to sodium hydrosulfide in the mixed solution is 1:(1.1-1.2). The mixed solution was heated to 35°C-40°C and reacted for 1.5-2.0 hours. The resulting mixed solution was then filtered and distilled to obtain a cyano-containing mercapto compound.

[0037] In one possible implementation, if the cyano-containing haloalkane is chloroacetonitrile, the distillation process involves collecting the fraction distilled at a temperature between 80°C and 85°C under a vacuum of 10 mmHg-20 mmHg to obtain a cyano-containing mercapto compound, wherein the cyano-containing mercapto compound is mercaptoacetonitrile. Optionally, in this embodiment, the distillation process can also be carried out under a vacuum of 10 mmHg-13 mmHg, 13 mmHg-17 mmHg, or 17 mmHg-20 mmHg.

[0038] Specifically, the reaction formula for the production of mercaptoacetonitrile from the reaction of chloroacetonitrile with sodium hydrosulfide is as follows: Cl-CH2-CN+NaSH→HS-CH2-CN+NaCl In another possible embodiment, if the cyano-containing haloalkane is 3-chloropropionitrile, the distillation process involves collecting the fraction distilled at a temperature between 95°C and 100°C under a vacuum of 10 mmHg to 20 mmHg to obtain a cyano-containing mercapto compound, wherein the cyano-containing mercapto compound is 3-mercaptopropionitrile. Optionally, in this embodiment, the distillation process can also be carried out under a vacuum of 10 mmHg to 13 mmHg, 13 mmHg to 17 mmHg, or 17 mmHg to 20 mmHg.

[0039] Specifically, the reaction formula for the formation of 3-mercaptopropionitrile from sodium hydrosulfide is as follows: Cl-CH2CH2-CN+NaSH→HS-CH2CH2-CN+NaCl Understandably, in this embodiment, an alcohol solvent is first provided, and the cyano-containing haloalkane and the alcohol solvent are mixed at a low temperature of 0°C-5°C. Sodium hydrosulfide is then added to obtain a mixed solution, wherein the molar ratio of the cyano-containing haloalkane to sodium hydrosulfide is 1:(1.1-1.2). The mixed solution is then heated to 35°C-40°C and reacted for 1.5-2.0 hours. After the reaction, the mixed solution is filtered and distilled. The low-temperature addition step effectively controls the initial rate of the nucleophilic substitution reaction, avoiding localized overheating due to excessively vigorous reaction, thereby reducing the occurrence of side reactions. The amount of sodium hydrosulfide is slightly excess relative to the cyano-containing haloalkane, ensuring that the chlorine atom in the cyano-containing haloalkane is fully substituted, allowing the reaction to proceed completely in the forward direction and improving the conversion rate of the starting material. The reaction temperature was controlled within a mild range of 35°C-40°C, providing sufficient activation energy to facilitate the nucleophilic substitution reaction without causing oxidative coupling or other side reactions in the thiol compound due to excessively high temperatures. Specifically, when the cyano-containing haloalkane was chloroacetonitrile, the fraction distilled at 80°C to 85°C was collected under a vacuum of 15 mmHg to obtain mercaptoacetonitrile. When the cyano-containing haloalkane was 3-chloropropionitrile, the fraction distilled at 95°C to 100°C was collected under a vacuum of 15 mmHg to obtain 3-mercaptopropionitrile. Different distillation temperature ranges were set for cyano-containing thiol compounds with different carbon chain lengths. Due to the different molecular weights of mercaptoacetonitrile and 3-mercaptopropionitrile, their boiling points differed. By controlling the distillation temperature and vacuum, the cyano-containing thiol compound was effectively separated from unreacted raw materials, byproducts, and solvents. Alternatively, the molar ratio of haloalkane to sodium hydrosulfide can be 1:1.05, 1:1.08, or 1:1.15.

[0040] It should be noted that after step S2 above, there are multiple routes to prepare electrolyte additives in this embodiment, and each route has specific experimental steps.

[0041] In one embodiment, a nucleophilic substitution reaction is carried out by mixing a cyano-containing mercapto compound, trifluoroethyl iodine, an organic solvent, and an acid-binding agent: The cyano-containing mercapto compound is mercaptoacetonitrile, the organic solvent is tetrahydrofuran, and the acid-binding agent is anhydrous potassium carbonate; A first solution is formed by mixing mercaptoacetonitrile and tetrahydrofuran. Anhydrous potassium carbonate is added to the first solution to obtain a pre-solution. Trifluoroethyl iodide and tetrahydrofuran are mixed under an inert gas atmosphere at a temperature of 0°C-5°C to form a second solution. The second solution is added dropwise to the first solution to obtain a mixed solution. The molar ratio of mercaptoacetonitrile:trifluoroethyl iodide:anhydrous potassium carbonate in the mixed solution is 1:(1.0~1.1):(1.1~1.3). The mixed solution was heated to 20°C-25°C and reacted for 5-8 hours. The mixed solution after reaction was washed and dried to obtain the first sulfide intermediate, which was 2,2,2-trifluoroethyl thioacetonitrile (NC-CH2-S-CH2-CF3).

[0042] Specifically, the reaction formula for the formation of 2,2,2-trifluoroethylthioacetonitrile from mercaptoacetonitrile, trifluoroethyl iodide, and triethylamine is as follows: HS-CH2-CN+CF3-CH2-I+K2CO3→NC-CH2-S-CH2-CF3+KI+KHCO3 Understandably, pre-mixing mercaptoacetonitrile with tetrahydrofuran to form a first solution and then adding anhydrous potassium carbonate allows the mercaptoacetonitrile to maintain the free state of its thiol groups in an alkaline environment with the presence of an acid-binding agent. This fully preserves the nucleophilic activity of the thiol anion. Simultaneously, the anhydrous potassium carbonate, as a solid inorganic base, is uniformly suspended in the reaction system, effectively neutralizing the hydrogen iodide generated during subsequent additions. Dissolving trifluoroethyl iodine separately in tetrahydrofuran to form a second solution allows for precise control of the introduction rate of the nucleophilic substitution reagent, avoiding excessively high local concentrations and concentrated heat release caused by a single addition. This effectively suppresses potential elimination or coupling side reactions of trifluoroethyl iodine under alkaline conditions. The low-temperature environment of 0°C-5°C further reduces the reaction rate in the initial stage, allowing the orderly formation of thioether bonds during addition. Simultaneously, the increased solubility of hydrogen iodide in tetrahydrofuran at low temperatures facilitates the timely capture of hydrogen iodide by potassium carbonate, preventing acid accumulation from damaging the structures of reactants and products.

[0043] Specifically, the molar ratio of mercaptoacetonitrile, trifluoroethyl iodide, and anhydrous potassium carbonate is limited to 1:(1.0~1.1):(1.1~1.3), with a slight excess of trifluoroethyl iodide relative to mercaptoacetonitrile. This ensures that all thiol groups in the mercaptoacetonitrile molecule participate in the coupling reaction, preventing unconverted mercaptoacetonitrile from remaining in the system due to insufficient reactant ratio. Residual mercaptoacetonitrile may be oxidized to disulfides and other byproducts in subsequent oxidation steps, increasing purification difficulty. Anhydrous potassium carbonate, used as an acid-binding agent, is in 10% to 30% excess relative to mercaptoacetonitrile. This is sufficient to neutralize all hydrogen iodide generated in the reaction and any acidic substances produced by trace amounts of water in the reaction system, ensuring the reaction system maintains a consistently weakly alkaline environment. The excess of potassium carbonate in the potassium-mercaptoacetonitrile molar ratio allows for easy removal of potassium iodide, potassium bicarbonate, etc., after the reaction, through filtration or washing, without contaminating the first sulfide intermediate. After the addition is complete, the mixed solution is heated to 20°C-25°C and kept at that temperature for 5-8 hours, which is sufficient to allow the nucleophilic substitution reaction to proceed completely, resulting in a high conversion rate of thioether bond formation.

