Preparation method of constant-temperature self-repairing flexible supercapacitor

Abstract

The invention discloses a preparation method of a constant-temperature self-repairing flexible supercapacitor. The preparation method comprises the following steps: reducing graphene oxide (LTR-rGO) at a low temperature to retain gt; 15% of oxygen functional groups are used for improving dispersity and pseudocapacitance; alkane-coated Ag core-shell nanoparticles are prepared through a reversed-phase dropwise adding emulsification method, and constant-temperature regulation and control at the temperature of 25-45 DEG C are achieved; the lignin-based self-healing gel polymer electrolyte is crosslinked through hydrogen bonds and ions, and is loaded with Fh-BN and core-shell particles to improve the ionic conductivity to gt; 50 mS / cm; the electrode slurry contains 70wt%-85wt% of LTR-rGO, an interface is optimized through acid heat treatment, and a sandwich structure is assembled through reverse evaporation. The device is green and environment-friendly, high in flexibility (bending gt, capacity retention gt after 1000 times, 90%) and self-healing efficiency gt; the buffer temperature difference is 5-10 DEG C, stable operation is carried out at the temperature of-20-60 DEG C, and the specific capacity is gt; 400 F / g and the energy density gt; the service life is 50Wh / kg, and the service life is gt; the method is suitable for various wearable electronic devices.

Description

Technical Field

[0001] This invention relates to a method for preparing a temperature-controlled, self-healing flexible supercapacitor, specifically a composite method based on silver phase change core-shell nanoparticles, low-temperature reduced graphene oxide, and lignin-based self-healing gel polymer electrolyte, for realizing energy storage and thermal management of flexible, wearable electronic devices. Background Technology

[0002] Supercapacitors are highly efficient energy storage devices with advantages such as high power density, fast charging and discharging, and long cycle life, and are widely used in wearable electronics, electric vehicles, and smart devices. However, traditional supercapacitors often face problems such as low energy density, high temperature sensitivity, insufficient mechanical flexibility, and inability to self-repair after damage. These limitations restrict their application in extreme environments (such as high temperature, low temperature, or mechanical deformation), especially in wearable devices, where temperature fluctuations can lead to performance degradation, and mechanical damage (such as bending or stretching) can easily cause cracks and capacity loss.

[0003] Currently, researchers are improving supercapacitors by introducing phase change materials (PCMs) for thermal regulation, employing polymer networks for self-healing, and utilizing carbon nanomaterials to enhance conductivity. For example, some works use paraffin microcapsules to enhance thermal stability or polyvinyl alcohol (PVA)-based hydrogels to provide flexibility, but these methods often lack multifunctional integration, such as simultaneously achieving isothermal control, self-healing, and high capacity. Furthermore, the introduction of biomass materials such as lignin can improve environmental friendliness, but compatibility with phase change core-shell particles still needs optimization. Although rGO-based electrodes have been reported in existing technologies, high-temperature reduction often leads to the loss of functional groups, affecting dispersibility and interfacial integration.

[0004] This invention aims to address the aforementioned problems by developing a multifunctional supercapacitor through pretreatment of low-temperature reduced graphene oxide (LTR-rGO), synthesis of silver phase-change core-shell nanoparticles, preparation of lignin-based self-healing GPE, and reverse evaporation assembly technology. This method emphasizes green preparation, low-temperature processes, and material compatibility, providing a new approach for wearable energy storage. Summary of the Invention

[0005] The purpose of this invention is to overcome the temperature sensitivity and mechanical fragility of traditional supercapacitors and to provide a highly efficient composite method based on silver phase change core-shell nanoparticles, LTR-rGO and lignin-based self-healing GPE, so as to achieve isothermal regulation, self-repair and high capacitance.

