Application of 2, 4-thiazolidinedione 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 application of a 2, 4-thiazolidinedione 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 2, 4-thiazolidinedione compound disclosed by the invention is used for preparing a solid-state lithium ion battery electrolyte, and the structure of the 2, 4-thiazolidinedione compound is as follows: # imgabs0 #, in which R1 to R7 are independently a sulfonic group, a cyano group, an ionic liquid group, a borate group, a polyether chain segment, an amino group and an ether group. The 2, 4-thiazolidinedione compound is used as a functional additive of an electrode material, the structural stability is improved through chemical bonding or physical coating, volume expansion is relieved, or an electron / ion conduction network is enhanced; a functional interface layer is formed on the surface of the electrode, so that side reaction (such as electrolyte decomposition) is inhibited, interface impedance is reduced, and the lithium metal negative electrode is stabilized (such as dendrite growth is inhibited); through an electrochemical decomposition or pre-passivation strategy, a stable solid electrolyte interface (SEI) is constructed, and the cycle life is prolonged.

Description

Technical Field

[0001] This application relates to the technical field of solid-state lithium-ion battery electrolyte manufacturing, and more specifically, to the application of 2,4-thiazolidinedione compounds in solid-state lithium-ion battery electrolytes and its preparation method. Background Art

[0002] As a disruptive energy storage solution, solid-state lithium-ion batteries have significant advantages in energy density and safety, and have broad application prospects in electric vehicles, power vehicles, etc. However, the material defects of their core component, the solid electrolyte, still restrict the industrialization process.

[0003] In the prior art, taking NASICON-type solid electrolytes (such as Li 1.5 Al 0.5 Ge 1.5 (PO4)3) as an example, its room temperature ionic conductivity can reach 2×10 -3 S / cm, but its mechanical brittleness results in the need to maintain the electrode / electrolyte interface contact pressure above 15 MPa (far exceeding the limit of existing battery packaging processes), and an insulating layer of Li3Al2(PO4)3 will form due to the segregation of aluminum elements during long-term cycling, and the interfacial impedance increases from the initial 80 Ω·cm 2 sharply to 600 Ω·cm 2 (after 200 cycles); although halide electrolytes (such as Li3YCl6) have a wide electrochemical window of 4.8 V and ionic conduction ability at the level of 10 -3 S / cm, they are extremely sensitive to humidity (hydrolyzing to form LiCl and Y(OH)3 when exposed to a 30% RH environment for 5 minutes), resulting in the need to operate the whole process in an environment with a dew point < -60 °C during large-scale production, increasing the equipment cost by more than 40%; while the thin-film LiPON electrolyte is compatible with high-voltage cathodes (>5 V), but the deposition thickness limitation (usually < 3 μm) results in its surface resistance as high as 200 Ω·cm 2 and cannot meet the low internal loss requirements of large-capacity batteries. The inherent defects of the above material systems cause the energy efficiency decay rate of the battery under high-load conditions to exceed expectations, seriously hindering its practical application process in the field of power batteries. Summary of the Invention

[0004] The purpose of the present invention is to provide an application of 2,4-thiazolidinedione compounds in solid-state lithium-ion battery electrolytes, a solid-state lithium-ion battery electrolyte and its preparation method. The present invention uses 2,4-thiazolidinedione compounds as additives for solid-state lithium-ion battery electrolytes, improves the cycling stability of solid-state lithium-ion batteries under high-load conditions, and promotes the application of solid-state lithium-ion batteries in the field of power batteries.

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

[0006] Application of a 2,4-thiazolidinedione compound in a solid-state lithium-ion battery electrolyte. The structure of the 2,4-thiazolidinedione compound is as follows:

[0007]

[0008] Wherein, R1 to R7 are independently a sulfonic acid group, a cyano group, an ionic liquid group (imidazolium or pyrrolidone), a borate group, a polyether segment, an amino group, and an ether group.

[0009] The 2,4-thiazolidinedione compound of the present invention can promote the dissociation of lithium salts, increase the free Li + concentration, and reduce the interfacial charge transfer impedance.

[0010] The above-mentioned ionic liquid group is imidazolium or pyrrolidone.