[0044] Further, after the reaction is complete, inorganic salts, unreacted acid-binding agents, and residual water are removed sequentially by washing and drying to obtain a high-purity first thioether intermediate, 2,2,2-trifluoroethylthioacetonitrile. Specifically, the 2,2,2-trifluoroethylthioacetonitrile molecule simultaneously contains a cyano group, a thioether bond, and a trifluoromethyl functional group. The cyano group is located on a methylene group at one end of the molecule, and the trifluoromethyl group is separated from the cyano group by a methylene unit via a thioether bond. The short-chain structure ensures that after the molecule is subsequently oxidized to a sulfonyl group, the distance between the cyano group and the sulfonyl group is compact, which is beneficial for the formation of a thin-layer structure at the electrode interface. Optionally, the reaction time at 20°C-25°C can also be 5-6 hours, 6-7 hours, or 7-8 hours, and the molar ratio of mercaptoacetonitrile:trifluoroethyl iodine:potassium carbonate in the mixed solution can also be 1:1.02:1.15, 1:1.05:1.20, or 1:1.08:1.25.

[0045] Furthermore, after obtaining the first sulfide intermediate 2,2,2-trifluoroethyl thioacetonitrile (NC-CH2-S-CH2-CF3), the process further includes: 2,2,2-trifluoroethyl thioacetonitrile and dichloromethane were mixed and then an oxidant was added at 0°C-5°C to obtain a mixed solution, wherein the molar ratio of the first thioether intermediate to the oxidant in the mixed solution was 1:(2.4~3.0). The mixed solution is heated to 20°C-25°C and reacted for 10-14 hours. The mixed solution after reaction is washed and dried to obtain an electrolyte additive, which is (2,2,2-trifluoroethyl)sulfonyl acetonitrile.

[0046] Specifically, the oxidant is m-chloroperoxybenzoic acid (m-CPBA, C7H5ClO3), and the reaction formula for the formation of (2,2,2-trifluoroethyl thioacetonitrile) by reacting m-chloroperoxybenzoic acid is as follows: NC-CH2-S-CH2-CF3+2m-CPBA→NC-CH2-SO2-CH2-CF3+2m-CBA Understandably, adding the oxidant at a low temperature of 0°C-5°C effectively controls the initial rate of the oxidation reaction, avoiding excessively high local concentrations and concentrated heat release due to a single addition of the oxidant. This prevents side reactions such as over-oxidation of the thioether bond or breakage of the carbon-sulfur bond during the oxidation process. The thioether bond in the first thioether intermediate has lone pairs of electrons on two sulfur atoms. The oxidant can progressively oxidize the thioether bond to sulfoxides and sulfones. When the amount of oxidant is 2.4-3.0 times the molar amount of the first thioether intermediate, it ensures that the thioether bond is completely converted to a sulfonyl group, without remaining at the sulfoxide stage. This avoids the problem of inconsistent functional groups in the final product caused by the presence of a sulfinyl intermediate, which affects the consistency of film formation and the predictability of electrochemical behavior of the additive at the electrode interface. The appropriate excess of oxidant provides sufficient oxidation equivalent for complete reaction, while this dosage range does not lead to over-oxidation of stable structures such as cyano groups or carbon-fluorine bonds in the molecule. Optionally, the molar ratio of the first sulfide intermediate to the oxidant in the mixed solution can also be 1:2.5, 1:2.7 or 1:2.9.

[0047] Specifically, the mixed solution after adding the oxidant is heated to 20°C-25°C and reacted for 10-14 hours. This reaction temperature and time are moderate, providing sufficient activation energy to facilitate the oxidation reaction while avoiding side reactions that may be caused by the oxidant under high-temperature conditions. Dichloromethane, as the reaction solvent, remains inert during the oxidation process and does not participate in the oxidation reaction. At the same time, it can dissolve the first thioether intermediate and the oxidant, which is beneficial for the complete reaction between the oxidant and the thioether bond. After the reaction, residual oxidant and its reduction products are removed by washing, and moisture is removed by drying to obtain high-purity electrolyte additive (2,2,2-trifluoroethyl)sulfonylacetonitrile. Optionally, the reaction time at 20°C-25°C can also be 10-11 hours, 11-12 hours, or 12-14 hours.

[0048] It should be noted that in the electrolyte additive obtained in this embodiment, the original thioether bonds are oxidized to sulfonyl groups, forming a sulfonyl structure. Sulfonyl groups possess strong electron-withdrawing effects and polarity, endowing the molecule with good oxidative polymerization activity on the positive electrode surface, enabling it to participate in the construction of an interfacial film framework containing sulfur-oxygen bonds during charging. Simultaneously, the cyano group and trifluoromethyl group remain stable under oxidative conditions. The cyano group, as a high-voltage stabilizing group, can form a dense protective layer on the positive electrode surface, while the trifluoromethyl group, as a negative electrode interface regulating group, can be reduced to lithium fluoride at the negative electrode. Therefore, this oxidation reaction step achieves efficient conversion of thioether bonds to sulfonyl groups while completely preserving the functional structures of the cyano group and trifluoromethyl group, resulting in a final product containing all three functional groups.

[0049] In another embodiment, the nucleophilic substitution reaction involving a mixture of a cyano-containing mercapto compound, trifluoroethyl iodine, anhydrous acetonitrile, and an acid-binding agent comprises: The cyano-containing mercapto compound is 3-mercaptopropionitrile, the organic solvent is anhydrous acetonitrile, and the acid-binding agent is anhydrous potassium carbonate; 3-Mercaptopropionitrile and anhydrous acetonitrile are mixed to form a first solution. Anhydrous potassium carbonate is added to the first solution to obtain a pre-solution. Trifluoromethyl iodine gas is passed through the pre-solution in an inert gas atmosphere at a temperature of 0°C-5°C to obtain a mixed solution. The molar ratio of 3-mercaptopropionitrile:trifluoromethyl iodine:anhydrous potassium carbonate in the mixed solution is 1:(1.1~1.2):(1.3~1.5). The mixed solution is heated to 20°C-25°C and reacted for 6-8 hours. The mixed solution after reaction is washed and dried to obtain the first sulfide intermediate, which is 3-(trifluoromethylthio)propionitrile.

[0050] Specifically, the reaction formula for the formation of 3-(trifluoromethylthio)propionitrile from 3-mercaptopropionitrile, trifluoroethyl iodine, and anhydrous potassium carbonate is as follows: HS-CH2CH2-CN+CF3-I+K2CO3→NC-CH2CH2-S-CF3+KI+KHCO3 Understandably, when 3-mercaptopropionitrile is used instead of mercaptoacetonitrile as a raw material, the cyano and mercapto groups in its molecule are connected by an ethylene chain. Compared to the methylene chain in mercaptoacetonitrile, the carbon chain length is increased by one methylene unit. This difference in chain length increases the spatial distance between the mercapto and cyano groups in 3-mercaptopropionitrile. When the mercapto group undergoes a nucleophilic substitution reaction with trifluoroethyl iodide to form a thioether bond, the molecular span between the trifluoromethyl functional group and the cyano group is wider, resulting in different molecular conformations and flexibility in the first thioether intermediate. After subsequent oxidation to a sulfonyl group, the cyano and sulfonyl groups in the final electrolyte additive are separated by an ethylene chain. Compared to analogs separated by methylene chains, the intramolecular functional group spacing is larger, which may lead to different molecular arrangements and film thicknesses during film formation at the electrode interface.

