Stress-responsive solid-state electrolyte-based solid-state lithium battery and method of making the same

Abstract

The application relates to the technical field of solid-state lithium batteries, and discloses a stress response type solid-state electrolyte-based solid-state lithium battery and a preparation method thereof. The battery comprises a positive electrode of a lithium iron phosphate material, a negative electrode of a lithium metal sheet, and a stress response type solid-state electrolyte arranged between the positive electrode and the negative electrode. The stress response type solid-state electrolyte comprises a core-sheath type heterogeneous nanofiber piezoelectric film, polyethylene oxide (PEO) and lithium bis-trifluoromethanesulfonimide. The core-sheath type heterogeneous nanofiber piezoelectric film takes polyvinylidene fluoride-trifluoroethylene as a core layer and takes bromoacetylated cellulose acetate as a sheath layer. The core-sheath type heterogeneous nanofiber piezoelectric film realizes the dual-function synergy of "piezoelectric response inhibiting dendrites + interface coordination fast conduction". The ion conductivity is significantly improved, lithium dendrites are long-effectively inhibited, the solid-state lithium battery has a long cycle life and high safety. The coaxial electrospinning and solution casting process are combined, the preparation process is simple and scalable, and the application is suitable for the industrialization of the solid-state lithium battery.

Description

Technical Field

[0001] This invention relates to the field of solid-state lithium battery technology, specifically to a stress-responsive solid electrolyte-based solid-state lithium battery and its preparation method. Background Technology

[0002] Driven by the dual-carbon goals and the rapid development of the new energy industry, high-safety, high-energy-density energy storage systems have become a key focus of industry research and development. Solid-state lithium metal batteries, which use solid electrolytes to replace the traditional "electrolyte + separator" system, have significant advantages in energy density and safety, representing a new generation of technology that breaks through the bottlenecks of traditional lithium batteries.

[0003] Polyethylene oxide (PEO)-based polymer solid electrolytes have been widely studied due to their good processability, low interfacial impedance, and excellent flexibility. However, they have two major bottlenecks: first, low ionic conductivity, which limits lithium-ion transport; and second, poor mechanical properties, which make it difficult to suppress lithium dendrite growth, easily leading to battery capacity decay, short circuits, or even safety accidents.

[0004] Existing technologies enhance ionic conductivity or mechanical strength through chemical modification, molecular design, and filler addition, but simultaneously fail to achieve efficient ion transport and long-term lithium dendrite suppression. Physical barriers alone cannot maintain a stable negative electrode interface over the long term, ultimately leading to decreased battery coulombic efficiency and rapid capacity decay. Therefore, developing solid-state electrolyte-based solid-state lithium batteries that combine rapid ion conduction with intelligent stress-response dendrite suppression is a pressing technical challenge in this field. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art and provide a stress-responsive solid electrolyte-based solid lithium battery and its preparation method. By using a core-sheath heterogeneous nanofiber piezoelectric film to achieve rapid lithium ion transport and uniform deposition, the invention solves the problems of limited ion conduction and difficulty in suppressing lithium dendrites in traditional polymer solid electrolytes, thereby improving the cycle stability and safety of solid lithium batteries.

[0006] The technical solution adopted in this invention is: a stress-responsive solid electrolyte-based solid lithium battery, comprising a positive electrode of lithium iron phosphate material (LiFePO4), a negative electrode of lithium (Li) metal sheet, and a stress-responsive solid electrolyte disposed between the positive and negative electrodes; the stress-responsive solid electrolyte comprises a core-sheath heterostructure nanofiber piezoelectric membrane, polyethylene oxide (PEO), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI); the core-sheath heterostructure nanofiber piezoelectric membrane has polyvinylidene fluoride-trifluoroethylene (PVT) as the core layer and bromoacetylated cellulose acetate (Br-CA) as the sheath layer.

[0007] The core-sheath heterogeneous nanofiber piezoelectric membrane accounts for 30%-60% of the mass of the stress-responsive solid electrolyte.

[0008] The molar ratio of ethylene oxide structural units in the polyethylene oxide to lithium in the lithium bis(trifluoromethanesulfonylimide) is 8-18.

[0009] The core-sheath heterogeneous nanofiber piezoelectric film has a thickness of 15-25 μm, and the stress-responsive solid electrolyte has a thickness of 25-35 μm.

