Bismuth / carbonized silk fabric flexible sodium battery negative electrode material as well as preparation method and application thereof

Abstract

The invention discloses a bismuth / carbonized silk fabric flexible sodium battery negative electrode material as well as a preparation method and application thereof, and belongs to the technical field of battery negative electrode materials. The preparation method comprises the following steps: soaking a silk fabric in a hydrochloric acid solution, a 3-aminopropyltriethoxysilane solution and a bismuth chloride-polyvinylpyrrolidone solution in sequence to obtain a bismuth ion-loaded silk fabric; putting the silk fabric loaded with the bismuth ions into a sodium hypophosphite monohydrate solution for in-situ reduction to obtain a composite material; and finally calcining and cooling the composite material to obtain the bismuth / carbonized silk fabric flexible sodium battery negative electrode material. The bismuth / carbonized silk fabric flexible sodium battery negative electrode material prepared by the preparation method disclosed by the invention has excellent cycling stability, high-current charge-discharge capability, excellent rate capability and good flexibility.

Description

Technical Field

[0001] This invention relates to a bismuth / carbide filament flexible sodium battery anode material, its preparation method and application, belonging to the technical field of battery anode materials. Background Technology

[0002] The global energy system is accelerating its transition towards a renewable energy-dominated model, and large-scale energy storage technology has become a key pillar supporting the consumption of new energy sources such as photovoltaics and wind power. Simultaneously, the rapid iteration and upgrading of portable electronic devices are driving innovation in energy storage devices towards lower cost and higher safety. Sodium-ion batteries (SIBs), with their significant cost advantages and excellent safety performance, have become an ideal alternative to lithium-ion batteries (LIBs) in low-to-medium energy density applications.

[0003] In practical applications, SIBs exhibit superior safety performance compared to LIBs—their organic electrolytes have a higher ignition point, giving SIBs a unique advantage in scenarios requiring close contact with the human body, such as wearable devices. The explosive growth of flexible electronic devices in recent years further highlights the application potential of SIBs: wearable wristbands, flexible displays, and other devices place stringent requirements on the bending and folding tolerance of power supplies, while SIBs, through reasonable structural optimization design, can simultaneously meet the dual demands of flexibility and high safety, making them more promising for industrialization compared to flexible LIBs. As the core carrier for sodium storage in flexible SIBs, the anode material must balance three key properties: excellent electrochemical sodium storage performance, stable structural stability, and good mechanical flexibility.

[0004] Alloy anode materials, as highly promising high-capacity anode materials, have attracted widespread attention due to their high sodium storage capacity based on alloying reactions. Among them, elemental bismuth has become a research hotspot due to its theoretical capacity of 385 mAh / g, excellent electrochemical alloying reaction kinetics, high abundance in the Earth's crust, and stable chemical properties. However, during charge and discharge, the volume expansion caused by the alloying reaction easily leads to electrode structure collapse and active material shedding, which seriously limits its practical application.

[0005] Therefore, developing a battery anode material that is simple to prepare, has mild conditions, and possesses good flexibility, cycle stability, and charge / discharge capability has extremely high practical and economic value. Summary of the Invention

[0006] To address the limited research on flexible sodium-ion battery anode materials, the poor conductivity of bismuth anode materials, and the poor cycle stability caused by volume expansion during charge and discharge, this invention involves sequentially impregnating silk fabric in hydrochloric acid solution, 3-aminopropyltriethoxysilane solution, and bismuth chloride-polyvinylpyrrolidone solution to obtain bismuth-loaded silk fabric. The bismuth-loaded silk fabric is then subjected to in-situ reduction in a sodium hypophosphite monohydrate solution to obtain a composite material. Finally, the composite material is calcined and cooled to obtain a bismuth / carbide silk fabric flexible sodium battery anode material. The bismuth / carbide silk fabric flexible sodium battery anode material prepared by this invention exhibits excellent cycle stability, high-current charge and discharge capability, and good flexibility.

[0007] The first objective of this invention is to provide a method for preparing a bismuth / carbide filament flexible sodium electrode anode material, comprising the steps of: (1) Waste silk fabrics are placed in alcohol, ultrasonically cleaned and dried to obtain silk fabrics; (2) The silk fabric is immersed in hydrochloric acid solution, taken out and rinsed until neutral and dried; then it is immersed in 3-aminopropyltriethoxysilane solution and mixed solution in turn to obtain silk fabric loaded with bismuth ions; wherein, bismuth chloride solution and polyvinylpyrrolidone solution are mixed to obtain mixed solution; (3) The silk fabric loaded with bismuth ions was reduced in a sodium hypophosphite monohydrate solution; after reduction, it was washed and dried to obtain the Bi-silk textile composite material. (4) The Bi-silk textile composite material was calcined and cooled to obtain a bismuth / carbonized filament flexible sodium electrode anode material.

