Fluorine-containing sulfonic acid group compound, preparation method thereof and electrolyte

Abstract

The invention discloses a fluorine-containing sulfonic acid group compound, specifically, the structural general formula of the fluorine-containing sulfonic acid group compound is # imgabs0 #, wherein M is a metal ion, and m is equal to 1, 2 or 3; a is a difluorophosphate radical, a trifluoromethanesulfinic acid radical, a trifluoromethanesulfonate radical, a nitrate radical, a trifluoromethyl group or a cyano group; f is a fluorine atom; z is a boron atom or a phosphorus atom, b is 0 or 1, and a and f are independently integers from 0 to 4; o is an oxygen atom; y1 is a carbon atom or a sulfur atom, and c is equal to 1 or 2; y2 is a carbon atom or a sulfur atom, and d = 1 or 2; r1 and R2 are independently carbon chains with the carbon atom number of 0-3; x1, X2, X3 and X4 are independently a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a hydrogen atom, a cyano group, a methyl group, a trifluoromethyl group or a vinyl group; the invention also discloses a preparation method of the fluorine-containing sulfonic acid group compound. The fluorine-containing sulfonic acid group compound electrolyte battery disclosed by the invention is low in gas production rate and high in ionic conductivity and transference number under high-temperature and high-pressure conditions, and the cycling stability and the rate capability of the battery are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery electrolyte materials, and in particular to a fluorine-containing sulfonic acid compound, a preparation method thereof, and an electrolyte. Background Art

[0002] As the global energy structure transitions toward cleaner, more electrified energy, lithium-ion batteries, as a high-energy-density energy storage technology, have become a core enabler for electric vehicles, smart grids, and portable electronic devices. Traditional lithium-ion battery electrolyte systems generally use lithium hexafluorophosphate (LiPF6) as the primary salt. While LiPF6 exhibits acceptable ionic conductivity and electrochemical stability at room temperature, the PF bond in its molecular structure suffers from poor thermodynamic stability, causing LiPF6 to readily decompose and release toxic hydrogen fluoride gas. This affects the chemical and electrochemical properties of the electrolyte, destroying the solid electrolyte interface (SEI) membrane, leading to battery capacity decay, increased internal resistance, and the risk of thermal runaway. Furthermore, LiPF6 readily hydrolyzes to release HF gas, further damaging the integrity of the SEI membrane, making it difficult to meet the high-temperature cycling and high-voltage tolerance requirements of high-energy-density batteries.

[0003] In response to the above-mentioned limitations of LiPF6, researchers have developed a new lithium salt, lithium difluorooxalatoborate (LiDFOB). The molecular structure of LiDFOB combines the rigid skeleton of the oxalate borate group with the strong electron-withdrawing effect of the fluorine atom. It has high ionic conductivity at room temperature, and its decomposition products (such as LiF and lithium borate) can form a dense and ion-conductive solid electrolyte interface film on the electrode surface in a voltage system below 4.5V, effectively inhibiting the continuous decomposition of the electrolyte, thereby improving the cycle stability of the battery.

[0004] However, as battery applications evolve towards high voltage (>4.5V) and high temperature (>60℃), the molecular structure defects of LiDFOB are gradually exposed. 2- ) is thermodynamically unstable and easily decomposes under high temperature and high pressure conditions, releasing gases such as CO and CO2, which triggers local electrolyte bloating and destroys the integrity of the solid electrolyte interface membrane, leading to electrode / electrolyte interface contact failure and affecting battery performance and safety. Summary of the Invention

[0005] In response to the shortcomings of the existing technology, the first purpose of the present invention is to provide a fluorine-containing sulfonic acid compound, which solves the problem of poor stability of traditional lithium salt LiDFOB under high voltage and high temperature conditions due to the structural defects of the oxalic acid group; the second purpose is to provide a method for preparing the fluorine-containing sulfonic acid compound; and the third purpose is to provide an electrolyte for the fluorine-containing sulfonic acid compound.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A fluorine-containing sulfonic acid compound, wherein the general structural formula of the fluorine-containing sulfonic acid compound is:

[0008]

[0009] in:

[0010] M is a lithium ion, a sodium ion, a potassium ion, a magnesium ion or an aluminum ion, and when M is a lithium ion, a sodium ion or a potassium ion, m=1; when M is a magnesium ion, m=2; when M is an aluminum ion, m=3;

[0011] A is difluorophosphate, trifluoromethylsulfinate, trifluoromethylsulfonate, nitrate, trifluoromethyl or cyano;

[0012] F is a fluorine atom;

[0013] Z is a boron atom or a phosphorus atom. When Z is a boron atom, b=0 or 1, a and f are independently 0, 1 or 2, and a+f+2b=2. When Z is a phosphorus atom, b=0, 1 or 2, a and f are independently 0, 1, 2, 3 or 4, and a+f+2b=4.

[0014] O is an oxygen atom;

[0015] Y 1 is a carbon atom or a sulfur atom, when Y 1 When Y is a carbon atom, c=1; 1 When it is a sulfur atom, c=1 or 2;

[0016] Y 2 is a carbon atom or a sulfur atom, when Y 2 When it is a carbon atom, d = 1, when it is a sulfur atom, d = 1 or 2;

[0017] R 1 、R 2 is independently a carbon chain with 0-3 carbon atoms, and when the carbon number of the carbon chain is 0, it means that the two side groups are directly connected; wherein, when Z is a boron atom, Y 1 When it is a carbon atom and a=b=0, R 1 A carbon chain with 1 to 3 carbon atoms;

[0018] X 1 、X 2 Corresponding representation R 1 The group on X 3 、X 4 Corresponding representation R 2 The group on X 1 、X 2 、X 3 、X4 are independently a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a hydrogen atom, a cyano group, a methyl group, a trifluoromethyl group or a vinyl group.

[0019] According to the above technical means, the fluorinated sulfonic acid compound of the present invention is a new type of salt. The fluorinated sulfonic acid group introduced into its structure is different from the oxalic acid group (C2O4 2- ) has significant structural and performance advantages; first, the highly stable covalent bonds (S=O and SF bonds) formed by the sulfur atom in the sulfonic acid group and the strongly electronegative oxygen atom and fluorine atom give it stronger thermodynamic stability and antioxidant ability, and the gas production rate is low under high temperature (>60℃) and high pressure (>4.5V), thereby reducing the expansion of the electrolyte and improving the cycle stability. The ionic conductivity and migration number are high, which improves the battery cycle stability and rate performance; secondly, LiF and sulfur-boron complexes generated by the fluorosulfonic acid group during the decomposition process can form a high ionic conductivity and dense interfacial film, optimize the transport kinetics of metal ions (such as lithium ions in lithium batteries), and further improve the long-term cycle stability of the battery (such as the capacity retention rate after 500 cycles is as high as 98%) and safety. The fluorosulfonic acid group solves the inherent defects of the oxalic acid group in traditional lithium salts in high-pressure and high-temperature systems through the dual effects of structural stability and functional decomposition products.

[0020] Furthermore, the fluorine-containing sulfonic acid compound is one of the following structural formulas:

[0021]

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

[0029] According to the above technical means, it should be noted that the above are some of the compounds claimed to be protected by the present invention, but are not limited to this and should not be understood as limiting the fluorine-containing sulfonic acid compound of the present invention. In the general structural formula of the fluorine-containing sulfonic acid compound, M is a metal ion, including lithium ions, sodium ions, potassium ions, magnesium ions, and aluminum ions. Their application in batteries is known to those skilled in the art to be interchangeable and have similar functions.

