A method for preparing a titanium carbide-doped polymer solid-state electrolyte

Abstract

The application discloses a preparation method of a titanium carbide doped polymer solid electrolyte, which can effectively reduce the crystallinity of PEO, enhance the ionic conductivity of the polymer solid electrolyte and widen the electrochemical window by grafting PCL (polycaprolactone) on the surface of a two-dimensional material titanium carbide (MXene) and blending the PCL with a PEO (polyethylene oxide) blend.The steps adopted by the application are as follows: firstly, PCL is grafted on the surface of MXene through a one-pot method; then, the grafted material is mixed with PEO and LiTFSI (lithium bis(trifluoromethanesulfonyl)imide) in a certain proportion, is subjected to ultrasonic oscillation and is uniformly mixed by heating; finally, the solution is poured on a glass culture medium, the solvent is volatilized at room temperature, the solvent is removed by heating, and a solid polymer electrolyte film is obtained.The polymer solid electrolyte film prepared by the method of the application has good mechanical properties, high ionic conductivity, a wide electrochemical stability window, stable charge and discharge processes of an assembled battery and excellent cycle performance.

Description

Technical Field

[0001] This invention relates to the technical field of methods for preparing polyethylene oxide solid electrolytes for lithium batteries. Background Technology

[0002] Currently, lithium-ion batteries, as a new type of energy storage device, have advantages such as high energy density, long lifespan, and high operating voltage. They have been widely used in mobile phones, automobiles, and other areas of daily life, and lithium-ion batteries have become an indispensable technology in human life.

[0003] Electrolytes are a crucial component of lithium-ion battery systems, located between the positive and negative electrodes. They act as a bridge between the two electrodes, connecting them and playing a vital role in transferring and transporting lithium ions during battery operation. Currently, electrolytes are mainly classified into organic liquid electrolytes and solid electrolytes. Current research indicates that traditional organic liquid electrolytes pose risks such as internal short circuits, leakage, volatile gas expansion, flammability, and even explosion. Furthermore, the energy density of lithium-ion batteries using traditional organic liquid electrolytes is nearing its peak and is difficult to increase further, failing to meet future battery development trends. Therefore, solid electrolytes are currently a hot research topic. Solid electrolytes are mainly divided into two categories: inorganic solid electrolytes and solid polymer electrolytes. Inorganic solid electrolytes possess advantages such as high elastic modulus, thermal stability, a wide electrochemical window, and low flammability; however, they may react with metallic lithium, potentially causing safety issues.

[0004] Compared to traditional organic liquid electrolytes and inorganic solid electrolytes, solid polymer electrolytes offer advantages such as ease of processing, light weight, low manufacturing cost, high flexibility, low interfacial resistance, and the ability to change shape with electrode volume during battery charging and discharging. Current theory suggests that solid polymer electrolytes achieve lithium-ion transport through localized chain segment movement in amorphous regions. As research into solid polymer electrolytes deepens, the types of polymers that can be used as matrix materials are gradually increasing. PEO is the earliest recorded polyether polymer matrix material used in lithium-ion batteries. + It can coordinate with the polar functional group −O− in PEO, and free volumes are formed when polymer chain segments move locally. Under the action of an external electric field, Li + These free volumes facilitate the transfer of energy between or within polymer chains. However, traditional PEO-based polymer electrolytes suffer from drawbacks such as low ionic conductivity, high interfacial resistance, low ion transference number, and narrow electrochemical window. Preparing composite electrolytes is a simple and effective method to improve the performance of PEO solid electrolytes. The added composite material can act as a crosslinking center for PEO, thereby disrupting polymer rearrangement, reducing crystallinity, and increasing the ionic conductivity and electrochemical window of the PEO-based polymer electrolyte. Summary of the Invention

[0005] The purpose of this invention is to address the problems and shortcomings of the prior art and to provide a method for preparing titanium carbide-doped polymer solid electrolytes.