[0051] Specifically, 3-mercaptopropionitrile is pre-mixed with anhydrous acetonitrile to form a first solution. The addition of anhydrous potassium carbonate as an acid-binding agent keeps the thiol group in a deprotonated state in an alkaline environment, maintaining its nucleophilic activity. Anhydrous potassium carbonate, as a solid inorganic base, is uniformly suspended in the reaction system, effectively neutralizing the hydrogen iodide generated in subsequent reactions. Trifluoroethyl iodine is added under an inert gas atmosphere at 0°C-5°C, effectively controlling the introduction rate of the nucleophilic substitution reagent and avoiding the violent exothermic coupling reaction caused by excessively high local concentrations. This prevents side reactions such as the decomposition of trifluoroethyl iodine or oxidative coupling of thiol groups due to sudden temperature increases. The low-temperature feeding environment of 0°C-5°C further ensures the stable progress of the initial stage of the reaction, allowing the orderly formation of thioether bonds and timely neutralization of the byproduct hydrogen iodide by potassium carbonate, avoiding the destruction of reactants and products by acid accumulation. The amount of trifluoroethyl iodine is slightly excess relative to 3-mercaptopropionitrile, ensuring complete conversion of the thiol group; the excess of anhydrous potassium carbonate keeps the reaction in a weakly alkaline atmosphere throughout. After the feed is completed, the temperature is raised to 20°C-25°C and maintained for 6-8 hours to achieve a high conversion rate in the nucleophilic substitution reaction. After the reaction, washing and drying effectively remove potassium iodide, potassium bicarbonate, unreacted acid-binding agents, and residual moisture, yielding a high-purity first sulfide intermediate, namely 3-(trifluoromethylthio)propionitrile (NC-CH2CH2-S-CF3). Optionally, the reaction time at 20°C-25°C can also be 5-6 hours, 6-7 hours, or 7-8 hours.

[0052] Specifically, the first thioether intermediate molecule in this embodiment simultaneously contains a cyano group, a thioether bond, and a trifluoromethyl functional group. The cyano group and the thioether bond are connected by an ethylene chain. Under oxidative conditions, the thioether bond can be converted to a sulfonyl group, while the ethylene chain, cyano group, and trifluoromethyl group remain stable under these oxidative conditions. Limiting the reaction conditions using 3-mercaptopropionitrile as a starting material enriches the selectivity of the synthesis of a series of additives. Optionally, the molar ratio of 3-mercaptopropionitrile:trifluoroethyl iodine:potassium carbonate in the mixed solution can also be 1:1.12:1.35, 1:1.15:1.40, or 1:1.18:1.45.

[0053] Furthermore, after obtaining the first sulfide intermediate 3-(trifluoromethylthio)propionitrile (NC-CH2CH2-S-CF3), the process also includes: 3-(trifluoromethylthio)propionitrile and dichloromethane were mixed and then an oxidant was added at 0°C-5°C to obtain a mixed solution, wherein the molar ratio of the first sulfide intermediate to the oxidant in the mixed solution was 1:(2.4~3.0). The mixed solution is heated to 20°C-25°C and reacted for 12-15 hours. The mixed solution after reaction is washed and dried to obtain the electrolyte additive, which is 3-(trifluoromethylsulfonyl)propionitrile.

[0054] Specifically, the oxidant is m-chloroperoxybenzoic acid, and the reaction formula for the formation of 3-(trifluoromethylthio)propionitrile from m-chloroperoxybenzoic acid is as follows: NC-CH2CH2-S-CF3+2m-CPBA→NC-CH2CH2-SO2-CF3+2m-CBA Understandably, adding the oxidant at low temperatures effectively controls the initial rate of the oxidation reaction, preventing excessively high local concentrations and concentrated heat release due to a single addition of the oxidant. This prevents side reactions such as over-oxidation of the thioether bond or breakage of the carbon-sulfur bond during oxidation. The thioether bond in the first thioether intermediate has lone pairs of electrons on two sulfur atoms. The oxidant can progressively oxidize the thioether bond to sulfoxides and sulfones. When the amount of oxidant is 2.4-3.0 times the molar amount of the first thioether intermediate, it ensures that the thioether bond is completely converted to a sulfonyl group, without remaining at the sulfoxide stage. The presence of the sulfonyl group intermediate leads to inconsistent functional groups in the final product, affecting the consistency of film formation of the additive at the electrode interface. The appropriate excess of oxidant provides sufficient oxidative equivalent for complete reaction, while this dosage range avoids over-oxidation of stable structures such as cyano groups or carbon-fluorine bonds in the molecule, ensuring the integrity of the product structure. Optionally, the molar ratio of the first thioether intermediate to the oxidant in the mixed solution can also be 1:2.5, 1:2.7, or 1:2.9.

[0055] Specifically, the mixed solution after adding the oxidant is heated to 20°C-25°C and reacted for 10-14 hours to ensure the oxidation reaction proceeds smoothly and avoid side reactions that may be caused by the oxidant under high-temperature conditions. Dichloromethane, as the reaction solvent, remains inert during the oxidation process and does not participate in the oxidation reaction, while simultaneously dissolving the first sulfide intermediate and the oxidant. After the reaction, residual oxidant and its reduction products are removed by washing, and moisture is removed by drying to obtain high-purity electrolyte additive 3-(trifluoromethanesulfonyl)propionitrile. Optionally, the reaction time at 20°C-25°C can also be 10-11 hours, 11-13 hours, or 13-15 hours.

[0056] It should be noted that in the electrolyte additive obtained in this embodiment, the cyano group and the sulfonyl group are connected by an ethylene chain, forming a cyanoethylsulfonyl structure. The ethylene linking chain increases the spatial distance between the cyano group and the sulfonyl group, giving the molecule higher flexibility and rotational freedom. This allows for adsorption and reaction in different molecular conformations and arrangements during film formation at the electrode interface. This structural feature helps to regulate the order and uniformity of the interfacial film. Simultaneously, this oxidation step achieves efficient conversion of the thioether bond to the sulfonyl group while fully preserving the functional structures of the cyano group and the trifluoromethyl group, resulting in a final product containing all three functional groups.

[0057] In another embodiment, the sulfonation reaction involves mixing a cyano-containing mercapto compound, 2-chloroethanesulfonyl chloride, dichloromethane, and an acid-binding agent, comprising: The cyano-containing mercapto compound is mercaptoacetonitrile, the organic solvent is dichloromethane, and the acid-binding agent is triethylamine; A first solution is formed by mixing mercaptoacetonitrile and dichloromethane. An acid-binding agent is added to the first solution to obtain a pre-solution. 2-Chloroethanesulfonyl chloride and dichloromethane are mixed in an inert gas atmosphere at a temperature of 0°C-5°C to form a second solution. The second solution is added dropwise to the first solution at a rate that maintains the temperature of the reaction solution not exceeding 5°C to obtain a mixed solution. The molar ratio of mercaptoacetonitrile:2-chloroethanesulfonyl chloride:triethylamine in the mixed solution is 1:(1.0~1.1):(1.1~1.2). The mixed solution was heated to 20°C-25°C and reacted for 4-5 hours. The mixed solution after the reaction was washed and dried to obtain the first sulfide intermediate, which was 2-(cyanomethylthio)ethanesulfonyl chloride (NC-CH2-S-CH2CH2-SO2-Cl).