[0030] The present invention provides a method for preparing the above-mentioned fluorine-containing sulfonic acid compound, comprising the following steps:

[0031] S1. Mix the potassium salt, the reactant, and the solvent, react at a temperature of -20°C to 80°C for 3-20 hours, filter, and concentrate the filtrate to obtain an intermediate;

[0032] S2. The intermediate, solvent 2 and the metal compound are mixed, reacted at a temperature of -20°C to 80°C for 0.5-2h, filtered, crystallized, and the filtrate is concentrated and crystallized to obtain a fluorine-containing sulfonic acid compound.

[0033] Furthermore, in step S1:

[0034] The potassium salt is at least one of dipotassium sulfonate difluoroacetate, dipotassium sulfonate acetate, dipotassium sulfinate acetate, dipotassium malonate, potassium oxalate, and dipotassium 2-fluoromalonate;

[0035] The reactant is at least one of phosphorus pentafluoride, boron trifluoride, boron trifluoride ethyl ether, and boron trifluoride dimethyl carbonate;

[0036] The first solvent is at least one of ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl acetate, methyl propionate, ethyl ether, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, furan, tetrahydropyran, 1,3-dioxane, 1,4-dioxane, isopropyl ether, and 1,2-dimethoxyethane.

[0037] Furthermore, in step S2:

[0038] The second solvent is at least one of ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl acetate, methyl propionate, ethyl ether, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, furan, tetrahydropyran, 1,3-dioxane, 1,4-dioxane, isopropyl ether, and 1,2-dimethoxyethane;

[0039] The metal compound is at least one of lithium tetrafluoroborate, sodium tetrafluoroborate, potassium tetrafluoroborate, magnesium tetrafluoroborate, and aluminum tetrafluoroborate.

[0040] The present invention provides an electrolyte containing a fluorine-containing sulfonic acid compound, comprising the fluorine-containing sulfonic acid compound as described above.

[0041] Furthermore, it also includes a solute and an organic solvent, and the mass percentage of the fluorine-containing sulfonic acid compound is 0.1-45%, the percentage of the solute is 10-30%, and the rest is the organic solvent.

[0042] Further, the solute is at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium hexafluoroantimonate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(pentafluoroethanesulfonyl)imide, lithium (trifluoromethanesulfonyl)(pentafluoroethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium (trifluoromethanesulfonyl)(fluorosulfonyl)imide, lithium (pentafluoroethanesulfonyl)(fluorosulfonyl)imide, lithium tris(trifluoromethanesulfonyl)methylate, lithium bis(difluorophosphonyl)imide, fluoroethylene carbonate, difluoroethylene carbonate, vinylene carbonate, vinyl sulfate, vinyl disulfate, pentaerythritol sulfate, propane sultone, pentafluoroethoxycyclotriphosphazene, biphenyl, and tris(trimethylsilyl)phosphate.

[0043] Furthermore, the organic solvent is at least one of ethylene carbonate, propylene carbonate, butylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl butyl carbonate, ethyl acetate, isopropyl acetate, n-propyl acetate, propyl propionate, and ethyl difluoroacetate.

[0044] The present invention provides a lithium ion battery comprising a positive electrode, a negative electrode and a separator. The lithium ion battery also comprises the electrolyte of the fluorine-containing sulfonic acid compound.

[0045] Beneficial effects achieved by the present invention:

[0046] The fluorinated sulfonic acid compound of the present invention is a novel fluorinated sulfonic acid salt constructed by introducing a fluorinated sulfonic acid group. Under the synergistic effect of the sulfur atom, the strongly electronegative oxygen atom, and the fluorine atom in the sulfonic acid group, the thermodynamic stability and electrochemical tolerance are improved. The fluorinated sulfonic acid group has a low gas production rate under high temperature (>60°C) and high voltage (>4.5V) conditions, thereby reducing the overall gas expansion of the battery. The ionic conductivity and transfer number are high, thereby improving the battery cycle stability and rate performance, and extending the battery life. Moreover, the LiF and sulfur-boron complex generated during the decomposition process of the fluorinated sulfonic acid group can form a high ionic conductivity and dense interfacial film, further optimizing the transport kinetics of metal ions (such as lithium ions in lithium batteries), and improving the long-cycle stability (such as a capacity retention rate of up to 98% after 500 cycles) and safety of the battery. The fluorinated sulfonic acid group solves the inherent defects of the oxalic acid group in traditional lithium salts in high-pressure and high-temperature systems through the dual effects of structural stability and functional decomposition products, providing key material support for the large-scale application of high-energy-density and high-safety lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 is the nuclear magnetic resonance fluorine spectrum of compound 1 in Example 1 of the present invention;