[0008] In one embodiment, the silk fabric in step (1) can be cut into a rectangle; optionally, the cutting size is 4cm × 8cm.

[0009] In one embodiment, in step (2), the concentration of the hydrochloric acid solution is 0.01~0.10 M, the concentration of the 3-aminopropyltriethoxysilane solution is 1~15%, the concentration of the bismuth chloride solution is 0.1~1.0 M, and the concentration of the polyvinylpyrrolidone solution is 5~40 mg·mL. -1 .

[0010] Optionally, the ratio of the amount of silk fabric, hydrochloric acid solution, 3-aminopropyltriethoxysilane solution and mixed solution is 1~2 g: 20~60 mL: 10~40 mL: 12~40 mL; Optionally, the silk fabric is immersed in hydrochloric acid solution for 0.5-3 h, in 3-aminopropyltriethoxysilane solution for 8-72 h, or in a mixed solution of bismuth chloride and polyvinylpyrrolidone for 8-72 h. Optionally, the silk fabric is impregnated in hydrochloric acid solution at a temperature of 20-30°C, in 3-aminopropyltriethoxysilane solution at a temperature of 20-30°C, or in a mixed solution of bismuth chloride and polyvinylpyrrolidone at a temperature of 20-30°C.

[0011] In one embodiment, the ratio of the amount of silk fabric, hydrochloric acid solution, 3-aminopropyltriethoxysilane solution, bismuth chloride solution and polyvinylpyrrolidone solution used for soaking in step (2) is 1~2 g: 20~60 mL: 10~40 mL: 10~30 mL: 2~10 mL.

[0012] In one embodiment, the ratio of the amount of bismuth-loaded silk fabric to sodium phosphite monohydrate solution in step (3) is 1~2 g: 80~120 mL. Optionally, the concentration of the sodium hypophosphite monohydrate solution is 0.1~2.0 M; Optionally, the reduction temperature is 30~90 ℃; Optionally, the restoration time is 1 to 5 hours.

[0013] In one embodiment, the ratio of the amount of bismuth-loaded silk fabric to sodium hypophosphite monohydrate solution in step (3) is 1~2 g: 80~120 mL.

[0014] In one embodiment, the calcination in step (4) is carried out by heating from room temperature to 600~950°C under an inert atmosphere. Optionally, the heating rate is 1~5 ℃ / min; Optionally, the heat preservation time is 1 to 4 hours.

[0015] A second objective of this invention is to provide a bismuth / carbide filament flexible sodium electrode anode material prepared by any of the methods described above.

[0016] A third objective of this invention is to provide the application of the aforementioned bismuth / carbide filament flexible sodium electrode material in sodium-ion batteries or wearable electronic devices.

[0017] The fourth objective of this invention is to provide a method for improving the cycle stability of sodium-ion batteries, wherein a sodium-ion battery is prepared using a bismuth / carbide filament flexible sodium-ion battery anode material; the preparation method of the bismuth / carbide filament flexible sodium-ion battery anode material includes the following steps: (1) Waste silk fabrics are placed in alcohol, ultrasonically cleaned and dried to obtain silk fabrics; (2) The silk fabric is immersed in hydrochloric acid solution, taken out and rinsed until neutral and dried; then it is immersed in 3-aminopropyltriethoxysilane solution and mixed solution in turn to obtain silk fabric loaded with bismuth ions; wherein, bismuth chloride solution and polyvinylpyrrolidone solution are mixed to obtain mixed solution; (3) The silk fabric loaded with bismuth ions was reduced in a sodium hypophosphite monohydrate solution; after reduction, it was washed and dried to obtain the Bi-silk textile composite material. (4) The Bi-silk textile composite material was calcined and cooled to obtain a bismuth / carbonized filament flexible sodium electrode anode material.

[0018] In one embodiment, in step (2), the concentration of the hydrochloric acid solution is 0.01~0.10 M, the concentration of the 3-aminopropyltriethoxysilane solution is 1~15%, the concentration of the bismuth chloride solution is 0.1~1.0 M, and the concentration of the polyvinylpyrrolidone solution is 5~40 mg·mL. -1 .