[0010] A method for preparing a stress-responsive solid electrolyte-based solid-state lithium battery, characterized by comprising the following steps: Step 1: Preparation of bromoacetylated cellulose acetate powder: Dissolve cellulose acetate in N,N-dimethylformamide, add bromoacetyl bromide in an ice-water bath and react, then precipitate, wash and dry to obtain bromoacetylated cellulose acetate powder; Step 2: Preparation of core-sheath heterogeneous nanofiber piezoelectric membrane: Using a mixture of N,N-dimethylformamide (DMF) and acetone (AC) as solvent, polyvinylidene fluoride-trifluoroethylene core spinning solution and bromoacetylated cellulose acetate sheath spinning solution were prepared respectively. Core-sheath polyvinylidene fluoride-trifluoroethylene / bromoacetylated cellulose acetate heterogeneous nanofiber piezoelectric membrane was prepared by coaxial electrospinning. Step 3: Preparation of stress-responsive solid electrolyte: Polyethylene oxide (PEO) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) are dissolved in acetonitrile to prepare a mixed solution. The solution is then filled into a core-sheath heterostructure nanofiber piezoelectric membrane by solution casting, and then dried under vacuum to obtain a stress-responsive solid electrolyte. Step 4: Assemble the solid-state lithium battery: Using lithium iron phosphate as the positive electrode and lithium metal sheet as the negative electrode, place the stress-responsive solid electrolyte obtained in Step 3 between the positive and negative electrodes to assemble a stress-responsive solid electrolyte-based solid-state lithium battery.

[0011] In step one, 10g of cellulose acetate was dissolved in 150mL of N,N-dimethylformamide, and 11g of bromoacetyl bromide was added. The reaction was carried out at 0℃ for 2h and at room temperature for 24h. The product was washed with deionized water and dried at 60℃ to obtain bromoacetylated cellulose acetate powder.

[0012] In step two, the core spinning solution concentration is 8-15 wt%, and the sheath spinning solution concentration is 10-20 wt%; the coaxial electrospinning voltage is 15-25 kV, the receiving distance is 15-25 cm, and the solution extrusion speed is 0.2-0.6 mL / h.

[0013] In step three, the molar ratio of ethylene oxide unit (ethylene oxide, a structural unit in polyethylene oxide) to lithium is 8-18, the vacuum drying temperature is 50-70℃, and the core-sheath heterogeneous nanofiber piezoelectric film accounts for 30%-60% of the total mass of the solid electrolyte.

[0014] In step two, the mass ratio of N,N-dimethylformamide to acetone used in the core spinning solution is 8:2, and the mass ratio of N,N-dimethylformamide to acetone used in the sheath spinning solution is 6:4.

[0015] The beneficial effects of this invention are: the core layer of polyvinylidene fluoride-trifluoroethylene has excellent piezoelectric effect and electromechanical coupling characteristics. When it is deformed by the mechanical stress generated by the lithium protrusion, it generates a reverse piezoelectric overpotential, which inhibits the deposition of lithium ions at the tip, guides their uniform distribution, and dynamically inhibits lithium dendrites.

[0016] The sheath of bromoacetylated cellulose acetate is rich in hydroxyl groups, ester groups, ether bonds and bromine coordination sites, which synergistically form a continuous interfacial ion conduction channel with the ether oxygen bond of polyethylene oxide, thus significantly improving ion conductivity.

[0017] Synergistic effect: Simultaneous realization of "rapid ion transport + uniform deposition" enables solid-state lithium batteries to have high ionic conductivity, long cycle life and high safety.

[0018] This invention presents a core-sheath heterogeneous nanofiber piezoelectric membrane that achieves a dual-function synergy of "piezoelectric response to suppress dendrites + interfacial coordination for rapid conduction." This significantly improves ionic conductivity, effectively suppresses lithium dendrites, and results in long cycle life and high safety for solid-state lithium batteries. The fabrication process combines coaxial electrospinning and solution casting, making it simple, scalable, and suitable for industrial applications of solid-state lithium batteries.

[0019] The stress-responsive solid electrolyte of this invention introduces a core-sheath heterostructure nanofiber (PVT / Br-CA) piezoelectric film, which promotes efficient ion transport and guides uniform ion deposition in the electrolyte. This solves the problem of limited ion transport and inability to suppress dendrite growth in polymer electrolytes. The prepared stress-responsive solid electrolyte has excellent ionic conductivity and long-term cycling stability. Attached Figure Description

[0020] Figure 1 This is a comparison of the XPS spectra of bromoacetylated cellulose acetate and the raw material cellulose acetate in Example 3; Figure 2 The images shown are of the core-sheath heterostructured nanofibers in Example 3, where (a) is a SEM image of the piezoelectric film of the core-sheath heterostructured nanofibers; (b) and (c) are HRTEM images of a single core-sheath heterostructured nanofiber at different scales. Figure 3 The diagram shows the butterfly-shaped amplitude and phase curves of the stress-responsive solid electrolyte in Example 3. Figure 4 This is a comparison chart of the ionic conductivity of the electrolytes in Example 3 and Comparative Examples 1-3; Figure 5Example 3: Li⁺ plating / stripping cycle diagram of a Li / Li symmetric cell with a stress-responsive solid electrolyte; Figure 6 The graph shows the cycle performance of the stress-responsive solid electrolyte-based solid lithium battery in Example 3 at 50°C and 1C rate. Detailed Implementation

[0021] The above-mentioned solution will be further described below with reference to specific embodiments; it should be understood that these embodiments are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following embodiments; the implementation conditions used in the embodiments can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions in conventional experiments.

