Sulfonate compound as well as preparation method and application thereof

Abstract

The invention discloses a sulfonate compound as well as a preparation method and application thereof. The sulfonate compound has the following structural formula, x is selected from any one of halogen, alkyl, alkenyl, alkynyl, cyano and aryl; the invention has unique and novel annular structure, is very suitable for being used as an additive of the electrolyte of the lithium ion battery, and is especially suitable for being used in the electrolyte of the ternary system lithium ion battery, and the preparation method provided by the invention has the advantages of mild reaction conditions and high product purity and yield.

Description

[0001] This invention belongs to the field of chemical synthesis, specifically relating to a sulfonate compound, its preparation method and application, which is very suitable as an additive for lithium-ion battery electrolytes. Background Technology

[0002] Since their commercialization, lithium-ion batteries have been widely used in portable electronic devices, electric vehicles, and energy storage systems. The electrolyte, as a crucial component of lithium-ion batteries, plays a vital role in ion transport and charge conduction between the positive and negative electrodes. An ideal lithium-ion battery electrolyte needs to meet requirements such as high ionic conductivity, high chemical and thermal stability, a wide electrochemical window, good compatibility with other battery components, and safety, non-toxicity, and non-polluting properties, thereby improving the stability of the positive electrode material and extending the battery's cycle life.

[0003] However, existing lithium-ion batteries generally suffer from poor thermal stability and cycle life. Therefore, the applicant seeks technical solutions to improve these issues. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a sulfonate compound, its preparation method and application, which has a unique and novel cyclic structure and is very suitable for use as an additive in lithium-ion battery electrolytes, especially in ternary lithium-ion battery electrolytes. Moreover, the proposed preparation method has mild reaction conditions and high product purity and yield.

[0005] The technical solution adopted in this invention is as follows: A sulfonate compound having the following structural formula: X is selected from any one of halogen, alkyl, alkenyl, alkynyl, cyano, and aryl.

[0006] Preferably, the halogen is any one of fluorine, chlorine, bromine, and iodine; The alkyl group is either substituted or unsubstituted C1-C. 10 alkyl; The alkenyl group is a substituted, unsubstituted, or heteroatom-containing C2-C group. 10 alkenyl; The alkynyl group is a substituted, unsubstituted, or heteroatom-containing C2-C group. 10 alkynyl group; The cyano group is a substituted, unsubstituted, or heteroatom-containing C2-C group. 10 Cyano; The aryl group is an independent aryl group, or a combination of aryl and alkyl groups, or a combination of aryl and heteroatom groups.

[0007] Preferably, the alkyl group is selected from any one of methyl-CH3, ethyl-C2H5, n-propyl-CH2CH2CH3, isopropyl-CH(CH3)2, n-butyl-CH2CH2CH2CH3, and tert-butyl-C(CH3)3; the alkenyl group is selected from any one of vinyl-CH=CH2, propenyl-CH2CH=CH2, and butenyl-CH2CH2CH=CH2; the alkynyl group is selected from ethynyl-C≡CH or propynyl-CH2C≡CH; the cyano group is selected from acetonitrile-CH2-C≡N or propionitrile-CH2CH2-C≡N; and the aryl group is selected from any one of phenyl, p-tolyl, and naphthyl.

[0008] Preferably, the sulfonate compound comprises the following structure: , , , , , Any one or a mixture of several of them.

[0009] Preferably, a method for preparing the sulfonate compound according to the above-described method involves using methyl disulfonic acid or its derivative as a raw material, adding an acid-binding agent dropwise to form a suspension in an organic solvent environment, then adding a ligand corresponding to the raw material dropwise to react, and continuing the reaction at a constant temperature for 2-10 hours after the addition is completed to obtain the reaction product; the reaction product is then post-treated to obtain the sulfonate compound; the temperature range of the reaction is controlled between -10 and 100°C.

