Preparation method of graphene strip modified bismuth-based composite negative electrode material and electrochemical energy storage application of graphene strip modified bismuth-based composite negative electrode material
The preparation of graphene strip-modified bismuth-based composite materials by spray-freezing technology solves the problems of limited electron transport paths and insufficient structural stability of bismuth-based anode materials, achieving high specific capacitance and good cycle stability, and improving the energy storage performance of supercapacitors.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA UNIV OF PETROLEUM (EAST CHINA)
- Filing Date
- 2026-03-19
- Publication Date
- 2026-05-12
AI Technical Summary
Existing bismuth-based anode materials suffer from limited electron transport paths, easy aggregation of active materials, and insufficient stability of conductive structures, resulting in low utilization of active sites and affecting their electrochemical performance.
Graphene strips were prepared using a spray-freeze technique and then ultrasonically dispersed with a bismuth source in ethanol before undergoing a solvothermal reaction to form a bismuth-based composite material modified with graphene strips. By constructing a stable electron transport pathway, the structural stability and electrochemical performance of the material were improved.
It significantly improves the specific capacitance and cycle stability of bismuth-based composite materials, enhances the electrochemical reaction efficiency and structural stability of the materials, and improves the energy storage performance of supercapacitors.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of electrochemical energy storage materials technology, specifically to a method for preparing a graphene strip-modified bismuth-based composite anode material and its electrochemical energy storage application. Background Technology
[0002] Supercapacitors are important electrochemical energy storage devices with advantages such as high power density, fast charge / discharge speed, and long cycle life, showing broad application prospects in new energy vehicles, smart grids, and portable electronic devices. However, compared with traditional electrochemical batteries, their energy density is still relatively low, especially with the development of high-capacity, high-rate anode materials being particularly crucial. Currently, carbon materials, due to their large specific surface area and good conductivity, exhibit good rate performance and stability as energy storage anode materials, and have gained initial market recognition and promotion. However, their energy storage mechanism mainly relies on electric double-layer capacitance, resulting in relatively low specific capacity, which cannot overcome the bottleneck of low energy density in supercapacitors.
[0003] To further improve the energy storage performance of anodes, researchers are increasingly introducing bismuth-based materials with reversible redox reaction characteristics into electrode systems. Existing technologies typically improve the electrochemical performance of bismuth-based materials by constructing conductive carbon-based composite structures. For example, patent CN113258025A discloses a high-performance bismuth-based anode for aqueous batteries, which improves the cycle stability and specific capacity of the electrode by growing bismuth-based nanostructures on a porous conductive carbon substrate to form a self-supporting electrode. Patent CN114784256B discloses a bismuth-based composite anode material that improves the rate performance and cycle stability of the material by using a carbon-coated bismuth nanoparticle structure. Furthermore, patent CN118782394A improves the conductivity and energy storage performance of the material by constructing a Bi₂O₃ / Bi₂S₃ heterocomposite structure and introducing conductive carbon materials.
[0004] While the aforementioned technologies have improved the electrochemical performance of bismuth-based materials to some extent, problems such as limited electron transport pathways, easy aggregation of active materials, and insufficient stability of conductive structures still exist, resulting in low utilization of active sites. Therefore, it is still necessary to further develop bismuth-based anode materials that can construct stable electron transport pathways and improve electrochemical reaction efficiency. Summary of the Invention
[0005] To address the problems of poor electrical conductivity and insufficient structural stability during cycling in existing bismuth-based materials, this invention provides a graphene strip-modified bismuth-based composite material, its preparation method, and its applications. The preparation method includes the following steps: Graphene oxide was stripped using a spray-freeze technique to obtain graphene strips. The graphene strips and bismuth source were ultrasonically dispersed and stirred in ethanol and then subjected to a solvothermal reaction. After the reaction was completed, the graphene strips were filtered, washed and vacuum dried to obtain a bismuth-based composite material modified with graphene strips.
[0006] Furthermore, the bismuth source is one or more of bismuth nitrate, bismuth chloride, and bismuth acetate.
[0007] Furthermore, the mass fraction of the graphene strip is 5% to 20%.
[0008] Furthermore, the temperature of the solvothermal reaction is 180~220℃, and the reaction time is 12~48 h.
[0009] Furthermore, the vacuum drying temperature is 80°C, and the vacuum drying time is 12 hours.
[0010] The present invention also discloses a graphene strip modified bismuth-based composite material prepared by the above-described preparation method.