[0022] Example 1: A stress-responsive solid electrolyte-based solid-state lithium battery is prepared according to the following steps: Step 1: Preparation of bromoacetylated cellulose acetate: 10g of cellulose acetate (CA) was dried in a vacuum oven at 60℃ for 12h and then dissolved in 150mL of N,N-dimethylformamide (DMF). The solution was stirred until completely dissolved, and 11g of bromoacetyl bromide was added in an ice-water bath. The reaction was continued to be stirred at 0℃ for 2h, and then stirred at room temperature for 24h. The solution after the reaction was poured into 1500ml of deionized water, and a large amount of pale yellow solid precipitated. The pale yellow solid product was repeatedly washed with deionized water and filtered, and then dried in an oven at 60℃ to obtain bromoacetylated cellulose acetate (Br-CA) powder.

[0023] Step 2: Preparation of core-sheath heterogeneous nanofiber (PVT / Br-CA) piezoelectric film: Using a mixture of N,N-dimethylformamide (DMF) and acetone (AC) as solvent, with a mass ratio of N,N-dimethylformamide:acetone = 6:4, 1.2 g of brominated acetic acid acetate (Br-CA) was dissolved in 8.8 g of the mixture to prepare a 12 wt% bromoacetic acid acetate (Br-CA) sheath spinning solution; using the mixture of N,N-dimethylformamide (DMF) and acetone (AC) as solvent, with a mass ratio of N,N-dimethylformamide:acetone = 6:4, ... A 10.2 wt% polyvinylidene fluoride-trifluoroethylene (PVT) core-sheath spinning solution was prepared by dissolving 1 g of PVT powder in a mixture of 8.8 g of DMF and AC. The ratio of N,N-dimethylformamide to acetone was 8:2. Using coaxial electrospinning technology, the core and sheath layers were electrospun at an extrusion speed of 0.2 mL / h under conditions of 15 kV positive voltage and -2 kV negative voltage, with a spinning receiving distance of 15 cm. The resulting core-sheath heterogeneous nanofiber (PVT / Br-CA) piezoelectric film, approximately 15 μm thick, was collected on a collecting roller. PVT is an abbreviation for P(VDF-TrFE).

[0024] Step 3: Preparation of stress-responsive solid electrolyte: Polyethylene oxide (PEO) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) are dissolved in anhydrous acetonitrile, controlling the molar ratio of ethylene oxide units in PEO to lithium in LiTFSI to be 8:1. The mass fraction of PEO in the mixed solution is 12%. The mixed solution is cast onto a core-sheath heterostructure nanofiber (PVT / Br-CA) piezoelectric film and smoothed with a scraper. It is then dried in a vacuum drying oven at 50°C for 24 h. The resulting stress-responsive solid electrolyte, with a thickness of approximately 25 μm, is obtained. The solid electrolyte prepared by this process is named PVT / Br-CA / PEO / LiTFSI, i.e., stress-responsive solid electrolyte. The amount of PEO / LiTFSI solution is controlled so that the mass of the core-sheath heterostructure nanofiber (PVT / Br-CA) piezoelectric film accounts for approximately 30% of the total mass of the stress-responsive solid electrolyte after drying.

[0025] Step 4: Assemble the solid-state lithium battery: Using lithium iron phosphate as the positive electrode and lithium metal sheet as the negative electrode, place the stress-responsive solid electrolyte obtained in Step 3 between the positive and negative electrodes to assemble a stress-responsive solid electrolyte-based solid-state lithium battery. The process uses existing technology.

[0026] Example 2: A stress-responsive solid electrolyte-based solid-state lithium battery is prepared according to the following steps: Step 1: Preparation of bromoacetylated cellulose acetate: 10g of cellulose acetate (CA) was dried in a vacuum oven at 60℃ for 12h and then dissolved in 150mL of N,N-dimethylformamide (DMF). The solution was stirred until completely dissolved, and 11g of bromoacetyl bromide was added in an ice-water bath. The reaction was continued to be stirred at 0℃ for 2h, and then stirred at room temperature for 24h. The solution after the reaction was poured into 1500ml of deionized water, and a large amount of pale yellow solid precipitated. The pale yellow solid product was repeatedly washed with deionized water and filtered, and then dried in an oven at 60℃ to obtain bromoacetylated cellulose acetate (Br-CA) powder.