[0010] Preferably, the derivative of methyl disulfonic acid is selected from any one or a mixture of several of methyl disulfonic acid chloride, methyl disulfonic acid bromide, and methyl disulfonic acid fluoride; and / or the acid-binding agent is pyridine or triethylamine; and / or the ligand is one of alkyl alcohol, alkynyl alcohol, alkenyl alcohol, cyano alcohol, aryl alcohol, and haloalcohol; and / or the reaction solvent is any one or a mixture of several of ether organic solvents, carbonate organic solvents, carboxylic acid ester organic solvents, chlorinated hydrocarbons, alkanes, and nitrile organic solvents.

[0011] Preferably, the molar ratio of the ligand to methyl disulfonic acid or its derivative is 1-3 times; and / or the molar ratio of the acid-binding agent to methyl disulfonic acid or its derivative is 1-3 times; and / or the amount of organic solvent added is 4-12 times the weight of methyl disulfonic acid or its derivative.

[0012] Preferably, according to the application of the sulfonate compound described above, the sulfonate compound is added to the lithium-ion battery electrolyte.

[0013] Preferably, the lithium-ion battery electrolyte comprises an organic solvent system, a lithium salt system, and an additive system; the organic solvent system comprises at least one cyclic carbonate and at least one chain carbonate; and the additive system comprises the sulfonate compound.

[0014] Preferably, the sulfonate compound accounts for 0.5-5% of the mass fraction of the lithium-ion battery electrolyte; more preferably, 1-4%; and the chain carbonate accounts for 75-92% of the mass fraction of the lithium-ion battery electrolyte, more preferably 80-90%.

[0015] The sulfonate compounds provided in this application have a unique and novel cyclic structure, making them highly suitable as additives for lithium-ion battery electrolytes, especially for ternary lithium-ion batteries (particularly NCM622 or NCM811). This has significant theoretical and practical value. This application also specifically proposes a method for preparing sulfonate compounds, using methyl disulfonic acid or its derivatives as raw materials to synthesize a ligand with a target fragment in an acid-binding environment. The reaction product is then post-processed (separation, purification, etc.) to obtain the target product. The reaction conditions are mild, and the product purity and yield are high. Detailed Implementation

[0016] This embodiment presents a sulfonate compound having the following structural formula: X is selected from any one of halogen, alkyl, alkenyl, alkynyl, cyano, and aryl.

[0017] Preferably, in this embodiment, the halogen is any one of fluorine, chlorine, bromine, and iodine; the alkyl group is a substituted or unsubstituted C1-C group. 10 Alkyl; alkenyl is a substituted, unsubstituted or heteroatom-containing C2-C group. 10 Alkenyl; ynyl is a C2-C group that is substituted, unsubstituted, or contains heteroatoms. 10 The alkynyl group and cyano group are substituted, unsubstituted, or contain heteroatoms in the C2-C group. 10 Cyanoyl; aryl is an independent aryl group, or a combination of aryl and alkyl, or aryl and heteroatom.

[0018] Preferably, in this embodiment, the alkyl group is selected from any one of methyl-CH3, ethyl-C2H5, n-propyl-CH2CH2CH3, isopropyl-CH(CH3)2, n-butyl-CH2CH2CH2CH3, and tert-butyl-C(CH3)3; the alkenyl group is selected from any one of vinyl-CH=CH2, propenyl-CH2CH=CH2, and butenyl-CH2CH2CH=CH2; the alkynyl group is selected from ethynyl-C≡CH or propynyl-CH2C≡CH; the cyano group is selected from acetonitrile-CH2-C≡N or propionitrile-CH2CH2-C≡N; and the aryl group is selected from any one of phenyl, p-tolyl, and naphthyl.

[0019] Preferably, in this embodiment, the sulfonate compound comprises the following structure: , , , , , Any one or a mixture of several of them.