[0058] Specifically, the reaction formula for the formation of 2-(cyanomethylthio)ethanesulfonyl chloride from mercaptoacetonitrile, 2-chloroethanesulfonyl chloride, and triethylamine is as follows: HS-CH2-CN+Cl-SO2-CH2CH2-Cl+Et3N→NC-CH2-S-CH2CH2-SO2-Cl+Et3N·HCl Understandably, by pre-mixing mercaptoacetonitrile with dichloromethane and adding an acid-binding agent to form a pre-solution, the acid-binding agent is uniformly dispersed in the system, which can neutralize the hydrogen chloride generated in the reaction at any time. Triethylamine, as an acid-binding agent, can be in excess relative to mercaptoacetonitrile, neutralizing all the hydrogen chloride generated in the reaction and any acidic substances produced by trace amounts of water in the reaction system, ensuring that the reaction system always maintains a weakly alkaline environment. Adding 2-chloroethanesulfonyl chloride separately in dichloromethane to form a second solution, using a dropwise method, allows for precise control of the introduction rate of the thiol-functionalized reagent. Slow dropwise addition at a reaction solution temperature not exceeding 5°C avoids excessively high local concentrations and concentrated release of reaction heat caused by a single addition, thereby effectively suppressing possible decomposition side reactions of 2-chloroethanesulfonyl chloride under acidic or high-temperature conditions. The low-temperature dropwise addition environment of 0°C-5°C further reduced the reaction rate in the initial stage, allowing the thioether bonds generated during the dropwise addition to form in an orderly manner. Simultaneously, the increased solubility of hydrogen chloride in dichloromethane under low-temperature conditions facilitated the timely capture of hydrogen chloride by the acid-binding agent, preventing acid accumulation from damaging the reactant and product structures. The molar ratio of mercaptoacetonitrile to 2-chloroethanesulfonyl chloride to triethylamine was limited to 1:(1.0~1.05):(1.1~1.2), with a slight excess of 2-chloroethanesulfonyl chloride relative to mercaptoacetonitrile. This ensured that all thiol groups in the mercaptoacetonitrile molecule participated in the coupling reaction, preventing unconverted mercaptoacetonitrile from remaining in the system due to insufficient reactant ratio. Residual mercaptoacetonitrile could be oxidized to disulfides and other byproducts in subsequent oxidation steps, increasing purification difficulty. After the acid-binding agent was added, the mixed solution was heated to 20°C-25°C for incubation to ensure complete sulfonation. After the reaction, the acid-binding agent salts, unreacted acid-binding agent, and residual water are removed sequentially by washing and drying to obtain a high-purity first thioether intermediate, 2-(cyanomethylthio)ethanesulfonyl chloride. This first thioether intermediate molecule simultaneously contains a cyano group, a thioether bond, and a trifluoromethyl functional group. The cyano group is located on a methylene group at one end of the molecule. The thioether bond formed by the sulfonation coupling of the trifluoromethyl group is separated from the cyano group by one methylene unit. The short-chain structure ensures that the distance between the cyano group and the sulfonyl group is compact after subsequent oxidation to a sulfonyl group, which is beneficial for forming a functionally synergistic thin-layer structure at the electrode interface. Optionally, the ratio of mercaptoacetonitrile:2-chloroethanesulfonyl chloride:triethylamine in the mixed solution can also be 1:1.02:1.13, 1:1.04:1.18, or 1:1.03:1.05. Optionally, the reaction time at 20°C-25°C can be 4-4.5 hours, 4.5-4.7 hours, or 4.7-5 hours.

[0059] Furthermore, the first thioether intermediate 2-(cyanomethylthio)ethanesulfonyl chloride (NC-CH2-S-CH2CH2-SO2-Cl) subsequently includes: A mixed solution was obtained by adding an oxidant to a mixture of 2-(cyanomethylthio)ethanesulfonyl chloride at 0°C-5°C, wherein the molar ratio of the first sulfide intermediate to the oxidant in the mixed solution was 1:(2.4~3.0). The mixed solution is heated to 20°C-25°C and reacted for 10-12 hours. The mixed solution after reaction is washed and dried to obtain a sulfonyl intermediate, which is 2-(cyanomethylsulfonyl)ethanesulfonyl chloride.

[0060] Specifically, the oxidant is m-chloroperoxybenzoic acid. The reaction formula for the formation of 2-(cyanomethylthio)ethanesulfonyl chloride (C4H6ClNO2S2) from m-chloroperoxybenzoic acid is as follows: NC-CH2-S-CH2CH2-SO2-Cl+m-CPBA→NC-CH2-SO2-CH2CH2-SO2-Cl+2m-CBA Understandably, adding the oxidant m-chloroperoxybenzoic acid at low temperatures can effectively control the initial rate of the oxidation reaction, avoiding excessively high local concentrations and concentrated heat release due to a single addition of the oxidant. This prevents side reactions such as over-oxidation of the thioether bond or carbon-sulfur bond breakage during the oxidation process. The thioether bond in the first thioether intermediate has lone pairs of electrons on two sulfur atoms. The oxidant can progressively oxidize the thioether bond to sulfoxides and sulfones. When the amount of oxidant is 2.4-3.0 times the molar amount of the first thioether intermediate, it can ensure that the thioether bond is completely converted to a sulfonyl group and does not remain at the sulfoxide stage. Optionally, the molar ratio of the first thioether intermediate to the oxidant in the mixed solution can also be 1:2.5, 1:2.7, or 1:2.9.

[0061] Specifically, the mixed solution after adding the oxidant is heated to 20°C-25°C and reacted for 10-12 hours to ensure the oxidation reaction proceeds smoothly. Dichloromethane, as the reaction solvent, remains inert during the oxidation process and does not participate in the oxidation reaction. After the reaction is complete, residual oxidant and its reduction products are removed by washing, and moisture is removed by drying to obtain the high-purity sulfonyl intermediate 2-(cyanomethylsulfonyl)ethanesulfonyl chloride. Optionally, the reaction time at 20°C-25°C can also be 10-10.5 hours, 10.5-11.5 hours, or 11.5-12 hours.

[0062] Specifically, in the sulfonyl intermediate molecule obtained in this embodiment, the original thioether bond is oxidized to a sulfonyl group, while the cyano and sulfonyl chloride groups in the molecule remain stable under oxidative conditions and do not participate in any side reactions. This sulfonyl intermediate contains three functional groups: cyano, sulfonyl, and sulfonyl chloride. The sulfonyl chloride group serves as the active site for the subsequent fluorination exchange reaction, capable of undergoing a chlorine-fluorine substitution reaction with the fluorinating agent to transform into a sulfonyl fluoride functional group, thereby ultimately obtaining an electrolyte additive containing cyano, sulfonyl, and sulfonyl fluoride.

[0063] Furthermore, the electrolyte additive is obtained by exchanging the sulfonyl intermediate with a fluorinating agent, including: Potassium fluoride and a polar solvent are provided. The sulfonyl intermediate and the polar solvent are mixed and then potassium fluoride is added to obtain a mixed solution, wherein the molar ratio of sulfonyl intermediate to potassium fluoride in the mixed solution is 1:(3.0~3.5). The mixed solution is heated to 60-65°C and reacted for 4-5 hours. The mixed solution after reaction is washed and dried to obtain the electrolyte additive, which is 2-(cyanomethylsulfonyl)ethanesulfonyl fluoride.

[0064] Specifically, the fluorinating agent is potassium fluoride. The reaction formula for the formation of 2-(cyanomethylsulfonyl)ethanesulfonyl chloride from potassium fluoride is as follows: NC-CH2-SO2-CH2CH2-SO2-Cl+KF→NC-CH2-SO2-CH2CH2-SO2F+KCl Understandably, potassium fluoride, as a fluorine source, possesses fluoride ions with strong nucleophilicity, enabling them to undergo nucleophilic substitution reactions with the sulfonyl chloride groups in the sulfonyl intermediate. The chlorine atom is replaced by the fluoride ion, forming a sulfonyl fluoride bond. The selection of a polar solvent effectively dissolves the sulfonyl intermediate and potassium fluoride, providing a homogeneous reaction environment and promoting effective collisions and reactions between fluoride ions and sulfonyl chloride groups. The amount of potassium fluoride used is 3.0-4.0 times the molar amount of the sulfonyl intermediate. This excess design ensures that all sulfonyl chloride groups in the sulfonyl intermediate participate in the fluoride exchange reaction, preventing unfluorinated intermediates from remaining in the product due to insufficient fluorine source. Unconverted sulfonyl chloride groups may hydrolyze in the electrolyte environment, producing acidic substances that affect electrolyte stability and battery performance. The reaction temperature is controlled at 60-65°C to promote the smooth progress of the fluorination reaction. Optionally, the molar ratio of sulfonyl intermediate to potassium fluoride can also be 1:3.5, 1:3.2, or 1:3.9. Optionally, the reaction time at 20°C-25°C can also be 4 hours-4.5 hours, 4.5 hours-4.7 hours, or 4.7 hours-5 hours.