[0027] Step 2: Preparation of core-sheath heterogeneous nanofiber (PVT / Br-CA) piezoelectric film: Using a mixture of N,N-dimethylformamide (DMF) and acetone (AC) as solvent, with a mass ratio of N,N-dimethylformamide:acetone = 6:4, 1.2 g of bromoacetylated cellulose acetate (Br-CA) was dissolved in 8.8 g of the mixture to prepare a 12 wt% bromoacetylated cellulose acetate (Br-CA) sheath spinning solution; Using a mixture of N,N-dimethylformamide (DMF) and acetone (AC) as solvent, with a mass ratio of N,N-dimethylformamide:acetone = 8:2, 1 g of polyvinylidene fluoride-trifluoroethylene (PVT) powder was dissolved in 8.8 g of the mixture. It is an abbreviation for P(VDF-TrFE). A 10.2wt% polyvinylidene fluoride-trifluoroethylene core spinning solution was prepared. Using coaxial electrospinning technology, the core and sheath layers were electrospun at an extrusion speed of 0.6mL / h under conditions of 20KV positive voltage and -2KV negative voltage. The spinning receiving distance was 25cm. The core-sheath heterogeneous nanofiber (PVT / Br-CA) piezoelectric film with a thickness of about 25μm was collected on the collecting roller.

[0028] Step 3: Preparation of stress-responsive solid electrolyte: Polyethylene oxide (PEO) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) are dissolved in anhydrous acetonitrile. The molar ratio of ethylene oxide units in PEO to lithium in LiTFSI is controlled at 10:1, and the mass fraction of PEO in the mixed solution is 12%. The mixed solution is cast onto a core-sheath heterostructured nanofiber (PVT / Br-CA) piezoelectric film and smoothed with a scraper. It is then dried in a vacuum drying oven at 70°C for 24 h. The resulting stress-responsive solid electrolyte, with a thickness of approximately 35 μm, is obtained. The solid electrolyte prepared by this process is named PVT / Br-CA / PEO / LiTFSI, i.e., stress-responsive solid electrolyte. The amount of PEO / LiTFSI solution is controlled so that the mass of the core-sheath heterostructured nanofiber (PVT / Br-CA) piezoelectric film accounts for approximately 60% of the total mass of the stress-responsive solid electrolyte after drying.

[0029] Step 4: Assemble the solid-state lithium battery: Using lithium iron phosphate as the positive electrode and lithium metal sheet as the negative electrode, place the stress-responsive solid electrolyte obtained in Step 3 between the positive and negative electrodes to assemble a stress-responsive solid electrolyte-based solid-state lithium battery. The process uses existing technology.

[0030] Example 3: A stress-responsive solid electrolyte-based solid-state lithium battery is prepared according to the following steps: Step 1: Preparation of bromoacetylated cellulose acetate: 10g of cellulose acetate (CA) was dried in a vacuum oven at 60℃ for 12h, then dissolved in 150mL of N,N-dimethylformamide (DMF). The solution was stirred until completely dissolved, and 11g of bromoacetyl bromide was added in an ice-water bath. The reaction was continued at 0℃ with stirring for 2h, followed by another 24h at room temperature with stirring. The resulting solution was poured into 1500ml of deionized water, resulting in the precipitation of a large amount of pale yellow solid. The pale yellow solid product was repeatedly washed with deionized water and filtered, then dried in an oven at 60℃ to obtain bromoacetylated cellulose acetate (Br-CA) powder. In this example, the XPS spectra of bromoacetylated cellulose acetate and the raw material cellulose acetate are compared as follows... Figure 1 As shown.

[0031] Step 2: Preparation of core-sheath heterogeneous nanofiber (PVT / Br-CA) piezoelectric film: Using a mixture of N,N-dimethylformamide (DMF) and acetone (AC) as solvent, with a mass ratio of N,N-dimethylformamide:acetone = 6:4, 1.2 g of bromoacetylated cellulose acetate (Br-CA) was dissolved in 8.8 g of the mixture to prepare a 12 wt% bromoacetylated cellulose acetate (Br-CA) sheath spinning solution; Using a mixture of N,N-dimethylformamide (DMF) and acetone (AC) as solvent, with a mass ratio of N,N-dimethylformamide:acetone = 8:2, 1 g of polyvinylidene fluoride-trifluoroethylene (PVT) powder was dissolved in 8.8 g of the mixture. P(VDF-TrFE) is an abbreviation for polyvinylidene fluoride-trifluoroethylene core spinning solution. Using coaxial electrospinning technology, the core and sheath layers were electrospun at an extrusion speed of 0.5 mL / h under conditions of 20 kV positive voltage and -2 kV negative voltage, with a spinning receiving distance of 20 cm. The resulting core-sheath heterogeneous nanofiber (PVT / Br-CA) piezoelectric film, approximately 20 μm thick, was collected on a collecting roller. In this embodiment, the SEM image of the core-sheath heterogeneous nanofiber piezoelectric film is shown below. Figure 2 As shown in (a), HRTEM images of a single core-sheath heterostructure nanofiber at different scales are as follows. Figure 2 As shown in (b) and (c).

