Application of 2-mercaptothiazoline compound in solid-state lithium ion battery, solid-state lithium ion battery electrolyte and preparation method of solid-state lithium ion battery electrolyte

Abstract

The invention discloses an application of a 2-mercaptothiazoline compound in a solid-state lithium ion battery electrolyte, the solid-state lithium ion battery electrolyte and a preparation method of the solid-state lithium ion battery electrolyte, the structure of the 2-mercaptothiazoline compound is as follows: # imgabs0 #, R1 is amido, methyl ester group, pyridyl or H atom; r2 is an acetyl group, a methoxyl group, a sulfonic group, a sulfydryl group or an H atom; and R3 is phenyl or H atom. According to the invention, the 2-mercaptothiazoline compound is adopted as an additive of the solid-state lithium ion battery electrolyte, and a functional group of the 2-mercaptothiazoline compound and Li < + > can form a weak coordinate bond to construct a flexible ion transmission channel, so that repeated side reactions in electrolyte salt are inhibited, the high-temperature performance of the battery is improved, and the cycle performance and rate capability of the battery are further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state lithium-ion batteries, and specifically relates to the application of 2-mercapto-thiazoline compounds in solid-state lithium-ion battery electrolytes, solid-state lithium-ion battery electrolytes and their preparation methods. Background Art

[0002] As a new generation of energy storage technology, solid-state lithium-ion batteries show broad application prospects in fields such as electric vehicles, smart grids, and portable electronic devices, and are considered one of the most promising technologies to replace traditional liquid lithium-ion batteries. However, the existing solid electrolyte systems still face significant challenges in terms of high-temperature cycle stability and rate performance.

[0003] Polymer solid electrolytes (such as polyethylene oxide PEO) have good flexibility and processability, but are prone to molecular chain rearrangement at high temperatures, resulting in a decrease in the stability of the electrolyte-electrode interface. At the same time, their own thermal stability is insufficient, which further exacerbates the capacity attenuation during high-temperature cycling, and the high-temperature cycle performance is poor. In addition, for traditional polymer electrolytes at high current densities ≥2C, their charge-discharge efficiency is significantly reduced, it is difficult to maintain high rate performance, and they cannot meet the requirements of high-power devices. Summary of the Invention

[0004] The purpose of the present invention is to provide the application of 2-mercapto-thiazoline compounds in solid-state lithium-ion battery electrolytes, solid-state lithium-ion battery electrolytes and their preparation methods. The present invention uses 2-mercapto-thiazoline compounds as additives for solid-state lithium-ion battery electrolytes to improve the high-temperature cycle performance and rate performance of solid-state lithium-ion batteries.

[0005] To solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0006] The application of a 2-mercapto-thiazoline compound in a solid-state lithium-ion battery electrolyte, and the structure of the 2-mercapto-thiazoline compound is as follows:

[0007]

[0008] Wherein, R1 is an amide group, a methyl ester group, a pyridyl group or an H atom; R2 is an acetyl group, a methoxy group, a sulfonic acid group, a mercapto group or an H atom; R3 is a phenyl group or an H atom.

[0009] The present invention uses 2-mercapto-thiazoline compounds as functional additives for solid-state lithium-ion battery electrolytes. The functional groups of 2-mercapto-thiazoline compounds can form weak coordination bonds with Li + to construct a flexible ion transport channel, thereby inhibiting the side reactions repeatedly occurring in the electrolyte salt, improving the high-temperature performance of the battery, and further improving the cycle performance and rate performance of the battery.

[0010] To further improve the cycling performance of the battery, the 2-mercapto thiazoline compounds are preferably at least one of 4-acetyl-5-formamido-2-mercapto thiazoline, 4-methoxy-5-methylester-2-mercapto thiazoline, 4-phenyl-5-oxo-2-mercapto thiazoline, 3-sulfo-2,5-dimercapto-4-(pyridin-3-yl) thiazoline, 2-mercapto thiazoline, 5-oxo-2-mercapto thiazoline or 2,4-dimercapto thiazoline. Further preferably, the 2-mercapto thiazoline compounds are at least one of 4-acetyl-5-formamido-2-mercapto thiazoline, 2,4-dimercapto thiazoline, 4-methoxy-5-methylester-2-mercapto thiazoline or 3-sulfo-2,5-dimercapto-4-(pyridin-3-yl) thiazoline. More preferably, the 2-mercapto thiazoline compounds are at least one of 4-acetyl-5-formamido-2-mercapto thiazoline or 2,4-dimercapto thiazoline, and most preferably 4-acetyl-5-formamido-2-mercapto thiazoline.

[0011] A solid-state lithium-ion battery electrolyte comprises 44-50% of a lithium salt, 47-53% of a polymer matrix, 0.1-0.5% of a 2-mercapto thiazoline compound, and 2-3% of a film-forming additive, and the aforesaid percentages are by mass. The sum of the masses of the aforesaid components is 100%.

[0012] Unless otherwise specified in this application, all are by mass percentage.

[0013] In this application, the dosage of the 2-mercapto thiazoline compounds is not the more the better. It was found in the experiments of the invention that when the dosage is too much, not only the cost will be high, but also the battery performance will show an obvious downward trend. The dosage of the 2-mercapto thiazoline compounds in this application is more preferably 0.2-0.3%.

[0014] The aforesaid lithium salt includes at least one of lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium difluorophosphate, lithium difluorobis(oxalato)phosphate, lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium methanesulfonate, lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide or lithium bis(trifluoromethylsulfonyl)imide.

