A trihydrocarbylsilyl phosphonate sulfate ester, a process for its preparation and a secondary battery electrolyte using the sulfate ester as an additive

Abstract

The present application relates to a kind of trihydrocarbylsilyl phosphonate ester-based sulfates and preparation process and with the sulfates as additive secondary battery electrolyte, electrolyte includes trihydrocarbylsilyl phosphonate ester-based sulfates, electrolyte salt, non-aqueous organic solvent and other additives.The structural general formula of trihydrocarbylsilyl phosphonate ester-based sulfates is:trihydrocarbylsilyl phosphonate ester-based sulfates as secondary battery electrolyte additive, can reduce the direct current resistance of battery, promote high temperature cycle and high temperature storage performance, inhibit the inflation after high temperature storage of battery.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of chemical preparation, and particularly relates to a trihydrocarbylsilyl phosphonate sulfate ester and a preparation process thereof, and a secondary battery electrolyte using the sulfate ester as an additive. BACKGROUND

[0002] Secondary battery electrolyte additives, as one of the most economical and efficient means to improve battery performance, have become the core element of electrolyte functional diversification. Generally, only a small amount of additive needs to be added to significantly improve the key performance indicators of the battery, including rate performance, cycle performance, high and low temperature performance, and safety. Additives are the most economical and efficient method to improve battery performance, and through the screening and proportioning of a small amount of additives, the performance of the electrolyte can be greatly improved, which is the core direction of research in the field of lithium ion battery electrolytes in recent years.

[0003] Positive electrode film-forming additives in the electrolyte can form a protective film or complex layer on the surface of the positive electrode, inhibit the interface side reaction of the electrolyte and the positive electrode and the dissolution of transition metal ions, thereby improving the storage and cycle stability at high temperature and high voltage. However, most positive electrode film-forming additives will deteriorate part of the electrochemical performance while improving the storage and cycle stability. For example, sulfate ester compounds, especially monocyclic sulfate ester compounds, although their film-forming impedance is relatively slightly reduced, their positive electrode film-forming effect is relatively weak, and the effect of inhibiting the interface side reaction of the electrolyte and the positive electrode at high voltage is limited, so their high-temperature storage performance and high-temperature cycle performance need to be improved.

[0004] Therefore, additives are often not used alone in the formulation of electrolytes. In fact, in order to meet the functionalization requirements, two or more types of additives are usually included in the electrolyte. Although this approach improves the functionality of the electrolyte, it also increases the cost and makes the chemical reaction process inside the battery more complex and variable.

[0005] Chinese patent CN109888386A of Dongguan Shanshan Battery Material Co., Ltd. discloses a chain-like sulfur-containing sulfate compound M and a cyclic sulfonate compound N used in combination, the compound M can participate in the formation of a passivation film at the positive and negative electrode interface, improve the high-temperature performance and inhibit the gas production of the battery, but the compound M has high impedance, resulting in poor cycle performance of the electrolyte and the battery configured with the compound M.

[0006] The Chinese patent CN118431564A of Zhejiang Blue Sky Environmental Protection High-tech Co., Ltd. discloses that the first additive is monofluorophosphoric acid group fluoroboric acid and the second additive is a bicyclic sulfate compound. The patent also discloses that the additive also includes a third additive, which is at least one of at least one of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, lithium bisfluorosulfonimide, lithium difluorophosphate bisoxalate, lithium difluorophosphate oxalate borate, lithium tetrafluoroborate, tris(trimethylsilyl) borate, and tris(trimethylsilyl) phosphate. The three additives are used together. The electrolyte can effectively reduce the battery impedance, improve the storage and cycle performance of the battery at high temperature and high voltage, and ensure that the battery has good low temperature and rate performance. However, it has no improvement effect on the inhibition of battery high-temperature storage gas production, low-temperature performance, and capacity retention rate.

[0007] The Chinese patent CN114597492A of Shenzhen Yinxin New Material Co., Ltd. discloses that the additive includes aryl sulfate, silicon-containing compound, fluoroethylene carbonate, and other additives, wherein the other additives include one or more of triallyl phosphate and tris(trimethylsilyl) phosphate. The non-aqueous electrolyte can improve the high-temperature storage performance of the lithium ion battery, and significantly improve the low-temperature cycle performance, discharge performance, and safety performance of the lithium ion battery. However, to achieve the above functions, a large number of additive types are required, the components are complex and the cost is high, but the direct current resistance is not fundamentally reduced, and there are still defects.

[0008] Therefore, in view of the above deficiencies, there is an urgent need to develop a new type of additive that can overcome the above defects and inhibit impedance growth in a high-voltage, high-temperature environment, thereby improving the storage performance and cycle performance of the battery and other indicators. SUMMARY

[0009] The problem to be solved by the present application is to provide a trihydrocarbylsilyl phosphonate sulfate and a preparation process, as well as a secondary battery electrolyte using the sulfate as an additive. The trihydrocarbylsilyl phosphonate sulfate can be used as a secondary lithium battery electrolyte additive, which can reduce the direct current resistance of the battery, improve the high-temperature cycle and high-temperature storage performance, and inhibit the swelling of the battery after high-temperature storage.

[0010] In order to achieve the above technical effects, the technical scheme of the present application is as follows:

[0011] A secondary battery electrolyte containing trihydrocarbylsilyl phosphonate sulfate, the electrolyte comprising trihydrocarbylsilyl phosphonate sulfate, electrolyte salt, non-aqueous organic solvent and other additives.