[0020] Preferably, this embodiment also proposes a method for preparing the sulfonate compound according to the above description, wherein methyl disulfonic acid or its derivative is used as raw material, and an acid-binding agent is added dropwise to form a suspension in an organic solvent environment, and then a ligand corresponding to the raw material is added dropwise to react. After the addition is completed, the reaction is continued at a constant temperature for 2-10 hours to obtain the reaction product; the reaction product is post-treated to obtain the sulfonate compound; the reaction temperature range is controlled in the range of -10 to 100°C, more preferably -10 to 20°C, and even more preferably -5 to 5°C.

[0021] Preferably, in this embodiment, the derivative of methyl disulfonic acid is selected from any one or a mixture of several of methyl disulfonic acid chloride, methyl disulfonic acid bromide, and methyl disulfonic acid fluoride; and / or the acid binding agent is pyridine or triethylamine; and / or the ligand is one of alkyl alcohol, alkynyl alcohol, alkenyl alcohol, cyano alcohol, aryl alcohol, and haloalcohol; and / or the reaction solvent is any one or a mixture of several of ether organic solvents, carbonate organic solvents, carboxylic acid ester organic solvents, chlorinated hydrocarbons, alkanes, and nitrile organic solvents.

[0022] Preferably, in this embodiment, the molar ratio of the ligand to methanedisulfonic acid or its derivative is 1-3 times, more preferably 1.8-2.5 times, and most preferably 2.1 times; and / or the molar ratio of the acid-binding agent to methanedisulfonic acid or its derivative is 1-3 times, more preferably 1.8-2.5 times, and most preferably 2.1 times; and / or the amount of organic solvent added is 4-12 times the weight of methanedisulfonic acid or its derivative, more preferably 5-10 times.

[0023] It should be noted that the post-processing involved in this embodiment mainly refers to the fine separation (using known separation processes) and / or purification (using known purification processes) of the reaction products (in a mixed state) after the reaction is completed. For example, firstly, unreacted raw materials or salts are removed by washing and extraction, and then further purified by crystallization to obtain high-purity target sulfonate compounds. These are all conventional technical means that can be used by those skilled in the art based on the content described in this application. Finally, the purity and structure of the final product are accurately characterized by known analytical methods such as nuclear magnetic resonance (NMR) to ensure that the target product that meets the requirements is obtained.

[0024] Preferably, this embodiment also proposes an application of the sulfonate compound described above, in which the sulfonate compound is added to the lithium-ion battery electrolyte; preferably, in this embodiment, the lithium-ion battery electrolyte includes an organic solvent system, a lithium salt system, and an additive system; the organic solvent system includes at least one cyclic carbonate and at least one chain carbonate, wherein preferably, the chain carbonate is ethyl methyl carbonate (EMC) and / or dimethyl carbonate (DMC) and / or diethyl carbonate (DEC); the cyclic carbonate may be ethylene carbonate (EC) and / or propylene carbonate (PC); the additive system includes the sulfonate compound as described above in this embodiment.

[0025] Preferably, in this embodiment, the sulfonate compound accounts for 0.5-5% of the mass fraction of the lithium-ion battery electrolyte; more preferably, 1-4%, and even more preferably 1.2-2.5%; the chain carbonate accounts for 75-92% of the mass fraction of the lithium-ion battery electrolyte, more preferably 80-90%. Preferably, in this embodiment, the lithium salt system includes any one or a mixture of several of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(oxalateborate)borate (LiBOB), lithium perchlorate (LiClO4), lithium trifluoromethanesulfonate (LiOTf), and lithium tetrafluoroborate (LiBF4); preferably, in this embodiment, the concentration of the lithium salt system in the electrolyte of the ternary lithium-ion battery is 0.5-2 mol·L⁻¹. -1 Preferably, in this embodiment, the additive system further includes the combined use of at least two of the following: ethylene carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfate (DTD), propanesulfonate lactone (PS), and lithium difluorooxalate borate (LiODFB), which account for 1-8% of the mass fraction of the lithium-ion battery electrolyte.