[0015] The aforesaid polymer matrix includes at least one of polyethylene oxide (PEO), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), polypropylene oxide (PPO), polyvinylidene chloride (PVDC) and single-ion polymer electrolytes.

[0016] The aforesaid film-forming additive includes at least one of lithium bis(fluorosulfonyl)imide, lithium difluoroborate, vinylene carbonate, 1,3-propane sultone, 1,4-butane sultone, acrylic lactone, ethylene ethylene carbonate, fluoroethylene carbonate or N-acetylcaprolactam.

[0017] As one of the preferred solutions, when preparing the solid-state lithium-ion battery electrolyte, the lithium salt used is lithium bis(trifluoromethanesulfonyl)imide, the polymer matrix is polyethylene oxide, and the film-forming additive is lithium difluoromethanesulfonylimide.

[0018] The preparation method of the above-mentioned solid-state lithium-ion battery electrolyte includes the following steps:

[0019] (1) In a glove box filled with argon (to prevent interference from moisture and oxygen), the weighed polymer matrix and lithium salt are added to an organic solvent, and stirred at 50-60 °C until the polyethylene oxide is completely dissolved to form a homogeneous solution, obtaining a basic solution;

[0020] (2) Add the 2-mercapto-thiazoline compound and the film-forming additive to the basic solution obtained in step (1), and stir evenly;

[0021] (3) Pour the solution obtained in (2) onto a clean flat mold, control the film thickness by the doctor blade method, place the coated mold in a vacuum drying oven, and dry at 40-50 °C for 12-24 hours to allow the organic solvent to volatilize sufficiently, forming a solid electrolyte membrane.

[0022] In the above step (1), the organic solvent is acetonitrile.

[0023] For the technologies not mentioned in the present invention, refer to the prior art.

[0024] The present invention uses the 2-mercapto-thiazoline compound as an additive for the solid-state lithium-ion battery electrolyte, and its functional group can form a weak coordination bond with Li + to construct a flexible ion transport channel, thereby suppressing the side reactions repeatedly occurring in the electrolyte salt, improving the high-temperature performance of the battery, and further improving the cycle performance and rate performance of the battery. Description of the Drawings

[0025] Figure 1 is a physical photo of the solid electrolyte membrane of the present invention;

[0026] Figure 2 is the high-temperature cycle performance graph of Example 2 of the present invention; Detailed Description of the Invention

[0027] To better understand the present invention, the content of the present invention will be further clarified below in conjunction with embodiments, but the content of the present invention is not limited to the following embodiments.

[0028] The present invention provides an application of a 2-mercapto-thiazoline compound in a solid-state lithium-ion battery electrolyte, and the 2-mercapto-thiazoline compound has the following structure:

[0029]

[0030] Among them, R1 is an amide group, a methyl ester group, a pyridyl group or an H atom; R2 is an acetyl group, a methoxy group, a sulfonic acid group, a mercapto group or an H atom; R3 is a phenyl group or an H atom.

[0031] In the present invention, unless otherwise specified, all the preparation raw materials are preferably commercially available products well-known to those skilled in the art or prepared by methods well-known to those skilled in the art.

[0032] In the present invention, the heterocycle is preferably thiazoline containing a sulfur-nitrogen heterocyclic structure.

[0033] In the present invention, when R1 to R3 are preferably H atoms, the 2-mercapto thiazoline compounds are preferably 2-mercapto thiazoline, 5-oxo-2-mercapto thiazoline.

[0034] In the present invention, when R1 is preferably an H atom and R2 is preferably a mercapto group, the 2-mercapto thiazoline compounds are preferably 2,4-dimercapto thiazoline.

[0035] In the present invention, when R1 is preferably an amide group, a methyl ester group or a pyridyl group, R2 is preferably an acetyl group, a methoxy group or a sulfonic acid group, and R3 is preferably a phenyl group, the 2-mercapto thiazoline compounds are preferably 4-acetyl-5-formamido-2-mercapto thiazoline, 4-methoxy-5-methyl ester-2-mercapto thiazoline, 3-sulfonic acid group-2,5-dimercapto-4-(pyridin-3-yl) thiazoline or 4-phenyl-5-oxo-2-mercapto thiazoline.

[0036] The present invention also provides a solid-state lithium-ion battery electrolyte, comprising a lithium salt, a polymer matrix and a 2-mercapto thiazoline compound; the 2-mercapto thiazoline compound has the following structure:

[0037]

[0038] Among them, R1 may be an amide group, a methyl ester group, a pyridyl group, then R2 is an acetyl group, a methoxy group, a sulfonic acid group, and R3 is a phenyl group; or R1 to R3 are independently H atoms; or R1 is an H atom and R2 is a mercapto group.

[0039] In the present invention, the lithium salt preferably includes one or more of lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium difluorophosphate, lithium bis(oxalato)difluorophosphate, lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium methanesulfonate, lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethylsulfonyl)imide. More preferably, it is lithium bis(trifluoromethylsulfonyl)imide. In the present invention, the concentration of the lithium salt is preferably 1 M.

[0040] In the present invention, the polymer matrix preferably includes one or more of polyethylene oxide (PEO), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), polypropylene oxide (PPO), polyvinylidene chloride (PVDC), and single-ion polymer electrolytes. More preferably, it is polyethylene oxide.

[0041] In the present invention, the mass ratio of the lithium salt, 2-mercapto thiazoline compound, and polymer matrix is preferably 20 - 50%: 0.1 - 1%: 50 - 70%, and more preferably 35.5%: 0.3%: 64.2%.