[0006] This invention provides a method for preparing a temperature-controlled, self-healing flexible supercapacitor, comprising the following steps: Step 1, Low-temperature reduction of graphene oxide pretreatment stage: Graphene oxide powder was dispersed in deionized water to form a suspension with a concentration of 5 mg / mL to 15 mg / mL. A mild reducing agent (such as vitamin C, molar ratio of GO:reducing agent = 1:3 to 1:6) was added, and reduction was carried out by stirring at room temperature (25°C to 50°C) for 24 h to 48 h, or by low-temperature hydrothermal treatment (80°C, in a sealed reactor for 2 h to 4 h). After centrifugation and washing (8000 rpm, 10 min, 3 to 5 times with water / ethanol), vacuum drying (40°C) was performed to obtain low-temperature reduced graphene oxide (LTR-rGO), in which the degree of reduction was controlled at 60% to 80% and the C / O ratio was 4 to 6, so as to retain oxygen functional groups to enhance dispersibility and integration with biomass materials. Step 2, Preparation of silver phase transition core-shell nanoparticles: At room temperature, the core material alkane (selected from octadecane, nonadecane, eicosane, docosane, or docosahexadecane) is dissolved in a volatile solvent (such as dichloromethane DCM, mass ratio 1:8~1:12), and magnetically stirred for 20 min~40 min until completely dissolved to form an oil phase. To prepare the aqueous phase: a surfactant (such as CTAB, concentration 0.1 g / 40 mL~0.3 g / 40 mL) is added to deionized water and stirred until homogeneous. The aqueous phase is slowly added dropwise to the oil phase (dropping rate 0.5 mL / min~2 mL / min) while simultaneously undergoing high-power ultrasonic dispersion (power 200 W~400 W, 10 min~20 min) to initially form a W / O emulsion. After the dropwise addition is complete, ultrasonication continues for 3 min~7 min, followed by the addition of additional deionized water (containing PVP stabilizer, 0.03 g / 20 mL~0.07 g / 20 mL), and the stirring speed is increased (400 rpm~1200 rpm). The solvent was induced to transform into an O / W emulsion by stirring at 40°C to 60°C for 3 to 7 hours to evaporate the solvent and form a solid alkane nanocore suspension. Silver nitrate (AgNO3, mass ratio 0.3 g / 1 g to 0.7 g / 1 g core material) was added to the suspension and stirred to dissolve. A reducing agent (such as sodium citrate solution, 1 g / 10 mL to 2 g / 10 mL water) was slowly added dropwise and stirred at room temperature for 1 to 5 hours to deposit the silver shell. The mixture was centrifuged (6000 rpm to 10000 rpm, 8 min to 12 min), washed 3 to 5 times with ethanol and water, and dried to obtain alkane@Ag core-shell nanoparticles with a size controlled between 50 nm and 250 nm. Step 3, Preparation of self-healing gel polymer electrolyte (GPE) and electrode slurry: Preparation of self-healing gel polymer electrolyte (GPE): Alkali lignin (1 g–2 g) was dissolved in deionized water (20 mL–40 mL), and NaOH was added to adjust the pH to 8–10. The solution was heated and stirred at 60°C–80°C for 0.5 h–2 h until completely dissolved, forming a lignin solution. An ionic crosslinking agent (such as CaCl2 or FeCl3, 0.1 g–0.5 g) was added, and the solution was stirred for 20 min–40 min to form a dynamic ionic complex network. H2SO4 (2 g–4 g) was added as an electrolyte salt to provide ionic conductivity. Fh-BN solution (0.5 mL–1.5 mL, concentration 2 mg / mL–4 mg / mL) and alkane@Ag core-shell nanoparticles (loaded 3 wt%–12 wt%) were added, and the solution was ultrasonically dispersed for 10 min–20 min (power 100 W–200 W) to ensure uniform particle distribution and fusion with lignin through hydrogen bonds. The solution was stirred for another 0.5 h–1.5 h. h until homogeneous; cool to room temperature to cure, forming lignin-based self-healing GPE, in which hydrogen bonding and ionic crosslinking synergistically achieve self-healing efficiency >80%, and Fh-BN enhances ion transport (conductivity >50 mS / cm) and alkane@Ag particles provide isothermal regulation (phase change enthalpy >100 J / g). Electrode slurry preparation: Mix 70 wt% ~ 85 wt% LTR-rGO, 8 wt% ~ 10 wt% PVDF binder, 0.5 wt% ~ 2 wt% Fh-BN and 3 wt% ~ 12 wt% alkane@Ag core-shell nanoparticles; ultrasonically disperse in NMP solvent for 1 h ~ 3 h (power 150 W ~ 250 W), stir until a uniform paste is formed, and degas for 20 min ~ 40 min; coat with a scraper onto calcined carbon cloth current collector (load 0.5 mg / cm² ~ 1.5 mg / cm²), and dry at 170°C ~ 190°C overnight; perform acid heat treatment (soak in H2SO4:HNO3 = 3:1 for 3 h ~ 5 h, wash, dry, and then heat at 170°C ~ 190°C overnight); Step 4, Assembly of the temperature-controlled self-healing flexible supercapacitor: Using reverse evaporation technology: A vacuum is applied to the bottom of the electrode, and GPE is uniformly filled into the electrode and maintained under vacuum for 10 h to 14 h for curing; the filled electrode and Fh-BN-based separator are stacked into a "sandwich" structure (active area 0.5 cm² to 2 cm²) and sealed with Kapton tape; the overall thickness is compressed to 0.5 cm to 1.5 cm and cut into rectangles (2 cm to 4 cm × 0.5 cm to 2 cm); an LTR-rGO film is sprayed onto the electrode surface as a current collector; the resulting supercapacitor has flexibility (>1000 bending cycles, capacity retention >90%), self-healing (efficiency >85%, time <10 min) and isothermal properties (phase change buffer temperature fluctuation 5°C to 10°C, suitable for 20°C to 60°C).

[0007] In step 1, the low-temperature reduction temperature is 25°C to 80°C, and the reducing agent is selected from vitamin C or tea polyphenols, retaining an oxygen functional group content of >15% to improve dispersibility and pseudocapacitive contribution.

[0008] In step 2, the core material alkane is selected from octadecane, nonadecane, eicosane, docosane, or docosane to achieve different phase transition temperatures (25°C~45°C); the volatile solvent is selected from dichloromethane or ethyl acetate; the reverse-phase dropping rate is 0.5~2 mL / min; and sodium citrate is used as a reducing agent for silver shell deposition.

[0009] In step 3, the lignin is alkali lignin or sulfonated lignin, the ionic crosslinking agent is selected from CaCl2 or FeCl3, the alkane@Ag core-shell nanoparticle loading is 3 wt%~12 wt%, the Fh-BN concentration is 2 mg / mL~4 mg / mL, and the H2SO4 concentration in the GPE preparation is 2 g / 30 mL~4 g / 30 mL, providing an ionic conductivity >50 mS / cm.