[0011] In order to improve the durability of the battery, the above 2,4-thiazolidinedione compound is at least one of 5-cyano-2,4-thiazolidinedione, 3-sulfonic acid group-2,4-thiazolidinedione, 4-imidazolium-1,2,4-thiadiazacyclohexane-3,5-dione, 4-pyrrolidone-1,2,4-thiadiazacyclohexane-3,5-dione, 5-borate group-1,2,4-thiadiazacyclohexane-3,5-dione, 4-polyether chain-1,2,4-thiadiazacyclohexane-3,5-dione, 3-aminoimidazolidine-2,4-dione or 1-ether group imidazolidine-2,4-dione. Further preferably, the 2,4-thiazolidinedione compound is at least one of 3-aminoimidazolidine-2,4-dione, 4-pyrrolidone-1,2,4-thiadiazacyclohexane-3,5-dione or 4-polyether chain-1,2,4-thiadiazacyclohexane-3,5-dione. More preferably, the 2,4-thiazolidinedione compound is 3-aminoimidazolidine-2,4-dione.

[0012] A solid-state lithium-ion battery electrolyte, the raw material components of which include 30-50% of a lithium salt, 50-70% of a polymer matrix, 0.1-1% of the 2,4-thiazolidinedione compound according to any one of claims 1-3, and 1-5% of a plasticizer. The sum of the masses of the foregoing components is 100%, and the foregoing percentages are all mass percentages.

[0013] The above lithium salt includes at least one of lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium bis(difluoromethanesulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium difluoro(oxalato)borate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, or lithium tetrafluoroborate.

[0014] The above polymer matrix includes at least one of polyethylene oxide (PEO) and its derivatives, polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), polycarbonate polymers or polystyrene polymers.

[0015] The above plasticizer includes at least one of succinonitrile, 1-butyl-2,3-dimethylimidazolium bromide (BMI-Br), and vinyl fluorocarbonate.

[0016] To improve the cycling performance of the battery, the lithium salt is preferably lithium bis(trifluoromethanesulfonyl)imide, the polymer matrix is preferably polyethylene oxide, and the plasticizer is preferably succinonitrile.

[0017] A method for preparing a solid-state lithium-ion battery electrolyte includes the following steps:

[0018] (1) In a glove box filled with argon, the weighed polymer matrix and lithium salt are mixed, tetrahydrofuran solvent is added, and the mixture is continuously stirred for 8-12 hours under an argon protection environment at 50-60 °C. Subsequently, ultrasonic treatment is carried out for 20-30 minutes to eliminate bubbles, and finally a uniform and transparent basic polymer solution is obtained.

[0019] (2) The 2,4-thiazolidinedione compound and the plasticizer are added to the basic polymer solution obtained in step (1), stirred evenly, coated, and then hot-pressed at 60-80 °C for 12-24 hours to fully volatilize the organic solvent and form a solid electrolyte membrane.

[0020] Unless otherwise specified, all percentages in the present invention are mass percentages. Technologies not mentioned in the present invention refer to the prior art.

[0021] In the present invention, the 2,4-thiazolidinedione compound is used as a functional additive for the electrode material, which improves the structural stability, alleviates volume expansion, or enhances the electron / ion conduction network through chemical bonding or physical coating; and forms a functional interface layer on the electrode surface to inhibit side reactions (such as electrolyte decomposition), reduce the interfacial impedance, and stabilize the lithium metal anode (such as inhibiting dendrite growth); through electrochemical decomposition or pre-passivation strategies, it participates in the construction of a stable solid electrolyte interface (SEI) to improve the cycle life. Description of the Drawings

[0022] Figure 1 It is a physical photo of the solid electrolyte membrane prepared in Example 1 of the present invention.

[0023] Figure 2 It is a high-temperature cycling performance graph of the solid-state lithium-ion battery prepared in Example 3 of the present invention. Detailed Description of the Invention

[0024] 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.

[0025] The present invention provides an application of a 2,4-thiazolidinedione compound in a solid-state lithium-ion battery electrolyte. The 2,4-thiazolidinedione compound has the following structure:

[0026]

[0027] Wherein, R1 to R7 are independently a sulfonic acid group, a cyano group, an ionic liquid group (imidazolium or pyrrolidone), a borate group, a polyether segment, an amino group, and an ether group.

[0028] In the present invention, unless otherwise specified, all 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.

[0029] In the present invention, the heterocycle is preferably thiazolidine containing a sulfur-oxygen heterocyclic structure.