[0026] This embodiment also specifically proposes a method for preparing a lithium-ion battery electrolyte based on sulfonate compounds as described above. The method involves mixing the raw materials of the organic solvent system to obtain an organic solvent mixture, freezing the organic solvent mixture for 1-3 hours, adding the lithium salt system to the organic solvent mixture for mixing, and finally adding the additive system for mixing to obtain the lithium-ion battery electrolyte.

[0027] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0028] Based on the above-described implementation schemes, this application further proposes the following specific embodiments: First, it should be noted that the reagent raw materials used in the following specific embodiments and comparative examples of the present invention are sourced from the following: Unless otherwise specified, all raw materials are ordinary commercially available products.

[0029] The test methods used in the specific embodiments and comparative examples of this invention are as follows: Nuclear magnetic resonance (NMR) analysis was performed using a Bruker AVANCE II 400 MHz spectrometer. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0030] Example 1: A certain amount of methyl disulfonyl chloride was dispersed in dichloromethane (as an organic solvent), and the temperature was controlled at 0°C. Pyridine (as an acid-binding agent) was slowly added dropwise to form a suspension. Trifluoroethanol (as a ligand) was then added dropwise to the reaction system. After the addition was completed, the reaction was continued at this temperature for 5 hours. The molar ratio of pyridine, trifluoroethanol and methyl disulfonyl chloride was 2.1:2.1:1, and the weight ratio of dichloromethane to methyl disulfonyl chloride was 10:1. After the reaction was complete, the system was adjusted to neutral with hydrochloric acid; then the reaction solution was washed with cold water to remove pyridine hydrochloride and obtain the organic phase. The organic phase was further concentrated to obtain a crude product. A methyl tert-butyl ether: petroleum ether in a mass ratio of 1:1 was added to the crude product to induce crystallization, finally yielding a sulfonate compound with the following structural formula: ; The sulfonate compounds synthesized above were characterized by NMR (1H, 13C): 1H NMR: δ 4.05 (4H,q), 4.77 (2H, s); 13 C NMR: δ 70.6, 71.2, 121.

[0031] Example 2: A certain amount of methyl disulfonyl chloride was dispersed in dichloromethane (as an organic solvent), and the temperature was controlled at -5°C. Pyridine (as an acid-binding agent) was slowly added dropwise to form a suspension. Propynol (as a ligand) was then added dropwise to the reaction system. After the addition was completed, the reaction was continued at this temperature for 5 hours. The molar ratio of pyridine, propynol and methyl disulfonyl chloride was 2.1:2.1:1, and the weight ratio of dichloromethane to methyl disulfonyl chloride was 10:1. After the reaction was complete, the system was adjusted to neutral with hydrochloric acid; then the reaction solution was washed with cold water to remove pyridine hydrochloride and obtain the organic phase. The organic phase was further concentrated to obtain a crude product. Methyl tert-butyl ether and petroleum ether in a mass ratio of 1:1 were added to the crude product to induce crystallization, and finally, a sulfonate compound with the following structural formula was obtained: ; The sulfonate compounds synthesized above were characterized by NMR (1H, 13C): 1 H NMR: δ 4.77 (2H, s), 4.27 (4H, d), 3.31 (2H, t); 13 C NMR: δ 78.7, 76.1, 50.9, 68.3.

[0032] Example 3: A certain amount of methyl disulfonyl chloride was dispersed in dichloromethane (as an organic solvent), and the temperature was controlled at -5°C. Triethylamine (as an acid-binding agent) was slowly added dropwise to form a suspension. 3-hydroxypropionitrile (as a ligand) was then added dropwise to the reaction system. After the addition was completed, the reaction was continued at this temperature for 5 hours. The molar ratio of triethylamine, 3-hydroxypropionitrile, and methyl disulfonyl chloride was 2.1:2.1:1, and the weight ratio of dichloromethane to methyl disulfonyl chloride was 10:1. After the reaction was complete, the system was adjusted to neutral with hydrochloric acid; then the reaction solution was washed with cold water to remove triethylamine hydrochloride and obtain the organic phase. The organic phase was further concentrated to obtain a crude product. Methyl tert-butyl ether and petroleum ether in a mass ratio of 1:1 were added to the crude product to induce crystallization, and finally, a sulfonate compound with the following structural formula was obtained: ; The sulfonate compounds synthesized above were characterized by NMR (1H, 13C): 1 H NMR: δ 2.6 4H, t), 3.9 (4H, t), 4.7 (2H, s); 13 C NMR: δ 117.1, 70.5, 56.4, 17.1.