[0032] Step 3: Preparation of stress-responsive solid electrolyte: Polyethylene oxide (PEO) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) are dissolved in anhydrous acetonitrile. The molar ratio of ethylene oxide units in PEO to lithium in LiTFSI is controlled at 12:1, and the mass fraction of PEO in the mixed solution is 12%. The mixed solution is cast onto a core-sheath heterostructured nanofiber (PVT / Br-CA) piezoelectric film and smoothed with a scraper. It is then dried in a vacuum drying oven at 60°C for 24 h. The resulting stress-responsive solid electrolyte, with a thickness of approximately 30 μm, is obtained. The solid electrolyte prepared by this process is named PVT / Br-CA / PEO / LiTFSI, i.e., stress-responsive solid electrolyte. The amount of PEO / LiTFSI solution is controlled so that the mass of the core-sheath heterostructured nanofiber (PVT / Br-CA) piezoelectric film accounts for approximately 40% of the total mass of the stress-responsive solid electrolyte after drying. In this embodiment, the butterfly-shaped amplitude curve and phase curve of the stress-responsive solid electrolyte are shown in the figure. Figure 3 As shown.

[0033] Step 4: Assemble the solid-state lithium battery: Using lithium iron phosphate as the positive electrode and lithium metal sheet as the negative electrode, place the stress-responsive solid electrolyte obtained in Step 3 between the positive and negative electrodes to assemble a stress-responsive solid electrolyte-based solid-state lithium battery. The process uses existing technology.

[0034] Example 4: A stress-responsive solid electrolyte-based solid-state lithium battery is prepared according to the following steps: Step 1: Preparation of bromoacetylated cellulose acetate: 10g of cellulose acetate (CA) was dried in a vacuum oven at 60℃ for 12h and then dissolved in 150mL of N,N-dimethylformamide (DMF). The solution was stirred until completely dissolved, and 11g of bromoacetyl bromide was added in an ice-water bath. The reaction was continued to be stirred at 0℃ for 2h, and then stirred at room temperature for 24h. The solution after the reaction was poured into 1500ml of deionized water, and a large amount of pale yellow solid precipitated. The pale yellow solid product was repeatedly washed with deionized water and filtered, and then dried in an oven at 60℃ to obtain bromoacetylated cellulose acetate (Br-CA) powder.

[0035] Step 2: Preparation of core-sheath heterogeneous nanofiber (PVT / Br-CA) piezoelectric film: Using a mixture of N,N-dimethylformamide (DMF) and acetone (AC) as solvent, with a mass ratio of N,N-dimethylformamide:acetone = 6:4, 1.2 g of bromoacetylated cellulose acetate (Br-CA) was dissolved in 8.8 g of the mixture to prepare a 12 wt% bromoacetylated cellulose acetate (Br-CA) sheath spinning solution; Using a mixture of N,N-dimethylformamide (DMF) and acetone (AC) as solvent, with a mass ratio of N,N-dimethylformamide:acetone = 8:2, 1 g of polyvinylidene fluoride-trifluoroethylene (PVT) powder was dissolved in 8.8 g of the mixture. It is an abbreviation for P(VDF-TrFE). A 10.2wt% polyvinylidene fluoride-trifluoroethylene core spinning solution was prepared. Using coaxial electrospinning technology, the core and sheath layers were electrospun at an extrusion speed of 0.5mL / h under positive voltage of 20KV and negative voltage of -2KV, respectively. The spinning receiving distance was 20cm. The core-sheath heterogeneous nanofiber (PVT / Br-CA) piezoelectric film with a thickness of about 23μm was collected on the collecting roller.

[0036] Step 3: Preparation of stress-responsive solid electrolyte: Polyethylene oxide (PEO) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) are dissolved in anhydrous acetonitrile. The molar ratio of ethylene oxide units in PEO to lithium in LiTFSI is controlled at 14:1, and the mass fraction of PEO in the mixed solution is 12%. The mixed solution is cast onto a core-sheath heterostructure nanofiber (PVT / Br-CA) piezoelectric film and smoothed with a scraper. It is then dried in a vacuum drying oven at 60°C for 24 h. The resulting stress-responsive solid electrolyte, with a thickness of approximately 30 μm, is obtained. The solid electrolyte prepared by this process is named PVT / Br-CA / PEO / LiTFSI, i.e., stress-responsive solid electrolyte. The amount of PEO / LiTFSI solution is controlled so that the mass of the core-sheath heterostructure nanofiber (PVT / Br-CA) piezoelectric film accounts for approximately 50% of the total mass of the stress-responsive solid electrolyte after drying.