[0030] In the present invention, when R1 to R7 are respectively preferably a sulfonic acid group, a cyano group, an ionic liquid group (imidazolium or pyrrolidone), a borate group, a polyether segment, an amino group, and an ether group, the 2,4-thiazolidinedione compound is preferably

[0031] 1-ether group-3-aminoimidazolidine-2,4-dione,

[0032]

[0033] 2-sulfonic acid group-5-cyano-2,4-thiazolidinedione,

[0034] 1-polyether chain-2-boronic acid group-4-pyrrolidone-1,2,4-thiadiazacyclohexane-3,5-dione,

[0035] 1-polyether chain-2-boronic acid group-4-imidazolium-1,2,4-thiadiazacyclohexane-3,5-dione.

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

[0037]

[0038] Among them, R1 to R7 are respectively a sulfonic acid group, a cyano group, an ionic liquid group (imidazolium or pyrrolidone), a borate group, a polyether segment, an amino group, and an ether group.

[0039] In the present invention, the lithium salt preferably includes one or more of lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium bis(difluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluoro(oxalato)borate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium tetrafluoroborate.

[0040] In the present invention, the polymer matrix includes one or more of polyethylene oxide (PEO) and its derivatives, polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), polycarbonate polymers, and polystyrene polymers.

[0041] In the present invention, the mass ratio of the lithium salt, the 2,4-thiazolidinedione compound, and the polymer matrix is preferably 30-50%: 0.1-1%: 50-70%, and more preferably 42.5%: 0.2%: 57.3%.

[0042] In the present invention, the solid-state lithium-ion battery electrolyte further includes a plasticizer; the plasticizer preferably includes one or more of succinonitrile, 1-butyl-2,3-dimethylimidazolium bromide (BMI-Br), and fluoroethylene carbonate.

[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) Weigh the polyethylene oxide (PEO) and lithium bis(trifluoromethanesulfonyl)imide LiTFSI and mix them into a tetrahydrofuran solvent. Continuously stir for 8-12 hours under an argon protection environment at 50-60 °C, and then perform ultrasonic treatment for 30 minutes to eliminate bubbles, finally obtaining a uniform and transparent basic polymer solution.

[0045] (2) Add 0.1-1% of the 2,4-thiazolidinedione compound and the plasticizer succinonitrile, which are based on the total mass of the electrolyte, to the basic solution obtained in step (1), and stir evenly.

[0046] (3) Use a doctor blade to coat the wet film in the solution obtained in (2), and then perform hot pressing at a high temperature of 60-80 °C for 12-24 hours to fully volatilize the organic solvent, forming a solid electrolyte membrane.

[0047] To further illustrate the present invention, the following combines examples to describe in detail the application of the 2,4-thiazolidinedione compound provided by the present invention in the solid-state lithium-ion battery electrolyte, but they cannot be understood as limiting the protection scope of the present invention.

[0048] In each example, if the temperature is not particularly specified, the operation is performed at room temperature; if the stirring speed is not particularly specified, the operation is performed at 200 r / min.

[0049] Example 1

[0050] 10 g of methyl cyanoacetate, 10β-aminothiophene and 28 g of sodium carbonate were dissolved in 100 mL of 80 wt% ethanol aqueous solution at 80°C, and refluxed for 5 hours while controlling the pH to be maintained at 8-9. After the reaction was completed, the solvent was distilled off and the residue was purified by column chromatography (silica gel, CHCl3 / MeOH=10:1) to obtain 11.7 g of high-purity 2,4-thiazolidinedione (TAD).

[0051] The obtained 11.7g TAD, 20g hydrazine sulfate and 2.8g sodium carbonate were placed in a mixed solution of 100mL water and methanol in a ratio of 1:1 at 80°C, pH was adjusted to pH≈5 (adjusted with 3% dilute HCl), amination was promoted, and reflux reaction was performed for 5 hours. The mixture was concentrated under reduced pressure at a pressure of 8kPa and a temperature of 15°C, and the residue was purified by column chromatography (silica gel, MeOH / CHCl3=5:1), and then the product was placed in a solution of 100mL ethanol / water in a ratio of 1:1 for recrystallization and further purified to obtain 11.5g purified 2-amino-4-thiazolidinedione.

[0052] 11.5 g of 2-amino-4-thiazolidinedione, 19 g of toluenesulfonyl chloride and 10.1 g of triethylamine were dissolved in 100 mL of dimethylformamide (DMF) and reacted at 5°C for 5 h. The product was washed with H2O and 5% NaHCO3 aqueous solution in turn to remove by-products HCl and TEA, then dried over anhydrous Na2SO4, concentrated and purified by column chromatography (silica gel, EtOAc / MeOH gradient elution) to obtain 19.8 g of the target product 3-sulfonic acid-2,4-thiazolidinedione.