[0042] In the present invention, the solid-state lithium-ion battery electrolyte further includes a film-forming additive. In the present invention, the film-forming additive preferably includes one or more of lithium bis(fluorosulfonyl)imide, lithium difluoroborate, vinylene carbonate, 1,3-propane sultone, 1,4-butane sultone, acrylic lactone, ethylene vinyl carbonate, fluoroethylene carbonate, and N-acetylcaprolactam. More preferably, it is vinylene carbonate. The content of the film-forming additive is 0.5 - 5% of the total mass of the solid-state lithium-ion battery electrolyte, and more preferably 1%.

[0043] The present invention also provides a preparation method of the solid-state lithium-ion battery electrolyte described in the above technical solution, including the following steps:

[0044] (1) In a glove box filled with argon (to prevent interference from moisture and oxygen), the weighed polyethylene oxide and lithium bis(trifluoromethylsulfonyl)imide are slowly added to an organic solvent and stirred at 50 - 60 °C until the polyethylene oxide is completely dissolved to form a homogeneous solution.

[0045] (2) A 2-mercapto thiazoline compound and a film-forming additive (15% by mass of lithium bis(trifluoromethanesulfonyl)imide) with a mass of 0.1 - 1% of the total mass of the electrolyte are added to the basic solution obtained in step (1) and stirred evenly.

[0046] (3) The solution obtained in (2) is poured onto a clean flat mold, and the thickness of the film is controlled by the doctor blade method. The coated mold is placed in a vacuum drying oven and dried at 40 - 50 °C for 12 - 24 hours to allow the organic solvent to volatilize fully, forming a solid electrolyte film.

[0047] To further illustrate the present invention, the application of 2-mercapto-thiazoline compounds provided by the present invention in solid-state lithium-ion battery electrolytes and the solid-state lithium-ion battery electrolytes will be described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0048] In each example, unless otherwise specified, the operations are carried out at room temperature (20 - 25 °C); unless otherwise specified, the stirring speed is 200 r / min.

[0049] Each 2-mercapto-thiazoline compound is prepared according to the following method, and the ratio between the solvents involved in each example is a volume ratio.

[0050] Preparation Example 1

[0051] Preparation of 4-acetyl-5-formamido-2-mercapto-thiazoline:

[0052] (1) Dissolve 2-mercapto-thiazoline (1 mol) in 400 ml of anhydrous tetrahydrofuran, and dropwise add triethylamine (1.2 mol) and trimethylchlorosilane (TMSCl, 1.1 mol) at a rate of 45 drops / min under an ice bath condition. After the addition is completed, raise the temperature to room temperature and stir the reaction for 2 hours. Distill off the solvent from the obtained reaction solution under reduced pressure to obtain a crude product, and purify the crude product by column chromatography (silica gel, petroleum ether / ethyl acetate = 3:1) to obtain 2-(trimethylsilylthio)thiazoline.

[0053] (2) Dissolve 2-(trimethylsilylthio)thiazoline (1 mol) in 500 ml of dichloromethane, add triethylamine (1.5 mol), and dropwise add formyl chloride (1.2 mol) at a rate of 45 drops / min under an ice bath. After the addition is completed, react at room temperature for 6 hours, filter, wash with 3% (mass concentration) dilute hydrochloric acid, dry with anhydrous sodium sulfate, distill off the solvent, and purify by recrystallization to obtain 5-formamido-2-(trimethylsilylthio)thiazoline.

[0054] (3) Dissolve 5-formamido-2-(trimethylsilylthio)thiazoline (1 mol) in 500 ml of acetonitrile, add aluminum chloride (13.3 g), and dropwise add acetyl chloride (1.2 mol) at a rate of 45 drops / min. Heat under reflux and react for 8 hours. Cool the reaction solution to room temperature, pour it into ice water for quenching, extract with ethyl acetate, combine the organic phases, dry and then distill and concentrate. Separate by column chromatography (silica gel, dichloromethane / methanol = 10:1) to obtain 4-acetyl-5-formamido-2-(trimethylsilylthio)thiazoline.

[0055] (4) Dissolve 4-acetyl-5-formamido-2-(trimethylsilylthio)thiazoline (1 mol) in 300 ml of methanol, add 2 L of dilute hydrochloric acid (1 M), and stir the reaction at room temperature for 5 hours. Remove the trimethylsilyl protecting group to restore the mercapto group. Adjust the reaction solution to neutral with saturated sodium bicarbonate solution, distill off the solvent under reduced pressure, and finally obtain the target product 4-acetyl-5-formamido-2-mercapto-thiazoline by recrystallization (ethanol / water 1:1 mixed solvent).

[0056] Preparation Example 2

[0057] Preparation of 4-methoxy-5-methyl carboxyl-2-mercapto-thiazoline:

[0058] (1) Dissolve 2-mercapto-thiazoline (1 mol) in 400 ml of anhydrous tetrahydrofuran (THF), and dropwise add triethylamine (1.2 mol) and trimethylchlorosilane (TMSCl, 1.1 mol) at a rate of 45 drops / min under an ice bath. After the addition is complete, warm the mixture to room temperature and stir the reaction for 2 hours. Distill off the solvent from the resulting reaction solution under reduced pressure to obtain a crude product, and purify the crude product by column chromatography (silica gel, petroleum ether / ethyl acetate = 4:1) to obtain 2-(trimethylsilylthio)thiazoline.