[0048] Figure 2is the nuclear magnetic resonance fluorine spectrum of compound 13 in Example 2 of the present invention;

[0049] Figure 3 This is the nuclear magnetic resonance fluorine spectrum of compound 33 in Example 3 of the present invention. DETAILED DESCRIPTION

[0050] In order to better understand the technical scheme of the present invention, achieve the purpose and beneficial effect, the present invention is further specifically elaborated by the following examples, but it should not be construed as limiting the present invention. Some non-essential improvements and adjustments made by those skilled in the art according to the above-mentioned invention content are also considered to fall within the scope of protection of the present invention. The experimental methods for which specific conditions are not specified in the embodiments are usually carried out according to conventional conditions or according to the conditions recommended by the reagent manufacturer. Unless otherwise specified, the reagents and equipment used in the present invention are conventional reagents and equipment in the art.

[0051] Unless otherwise specified, all reagents and materials used in the following examples were commercially available.

[0052] A person skilled in the art, knowing the compound represented by the structural formula, can know the preparation method of the above compound based on the common knowledge in the field of chemical synthesis. For example, compound 1 can be prepared by the method in Example 1; Figure 1-Figure 3 The chemical shift described in is the chemical shift.

[0053] Example 1: Preparation of a fluorine-containing sulfonic acid compound, the reaction formula is as follows:

[0054]

[0055] Specific experimental steps:

[0056] S1. Difluoro(sulfonic)acetic acid (Cas No. 422-67-3) and potassium hydroxide are mixed in a molar ratio of 1:1 to obtain dipotassium sulfonate difluoroacetate (molecular formula: C2F2SO5K2), the structural formula of which is shown below:

[0057]

[0058] S2, to a 250mL flask, 0.1mol (25.2g) of dipotassium sulfonate difluoroacetate and 126g of anhydrous dimethyl carbonate were added, and at 25°C room temperature, 0.2mol (28.4g) of boron trifluoride ether was slowly added dropwise with stirring. After the addition was complete, the temperature was raised to 60°C and the reaction was allowed to proceed for 20h. The reaction was terminated, the temperature was lowered to room temperature and filtered, and the filtrate was concentrated and crystallized to obtain an intermediate with a yield of 98%;

[0059] S3. Take 0.1 mol (22.3 g) of the intermediate, 126 g of anhydrous dimethyl carbonate and 0.1 mol (94 g) of battery-grade lithium tetrafluoroborate, add them into a 250 mL flask, mix them, stir and react at 25° C. for 1 h, filter, and concentrate the filtrate for crystallization to obtain a fluorine-containing sulfonic acid compound (Compound 1) with a yield of 94%.

[0060] The results of the fluorine NMR spectrum are as follows Figure 1 As shown; ICP-MS was used to detect compound 1; the ICP-MS elemental composition test results were:

[0061] Li: 3.02%, B: 4.74%, F: 33.07%, S: 13.92%, O: 34.81%, C: 10.44%; proved the successful synthesis of compound 1.