[0006] The technical solution proposed by this invention to address the above-mentioned technical problems is as follows: A method for preparing a titanium carbide-doped polymer solid electrolyte includes the following steps: (a) Preparation of MXene: First, 20 mL of 9 M hydrochloric acid is added to a polytetrafluoroethylene beaker, followed by the sequential addition of lithium fluoride and aluminum carbide. The mixture is then heated in an oil bath at 40°C for 24 hours. After 24 hours, the mixture is washed with deionized water, emulsified, dispersed, and ultrasonically exfoliated to obtain a dark green MXene aqueous solution. (b) Preparation of PCL-grafted MXene: α-caprolactone monomer and MXene are added to a flask, nitrogen gas is introduced for 20 min, and the mixture is heated in an oil bath. When the temperature reaches 120°C, a catalyst is added, and the mixture is heated in an oil bath at 120°C for 24 h. The resulting product is dried under vacuum at 100°C for 4 h to obtain PCL-grafted MXene. (c) Preparation of titanium carbide-doped polymer solid electrolyte: PCL-grafted MXene was mixed with PEO and LiTFSI in a specified ratio, solvent was added, and the mixture was stirred at 500 rpm for 3 h in an oil bath at 45 °C. The mixture was then transferred to a petri dish, dried at room temperature in a fume hood for 8 h, and dried on a hot table at 70 °C for 4 h.

[0007] In step (a), the mass of lithium fluoride is 0.88 g and the mass of aluminum carbide is 1.00 g.

[0008] In step (a), the number of times the deionized water is washed is 5-6, and the pH of the MXene aqueous solution should be neutral.

[0009] In step (a), the ultrasonic emulsification dispersion power is 40% and the time is 60 minutes.

[0010] In step (b), the MXene two-dimensional material should be centrifuged before use to replace the solvent with DMF (N,N-dimethylformamide).

[0011] In step (b), α-caprolactone monomer and MXene are purged with nitrogen for 20 minutes to remove oxygen, and then mixed in a container at a volume ratio of 11-15:9-12.

[0012] In step (b), the catalyst is stannous octoate with a concentration of 23 wt.% and a volume of 0.25-0.5 mL.

[0013] In step (c), the solvent is chloroform, and the amount added is 10-25 times the total mass of the solids.

[0014] In step (c), the PCL-grafted MXene, PEO and LiTFSI are mixed in a specified ratio of 5-3:4-7:1 by mass.

[0015] In step (c), the molecular weight of the PEO used is 300,000-500,000 g / mol.

[0016] Compared with existing technologies, the present invention has the following beneficial technical achievements: This invention discloses a method for preparing a titanium carbide-doped polymer solid electrolyte. The polymer solid electrolyte prepared by this method exhibits good mechanical properties, a lower melting point, high ionic conductivity, a wide electrochemical stability window, and stable charge-discharge process and excellent cycle performance when assembled into a battery. Attached Figure Description

[0017] Figure 1 The image shows a scanning electron microscope (SEM) image of MXene grafted onto PCL in Example 1.

[0018] Figure 2 Thermogravimetric analysis (TGA) curves for MXene-grafted PCL.

[0019] Figure 3 The DSC curves for the titanium carbide-doped polymer solid electrolyte of Example 2, and for pure PEO and LiTFSI are shown. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0021] Preparation of MXene: First, 20 mL of 9 M hydrochloric acid was added to a polytetrafluoroethylene beaker, followed by the addition of 0.88 g of lithium fluoride and 1.00 g of aluminum carbide. The mixture was then in an oil bath at 40 °C for 24 hours. After 24 hours, the mixture was washed six times with deionized water until the pH was neutral. The mixture was then emulsified, dispersed, and ultrasonically exfoliated at 40% power for 60 minutes to obtain a dark green MXene aqueous solution.

[0022] Preparation of PCL-grafted MXene: 11 mL of α-caprolactone monomer and 9 mL of MXene were added to a flask, nitrogen gas was purged for 20 min, and the mixture was heated in an oil bath. When the temperature reached 120 °C, 23 wt.% of 0.25 mL of stannous octoate was added, and the mixture was heated in an oil bath at 120 °C for 24 h. The resulting product was dried under vacuum at 100 °C for 4 h to obtain PCL-grafted MXene.

[0023] Preparation of titanium carbide-doped polymer solid electrolyte: 0.8 g PCL-grafted MXene was mixed with 1.0 g PEO (50000 g / mol) and 0.2 g LiTFSI, and 40 g chloroform was added. The mixture was stirred at 500 rpm for 3 h in an oil bath at 45 °C, transferred to a glass petri dish, dried at room temperature in a fume hood for 8 h, and then dried on a hot stage at 70 °C for 4 h.

[0024] SEM image of PCL-grafted MXene in Example 1 is shown below. Figure 1 As shown, the surface is covered with a layer of polymer.

[0025] The TGA curve of MXene grafted with PCL in Example 1 is as follows: Figure 2 As shown, the mass ratio of PCL to MXene is 88:11.

