A flexible electrolyte material based on lithium sulfonimide quasi-solid polymer, its preparation method and application

Abstract

The present application discloses a flexible electrolyte material based on sulfonimide lithium quasi-solid polymer, its preparation method and application. In the present application, diisocyanate is used as the hard segment, polyether polyol is used as the soft segment, sulfonimide polymer lithium salt is used as the ion-conducting chain segment, and small molecule polyhydroxy compound is used as the crosslinking center. Under the catalysis of an anhydrous and anaerobic catalyst, a high-temperature reaction is carried out, and after vacuum high-temperature drying, a polymer membrane material is obtained. After being infiltrated with an organic electrolyte, a quasi-solid polymer flexible electrolyte material is obtained. The prepared electrolyte material has the advantages of excellent mechanical properties, good electrochemical stability and high ionic conductivity, and can be applied to fields such as lithium-ion batteries, lithium metal batteries and flexible soft-pack lithium batteries, greatly improving the safety performance of lithium batteries. The preparation method of the present application has the characteristics of easily available raw materials, controllable process and mild conditions, and can be used for industrial large-scale production, with good practicability.

Description

Technical Field

[0001] This application belongs to the technical field of new materials for lithium battery electrolytes and polymer technology; specifically, it relates to a flexible electrolyte material based on lithium sulfonimide quasi-solid polymer, its preparation method and application. Background Art

[0002] Lithium-ion batteries have been widely used due to their advantages such as high energy density, high working voltage, and no memory effect. They are essential for power supply in various applications, from small wearable electronic devices to large new energy vehicles. To achieve the goals of carbon peak and carbon neutrality, the proportion of new energy power generation such as photovoltaic and wind energy is increasing year by year, and lithium-ion batteries also play a crucial role in the field of new energy energy storage. However, the traditional liquid electrolyte system (dual-ion lithium salt, organic electrolyte, separator) used in lithium-ion batteries still has problems such as flammability and leakage of the electrolyte, growth of lithium dendrites on the negative electrode, and concentration polarization of anions in the electrolyte, posing risks during long-term charge and discharge of the battery.

[0003] In recent years, quasi-solid electrolytes and solid electrolytes have developed rapidly in the field of lithium-ion batteries due to their good mechanical properties and ability to inhibit lithium dendrite growth. The design of solid-state electrolytes can effectively avoid the leakage of organic electrolytes and reduce the overall safety risk of the battery. Sulfonimide-based solid or quasi-solid electrolytes with fixed anions can better solve safety problems. Sulfonimide-based electrolytes generally use methods such as covalently binding anion groups to the material skeleton or adding additional anion receptors to capture free anions to inhibit anion migration. Such electrolyte material design enables the ion transport during battery charge and discharge to be mainly based on lithium ions, with the lithium ion migration coefficient (LTN) close to 1, effectively avoiding concentration polarization inside the battery and inhibiting the growth of lithium dendrites. However, the reported sulfonimide-based polymer electrolytes currently are basically based on pure carbon chains or benzene-containing groups as the main chain (Cao, C.; Li, Y., et al. ACS Appl Mater Interfaces 2019, 11(39), 35683 - 35692.), or have a high content of room-temperature crystalline polymer polyethylene glycol (Zhang, M.; Yu, S., et al. Chem Commun (Camb) 2019, 55(47), 6715 - 6718.; Chen, Y.; Li, C., et al. J. Membr. Sci. 2021, 620.), which results in the electrolytes generally showing rigidity and lacking flexibility and stretchability. Nowadays, flexible electronic devices have been widely used in fields such as artificial skin and bendable display screens, posing higher requirements for wearable electronic devices for the human body. As an energy storage device, lithium batteries also face the transformation of "from rigid to flexible", expecting new batteries to still operate safely and stably in a freely deformable state. Summary of the Invention

[0004] In view of the above problems existing in the prior art, the technical problems to be solved by this application are as follows: to provide a preparation method of a flexible electrolyte material based on lithium sulfonimide quasi-solid polymer, which has the characteristics of easily available raw materials, controllable process, mild conditions, etc., can be used for large-scale industrial production, and has good practicability. Another technical problem to be solved by the present invention is to provide a quasi-solid sulfonimide-based polymer flexible electrolyte material, which has excellent mechanical properties, good electrochemical stability, and high ionic conductivity. Another technical problem to be solved by the present invention is to provide an application of a quasi-solid sulfonimide-based polymer flexible electrolyte material, which has very good application prospects in the fields of lithium-ion batteries, lithium metal batteries, and flexible soft-pack lithium batteries, etc., and greatly improves the battery safety performance.