[0012] As a further technical solution, the structure general formula of the trihydrocarbylsilyl phosphonate sulfate compound I is as follows:

[0013]

[0014]

[0015] Wherein, n≥1, n is preferably 1, 2, or 3; R1, R2, and R3 are selected from C1 to C6 hydrocarbon groups, preferably one of cyano hydrocarbon groups or fluorinated hydrocarbon groups.

[0016] As a further technical solution, the preparation of compound I involves three steps:

[0017] S1: Compound II reacts with compound III. When X in compound III-a is selected from Br or Cl, compound IV is obtained. Compound IV is hydrolyzed to give compound V. The reaction formula is as follows:

[0018]

[0019] Wherein, R is selected from hydrogen atoms or C1 to C4 alkyl groups; n ≥ 1, n is preferably 1, 2, or 3; m takes the value 0 or 1;

[0020] When compound II reacts with compound III, and Y in compound III-b is selected from C1 to C4 alkyl groups, then no hydrolysis step is required to directly obtain compound V, as shown in the following reaction formula:

[0021]

[0022] S2: Compound V is oxidized to give compound VI, as shown in reaction II below:

[0023]

[0024] S3: Compound VI reacts with a trialkylsilyl compound to give the final product compound I, as shown in reaction formula III below:

[0025]

[0026] As a further technical solution, in step S1, compound III-a is preferably thionyl chloride, and compound III-b is preferably one of dimethyl sulfite and diethyl sulfite; the molar ratio of compound III to compound II is 2.0 to 5.0:1, preferably 2.5 to 4.0:1; the reaction temperature is -20 to 40°C, preferably -10 to 20°C.

[0027] As a further technical solution, in step S1, the solvent for the reaction of compound II and compound III is at least one of alkanes, halogenated hydrocarbons, esters, and sulfones, specifically selected from at least one of benzene, toluene, xylene, cyclohexane, cyclopentane, dichloromethane, chloroform, ethyl acetate, butyl acetate, dimethyl carbonate, diethyl carbonate, dimethyl sulfoxide, and sulfolane.

[0028] As a further technical solution, in step S2, compound V is oxidized to obtain compound VI. The oxidant used is selected from one of hydrogen peroxide, ozone, hypochlorous acid, oxygen, air, sodium hypochlorite, ammonium persulfate, potassium persulfate, potassium peroxymonosulfate, peroxysulfuric acid, sodium percarbonate, sodium perchlorate, sodium periodate, manganese oxide, and potassium permanganate. The preferred oxidants are hydrogen peroxide, sodium hypochlorite, and potassium peroxymonosulfate.

[0029] As a further technical solution, in step S2, the reaction solvent is selected from organic solvents or water, preferably organic solvents; the molar ratio of active oxygen provided by the oxidant to compound V is 3.0 to 6.0:1, preferably 3.6 to 4.0:1; the reaction temperature is -20 to 60°C.

[0030] As a further technical solution, in step S3, compound VI reacts with a trialkylsilyl compound to obtain the final product compound I. The trialkylsilyl compound is selected from one of trialkylsilazane, trialkylsiloxane, or trialkylhalosilane; preferably, the trialkylsilyl compound is selected from hexaalkyldisilazane, hexaalkyldisilaurea, heptaalkyldisilamine, trialkylchlorosilane, trialkylalkyloxysilane, trialkylacyloxysilane, trialkylsilylamine, trialkylsilylimidazolium, trialkylamineoxysilane, and trialkylsilyl... At least one of alkenoxysilane, trialkyloxime silane, or N,O-bistrialkylsilylacetamide; more typically selected from at least one of trimethylchlorosilane, hexamethyldisilazane, heptamethyldisilazane, tetramethyldivinyldisilazane, trimethylmethoxysilane, trimethylethoxysilane, trimethylsilylimidazolium, hexamethyldisilazane, or N,O-bistrimethylsilylacetamide, tetramethylbis(trifluoromethyl)disiloxane, tetraisopropyldicyanodisiloxane, and tetramethyl-bis(3-cyanopropyl)disilazane.

[0031] As a further technical solution, in step S3, the molar ratio of the trialkylsilyl compound to compound VI is 2 to 20:1, preferably 4.5 to 12:1; the reaction temperature is -10 to 160°C, and the reaction time is 1 to 40 hours.

[0032] As a further technical solution, other additives are selected from at least one of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), vinyl sulfite (ES), methane disulfonate (MMDS), 1,3-propane sulfonate lactone (PS), 1,3-propene sulfonate lactone (PST), tris(trimethylsilyl) phosphite (TMSPi), tris(trimethylsilyl) borate (TMSB), succinic anhydride (SA), succinic anhydride (SN), adiponitrile (ADN), and ethoxypentafluorocyclotriphosphazene (PFPN).

[0033] As a further technical solution, based on 100% of the total mass of the electrolyte, the amount of the trihydrosilylphosphonate sulfate compound additive is 0.1% to 5%, and the amount of other additives is 0.1% to 5%.