[0065] Specifically, the cyano and sulfonyl groups in the sulfonyl intermediate remain stable under fluorination conditions and do not participate in the nucleophilic substitution reaction of fluoride ions. Due to the high bond energy and stability of the carbon-nitrogen triple bond in the cyano group, and the high bond energy and antioxidant capacity of the sulfur-oxygen double bond in the sulfonyl group, they do not break or transform under mild fluorination conditions, thus ensuring the complete retention of the cyano and sulfonyl groups in the final product. The conversion of the sulfonyl chloride group to the sulfonyl fluoride group endows the final product with different chemical properties. Compared with the sulfonyl chloride group, the sulfonyl fluoride group has a higher bond energy and lower reactivity, which enhances the chemical and storage stability of the final product in the electrolyte, making it less prone to hydrolysis or side reactions with other electrolyte components, thus extending the electrolyte's lifespan. After the reaction, excess potassium fluoride and the generated potassium chloride are removed by washing, and residual moisture and polar solvents are removed by drying to obtain the high-purity electrolyte additive 2-(cyanomethylsulfonyl)ethanesulfonyl fluoride.

[0066] Specifically, the final electrolyte additive contains three functional groups: cyano, sulfonyl, and sulfonyl fluoride. The cyano group plays an antioxidant role on the positive electrode surface and inhibits the dissolution of transition metals. The sulfonyl group provides a lithium ion conduction channel at the interface to reduce the interfacial impedance. The sulfonyl fluoride group participates in the reduction and decomposition at the negative electrode interface to generate an interfacial film rich in lithium fluoride to suppress side reactions.

[0067] To verify the performance of the electrolyte additive prepared by this method, the following experiments were conducted: Example 1: In an ice-water bath at 0℃-5℃, 0.1 mol of chloroacetonitrile was dissolved in anhydrous ethanol, and 0.11 mol of sodium hydrosulfide was added in portions with stirring. After the addition was complete, the ice-water bath was removed, and the temperature was raised to 35℃-40℃ for 2 hours. After filtration to remove salt, the fraction collected under reduced pressure at 80℃-85℃ / 15mmHg was obtained as mercaptoacetonitrile. 0.05 mol of mercaptoacetonitrile was dissolved in anhydrous tetrahydrofuran, and 0.06 mol of anhydrous potassium carbonate was added. Under nitrogen protection at 0℃-5℃, 0.05 mol of trifluoroethyl iodide dissolved in tetrahydrofuran was slowly added dropwise to the above solution. After the addition was complete, the temperature was raised to room temperature and stirred for 6 hours. After washing, drying, and purification by silica gel column chromatography, a colorless oily liquid intermediate NC-CH2-S-CH2-CF3 was obtained. 0.035 mol of the above thioether intermediate was dissolved in diethyl chloroacetonitrile... In chloromethane, 0.105 mol of m-chloroperoxybenzoic acid was added in portions at 0℃-5℃. After the addition was complete, the mixture was allowed to rise to room temperature and reacted for 12 hours. The product was washed, dried, and purified by silica gel column chromatography to obtain a white solid NC-CH2-SO2-CH2-CF3 (additive-1). Additive-1 was added at a concentration of 2.0 wt% to a 1.0 M LiPF6 EC / EMC volume ratio basic electrolyte. The positive electrode was NCM811 with an isal capacity of 4.5 mAh / cm², and the negative electrode was artificial graphite with an isal capacity of 4.8 mAh / cm². The cells were stacked to form a 3 Ah pouch battery with an electrolyte injection volume of 3.5 g / Ah. The battery was charged at a constant current of 0.1 C to 4.65 V and then constant at 2.1 V for 15 min and 0.7 V for 10 min to complete the formation and obtain pouch battery S1.

[0068] Example 2: Following the method of Example 1, 3-mercaptopropionitrile was used instead of mercaptoacetonitrile. Specifically, 0.1 mol of 3-chloropropionitrile was dissolved in anhydrous ethanol in an ice-water bath at 0-5°C, and 0.11 mol of sodium hydrosulfide was added. The mixture was heated to 35-40°C and reacted for 2.5 hours. After filtration, the fraction at 95-100°C / 15 mmHg was collected by vacuum distillation to obtain 3-mercaptopropionitrile. 0.05 mol of 3-mercaptopropionitrile was dissolved in anhydrous acetonitrile, and 0.065 mol of anhydrous potassium carbonate was added. Under nitrogen protection at 0-5°C, 0.055 mol of... l of trifluoromethyl iodine was added to the above solution, and the mixture was stirred at room temperature for 7 hours. After post-treatment and column chromatography purification, NC-CH2CH2-S-CF3 intermediate was obtained. 0.035 mol of the intermediate was oxidized with 0.105 mol of m-chloroperoxybenzoic acid at 0℃-5℃ for 12 hours. After post-treatment purification, NC-CH2CH2-SO2-CF3 (additive-2) was obtained. Additive-2 was added at a concentration of 1.5 wt% to the same electrolyte and battery system as in Example 1 to complete the formation and obtain the soft-pack battery S2.

[0069] Example 3: 0.05 mol of mercaptoacetonitrile was dissolved in dichloromethane, and 0.055 mol of triethylamine was added. Under nitrogen protection at 0℃-5℃, a dichloromethane solution of 0.05 mol of 2-chloroethanesulfonyl chloride was slowly added dropwise. After the addition was complete, the mixture was brought to room temperature and stirred for 5 hours. Post-treatment yielded the intermediate NC-CH2-S-CH2CH2-SO2-Cl. 0.035 mol of this intermediate was oxidized with 0.105 mol of m-chloroperoxybenzoic acid at 0℃-5℃ for 12 hours to obtain NC-CH2-S... O2-CH2CH2-SO2-Cl sulfonyl intermediate; 0.025 mol of the sulfonyl intermediate was dissolved in DMF and 0.080 mol of anhydrous potassium fluoride was added. The mixture was stirred at 65 °C for 4 hours. After extraction, washing, drying and column chromatography purification, NC-CH2-SO2-CH2CH2-SO2-F (additive-3) was obtained. Additive-3 was added at a concentration of 2.0 wt% to the same electrolyte and battery system as in Example 1 to complete the formation and obtain the pouch battery S3.

[0070] Comparative Example 1: Using only 1.0M LiPF6 as the base electrolyte with an EC / EMC volume ratio of 1:1, without adding any film-forming additives, the positive electrode is NCM811 with an areal capacity of 4.5 mAh / cm², and the negative electrode is artificial graphite with an areal capacity of 4.8 mAh / cm². The cells are stacked to form a 3Ah pouch battery with an electrolyte injection amount of 3.5 g / Ah. The pouch battery D1 is obtained by processing the cells using the same formation procedure as in Example 1.

[0071] Comparative Example 2: According to the synthetic additive CH3-SO2-CH2CH2CH2-CF3, whose structure is R¹ is methyl, R² is propylene and there is no cyano group, this control additive was added at a concentration of 2.0 wt% to a 1.0 M LiPF6 EC / EMC volume ratio 1:1 basic electrolyte. The positive electrode is NCM811 with an isal capacity of 4.5 mAh / cm², and the negative electrode is artificial graphite with an isal capacity of 4.8 mAh / cm². The cells were stacked to form a 3 Ah soft-pack battery with an electrolyte injection amount of 3.5 g / Ah. The same formation procedure as in Example 1 was used to complete the formation and obtain the soft-pack battery D2.