[0005] In order to solve the above problems, the technical solutions adopted by this application are as follows:

[0006] A preparation method of a flexible electrolyte material based on lithium sulfonimide quasi-solid polymer, comprising the following steps:

[0007] 1) Under the condition of catalysis by an anhydrous and anaerobic catalyst, polyether polyol, small molecule polyhydroxy compound (low functionality, df = 3-4), lithium salt of bis-hydroxy-terminated sulfonimide polymer and diisocyanate are successively added and reacted at 60-100 °C for 0.5-20 hours to obtain a sulfonimide-based prepolymer. During the reaction process, 1-20 mL of solvent is added for dilution; the mass ratio of polyether polyol, lithium salt of bis-hydroxy-terminated sulfonimide polymer and diisocyanate is 1:1:1-5:5:1. The content of small molecule polyhydroxy compound (low functionality, df = 3-4) accounts for 0.5%-5% of the total feeding mass, and the catalyst content accounts for 0.1%-1% of the total feeding mass; the structural general formula of the sulfonimide-based prepolymer is as follows:

[0008]

[0009] In the formula, R1 is selected from:

[0010] R2 is selected from those with Mn of 2000, 2700 or 3300

[0011] R3 is selected from

[0012] R4 is selected from:

[0013] 2) React the sulfonimide-type prepolymer with a small molecule polyhydroxy compound (high functionality, df≥15) under the catalysis of a catalyst in an anhydrous and oxygen-free condition at 60-100 °C for 0.5-6 hours to obtain a preliminarily cross-linked product solution; pour the solution into a circular polytetrafluoroethylene mold, carry out a cross-linking reaction at 60-120 °C for 6-24 hours and volatilize the solvent, and obtain a polymer membrane material after vacuum drying at 60-120 °C for 6-24 hours. The content of the small molecule polyhydroxy compound (high functionality, df≥15) accounts for 1% to 20% of the total feeding mass;

[0014] 3) Immerse the dried polymer membrane material obtained in 2) in an organic electrolyte solution and fully swell it to an equilibrium state to prepare a sulfonimide-type quasi-solid polymer flexible electrolyte material.

[0015] The diisocyanate selected from one or a mixture of 4,4′-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate.

[0016] The polyether polyol selected from poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) triblock polyether (PPG-PEG-PPG, ), and the number average molecular weight (Mn) is one or a mixture of 2000, 2700, 3300.

[0017] The small molecule polyhydroxy compound (low functionality, df = 3-4) selected from one or a mixture of glycerol, trimethylolpropane, pentaerythritol.

[0018] The sulfonimide polymer lithium salt selected from one or a mixture of three bis-hydroxy-terminated R4 polymers (named lithium p-trifluoromethylbenzenesulfonimide polymer salt, lithium p-benzenesulfonimide polymer salt, lithium trifluoromethanesulfonimide polymer salt respectively according to different structures, and the degree of polymerization n = 18).

[0019] The catalyst selected from one or a mixture of stannous octoate, dibutyltin dilaurate.

[0020] The small molecule polyhydroxy compound (high functionality, df≥15) selected from one or a mixture of α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin, hydroxyethyl-β-cyclodextrin, hydroxypropyl-β-cyclodextrin.

[0021] The reaction solvent selected from one or a mixture of dimethyl sulfoxide, N,N-dimethylformamide, N-methylpyrrolidone.

[0022] The organic electrolyte selected from one or a mixture of dimethyl carbonate, diethyl carbonate, ethylene carbonate, fluoroethylene carbonate, propylene carbonate, γ-butyrolactone, γ-valerolactone.

[0023] In step 3), the obtained sulfonimide-based quasi-solid polymer flexible electrolyte material is stored under anhydrous and anaerobic conditions.

[0024] The sulfonimide-based quasi-solid sulfonimide polymer flexible electrolyte material and the sulfonimide-based quasi-solid polymer flexible electrolyte material obtained by the preparation method thereof.

[0025] The application of the described sulfonimide-based quasi-solid polymer flexible electrolyte material in the preparation of lithium-ion batteries, lithium metal batteries, and flexible pouch lithium batteries.

[0026] The sulfonimide-based prepolymer for the quasi-solid sulfonimide polymer flexible electrolyte material has the following general structural formula:

[0027]

[0028] In the formula, R1 is selected from:

[0029] The structural formula of R2 is

[0030] R3 is selected from

[0031] R4 is selected from:

[0032] A method for preparing a sulfonimide polymer membrane material includes the following steps:

[0033] 1) React polyether polyol, sulfonimide polymer lithium salt capped with dihydroxy, small molecule polyhydroxy compound and diisocyanate under the catalysis of an anhydrous and anaerobic catalyst to obtain a sulfonimide-based prepolymer, and add a solvent for dilution during the reaction; the mass ratio of polyether polyol, sulfonimide polymer lithium salt capped with dihydroxy and diisocyanate is 1:1:1 to 5:5:1; the df of the small molecule polyhydroxy compound is 3 - 4, and the dosage accounts for 0.5% - 5% of the total feeding mass; the general structural formula of the prepared sulfonimide-based prepolymer is shown as follows:

[0034]

[0035] In the formula, R1 is selected from:

[0036] The structural formula of R2 is

[0037] R3 is selected from

[0038] R4 is selected from:

[0039] 2) Crosslink the prepared sulfonimide-based prepolymer with a small molecule polyhydroxy compound under the catalysis of an anhydrous and anaerobic catalyst to obtain a preliminarily crosslinked product solution; pour the solution into a circular polytetrafluoroethylene mold, conduct crosslinking reaction again and evaporate the solvent, and obtain a polymer membrane material after vacuum drying at the end of the reaction; wherein, the functionality df of the small molecule polyhydroxy compound is ≥15, and the dosage accounts for 1% - 20% of the total feeding mass.

[0040] Advantages: Compared with the prior art, the advantages of this application are as follows:

[0041] (1) The preparation method of the quasi-solid-state sulfonimide-based polymer flexible electrolyte material provided by this application has easily available raw materials, mild reaction conditions, simple preparation process, strong chain segment adjustability, and can be used for large-scale industrial production.

[0042] (2) The quasi-solid-state sulfonimide-based polymer flexible electrolyte material prepared by this application has the advantages of excellent mechanical properties, good electrochemical stability, and high ionic conductivity, and can be applied to fields such as lithium-ion batteries, lithium metal batteries, and flexible soft-pack lithium batteries. Description of the Drawings

[0043] Figure 1 is the variable-temperature ionic conductivity spectrum of the quasi-solid-state sulfonimide-based polymer flexible electrolyte material;

[0044] Figure 2 is the cyclic charge and discharge test data graph of the lithium metal battery prepared from the quasi-solid-state sulfonimide-based polymer flexible electrolyte material at a current density of 0.5C;

[0045] Figure 3 is the infrared spectrum of the sulfonimide-based prepolymer;

[0046] Figure 4 is the infrared spectrum of the sulfonimide polymer membrane material. Detailed Embodiments

[0047] The present invention will be further described below in conjunction with specific implementation cases.

[0048] Example 1

[0049] A preparation method of a quasi-solid-state sulfonimide-based polymer flexible electrolyte material based on sulfonimide is as follows:

[0050] 1) Under argon protection, 0.3334 g of isophorone diisocyanate and 0.5575 g of poly(propylene glycol)-block-poly(L glycol)-block-poly(propylene glycol) triblock polyether ( 0.0050 g of stannous octoate was added to 0.3334 g of isophorone diisocyanate and 0.7425 g of poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) triblock polyether (

[0051] Mn = 2700), and the mixture was stirred at 60 °C for 4 h with 3 mL of N,N-dimethylformamide added during the reaction for dilution. The product was further reacted with 0.0225 g of glycerol at 75 °C for 2 h with 2 mL of N,N-dimethylformamide added during the reaction for dilution. The product was then reacted with 0.5595 g of lithium trifluoromethanesulfonimide polymer salt at 85 °C for 3 h with 3 mL of N,N-dimethylformamide added during the reaction for dilution. After the reaction was completed, a sulfonimide-type prepolymer was obtained, and the product was stored in a solution state under argon protection.

[0052] 3) The obtained polymer membrane material was immersed in a mixed organic electrolyte of γ-butyrolactone and ethylene carbonate (volume ratio 9:1), and was fully swollen to an equilibrium state to obtain a sulfonimide-type quasi-solid polymer flexible electrolyte material.

[0053] Example 2

[0054] A preparation method of a sulfonimide-based quasi-solid sulfonimide-type polymer flexible electrolyte material is as follows:

[0055] 1) Under argon protection, 0.3334 g of isophorone diisocyanate and 0.7425 g of poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) triblock polyether ( Mn = 2700) were stirred at 85 °C for 2 h with 0.0030 g of dibutyltin dilaurate as a catalyst, and 2 mL of N,N-dimethylformamide was added during the reaction for dilution. The product was further reacted with 0.0270 g of trimethylolpropane at 85 °C for 3 h with 2 mL of N,N-dimethylformamide added during the reaction for dilution. The product was then reacted with 0.7460 g of lithium trifluoromethanesulfonimide polymer salt at 85 °C for 3 h with 3 mL of N,N-dimethylformamide added during the reaction for dilution. After the reaction was completed, a sulfonimide-type prepolymer was obtained, and the product was stored in a solution state under argon protection.

[0056] 2) 0.1130 g of hydroxyethyl-β-cyclodextrin was added to the sulfonimide-type prepolymer solution, and the mixture was stirred at 85 °C for 2 h under argon protection to obtain a preliminary cross-linked product solution. The solution was poured into a polytetrafluoroethylene disc mold, and further cross-linked at 85 °C for 12 h to evaporate the solvent. After vacuum drying at 85 °C for 12 h, a polymer membrane material was obtained.