[0033] Example 4: A certain amount of methyl disulfonyl chloride was dispersed in dichloromethane (as an organic solvent), and the temperature was controlled at -5°C. Triethylamine (as an acid-binding agent) was slowly added dropwise to form a suspension. A solution of p-fluorophenol in dichloromethane (as a ligand) was then added dropwise to the reaction system. After the addition was completed, the reaction was continued at this temperature for 8 hours. The molar ratio of triethylamine, p-fluorophenol and methyl disulfonyl chloride was 2.1:2.1:1, and the weight ratio of dichloromethane to methyl disulfonyl chloride was 10:1. After the reaction was complete, the system was adjusted to neutral with hydrochloric acid; then the reaction solution was washed with cold water to remove triethylamine hydrochloride and obtain the organic phase. The organic phase was further concentrated to obtain a crude product. Methyl tert-butyl ether and petroleum ether in a mass ratio of 1:1 were added to the crude product to induce crystallization, and finally, a sulfonate compound with the following structural formula was obtained: ; The sulfonate compounds synthesized above were characterized by NMR (1H, 13C): 1H NMR: δ 7.26 (4H, m), 7.27 (4H, m), 4.76 (2H, s); 13C NMR: δ 69.3, 116.9, 117.5, 147.3, 155.5.

[0034] Comparative Example 1: This Comparative Example 1 uses the following compound provided in the example of prior patent application CN119381518A: .

[0035] For the purity and yield of the products in Examples 1-4, please refer to Table 1 below:

[0036] As can be seen from Table 1 above, the reaction conditions proposed in this application are mild, and the product purity and yield are high.

[0037] To further verify the application effects achieved in Embodiments 1-4 of this application, the following comparative application experiments were conducted on the products provided in Embodiments 1-4 and Comparative Example 1 respectively: The pouch cells corresponding to Examples 1-4 and Comparative Example 1 were fabricated according to the following steps: Electrolyte preparation: Prepared in a glove box under N2 atmosphere; the water content of the organic solvent system is <10 ppm; the electrolyte includes: The organic solvent system with a mass fraction of 85.5% is specifically composed of diethyl carbonate (DEC): ethyl methyl carbonate (EMC): dimethyl carbonate (DMC) in a mass ratio of 1:1:1 (wt%). The lithium salt system uses 1.0 mol·L⁻¹ -1Lithium hexafluorophosphate (LiPF6); The products provided in Examples 1-4 and Comparative Example 1 were selected respectively, and the product accounted for 1.5% of the electrolyte by mass. The rest are other additives, specifically composed of vinyl sulfate DTD: fluorovinyl carbonate FEC: lithium difluorooxalate borate LiODFB = 2:1:1 (wt%). After the raw materials of the organic solvent system are mixed evenly in a fixed ratio, the mixture is frozen and cooled for 1.5-2 hours to obtain an organic solvent mixture. The lithium salt system is added and mixed evenly. Finally, the products provided in Examples 1-5 and Comparative Example 1, as well as other additives, are added and mixed evenly for later use.