[0053] In a glove box filled with argon, 61.5 g of polyethylene oxide (PEO, molecular weight 600,000 g / mol, purity ≥99%, Aladdin), 35 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 500 ml of tetrahydrofuran were accurately weighed, stirred at 55 ° C under argon protection for 10 hours, and then ultrasonicated for 30 minutes to remove bubbles to form a uniform polymer solution; then 0.5 g of 3-sulfonic acid-2,4-thiazolidinedione and 3.5 g of succinonitrile were added and stirred to mix, and then coated into a wet film by a scraper, and the solvent was volatilized by hot pressing at 70 ° C for 12 hours to finally obtain a solid electrolyte membrane with a thickness of 80 μm.

[0054] 8 mL of 5% PVDF (polyvinylidene fluoride, Dongguan Kajin, PVDF 6020), 2 g of lithium iron phosphate, and 0.25 g of graphite (Dongguan Kajin, KNG-150, CAS: 7782-42-5) were mixed and stirred at 60 °C to obtain the positive electrode slurry; 5 mL of 80 wt% silicon-carbon (Shanghai Putailai New Energy Technology Co., Ltd., CAS No.: 409-21-2, PTL-SC-2000), 0.2 g of sodium sulfide, 0.25 g of graphite (Dongguan Kajin, KNG-150, CAS: 7782-42-5), and 5 mL of 10 wt% PTFE (polytetrafluoroethylene binder, Zhonghao Chenguang Research Institute of Chemical Industry Co., Ltd., CAS: 9002-84-0, CG-1) were mixed and the humidity was controlled to obtain the negative electrode slurry; subsequently, the positive and negative electrode slurries were coated and dried in a vacuum oven at 60 °C for 48 h to obtain a LiFePO4 positive electrode with a thickness of 100 μm and a graphite negative electrode material with a thickness of 360 μm.

[0055] A solid-state lithium-ion battery was prepared in an Ar-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm). The graphite negative electrode material with a thickness of 360 μm was used as the negative electrode, the LiFePO4 positive electrode with a thickness of 100 μm was used as the positive electrode, and the prepared solid-state electrolyte membrane was used as the separator to assemble a solid-state lithium-ion battery.

[0056] Example 2

[0057] 15 g of TAD (prepared with reference to Example 1) and 6.5 g of sodium cyanide were dissolved in 50 mL of DMF (N,N-dimethylformamide) and stirred at 50 °C for 6 h under nitrogen protection. 50 mL of 5 wt% hydrochloric acid was added for acidification. The acidified mixture was transferred to a separatory funnel, and then an equal volume of ethyl acetate was added for extraction. It was vigorously shaken for 2 minutes (releasing pressure 3 times), allowed to stand for 10 minutes to separate layers, the lower aqueous phase (containing DMF, NaCl, and excess HCl) was separated, and the upper organic phase was retained. The extraction was repeated twice, and the organic phases were combined and washed with deionized water to obtain the crude product. 10 g of the crude product was added to 100 mL of acetonitrile, stirred and dissolved at 70 °C, and hot filtered to obtain 95 mL of filtrate. 30 mL of acetonitrile was added dropwise, and the temperature was lowered to 0 °C and allowed to stand for 14 h. After suction filtration and drying, 15 g of 5-cyano-2,4-thiazolidinedione was obtained.

[0058] The preparation method of the solid-state electrolyte membrane referred to Example 1, except that 3-sulfonic acid-2,4-thiazolidinedione was replaced by 5-cyano-2,4-thiazolidinedione, and the rest were all referred to Example 1.

[0059] The preparation methods of the positive and negative electrode materials referred to Example 1.

[0060] The preparation method of the solid-state lithium-ion battery referred to Example 1