[0062] Example 2: Preparation of a fluorine-containing sulfonic acid compound, the reaction formula is as follows:

[0063]

[0064] Specific experimental steps:

[0065] S1. Difluoro(sulfonic)acetic acid (Cas No. 422-67-3) and potassium hydroxide are mixed in a molar ratio of 1:1 to obtain dipotassium sulfonate difluoroacetate (molecular formula: C2F2SO5K2), the structural formula of which is shown below:

[0066]

[0067] S2. To a 250 mL flask, 0.1 mol (25.2 g) of dipotassium sulfodifluoroacetate and 126 g of anhydrous dimethyl carbonate were added, and 0.2 mol (28.4 g) of boron trifluoride ether was slowly added dropwise under stirring at 0 ° C. in an ice bath. After the addition was complete, the mixture was reacted at room temperature of 25 ° C. for 3 h. After the reaction was completed, the mixture was filtered, and the filtrate was concentrated and crystallized to obtain an intermediate with a yield of 97%;

[0068] S2. Take 0.1 mol (39.8 g) of the intermediate, 126 g of anhydrous dimethyl carbonate and 0.1 mol (9.3 g) of battery-grade lithium tetrafluoroborate, add them into a 250 mL flask and mix them. Stir and react at 25° C. for 1 h. Filter and concentrate the filtrate to obtain a fluorine-containing sulfonic acid compound (Compound 13) with a yield of 98%.

[0069] The results of the fluorine NMR spectrum are as follows Figure 2 As shown; and ICP-MS was used to detect compound 13; the ICP-MS elemental composition test results were:

[0070] Li: 1.89%, B: 2.95%, F: 20.83%, S: 17.42%, O: 43.73%, C: 13.18%; this proved the successful synthesis of compound 13.

[0071] Example 3: Preparation of a fluorine-containing sulfonic acid compound, the reaction formula is as follows:

[0072]

[0073] Specific experimental steps:

[0074] S1. Difluoro(sulfonic)acetic acid (Cas No. 422-67-3) and potassium hydroxide are mixed in a molar ratio of 1:1 to obtain dipotassium sulfonate difluoroacetate (molecular formula: C2F2SO5K2), the structural formula of which is shown below:

[0075]

[0076] S2. To a 250 mL flask, 0.1 mol (25.2 g) of dipotassium sulfodifluoroacetate and 126 g of anhydrous dimethyl carbonate were added. Under a 0° C. ice bath, 0.2 mol (25.2 g) of phosphorus pentafluoride gas was introduced with stirring. The addition was complete, and the mixture was reacted at 25° C. room temperature for 3 h. After the reaction was completed, the mixture was filtered, and the filtrate was concentrated and crystallized to obtain an intermediate with a yield of 92%.

[0077] S2. Take 0.1 mol (39.8 g) of the intermediate, 126 g of anhydrous dimethyl carbonate and 0.1 mol (9.3 g) of battery-grade lithium tetrafluoroborate, add them into a 250 mL flask and mix them. Stir and react at 25° C. for 1 h. Filter and concentrate the filtrate to obtain a fluorinated sulfonic acid compound (Compound 33) with a yield of 94%.

[0078] The results of the fluorine NMR spectrum are as follows Figure 3 As shown; and ICP-MS was used to detect compound 33; the ICP-MS elemental composition test results are:

[0079] Li: 1.64%, P: 7.34%, F: 26.88%, S: 15.09%, O: 37.73%, C: 11.32%; this proved the successful synthesis of compound 33.

[0080] Example 4: Preparation of an electrolyte containing a fluorinated sulfonic acid compound as an additive

[0081] 1. Experimental Materials

[0082] Fluorine-containing sulfonic acid compounds (Compound 1, Compound 13, Compound 33), solute LiPF6 and organic solvents (ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC)) prepared under the conditions of Examples 1-3.

[0083] 2. Experimental methods

[0084] 15.2% LiPF6, 28.3% EC, 28.3% EMC and 28.3% DMC were mixed and stirred to prepare a basic electrolyte;

[0085] Take corresponding parts of the basic electrolyte and add 1%, 2% and 3% by mass of compound 1, 1%, 2% and 3% by mass of compound 13, and 1%, 2% and 3% by mass of compound 33 respectively. The resulting electrolytes are recorded as electrolyte 1-1%, 1-2% and 1-3%, 13-1%, 13-2% and 13-3%, 33-1%, 33-2% and 33-3%.