[0034] As a further technical solution, when the secondary battery is a lithium-ion battery, the electrolyte in the electrolyte solution is one or more of the following: lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorophosphate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(oxalateborate), lithium difluorooxalateborate, lithium tetrafluorooxalate phosphate, lithium difluorobis(oxalateborate), and lithium fluorosulfonyl(trifluoromethanesulfonyl)imide, and the molar concentration of the electrolyte in the electrolyte solution is 0.5–2 mol / L;

[0035] As a further technical solution, when the secondary battery is a sodium-ion battery, the electrolyte in the electrolyte is at least one of sodium hexafluorophosphate, sodium difluorophosphate, sodium bis(oxalate-borate), sodium difluorooxalate-borate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium trifluoromethanesulfonate, sodium perchlorate, and sodium tetrafluoroborate.

[0036] As a further technical solution, the non-aqueous organic solvent is composed of one or more of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethylene carbonate, methyl ethyl carbonate, methyl propyl carbonate, methyl butyl carbonate, propylene carbonate, γ-butyrolactone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, difluoroethyl acetate, trifluoroethyl acetate, trifluoroethyl methyl carbonate, and bis(trifluoroethyl) carbonate.

[0037] Compared with the prior art, the beneficial effects of the present invention are:

[0038] This invention proposes a trihydrosilylphosphonate sulfate, its preparation process, and a secondary battery electrolyte using the sulfate as an additive. The trihydrosilylphosphonate sulfate can be used as an additive in a secondary lithium battery electrolyte. Additives containing elements such as phosphorus, sulfur, and silicon can reduce the DC internal resistance of the battery, improve high-temperature cycling and high-temperature storage performance, and suppress gas expansion after high-temperature storage. Attached Figure Description

[0039] Figure 1 These are the preparation process steps for compound I. Detailed Implementation

[0040] The technical solutions in the embodiments of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] A secondary battery electrolyte containing trialkylsilylphosphonate sulfate, the electrolyte comprising trialkylsilylphosphonate sulfate, electrolyte salt, non-aqueous organic solvent and other additives.

[0042] The general structural formula of the trihydrosilylphosphonate sulfate compound I is as follows:

[0043]

[0044] Wherein, n≥1, n is preferably 1, 2, or 3; R1, R2, and R3 are selected from C1 to C6 hydrocarbon groups, preferably one of cyano hydrocarbon groups or fluorinated hydrocarbon groups.

[0045] The preparation of compound I involves three steps:

[0046] S1: Compound II reacts with compound III. When X in compound III-a is selected from Br or Cl, compound IV is obtained. Compound IV is hydrolyzed to give compound V. The reaction formula is as follows:

[0047]

[0048] Wherein, R is selected from hydrogen atoms or C1 to C4 alkyl groups; n ≥ 1, n is preferably 1, 2, or 3; m takes the value 0 or 1;

[0049] When compound II reacts with compound III, and Y in compound III-b is selected from C1 to C4 alkyl groups, then no hydrolysis step is required to directly obtain compound V, as shown in the following reaction formula:

[0050]

[0051] S2: Compound V is oxidized to give compound VI, as shown in reaction II below:

[0052]

[0053] S3: Compound VI reacts with a trialkylsilyl compound to give the final product compound I, as shown in reaction formula III below:

[0054]

[0055] When R1, R2, and R3 are the groups listed in Table 1, the structure of compound I, trialkylsilylphosphonate sulfate, can be determined.

[0056] Table 1 Combinations of R1, R2, and R3 groups

[0057] Compound n R1 R2 R3 I-1 1 -CH3 -CH3 -CH3 I-2 2 -CH3 -CH3 -CH3 I-3 1 -CH2CH3 -CH2CH3 -CH2CH3 I-4 2 -CH2CH3 -CH2CH3 -CH2CH3 I-5 1 -CH3 -CH3 -CH=CH2 I-6 2 -CH3 -CH3 -CH=CH2 I-7 1 -CH3 -CH3 -C6H5 I-8 2 -CH3 -CH3 -C6H5 I-9 3 -CH3 -CH3 -CH3 I-10 3 -CH2CH3 -CH2CH3 -CH2CH3 I-11 3 -CH3 -CH3 -CH=CH2 I-12 3 -CH3 -CH3 -C6H5

[0058] I. Preparation Example

[0059] Preparation Example 1

[0060] Preparation Example 1 provides compound I-1 and its preparation process, including the following steps:

[0061]

[0062] S1: In a 500mL reaction flask equipped with nitrogen protection, mechanical stirring, thermometer, reflux condenser, and tail gas absorption device, add 24.0g (0.25mol) of compound II-1 (hydroxymethylphosphonic acid) and 300mL of dichloromethane, stir until homogeneous, cool to -15℃, add 107.1g (0.9mol) of compound III-1 (thionyl chloride) dropwise, maintain -10 to -8℃, and after the addition is complete, slowly raise the temperature to 0℃ and continue the reaction for 2h. Concentrate the mother liquor to remove low-boiling substances, and purify the crude product by column chromatography to obtain 23.4g of compound IV-1.

[0063] In a 500 mL reaction flask equipped with a mechanical stirrer, thermometer, dropping funnel, reflux condenser, and tail gas treatment device, 23.4 g (0.075 mol) of compound IV-1 prepared in step S1 and 200 mL of dichloromethane were added. The mixture was cooled to -5 °C, and 27.0 g (1.5 mol) of water was added dropwise. The mixture was kept at 0–5 °C and the addition was completed over 3 hours. The mixture was then brought to room temperature and the reaction continued for another 3 hours. Low-boiling substances were removed by vacuum distillation to obtain 16.8 g of compound V-1.