[0057] 3) Immerse the obtained polymer membrane material in a mixed organic electrolyte of γ-butyrolactone and vinyl fluorocarbonate (volume ratio 1:1), and fully swell it to the equilibrium state to obtain a sulfonimide-based quasi-solid polymer flexible electrolyte material.

[0058] Example 3

[0059] A preparation method of a sulfonimide-based quasi-solid sulfonimide polymer flexible electrolyte material is as follows:

[0060] 1) Add 0.3334 g of isophorone diisocyanate and 0.8025 g of poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) triblock polyether ( Mn = 3300) to 0.0050 g of dibutyltin dilaurate as a catalyst and stir at 65 °C for 2 h under argon protection. During this period, add 2 mL of dimethyl sulfoxide for dilution. React the product with 0.0330 g of trimethylolpropane at 65 °C for another 3 h, and add 3 mL of dimethyl sulfoxide for dilution during this period. React the product with 0.7680 g of lithium salt of p-benzenesulfonimide polymer at 85 °C for 5 h, and add 3 mL of dimethyl sulfoxide for dilution during this period. After the reaction is completed, a sulfonimide-based prepolymer is obtained, and the product is kept in a solution state and stored under argon protection.

[0061] 2) Add 0.0875 g of β-cyclodextrin to the sulfonimide-based prepolymer solution and stir at 85 °C for 4 h under argon protection to obtain a preliminary cross-linked product solution. Pour the solution into a polytetrafluoroethylene disc mold, and conduct further cross-linking reaction at 100 °C for 6 h to evaporate the solvent. After vacuum drying at 100 °C for 18 h, a polymer membrane material is obtained.

[0062] 3) Immerse the obtained polymer membrane material in a mixed organic electrolyte of γ-valerolactone and vinyl fluorocarbonate (volume ratio 1:1), and fully swell it to the equilibrium state to obtain a sulfonimide-based quasi-solid polymer flexible electrolyte material.

[0063] Example 4

[0064] A preparation method of a sulfonimide-based quasi-solid sulfonimide polymer flexible electrolyte material is as follows:

[0065] 1) Add 0.3334 g of 4,4'-dicyclohexylmethane diisocyanate and 1.0000 g of poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) triblock polyether ( 0.0100 g of stannous octoate was added to 2000) and stirred at 100 °C for 1 h under argon protection. During this period, 4 mL of N-methylpyrrolidone was added for dilution. The product was continuously reacted with 0.0450 g of pentaerythritol at 100 °C for 2 h, and 3 mL of N-methylpyrrolidone was added for dilution during this period. The product was reacted with 0.8610 g of lithium salt of trifluorotoluenesulfonimide polymer at 85 °C for 3 h, and 2 mL of N-methylpyrrolidone was added for dilution during this period. After the reaction was completed, a sulfonimide-type prepolymer was obtained, and the product was stored in a solution state under argon protection.

[0066] 2) 0.0650 g of α-cyclodextrin was added to the sulfonimide-type prepolymer solution and stirred at 85 °C for 2 h under argon protection to obtain a preliminary cross-linked product solution. The solution was poured into a polytetrafluoroethylene disc mold and further cross-linked at 120 °C for 12 h to evaporate the solvent. After vacuum drying at 120 °C for 24 h, a polymer membrane material was obtained.

[0067] 3) The obtained polymer membrane material was immersed in an organic electrolyte of propylene carbonate and fully swollen to an equilibrium state to obtain a sulfonimide-type quasi-solid polymer flexible electrolyte material.

[0068] Example 5

[0069] A preparation method of a sulfonimide-type quasi-solid sulfonimide-based polymer flexible electrolyte material is as follows:

[0070] 1) 0.3334 g of 4,4′-dicyclohexylmethane diisocyanate and 0.6750 g of poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) triblock polyether ( Mn = 3300) were stirred at 80 °C for 3 h under the catalysis of 0.0030 g of stannous octoate under argon protection. During this period, 2 mL of N-methylpyrrolidone was added for dilution. The product was continuously reacted with 0.0175 g of glycerol at 80 °C for 3 h, and 2 mL of N-methylpyrrolidone was added for dilution during this period. The product was reacted with 0.5595 g of lithium salt of trifluoromethanesulfonimide polymer at 80 °C for 6 h, and 2 mL of N-methylpyrrolidone was added for dilution during this period. After the reaction was completed, a sulfonimide-type prepolymer was obtained, and the product was stored in a solution state under argon protection.

[0071] 2) 0.0750 g of γ-cyclodextrin was added to the sulfonimide-type prepolymer solution and stirred at 80 °C for 3 h under argon protection to obtain a preliminary cross-linked product solution. The solution was poured into a polytetrafluoroethylene disc mold and further cross-linked at 95 °C for 12 h to evaporate the solvent. After vacuum drying at 95 °C for 24 h, a polymer membrane material was obtained.