[0061] Example 3

[0062] 7.6 g of thiourea and 10 g of acetylacetone were refluxed in 100 mL of hydrochloric acid with a concentration of 0.01 mol / L for 6 hours. The product was filtered, washed and dried to obtain 6 g of thiodiazacyclohexane. 6 g of thiodiazacyclohexane was oxidized at 60 °C for 5 hours under the condition of 100 mL of benzoyl peroxide to generate 11.5 g of 4-hydroxythiodiazacyclohexane. 11.5 g of 4-hydroxythiodiazacyclohexane and 23.3 g of ionic liquid N-butylpyridinium tetrafluoroborate were added to 100 mL of DMF and stirred at 60 °C for 12 hours to obtain 11.5 g of 4-ionic liquid-based thiodiazacyclohexane. 11.5 g of 4-ionic liquid-based thiodiazacyclohexane and 30 g of DDQ (2,3-dichloro-5,6-dicyanobenzoquinone) were reacted in 100 mL of dichloromethane at -5 °C for 4 hours. The product was acidified with 30 ml of 2 mol / L hydrochloric acid, and 10 ml of 5% NaOH by mass concentration was added dropwise to the product until the pH reached 8, and the temperature was controlled in an ice bath; then 30 ml of a 1:1 mixture of acetone and water was added for extraction. After shaking, the mixture was allowed to stand and layer. The upper organic phase was collected, and the extraction was repeated twice. The organic phases were combined and washed with deionized water, dried, and the solvent was removed by distillation under reduced pressure to obtain a crude product. Then, 10 g of the crude product was added to 100 mL of acetonitrile, stirred and dissolved at 70 °C, hot filtered to obtain 95 mL of filtrate, 250 mL of n-hexane was added dropwise, and the temperature was lowered to 0 °C and allowed to stand for 14 hours. After suction filtration and drying, 4-ionic liquid-based-1,2,4-thiadiazacyclohexane-3,5-dione was obtained.

[0063] The preparation method of the solid electrolyte membrane refers to Example 1, except that 3-sulfonic acid-2,4-thiazolidinedione is replaced by 4-ionic liquid-based-1,2,4-thiadiazacyclohexane-3,5-dione, and the rest are all referred to Example 1.

[0064] The preparation methods of the positive and negative electrode materials refer to Example 1.

[0065] The preparation method of the solid-state lithium ion electrolyte refers to Example 1.

[0066] Example 4

[0067] Take 10 g of thiodiazacyclohexane (prepared with reference to Example 3), react it with 13.6 g of DDQ in 100 ml of dichloromethane at -5 °C for 4 hours. The obtained product is successively acidified with 150 ml of dilute hydrochloric acid (dilute hydrochloric acid with a mass concentration of 5%), and extracted with an equal volume of ethyl acetate. After shaking, it is left to stand for liquid separation, and the extraction is repeated twice. The organic phases are combined and washed with deionized water, dried, and the solvent is removed by distillation under reduced pressure. Then it is purified by recrystallization to obtain 4.3 g of 3,5-diketo-thiodiazacyclohexane. Dissolve 4.3 g of 3,5-diketo-thiodiazacyclohexane in 50 mL of anhydrous toluene, place it in a dry three-necked flask, add 0.65 g of benzoyl peroxide (BPO) as a catalyst, stir until completely dispersed, introduce nitrogen for protection to exclude the interference of oxygen and moisture, heat the reaction system to 60 °C, and keep stirring at a constant temperature for 8 hours (monitor the reaction progress by TLC, the developing agent is ethyl acetate / petroleum ether = 1:2). The raw material spot (3,5-diketo compound) disappears and a new product spot (5-hydroxy compound) appears. After the reaction is completed, cool the system to room temperature. Add 20 mL of saturated sodium thiosulfate solution and stir for 10 minutes to decompose the residual peroxide. Transfer it to a separatory funnel and extract three times with 30 mL of ethyl acetate. Combine the organic phases. The organic phases are successively washed with 10% NaHCO3 solution (20 mL × 2) and deionized water (20 mL × 2). Add anhydrous sodium sulfate and dry for 30 minutes, then filter to remove the desiccant. Distill off the solvent under reduced pressure to obtain the crude product. Recrystallize with 20 ml of ethanol-water mixed solvent (volume ratio 1:3) to obtain 4.3 g of white crystalline 5-hydroxy-thiodiazacyclohexane. Place 4.3 g of 5-hydroxy-thiodiazacyclohexane in 50 ml of DMF (N,N-dimethylformamide), then successively add 2.20 boric acid, 6.73 g of DCC (dicyclohexylcarbodiimide) and 0.36 g of catalyst DMAP (4-dimethylaminopyridine) to carry out the esterification reaction. Add 20 g of triethylamine to neutralize the by-product (HCl), stir at 60 °C for 12 hours, dropwise add 150 ml of n-hexane, cool to 0 °C, and let it stand for 14 hours. After suction filtration and drying, dissolve 4.3 g of the crude product in 85 mL of hot dichloromethane (50 °C) in a fume hood, add 0.1 g of activated carbon for decolorization and filter while it is hot. Slowly add 255 mL of n-hexane dropwise with stirring until slightly turbid, cool in an ice bath to 0 °C and let it stand for 12 hours to crystallize. After suction filtration, wash twice with 20 mL of pre-cooled n-hexane, and dry the filter cake at 45 °C and 10 mmHg under vacuum for 12 hours. Finally, the target product 5-borate-1,2,4-thiadiazacyclohexane-3,5-dione is obtained.