[0086] Example 5: Preparation of an electrolyte containing a fluorinated sulfonic acid compound as the main salt

[0087] 1. Experimental Materials

[0088] Compound 1, ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) prepared under the conditions of Example 1.

[0089] 2. Experimental methods

[0090] 22.9% compound 1, 25.7% EC, 25.7% EMC and 25.7% DMC were respectively taken by mass fraction and mixed and stirred uniformly to prepare a 1 mol / kg electrolyte, which was recorded as 1-M.

[0091] Comparative Example 1: Preparation of an electrolyte containing lithium difluorooxalatoborate as an additive

[0092] 1. Experimental Materials

[0093] Lithium difluorooxalatoborate, solute LiPF6 and organic solvents (ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC)).

[0094] 2. Experimental methods

[0095] 15.2% LiPF6, 28.3% EC, 28.3% EMC and 28.3% DMC were mixed and stirred to prepare a basic electrolyte;

[0096] 1%, 2% and 3% by mass of commercially available lithium difluorooxalatoborate were added to the corresponding parts of the basic electrolyte, and the obtained electrolytes were recorded as electrolytes D-1%, D-2% and D-3%.

[0097] Comparative Example 2: Preparation of an electrolyte containing lithium difluorooxalatoborate as the main salt

[0098] 1. Experimental Materials

[0099] Lithium difluorooxalatoborate, ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC).

[0100] 2. Experimental methods

[0101] 14.5% lithium difluorooxalatoborate, 28.5% EC, 28.5% EMC and 28.5% DMC were respectively taken by mass fraction and mixed and stirred uniformly to prepare a 1 mol / kg electrolyte, which was recorded as DM.

[0102] Example 6: Performance evaluation of electrolyte as additive

[0103] 1. Experimental Materials

[0104] The electrolytes 1-1%, 1-2% and 1-3%, 13-1%, 13-2% and 13-3%, 33-1%, 33-2% and 33-3% prepared under the conditions of Example 4, the electrolytes D-1%, D-2% and D-3% prepared under the conditions of Comparative Example 1, the positive electrode (NCM811 material), the negative electrode (graphite) and the separator.

[0105] 2. Experimental methods

[0106] The positive electrode (NCM811 material), negative electrode (graphite) and separator were made into battery cells, and 6mL of each electrolyte was injected respectively. After sealing and formation operation, soft-pack batteries with a capacity of 2Ah were made; each soft-pack battery was charged and discharged at 60°C with a charge and discharge rate of 1C in the voltage range of 3V-4.6V to test the performance of each electrolyte.

[0107] 3. Experimental results

[0108] When used as an electrolyte additive, the experimental results are shown in Table 1. Taking electrolytes D-1%, D-2%, and D-3% as comparative examples, under the same solute and organic solvent ratio conditions, the electrolyte containing the fluorinated sulfonic acid compound of the present invention has a better capacity retention rate under high temperature and high pressure conditions. This is because the electrolyte containing the fluorinated sulfonic acid lithium salt produces less gas than the electrolyte containing the difluorooxalatoborate lithium salt. Gas production can lead to poor battery contact, resulting in a rapid increase in the battery's direct current resistance (DCIR) and a series of side reactions, thereby affecting the battery's cycle life.

[0109] As can be seen from Table 1, when the addition amount of compound 1 increases from 1% to 3%, the 500-cycle capacity retention rate of the battery increases significantly, while the addition amount of compounds 13 and 33 does not increase significantly after 2%. Considering the cost, the optimal addition amount of compound 1 is 3%, and the optimal addition amount of compounds 13 and 33 is 2%.