[0059] (2) Dissolve 2-(trimethylsilylthio)thiazoline (1 mol) in 500 ml of dry DMF, add sodium hydride (NaH, 1.5 mol, 60 wt% mineral oil dispersion), and stir at an ice bath for 30 minutes for activation. Dropwise add methyl formate (1.2 mol) at a rate of 45 drops / min, and react at room temperature for 7 hours (monitored by TLC). Pour the reaction solution into ice water to quench it, extract with ethyl acetate (3 × 50 mL), combine the organic phases, dry over anhydrous sodium sulfate, distill and concentrate, and recrystallize (ethanol / water 1:1) to obtain 5-methyl carboxyl-2-(trimethylsilylthio)thiazoline.

[0060] (3) Dissolve 5-methyl carboxyl-2-(trimethylsilylthio)thiazoline (1 mol) in 500 ml of acetonitrile, add N-bromosuccinimide (NBS, 1.2 mol) and azobisisobutyronitrile (AIBN, 8.2 g), and heat and reflux the reaction in the dark for 5 hours. Cool the reaction solution, filter off the by-products, distill and concentrate, and separate by column chromatography (silica gel, dichloromethane / methanol = 15:1) to obtain 4-bromo-5-methyl carboxyl-2-(trimethylsilylthio)thiazoline.

[0061] Dissolve 4-bromo-5-methoxycarbonyl-2-(trimethylsilylthio)thiazoline (1 mol) in 300 ml of methanol, add sodium methoxide (2.0 mol), and reflux the reaction mixture at 60 °C for 8 hours. The bromine atom is substituted by a methoxy group. The resulting reaction solution is neutralized to pH = 7 with 5% (mass concentration) dilute hydrochloric acid, and methanol is removed by distillation under reduced pressure. The residue is extracted with ethyl acetate, dried, distilled and concentrated, and purified by column chromatography (silica gel, petroleum ether / ethyl acetate = 2:1).

[0062] (4) Dissolve the above product (1 mol) in 300 ml of methanol, add 2 L of dilute hydrochloric acid (1 M), and stir the reaction mixture at room temperature for 4 hours. The trimethylsilyl protecting group is hydrolyzed to restore the mercapto group. The reaction solution is adjusted to neutral with saturated sodium bicarbonate solution, and the solvent is removed by distillation under reduced pressure. Finally, the target product 4-methoxy-5-methoxycarbonyl-2-mercapto-thiazoline is obtained by recrystallization (ethanol / water mixed solvent 1:1).

[0063] Preparation Example 3

[0064] Preparation of 4-phenyl-5-oxo-2-mercapto-thiazoline:

[0065] (1) Dissolve 2-mercapto-thiazoline (1 mol) in 400 ml of anhydrous tetrahydrofuran (THF), and dropwise add triethylamine (1.2 mol) and trimethylchlorosilane (TMSCl, 1.1 mol) at a rate of 45 drops / min under an ice bath. After the addition is complete, the temperature is raised to room temperature, and the reaction mixture is stirred for 2 hours. The resulting reaction solution is distilled under reduced pressure to remove the solvent to obtain a crude product, and the crude product is purified by column chromatography (silica gel, petroleum ether / ethyl acetate = 4:1) to obtain 2-(trimethylsilylthio)thiazoline.

[0066] (2) Dissolve 2-(trimethylsilylthio)thiazoline (1 mol) in 500 m of anhydrous DMF, add sodium hydride (NaH, 1.5 mol, 60 wt% mineral oil dispersion), and stir in an ice bath for 30 minutes for activation. Dropwise add ethyl acetate (1.2 mol) at a rate of 45 drops / min, and react at room temperature for 6 hours (monitored by TLC). Pour the reaction solution into ice water to quench it, extract with ethyl acetate (3 × 50 mL), combine the organic phases, dry over anhydrous sodium sulfate, distill and concentrate, and recrystallize (ethanol / water 1:1) to obtain 5-acetyl-2-(trimethylsilylthio)thiazoline.

[0067] (3) Dissolve 5-acetyl-2-(trimethylsilylthio)thiazoline (1 mol) in 500 ml of dichloromethane, add aluminum trichloride (AlCl3, 1.2 mol), and dropwise add benzoyl chloride (1.1 mol) at a rate of 45 drops / min under an ice bath. After the addition is complete, raise the temperature to 40 °C and react for 8 hours. Pour the reaction solution into ice-cold hydrochloric acid to quench, extract with dichloromethane, dry, and then distill and concentrate. Separate by column chromatography (silica gel, dichloromethane / methanol = 20:1) to obtain 4-benzoyl-5-acetyl-2-(trimethylsilylthio)thiazoline.

[0068] Dissolve 4-benzoyl-5-acetyl-2-(trimethylsilylthio)thiazoline (1 mol) in 500 ml of methanol, add potassium hydroxide (2.0 mol), and heat under reflux for 5 hours to hydrolyze the benzoyl group to a keto group. Neutralize the reaction solution with 5% dilute hydrochloric acid to pH = 7, distill off methanol under reduced pressure, extract the residue with ethyl acetate, dry, and then distill and concentrate. Purify by column chromatography (silica gel, petroleum ether / ethyl acetate = 2:1).

[0069] (4) Dissolve the above product (1 mol) in 300 ml of methanol, add 2 L of dilute hydrochloric acid (1 M), stir at room temperature for 4 hours to hydrolyze the trimethylsilyl protecting group and restore the mercapto group. Adjust the reaction solution to neutral with saturated sodium bicarbonate solution, distill off the solvent under reduced pressure, and finally obtain the target product 4-phenyl-5-oxo-2-mercapto-thiazoline by recrystallization (ethanol / water 1:1 mixed solvent).