[0010] In step 3, the LTR-rGO ratio of the electrode slurry is 70 wt%~85 wt%, the ultrasonic dispersion power is 150 W~250 W, and the acid heat treatment uses an H2SO4:HNO3 volume ratio of 3:1.

[0011] In step 4, the reverse evaporation vacuum maintenance time is 10 h to 14 h, the supercapacitor structure is a "sandwich" stack, suitable for wearable devices, with a specific capacitance >400 F / g and a cycle life >40,000 times.

[0012] The beneficial effects of this invention are as follows: (1) By introducing silver phase change core-shell nanoparticles, not only isothermal control (phase change heat absorption buffers temperature fluctuations) is achieved, but the silver shell also enhances conductivity and thermal diffusion. (2) The hydrogen bonding and ionic crosslinking of lignin-based GPE provide an efficient self-healing mechanism, which improves mechanical durability and flexibility; (3) The low-temperature reduction of LTR-rGO retains functional groups, which improves dispersibility, pseudocapacitive contribution and interfacial integration with biomass materials; (4) The overall method is green and environmentally friendly, uses biomass materials, is suitable for wearable devices, and has high capacity, long life and wide temperature range operation.

[0013] The preparation method proposed in this invention provides a new approach for multifunctional flexible supercapacitors. Test data shows that the specific capacitance reaches over 450 F / g, the energy density is >50 Wh / kg, and the capacity recovery after self-healing is >90%, making it suitable for smart wearables and energy storage. Attached Figure Description

[0014] Figure 1 This is a schematic diagram illustrating the fabrication process of the isothermal self-healing flexible supercapacitor of the present invention. Figure 2 Scanning electron microscope image of silver phase transition core-shell nanoparticles; Figure 3 Scanning electron microscope image of hydrogel electrolyte; Figure 4 Cyclic volt-ampere curves and constant current charge-discharge curves of supercapacitors under different load ratios; Figure 5 Electrochemical performance curves under bending, tensile, and torsional conditions; Figure 6 Optical photographs of the self-healing process; Figure 7 An optical photograph of a supercapacitor in a flexible state. Detailed Implementation Example 1

[0015] Step 1, Low-temperature reduction of graphene oxide pretreatment stage: Graphene oxide powder was dispersed in deionized water to form a suspension with a concentration of 5 mg / mL; vitamin C was added (molar ratio of GO:reducing agent = 1:3), and the mixture was stirred at room temperature (25°C) for 24 h for reduction; the mixture was centrifuged and washed (8000 rpm, 10 min, 3 times with water / ethanol), and vacuum dried (40°C) to obtain LTR-rGO with a reduction degree of 60% and a C / O ratio of 4. Step 2, Preparation of silver phase transition core-shell nanoparticles: At room temperature, octadecane was dissolved in DCM (mass ratio 1:8) and magnetically stirred for 20 min to form an oil phase. An aqueous phase was prepared by adding CTAB (0.1 g / 40 mL) to deionized water. The aqueous phase was then added dropwise to the oil phase (0.5 mL / min) and ultrasonically dispersed (200 W, 10 min) to form a W / O emulsion. Ultrasonication was continued for 3 min, and additional water (containing PVP 0.03 g / 20 mL) was added. The mixture was stirred at 400 rpm to convert the phase to an O / W emulsion. The DCM was evaporated by heating at 40°C and stirring for 3 h. AgNO3 (0.3 g / 1 g core material) was added. Sodium citrate solution (1 g / 10 mL) was added dropwise, and the mixture was stirred for 1 h to deposit a silver shell. The mixture was centrifuged (6000 rpm, 8 min), washed, and dried to obtain octadecane@Ag particles with a size of approximately 50 nm. Step 3, Preparation of self-healing gel polymer electrolyte (GPE) and electrode slurry: Preparation of GPE: Alkali lignin (1 g) was dissolved in deionized water (20 mL), and the pH was adjusted to 8 by adding NaOH. The mixture was stirred at 60°C for 0.5 h. CaCl2 (0.1 g) was added and stirred for 20 min. H2SO4 (2 g) was added. Fh-BN solution (0.5 mL, 2 mg / mL) and octadecane@Ag particles (3 wt%) were added and ultrasonically dispersed for 10 min (100 W). The mixture was stirred for 0.5 h and then cooled to solidify. Electrode slurry preparation: Mix 70 wt% LTR-rGO, 8 wt% PVDF, 0.5 wt% Fh-BN and 3 wt% octadecane@Ag; ultrasonically disperse in NMP for 1 h (150 W), stir into a paste, degas for 20 min; coat onto carbon cloth (load 0.5 mg / cm²), dry at 170°C; acid heat treatment (soak in H2SO4:HNO3=3:1 for 3 h, wash, heat at 170°C). Step 4, Assembly of the temperature-controlled self-healing flexible supercapacitor: Using reverse evaporation: vacuum fill the bottom of the electrode with GPE and maintain curing for 10 h; stack it into a "sandwich" structure (active area 0.5 cm²) and seal it; compress the thickness to 0.5 cm and cut it into rectangles (2 cm × 0.5 cm); spray an LTR-rGO film as a current collector. Example 2