[0110] Table 1 Performance test results as electrolyte additive

[0111]

[0112] Example 7: Performance evaluation of the electrolyte as the main salt

[0113] 1. Experimental Materials

[0114] Electrolyte 1-M prepared under the conditions of Example 5, electrolyte DM prepared under the conditions of Comparative Example 2, positive electrode (NCM811 material), negative electrode (graphite) and separator.

[0115] 2. Experimental methods

[0116] 1) Assemble steel sheet-to-steel sheet button cells and test the ionic conductivity of electrolyte 1-M and electrolyte DM at room temperature.

[0117] 2) The positive electrode (NCM811 material), negative electrode (graphite) and separator were made into battery cells, and 6 mL of electrolyte 1-M and electrolyte DM were injected respectively. After sealing and formation operation, soft-pack batteries with a capacity of 2 Ah were made. Each soft-pack battery was charged and discharged at different rates in the voltage range of 3 V-4.6 V at 60°C to test the performance of each electrolyte.

[0118] 3. Experimental results

[0119] 1) The ionic conductivity and DC internal resistance test results of compound 1 and lithium difluorooxalatoborate as the main salts of the electrolyte are shown in Table 2. The room temperature ionic conductivity of electrolyte 1-M containing compound 1 is significantly higher than that of electrolyte DM containing lithium difluorooxalatoborate, and the DC internal resistance is also smaller. This is due to the strong electron-withdrawing ability of the fluorosulfonic acid group in the molecular structure of compound 1, which enables the lithium salt to fully dissociate, thereby improving the ionic conductivity.

[0120] Table 2 Test results of ionic conductivity and DC internal resistance as the main salt of electrolyte

[0121] electrolyte Room temperature ionic conductivity (mS / cm) Room temperature DC resistance (mΩ) 1-M 11.7 25 DM 9.2 47

[0122] 2) The cycling performance results of compound 1 and lithium difluorooxalatoborate as the main salt of the electrolyte at different charge and discharge rates are shown in Table 3. The rate performance of electrolyte 1-M containing compound 1 is significantly better than that of electrolyte DM containing lithium difluorooxalatoborate. This is due to the larger anion volume of compound 1, which makes the electrolyte have a higher ion migration number and reduces the polarization voltage, thereby making the electrolyte have better rate performance.

[0123] Table 3 Rate performance test results of the main salt of the electrolyte

[0124]

[0125] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A fluorine-containing sulfonic acid compound, characterized in that: The general structural formula of the fluorine-containing sulfonic acid compound is: in: M is a lithium ion, a sodium ion, a potassium ion, a magnesium ion or an aluminum ion, and when M is a lithium ion, a sodium ion or a potassium ion, m=1; when M is a magnesium ion, m=2; when M is an aluminum ion, m=3; A is difluorophosphate, trifluoromethylsulfinate, trifluoromethylsulfonate, nitrate, trifluoromethyl or cyano; F is a fluorine atom; Z is a boron atom or a phosphorus atom. When Z is a boron atom, b=0 or 1, a and f are independently 0, 1 or 2, and a+f+2b=2. When Z is a phosphorus atom, b=0, 1 or 2, a and f are independently 0, 1, 2, 3 or 4, and a+f+2b=4. O is an oxygen atom; Y 1 is a carbon atom or a sulfur atom, when Y 1 When Y is a carbon atom, c=1; 1 When it is a sulfur atom, c=1 or 2; Y 2 is a carbon atom or a sulfur atom, when Y 2 When it is a carbon atom, d = 1, when it is a sulfur atom, d = 1 or 2; R 1 、R 2 is independently a carbon chain with 0-3 carbon atoms, and when the carbon number of the carbon chain is 0, it means that the two side groups are directly connected; wherein, when Z is a boron atom, Y 1 When it is a carbon atom and a=b=0, R 1 A carbon chain with 1 to 3 carbon atoms; X 1 、X 2 Corresponding representation R 1 The group on X 3 、X 4 Corresponding representation R 2 The group on X 1 、X 2 、X 3 、X 4 are independently a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a hydrogen atom, a cyano group, a methyl group, a trifluoromethyl group or a vinyl group.