[0019] Optionally, the silk fabric is immersed in hydrochloric acid solution for 0.5-3 h, in 3-aminopropyltriethoxysilane solution for 8-72 h, or in a mixed solution of bismuth chloride and polyvinylpyrrolidone for 8-72 h. Optionally, the silk fabric is impregnated in hydrochloric acid solution at a temperature of 20-30°C, in 3-aminopropyltriethoxysilane solution at a temperature of 20-30°C, or in a mixed solution of bismuth chloride and polyvinylpyrrolidone at a temperature of 20-30°C.

[0020] In one embodiment, the ratio of the amount of silk fabric, hydrochloric acid solution, 3-aminopropyltriethoxysilane solution, bismuth chloride solution and polyvinylpyrrolidone solution used for soaking in step (2) is 1~2 g: 20~60 mL: 10~40 mL: 10~30 mL: 2~10 mL.

[0021] In one embodiment, the concentration of the sodium hypophosphite monohydrate solution in step (3) is 0.1~2.0 M; Optionally, the reduction temperature is 30~90 ℃; Optionally, the restoration time is 1 to 5 hours.

[0022] In one embodiment, the ratio of the amount of bismuth-loaded silk fabric to sodium hypophosphite monohydrate solution in step (3) is 1~2 g: 80~120 mL.

[0023] In one embodiment, the calcination in step (4) is carried out by heating from room temperature to 600~950°C under an inert atmosphere. Optionally, the heating rate is 1~5 ℃ / min; Optionally, the heat preservation time is 1 to 4 hours.

[0024] Beneficial effects of the present invention This invention involves immersing silk fabric in hydrochloric acid solution, 3-aminopropyltriethoxysilane solution, and bismuth chloride-polyvinylpyrrolidone solution to obtain bismuth-loaded silk fabric; then, the bismuth-loaded silk fabric is placed in a sodium hypophosphite monohydrate solution for in-situ reduction to obtain a composite material; finally, the composite material is calcined and cooled to obtain a bismuth / carbonized silk fabric flexible sodium electrode anode material.

[0025] Specifically: The bismuth / carbide filament flexible sodium electrode anode material prepared by this invention can withstand current densities of 5 mA·cm⁻¹. -2 After 1000 cycles, the discharge specific capacity decreased from 0.80 to 0.66 mAh·cm⁻¹. -2 The capacity retention rate reached 82.5%; Bismuth / carbide filament flexible sodium-ion battery anode material was used as an anode material in 0.3 cm⁻¹. -2 After 10 cycles, the discharge specific capacity is 1.34 mAh·cm⁻¹. -2 When the current density increases to 0.5 cm⁻¹ -2 0.7 cm -2 1 cm -2 1.5 cm -2 2cm -2 3 cm -2 5 cm -2 The discharge specific capacities were 1.17, 1.06, 1.05, 1.03, 0.98, 0.96, and 0.90 mAh·cm⁻¹, respectively. -2 When the current density decreases sequentially to 3 cm -2 2 cm -2 1.5 cm -2 1 cm -2 0.7 cm -2 0.5 cm -2 0.3 cm -2 At that time, the discharge specific capacity recovered to 0.92, 0.93, 0.93, 0.93, 0.93, 0.95, and 1.04 mAh·cm⁻¹. -2 The discharge specific capacity remains stable at different current densities, demonstrating excellent rate performance.

[0026] At a current density of 0.3 mA·cm -2After 200 cycles, the discharge specific capacity remained relatively stable at 1.1 mAh·cm⁻¹. -2 about.

[0027] The bismuth / carbide filament flexible sodium electrode anode material prepared by this invention has excellent cycle stability, high current charge and discharge capability, excellent rate performance, and good flexibility. Attached Figure Description

[0028] Figure 1 The structure of the bismuth / carbide filament anode material prepared in Example 1 is characterized.

[0029] Figure 2 The X-ray diffraction patterns are those of the bismuth / carbide filament anode materials prepared in Examples 1-3.

[0030] Figure 3 This is a transmission electron microscope image of the bismuth / carbide filament anode material prepared in Example 1.

[0031] Figure 4 The bismuth / carbide filament anode material prepared in Example 1 was tested at a current density of 5 mA·cm⁻¹. -2 The following is a graph showing the cyclic performance.

[0032] Figure 5 The bismuth / carbide filament anode materials prepared in Examples 1-3 were compared at different current densities of 0.3 cm⁻¹. -2 0.5cm -2 0.7 cm -2 1 cm -2 1.5 cm -2 2 cm -2 3 cm -2 5 cm -2 3 cm -2 2 cm -2 1.5 cm -2 1 cm -2 0.7cm -2 0.5 cm -2 0.3 cm -2 The following is a graph showing the rate performance.