[0016] Step 1, Low-temperature reduction of graphene oxide pretreatment stage: Graphene oxide powder was dispersed in deionized water to form a suspension with a concentration of 10 mg / mL; vitamin C was added (molar ratio of GO:reducing agent = 1:4), and the mixture was stirred at room temperature (30°C) for 36 h for reduction; the mixture was centrifuged and washed (8000 rpm, 10 min, 4 times with water / ethanol), and vacuum dried (40°C) to obtain LTR-rGO with a reduction degree of 70% and a C / O ratio of 5, in order to retain more oxygen functional groups to enhance dispersibility in subsequent slurries and hydrogen bonding with lignin; Step 2, Preparation of silver phase transition core-shell nanoparticles: At room temperature, nonadecane was dissolved in DCM (mass ratio 1:10) and magnetically stirred for 30 min to form a clear oil phase. An aqueous phase was prepared by adding CTAB (0.2 g / 40 mL) to deionized water and stirring until homogeneous. The aqueous phase was slowly added dropwise to the oil phase (1 mL / min) while simultaneously undergoing high-power ultrasonic dispersion (300 W, 15 min), initially forming a W / O emulsion. After the addition was complete, ultrasonication continued for 5 min, followed by the addition of additional deionized water (containing 0.05 g / 20 mL of PVP stabilizer) and increasing the stirring speed (800 rpm) to induce the phase to transform into an O / W emulsion. The mixture was gently heated to 50°C and stirred for 4 h to volatilize the DCM, forming a solid nonadecane nanocore suspension. Silver nitrate (AgNO3, mass ratio 0.5 g / 1 g core material) was added to the suspension and stirred until dissolved. Sodium citrate solution (1.5 g / 10 mL water) was slowly added dropwise, and the mixture was stirred at room temperature for 3 h to deposit a silver shell. The mixture was then centrifuged (8000 rpm, 10 min). The nanoparticles were washed four times with ethanol and water and dried to obtain nonadecane@Ag core-shell nanoparticles with a size of 150 nm. Step 3, Preparation of self-healing gel polymer electrolyte (GPE) and electrode slurry: Preparation of self-healing gel polymer electrolyte (GPE): Alkali lignin (1.5 g) was dissolved in deionized water (30 mL), and NaOH was added to adjust the pH to 9. The solution was heated and stirred at 70°C for 1 h until completely dissolved, forming a lignin solution. An ionic crosslinking agent, FeCl3 (0.3 g), was added and stirred for 30 min to form a dynamic ionic complex network. H2SO4 (3 g) was added as an electrolyte salt to provide ionic conductivity. Fh-BN solution (1 mL, concentration 3 mg / mL) and nonadecane@Ag core-shell nanoparticles (6 wt%) were added and ultrasonically dispersed for 15 min (150 W) to ensure uniform particle distribution and fusion with lignin through hydrogen bonds. Stirring was continued for 1 h until homogeneous. The mixture was cooled to room temperature and cured to form a lignin-based self-healing GPE. The self-healing efficiency was >85% achieved synergistically through hydrogen bonds and ionic crosslinking, and isothermal regulation (phase transition enthalpy >120 J / g) was provided by Fh-BN enhancing ion transport (conductivity >55 mS / cm) and nonadecane@Ag particles. Electrode slurry preparation: 75 wt% LTR-rGO, 9 wt% PVDF binder, 1 wt% Fh-BN and 6 wt% nonadecane@Ag core-shell nanoparticles were mixed; the mixture was ultrasonically dispersed in NMP solvent for 2 h (power 200 W), stirred until a uniform paste was formed, and degassed for 30 min; the paste was then coated onto calcined carbon cloth current collector with a scraper (load 1 mg / cm²), dried at 180°C overnight; and subjected to acid heat treatment (soaking in H2SO4:HNO3=3:1 for 4 h, washing, drying, and then heating at 180°C overnight). Step 4, Assembly of the temperature-controlled self-healing flexible supercapacitor: Using reverse evaporation technology: A vacuum is applied to the bottom of the electrode, and GPE is uniformly filled into the electrode and maintained under vacuum for 12 h for curing; the filled electrode and Fh-BN-based separator are stacked into a "sandwich" structure (active area 1 cm²) and sealed with Kapton tape; the overall thickness is compressed to 1 cm and cut into rectangles (3 cm × 1 cm); an LTR-rGO film is sprayed onto the electrode surface as a current collector; the resulting supercapacitor has flexibility (>1200 bending cycles, capacity retention >92%), self-healing (efficiency >88%, time <8 min) and isothermal properties (phase change buffer temperature fluctuation 6°C~8°C, suitable for -15°C~55°C). Example 3