[0072] 3) Immerse the obtained polymer membrane material in an organic electrolyte of diethyl carbonate ∶ ethylene carbonate = 7 ∶ 3, and fully swell it to the equilibrium state to obtain a sulfonimide-based quasi-solid polymer flexible electrolyte material.

[0073] Example 6

[0074] A preparation method of a sulfonimide-based quasi-solid sulfonimide polymer flexible electrolyte material is as follows:

[0075] 1) Add 0.3334 g of 4,4′-dicyclohexylmethane diisocyanate and 1.3500 g of poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) triblock polyether ( Mn = 3300) to 0.0040 g of stannous octoate under the protection of argon and stir and react at 100 °C for 2 h. During this period, add 2 mL of N,N-dimethylformamide for dilution. React the product with 0.0650 g of pentaerythritol at 100 °C for another 3 h, and add 4 mL of N,N-dimethylformamide for dilution during this period. React the product with 0.7680 g of lithium salt of p-benzenesulfonimide polymer at 100 °C for 4 h, and add 2 mL of N,N-dimethylformamide for dilution during this period. After the reaction is completed, a sulfonimide-based prepolymer is obtained, and the product is kept in a solution state and stored under argon protection.

[0076] 2) Add 0.0950 g of β-cyclodextrin to the sulfonimide-based prepolymer solution and stir and react at 100 °C for 4 h under the protection of argon to obtain a preliminary cross-linked product solution. Pour the solution into a polytetrafluoroethylene disc mold, carry out further cross-linking reaction at 60 °C for 24 h and volatilize the solvent, and obtain a polymer membrane material after vacuum drying at 60 °C for 24 h.

[0077] 3) Immerse the obtained polymer membrane material in an organic electrolyte of dimethyl carbonate ∶ ethylene carbonate = 1 ∶ 1, and fully swell it to the equilibrium state to obtain a sulfonimide-based quasi-solid polymer flexible electrolyte material.

[0078] Example 7

[0079] A preparation method of a sulfonimide-based quasi-solid sulfonimide polymer flexible electrolyte material is as follows:

[0080] 1) Add 0.3334 g of 4,4′-dicyclohexylmethane diisocyanate and 0.8025 g of poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) triblock polyether ( Mn = 2700) was stirred and reacted at 85 °C for 4 h under the catalysis of 0.0040 g of dibutyltin dilaurate and under argon protection. During this period, 3 mL of dimethyl sulfoxide was added for dilution. The product was continuously reacted with 0.0300 g of trimethylolpropane at 85 °C for 2 h, and 3 mL of dimethyl sulfoxide was added for dilution during this period. The product was reacted with 1.2900 g of lithium salt of trifluorotoluenesulfonylimide polymer at 85 °C for 4 h, and 3 mL of dimethyl sulfoxide was added for dilution during this period. After the reaction was completed, a sulfonylimide-type prepolymer was obtained, and the product was stored in a solution state under argon protection.

[0081] 2) 0.1100 g of hydroxypropyl-β-cyclodextrin was added to the sulfonylimide-type prepolymer solution, and the mixture was stirred and reacted at 100 °C for 3 h under argon protection to obtain a preliminarily cross-linked product solution. The solution was poured into a polytetrafluoroethylene disc mold, and further cross-linking reaction was carried out at 120 °C for 12 h to volatilize the solvent. After vacuum drying at 120 °C for 24 h, a polymer membrane material was obtained.

[0082] 3) The obtained polymer membrane material was immersed in an organic electrolyte of diethyl carbonate∶ethylene carbonate = 7∶3, and was fully swollen to an equilibrium state to obtain a sulfonylimide-type quasi-solid polymer flexible electrolyte material.

[0083] Example 8

[0084] A preparation method of a sulfonylimide-type quasi-solid sulfonylimide polymer flexible electrolyte material is as follows:

[0085] 1) 0.3334 g of hexamethylene diisocyanate and 0.7000 g of poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) triblock polyether ( Mn = 2000) was stirred and reacted at 75 °C for 0.5 h under the catalysis of 0.0040 g of dibutyltin dilaurate and under argon protection. During this period, 2 mL of N-methylpyrrolidone was added for dilution. The product was continuously reacted with 0.0575 g of trimethylolpropane at 75 °C for 3 h, and 2 mL of N-methylpyrrolidone was added for dilution during this period. The product was reacted with 0.9700 g of lithium salt of trifluoromethanesulfonylimide polymer at 75 °C for 3 h, and 2 mL of N-methylpyrrolidone was added for dilution during this period. After the reaction was completed, a sulfonylimide-type prepolymer was obtained, and the product was stored in a solution state under argon protection.