[0070] Preparation Example 4

[0071] Preparation of 3-sulfo-2,5-dimercapto-4-(pyridin-3-yl)thiazoline:

[0072] (1) Dissolve 2-mercapto-thiazoline (1 mol) in 100 ml of anhydrous DMF, add potassium carbonate (2.0 mol) and methyl iodide (1.2 mol), and stir at room temperature for 5 hours to form 2-methylthio-thiazoline. Dissolve 2-methylthio-thiazoline (1 mol) in 150 ml of dichloromethane, add N-bromosuccinimide (NBS, 1.2 mol) and AIBN (azobisisobutyronitrile, 3 g), and heat under reflux in the dark for 6 hours to form 4-bromo-2-methylthio-thiazoline.

[0073] (2) Dissolve 4-bromo-2-(methylthio)thiazoline (1 mol) in 200 ml of toluene, add pyridin-3-ylboronic acid (1.5 mol), potassium carbonate (2.0 mol) and tetrakis(triphenylphosphine)palladium (Pd(PPh3)4, 0.05 mol), heat to 100 °C under argon protection and react for 12 hours. Introduce the pyridyl group through Suzuki coupling, then filter the reaction solution and concentrate it under reduced pressure. Separate by column chromatography (silica gel, dichloromethane / methanol = 20:1) to obtain 4-(pyridin-3-yl)-2-(methylthio)thiazoline.

[0074] (3) Dissolve 4-(pyridin-3-yl)-2-(methylthio)thiazoline (1 mol) in 200 ml of carbon tetrachloride, add NBS (1.2 mol) under ice bath, and react in the dark for 2 - 4 hours to form 5-bromo-4-(pyridin-3-yl)-2-(methylthio)thiazoline. Then dissolve 5-bromo-4-(pyridin-3-yl)-2-(methylthio)thiazoline (1 mol) in 150 ml of ethanol, add sodium hydrosulfide (NaHS, 2.0 mol), heat under reflux for 8 hours. After the reaction solution is cooled, concentrate it under reduced pressure, and purify by column chromatography (silica gel, dichloromethane / methanol = 10:1) to obtain 5-mercapto-4-(pyridin-3-yl)-2-(methylthio)thiazoline.

[0075] (4) Dissolve 5-mercapto-4-(pyridin-3-yl)-2-(methylthio)thiazoline (1 mol) in 100 ml of concentrated sulfuric acid (mass concentration 98%), slowly add 1.5 mol of 20% oleum (containing SO3) dropwise at a rate of 1 drop / second under ice bath, react at room temperature for 2 hours to introduce a sulfonic acid group at the 3-position to obtain a sulfonic acid group product. Dissolve the sulfonic acid group product (1 mol) in 100 ml of methanol, add 100 ml of concentrated hydrochloric acid (12 M), heat under reflux for 6 hours to remove the methylthio protecting group and restore the mercapto group at the 2-position. Concentrate the reaction solution under reduced pressure, add saturated sodium bicarbonate solution for neutralization, filter and then freeze-dry to obtain the target product 3-sulfonic acid group-2,5-dimercapto-4-(pyridin-3-yl)thiazoline.

[0076] Preparation Example 5

[0077] Preparation of 5-oxo-2-mercapto-thiazoline:

[0078] (1) Dissolve 2-mercapto-thiazoline (1 mol) in 400 ml of anhydrous tetrahydrofuran (THF), dropwise add triethylamine (1.2 mol) and trimethylchlorosilane (TMSCl, 1.1 mol) at a rate of 45 drops / min under ice bath. After dropping, warm to room temperature and stir for 2 hours. Distill off the solvent from the obtained reaction solution under reduced pressure to obtain a crude product, and purify the crude product by column chromatography (silica gel, petroleum ether / ethyl acetate = 4:1) to obtain 2-(trimethylsilylthio)thiazoline.

[0079] (2) Dissolve 2-(trimethylsilylthio)thiazoline (1 mol) in 500 ml of anhydrous DMF, add sodium hydride (NaH, 1.5 mol, 60 wt% mineral oil dispersion), and stir in an ice bath for 30 minutes for activation. Dropwise add ethyl acetate (1.2 mol) at a rate of 45 drops / min, react at room temperature for 6 hours (monitored by TLC), pour the resulting reaction solution into ice water for quenching, extract with ethyl acetate (3×50 mL), combine the organic phases, dry over anhydrous sodium sulfate, distill and concentrate, and then recrystallize (ethanol / water) to obtain 5-acetyl-2-(trimethylsilylthio)thiazoline.

[0080] (3) Dissolve 5-acetyl-2-(trimethylsilylthio)thiazoline (1 mol) in 300 ml of methanol, add 2 L of dilute hydrochloric acid (1 M), and stir and react at room temperature for 5 hours to form the target product 5-oxo-2-mercapto-thiazoline.

[0081] Preparation Example 6

[0082] Preparation of 2,4-dimercapto-thiazoline:

[0083] (1) Dissolve 2-mercapto-thiazoline (1 mol) in 400 ml of anhydrous tetrahydrofuran (THF), dropwise add triethylamine (1.2 mol) and trimethylchlorosilane (TMSCl, 1.1 mol) at a rate of 45 drops / min under an ice bath. After the addition is complete, warm up to room temperature and stir and react for 2 hours. Distill off the solvent from the resulting reaction solution under reduced pressure to obtain a crude product. Purify the crude product by column chromatography (silica gel, petroleum ether / ethyl acetate = 4:1) to obtain 2-(trimethylsilylthio)thiazoline.