[0033] Figure 6 The image shows a flexible test image of the bismuth / carbide filament anode material prepared in Example 1.

[0034] Figure 7 The structure of the bismuth / carbide filament anode material prepared in Example 2 is characterized.

[0035] Figure 8The structure of the bismuth / carbide filament anode material prepared in Example 3 is characterized.

[0036] Figure 9 The bismuth / carbide filament anode materials prepared at different calcination temperatures in Examples 1-3 are compared at a current density of 0.3 mA·cm⁻¹. -2 The following is a graph showing the cyclic performance.

[0037] Figure 10 The bismuth / carbide filament anode materials prepared at different reduction temperatures in Examples 1, 4, and 5 are used at a current density of 0.3 mA·cm⁻¹. -2 The following is a graph showing the cyclic performance.

[0038] Figure 11 The bismuth / carbide filament anode materials prepared at different reduction times in Examples 1, 6, and 7 are used at a current density of 0.3 mA·cm⁻¹. -2 The following is a graph showing the cyclic performance.

[0039] Figure 12 The bismuth / carbide filament anode materials prepared by different impregnation methods in Examples 1 and 8 were tested at a current density of 0.3 mA·cm⁻¹. -2 The following is a graph showing the cyclic performance.

[0040] Figure 13 The structure of the negative electrode material prepared in Comparative Example 1 is characterized.

[0041] Figure 14 The structure of the negative electrode material prepared in Comparative Example 2 is characterized.

[0042] Figure 15 The negative electrode material prepared in Comparative Example 1 was at 0.3 mA·cm -2 The following is a cycle performance diagram; solid parts represent discharge, and hollow parts represent charging.

[0043] Figure 16 The negative electrode material prepared in Comparative Example 2 was subjected to a current density of 0.3 mA·cm⁻¹. -2 The following is a graph showing the cyclic performance.

[0044] Figure 17 The negative electrode material prepared in Comparative Example 3 was tested at a current density of 0.3 mA·cm⁻¹. -2 The following is a graph showing the cyclic performance.

[0045] Figure 18 The negative electrode material prepared in Comparative Example 4 was subjected to a current density of 0.3 mA·cm⁻¹. -2 The following is a graph showing the cyclic performance. Detailed Implementation

[0046] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0047] Conventional methods (such as hydrothermal methods) for bonding bismuth to flexible materials typically involve reacting precursors in a high-temperature, high-pressure solution to generate elemental bismuth, which is then simultaneously loaded onto silk. However, this inherent property presents significant challenges in meeting the flexibility requirements of the silk substrate and the need for uniform bismuth loading. For example: (1) Under high pressure, the pore structure of silk fibers is compressed, loses its fluffiness, and becomes dense and brittle. Even if it is not calcined afterward, the silk after hydrothermal treatment is prone to lose its flexibility and cannot meet the flexibility requirements of carbonized silk fabrics after calcination. (2) The formation of bismuth element is simultaneous with the loading, the reaction rate is fast, and there is a lack of effective dispersion mechanism, making it difficult to control the morphology; (3) The binding of bismuth particles to silk mainly relies on physical adsorption and lacks chemical bonding. During the charging and discharging process of sodium batteries, bismuth will undergo significant volume expansion. Repeated volume changes will cause bismuth particles to fall off the silk substrate, resulting in rapid capacity decay and short circuits.

[0048] Inspired by capillary nutrient transport, this invention utilizes a porous bismuth cluster structure formed by in-situ reduction as a porous pre-template. During calcination, the bismuth structure becomes porous. Compared to other preparation methods, the synthesis conditions of this invention are mild, simple, controllable, and low-cost. Furthermore, the polyvinylpyrrolidone-derived carbon layer after carbonization coats the bismuth surface, and the porous bismuth formed by in-situ reduction and calcination is uniformly dispersed in the nitrogen-doped carbon matrix. This structure provides sufficient buffer space for volume expansion during cycling and accelerates ion / electron transport, effectively improving the battery's long-cycle stability and rate performance. Therefore, the flexible self-supporting bismuth / carbonized filament fabric prepared by this invention exhibits excellent high-current charge / discharge capability and cycle stability when used as a negative electrode material for sodium-ion batteries.