[0086] 2) 0.0850 g of α-cyclodextrin was added to the sulfonylimide-type prepolymer solution, and the mixture was stirred and reacted at 85 °C for 3 h under argon protection to obtain a preliminarily cross-linked product solution. The solution was poured into a polytetrafluoroethylene disc mold, and further cross-linking reaction was carried out at 85 °C for 12 h to volatilize the solvent. After vacuum drying at 120 °C for 24 h, a polymer membrane material was obtained.

[0087] 3) Immerse the obtained polymer membrane material in an organic electrolyte of γ-butyrolactone∶ethylene carbonate = 9∶1, and fully swell it to the equilibrium state to obtain a sulfonimide-based quasi-solid polymer flexible electrolyte material.

[0088] Example 9

[0089] A preparation method of a sulfonimide-based quasi-solid sulfonimide polymer flexible electrolyte material is as follows:

[0090] 1) Add 0.3334 g of hexamethylene diisocyanate and 0.7425 g of poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) triblock polyether ( Mn = 3300) to 0.0080 g of stannous octoate under the protection of argon, stir and react at 60 °C for 1.5 h, and add 2 mL of N,N-dimethylformamide during this period. React the product with 0.0275 g of glycerol at 60 °C for another 4 h, and add 3 mL of N,N-dimethylformamide for dilution during this period. React the product with 0.5760 g of lithium salt of p-benzenesulfonimide polymer at 60 °C for 3 h, and add 2 mL of N,N-dimethylformamide for dilution during this period. After the reaction is completed, a sulfonimide-based prepolymer is obtained, and the product is kept in a solution state for storage under argon protection.

[0091] 2) Add 0.0750 g of γ-cyclodextrin to the sulfonimide-based prepolymer solution, stir and react at 85 °C for 2 h under the protection of argon to obtain a preliminary cross-linked product solution. Pour the solution into a polytetrafluoroethylene disc mold, carry out further cross-linking reaction at 85 °C for 6 h and evaporate the solvent, and obtain a polymer membrane material after vacuum drying at 100 °C for 12 h.

[0092] 3) Immerse the obtained polymer membrane material in an organic electrolyte of propylene carbonate∶ethylene carbonate = 1∶1, and fully swell it to the equilibrium state to obtain a sulfonimide-based quasi-solid polymer flexible electrolyte material.

[0093] Example 10

[0094] A preparation method of a sulfonimide-based quasi-solid sulfonimide polymer flexible electrolyte material is as follows:

[0095] 1) Add 0.3334 g of hexamethylene diisocyanate and 0.8500 g of poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) triblock polyether ( Mn = 2700) was stirred and reacted at 65 °C for 3 h under the protection of argon with 0.0050 g of stannous octoate as a catalyst, and 2 mL of dimethyl sulfoxide was added during the reaction. The product was continuously reacted with 0.0350 g of glycerol at 65 °C for 3 h, and 3 mL of dimethyl sulfoxide was added for dilution during the reaction. The product was reacted with 0.8610 g of lithium salt of trifluorotoluenesulfonylimide polymer at 65 °C for 3 h, and 2 mL of dimethyl sulfoxide was added for dilution during the reaction. After the reaction was completed, a sulfonimide-type prepolymer was obtained, and the product was stored in a solution state under the protection of argon.

[0096] 2) 0.0960 g of hydroxyethyl-β-cyclodextrin was added to the sulfonimide-type prepolymer solution, and the mixture was stirred and reacted at 85 °C for 3 h under the protection of argon to obtain a preliminarily crosslinked product solution. The solution was poured into a polytetrafluoroethylene disc mold, and further crosslinked at 120 °C for 24 h to volatilize the solvent. After vacuum drying at 120 °C for 12 h, a polymer membrane material was obtained.

[0097] 3) The obtained polymer membrane material was immersed in an organic electrolyte solution of propylene carbonate:ethylene carbonate = 1:1, and fully swollen to an equilibrium state to obtain a sulfonimide-type quasi-solid polymer flexible electrolyte material.

[0098] Example 11

[0099] A dumbbell-shaped spline was cut from any of the sulfonimide polymer membrane materials prepared in Examples 1-10 for tensile testing. The thickness of the spline was measured, and the tensile rate was 5 mm / min. The results are shown in Table 1, indicating that the obtained polymer membrane material has good mechanical properties and strong chain segment controllability.

[0100] Table 1. Tensile property test results of sulfonimide polymer membrane materials

[0101] Product Breaking stress (Mpa) Breaking strain (%) Example 1 5.80 80 Example 2 1.50 1350 Example 3 0.65 2170 Example 4 0.90 2790 Example 5 1.05 1200 Example 6 1.30 1170 Example 7 3.50 210 Example 8 4.00 450 Example 9 1.10 1450 Example 10 2.30 580

[0102] A dumbbell-shaped spline was cut from any of the quasi-solid sulfonimide-type polymer flexible electrolyte materials prepared in Examples 1-10 for tensile testing. The thickness of the spline was measured, and the tensile rate was 5 mm / min. The results are shown in Table 2, indicating that the obtained quasi-solid sulfonimide-type polymer flexible electrolyte material has good mechanical properties and strong chain segment controllability.