[0037] Step 4: Assemble the solid-state lithium battery: Using lithium iron phosphate as the positive electrode and lithium metal sheet as the negative electrode, place the stress-responsive solid electrolyte obtained in Step 3 between the positive and negative electrodes to assemble a stress-responsive solid electrolyte-based solid-state lithium battery. The process uses existing technology.

[0038] Comparative Example 1: A stress-responsive solid electrolyte-based solid-state lithium battery was prepared according to the following steps: Step 1: Preparation of PVT nanofiber membrane: A 10 wt% PVT core layer spinning solution was prepared using a mixed solution of DMF and AC as the solvent. Specifically, 1 g of PVT powder was dissolved in 9 g of a mixed solution of DMF and AC, with a mass ratio of DMF to AC of 8:2. Electrospinning was performed at a speed of 0.4 mL / h under conditions of 25 KV positive voltage and -2 KV negative voltage. The PVT nanofiber membrane with a thickness of approximately 20 μm was collected on a collecting roller.

[0039] Step 2: Preparation of PVT nanofiber membrane composite solid electrolyte: PEO and LiTFSI were dissolved in anhydrous acetonitrile at a certain mass ratio to prepare a PEO / LiTFSI mixed solution. The molar ratio of [EO] in PEO to [Li] in LiTFSI was 12:1, and the mass fraction of PEO in the mixed solution was 12%. The mixed solution was poured onto a PVT nanofiber membrane and leveled with a scraper. It was then dried in a vacuum drying oven at 60℃ for 24 hours. The resulting PVT nanofiber membrane composite solid electrolyte, with a thickness of approximately 30 μm, was obtained. This solid electrolyte was named PVT / PEO / LiTFSI. The amount of PEO / LiTFSI solution was controlled so that the mass of the PVT nanofiber membrane accounted for approximately 40% of the total mass of the composite solid electrolyte after drying.

[0040] The remaining preparation steps and parameters are the same as in Example 3.

[0041] Comparative Example 2: A stress-responsive solid electrolyte-based solid-state lithium battery was prepared according to the following steps: Step 1: Preparation of Br-CA nanofiber membrane: A 12wt% Br-CA sheath spinning solution was prepared using a mixed solution of DMF and AC as the solvent. Specifically, 1.2g of Br-CA powder was dissolved in 8.8g of a mixed solution of DMF and AC, with a mass ratio of DMF to AC of 6:4. Electrospinning was performed at a speed of 0.4mL / h under conditions of 25KV positive voltage and -2KV negative voltage. The Br-CA nanofiber membrane with a thickness of approximately 20μm was collected on a collecting roller.

[0042] Step 2: Preparation of Br-CA nanofiber membrane composite solid electrolyte: PEO and LiTFSI were dissolved in anhydrous acetonitrile at a certain mass ratio to prepare a PEO / LiTFSI mixed solution. The molar ratio of [EO] in PEO to [Li] in LiTFSI was 12:1, and the mass fraction of PEO in the mixed solution was 12%. The mixed solution was poured onto a Br-CA nanofiber membrane and leveled with a scraper. It was then dried in a vacuum drying oven at 60℃ for 24 hours. The membrane was then peeled off to obtain the Br-CA nanofiber membrane composite solid electrolyte with a thickness of approximately 30 μm. The solid electrolyte prepared by this process was named Br-CA / PEO / LiTFSI. The amount of PEO / LiTFSI solution was controlled so that the mass of the Br-CA nanofiber membrane accounted for approximately 40% of the total mass of the composite solid electrolyte after drying.

[0043] The remaining steps and parameters are the same as in Example 3, and a solid-state lithium battery is obtained.

[0044] Comparative Example 3: A stress-responsive solid electrolyte-based solid-state lithium battery was prepared according to the following steps: A PEO / LiTFSI mixed solution was prepared by dissolving PEO and LiTFSI in anhydrous acetonitrile at a certain mass ratio. The molar ratio of [EO] in PEO to [Li] in LiTFSI was 12:1, and the mass fraction of PEO in the mixed solution was 12%. The mixed solution was cast into a polytetrafluoroethylene plate and then dried in a vacuum drying oven at 60°C for 24 h. The plate was then peeled off to obtain the PEO solid electrolyte with a thickness of approximately 30 μm. The solid electrolyte prepared by this process was named PEO / LiTFSI. The remaining steps and parameters were the same as in Example 3 to prepare a solid-state lithium battery.