[0017] Step 1, Low-temperature reduction of graphene oxide pretreatment stage: Graphene oxide powder was dispersed in deionized water to form a suspension with a concentration of 15 mg / mL; tea polyphenols were added (molar ratio of GO:reducing agent = 1:5), and reduction was carried out under low-temperature hydrothermal conditions (80°C, in a sealed reactor for 2 h); centrifugation and washing (8000 rpm, 10 min, 5 times with water / ethanol), and vacuum drying (40°C) were performed to obtain LTR-rGO with a reduction degree of 75% and a C / O ratio of 5.5, in order to retain oxygen functional groups >18% to improve pseudocapacitive contribution and biomass compatibility; Step 2, Preparation of silver phase transition core-shell nanoparticles: At room temperature, eicosane was dissolved in ethyl acetate (mass ratio 1:12) and magnetically stirred for 35 min to form a clear oil phase. An aqueous phase was prepared by adding CTAB (0.25 g / 40 mL) to deionized water and stirring until homogeneous. The aqueous phase was slowly added dropwise to the oil phase (1.5 mL / min) while simultaneously undergoing high-power ultrasonic dispersion (350 W, 18 min) to initially form a W / O emulsion. After the addition was complete, ultrasonication continued for 6 min, followed by the addition of additional deionized water (containing 0.06 g / 20 mL of PVP stabilizer) and increasing the stirring speed (1000 rpm) to induce the phase to transform into an O / W emulsion. The mixture was gently heated to 55°C and stirred for 5 h to evaporate the ethyl acetate, forming a solid eicosane nanocore suspension. Silver nitrate (AgNO3, mass ratio 0.6 g / 1 g core material) was added to the suspension and stirred until dissolved. Sodium citrate solution (1.8 g / 10 mL water) was slowly added dropwise, and the mixture was stirred at room temperature for 4 h to deposit a silver shell. The mixture was then centrifuged (9000 rpm). Washed five times with ethanol and water at rpm (11 min), and dried to obtain eicosane@Ag core-shell nanoparticles with a size of 200 nm. Step 3, Preparation of self-healing gel polymer electrolyte (GPE) and electrode slurry: Preparation of self-healing gel polymer electrolyte (GPE): Sulfonated lignin (2 g) was dissolved in deionized water (40 mL), and NaOH was added to adjust the pH to 10. The solution was heated and stirred at 80°C for 1.5 h until completely dissolved, forming a lignin solution. An ionic crosslinking agent, CaCl2 (0.4 g), was added and stirred for 35 min to form a dynamic ionic complex network. H2SO4 (3.5 g) was added as an electrolyte salt to provide ionic conductivity. Fh-BN solution (1.2 mL, concentration 3.5 mg / mL) and eicosane@Ag core-shell nanoparticles (loaded 9 wt%) were added and ultrasonically dispersed for 18 min (power 180 W) to ensure uniform particle distribution and fusion with lignin through hydrogen bonds. Stirring was continued for 1.2 h until homogeneous. The mixture was cooled to room temperature and cured to form a lignin-based self-healing GPE. The self-healing efficiency was >90% achieved synergistically through hydrogen bonding and ionic crosslinking. Fh-BN enhanced ion transport (conductivity >60 mS / cm) and eicosane@Ag particles provided isothermal regulation (phase transition enthalpy >140°C). J / g); Electrode slurry preparation: 80 wt% LTR-rGO, 9.5 wt% PVDF binder, 1.5 wt% Fh-BN and 9 wt% eicosane@Ag core-shell nanoparticles were mixed; the mixture was ultrasonically dispersed in NMP solvent for 2.5 h (power 220 W), stirred until a uniform paste was formed, and degassed for 35 min; the paste was then coated onto calcined carbon cloth current collector with a scraper (load 1.2 mg / cm²), dried at 185°C overnight; and subjected to acid heat treatment (soaking in H2SO4:HNO3=3:1 for 4.5 h, washing, drying, and then heating at 185°C overnight). Step 4, Assembly of the temperature-controlled self-healing flexible supercapacitor: Using reverse evaporation technology: A vacuum was applied to the bottom of the electrode, and GPE was uniformly filled into the electrode and maintained under vacuum for 13 h for curing; the filled electrode and Fh-BN-based separator were stacked into a "sandwich" structure (active area 1.5 cm²) and sealed with Kapton tape; the overall thickness was compressed to 1.2 cm and cut into rectangles (3.5 cm × 1.5 cm); an LTR-rGO film was sprayed onto the electrode surface as a current collector; the resulting supercapacitor has flexibility (>1400 bending cycles, capacity retention >94%), self-healing (efficiency >92%, time <6 min) and isothermal properties (phase change buffer temperature fluctuation 7°C~9°C, suitable for -20°C~60°C). Example 4