[0049] This invention first prepares bismuth-loaded silk fabric by impregnation, which is then in-situ reduced in a sodium hypophosphite monohydrate solution to form Bi-silk textile. Subsequently, a porous bismuth structure is formed during calcination. After carbonization, a nitrogen-doped carbon layer derived from polyvinylpyrrolidone coats the bismuth surface, and the silk fabric forms a nitrogen-doped carbon matrix after carbonization. By controlling the calcination temperature, reduction temperature, and reduction time, the uniformity and porosity of the bismuth structure can be controlled, thereby achieving a controllable porous structure and uniform dispersion of bismuth on the carbon matrix. This method is simple, has a short process, and is under mild conditions.

[0050] Raw materials used in the examples: The waste silk fabrics come from garment factories and are plain weave silk fabrics with a specification of 19 momme; Hydrochloric acid was purchased from Sinopharm Chemical Reagent Co., Ltd., 3-aminopropyltriethoxysilane was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., bismuth chloride was purchased from Shanghai Titan Technology Co., Ltd., and polyvinylpyrrolidone was purchased from Shanghai Titan Technology Co., Ltd. Sodium hypophosphite monohydrate was purchased from Shanghai McLean Biochemical Technology Co., Ltd.

[0051] Test method: Cyclic performance test: Before the test, at 0.1 A·g -1 Activation was performed at a low current density for 10 weeks. Afterwards, a bismuth / carbide filament flexible sodium electrode was assembled with a sodium sheet to form a coin cell sodium-ion battery, operating at 0.3 mA·cm⁻¹. -2 Current density and cyclic testing were performed at 25 °C.

[0052] In the following examples, unless otherwise specified, the operating temperature is room temperature (20~30°C); and unless otherwise mentioned, the solvent is water.

[0053] Example 1 1. A method for preparing a bismuth / carbide filament flexible sodium electrode anode material, comprising the following steps: (1) The waste silk fabric was placed in alcohol, ultrasonically cleaned multiple times, dried, and cut into rectangular silk fabric (4cm×8cm). (2) 15 mL of 0.5 M bismuth chloride solution and 5 mL of 20 mg·mL⁻¹ -1 The polyvinylpyrrolidone solution was mixed to obtain a mixed solution; 1.2 g of rectangular silk fabric was immersed in 40 mL of 0.05 M hydrochloric acid solution at 25 °C for 1 h. After removal, it was rinsed several times with deionized water until neutral and then dried. The dried rectangular silk fabric was immersed in 20 mL of 5% (v / v) 3-aminopropyltriethoxysilane solution at 25 °C for 24 h, and then immersed in a mixed solution at 25 °C for 24 h to obtain bismuth-loaded silk fabric. (3) The silk fabric loaded with bismuth ions was placed in 100 mL of 0.8 M sodium hypophosphite monohydrate solution and reduced at 60 °C for 3 h. After the reduction was completed, the fabric was washed in deionized water and then vacuum dried at 60 °C to obtain Bi-silk textile composite material. (4) The Bi-silk textile composite material was placed in a tube furnace for calcination. Under the protection of an inert atmosphere (nitrogen), the temperature was raised from room temperature to 800 ℃ at a rate of 2 ℃ / min. After holding at 800 ℃ for 3 h, it was cooled to room temperature to obtain the bismuth / carbide filament flexible sodium electrode anode material.

[0054] 2. Structural characterization The structural characterization of the bismuth / carbide filament flexible sodium electrode material prepared in step 1 is as follows: Figure 1 As shown; X-ray diffraction pattern as follows Figure 2 As shown, the results indicate that the main phase of the flexible sodium electrode anode material is bismuth, and its data is consistent with the standard data (JCPDS No. 05-0519). The carbon in it is amorphous carbon, and no obvious diffraction peaks are visible. Transmission electron microscope image as shown Figure 3 As shown, the results indicate that polyvinylpyrrolidone is converted into a carbon layer on the bismuth surface, and the bismuth atoms are coated by the carbon layer.

[0055] 3. Performance Testing The bismuth / carbide filament flexible sodium electrode anode material prepared in step 1 operates at a current density of 5 mA·cm⁻¹. -2 The following are the cycle performance results: Figure 4 As shown, the results indicate that after 1000 cycles, the discharge specific capacity decreased from 0.80 to 0.66 mAh·cm⁻¹. -2 It achieved a capacity retention rate of 82.5%, demonstrating excellent cycle stability.