[0072] Comparative Example 3: An additive, NC-CH2CH2-O-CF3, was prepared. This molecule contains cyano and fluorine functional groups but no sulfonyl groups. This control additive was added at a concentration of 2.0 wt% to a 1.0 M LiPF6 EC / EMC volume ratio 1:1 basic electrolyte. The positive electrode was NCM811 with an isal capacity of 4.5 mAh / cm², and the negative electrode was artificial graphite with an isal capacity of 4.8 mAh / cm². The electrodes were stacked to form a 3 Ah pouch battery with an electrolyte injection amount of 3.5 g / Ah. The battery was processed using the same formation procedure as in Example 1 to complete the formation and obtain pouch battery D3.

[0073] Performance Testing Methodology Description The following electrochemical performance tests were conducted on the pouch cells S1, S2, and S3 from the above experimental examples, as well as the pouch cells D1, D2, and D3 from the comparative examples: 4.65V Cycle Performance: The formed pouch cell was placed in a 25°C±2°C charge-discharge test system, charged at a constant current of 1C to 4.65V, then switched to constant voltage charging until the current dropped to 0.05C, and then discharged at a constant current of 1C to 2.8V. This cycle was repeated. The discharge capacity of the 1st and 500th cycles was recorded. Capacity retention rate = (500th discharge capacity / 1st discharge capacity) × 100%.

[0074] Room temperature rate performance: At 25°C, the pouch cell was first fully charged at a constant current and constant voltage of 0.33C, and then discharged to 2.8V at constant currents of 0.33C, 1C, 3C, 5C, and 10C, respectively. The discharge capacity at each rate was recorded. 5C discharge retention rate = (5C discharge capacity / 0.33C discharge capacity) × 100%. Before testing, all cells underwent three standard capacity calibrations at 0.33C.

[0075] Interfacial impedance: The pouch cell was charged to 50% state of charge and left to stand at a constant temperature of 25°C for 2 hours. AC impedance spectroscopy was performed using an electrochemical workstation, with a frequency range of 100kHz to 10mHz and an amplitude of 5mV. An equivalent circuit model was used for fitting, and the intersection of the semicircle in the mid-frequency region and the real axis was taken as the interfacial impedance.

[0076] Low-temperature discharge performance: The pouch battery was fully charged at 0.5C at 25°C, then placed in a -20°C constant temperature chamber for 12 hours until the battery temperature reached equilibrium. After that, it was discharged at a constant current of 0.5C to 2.8V, and the low-temperature discharge capacity was recorded. Low-temperature discharge retention rate = (0.5C discharge capacity at -20°C / 0.5C discharge capacity at 25°C) × 100%.

[0077] Table 1: Experimental Data Table

[0078] As shown in Table 1, the electrolyte additive with three functional groups (cyano, sulfonyl, and fluorine) provided by this invention exhibits significantly superior overall performance compared to existing technologies in high-voltage, high-power lithium-ion batteries. The synergistic effect of the three functional groups was fully verified through systematic comparative experiments. Comparative Example 2, lacking cyano groups but retaining sulfonyl and fluorine functional groups, showed a 16.4 percentage point decrease in its 500-cycle retention rate compared to Example 1, and a 62.5% increase in interfacial impedance. This demonstrates that cyano groups play an irreplaceable role in densifying and reinforcing the positive electrode electrolyte interfacial film and enhancing its antioxidant capacity at high potentials. Comparative Example 3, lacking sulfonyl groups but retaining cyano and fluorine functional groups, experienced severe rupture of its positive electrode electrolyte interfacial film after 300 cycles. This proves that the flexible ion-conducting framework constructed by sulfonyl groups is the fundamental support for maintaining the structural integrity and low-impedance ion conduction of the positive electrode electrolyte interfacial film. When all three are present, the positive electrode CEI exhibits a gradient structure with an outer layer rich in cyano groups (C≡N bonds) to resist high-voltage oxidation and corrosion, and an inner layer rich in SO bonds to ensure rapid lithium-ion conduction. The negative electrode electrolyte interface film contains up to 78 wt% lithium fluoride. Simultaneously, the fluorinated functional groups effectively lower the lithium-ion desolvation energy barrier, resulting in Example 1 achieving a cycle retention rate of 87.6% after 500 cycles at a 4.65V cutoff voltage, a 5C rate discharge retention rate of 91.2%, and an interface impedance as low as 32 Ω·cm². Its overall performance is far superior to the control example without additives and any control example lacking a specific functional group. Therefore, the cyano group provides a high-voltage antioxidant barrier, the sulfonyl group provides a flexible ion-conducting framework, and the fluorinated functional group provides negative electrode interface protection and solvation regulation. These three functional groups are functionally complementary and synergistic, allowing a single molecule to simultaneously meet the requirements of high voltage stability, high rate performance, and wide temperature range adaptability. This solves the technical challenge of existing bifunctional additives and multi-component compounding schemes, which struggle to simultaneously achieve high voltage stability and high rate performance.

[0079] The second embodiment of the present invention also provides an electrolyte additive for use in lithium-ion batteries. The electrolyte additive is prepared based on the above-described method for preparing electrolyte additives. The electrolyte additive is (2,2,2-trifluoroethyl)sulfonyl acetonitrile, 3-(trifluoromethylsulfonyl)propionitrile, or 2-(cyanomethylsulfonyl)ethanesulfonyl fluoride.

[0080] It should be noted that the electrolyte additive in this embodiment is directly added to the electrolyte of the lithium-ion battery. During the first charge of the battery, the cyano, sulfonyl, and fluorinated functional groups in its molecule undergo electrochemical reactions at different potentials on the positive or negative electrode surfaces, forming an interfacial protective layer. Understandably, this embodiment uses a cyano-containing haloalkane as a starting material, introduces a cyano functional group through nucleophilic substitution, then forms a thioether bond through sulfonation coupling, converts the thioether bond to a sulfonyl group through oxidation, and selectively obtains trifluoromethanesulfonyl products directly or sulfonyl fluoride products through fluorination exchange, depending on the type of mercaptofunctionalizing reagent. This preparation method ensures the introduction of cyano, sulfonyl, and fluorinated functional groups into the product molecule, with the three functional groups covalently linked intramolecularly to form a compact and functionally complementary small organic molecule. In trifluoromethanesulfonyl acetonitrile, the cyano group and sulfonyl group are linked by a methylene group; in trifluoromethanesulfonyl propionitrile, the cyano group and sulfonyl group are linked by an ethylene group; and in sulfonyl fluoride cyanosulfonate, the cyano group is linked to the sulfonyl fluoride group via a sulfonyl group. These three structures correspond to electrolyte additives with different chain lengths and combinations of fluorinated functional groups. When applied to lithium-ion battery electrolytes, the cyano, sulfonyl, and fluorinated functional groups in the electrolyte additive molecule function at different potentials and on different electrode surfaces during battery charging and discharging. The cyano group has a high oxidation potential and can preferentially adsorb on the positive electrode surface, undergoing oxidative polymerization under high voltage conditions to form an interfacial protective layer rich in carbon-nitrogen triple bonds. This protective layer has a dense structure and high antioxidant capacity, effectively inhibiting direct contact and oxidative decomposition of electrolyte components on the positive electrode surface. Simultaneously, the lone pair electrons of the cyano group can coordinate with transition metal ions dissolved from the positive electrode, slowing down the catalytic decomposition of the electrolyte by transition metal ions and their damage to the negative electrode interface. During charging, the sulfonyl group participates in oxidative polymerization on the positive electrode surface, forming an interfacial film framework containing sulfur-oxygen bonds. This framework exhibits good lithium-ion conductivity, providing ion transport channels at the positive electrode interface and reducing the impedance of lithium ions crossing the interfacial film. This avoids the obstruction of lithium-ion conduction caused by excessive density of a single cyano film layer. Fluorinated functional groups undergo a reductive decomposition reaction on the negative electrode surface, generating a solid electrolyte interfacial film rich in lithium fluoride. Lithium fluoride possesses high mechanical strength and a wide electrochemical window, effectively suppressing side reactions between the negative electrode and the electrolyte. Simultaneously, the strong electronegativity of the fluorinated functional groups helps regulate the solvation sheath structure of lithium ions in the electrolyte, reducing the energy barrier that lithium ions need to overcome for desolvation, making it easier for lithium ions to cross the interface and enter the electrode material.