[0011] This invention also discloses a method for preparing a supercapacitor negative electrode material, comprising: The graphene strip-modified bismuth-based composite material, conductive acetylene black, and PTFE binder are mixed in a solvent to form a slurry. The slurry is then coated onto the surface of a conductive substrate and pressed into a sheet to obtain a supercapacitor negative electrode material.
[0012] Preferably, the conductive substrate is nickel foam; and the solvent is anhydrous ethanol.
[0013] Compared with the prior art, the present invention has the following beneficial effects: The method for preparing graphene-modified bismuth-based composite materials provided by this invention is simple to operate and uses readily available raw materials. By introducing graphene strips, the structural stability of bismuth-based materials can be improved to a certain extent, and the electrochemical performance of the anode material can be enhanced. Test results show that the prepared composite material has high specific capacitance and good cycle stability. Attached Figure Description
[0014] Figure 1 This is a scanning electron microscope image of Embodiment 1 of the present invention; Figure 2 This is a scanning electron microscope image of Embodiment 2 of the present invention; Figure 3 The X-ray diffraction patterns are those of Embodiments 1 and 2 of the present invention; Figure 4 This is a cyclic voltammetry curve of Embodiment 1 of the present invention in a three-electrode system; Figure 5This is a constant current charge-discharge curve of Embodiment 1 of the present invention in a three-electrode system; Figure 6 These are constant current charge-discharge curves of Embodiments 1-8 of the present invention in a three-electrode system; Figure 7 These are the magnification diagrams of Embodiments 1-8 of the present invention in a three-electrode system; Figure 8 The diagram shows the cycle life of Embodiments 1 and 2 of the present invention in a three-electrode system; Figure 9 This is an electrode matching diagram of the asymmetric supercapacitor assembled with Ni(OH)2 positive electrode in Embodiment 1 of the present invention; Figure 10 This is a cyclic voltammetry curve of the asymmetric supercapacitor assembled with Ni(OH)2 in Example 1 of the present invention in a three-electrode system; Figure 11 This is a constant current charge-discharge curve of the asymmetric supercapacitor assembled with Ni(OH)2 in Example 1 of the present invention in a three-electrode system. Detailed Implementation
[0015] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0016] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings: Example
[0017] Preparation of bismuth-based composite materials modified with graphene strips: Graphene oxide was prepared using a modified Hummers method, centrifuged, and then used for subsequent preparation of graphene strips via a "spray-freeze" strategy. All graphene strips mentioned below were prepared using this method. A 10% (w / w) graphene strip was added to 5 ml of ethanol and ultrasonically dispersed for 2 h. 0.5 mmol of bismuth nitrate pentahydrate was added, and ultrasonic dispersion continued for 30 min. The mixture was stirred at room temperature for 30 min until homogeneous. The mixture was then transferred to a polytetrafluoroethylene-lined reactor and subjected to a solvothermal reaction at 200 °C for 48 h. After the reaction, the mixture was naturally cooled to room temperature, and the resulting product was filtered under reduced pressure and vacuum dried at 80 °C for 12 h to obtain the composite material. Example
[0018] Add 0.5 mmol of bismuth nitrate pentahydrate to 5 ml of ethanol, sonicate for 30 min, and stir at room temperature for 30 min to mix evenly. Transfer the resulting mixture to a polytetrafluoroethylene-lined reactor and carry out a solvothermal reaction at 200 °C for 48 h. After the reaction is completed, allow it to cool naturally to room temperature, filter the product under reduced pressure, and dry it under vacuum at 80 °C for 12 h to obtain the bismuth-based material. Example
[0019] Preparation of bismuth-based composite material modified with graphene strips: 5% by mass of graphene strips were added to 5 ml of ethanol and ultrasonically dispersed for 2 h. 0.5 mmol of bismuth nitrate pentahydrate was added and ultrasonically dispersed for another 30 min. The mixture was stirred at room temperature for 30 min to mix evenly. The mixture was transferred to a polytetrafluoroethylene-lined reactor and subjected to a solvothermal reaction at 220℃ for 24 h. After the reaction was completed, the mixture was naturally cooled to room temperature. The obtained product was filtered under reduced pressure and vacuum dried at 80℃ for 12 h to obtain the composite material. Example
[0020] Preparation of bismuth-based composite material modified with graphene strips: 20% graphene strips were added to 5 ml of ethanol and ultrasonically dispersed for 2 h. 0.5 mmol of bismuth nitrate pentahydrate was added and ultrasonically dispersed for another 30 min. The mixture was stirred at room temperature for 30 min to mix evenly. The mixture was transferred to a polytetrafluoroethylene-lined reactor and subjected to a solvothermal reaction at 220 °C for 12 h. After the reaction was completed, the mixture was naturally cooled to room temperature. The product was filtered under reduced pressure and vacuum dried at 80 °C for 12 h to obtain the composite material. Example