[0084] (2) Dissolve 2-(trimethylsilylthio)thiazoline (1 mol) in 150 ml of carbon tetrachloride, add N-bromosuccinimide (NBS, 1.2 mol) and azobisisobutyronitrile (AIBN, 8.2 g) under an ice bath, and heat and reflux the reaction in the dark for 6 hours. Cool the reaction solution, filter off the by-products, distill and concentrate, and then purify by column chromatography (silica gel, dichloromethane / methanol = 20:1) to obtain 4-bromo-2-(trimethylsilylthio)thiazoline.

[0085] (3) Dissolve 4-bromo-2-(trimethylsilylthio)thiazoline (1 mol) in 200 ml of ethanol, add sodium hydrosulfide (NaHS, 2.0 mol), and heat and reflux the reaction for 8 hours to replace the bromine atom at the 4-position. After the reaction solution is cooled, concentrate it under reduced pressure, and purify it by column chromatography (silica gel, dichloromethane / methanol = 10:1) to obtain 4-mercapto-2-(trimethylsilylthio)thiazoline.

[0086] (4) Dissolve 4-mercapto-2-(trimethylsilylthio)thiazoline (1 mol) in 300 ml of methanol, add 2 L of dilute hydrochloric acid (1 M), and stir the reaction at room temperature for 3 hours. The trimethylsilyl protecting group is hydrolyzed to restore the mercapto group at the 2-position. The reaction solution is adjusted to neutral with saturated sodium bicarbonate solution, the solvent is removed by distillation under reduced pressure, and finally the target product 2,4-dimercaptothiazoline is obtained by recrystallization (ethanol / water mixed solvent 1:1).

[0087] Example 1

[0088] Inside a glove box filled with argon, accurately weigh 64.2 g of polyethylene oxide (PEO, Wuhan Jixin Yibang Biotechnology Co., Ltd., CAS No.: 25322-68-3, molecular weight 35,000) and 35.5 g of lithium bis(trifluoromethanesulfonyl)imide, and add them to 500 mL of acetonitrile organic solvent. Set the temperature to 55 °C and continuously stir at a speed of 200 r / min for 5 hours until the PEO is completely dissolved to form a homogeneous solution. Subsequently, add 0.3 g of 4-methoxy-5-methylcarboxylate-2-mercaptothiazoline (accounting for 0.3% of the total mass of the electrolyte) and 1.5 g of lithium bis(fluorosulfonyl)imide (film-forming additive, accounting for 1.5% of the total mass of the electrolyte) to the above basic solution, and continue stirring for 3 hours to ensure that all components are fully mixed evenly. Pour the obtained solution onto a clean flat mold of 10 cm × 10 cm, and use a 0.2 mm thick scraper to precisely control the thickness of the film by the doctor blade method. After coating, place the mold in a vacuum drying oven and dry it at 45 °C for 18 hours to fully volatilize the organic solvent, and finally obtain a solid electrolyte membrane with a thickness of 0.05 mm.

[0089] Inside a glove box filled with argon, using a lithium metal sheet as the negative electrode and LiFePO4 as the positive electrode, use the above-prepared solid electrolyte membrane as the separator to assemble a solid-state lithium-ion battery.

[0090] Example 2

[0091] In a glove box filled with argon, accurately weigh 64.2 g of polyethylene oxide (PEO, Wuhan Jixin Yibang Biotechnology Co., Ltd., CAS No.: 25322 - 68 - 3, molecular weight 35,000) and 35.5 g of lithium bis(trifluoromethanesulfonyl)imide, and add them to 500 mL of acetonitrile organic solvent. Set the temperature to 55 °C and continuously stir at a speed of 200 r / min for 5 hours until the PEO is completely dissolved to form a homogeneous solution. Subsequently, add 0.3 g of 4 - acetyl - 5 - formamido - 2 - mercapto - thiazoline (accounting for 0.3% of the total mass of the electrolyte) and 1.5 g of lithium bis(fluorosulfonyl)imide (film - forming additive, accounting for 1.5% of the total mass of the electrolyte) to the above - mentioned basic solution, and continue stirring for 3 hours to ensure that all components are fully mixed evenly. Pour the obtained solution onto a clean flat mold of 10 cm × 10 cm, and use a 0.2 - mm - thick scraper to precisely control the thickness of the film by the doctor - blade method. After coating, place the mold in a vacuum drying oven and dry it at 45 °C for 18 hours to allow the organic solvent to fully volatilize, and finally obtain a solid electrolyte membrane with a thickness of 0.05 mm.

[0092] In a glove box filled with argon, using a lithium metal sheet as the negative electrode and LiFePO4 as the positive electrode, use the above - prepared solid electrolyte membrane as the separator to assemble a solid - state lithium - ion battery.

[0093] Example 3

[0094] Prepare the solid - state lithium - ion battery electrolyte and the solid - state lithium - ion battery according to the preparation method described in Example 1, with the only difference being that the 2 - mercapto - thiazoline - type compound is 3 - sulfonic acid - 2,5 - dimercapto - 4 - (pyridin - 3 - yl) - thiazoline.

[0095] Example 4

[0096] Prepare the solid - state lithium - ion battery electrolyte and the solid - state lithium - ion battery according to the preparation method described in Example 1, with the only difference being that the 2 - mercapto - thiazoline - type compound is 4 - phenyl - 5 - oxo - 2 - mercapto - thiazoline.

[0097] Example 5

[0098] Prepare the solid - state lithium - ion battery electrolyte and the solid - state lithium - ion battery according to the preparation method described in Example 1, with the only difference being that the 2 - mercapto - thiazoline - type compound is 2,4 - dimercapto - thiazoline.