[0056] Bismuth / carbide filament flexible sodium electrode material was used as a negative electrode material for sodium-ion batteries at different current densities of 0.3 cm⁻¹. -2 0.5 cm -2 0.7 cm -2 1 cm -2 1.5 cm -2 2 cm -2 3 cm -2 5 cm -2 3 cm -2 2 cm -2 1.5 cm -2 1cm -2 0.7 cm -2 0.5 cm -2 0.3 cm -2 The following are the performance results at the rate of magnification: Figure 5 As shown, the results indicate that at 0.3 cm -2 After 10 cycles, the discharge specific capacity is 1.34 mAh·cm⁻¹. -2 When the current density increases to 0.5 cm⁻¹ -2 0.7 cm -2 1 cm -2 1.5 cm -2 2 cm -2 3 cm -2 5 cm-2 The discharge specific capacities were 1.17, 1.06, 1.05, 1.03, 0.98, 0.96, and 0.90 mAh·cm⁻¹, respectively. -2 When the current density decreases sequentially to 3 cm -2 2 cm -2 1.5 cm -2 1 cm -2 0.7 cm -2 0.5 cm -2 0.3 cm -2 At that time, the discharge specific capacity recovered to 0.92, 0.93, 0.93, 0.93, 0.93, 0.95, and 1.04 mAh·cm⁻¹. -2 The discharge specific capacity remains stable at a high capacity level under different current densities, exhibiting excellent rate performance.

[0057] Flexible test structure of bismuth / carbide filament fabric flexible sodium electrode anode material, such as Figure 6 As shown, the results indicate that the negative electrode material can recover its original shape regardless of whether it is bent in the latitudinal direction, bent in the longitudinal direction, or folded. This demonstrates that the negative electrode material has good flexibility and can be directly used as a negative electrode material for sodium-ion batteries.

[0058] Example 2 Based on Example 1, the calcination temperature in step (4) was changed to 600 °C, while the other steps remained the same, to prepare a bismuth / carbonized filament flexible sodium electrode anode material.

[0059] X-ray diffraction pattern as follows Figure 2 As shown, the rate performance results under different current densities are as follows: Figure 5 As shown, the structure is as follows Figure 7 As shown.

[0060] Example 3 Based on Example 1, the calcination temperature in step (4) was changed to 950 °C, while the other steps remained the same, to prepare a bismuth / carbonized filament flexible sodium electrode anode material.

[0061] X-ray diffraction pattern as follows Figure 2 As shown, the rate performance results under different current densities are as follows: Figure 5 As shown, the structure is as follows Figure 8 As shown.

[0062] The X-ray diffraction patterns of the bismuth / carbide filament flexible sodium electrode materials prepared in Examples 1-3 are shown below. Figure 2 As shown, the results indicate that the main phase of the flexible sodium electrode anode material is elemental bismuth, and its data are consistent with the standard data (JCPDS No. 05-0519); the rate performance results at different current densities are as follows: Figure 5 As shown, the discharge specific capacity of Example 1 remained stable at a high capacity level under different current densities, while the capacity of Example 2 decreased more rapidly, and the capacity of Example 3 was lower; the discharge specific capacity was detected at a current density of 0.3 mA·cm⁻¹. -2 The loop performance is as follows: Figure 9 As shown.

[0063] The results showed that the discharge specific capacity remained relatively stable after 200 cycles, with Example 1 exhibiting the highest discharge specific capacity, maintained at 1.1 mAh·cm⁻¹. -2 If the calcination temperature is too low, the discharge specific capacity will decrease after a certain number of cycles; if the calcination temperature is too high, the discharge specific capacity will decrease. Example 4 Based on Example 1, the reduction temperature in step (3) was changed to 30 °C, while the other steps remained the same, to prepare a bismuth / carbonized filament flexible sodium electrode anode material.

[0064] Example 5 Based on Example 1, the reduction temperature in step (3) was changed to 90 °C, while the other steps remained the same, to prepare a bismuth / carbonized filament flexible sodium electrode anode material.

[0065] The bismuth / carbide filament flexible sodium electrode anode materials prepared in Examples 1, 4, and 5 were tested at a current density of 0.3 mA·cm⁻¹. -2 The loop performance is as follows: Figure 10 As shown in the figure. The results indicate that excessively high reduction temperatures reduce the discharge specific capacity, while excessively low reduction temperatures significantly reduce the discharge specific capacity.

[0066] Example 6 Based on Example 1, the reduction time in step (3) was changed to 1 h, while the other steps remained the same, and a bismuth / carbide filament flexible sodium electrode anode material was prepared.

[0067] Example 7 Based on Example 1, the reduction time in step (3) was changed to 5 h, while the other steps remained the same, and a bismuth / carbide filament flexible sodium electrode anode material was prepared.