[0021] Preparation of bismuth-based composite material modified with graphene strips: 10% graphene strips were added to 5 ml of ethanol / water mixed solution (ethanol to water volume ratio 1:1), and ultrasonically dispersed for 2 h. 0.5 mmol of bismuth nitrate pentahydrate was added, and ultrasonic dispersion was continued for 30 min. The mixture was stirred at room temperature for 30 min to achieve homogeneity. The mixture was then transferred to a polytetrafluoroethylene-lined reactor and subjected to a solvothermal reaction at 200 °C for 48 h. After the reaction, the mixture was naturally cooled to room temperature, and the resulting product was filtered under reduced pressure and vacuum dried at 80 °C for 12 h to obtain the composite material. Example
[0022] Preparation of bismuth-based composite material modified with graphene strips: 5% (w / w) graphene strips were added to 5 ml of a mixed solution of ethanol and ethylene glycol (volume ratio of ethanol to ethylene glycol: 1:1). The mixture was ultrasonically dispersed for 2 h, then 0.5 mmol of bismuth chloride was added, and the mixture was ultrasonically dispersed for another 30 min. The mixture was stirred at room temperature for 30 min until homogeneous. The mixture was then transferred to a polytetrafluoroethylene-lined reactor and subjected to a solvothermal reaction at 200 °C for 48 h. After the reaction was completed, the mixture was naturally cooled to room temperature. The resulting product was filtered under reduced pressure and then vacuum dried at 80 °C for 12 h to obtain the composite material. Example
[0023] Add 0.5 mmol of bismuth chloride to 5 ml of ethanol, sonicate for 30 min, and stir at room temperature for 30 min to mix evenly. Transfer the resulting mixture to a polytetrafluoroethylene-lined reactor and carry out a solvothermal reaction at 200 °C for 48 h. After the reaction is completed, allow it to cool naturally to room temperature, filter the product under reduced pressure, and dry it under vacuum at 80 °C for 12 h to obtain the bismuth-based material. Example
[0024] Add 0.5 mmol of bismuth acetate to 5 ml of ethanol, sonicate for 30 min, and stir at room temperature for 30 min to mix evenly. Transfer the resulting mixture to a polytetrafluoroethylene-lined reactor and carry out a solvothermal reaction at 200 °C for 48 h. After the reaction is completed, allow it to cool naturally to room temperature, filter the product under reduced pressure, and dry it under vacuum at 80 °C for 12 h to obtain the bismuth-based material.
[0025] The electrochemical performance tests for each embodiment were conducted using the following methods: The resulting composite material was used to prepare a negative electrode material, with a mass ratio of active material, conductive agent, and binder of 80:10:10 and a loading of 1~3 mg cm⁻¹. -2 Examples 1-5 used nickel foam as the current collector, Examples 6 and 7 used stainless steel mesh as the current collector, and Example 8 used stainless steel mesh as the current collector. Electrochemical performance was tested using a three-electrode system with Hg / HgO electrode as reference electrode, platinum sheet as counter electrode, and 6 M KOH solution as electrolyte. Cyclic voltammetry and constant current charge-discharge tests were performed respectively.
[0026] Figure 1 and Figure 2 The images shown are scanning electron microscope (SEM) images of Embodiments 1 and 2 of the present invention, respectively. Figure 1The tightly packed composite structure of graphene strips and bismuth-based nanoparticles is clearly demonstrated. The material obtained in Example 2 consists of nanosheets and nanospheres, wherein the nanosheets are cross-linked to form a network structure, and the nanospheres are approximately 200 nm in diameter and uniformly distributed on the surface of the nanosheets. In contrast, after adding graphene strips in Example 1, the nanospheres are distributed between the graphene strip layers and are more uniformly distributed.
[0027] Figure 3 These are the XRD patterns of Embodiments 1 and 2 of the present invention. Figure 3 It can be seen that in the sample without graphene strips, the diffraction peaks correspond to the characteristic diffraction peaks of metallic bismuth and basic bismuth carbonate, respectively, indicating that a bismuth-based composite structure has been formed in the sample. After the introduction of graphene strips, the characteristic diffraction peaks of metallic bismuth and basic bismuth carbonate can still be observed in the XRD pattern of the composite material, and no obvious new impurity phase diffraction peaks were detected, indicating that the introduction of graphene strips did not change the main phase composition of the material. At the same time, compared with the sample without graphene strips, the relative intensity and peak shape of some diffraction peaks changed to a certain extent, indicating that the introduction of graphene strips affected the crystal structure of the material to some extent.