[0018] Step 1, Low-temperature reduction of graphene oxide pretreatment stage: Graphene oxide powder was dispersed in deionized water to form a suspension with a concentration of 12 mg / mL; vitamin C was added (molar ratio of GO:reducing agent = 1:5.5), and the mixture was stirred at room temperature (40°C) for 42 h for reduction; the mixture was centrifuged and washed (8000 rpm, 10 min, 4 times with water / ethanol), and vacuum dried (40°C) to obtain LTR-rGO with a reduction degree of 78% and a C / O ratio of 5.8, in order to retain more than 20% of oxygen functional groups to improve interfacial compatibility and pseudocapacitive properties; Step 2, Preparation of silver phase transition core-shell nanoparticles: At room temperature, docosane was dissolved in DCM (mass ratio 1:11) and magnetically stirred for 40 min to form a clear oil phase. For the aqueous phase preparation: CTAB (0.3 g / 40 mL) was added to deionized water and stirred until homogeneous. The aqueous phase was slowly added dropwise to the oil phase (2 mL / min) while simultaneously undergoing high-power ultrasonic dispersion (400 W, 20 min), initially forming a W / O emulsion. After the addition was complete, ultrasonication continued for 7 min, followed by the addition of additional deionized water (containing 0.07 g / 20 mL of PVP stabilizer) and increased stirring speed (1200 rpm) to induce the phase to convert to an O / W emulsion. The mixture was gently heated to 60°C and stirred for 6 h to volatilize the DCM, forming a solid docosane nanocore suspension. Silver nitrate (AgNO3, mass ratio 0.7 g / 1 g core material) was added to the suspension and stirred until dissolved. Sodium citrate solution (2 g / 10 mL water) was slowly added dropwise, and the mixture was stirred at room temperature for 5 h to deposit a silver shell. The mixture was then centrifuged (10000 rpm, 12...). The nanoparticles were washed five times with ethanol and water and dried to obtain dodecane@Ag core-shell nanoparticles with a size of 220 nm. Step 3, Preparation of self-healing gel polymer electrolyte (GPE) and electrode slurry: Preparation of self-healing gel polymer electrolyte (GPE): Alkali lignin (1.8 g) was dissolved in deionized water (35 mL), and NaOH was added to adjust the pH to 9.5. The solution was heated and stirred at 75°C for 1.2 h until completely dissolved, forming a lignin solution. An ionic crosslinking agent, FeCl3 (0.45 g), was added and stirred for 40 min to form a dynamic ionic complex network. H2SO4 (3.8 g) was added as an electrolyte salt to provide ionic conductivity. Fh-BN solution (1.4 mL, concentration 4 mg / mL) and dodecane@Ag core-shell nanoparticles (10 wt%) were added and ultrasonically dispersed for 20 min (200 W) to ensure uniform particle distribution and fusion with lignin via hydrogen bonds. Stirring continued for 1.5 h until homogeneous. The mixture was cooled to room temperature and cured to form a lignin-based self-healing GPE. The self-healing efficiency was >92% achieved synergistically through hydrogen bonding and ionic crosslinking, and ion transport was enhanced by Fh-BN (conductivity >65). mS / cm) and dodecane@Ag particles provide isothermal regulation (phase change enthalpy >150 J / g); Electrode slurry preparation: 82 wt% LTR-rGO, 10 wt% PVDF binder, 1.8 wt% Fh-BN and 10 wt% dodecane@Ag core-shell nanoparticles were mixed; the mixture was ultrasonically dispersed in NMP solvent for 3 h (power 250 W), stirred until a uniform paste was formed, and degassed for 40 min; the paste was then coated onto calcined carbon cloth current collector with a scraper (load 1.4 mg / cm²), dried at 190°C overnight; and subjected to acid heat treatment (soaking in H2SO4:HNO3=3:1 for 5 h, washing, drying, and then heating at 190°C overnight). Step 4, Assembly of the temperature-controlled self-healing flexible supercapacitor: Using reverse evaporation technology: A vacuum was applied to the bottom of the electrode, and GPE was uniformly filled into the electrode and maintained under vacuum for 14 h for curing; the filled electrode and Fh-BN-based separator were stacked into a "sandwich" structure (active area 2 cm²) and sealed with Kapton tape; the overall thickness was compressed to 1.5 cm and cut into rectangles (4 cm × 2 cm); an LTR-rGO film was sprayed onto the electrode surface as a current collector; the resulting supercapacitor has flexibility (>1500 bending cycles, capacity retention >95%), self-healing (efficiency >93%, time <5 min) and isothermal properties (phase change buffer temperature fluctuation 8°C~10°C, suitable for -25°C~65°C). Example 5