[0068] The bismuth / carbide filament flexible sodium electrode anode materials prepared in Examples 1, 6, and 7 were tested at a current density of 0.3 mA·cm⁻¹. -2 The loop performance is as follows: Figure 11 As shown in the figure. The results indicate that excessively long reduction time will reduce the discharge specific capacity; excessively short reduction time will significantly reduce the discharge specific capacity.

[0069] Example 8 Based on Example 1, the impregnation method in step (2) was changed to impregnation in a mixed solution of 3-aminopropyltriethoxysilane solution, bismuth chloride and polyvinylpyrrolidone, while the remaining steps remained the same, to prepare a bismuth / carbonized filament flexible sodium electrode anode material.

[0070] The bismuth / carbide filament flexible sodium electrode anode materials prepared in Examples 1 and 8 were tested at a current density of 0.3 mA·cm⁻¹. -2 The loop performance is as follows: Figure 12 As shown in the figure. The results indicate that changing the impregnation method leads to a decrease in discharge specific capacity.

[0071] Comparative Example 1 Based on Example 1, step (2) was changed so that the material was not impregnated with 3-aminopropyltriethoxysilane solution, but only with a mixture of hydrochloric acid solution, bismuth chloride solution and polyvinylpyrrolidone solution. The remaining steps remained the same, and the negative electrode material was obtained.

[0072] Structure as Figure 13 As shown, the negative electrode material was tested at 0.3 mA·cm⁻¹. -2 The loop performance is as follows: Figure 15 As shown, the results indicate that the discharge specific capacity is significantly lower than that of Example 1.

[0073] Comparative Example 2 Based on Example 1, the mixed solution in step (2) was modified so that polyvinylpyrrolidone was not added, and only hydrochloric acid solution, 3-aminopropyltriethoxysilane solution and bismuth chloride solution were used for impregnation treatment, while the other steps remained the same, to obtain the negative electrode material.

[0074] Structure as Figure 14 As shown, the negative electrode material was tested at 0.3 mA·cm⁻¹. -2 The loop performance is as follows: Figure 16 As shown, the results indicate that the discharge specific capacity decreased significantly compared to Example 1, and a short circuit occurred.

[0075] Comparative Example 3 Based on Example 1, steps (2) and (3) are omitted, while the remaining steps remain the same to obtain the negative electrode material.

[0076] The negative electrode material was tested at 0.3 mA·cm⁻¹. -2 The loop performance is as follows: Figure 17 As shown, the results indicate that the discharge specific capacity is significantly lower than that of Example 1.

[0077] Comparative Example 4 The negative electrode is prepared using aluminum foil as the current collector using a traditional coating method, and the steps are as follows: The negative electrode material was obtained by mixing bismuth powder (active material), carbon black (conductive material) and polyvinylidene fluoride (binder) in a mass ratio of 7:2:1, adding N-methylpyrrolidone and grinding it into a slurry, then coating the prepared slurry onto carbon-coated aluminum foil and drying it in a vacuum oven at 60 °C for 10 h.

[0078] The negative electrode material was tested at 0.3 mA·cm⁻¹. -2 The loop performance is as follows: Figure 18 As shown, the results indicate that the discharge specific capacity decreased significantly compared to Example 1, and a short circuit occurred.

[0079] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for preparing bismuth / carbide filament flexible sodium electrode anode material, characterized in that, Including the following steps: (1) Waste silk fabrics are placed in alcohol, ultrasonically cleaned and dried to obtain silk fabrics; (2) The silk fabric is immersed in hydrochloric acid solution, then rinsed until neutral and dried. The silk fabric loaded with bismuth ions was obtained by impregnating it sequentially in a 3-aminopropyltriethoxysilane solution and a mixed solution; wherein, a bismuth chloride solution and a polyvinylpyrrolidone solution were mixed to obtain the mixed solution. (3) The silk fabric loaded with bismuth ions was reduced in a sodium hypophosphite monohydrate solution; After reduction, the material is cleaned and dried to obtain the Bi-silk textile composite material. (4) The Bi-silk textile composite material was calcined and cooled to obtain a bismuth / carbonized filament flexible sodium electrode anode material.

2. The method according to claim 1, characterized in that, In step (2), the concentration of hydrochloric acid solution is 0.01~0.10 M, the concentration of 3-aminopropyltriethoxysilane solution is 1~15%, the concentration of bismuth chloride solution is 0.1~1.0 M, and the concentration of polyvinylpyrrolidone solution is 5~40 mg·mL. -1 ; Optionally, the ratio of the amount of silk fabric, hydrochloric acid solution, 3-aminopropyltriethoxysilane solution and mixed solution is 1~2g: 20~60 mL: 10~40 mL: 12~40 mL.