[0028] like Figure 4 and Figure 5 As shown, the negative electrode material obtained in Example 1 exhibits significant redox characteristics in cyclic voltammetry testing and a long discharge time in constant current charge-discharge testing. Test results indicate that this material has a discharge time of 1 A g. -1 The specific capacitance at current density is 1400–1500 F g -1 , at 50 A g -1 It can still maintain about 800 F g at current density -1 Combining Figure 7 It can be seen that, compared with Example 1, the discharge time of the constant current charge-discharge curves of the negative electrode materials in Examples 2-8 is shortened by about 30% to 50%, and their energy storage performance is significantly reduced. For example... Figure 8 As shown, the anode material prepared in Example 1 retained approximately 90% of its initial specific capacitance after 5000 cycles; in contrast, the anode material prepared in Example 2 retained only approximately 60% of its initial specific capacitance after 4000 cycles. Its cycle stability is significantly worse than that of the graphene strip-modified bismuth-based composite material. Furthermore, the anode materials prepared in Examples 7 and 8 using different bismuth sources retained only 60.8% and 40% of their initial capacity, respectively, after 1000 cycles, with capacity decay rates higher than those of Examples 1 and 2. These results indicate that the introduction of graphene strips helps improve the structural stability of the material, thereby enhancing cycle performance; simultaneously, the type of bismuth source also has a significant impact on the cycle stability of the composite material.
[0029] like Figure 9-11As shown, an asymmetric supercapacitor device was assembled using the graphene strip-modified bismuth-based composite material prepared in Example 1 as the negative electrode, Ni(OH)2 as the positive electrode, and 6 M KOH as the electrolyte. The device has an operating voltage window of up to 1.5V, and calculations based on the constant current charge-discharge curves show that the device exhibits excellent rate performance.
[0030] The results from Examples 1 to 8 show that the introduction of graphene strips, the solvothermal reaction temperature, and the reaction time all have a certain impact on the structure and electrochemical performance of the bismuth-based composite material. Specifically, when the mass fraction of graphene strips is 10%, the solvothermal reaction temperature is 200℃, and the reaction time is 48 h, the resulting composite material exhibits better electrochemical energy storage performance.
[0031] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.
Claims
1. A method for preparing a graphene strip-modified bismuth-based composite material, characterized in that, The specific preparation steps are as follows: Graphene strips are dispersed in a solvent to obtain a dispersion; a bismuth source is added to the dispersion, and after mixing evenly, a solvothermal reaction is carried out; after the reaction is completed, the obtained product is filtered and dried under vacuum to obtain a bismuth-based composite material modified with graphene strips.
2. The preparation method according to claim 1, characterized in that, The graphene strips were obtained by spraying and freezing graphene oxide and then drying it. The graphene oxide was prepared by a modified Hummers method. The specific preparation scheme is as follows: graphite and concentrated sulfuric acid were mixed under ice bath conditions, potassium permanganate was added to carry out the oxidation reaction, deionized water and hydrogen peroxide were added to terminate the reaction after the reaction was completed, the mixture was centrifuged and washed until neutral and dried to obtain graphene oxide. The graphene oxide dispersion was sprayed into liquid nitrogen through a spraying device for rapid freezing, and then freeze-dried to obtain graphene strips.
3. The preparation method according to claim 1, characterized in that, The bismuth source is one or more of bismuth nitrate, bismuth chloride, and bismuth acetate.
4. The preparation method according to claim 1, characterized in that, The mass ratio of the bismuth source to the graphene strip is 4:1 to 20:
1.
5. The preparation method according to claim 1, characterized in that, The solvothermal reaction temperature is 180-220℃, and the reaction time is 12-48 h.
6. The preparation method according to claim 1, characterized in that, The solvent used is ethanol, water, ethylene glycol, or a mixture thereof.
7. A method for preparing a negative electrode material for a supercapacitor, characterized in that, The method includes the following steps: dispersing the graphene strip-modified bismuth-based composite material, conductive agent, and binder obtained by the method of claim 1 in ethanol to prepare an electrode slurry; coating the electrode slurry onto the surface of a conductive substrate; and obtaining a supercapacitor negative electrode material after drying and pressing.
8. The preparation method according to claim 7, characterized in that, The conductive substrate is nickel foam, carbon cloth, or stainless steel mesh.