[0038] Preparation of the battery positive electrode: Using methylpyrrolidone (NMP) as a solvent, 2% (w / w) of polyvinylidene fluoride (PVDF) was uniformly dispersed to obtain a mixture. Then, 2% (w / w) of carbon nanotubes (CNTs) were added and uniformly mixed. Next, 96% (w / w) of the positive electrode active material (lithium cobalt oxide, LiCoO2) was added and mixed uniformly. The mixture was then uniformly coated onto aluminum foil using a coating machine. After drying, rolling, and cutting, the positive electrode sheet was formed with an areal density ranging from 350-450 g / cm³. 2 (Double-sided); Preparation of the battery negative electrode: Using deionized water as a solvent, 1% by mass of carboxymethyl cellulose (CMC) is uniformly dispersed to obtain a mixture. Then, 2% by mass of conductive carbon black (SP) and 96% by mass of negative electrode active material (specifically, vapor-deposited silicon carbon, material type SH-SO2) are added and uniformly mixed. Finally, 1% by mass of styrene-butadiene rubber (SBR) is added and uniformly mixed. After uniform mixing, the mixture is evenly coated onto copper foil using a coating machine. After drying, rolling, and cutting, the negative electrode sheet is formed with an areal density ranging from 200-350 g / cm³. 2 (Double-sided); To further demonstrate the effectiveness of the implementation, this application also includes the following comparative examples 2-5: Comparative Example 2: The rest of the technical solutions of Comparative Example 2 are the same as those of Example 1, except that the product in Example 2 is replaced with the additive ethylene carbonate (VC).

[0039] Comparative Example 3: The rest of the technical solutions of Comparative Example 3 are the same as those of Example 2, except that the product in Example 3 is replaced with the additive ethylene carbonate (VC).

[0040] Comparative Example 4: The remaining technical solutions of Comparative Example 4 are the same as those of Example 3, except that the product in Example 4 is replaced with the additive ethylene carbonate (VC).

[0041] Comparative Example 5: The rest of the technical solutions of Comparative Example 5 are the same as those of Example 4, except that the product in Example 5 is replaced with the additive ethylene carbonate (VC).

[0042] Therefore, we obtained pouch cells assembled from the electrolytes provided in Examples 1-4 and Comparative Examples 1-5, respectively, using the products provided as specific additives. The electrolyte usage of each pouch cell was 4 g / Ah. Then, the following performance comparison tests were conducted on each pouch cell: Three groups of each soft-pack battery corresponding to Examples 1-4 and Comparative Examples 1-5 were made. Each group was cycled for 300 cycles at 25°C, 45°C and 60°C respectively. The charge and discharge conditions used for each cycle test were: charge and discharge rate of 1C / 1C and voltage range of 2.5V-4.2V. The measured capacity retention rates of the lithium-ion batteries are shown in Table 2 below:

[0043] To further enhance the effectiveness of the sulfonate compounds proposed in the above embodiments of this application for specific lithium-ion batteries, this embodiment also proposes a ternary lithium-ion battery, employing a lithium-ion battery electrolyte based on the sulfonate compounds described above; its positive electrode active material includes lithium nickel cobalt manganese oxide (LiNixCoyMn1-x-yO2, NCM) as a ternary positive electrode material, preferably NCM622 or NCM811, i.e., the ratio between N (representing nickel), C (representing cobalt), and M (representing manganese) is 6:2:2 or 8:1:1; preferably, in this embodiment, the negative electrode active material of the ternary lithium-ion battery includes graphite or a known carbon-silicon composite material.

[0044] To further verify the implementation effect of the electrolyte for the specific ternary lithium-ion battery proposed in the above embodiments of this application, this application further provides the following embodiments and comparative examples: Example 5: An electrolyte for a ternary lithium-ion battery, comprising: The organic solvent system with a mass fraction of 85.5% is specifically composed of fluoroethylene carbonate FEC: ethylene carbonate EC: methyl ethyl carbonate EMC: propyl propionate PP = 2:2:2:4 (wt%). The lithium salt system used was 1.0 mol·L⁻¹ lithium hexafluorophosphate (LiPF₆). Example 1 provides a product with a mass fraction of 1.5%; The remainder consists of other additives, specifically composed of vinyl sulfate DTD: fluorovinyl carbonate FEC: lithium difluorooxalate borate LiODFB = 2:1:1 (wt%). The electrolyte is prepared in a glove box under N2 atmosphere, ensuring that the water content of the solvent system is <10ppm. During preparation, the raw materials of the organic solvent system are first mixed evenly in a fixed ratio, and then the mixture is cooled to a freezing temperature of 1.5-2 hours to obtain an organic solvent mixture. The lithium salt system is then added and mixed evenly. Finally, the product provided in Example 1 and other additives are added and mixed evenly before use.