[0064] S2: In a 500mL reaction flask equipped with a magnetic stirrer, thermometer, and reflux condenser, add 16.8g (0.07mol) of compound V-1 prepared in step S1 and 200mL of dichloroethane. Stir to disperse thoroughly, cool to -2℃, and add 25.5g (0.23mol) of 30% hydrogen peroxide solution dropwise. After the addition is complete, keep the temperature at 0-5℃ and continue the reaction for 4h. Separate the liquid and liquid phases. Treat the aqueous phase with sodium bisulfite to remove harmful substances, and remove dichloroethane from the organic phase by distillation. Then purify the crude product by column chromatography to obtain 15.6g of compound VI-1.

[0065] S3: In a 500mL reaction flask equipped with nitrogen protection, magnetic stirring, thermometer, reflux condenser, and tail gas absorption, add 15.6g (0.06mol) of compound VI-1 prepared in step S2 and 200mL of dichloroethane. Stir to dissolve, and add 40.9g (0.38mol) of trimethylchlorosilane dropwise at -10℃ to -5℃. After the addition is complete, raise the temperature to 30℃ to 35℃ and continue the reaction for 3h. The solvent is recovered by vacuum distillation using a water pump to obtain the crude product. Purify by column chromatography to obtain 24.9g of compound I-1 with a purity of 99.0%. The overall yield of the three steps is 34.7% (based on compound II-1).

[0066] Preparation Example 2

[0067] Preparation Example 2 provides compound I-2 and its preparation process, including the following steps:

[0068]

[0069]

[0070] S1: In a 500mL reaction flask equipped with nitrogen protection, mechanical stirring, thermometer, reflux condenser, and tail gas absorption device, 31.5g (0.25mol) of compound II-2 (2-hydroxyethylphosphonic acid) and 300mL of ethyl acetate were added and stirred evenly. First, 15.5g (0.13mol) of compound III-2 (thionyl chloride) was added dropwise. Then, while keeping the dropping rate of thionyl chloride (total 1.1mol, 130.9g) constant, 111.3g (1.1mol) of triethylamine was slowly added dropwise. A solid gradually appeared in the reaction phase. The temperature was maintained at -20 to -10℃. After the addition was complete, the temperature was slowly raised to 20℃ and the reaction continued for 2 hours. The solid salt was removed by filtration. The mother liquor was distilled under reduced pressure using a water pump to recover the solvent. The solution was purified by column chromatography to obtain 29.8g of compound IV-2. In a 500 mL reaction flask equipped with a mechanical stirrer, thermometer, dropping funnel, reflux condenser and tail gas treatment device, 29.8 g (0.08 mol) of compound IV-2 prepared in step S1 and 300 mL of dichloromethane were added. The mixture was cooled to -5 °C, and 10.8 g (0.6 mol) of water was added dropwise. The mixture was kept at 0–5 °C and the addition was completed in 3 h. The mixture was then raised to room temperature and the reaction was continued for another 3 h. The solvent was removed by vacuum distillation to obtain 23.2 g of compound V-2.

[0071] S2: In a 500mL reaction flask equipped with a magnetic stirrer, thermometer, and reflux condenser, add 23.2g (0.078mol) of compound V-2 prepared in step S1 and 200mL of dichloromethane. Stir until thoroughly dispersed, cool to -2℃, and add 10.0g (0.09mol) of 30% hydrogen peroxide solution dropwise. After the addition is complete, slowly raise the temperature to 15-20℃ and continue the reaction for 4 hours. Separate the liquid and aqueous phases. Add sodium bisulfite to the aqueous phase to remove excess hydrogen peroxide for harmless treatment. Remove dichloromethane from the organic phase by atmospheric distillation and purify by column chromatography to obtain 19.0g of compound VI-2.

[0072] S3: In a 250ml reaction flask equipped with nitrogen protection, magnetic stirring, thermometer, reflux condenser, and tail gas absorption device, add 19.0g (0.06mol) of compound VI-2 prepared in step S2 and 96.8g (0.60mol) of hexamethyldisilazane. The mixture is heated to 130℃~135℃ and reacted for 36h. Excess hexamethyldisilazane is recovered by vacuum distillation using a water pump. The mixture is purified by column chromatography to obtain 25.6g of compound I-2 with a purity of 99.2%. The overall yield of the three steps is 36.6% (based on compound II-2).

[0073] Preparation Example 3

[0074] Preparation Example 3 provides compound I-6 and its preparation process, including the following steps:

[0075]

[0076] S1: In a 500 mL reaction flask equipped with nitrogen protection, mechanical stirring, thermometer, reflux condenser and tail gas absorption device, add 27.5 g (0.25 mol) of compound II-3 (2-hydroxyethylphosphonic acid), 200 mL of toluene, 1.0 g of p-toluenesulfonic acid and 15.4 g (0.14 mol) of dimethyl sulfite. Stir and heat to 85-88 °C and react for 5 h. Separate the by-product methanol from the water separator. After the reaction is complete, remove the solvent and low-boiling substances by vacuum distillation. Purify the crude product by column chromatography to obtain 21.3 g (0.08 mol) of compound V-3.