[0081] Furthermore, the electrolyte additive of the present invention simultaneously contains three types of functional groups: cyano, sulfonyl, and fluorine-containing functional groups, wherein the fluorine-containing functional group can be trifluoromethyl or sulfonyl fluoride. During lithium-ion battery charging, the sulfonyl group can form a flexible interfacial framework containing sulfur-oxygen bonds, exhibiting good lithium-ion conductivity. As the voltage further increases, the cyano group further oxidizes and polymerizes on the positive electrode surface, crosslinking on the sulfonyl framework to form a dense protective layer rich in carbon-nitrogen triple bonds. The sulfonyl group provides ion conduction channels and a flexible substrate, while the cyano group provides an antioxidant barrier and mechanical strength, constructing a gradient positive electrode interfacial film with an inner flexible ion-conducting layer and an outer dense antioxidant layer. Simultaneously, the fluorine-containing functional group is reduced and decomposed on the negative electrode surface, generating a solid electrolyte interfacial film rich in lithium fluoride. This film has high mechanical strength and a wide electrochemical window, effectively suppressing side reactions between the negative electrode and the electrolyte; at the same time, the high electronegativity of the fluorine-containing functional group helps to reduce the lithium-ion desolvation energy barrier and improve the charge transfer efficiency at the interface. The three functional groups work in an orderly and synergistic manner in the electrochemical reaction, enabling the positive electrode to obtain an interface layer with both anti-oxidation and ion conduction functions, and the negative electrode to obtain a stable and low-impedance protective layer. This simultaneously improves the battery's cycle stability at high voltage and its discharge capability at high rate, solving the problem that existing electrolyte additives cannot achieve both high-voltage stability and high-rate performance.

[0082] A third embodiment of the present invention also provides a battery, comprising a positive electrode, an electrolyte layer and a negative electrode stacked together, wherein the electrolyte layer comprises electrolyte additives as described above.

[0083] The battery provided by this invention has an electrolyte layer containing the aforementioned trifunctional electrolyte additives, which can synergistically construct a gradient-distributed and functionally complementary interface protective film on the positive and negative electrode surfaces. The cyano group enhances the high-voltage oxidation resistance, the sulfonyl group provides a flexible ion conduction channel, and the fluorinated alkyl group forms a dense and stable fluorine-rich interface on the negative electrode. This effectively reduces interface impedance, suppresses side reactions, significantly improves the cycle stability, rate performance, and safety of the battery under high voltage and high rate conditions, and extends the battery's service life.

[0084] The fourth embodiment of the present invention also provides an electronic device, including a device body and the battery described above, wherein the solid-state battery is disposed within the device body.

[0085] The electronic device provided by this invention uses the aforementioned high-performance battery. Thanks to the multiple synergistic protection mechanisms of the electrolyte additive, the device can maintain a stable and reliable power supply under harsh operating conditions such as high-power fast charging, wide temperature range, and long-term cycling, thus meeting the dual requirements of battery life and safety.

[0086] In this invention, the electronic device may include, but is not limited to, portable consumer electronic devices, smart mobile terminals, electric vehicles, energy storage systems, or wearable devices. For example, the electronic device may be a smartphone, tablet computer, laptop computer, smartwatch, wireless headset, electric bicycle, electric motorcycle, electric vehicle, hybrid vehicle, drone, portable energy storage power supply, home energy storage system, or base station backup power supply.

[0087] The preparation method of an electrolyte additive and the electrolyte additive disclosed in the embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention. Any modifications, equivalent substitutions and improvements made within the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an electrolyte additive, characterized in that: The preparation method of the electrolyte additive includes the following steps: A cyano-containing haloalkane and sodium hydrosulfide are provided. The cyano-containing haloalkane is subjected to a nucleophilic substitution reaction with sodium hydrosulfide to obtain a cyano-containing mercapto compound. A thiol-functionalized reagent is provided, and the cyano-containing thiol compound is reacted with the thiol-functionalized reagent to obtain an intermediate containing a thioether bond; The intermediate containing the thioether bond is oxidized with an oxidizing agent to convert the thioether bond into a sulfonyl group, thereby obtaining a sulfonyl intermediate. Choose the type of thiol-functionalized reagent; If the thiol-functionalizing agent is trifluoroethyl iodide or trifluoromethyl iodide, the trifluoromethyl group in the trifluoroethyl iodide or trifluoromethyl iodide is introduced through a nucleophilic substitution reaction, and after oxidation, a sulfonyl intermediate is obtained. The sulfonyl intermediate is an electrolyte additive comprising cyano, sulfonyl, and trifluoromethyl functional groups; or If the thiol functionalizing agent is 2-chloroethanesulfonyl chloride, the sulfonyl chloride group of 2-chloroethanesulfonyl chloride is introduced into the sulfonyl intermediate through a sulfonylation reaction to provide a fluorinating agent. The sulfonyl intermediate and the fluorinating agent react to obtain a fluorinated product, in which the chlorine atom is replaced by a fluorine atom to obtain a sulfonyl fluoride group. The fluorinated product is an electrolyte additive that includes cyano, sulfonyl, and sulfonyl fluoride functional groups.

2. The method for preparing the electrolyte additive as described in claim 1, characterized in that: The specific components after providing the thiol-functionalized reagent include: A sulfonating solvent, an organic solvent, and an acid-binding agent are provided. The sulfonating solvent, the organic solvent, and the acid-binding agent are mixed to obtain a mercapto-functionalized reagent. If the thiol functionalizing agent is trifluoroethyl iodide or trifluoromethyl iodide, a nucleophilic substitution reaction is carried out by mixing trifluoroethyl iodide or trifluoromethyl iodide, a cyano-containing thiol compound, an organic solvent, and an acid-binding agent. The cyano-containing thiol compound contains a thiol group, and the trifluoroethyl iodide or trifluoromethyl iodide contains an iodoalkyl group. The thiol group is coupled to the iodoalkyl group of the trifluoroethyl iodide through a nucleophilic substitution reaction to form a thioether bond, yielding a first thioether intermediate. An oxidizing agent is provided, and the first thioether intermediate is mixed with the organic solvent and then subjected to an oxidation reaction with the oxidizing agent to oxidize the thioether bond to a sulfonyl group to obtain an electrolyte additive. or, If the sulfonation solvent is 2-chloroethanesulfonyl chloride, a sulfonation reaction is carried out by mixing a cyano-containing thiol compound, 2-chloroethanesulfonyl chloride, an organic solvent, and an acid-binding agent. The cyano-containing thiol compound contains a thiol group, and the 2-chloroethanesulfonyl chloride contains a sulfonyl chloride group. The sulfonation reaction couples the thiol group with the sulfonyl chloride group to form a thioether bond, yielding a second thioether intermediate. An oxidizing agent is provided, and the second thioether intermediate is mixed with the organic solvent and then subjected to an oxidation reaction to oxidize the thioether bond to a sulfonyl group, yielding a sulfonyl intermediate. A fluorinating agent is provided, and the sulfonyl intermediate is subjected to an exchange reaction with the fluorinating agent to obtain an electrolyte additive.