[0068] The preparation method of the solid electrolyte membrane refers to Example 1, except that 3-sulfonic acid-2,4-thiazolidinedione is replaced by 5-borate-1,2,4-thiadiazacyclohexane-3,5-dione, and the rest are all referred to Example 1.

[0069] The preparation methods of the positive and negative electrode materials refer to Example 1.

[0070] The preparation method of the solid-state lithium-ion battery refers to Example 1

[0071] Example 5

[0072] Take 22 g of 3,5-diketo thiodiazacyclohexane (prepared with reference to Example 4) and 10 g of di-tert-butyl peroxide and place them in 100 mL of tetrahydrofuran. Under the conditions of a reaction temperature of 60 °C and a reaction time of 24 hours, use 30 ml of p-toluenesulfonic acid with a concentration of 1 mol / L to catalyze the formation of 11.03 g of 4-hydroxythiodiazacyclohexane. Then add 17.2 g of toluenesulfonic acid and react at 70 °C for 12 hours to form 4-polyether chain-1,2,4-thiadiazacyclohexane-3,5-dione.

[0073] The preparation method of the solid electrolyte membrane refers to Example 1, except that 3-sulfonic acid-2,4-thiazolidinedione is replaced by 4-polyether chain-1,2,4-thiadiazacyclohexane-3,5-dione, and the rest are all referred to Example 1.

[0074] The preparation methods of the positive and negative electrode materials refer to Example 1.

[0075] The preparation method of the solid-state lithium-ion battery refers to Example 1

[0076] Example 6

[0077] Place 10 g of acetylacetone, 8.9 g of glycine methyl ester, and 0.1 g of p-toluenesulfonic acid (PTSA) in 100 mL of THF (tetrahydrofuran) and reflux and heat for 5 hours. Filter, wash, and dry to form 6.8 g of an imidazolidine intermediate. React the dried 6.8 g of the imidazolidine ring intermediate with 100 mL of benzyl alcohol at 60 °C for 8 h to protect the amino group, then add 50 g of 2,3-dichloro-5,6-dicyano-p-benzoquinone and 100 mL of dichloromethane, and react in a -5 °C environment for 4 hours. The product is acidified (100 mL of 40 wt% hydrofluoric acid) to obtain a crude product. Then add 10 g of the crude product to 100 mL of acetonitrile, stir and dissolve at 70 °C, and perform hot filtration to obtain 95 mL of filtrate. Dropwise add 75 mL of deionized water, cool down to 0 °C, and let stand for 14 hours. Filter by suction and dry to finally obtain the product 3-aminoimidazolidine-2,4-dione.

[0078] The preparation method of the solid electrolyte membrane refers to Example 1, except that 3-sulfonic acid-2,4-thiazolidinedione is replaced by 3-aminoimidazolidine-2,4-dione, and the rest are all referred to Example 1.

[0079] The preparation methods of the positive and negative electrode materials refer to Example 1.

[0080] Preparation Method of Solid-State Lithium-Ion Battery - Reference Example 1

[0081] Example 7

[0082] 6.8 g of imidazolidine ring (prepared with reference to Example 6) was mixed with 50 g of 2,3-dichloro-5,6-dicyano-p-benzoquinone and 100 mL of dichloromethane, and reacted at -5 °C for 4 hours to obtain 9.4 g of 2,4-diketoimidazolidine. Then, 1.5 g of methanol and 12 g of sodium bisulfate were added and reacted at 70 °C for 12 hours. Finally, after washing with 0.1 mol / L sodium carbonate solution, 1-ethoxyimidazolidine-2,4-dione was obtained.

[0083] The preparation method of the solid electrolyte membrane refers to Example 1, except that 3-sulfonyl-2,4-thiazolidinedione is replaced by 1-ethoxyimidazolidine-2,4-dione, and the rest are all referred to Example 1.

[0084] The preparation methods of the positive and negative electrode materials refer to Example 1.