[0103] Table 2. Tensile property test results of quasi-solid sulfonimide-type polymer flexible electrolyte materials

[0104] Product Breaking stress (Kpa) Breaking strain (%) Example 1 550 220 Example 2 40 180 Example 3 20 50 Example 4 55 150 Example 5 60 165 Example 6 80 130 Example 7 180 250 Example 8 315 175 Example 9 70 110 Example 10 225 300

[0105] A dumbbell-shaped spline was cut from any of the quasi-solid sulfonimide-type polymer flexible electrolyte materials prepared in Examples 1-10 for ionic conductivity testing. It was cut into a disc with a diameter of 16 mm and assembled into a stainless steel / electrolyte material / stainless steel symmetric cell for variable temperature alternating current impedance testing. The results are as followsFigure 1 As shown (a, b, and c are the results of the variable-temperature AC impedance tests for Examples 1, 2, and 3 respectively), the room-temperature ionic conductivities of Examples 1-10 are all in the range of 5×10 -6 S cm -1 ~1×10 -3 S cm -1 range, and different quasi-solid-state sulfonimide-based polymer flexible electrolyte materials all exhibit relatively high ionic conductivities.

[0106] Figure 2 A lithium metal battery assembled with the quasi-solid-state sulfonimide-based polymer flexible electrolyte material prepared in Example 1 as the lithium metal anode / electrolyte material / lithium iron phosphate cathode was subjected to cyclic charge-discharge tests at a current density of 0.5C, showing good cycle stability. Lithium metal batteries assembled with the sulfonimide-based polymer flexible electrolyte materials prepared in Examples 2-10 with lithium iron phosphate as the positive electrode can all obtain good battery cycle effects.

[0107] Figure 3 The infrared spectrum obtained by testing the sulfonimide prepolymer prepared in Example 1. It can be clearly seen from the figure characteristic functional groups such as isocyanate groups, urethane groups, ether bonds, and sulfonimide groups, and the product structure is clear. Infrared characterizations of the sulfonimide prepolymers prepared in Examples 2-10 can all obtain spectra with corresponding characteristic functional groups.

[0108] Figure 4 The infrared spectrum obtained by testing the sulfonimide polymer membrane material prepared in Example 1. It can be clearly seen from the figure characteristic functional groups such as urethane groups, ether bonds, and sulfonimide groups. The characteristic isocyanate group (2255 cm -1 ) in the prepolymer spectrum disappears, proving that the polymerization reaction is complete and the product structure is clear. Infrared characterizations of the sulfonimide polymer membrane materials prepared in Examples 2-10 can all obtain spectra with corresponding characteristic functional groups.

Claims

1. A preparation method of a flexible electrolyte material based on sulfonimide lithium quasi-solid polymer, characterized in that, it includes the following steps: 1) Under the catalysis of an anhydrous and anaerobic catalyst, polyether polyol, small molecule polyhydroxy compound, bis-hydroxy-terminated sulfonimide polymer lithium salt and diisocyanate are successively added to react to obtain a sulfonimide-type prepolymer, and a solvent is added for dilution during the reaction process; the mass ratio of polyether polyol, bis-hydroxy-terminated sulfonimide polymer lithium salt and diisocyanate is 1∶1∶1 to 5∶5∶1; the functionality df of the small molecule polyhydroxy compound is 3 to 4, and the dosage accounts for 0.5% to 5% of the total feeding mass; the structural general formula of the prepared sulfonimide-type prepolymer is as follows: In the formula, R1 is selected from: The structural formula of R2 is R3 is selected from R4 is selected from: 2) The prepared sulfonimide-type prepolymer and the small molecule polyhydroxy compound are subjected to a cross-linking reaction under the catalysis of an anhydrous and anaerobic catalyst to obtain a preliminarily cross-linked product solution; The solution is poured into a circular polytetrafluoroethylene mold, and the cross-linking reaction is carried out again and the solvent is volatilized. After the reaction is completed, vacuum drying is carried out to obtain a polymer membrane material; among them, the functionality df of the small molecule polyhydroxy compound is ≥15, and the dosage accounts for 1% to 20% of the total feeding mass; 3) The obtained polymer membrane material is immersed in an organic electrolyte solution and fully swollen to an equilibrium state to prepare a sulfonimide-type quasi-solid polymer flexible electrolyte material.