[0045] Figure 1 The XPS spectra of bromoacetylated cellulose acetate (Br-CA) and the raw material cellulose acetate (CA) in Example 3 are compared. It can be seen that their XPS spectra are basically identical, with characteristic peaks at binding energies of 533.08 eV and 287.08 eV, indicating that after bromination modification, bromoacetylated cellulose acetate retains its original basic chemical structure. However, unlike the raw material cellulose acetate, the spectrum of bromoacetylated cellulose acetate shows three new characteristic peaks at 71.08 eV, 184.08 eV, and 258.08 eV. Figure 1 The Br 3d, Br 3p, and Br 3s groups in the figure provide strong evidence that Br-CH2 can be grafted onto CA via acylation to yield Br-CA. Figure 1 Br 3d, Br 3p, and Br 3s are characteristic peaks of Br-CH2 formation.

[0046] Figure 2 Images of the core-sheath heterostructure nanofibers in Example 3 are shown, where (a) is a SEM image of the piezoelectric film of the core-sheath heterostructure nanofiber (PVT / Br-CA); (b) and (c) are HRTEM images (high-resolution transmission electron microscopy images) of a single core-sheath heterostructure nanofiber (PVT / Br-CA) at different scales. Figure 2 As can be seen in (a), the PVT / Br-CA nanofibers have good morphology and uniform thickness, and the fiber membrane exhibits a disordered porous structure; from Figure 2 As can be seen from (b), the prepared core-sheath heterostructure nanofibers have a distinct core-sheath structure; from Figure 2 (b) further reveals a distinct heterogeneous interface between the PVT core and the Br-CA sheath.

[0047] This demonstrates that a heterogeneous nanofiber piezoelectric membrane with PVT as the core and Br-CA as the nanosheath was successfully prepared by coaxial electrospinning technology.

[0048] Figure 3 The figures show the butterfly-shaped amplitude and phase curves of the stress-responsive solid electrolyte (PVT / Br-CA / PEO / LiTFSI) in Example 3. As can be seen from the figures, the piezoelectric displacement curve of the stress-responsive solid electrolyte exhibits a typical butterfly shape as the applied DC bias is scanned from negative to positive. Near the coercive voltage, the displacement reverses sharply, and the distribution is basically symmetrical under both positive and negative biases. The corresponding phase curve shows a sudden change of approximately 180° at the coercive field. This confirms that the stress-responsive solid electrolyte has a good piezoelectric effect and can respond to the stress generated by dendrite growth.

[0049] Figure 4 The figure shows a comparison of the ionic conductivity of the electrolytes in Example 3 and Comparative Examples 1-3. The figure shows the ionic conductivity test results of four electrolytes under different temperature conditions: PVT / PEO / LiTFSI electrolyte of Comparative Example 1, Br-CA / PEO / LiTFSI electrolyte of Comparative Example 2, PEO / LiTFSI electrolyte of Comparative Example 3, and PVT / Br-CA / PEO / LiTFSI electrolyte of Example 3.

[0050] from Figure 4As can be seen, the ionic conductivity of the PVT / Br-CA / PEO / LiTFSI electrolyte and the electrolytes of Comparative Examples 1 and 2 is significantly higher than that of the pure PEO electrolyte of Comparative Example 3 across all temperature ranges from 30°C to 70°C. Furthermore, the electrolyte of Example 3, modified with a core-sheath heterostructure nanofiber (PVT / Br-CA) piezoelectric film, exhibits the best ionic conductivity compared to the electrolytes of Comparative Examples 1 and 2. This indicates that the Br-CA nanosheath layer of the core-sheath heterostructure nanofiber (PVT / Br-CA) has a significant effect on promoting ion transport through multi-coordination synergy of PEO ether oxygen bonds at the fiber-matrix interface, thereby effectively improving the ionic conductivity of the solid electrolyte.

[0051] Figure 5 The figure shows the Li⁺ plating / stripping cycle diagram (50°C) of a Li / Li symmetric battery using the stress-responsive solid electrolyte (PVT / Br-CA / PEO / LiTFSI) of Example 3. As can be seen from the figure, at a charge / discharge capacity of 0.1 mA / cm², the battery maintained a stable voltage for 20 hours under sequentially increasing current densities of 0.1 mA / cm², 0.2 mA / cm², 0.3 mA / cm², 0.4 mA / cm², and 0.5 mA / cm². Furthermore, when the current density was reduced back to 0.2 mA / cm², the voltage remained stable and continued to cycle for 650 hours. This indicates that the stress-responsive solid electrolyte has a significant effect on regulating uniform ion deposition to suppress lithium dendrite growth, and can significantly improve the battery's cycle stability.