[0099] Example 6

[0100] Prepare the solid - state lithium - ion battery electrolyte and the solid - state lithium - ion battery according to the preparation method described in Example 1, with the only difference being that the 2 - mercapto - thiazoline - type compound is 5 - oxo - 2 - mercapto - thiazoline.

[0101] Example 7

[0102] Prepare a solid-state lithium-ion battery electrolyte and a solid-state lithium-ion battery according to the preparation method described in Example 1, except that the 2-mercapto thiazoline compound is 2-mercapto thiazoline.

[0103] Example 8

[0104] Prepare a solid-state lithium-ion battery electrolyte and a solid-state lithium-ion battery according to the preparation method described in Example 2, except that the 2-mercapto thiazoline compound is 0.1 g of 4-acetyl-5-formamido-2-mercapto thiazoline.

[0105] Example 9

[0106] Prepare a solid-state lithium-ion battery electrolyte and a solid-state lithium-ion battery according to the preparation method described in Example 1, except that the 2-mercapto thiazoline compound is 0.2 g of 4-acetyl-5-formamido-2-mercapto thiazoline.

[0107] Example 10

[0108] Prepare a solid-state lithium-ion battery electrolyte and a solid-state lithium-ion battery according to the preparation method described in Example 1, except that the 2-mercapto thiazoline compound is 0.4 g of 4-acetyl-5-formamido-2-mercapto thiazoline.

[0109] Example 11

[0110] Prepare a solid-state lithium-ion battery electrolyte and a solid-state lithium-ion battery according to the preparation method described in Example 1, except that the 2-mercapto thiazoline compound is 0.5 g of 4-acetyl-5-formamido-2-mercapto thiazoline.

[0111] Comparative Example 1

[0112] Prepare a solid-state lithium-ion battery electrolyte and a solid-state lithium-ion battery according to the preparation method described in Example 2, except that the lithium salt is 1 M lithium bis(fluorosulfonyl)imide (LiFSI).

[0113] Comparative Example 2

[0114] Without 2-mercapto thiazoline compound additive, the basic electrolyte lithium salt is 1 M lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), and the rest refers to Example 2.

[0115] Comparative Example 3

[0116] Without 2-mercapto thiazoline compound additive, the basic electrolyte lithium salt is 1 M lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), and the rest refers to Example 2.

[0117] Test Example

[0118] Cycling performance test: The solid-state lithium-ion batteries prepared in Examples 1 to 11 and Comparative Examples 1 to 3 were charged and discharged at a constant current of 2C at room temperature, the charge-discharge interval was 3.0 to 4.2V, the cut-off current was 0.02C, and the cycling performance of the lithium-ion battery was evaluated after 200 cycles. The cycling performance was calculated by the capacity retention rate of the following formula:

[0119] Capacity retention rate (%) = (discharge capacity of the 200th cycle / initial discharge capacity) × 100%;

[0120] High-temperature cycling performance test:

[0121] The solid-state lithium-ion batteries prepared in Examples 1 to 11 and Comparative Examples 1 to 3 were stored at a high temperature of 60°C, then charged to 4.2V at a constant current and constant voltage of 2C, the cut-off current was 0.02C, and then discharged to 3.0V at a constant current of 0.5C. After repeating the 0.5C charge / 0.5C discharge cycle 100 times, the cycling performance of the lithium-ion battery was evaluated. The cycling performance was calculated by the capacity retention rate of the following formula.

[0122] Capacity retention rate (%) = (discharge capacity of the 100th cycle / initial discharge capacity) × 100%.

[0123] Rate performance test:

[0124] The solid-state lithium-ion batteries prepared in Examples 1 to 11 and Comparative Examples 1 to 3 were under room temperature conditions, and then charged and discharged in a constant current and constant voltage of 0.2C, 0.5C, 1C, 2C, and 5C in sequence for 5 cycles. The charge-discharge interval was 3.0 to 4.2V, the cut-off current was 0.02C, and then finally charged and discharged in a constant current and constant voltage of 0.5C in this interval for 50 cycles to measure the high-rate cycling performance of the lithium-ion battery. The high-rate cycling performance was calculated by the capacity retention rate of the following formula.

[0125] Capacity retention rate (%) = (discharge capacity of the 75th cycle / discharge capacity of the 10th cycle) × 100%. The test results of the cycling performance, high-temperature cycling performance, and rate cycling performance are shown in Table 1.

[0126] Table 1 Test results of the cycling performance, high-temperature cycling performance, and rate cycling performance of the solid-state lithium-ion batteries prepared in Examples 1 to 11 and Comparative Examples 1 to 3

[0127] Cycling performance (%) High-temperature cycling performance (%) Rate performance (%) Example 1 96.5 94.2 96.4 Example 2 99.2 98.9 98.8 Example 3 95.6 94.8 96.6 Example 4 94.5 95.1 96.8 Example 5 98.2 94.9 96.7 Example 6 92.4 91.6 95.3 Example 7 91.6 90.9 96.5 Example 8 91.3 89.8 89.6 Example 9 97.6 96.6 95.3 Example 10 92.6 91.2 93.2 Example 11 90.5 90.1 92.2 Comparative Example 1 90.5 88.8 87.9 Comparative Example 2 79.3 35.5 81.6 Comparative Example 3 74.2 79.3 80.2