[0077] S2: In a 500mL reaction flask equipped with a magnetic stirrer, thermometer, and reflux condenser, add 21.3g (0.08mol) of compound V-3 prepared in step S1 and 200mL of dichloromethane. Stir to disperse thoroughly, cool to -2℃, and add 31.4g (0.28mol) of 30% hydrogen peroxide solution dropwise. After the addition is complete, keep the temperature at 0-5℃ and continue the reaction for 4h. Separate the liquid and liquid phases. Add sodium bisulfite to the aqueous phase to remove excess hydrogen peroxide, and distill the organic phase to remove dichloromethane. Purify the crude product by column chromatography to obtain 20.4g (0.065mol) of compound VI-3.

[0078] S3: In a 500ml reaction flask equipped with nitrogen protection, magnetic stirring, thermometer, reflux condenser, and tail gas absorption device, add 20.4g (0.065mol) of compound VI-3 prepared in step S2 and 121.2g (0.65mol) of tetramethyldivinyldisilazane. The mixture is heated to 130℃~135℃ and reacted for 40h. Excess tetramethyldivinyldisilazane is recovered by vacuum distillation using a water pump. The mixture is purified by column chromatography to obtain 31.6g of compound I-6 with a purity of 99.4%. The overall yield of the three steps is 38.9% (based on compound II-3).

[0079] II. Test Examples

[0080] Lithium-ion battery testing:

[0081] Test Example 1

[0082] Step 1: In a glove box filled with nitrogen or argon and containing ≤0.1ppm of both water and oxygen, mix ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7 to obtain a non-aqueous organic solvent mixture. Then, add lithium hexafluorophosphate to dissolve it and prepare a solution with a concentration of 1mol / L, which is the basic electrolyte.

[0083] Step 2: In a glove box filled with nitrogen or argon gas and containing ≤0.1ppm of both water and oxygen, add 1% by mass of compound I-1 obtained in Preparation Example 1, 0.5% by mass of VC, and 1% by mass of PS to the basic electrolyte and mix thoroughly to obtain the electrolyte to be tested.

[0084] Step 3: In a glove box filled with nitrogen or argon gas and containing ≤0.1ppm of both water and oxygen, inject the electrolyte to be tested into LiNi. 0.6 Co 0.2 Mn 0.2 In a pouch cell, O2 is used as the positive electrode material and artificial graphite as the negative electrode. After liquid injection, the cells are sealed and left to stand, undergo formation, aging, resealing, and capacity testing.

[0085] Step 4: Test the lithium-ion battery obtained in this test example for room temperature DC internal resistance, 45°C high temperature cycling and 60°C high temperature storage.

[0086] Test Example 2

[0087] The operation steps are the same as those in Test Example 1, except that in step 2, 1% of compound I-1 is replaced with 0.5% of compound I-2.

[0088] Test Example 3

[0089] The operation steps are the same as those in Test Example 1, except that in step 2, 1% of compound I-1 is replaced with 2% of compound I-2.

[0090] Test Example 4

[0091] The operation steps are the same as those in Test Example 1, except that in step 2, 1% of compound I-1 is replaced with 1% of compound I-6.

[0092] Comparative Example 1

[0093] The operation steps are the same as in Test Example 1, except that step 2 is not included.

[0094] Comparative Example 2

[0095] The procedure was the same as in Test Example 1, except that compound I-1 was not added in step 2.

[0096] Comparative Example 3

[0097] The operation steps are the same as those in Test Example 1, except that in step 2, 1% of compound I-1 is replaced with 1% of tris(trimethylsilyl)phosphate.

[0098] Comparative Example 4

[0099] The operation steps are the same as those in Test Example 1, except that in step 2, 1% of compound I-1 is replaced with 1% of vinyl sulfate.

[0100] Comparative Example 5

[0101] The operation steps are the same as those in Test Example 1, except that in step 2, 1% of compound I-1 is replaced with 1% of vinyl sulfate and 0.5% of tris(trimethylsilyl)phosphate.

[0102] Test Examples 1-4 and Comparative Examples 1-5 were subjected to room temperature DC internal resistance, 45°C high-temperature cycling, and 60°C high-temperature storage tests.

[0103] Room temperature DC internal resistance test: At 25℃, the lithium-ion batteries of Test Examples 1-4 and Comparative Examples 1-5 were charged to 4.5V at a constant current and constant voltage of 1C, with a cutoff current of 0.05C. They were then discharged to 3V at a constant current of 1C, and the discharge capacity Qt1 was recorded. They were then charged again to 4.5V at a constant current and constant voltage of 1C, with a cutoff current of 0.05C to fully charge. Then, 50% of the charge (Qt1) was discharged at a constant current of 1C. After standing for 1 hour, the voltage V1 was recorded. Finally, they were discharged at a constant current of 3Qt1 for 10 seconds, and the voltage V2 was recorded.

[0104] DC internal resistance (DCR) = (V1 - V2) / (3 * Qt1)

[0105] The room temperature DC internal resistance data for Test Examples 1-4 and Comparative Examples 1-5 are shown in Table 1 below:

[0106] Item DC internal resistance, mΩ Test Example 1 33.43 Test Example 2 34.12 Test Example 3 32.27 Test Example 4 33.98 Comparative Example 1 38.13 Comparative Example 2 39.53 Comparative Example 3 37.32 Comparative Example 4 35.78 Comparative Example 5 35.34

[0107] 45℃ High-Temperature Cycling Performance Test: At 45℃, the lithium-ion batteries of Test Examples 1-4 and Comparative Examples 1-5 were charged to 4.5V at a constant current of 1C, and then discharged to 3V at a constant current of 1C. After 600 charge-discharge cycles, the discharge capacity retention rate after the 600th cycle was calculated.