[0052] Figure 6 The graph shows the cycling performance of the stress-responsive solid electrolyte-based (PVT / Br-CA / PEO / LiTFSI) solid-state lithium battery (LiFePO4 / Li) in Example 3 at 50°C and 1C rate. As can be seen from the graph, the solid-state lithium battery assembled with this stress-responsive solid electrolyte still maintains a discharge specific capacity of 119.4 mAh / g after 620 stable cycles at 1C rate, and the coulombic efficiency remains above 99.9%. This indicates that the unique core-sheath structure of the PVT / Br-CA nanofibers within the stress-responsive solid electrolyte enables "rapid transport and uniform deposition" of Li+ within the battery. The assembled solid-state lithium battery exhibits high coulombic efficiency, long cycle life, and high safety.

Claims

1. A stress-responsive solid electrolyte-based solid-state lithium battery, characterized in that: The invention includes a positive electrode made of lithium iron phosphate, a negative electrode made of lithium metal sheet, and a stress-responsive solid electrolyte disposed between the positive and negative electrodes; the stress-responsive solid electrolyte comprises a core-sheath heterogeneous nanofiber piezoelectric membrane, polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide; the core-sheath heterogeneous nanofiber piezoelectric membrane has polyvinylidene fluoride-trifluoroethylene as the core layer and bromoacetylated cellulose acetate as the sheath layer.

2. The stress-responsive solid-state electrolyte-based solid-state lithium battery according to claim 1, characterized in that: The core-sheath heterogeneous nanofiber piezoelectric membrane accounts for 30%-60% of the mass of the stress-responsive solid electrolyte.

3. The stress-responsive solid electrolyte-based solid-state lithium battery according to claim 1, characterized in that: The molar ratio of ethylene oxide structural units in the polyethylene oxide to lithium in the lithium bis(trifluoromethanesulfonylimide) is 8-18.

4. The stress-responsive solid electrolyte-based solid-state lithium battery according to claim 1, characterized in that: The core-sheath heterogeneous nanofiber piezoelectric film has a thickness of 15-25 μm, and the stress-responsive solid electrolyte has a thickness of 25-35 μm.

5. A method for preparing a stress-responsive solid electrolyte-based solid-state lithium battery, characterized in that: Includes the following steps: Step 1: Preparation of bromoacetylated cellulose acetate powder: Dissolve cellulose acetate in N,N-dimethylformamide, add bromoacetyl bromide in an ice-water bath and react, then precipitate, wash and dry to obtain bromoacetylated cellulose acetate powder; Step 2: Preparation of core-sheath heterogeneous nanofiber piezoelectric membrane: Using a mixture of N,N-dimethylformamide and acetone as solvent, polyvinylidene fluoride-trifluoroethylene core spinning solution and bromoacetylated cellulose acetate sheath spinning solution were prepared respectively. Core-sheath heterogeneous nanofiber piezoelectric membrane, i.e., core-sheath heterogeneous nanofiber piezoelectric membrane, was obtained by coaxial electrospinning. Step 3: Preparation of stress-responsive solid electrolyte: Polyethylene oxide and lithium bis(trifluoromethanesulfonylimide) are dissolved in acetonitrile to prepare a mixed solution, which is then filled into a core-sheath heterostructure nanofiber piezoelectric membrane by solution casting and vacuum drying to obtain a stress-responsive solid electrolyte; Step 4: Assemble the solid-state lithium battery: Using lithium iron phosphate as the positive electrode and lithium metal sheet as the negative electrode, place the stress-responsive solid electrolyte obtained in Step 3 between the positive and negative electrodes to assemble a stress-responsive solid electrolyte-based solid-state lithium battery.

6. The preparation method according to claim 5, characterized in that: In step one, 10g of cellulose acetate was dissolved in 150mL of N,N-dimethylformamide, and 11g of bromoacetyl bromide was added. The reaction was carried out at 0℃ for 2h and at room temperature for 24h. The product was washed with deionized water and dried at 60℃ to obtain bromoacetylated cellulose acetate powder.

7. The preparation method according to claim 5, characterized in that: In step two, the core spinning solution concentration is 8-15 wt%, and the sheath spinning solution concentration is 10-20 wt%; the coaxial electrospinning voltage is 15-25 kV, the receiving distance is 15-25 cm, and the solution extrusion speed is 0.2-0.6 mL / h.

8. The preparation method according to claim 5, characterized in that: In step three, the molar ratio of ethylene oxide units to lithium is 8-18, the vacuum drying temperature is 50-70℃, and the core-sheath heterogeneous nanofiber piezoelectric film accounts for 30%-60% of the total mass of the solid electrolyte.

9. The preparation method according to claim 5, characterized in that: In step two, the mass ratio of N,N-dimethylformamide to acetone used in the core spinning solution is 8:2, and the mass ratio of N,N-dimethylformamide to acetone used in the sheath spinning solution is 6:4.

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