[0019] Step 1, Low-temperature reduction of graphene oxide pretreatment stage: Graphene oxide powder was dispersed in deionized water to form a suspension with a concentration of 8 mg / mL; tea polyphenols were added (molar ratio of GO:reducing agent = 1:6), and the mixture was stirred at room temperature (50°C) for 48 h for reduction; the mixture was centrifuged and washed (8000 rpm, 10 min, 5 times with water / ethanol), and vacuum dried (40°C) to obtain LTR-rGO with a reduction degree of 80% and a C / O ratio of 6, in order to retain oxygen functional groups >22% to improve the overall material stability and electrochemical performance; Step 2, Preparation of silver phase transition core-shell nanoparticles: At room temperature, docosane was dissolved in ethyl acetate (mass ratio 1:12) and magnetically stirred for 35 min to form a clear oil phase. For the aqueous phase preparation: CTAB (0.15 g / 40 mL) was added to deionized water and stirred until homogeneous. The aqueous phase was slowly added dropwise to the oil phase (1.8 mL / min) while simultaneously undergoing high-power ultrasonic dispersion (380 W, 19 min), initially forming a W / O emulsion. After the addition was complete, ultrasonication continued for 6 min, followed by the addition of additional deionized water (containing 0.06 g / 20 mL of PVP stabilizer) and increased stirring speed (900 rpm) to induce the phase to transform into an O / W emulsion. The mixture was gently heated to 58°C and stirred for 7 h to volatilize ethyl acetate, forming a solid docosane nanocore suspension. Silver nitrate (AgNO3, mass ratio 0.65 g / 1 g core material) was added to the suspension and stirred until dissolved. Sodium citrate solution (1.7 g / 10 mL water) was slowly added dropwise, and the mixture was stirred at room temperature for 4.5 h to deposit a silver shell. The mixture was then centrifuged (9500 rpm, 11 min). The nanoparticles were washed four times with ethanol and water and dried to obtain docosane@Ag core-shell nanoparticles with a size of 250 nm. Step 3, Preparation of self-healing gel polymer electrolyte (GPE) and electrode slurry: Preparation of self-healing gel polymer electrolyte (GPE): Sulfonated lignin (1.2 g) was dissolved in deionized water (25 mL), and NaOH was added to adjust the pH to 8.5. The solution was heated and stirred at 65°C for 0.8 h until completely dissolved, forming a lignin solution. An ionic crosslinking agent, CaCl2 (0.2 g), was added and stirred for 25 min to form a dynamic ionic complex network. H2SO4 (2.5 g) was added as an electrolyte salt to provide ionic conductivity. Fh-BN solution (0.8 mL, concentration 2.5 mg / mL) and docosane@Ag core-shell nanoparticles (12 wt%) were added and ultrasonically dispersed for 12 min (120 W) to ensure uniform particle distribution and fusion with lignin via hydrogen bonds. Stirring continued for 0.8 h until homogeneous. The mixture was cooled to room temperature and cured to form a lignin-based self-healing GPE. The self-healing efficiency was >88% achieved synergistically through hydrogen bonding and ionic crosslinking, and ion transport was enhanced by Fh-BN (conductivity >58). (mS / cm) and docosane@Ag particles provide isothermal regulation (phase change enthalpy >130 J / g); Electrode slurry preparation: 85 wt% LTR-rGO, 10 wt% PVDF binder, 2 wt% Fh-BN and 12 wt% docosane@Ag core-shell nanoparticles were mixed; the mixture was ultrasonically dispersed in NMP solvent for 2.8 h (power 230 W), stirred until a uniform paste was formed, and degassed for 35 min; the paste was then coated onto calcined carbon cloth current collector with a scraper (load 1.5 mg / cm²), dried at 175°C overnight; and subjected to acid heat treatment (soaking in H2SO4:HNO3=3:1 for 3.5 h, washing, drying, and then heating at 175°C overnight). Step 4, Assembly of the temperature-controlled self-healing flexible supercapacitor: Using reverse evaporation technology: A vacuum was applied to the bottom of the electrode, and GPE was uniformly filled into the electrode and maintained under vacuum for 11 h for curing; the filled electrode and Fh-BN-based separator were stacked into a "sandwich" structure (active area 1.2 cm²) and sealed with Kapton tape; the overall thickness was compressed to 0.8 cm and cut into rectangles (2.5 cm × 1 cm); an LTR-rGO film was sprayed onto the electrode surface as a current collector; the resulting supercapacitor has flexibility (>1300 bending cycles, capacity retention >93%), self-healing (efficiency >90%, time <7 min) and isothermal properties (phase change buffer temperature fluctuation 6°C~9°C, suitable for -18°C~58°C).