[0108] Discharge capacity retention rate (%) at 45℃ = (Discharge capacity after 600 cycles / Discharge capacity after the first cycle) * 100%

[0109] The 45℃ high-temperature cycling data for Test Examples 1-4 and Comparative Examples 1-5 are shown in Table 2 below:

[0110]

[0111]

[0112] 60℃ High-Temperature Storage Test: At 25℃, the lithium-ion batteries of Test Examples 1-4 and Comparative Examples 1-5 were charged to 4.5V at a constant current and constant voltage of 0.5C, with a cutoff current of 0.05C, and then discharged to 3V at a constant current of 0.5C. The discharge capacity was recorded, which is the initial discharge capacity. Then, the batteries were charged to 4.5V at a constant current and constant voltage of 0.5C, and the battery thickness was measured, which is the initial thickness. The fully charged batteries were placed in a constant temperature environment of 60℃ and stored for 7 days. After 7 days, they were removed and left to stand at 25℃ for 4 hours to cool to room temperature. The battery thickness was then measured, which is the thickness after storage. The batteries were discharged to 3V at a constant current of 0.5C, and the discharge capacity was recorded, which is the retained capacity. The batteries were charged to 4.5V at a constant current and constant voltage of 0.5C, with a cutoff current of 0.05C, and then discharged to 3V at a constant current of 0.5C, and the discharge capacity was recorded, which is the recovered capacity.

[0113] Battery capacity retention rate (%) = Retained capacity / Initial capacity * 100%

[0114] Battery capacity recovery rate (%) = Recovered capacity / Initial capacity * 100%

[0115] Thickness change rate (%) = (Thickness after storage - Initial thickness) / Initial thickness * 100%

[0116] The high-temperature storage data at 60℃ for Test Examples 1-4 and Comparative Examples 1-5 are shown in Table 3 below:

[0117]

[0118]

[0119] As can be seen from Tables 1-3, electrolytes containing trialkylsilylphosphonate sulfate exhibit lower DC internal resistance, better high-temperature cycle performance and high-temperature storage performance in lithium-ion batteries, and can better suppress gas expansion of lithium-ion batteries after high-temperature storage.

[0120] Sodium-ion battery test:

[0121] Test Example 5

[0122] Step 1: In a glove box filled with nitrogen or argon and containing ≤0.1ppm of both water and oxygen, mix ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 3:2:3:2 to obtain a non-aqueous organic solvent mixture. Then, add sodium hexafluorophosphate to dissolve it and prepare a solution with a concentration of 1mol / L, which is the basic electrolyte.

[0123] Step 2: In a glove box filled with nitrogen or argon gas and containing ≤0.1ppm of both water and oxygen, add 1% by mass of compound I-1 obtained in Preparation Example 1, 2% by mass of FEC, and 1% by mass of PST to the basic electrolyte and mix thoroughly to obtain the electrolyte to be tested.

[0124] Step 3: In a glove box filled with nitrogen or argon gas and containing ≤0.1ppm of both water and oxygen, inject the electrolyte to be tested into a solution of NaNi. 1 / 3 Fe 1 / 3 Mn 1 / 3 In a pouch cell, O2 is used as the positive electrode material and hard carbon as the negative electrode. After liquid injection, the cells are sealed and left to stand, undergo formation, aging, resealing, and capacity testing.

[0125] Step 4: Test the sodium-ion battery obtained in this test example for room temperature DC internal resistance, 45°C high-temperature cycling, and 60°C high-temperature storage.

[0126] Test Example 6

[0127] The operation steps are the same as those in Test Example 5, except that in step 2, 1% of compound I-1 is replaced with 1% of compound I-2.

[0128] Test Example 7

[0129] The operation steps are the same as those in Test Example 5, except that in step 2, 1% of compound I-1 was replaced with 1% of compound I-6.

[0130] Test Example 8

[0131] The operation steps are the same as those in Test Example 5, except that in step 2, 1% of compound I-1 was replaced with 2% of compound I-6.

[0132] Comparative Example 6

[0133] The operation steps are the same as in test example 5, except that step 2 is omitted.

[0134] Comparative Example 7

[0135] The procedure was the same as in test example 5, except that compound I-1 was not added in step 2.

[0136] Comparative Example 8

[0137] The operation procedure is the same as that in test example 5, except that in step 2, 1% of compound I-1 was replaced with 0.5% of tris(trimethylsilyl)phosphate.

[0138] Comparative Example 9

[0139] The operation steps are the same as those in Test Example 5, except that in step 2, 1% of compound I-1 is replaced with 1% of vinyl sulfate.

[0140] Comparative Example 10

[0141] The operation steps are the same as those in Test Example 5, except that in step 2, 1% of compound I-1 was replaced with 1% of vinyl sulfate and 0.5% of tris(trimethylsilyl)phosphate.

[0142] Test Examples 5-8 and Comparative Examples 6-10 were subjected to room temperature DC internal resistance, 45°C high-temperature cycling, and 60°C high-temperature storage tests.