[0045] Example 6: The remaining technical solutions of Example 6 are the same as those of Example 5, except that in Example 6, the product provided in Example 2 is used instead of the product provided in Example 1.

[0046] Example 7: The remaining technical solutions of Example 7 are the same as those of Example 5, except that in Example 7, the product provided in Example 3 is used instead of the product provided in Example 1.

[0047] Example 8: The remaining technical solutions of Example 8 are the same as those of Example 5, except that in Example 8, the product provided in Example 4 is used instead of the product provided in Example 1.

[0048] Comparative Example 6: The remaining technical solutions of Comparative Example 6 are the same as those of Example 5, except that in Comparative Example 6, the product provided by Comparative Example 1 is used instead of the product provided by Example 1.

[0049] Comparative Example 7: The remaining technical solutions of Comparative Example 7 are the same as those of Example 5, except that in Comparative Example 7, the organic solvent system is specifically composed of propylene carbonate PC and ethylene carbonate EC = 1:1 (wt%).

[0050] Then, the pouch cells corresponding to Examples 5-8 and Comparative Examples 6-7 were fabricated according to the following steps: Preparation of the positive electrode of the battery: Using methylpyrrolidone (NMP) as solvent, 2% by mass of polyvinylidene fluoride (PVDF) is uniformly dispersed to obtain a mixed solution. Then, 2% by mass of carbon nanotubes (CNT) are added and uniformly mixed. After that, 96% by mass of positive electrode active material (using the ternary system NCM622) is added and mixed evenly. The mixture is then uniformly coated on aluminum foil using a coating machine. After drying, rolling, and cutting, the positive electrode sheet is formed with an areal density range of 350-450 g / cm2 (double-sided). Preparation of the battery negative electrode: Using deionized water as a solvent, 1% by mass of carboxymethyl cellulose (CMC) is uniformly dispersed to obtain a mixed solution. Then, 2% by mass of conductive carbon black (SP) and 96% by mass of negative electrode active material are added and uniformly mixed. Finally, 1% by mass of styrene-butadiene rubber (SBR) is added and uniformly mixed. After uniform mixing, the mixture is evenly coated on copper foil using a coating machine. After drying, rolling, and cutting, the negative electrode sheet is formed with an areal density range of 200-350 g / cm2 (double-sided). Therefore, we obtained: NCM622|| graphite pouch batteries assembled from the electrolytes provided by Examples 5-8 and Comparative Examples 6-7 respectively as specific additives, with each pouch battery using an electrolyte amount of 4g / Ah. To further demonstrate the application effect of the embodiments of this application in ternary lithium-ion batteries, this application also provides the following embodiment 9: Example 9: The remaining technical solutions of Example 9 are the same as those of Example 5, except that the positive electrode active material in the soft pack battery of Example 9 is the ternary NCM811 system.

[0051] Then, the following performance comparison tests were conducted on each pouch battery: Three groups of each soft-pack battery corresponding to Examples 5-9 and Comparative Examples 6-7 were made. Each group was cycled for 300 cycles at 25°C, 45°C and 60°C respectively. The charge and discharge conditions used for each cycle test were: charge and discharge rate of 1C / 1C and voltage range of 2.7V-4.2V. The measured capacity retention rates of lithium-ion batteries are shown in Table 3 below:

[0052] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0053] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A sulfonate compound, characterized in that, It contains the following structural formula: X is selected from any one of halogen, alkyl, alkenyl, alkynyl, cyano, and aryl.