2. A fluorine-containing sulfonic acid compound according to claim 1, characterized in that: The fluorine-containing sulfonic acid compound is one of the following structural formulas:

3. A method for preparing a fluorine-containing sulfonic acid compound according to claim 1, characterized in that: The following steps are involved: S1. Mix the potassium salt, the reactant, and the solvent, react at a temperature of -20°C to 80°C for 3-20 hours, filter, and concentrate the filtrate to obtain an intermediate; S2. The intermediate, solvent 2 and the metal compound are mixed, reacted at a temperature of -20°C to 80°C for 0.5-2h, filtered, and the filtrate is concentrated and crystallized to obtain a fluorine-containing sulfonic acid compound.

4. The method for preparing a fluorine-containing sulfonic acid compound according to claim 3, wherein: In step S1: The potassium salt is at least one of dipotassium sulfonate difluoroacetate, dipotassium sulfonate acetate, dipotassium sulfinate acetate, dipotassium malonate, potassium oxalate, and dipotassium 2-fluoromalonate; The reactant is at least one of phosphorus pentafluoride, boron trifluoride, boron trifluoride ethyl ether, and boron trifluoride dimethyl carbonate; The first solvent is at least one of ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl acetate, methyl propionate, ethyl ether, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, furan, tetrahydropyran, 1,3-dioxane, 1,4-dioxane, isopropyl ether, and 1,2-dimethoxyethane.

5. The method for preparing a fluorine-containing sulfonic acid compound according to claim 3, wherein: In step S2: The second solvent is at least one of ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl acetate, methyl propionate, ethyl ether, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, furan, tetrahydropyran, 1,3-dioxane, 1,4-dioxane, isopropyl ether and 1,2-dimethoxyethane; The metal compound is at least one of lithium tetrafluoroborate, sodium tetrafluoroborate, potassium tetrafluoroborate, magnesium tetrafluoroborate, and aluminum tetrafluoroborate.

6. An electrolyte containing a fluorinated sulfonic acid compound, characterized in that: The invention comprises the fluorine-containing sulfonic acid compound according to any one of claims 1 to 2.

7. The electrolyte of the fluorinated sulfonic acid compound according to claim 6, characterized in that It also includes solute and organic solvent, and the mass percentage of the fluorine-containing sulfonic acid compound is 0.1-45%, the percentage of the solute is 10-30%, and the rest is organic solvent.

8. The electrolyte of the fluorinated sulfonic acid compound according to claim 7, characterized in that The solute is at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium hexafluoroantimonate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(pentafluoroethanesulfonyl)imide, lithium (trifluoromethanesulfonyl)(pentafluoroethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium (trifluoromethanesulfonyl)(fluorosulfonyl)imide, lithium (pentafluoroethanesulfonyl)(fluorosulfonyl)imide, lithium tris(trifluoromethanesulfonyl)methylate, lithium bis(difluorophosphonyl)imide, fluoroethylene carbonate, difluoroethylene carbonate, vinylene carbonate, vinyl sulfate, vinyl disulfate, pentaerythritol sulfate, propane sultone, pentafluoroethoxycyclotriphosphazene, biphenyl, and tris(trimethylsilyl)phosphate.

9. The electrolyte of the fluorinated sulfonic acid compound according to claim 7, characterized in that The organic solvent is at least one of ethylene carbonate, propylene carbonate, butylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl butyl carbonate, ethyl acetate, isopropyl acetate, n-propyl acetate, propyl propionate, and ethyl difluoroacetate.

10. A lithium-ion battery comprising a positive electrode, a negative electrode, and a separator, characterized in that: The lithium-ion battery further comprises an electrolyte comprising the fluorine-containing sulfonic acid compound according to claim 6.

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