3. The method according to claim 1, characterized in that, In step (2), the silk fabric is immersed in hydrochloric acid solution for 0.5-3 h, in 3-aminopropyltriethoxysilane solution for 8-72 h, and in a mixed solution of bismuth chloride and polyvinylpyrrolidone for 8-72 h. Optionally, the silk fabric is impregnated in hydrochloric acid solution at a temperature of 20-30°C, in 3-aminopropyltriethoxysilane solution at a temperature of 20-30°C, or in a mixed solution of bismuth chloride and polyvinylpyrrolidone at a temperature of 20-30°C.

4. The method according to claim 1, characterized in that, In step (3), the ratio of bismuth-loaded silk fabric to sodium phosphite monohydrate solution is 1~2 g: 80~120 mL; Optionally, the concentration of the sodium hypophosphite monohydrate solution is 0.1~2.0 M; Optionally, the reduction temperature is 30~90 ℃; Optionally, the restoration time is 1 to 5 hours.

5. The method according to claim 1, characterized in that, In step (4), calcination is carried out by raising the temperature from room temperature to 600~950 ℃ under an inert atmosphere. Optionally, the heating rate is 1~5 ℃ / min; Optionally, the heat preservation time is 1 to 4 hours.

6. The bismuth / carbide filament flexible sodium electrode anode material prepared by the method according to any one of claims 1 to 5.

7. The application of the bismuth / carbide filament flexible sodium electrode material according to claim 6 in the preparation of sodium-ion batteries or wearable electronic devices.

8. A method for improving the cycle stability of a sodium-ion battery, characterized in that, Sodium-ion batteries are prepared using bismuth / carbide filament flexible sodium anode material; the preparation method of the bismuth / carbide filament flexible sodium anode material includes the following steps: (1) Waste silk fabrics are placed in alcohol, ultrasonically cleaned and dried to obtain silk fabrics; (2) The silk fabric is immersed in hydrochloric acid solution, then rinsed until neutral and dried. The silk fabric loaded with bismuth ions was obtained by impregnating it sequentially in a 3-aminopropyltriethoxysilane solution and a mixed solution; wherein, a bismuth chloride solution and a polyvinylpyrrolidone solution were mixed to obtain the mixed solution. (3) The silk fabric loaded with bismuth ions was reduced in a sodium hypophosphite monohydrate solution; After reduction, the material is cleaned and dried to obtain the Bi-silk textile composite material. (4) The Bi-silk textile composite material was calcined and cooled to obtain a bismuth / carbonized filament flexible sodium electrode anode material.

9. The method according to claim 7, characterized in that, In step (2), the concentration of hydrochloric acid solution is 0.01~0.10 M, the concentration of 3-aminopropyltriethoxysilane solution is 1~15%, the concentration of bismuth chloride solution is 0.1~1.0 M, and the concentration of polyvinylpyrrolidone solution is 5~40 mg·mL. -1 ; Optionally, the ratio of the amount of silk fabric, hydrochloric acid solution, 3-aminopropyltriethoxysilane solution and mixed solution is 1~2g: 20~60 mL: 10~40 mL: 12~40 mL; Optionally, the silk fabric is immersed in hydrochloric acid solution for 0.5-3 h, in 3-aminopropyltriethoxysilane solution for 8-72 h, or in a mixed solution of bismuth chloride and polyvinylpyrrolidone for 8-72 h. Optionally, the silk fabric is impregnated in hydrochloric acid solution at a temperature of 20-30°C, in 3-aminopropyltriethoxysilane solution at a temperature of 20-30°C, or in a mixed solution of bismuth chloride and polyvinylpyrrolidone at a temperature of 20-30°C.

10. The method according to claim 7, characterized in that, In step (3), the ratio of bismuth-loaded silk fabric to sodium phosphite monohydrate solution is 1~2 g: 80~120 mL; Optionally, the concentration of the sodium hypophosphite monohydrate solution is 0.1~2.0 M; Optionally, the reduction temperature is 30~90 ℃; Optionally, the restoration time is 1 to 5 hours; Optionally, in step (4), calcination is carried out by raising the temperature from room temperature to 600~950 °C under an inert atmosphere. Optionally, the heating rate is 1~5 ℃ / min; Optionally, the heat preservation time is 1 to 4 hours.

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