[0128] As can be seen from the results in Table 1, 2-mercapto thiazoline compounds are effective electrolyte functional additives for solid-state lithium batteries. 2-mercapto thiazoline compounds can improve the high-temperature cycling performance and rate performance at high current density of lithium-ion batteries by constructing flexible ion transport channels, forming composite networks and SEI films. 4-acetyl-5-formamido-2-mercapto thiazoline can make lithium batteries exhibit more stable cycling performance than 4-methoxy-5-methoxycarbonyl-2-mercapto thiazoline. The acetyl group and amide group it contains have a stronger coordination ability with Li + than the ester group and methoxy group. The nitrogen atom in the amide group has a lone pair of electrons and can form a stable weak coordination bond with Li + to construct a more stable flexible ion transport channel, thereby improving the high-temperature cycling performance of the battery. The film structure formed by 4-acetyl-5-formamido-2-mercapto thiazoline is more stable and more protective. During charge and discharge cycles, it can better inhibit the side reactions of electrolyte salts, protect electrode materials, reduce internal battery losses, enable the battery to maintain a higher discharge capacity at high current density, have higher rate performance, and more stable cycling performance. 2-mercapto thiazoline compounds with phenyl, pyridyl, sulfonic acid group or mercapto group, due to their specific functional groups, such as the nitrogen atom in the pyridyl group having a lone pair of electrons, can have a weak coordination interaction with lithium ions in the lithium salt to stabilize the lithium ions and make ion conduction more orderly. The phenyl group has certain electron delocalization and rigid structure, which helps to construct a stable molecular framework, has a better stabilizing effect on the lithium salt, and also exhibits more stable cycling performance for solid-state lithium batteries. Research shows that 2-mercapto thiazoline compounds are electrolyte functional additives with great development prospects for solid-state lithium batteries. The discovery of thiazole additives has expanded people's understanding of solid electrolytes and provided inspiration for designing efficient electrolyte systems for advanced solid-state lithium batteries.

[0129] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, not all of them. People can also obtain other embodiments based on these embodiments without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. Application of a 2-mercapto thiazoline compound in a solid-state lithium-ion battery electrolyte, characterized in that, The structures of 2-mercapto thiazoline compounds are as follows: Among them, R1 is an amide group, a methyl ester group, a pyridyl group or an H atom; R2 is an acetyl group, a methoxy group, a sulfonic acid group, a mercapto group or an H atom; R3 is a phenyl group or an H atom.

2. The application according to claim 1, characterized in that The 2-mercapto thiazoline compounds are at least one of 4-acetyl-5-formamido-2-mercapto thiazoline, 4-methoxy-5-methyl ester-2-mercapto thiazoline, 4-phenyl-5-oxo-2-mercapto thiazoline, 3-sulfonic acid group-2,5-dimercapto-4-(pyridin-3-yl) thiazoline, 2-mercapto thiazoline, 5-oxo-2-mercapto thiazoline or 2,4-dimercapto thiazoline.

3. The application according to claim 2, wherein The 2-mercapto thiazoline compounds are at least one of 4-acetyl-5-formamido-2-mercapto thiazoline, 2,4-dimercapto thiazoline, 4-methoxy-5-methyl ester-2-mercapto thiazoline or 3-sulfonic acid group-2,5-dimercapto-4-(pyridin-3-yl) thiazoline.

4. The application according to claim 3, wherein The 2-mercapto thiazoline compounds are at least one of 4-acetyl-5-formamido-2-mercapto thiazoline or 2,4-dimercapto thiazoline.

5. A solid-state lithium-ion battery electrolyte, characterized in that, It includes 44-50% of lithium salt, 47-53% of polymer matrix, 0.1-0.5% of the 2-mercapto thiazoline compounds described in any one of claims 1-4, and 2-3% of film-forming additive. The foregoing percentages are mass percentages.

6. The solid-state lithium-ion battery electrolyte according to claim 5, characterized in that, The lithium salt includes at least one of lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium difluorophosphate, lithium bis(oxalato)difluorophosphate, lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium methanesulfonate, lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide or lithium bis(trifluoromethylsulfonyl)imide.

7. The solid-state lithium-ion battery electrolyte according to claim 5 or 6, characterized in that The polymer matrix includes at least one of polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, polypropylene oxide, polyvinylidene chloride and single-ion polymer electrolyte.

8. The solid-state lithium-ion battery electrolyte according to claim 5 or 6, characterized in that The film-forming additive includes at least one of lithium bis(fluorosulfonyl)imide, lithium difluoroborate, vinylene carbonate, 1,3-propane sultone, 1,4-butane sultone, acrylic lactone, ethylene sulfite, fluoroethylene carbonate or N-acetylcaprolactam.

9. The solid-state lithium-ion battery electrolyte according to claim 5 or 6, characterized in that The lithium salt is lithium bis(trifluoromethylsulfonyl)imide, the polymer matrix is polyethylene oxide, and the film-forming additive is lithium bis(fluorosulfonyl)imide.

10. A method for preparing the solid-state lithium-ion battery electrolyte according to any one of claims 5-9, characterized in that, It includes the following steps: (1) In a glove box filled with argon, add the weighed polymer matrix and lithium salt to an organic solvent, and stir at 50-60 °C until the polyethylene oxide is completely dissolved to form a homogeneous solution to obtain a basic solution. (2) Add the 2-mercapto thiazoline compounds and the film-forming additive to the basic solution obtained in step (1), and stir evenly. (3) Pour the solution obtained in (2) onto a clean flat mold, control the thickness of the film by the doctor blade method, place the coated mold in a vacuum drying oven, and dry at 40-50 °C for 12-24 hours to fully volatilize the organic solvent to form a solid electrolyte film.

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