2. The preparation method of the flexible electrolyte material based on sulfonimide lithium quasi-solid polymer according to claim 1, characterized in that, the diisocyanate is selected from one or more of 4,4′-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate; the polyether polyol is poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) triblock polyether, and the number average molecular weight is one or a mixture of 2000, 2700, 3300; the small molecule polyhydroxy compound in step 1) is selected from one or a mixture of glycerol, trimethylolpropane, pentaerythritol; the small molecule polyhydroxy compound in step 2) is selected from one or a mixture of α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin, hydroxyethyl-β-cyclodextrin, hydroxypropyl-β-cyclodextrin; the sulfonimide polymer lithium salt is selected from one or a mixture of p-trifluoromethylbenzenesulfonimide polymer lithium salt, p-benzenesulfonimide polymer lithium salt, trifluoromethanesulfonimide polymer lithium salt.

3. The preparation method of the flexible electrolyte material based on sulfonimide lithium quasi-solid polymer according to claim 1, characterized in that, the catalyst is selected from one or a mixture of stannous octoate, dibutyltin dilaurate; the solvent is selected from one or a mixture of dimethyl sulfoxide, N,N-dimethylformamide, N-methylpyrrolidone.

4. The preparation method of the flexible electrolyte material based on sulfonimide lithium quasi-solid polymer according to claim 1, characterized in that, the organic electrolyte is selected from one or a mixture of dimethyl carbonate, diethyl carbonate, ethylene carbonate, fluoroethylene carbonate, propylene carbonate, γ-butyrolactone, γ-valerolactone.

5. The preparation method of the flexible electrolyte material based on lithium sulfonimide quasi-solid polymer according to claim 1, characterized in that, in step 1), polyether polyol, lithium salt of bis-hydroxy-terminated sulfonimide polymer, small molecule polyhydroxy compound and diisocyanate are reacted for 0.5 - 20 hours under the catalysis of an anhydrous and anaerobic catalyst at 60 - 100 °C to obtain a sulfonimide-type prepolymer, and 1 - 20 mL of solvent is added for dilution during the reaction; the sulfonimide-type prepolymer is stored in a solution under anhydrous and anaerobic conditions.

6. The preparation method of the flexible electrolyte material based on lithium sulfonimide quasi-solid polymer according to claim 1, characterized in that, in step 2), the sulfonimide-type prepolymer and the small molecule polyhydroxy compound are reacted for 0.5 - 6 hours under the catalysis of an anhydrous and anaerobic catalyst at 60 - 100 °C to obtain a preliminary cross-linked product solution; the solution is poured into a circular polytetrafluoroethylene mold, and cross-linking reaction is carried out at 60 - 120 °C for 6 - 24 hours to volatilize the solvent, and after vacuum drying at 60 - 120 °C for 6 - 24 hours, a polymer membrane material is obtained and stored under anhydrous and anaerobic conditions.

7. The sulfonimide-type quasi-solid polymer flexible electrolyte material obtained by the preparation method of the flexible electrolyte material based on lithium sulfonimide quasi-solid polymer according to any one of claims 1 - 6.

8. The application of the sulfonimide-type quasi-solid polymer flexible electrolyte material according to claim 7 in the preparation of lithium-ion batteries, lithium metal batteries and flexible soft-pack lithium batteries.

9. A sulfonimide-type prepolymer for a quasi-solid sulfonimide-type polymer flexible electrolyte material, characterized in that, the structural general formula is as follows: In the formula, R1 is selected from: The structural formula of R2 is R3 is selected from R4 is selected from:

10. A method for preparing a sulfonimide-type polymer membrane material, characterized in that, comprises the following steps: 1) Polyether polyol, lithium salt of bis-hydroxy-terminated sulfonimide polymer, small molecule polyhydroxy compound and diisocyanate are reacted under the catalysis of an anhydrous and anaerobic catalyst to obtain a sulfonimide-type prepolymer, and solvent is added for dilution during the reaction; the mass ratio of polyether polyol, lithium salt of bis-hydroxy-terminated sulfonimide polymer and diisocyanate is 1∶1∶1 - 5∶5∶1; the functionality df of the small molecule polyhydroxy compound is 3 - 4, and the dosage accounts for 0.5% - 5% of the total feeding mass; the structural general formula of the prepared sulfonimide-type prepolymer is as follows: In the formula, R1 is selected from: The structural formula of R2 is R3 is selected from R4 is selected from: 2) The prepared sulfonimide-type prepolymer and the small molecule polyhydroxy compound are subjected to a cross-linking reaction under the catalysis of an anhydrous and anaerobic catalyst to obtain a preliminary cross-linked product solution; the preliminary cross-linked product solution is poured into a circular polytetrafluoroethylene mold, and cross-linking reaction is carried out again to volatilize the solvent, and after the reaction is completed and vacuum dried, a polymer membrane material is obtained; wherein, the functionality df of the small molecule polyhydroxy compound is ≥15, and the dosage accounts for 1% - 20% of the total feeding mass.

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