[0143] Room temperature DC internal resistance test: At 25℃, the sodium-ion batteries of Test Example 5-8 and Comparative Example 6-10 were charged to 4V at a constant current and constant voltage of 1C, with a cutoff current of 0.05C. They were then discharged to 2V at a constant current of 1C, and the discharge capacity Qt2 was recorded. They were then charged again to 4V at a constant current and constant voltage of 1C, with a cutoff current of 0.05C, and 50% of Qt2 of the charge was discharged at a constant current of 1C. After standing for 1 hour, the voltage V3 was recorded. Finally, they were discharged at a constant current of 3Qt for 10 seconds, and the voltage V4 was recorded.

[0144] Discharge DC internal resistance (DCR) = (V3 - V4) / (3 * Qt2)

[0145] The room temperature DC internal resistance data for Test Examples 5-8 and Comparative Examples 6-10 are shown in Table 4 below:

[0146]

[0147]

[0148] High-temperature cycling performance test at 45℃: The sodium-ion batteries of Test Examples 5-8 and Comparative Examples 6-10 were charged to 4V at a constant current of 1C at 45℃, and then discharged to 2V at a constant current of 1C. After 200 charge-discharge cycles, the discharge capacity retention rate after the 200th cycle was calculated.

[0149] Discharge capacity retention rate (%) at 45℃ = (Discharge capacity after 200 cycles / Discharge capacity after the first cycle) * 100%

[0150] The high-temperature cycling data at 45℃ for Test Examples 5-8 and Comparative Examples 6-10 are shown in Table 5 below:

[0151] Item Discharge capacity retention rate at 45°C, % Test Example 5 83.45 Test Example 6 81.34 Test Example 7 84.23 Test Example 8 85.85 Comparative Example 6 64.98 Comparative Example 7 68.47 Comparative Example 8 70.12 Comparative Example 9 76.75 Comparative Example 10 76.12

[0152] 60℃ High-Temperature Storage Test: At 25℃, the sodium-ion batteries of Test Examples 5-8 and Comparative Examples 6-10 were charged to 4V at a constant current and constant voltage of 0.5C, with a cutoff current of 0.05C, and then discharged to 2V at a constant current of 0.5C. The discharge capacity was recorded, which is the initial discharge capacity. Then, the batteries were charged to 4V at a constant current and constant voltage of 0.5C, and the battery thickness was measured, which is the initial thickness. The fully charged batteries were placed in a constant temperature environment of 60℃ and stored for 7 days. After 7 days, they were removed and left to stand at 25℃ for 4 hours to cool to room temperature. The battery thickness was then measured, which is the thickness after storage. The batteries were discharged to 2V at a constant current of 0.5C, and the discharge capacity was recorded, which is the retained capacity. The batteries were charged to 4V at a constant current and constant voltage of 0.5C, with a cutoff current of 0.05C, and then discharged to 2V at a constant current of 0.5C, and the discharge capacity was recorded, which is the recovered capacity.

[0153] Battery capacity retention rate (%) = Retained capacity / Initial capacity * 100%

[0154] Battery capacity recovery rate (%) = Recovered capacity / Initial capacity * 100%

[0155] Thickness change rate (%) = (Thickness after storage - Initial thickness) / Initial thickness * 100%

[0156] The high-temperature storage data at 60℃ for Test Examples 5-8 and Comparative Examples 6-10 are shown in Table 6 below:

[0157]

[0158]

[0159] As can be seen from Tables 4-6, electrolytes containing trialkylsilylphosphonate sulfates also exhibit lower DC internal resistance, better high-temperature cycle performance and high-temperature storage performance in sodium-ion batteries, while also suppressing gas expansion of sodium-ion batteries after high-temperature storage.

[0160] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. The above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A secondary battery electrolyte containing trialkylsilylphosphonate sulfate, characterized in that, The electrolyte comprises trialkylsilylphosphonate sulfate, an electrolyte salt, a non-aqueous organic solvent, and other additives; the general structural formula of the trialkylsilylphosphonate sulfate compound I is as follows: Where n is 1, 2, or 3; R1, R2, and R3 are selected from one of the hydrocarbon groups from C1 to C6.

2. The secondary battery electrolyte containing trialkylsilylphosphonate sulfate according to claim 1, characterized in that, The other additives are selected from at least one of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), vinyl sulfite (ES), methylene disulfonate (MMDS), 1,3-propanesulfonate lactone (PS), 1,3-propenesulfonate lactone (PST), tris(trimethylsilyl)phosphite (TMSPi), tris(trimethylsilyl)borate (TMSB), succinic anhydride (SA), succinic anhydride (SN), adiponitrile (ADN), and ethoxypentafluorocyclotriphosphazene (PFPN).

3. The secondary battery electrolyte containing trialkylsilylphosphonate sulfate according to claim 1, characterized in that, The amount of the trihydrosilylphosphonate sulfate compound additive is 0.1% to 5% of the total mass of the electrolyte, and the amount of other additives is 0.1% to 5%.