[0085] Preparation Method of Solid-State Lithium-Ion Battery - Reference Example 1

[0086] Comparative Example 1

[0087] The difference from Example 1 is that the lithium salt used in the solid-state lithium-ion battery electrolyte membrane is lithium bis(oxalato)borate, and the rest are all referred to Example 1.

[0088] Comparative Example 2

[0089] The difference from Example 1 is that there is no 2,4-thiazolidinedione compound additive, and the lithium salt used is lithium bis(oxalato)borate, and the rest are all referred to Example 1.

[0090] Comparative Example 3

[0091] The difference from Example 1 is that there is no 2,4-thiazolidinedione compound additive, and the lithium salt used is LiTFSI, and the rest are all referred to Example 1.

[0092] Test Example

[0093] Cycling Performance Test: The 2032 coin cells prepared in Examples 1 to 7 and Comparative Examples 1 to 3 were charged and discharged at a constant current of 2C at room temperature, the charge-discharge interval was 2.4 - 3.4 V, and the cut-off current was 0.05C. After 500 cycles, the cycling performance of the lithium battery was evaluated. The cycling performance was calculated by the capacity retention rate of the following formula:

[0094] Capacity Retention Rate (%) = (Discharge Capacity of the 200th Cycle / Initial Discharge Capacity) × 100%;

[0095] High-Temperature Cycling Performance Test:

[0096] The 2032 button cells prepared in Examples 1-7 and Comparative Examples 1-3 were stored at a high temperature of 60°C, then charged to 3.4V under constant current and constant voltage at 2C, with the cut-off current being 0.05C, and then discharged to 2.4V under a constant current of 1C. After repeating the 1C charge / 1C discharge cycle 100 times, the cycle performance of the lithium battery was evaluated. The cycle performance was calculated by the capacity retention rate in the following formula.

[0097] Capacity retention rate (%) = (discharge capacity of the 100th cycle / initial discharge capacity) × 100%.

[0098] Rate performance test:

[0099] The 2032 button cells prepared in Examples 1-7 and Comparative Examples 1-3 were under normal temperature conditions, and then charged and discharged cyclically 5 times under constant current and constant voltage at 0.2C, 0.5C, 1C, 2C, and 5C in sequence. The charge-discharge interval was 2.4 - 3.4V, and the cut-off current was 0.05C. Then, finally, they were charged and discharged cyclically 50 times under constant current and constant voltage at 1C in this interval to measure the high-rate cycle performance of the lithium battery. The high-rate cycle performance was calculated by the capacity retention rate in the following formula.

[0100] Capacity retention rate (%) = (discharge capacity of the 75th cycle / discharge capacity of the 10th cycle) × 100%.

[0101] The test results of cycle performance, high-temperature cycle performance, and rate cycle performance are shown in Table 1.

[0102] Table 1 Test results of cycle performance and "high-temperature cycle performance" of the button cells of the solid-state lithium-ion batteries prepared in Examples 1-7 and 1-3

[0103] Table 1 Test results of cycle performance, high-temperature cycle performance, and rate cycle performance of the solid-state lithium-ion batteries prepared in Examples 1-3 and Comparative Examples 1-3

[0104] Cycling performance (%) High-temperature cycling performance (%) Rate performance (%) Example 1 90.2 90.1 91.3 Example 2 90.9 91.5 92.6 Example 3 95.1 96.2 96.7 Example 4 92.3 92.2 92.4 Example 5 95.1 94.4 97.7 Example 6 96.7 96.2 97.4 Example 7 91.4 90.2 91.2 Comparative example 1 90.7 89.3 90.2 Comparative example 2 78.8 70.5 80.3 Comparative example 3 75.4 78.2 76.3

[0105] As can be seen from the results in Table 2, the solid-state lithium-ion batteries of Examples 1-7 showed excellent performance in terms of cycle performance, high-temperature cycle performance, and rate performance. In particular, for Examples 3 and 5, all their performance indicators were significantly better than those of Comparative Examples 1-3. Specifically, the cycle performance of Example 3 was 93.4%, the high-temperature cycle performance was 93.7%, and the rate performance was 95.1%; the cycle performance of Example 5 was 93.2%, the high-temperature cycle performance was 93.8%, and the rate performance was 95.9%. In contrast, Comparative Examples 1 and 3 showed relatively poor performance, with cycle performances of 72.4% and 75.4% respectively, high-temperature cycle performances of 59.6% and 78.2% respectively, and rate performances of 75.2% and 76.3% respectively.