2. The sulfonate compound according to claim 1, characterized in that, The halogen is fluorine, Any one of chlorine, bromine, and iodine; The alkyl group is either substituted or unsubstituted C1-C. 10 alkyl; The alkenyl group is a substituted, unsubstituted, or heteroatom-containing C2-C group. 10 alkenyl; The alkynyl group is a substituted, unsubstituted, or heteroatom-containing C2-C group. 10 alkynyl group; The cyano group is a substituted, unsubstituted, or heteroatom-containing C2-C group. 10 Cyano; The aryl group is an independent aryl group, or a combination of aryl and alkyl groups, or a combination of aryl and heteroatom groups.

3. The sulfonate compound according to claim 2, characterized in that, The alkyl group is selected from any one of methyl-CH3, ethyl-C2H5, n-propyl-CH2CH2CH3, isopropyl-CH(CH3)2, n-butyl-CH2CH2CH2CH3, and tert-butyl-C(CH3)3; the alkenyl group is selected from any one of vinyl-CH=CH2, propenyl-CH2CH=CH2, and butenyl-CH2CH2CH=CH2; the alkynyl group is selected from ethynyl-C≡CH or propynyl-CH2C≡CH; the cyano group is selected from acetonitrile-CH2-C≡N or propionitrile-CH2CH2-C≡N; and the aryl group is selected from any one of phenyl, p-tolyl, and naphthyl.

4. The sulfonate compound according to claim 1, characterized in that, The sulfonate compound comprises the following structure: , , , , , Any one or a mixture of several of them.

5. A method for preparing the sulfonate compound according to any one of claims 1-4, characterized in that, Using methanedisulfonic acid or its derivatives as raw materials, an acid-binding agent is added dropwise to form a suspension in an organic solvent environment, followed by the addition of a ligand corresponding to the raw material to carry out the reaction. After the addition is completed, the reaction is continued at a constant temperature for 2-10 hours to obtain the reaction product. The reaction product is then post-treated to obtain the sulfonate compound. The temperature range of the reaction is controlled between -10 and 100°C.

6. The method for preparing the sulfonate compound according to claim 5, characterized in that, The derivative of methyl disulfonic acid is selected from any one or a mixture of several of methyl disulfonic acid chloride, methyl disulfonic acid bromide, and methyl disulfonic acid fluoride; and / or the acid-binding agent is pyridine or triethylamine; and / or the ligand is one of alkyl alcohol, alkynyl alcohol, alkenyl alcohol, cyano alcohol, aryl alcohol, and haloalcohol; and / or the reaction solvent is any one or a mixture of several of ether organic solvents, carbonate organic solvents, carboxylic acid ester organic solvents, chlorinated hydrocarbons, alkanes, and nitrile organic solvents.

7. The method for preparing the sulfonate compound according to claim 5, characterized in that, The molar ratio of the ligand to methyl disulfonic acid or its derivative is 1-3 times; and / or the molar ratio of the acid-binding agent to methyl disulfonic acid or its derivative is 1-3 times; and / or the amount of organic solvent added is 4-12 times the weight of methyl disulfonic acid or its derivative.

8. An application of the sulfonate compound according to any one of claims 1-4, characterized in that, The sulfonate compound is added to the lithium-ion battery electrolyte.

9. The application of the sulfonate compound according to claim 8, characterized in that, The lithium-ion battery electrolyte comprises an organic solvent system, a lithium salt system, and an additive system; the organic solvent system comprises at least one cyclic carbonate and at least one chain carbonate; the additive system comprises the sulfonate compound.

10. The application of the sulfonate compound according to claim 9, characterized in that, The sulfonate compound accounts for 0.5-5% of the mass fraction of the lithium-ion battery electrolyte; more preferably 1-4%; the chain carbonate accounts for 75-92% of the mass fraction of the lithium-ion battery electrolyte; more preferably 80-90%.

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