4. The secondary battery electrolyte containing trialkylsilylphosphonate sulfate according to claim 1, characterized in that, When the secondary battery is a lithium-ion battery, the electrolyte in the electrolyte solution is one or more of the following: lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorophosphate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(oxalate borate), lithium difluorooxalate borate, lithium tetrafluorooxalate phosphate, lithium difluorobis(oxalate borate), and lithium fluorosulfonyl(trifluoromethanesulfonyl)imide, and the molar concentration of the electrolyte in the electrolyte solution is 0.5–2 mol / L; when the secondary battery is a sodium-ion battery, the electrolyte in the electrolyte solution is sodium hexafluorophosphate, sodium difluorophosphate, sodium bis(oxalate borate), and lithium fluorosulfonyl(trifluoromethanesulfonyl)imide. Sodium fluoxetate borate, sodium difluorosulfonamide, sodium bis(trifluoromethylsulfonamide) sodium, sodium trifluoromethylsulfonate, sodium perchlorate, and sodium tetrafluoroborate; wherein the non-aqueous organic solvent comprises one or more of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethylene carbonate, methyl ethyl carbonate, methyl propyl carbonate, methyl butyl carbonate, propylene carbonate, γ-butyrolactone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, difluoroethyl acetate, trifluoroethyl acetate, trifluoroethyl methyl carbonate, and bis(trifluoroethyl) carbonate.

5. A trialkylsilylphosphonate sulfate compound, characterized in that, The general structural formula of the trihydrosilylphosphonate sulfate compound I is as follows: Where n is 1, 2, or 3; R1, R2, and R3 are selected from one of the hydrocarbon groups from C1 to C6.

6. A preparation process for the trialkylsilylphosphonate sulfate compound as described in claim 5, characterized in that: The preparation process of the trialkylsilylphosphonate sulfate compound I consists of three steps: S1: When compound II reacts with compound III-a, wherein X in compound III-a is selected from Br or Cl, compound IV is obtained; compound IV is hydrolyzed to obtain compound V; the reaction formula is as follows: Wherein, R is selected from hydrogen atoms or C1 to C4 alkyl groups; n is 1, 2, or 3; m takes the value 0 or 1; or When compound II reacts with compound III-b, where Y in compound III-b is selected from C1 to C4 alkyl groups, compound V is directly obtained without a hydrolysis step, as shown in the following reaction formula: S2: Compound V is oxidized to give compound VI, as shown in reaction II below: S3: Compound VI reacts with a trialkylsilyl compound to give the final product compound I, as shown in reaction formula III below:

7. The preparation process of a trialkylsilylphosphonate sulfate compound according to claim 6, characterized in that: In step S1, compound III-a is thionyl chloride, and compound III-b is selected from dimethyl sulfite and diethyl sulfite; the molar ratio of compound III to compound II is 2.0 to 5.0:1, and the reaction temperature is -20 to 40°C.

8. The preparation process of a trialkylsilylphosphonate sulfate compound according to claim 7, characterized in that: In step S1, the solvent for the reaction of compound II and compound III is at least one of alkanes, halogenated hydrocarbons, esters, and sulfones, specifically selected from at least one of benzene, toluene, xylene, cyclohexane, cyclopentane, dichloromethane, chloroform, ethyl acetate, butyl acetate, dimethyl carbonate, diethyl carbonate, dimethyl sulfoxide, and sulfolane.

9. The preparation process of a trialkylsilylphosphonate sulfate compound according to claim 6, characterized in that: In step S2, compound V is oxidized to obtain compound VI. The oxidant used is selected from one of hydrogen peroxide, ozone, hypochlorous acid, oxygen, air, sodium hypochlorite, ammonium persulfate, potassium persulfate, potassium perhydrosulfate, peroxysulfuric acid, sodium percarbonate, sodium perchlorate, sodium periodate, manganese oxide, and potassium permanganate.

10. The preparation process of a trialkylsilylphosphonate sulfate compound according to claim 9, characterized in that: In step S2, the reaction solvent is selected from organic solvents or water; the molar ratio of active oxygen provided by the oxidant to compound V is 3.0 to 6.0:1; and the reaction temperature is -20 to 60°C.

11. The preparation process of a trialkylsilylphosphonate sulfate compound according to claim 6, characterized in that: In step S3, the molar ratio of the trialkylsilyl compound to compound VI is 2–20:1, the reaction temperature is -10–160°C, and the reaction time is 1–40 h; the trialkylsilyl compound is selected from one of trialkylsilazane, trialkylsiloxane, or trialkylhalosilane.

12. The preparation process of a trialkylsilylphosphonate sulfate compound according to claim 11, characterized in that: The trialkylsilyl compound is selected from at least one of hexaalkyldisilazane, hexaalkyldisilaurea, heptaalkyldisilamine, trialkylchlorosilane, trialkylalkyloxysilane, trialkylacyloxysilane, trialkylsilylamine, trialkylsilylimidazolium, trialkylamineoxysilane, trialkylalkenyloxysilane, trialkyloximesilane, or N,O-bistrialkylsilylacetamide.

13. The preparation process of a trialkylsilylphosphonate sulfate compound according to claim 12, characterized in that: The trialkylsilane compound is selected from at least one of trimethylchlorosilane, hexamethyldisilazane, heptamethyldisilazane, tetramethyldivinyldisilazane, trimethylmethoxysilane, trimethylethoxysilane, trimethylsilylimidazolium, hexamethyldisilazane, or N,O-bistrimethylsilylacetamide, tetramethylbis(trifluoromethyl)disiloxane, tetraisopropyldicyanodisiloxane, and tetramethyl-bis(3-cyanopropyl)disilazane.

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