Claims

1. This invention provides a method for preparing a temperature-controlled, self-healing flexible supercapacitor, characterized in that, Includes the following steps: Step 1, Low-temperature reduction of graphene oxide pretreatment stage: Graphene oxide powder was dispersed in deionized water to form a suspension with a concentration of 5 mg / mL to 15 mg / mL. A mild reducing agent (such as vitamin C, molar ratio of GO:reducing agent = 1:3 to 1:6) was added, and the mixture was stirred at room temperature (25°C to 50°C) for 24 h to 48 h, or subjected to low-temperature hydrothermal treatment (80°C, in a sealed reactor for 2 to 4 h). The mixture was then centrifuged and washed (8000 rpm, 10 min, 3 to 5 times with water / ethanol), and vacuum dried (40°C) to obtain low-temperature reduced graphene oxide (LTR~rGO), with the degree of reduction controlled at 60% to 80% and the C / O ratio at 4 to 6, in order to retain oxygen functional groups to enhance dispersibility and integration with biomass materials. Step 2, Preparation of silver phase transition core-shell nanoparticles: At room temperature, the core material alkane (selected from octadecane, nonadecane, eicosane, docosane, or docosahexadecane) is dissolved in a volatile solvent (such as dichloromethane DCM, mass ratio 1:8 to 1:12) and magnetically stirred for 20 to 40 minutes until completely dissolved, forming an oil phase. To prepare the aqueous phase, a surfactant (such as CTAB, concentration 0.1 g / 40 mL to 0.3 g / 40 mL) is added to deionized water and stirred until homogeneous. The aqueous phase is slowly added dropwise to the oil phase (dropping rate 0.5 mL / min to 2 mL / min) while simultaneously undergoing high-power ultrasonic dispersion (power 200 W to 400 W, 10 to 20 minutes), initially forming a W / O emulsion. After the dropwise addition is complete, ultrasonication continues for 3 to 7 minutes, followed by the addition of additional deionized water (containing PVP stabilizer, 0.03 g / 20 mL to 0.07 g / 20 mL), increasing the stirring speed (400 rpm to 1200 rpm). The solvent was induced to transform into an O / W emulsion by stirring at 40°C to 60°C for 3 to 7 hours to evaporate the solvent and form a solid alkane nanocore suspension. Silver nitrate (AgNO3, mass ratio 0.3 g / 1 g to 0.7 g / 1 g core material) was added to the suspension and stirred to dissolve. A reducing agent (such as sodium citrate solution, 1 g / 10 mL to 2 g / 10 mL water) was slowly added dropwise and stirred at room temperature for 1 to 5 hours to deposit the silver shell. The mixture was centrifuged (6000 rpm to 10000 rpm, 8 min to 12 min), washed 3 to 5 times with ethanol and water, and dried to obtain alkane@Ag core-shell nanoparticles with a size controlled between 50 nm and 250 nm. Step 3, Preparation of self-healing gel polymer electrolyte (GPE) and electrode slurry: Preparation of self-healing gel polymer electrolyte (GPE): Alkali lignin (1 g–2 g) was dissolved in deionized water (20 mL–40 mL), and NaOH was added to adjust the pH to 8–10. The solution was heated and stirred at 60°C–80°C for 0.5 h–2 h until completely dissolved, forming a lignin solution. An ionic crosslinking agent (such as CaCl2 or FeCl3, 0.1 g–0.5 g) was added, and the mixture was stirred for 20 min–40 min to form a dynamic ionic complex network. H2SO4 (2 g–4 g) was added as an electrolyte salt to provide ionic conductivity. Fh-BN solution (0.5 mL–1.5 mL, concentration 2 mg / mL–4 mg / mL) and alkane@Ag core-shell nanoparticles (loaded 3 wt%–12 wt%) were added, and the mixture was ultrasonically dispersed for 10 min–20 min (power 100 W–200 W) to ensure uniform particle distribution and fusion with lignin through hydrogen bonds. The mixture was stirred for another 0.5 h–1.5 h. h until homogeneous; cool to room temperature to cure, forming lignin-based self-healing GPE, in which hydrogen bonding and ionic crosslinking synergistically achieve self-healing efficiency >80%, and Fh-BN enhances ion transport (conductivity >50 mS / cm) and alkane@Ag particles provide isothermal regulation (phase change enthalpy >100 J / g). Electrode paste preparation: Mix 70 wt%~85 wt% LTR-rGO, 8 wt%~10 wt% PVDF binder, 0.5 wt%~2 wt% Fh-BN and 3 wt%~12 wt% alkane@Ag core-shell nanoparticles; ultrasonically disperse in NMP solvent for 1 h~3 h (power 150W~250 W), stir until a uniform paste is formed, and degas for 20 min~40 min; coat with a scraper onto calcined carbon cloth current collector (load 0.5 mg / cm²~1.5 mg / cm²), and dry at 170°C~190°C overnight; perform acid heat treatment (soak in H2SO4:HNO3=3:1 for 3 h~5 h, wash, dry, and then heat at 170°C~190°C overnight); Step 4, Assembly of the temperature-controlled self-healing flexible supercapacitor: Using reverse evaporation technology: A vacuum is applied to the bottom of the electrode, and GPE is uniformly filled into the electrode and maintained under vacuum for 10 h to 14 h for curing; the filled electrode and Fh-BN-based separator are stacked into a "sandwich" structure (active area 0.5 cm² to 2 cm²) and sealed with Kapton tape; the overall thickness is compressed to 0.5 cm to 1.5 cm and cut into rectangles (2 cm to 4 cm × 0.5 cm to 2 cm); an LTR-rGO film is sprayed onto the electrode surface as a current collector; the resulting supercapacitor has flexibility (>1000 bending cycles, capacity retention >90%), self-healing (efficiency >85%, time <10 min) and isothermal properties (phase change buffer temperature fluctuation 5°C to 10°C, suitable for ~20°C to ~60°C).

2. The method for fabricating a temperature-controlled self-healing flexible supercapacitor according to claim 1, characterized in that, In step 1, the low-temperature reduction temperature is 25°C to 80°C, and the reducing agent is selected from vitamin C or tea polyphenols, retaining an oxygen functional group content of >15% to improve dispersibility and pseudocapacitive contribution.

3. The method for fabricating a temperature-controlled self-healing flexible supercapacitor according to claim 1, characterized in that, In step 2, the core material alkane is selected from octadecane, nonadecane, eicosane, docosane, or docosane to achieve different phase transition temperatures (25°C~45°C); the volatile solvent is selected from dichloromethane or ethyl acetate; the reverse-phase dropping rate is 0.5 mL / min~2 mL / min; and sodium citrate is used as a reducing agent for silver shell deposition.

4. The method for fabricating a temperature-controlled self-healing flexible supercapacitor according to claim 1, characterized in that, In step 3, the lignin is alkali lignin or sulfonated lignin, the ionic crosslinking agent is selected from CaCl2 or FeCl3, the alkane@Ag core-shell nanoparticle loading is 3 wt%~12 wt%, the Fh-BN concentration is 2 mg / mL~4 mg / mL, and the H2SO4 concentration in the GPE preparation is 2 g / 30 mL~4 g / 30 mL, providing an ionic conductivity >50 mS / cm.

5. The method for fabricating a temperature-controlled self-healing flexible supercapacitor according to claim 1, characterized in that, In step 3, the LTR-rGO ratio of the electrode slurry is 70 wt%~85 wt%, the ultrasonic dispersion power is 150 W~250 W, and the acid heat treatment uses an H2SO4:HNO3 volume ratio of 3:

1.

6. A method for fabricating a temperature-controlled self-healing flexible supercapacitor according to claim 1, characterized in that, In step 4, the reverse evaporation vacuum maintenance time is 10 h to 14 h, the supercapacitor structure is a "sandwich" stack, suitable for wearable devices, and has a specific capacitance > 400 F / g and a cycle life > 40,000 times.

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