[0026] Preparation of MXene: First, 20 mL of 9 M hydrochloric acid was added to a polytetrafluoroethylene beaker, followed by the addition of 0.88 g of lithium fluoride and 1.00 g of aluminum carbide. The mixture was then in an oil bath at 40 °C for 24 hours. After 24 hours, the mixture was washed six times with deionized water until the pH was neutral. The mixture was then emulsified, dispersed, and ultrasonically exfoliated at 40% power for 60 minutes to obtain a dark green MXene aqueous solution.

[0027] Preparation of PCL-grafted MXene: 15 mL of α-caprolactone monomer and 12 mL of MXene were added to a flask, nitrogen gas was purged for 20 min, and the mixture was heated in an oil bath. When the temperature reached 120 °C, 23 wt.% of 0.5 mL of stannous octoate was added, and the mixture was heated in an oil bath at 120 °C for 24 h. The resulting product was dried under vacuum at 100 °C for 4 h to obtain PCL-grafted MXene.

[0028] Preparation of titanium carbide-doped polymer solid electrolyte: 0.6 g PCL-grafted MXene was mixed with 1.4 g PEO (30000 g / mol) and 0.3 g LiTFSI, and 20 g chloroform was added. The mixture was stirred at 500 rpm for 3 h in an oil bath at 45 °C, transferred to a glass petri dish, dried at room temperature in a fume hood for 8 h, and then dried on a hot stage at 70 °C for 4 h.

[0029] The DSC curves of the titanium carbide-doped polymer solid electrolyte in Example 2, compared with those of pure PEO and LiTFSI, are shown below. Figure 3 As shown, the melting point of the composite material is significantly reduced.

[0030] The above-described embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A method of producing a titanium carbide-doped polymer solid-state electrolyte, characterized by, Includes the following steps: (a) Preparation of MXene: First, 20 mL of 9 M hydrochloric acid was added to a polytetrafluoroethylene beaker, followed by the addition of lithium fluoride and aluminum carbide. The mixture was then placed in an oil bath at 40°C for 24 hours. After 24 hours, the mixture was washed with deionized water, emulsified, dispersed, and ultrasonically exfoliated to obtain a dark green aqueous solution of MXene. (b) Preparation of PCL-grafted MXene: α-caprolactone monomer and MXene were added to a flask, nitrogen was introduced for 20 min, and the mixture was heated in an oil bath. When the temperature reached 120 °C, the catalyst was added, and the mixture was heated in an oil bath at 120 °C for 24 h. The resulting product was dried under vacuum at 100 °C for 4 h to obtain PCL-grafted MXene. (c) Preparation of titanium carbide-doped polymer solid electrolyte: PCL-grafted MXene was mixed with PEO and LiTFSI in a specified ratio, solvent was added, and the mixture was stirred at 500 rpm for 3 h in an oil bath at 45℃. The mixture was then transferred to a petri dish, dried at room temperature in a fume hood for 8 h, and dried on a hot table at 70℃ for 4 h.

2. The production method according to claim 1, characterized by, In step (a), the mass of lithium fluoride is 0.88 g and the mass of aluminum carbide is 1.00 g.

3. The production method according to claim 1, characterized by, In step (a), the number of times the deionized water is washed is 5-6, and the pH of the MXene aqueous solution should be neutral.

4. The method of claim 1, wherein, In step (a), the ultrasonic emulsification dispersion power is 40% and the time is 60 minutes.

5. The preparation method according to claim 1, characterized in that, In step (b), the MXene two-dimensional material should be centrifuged before use to replace the solvent with DMF (N,N-dimethylformamide).

6. The preparation method according to claim 1, characterized in that, In step (b), α-caprolactone monomer and MXene are purged with nitrogen for 20 minutes to remove oxygen, and then mixed in a container at a volume ratio of 11-15:9-12.

7. The preparation method according to claim 1, characterized in that, In step (b), the catalyst is stannous octoate with a concentration of 23 wt.% and a volume of 0.25-0.5 mL.

8. The preparation method according to claim 1, characterized in that, In step (c), the solvent is chloroform, and the amount added is 10-25 times the total mass of the solids.

9. The preparation method according to claim 1, characterized in that, In step (c), the PCL-grafted MXene, PEO and LiTFSI are mixed in a specified ratio of 5-3:4-7:1 by mass.

10. The preparation method according to claim 1, characterized in that, In step (c), the molecular weight of the PEO used is 300,000-500,000 g / mol.

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