3. The method for preparing the electrolyte additive as described in claim 2, characterized in that: Nucleophilic substitution reactions of cyano-containing haloalkanes with sodium hydrosulfide yield cyano-containing mercapto compounds, including: An alcohol solvent is provided. A cyano-containing haloalkane and an alcohol solvent are mixed at 0°C-5°C, and then sodium hydrosulfide is added to obtain a mixed solution, wherein the molar ratio of the cyano-containing haloalkane to sodium hydrosulfide in the mixed solution is 1:(1.1-1.2). The mixed solution was heated to 35°C-40°C and reacted for 1.5-2.0 hours. The resulting mixed solution was then filtered and distilled to obtain a cyano-containing mercapto compound. If the cyano-containing haloalkane is chloroacetonitrile, the distillation process involves collecting the distillate at a temperature between 80°C and 85°C under a vacuum of 10 mmHg-20 mmHg to obtain a cyano-containing mercapto compound, wherein the cyano-containing mercapto compound is mercaptoacetonitrile. If the cyano-containing haloalkane is 3-chloropropionitrile, the distillation process involves collecting the distillate at a temperature between 95°C and 100°C under a vacuum of 10 mmHg to 20 mmHg to obtain a cyano-containing mercapto compound, wherein the cyano-containing mercapto compound is 3-mercaptopropionitrile.

4. The method for preparing the electrolyte additive as described in claim 2, characterized in that: The cyano-containing haloalkane is chloroacetonitrile or 3-chloropropionitrile; the organic solvent includes dichloromethane, anhydrous acetonitrile, or tetrahydrofuran; and / or, the oxidant includes any one or a combination of several of m-chloroperoxybenzoic acid, hydrogen peroxide, potassium persulfate, potassium permanganate, sodium hypochlorite, sodium chlorite, dimethyldioxyethylene, or sodium perborate; and / or, the acid-binding agent includes any one or a combination of several of triethylamine, pyridine, N,N-diisopropylethylamine, 4-dimethylaminopyridine, N-methylmorpholine, 2,6-dimethylpyridine, or potassium carbonate.

5. The method for preparing the electrolyte additive as described in claim 3, characterized in that: If the thiol-functionalizing agent is trifluoroethyl iodine: The cyano-containing mercapto compound is mercaptoacetonitrile, the organic solvent is tetrahydrofuran, and the acid-binding agent is anhydrous potassium carbonate; A first solution is formed by mixing mercaptoacetonitrile and tetrahydrofuran. Anhydrous potassium carbonate is added to the first solution to obtain a pre-solution. Trifluoroethyl iodide and tetrahydrofuran are mixed under an inert gas atmosphere at a temperature of 0°C-5°C to form a second solution. The second solution is added dropwise to the first solution to obtain a mixed solution. The molar ratio of mercaptoacetonitrile:trifluoroethyl iodide:anhydrous potassium carbonate in the mixed solution is 1:(1.0~1.1):(1.1~1.3). The mixed solution was heated to 20°C-25°C and reacted for 5-8 hours. The mixed solution after the reaction was washed and dried to obtain the first sulfide intermediate, which was 2,2,2-trifluoroethyl thioacetonitrile. 2,2,2-trifluoroethyl thioacetonitrile and dichloromethane were mixed and then an oxidant was added at 0°C-5°C to obtain a mixed solution, wherein the molar ratio of the first thioether intermediate to the oxidant in the mixed solution was 1:(2.4~3.0). The mixed solution is heated to 20°C-25°C and reacted for 10-14 hours. The mixed solution after reaction is washed and dried to obtain an electrolyte additive, which is (2,2,2-trifluoroethyl)sulfonyl acetonitrile.

6. The method for preparing the electrolyte additive as described in claim 3, characterized in that: The thiol-functionalizing agent is trifluoromethyl iodine: The cyano-containing mercapto compound is 3-mercaptopropionitrile, the organic solvent is anhydrous acetonitrile, and the acid-binding agent is anhydrous potassium carbonate; 3-Mercaptopropionitrile and anhydrous acetonitrile are mixed to form a first solution. Anhydrous potassium carbonate is added to the first solution to obtain a pre-solution. Trifluoromethyl iodine is passed through the pre-solution under an inert gas atmosphere at a temperature of 0°C-5°C to obtain a mixed solution. The molar ratio of 3-mercaptopropionitrile:trifluoromethyl iodine:anhydrous potassium carbonate in the mixed solution is 1:(1.1~1.2):(1.3~1.5). The mixed solution was heated to 20°C-25°C and reacted for 6-8 hours. The mixed solution after the reaction was washed and dried to obtain the first sulfide intermediate, which was 3-(trifluoromethylthio)propionitrile. 3-(trifluoromethylthio)propionitrile and dichloromethane were mixed and then an oxidant was added at 0°C-5°C to obtain a mixed solution, wherein the molar ratio of the first sulfide intermediate to the oxidant in the mixed solution was 1:(2.4~3.0). The mixed solution is heated to 20°C-25°C and reacted for 12-15 hours. The mixed solution after reaction is washed and dried to obtain the electrolyte additive, which is 3-(trifluoromethylsulfonyl)propionitrile.

7. The method for preparing the electrolyte additive as described in claim 3, characterized in that: If the sulfonating solvent is 2-chloroethanesulfonyl chloride: The cyano-containing mercapto compound is mercaptoacetonitrile, the organic solvent is dichloromethane, and the acid-binding agent is triethylamine; A first solution is formed by mixing mercaptoacetonitrile and dichloromethane. An acid-binding agent is added to the first solution to obtain a pre-solution. 2-Chloroethanesulfonyl chloride and dichloromethane are mixed in an inert gas atmosphere at a temperature of 0°C-5°C to form a second solution. The second solution is added dropwise to the first solution at a rate that maintains the temperature of the reaction solution not exceeding 5°C to obtain a mixed solution. The molar ratio of mercaptoacetonitrile:2-chloroethanesulfonyl chloride:triethylamine in the mixed solution is 1:(1.0~1.1):(1.1~1.2). The mixed solution was heated to 20°C-25°C and reacted for 4-5 hours. The mixed solution after the reaction was washed and dried to obtain the first sulfide intermediate, which was 2-(cyanomethylthio)ethanesulfonyl chloride. 2-(cyanomethylthio)ethanesulfonyl chloride (NC-CH2-S-CH2CH2-SO2-Cl) and dichloromethane were mixed and then an oxidant was added at 0°C-5°C to obtain a mixed solution, wherein the molar ratio of the first sulfide intermediate to the oxidant in the mixed solution was 1:(2.4~3.0). The mixed solution was heated to 20°C-25°C and reacted for 10-12 hours. The mixed solution after reaction was washed and dried to obtain a sulfonyl intermediate, which was 2-(cyanomethylsulfonyl)ethanesulfonyl chloride. Potassium fluoride and a polar solvent are provided. The sulfonyl intermediate and the polar solvent are mixed and then potassium fluoride is added to obtain a mixed solution, wherein the molar ratio of sulfonyl intermediate to potassium fluoride in the mixed solution is 1:(3.0~3.5). The mixed solution is heated to 60-65°C and reacted for 4-5 hours. The mixed solution after reaction is washed and dried to obtain the electrolyte additive, which is 2-(cyanomethylsulfonyl)ethanesulfonyl fluoride.

8. An electrolyte additive, characterized in that: The electrolyte additive is prepared based on the preparation method of the electrolyte additive as described in any one of claims 1-7, wherein the electrolyte additive is (2,2,2-trifluoroethyl)sulfonyl acetonitrile, 3-(trifluoromethylsulfonyl)propionitrile, or 2-(cyanomethylsulfonyl)ethanesulfonyl fluoride.

9. A battery, characterized in that: It includes a positive electrode, an electrolyte layer, and a negative electrode stacked together, wherein the electrolyte layer includes the electrolyte additive as described in claim 8.

10. An electronic device, characterized in that: It includes a device body and a battery as described in claim 9, wherein the solid-state battery is disposed within the device body.

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