[0106] The inventor analyzed that the main reason for this performance difference lies in the more optimized reaction conditions and additives used in the examples. For example, the 4-ionic liquid-based-1,2,4-thiadiazinane-3,5-dione generated by the oxidation-boration reaction in Example 3, and the 4-polyether chain-1,2,4-thiadiazinane-3,5-dione generated by ring-opening polymerization in Example 5. These compounds have better electrochemical stability and ionic conductivity, which can effectively improve the cycle life and high-temperature performance of the battery.

[0107] However, due to the differences in the reaction mechanism or additive treatment methods in Comparative Example 1 and Comparative Example 3, the battery performance decreased. For example, in Comparative Example 1, different TAD treatment methods (sulfidation reaction and cyanidation reaction) were used, which may lead to unstable product structures or poor electrochemical performance; in Comparative Example 3, the amino group was not protected, and DDQ was directly used to break the amino group, which may lead to an increase in side reactions and affect the cycle stability and rate performance of the battery.

[0108] In summary, the optimized reaction conditions and additive selection in the examples are the key to improving the performance of solid-state lithium-ion batteries, while the differences in the reaction mechanism and treatment methods in the comparative examples lead to a decrease in performance.

Claims

1. Application of a 2,4-thiazolidinedione compound in a solid-state lithium-ion battery electrolyte, characterized in that, The structure of 2,4-thiazolidinedione compounds is as follows: Among them, R1 to R7 are independently a sulfonic acid group, a cyano group, an ionic liquid group (imidazolium or pyrrolidone), a borate group, a polyether segment, an amino group, and an ether group.

2. The application according to claim 1, wherein The ionic liquid group is imidazolium or pyrrolidone.

3. The application according to claim 1 or 2, characterized in that, The 2,4-thiazolidinedione compounds are at least one of 5-cyano-2,4-thiazolidinedione, 3-sulfonic acid group-2,4-thiazolidinedione, 4-imidazolium-1,2,4-thiadiazacyclohexane-3,5-dione, 4-pyrrolidone-1,2,4-thiadiazacyclohexane-3,5-dione, 5-borate group-1,2,4-thiadiazacyclohexane-3,5-dione, 4-polyether chain-1,2,4-thiadiazacyclohexane-3,5-dione, 3-aminoimidazolidine-2,4-dione, or 1-ether group imidazolidine-2,4-dione.

4. The application according to claim 3, characterized in that, At least one of 3-aminoimidazolidine-2,4-dione, 4-pyrrolidone-1,2,4-thiadiazacyclohexane-3,5-dione, or 4-polyether chain-1,2,4-thiadiazacyclohexane-3,5-dione.

5. The application according to claim 4, wherein The 2,4-thiazolidinedione compound is 3-aminoimidazolidine-2,4-dione.

6. A solid-state lithium-ion battery electrolyte, characterized in that, Its raw material components include 30-50% of lithium salt, 50-70% of polymer matrix, 0.1-1% of the 2,4-thiazolidinedione compound described in any one of claims 1-3, 1-5% of plasticizer, and the sum of the masses of the foregoing components is 100%. The foregoing percentages are all mass percentages.

7. The solid-state lithium-ion battery electrolyte according to claim 6, wherein The lithium salt is at least one of lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium bis(difluoromethanesulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium difluoro(oxalato)borate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, or lithium tetrafluoroborate.

8. The solid-state lithium-ion battery electrolyte according to claim 6 or 7, characterized in that, The polymer matrix is at least one of polyethylene oxide and its derivatives, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, polycarbonate polymers, or polystyrene polymers.

9. The solid-state lithium-ion battery electrolyte according to claim 6 or 7, characterized in that The plasticizer is at least one of succinonitrile, 1-butyl-2,3-dimethylimidazolium bromide, and vinyl carbonate fluoride.

10. The preparation method of the solid-state lithium-ion battery electrolyte according to any one of claims 6 to 9, characterized in that, It includes the following steps: (1) In a glove box filled with argon, mix the weighed polymer matrix and lithium salt, add tetrahydrofuran solvent, and continuously stir for 8-12 hours under an argon protection environment at 50-60 °C. Subsequently, perform ultrasonic treatment for 20-30 minutes to eliminate bubbles, and finally obtain a uniform and transparent basic polymer solution; (2) Add the 2,4-thiazolidinedione compound and the plasticizer to the basic polymer solution obtained in step (1), stir evenly, coat the film, and then perform hot pressing at 60-80 °C for 12-24 hours to fully volatilize the organic solvent and form a solid electrolyte membrane.

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