Graphene pseudocapacitor electrode material based on expansion-oxidation strategy modification and preparation method and application thereof

Abstract

The invention belongs to the field of supercapacitors, and discloses a graphene pseudocapacitor electrode material based on expansion-oxidation strategy modification and a preparation method and application thereof, and the preparation method comprises the steps: carrying out the flame heating of a graphene oxide film under a normal pressure condition, inducing the expansion and reduction reaction of the graphene oxide film, and obtaining expanded graphene; adding the expanded graphene into a mixed acid solution, and stirring for oxidation reaction to obtain expanded-oxidized graphene; mixing the expanded-oxidized graphene, the electrically exfoliated graphene and bacterial cellulose, and performing vacuum-assisted suction filtration treatment to obtain a graphene pseudocapacitor electrode material modified based on an expanded-oxidized strategy; according to the preparation method, physical expansion and chemical oxidation are combined to prepare expanded-oxidized graphene, so that the electron conduction capability and the ion migration rate of the electrode material are synergistically improved, and the graphene pseudocapacitance electrode material with flexibility, high specific surface area, abundant pseudocapacitance active sites and stable double-electrode-layer capacitance characteristics is prepared.

Description

Technical Field

[0001] This invention belongs to the field of supercapacitor technology, and specifically relates to a graphene pseudocapacitive electrode material modified by an expansion-oxidation strategy, its preparation method, and its application. Background Technology

[0002] Supercapacitors, as a novel energy storage device, have attracted widespread attention in the field of energy storage due to their advantages such as high power density, long lifespan, rapid charging and discharging, and zero pollution. However, their disadvantages, such as low energy density, large size, and unstable long-term power supply, limit their use in some long-term energy storage and high-energy-demand applications. Therefore, developing electrode materials with higher energy density, optimizing their structure, and constructing more stable and durable electrode materials are key to improving the performance of supercapacitors and promoting their widespread application.

[0003] Currently, graphene is considered an ideal electrode material due to its high theoretical specific surface area and excellent conductivity. However, existing graphene-based electrode materials generally suffer from problems such as easy agglomeration, low effective specific surface area, and limited pseudocapacitive contribution. Specifically, in practical applications, the energy density is limited mainly due to the reliance on the double-layer energy storage mechanism. Secondly, the strong π-π interactions between graphene sheets easily lead to irreversible stacking and agglomeration, resulting in a significant decrease in effective specific surface area and an extension of ion transport paths. This not only reduces the conductivity of the material but also makes the actual specific capacitance far lower than theoretically expected. In addition, although heteroatom doping (such as nitrogen doping) or composite metal oxides can partially improve pseudocapacitive performance, the process is often complex and costly, and it is difficult to precisely control the type and distribution of surface functional groups, resulting in low efficiency of pseudocapacitive active sites. Summary of the Invention

[0004] To address the technical problems existing in the prior art, this invention provides a graphene pseudocapacitive electrode material modified by an expansion-oxidation strategy, its preparation method, and its application, in order to solve the technical problems that existing graphene-based electrode materials generally suffer from, such as easy agglomeration, low effective specific surface area, and limited pseudocapacitive contribution.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a method for preparing a graphene pseudocapacitive electrode material modified by an expansion-oxidation strategy, comprising: Under normal pressure, graphene oxide film is heated by flame to induce expansion and reduction reactions in the graphene oxide film, thus obtaining expanded graphene. Expanded graphene was added to a mixed acid solution and stirred to carry out an oxidation reaction, yielding expanded-oxidized graphene. Expanded-oxidized graphene, electroexfoliated graphene, and bacterial cellulose were mixed and subjected to vacuum-assisted filtration to obtain a graphene pseudocapacitive electrode material modified based on an expansion-oxidation strategy.

[0006] Furthermore, the preparation process of the graphene oxide film is as follows: Water is added to graphene oxide and stirred until a dough-like consistency is formed, resulting in graphene oxide dough; the water content of the graphene oxide dough is 3%-8%; The graphene oxide dough was cold-pressed to obtain a graphene oxide film.

[0007] Furthermore, in the process of cold pressing the graphene oxide dough to obtain a graphene oxide film, the cold pressing pressure is 8-10 MPa and the cold pressing time is 8-10 min.

[0008] Furthermore, under normal pressure, the graphene oxide film is heated by flame to induce expansion and reduction reactions in the graphene oxide film to obtain expanded graphene. The flame heating temperature is 200-400℃ and the heating time is 5-8 minutes.

[0009] Furthermore, the mixed acid solution is a mixture of concentrated sulfuric acid, concentrated nitric acid and water; wherein the volume ratio of concentrated sulfuric acid to concentrated nitric acid is 3:1; and the volume ratio of the sum of the volumes of concentrated sulfuric acid and concentrated nitric acid to the volume of water in the mixed acid solution is (16-100):(0-84).

[0010] Furthermore, after adding expanded graphene to the mixed acid solution, the mass percentage of expanded graphene in the mixed acid solution is 2-5 wt%.

[0011] Furthermore, expanded graphene is added to a mixed acid solution and stirred to carry out an oxidation reaction to obtain expanded-oxidized graphene. During this process, the oxidation reaction temperature is 0-40℃ and the oxidation reaction time is 6-12h.

[0012] Furthermore, in the raw materials of the graphene pseudocapacitive electrode material modified by the expansion-oxidation strategy, the mass ratio of expanded-oxidized graphene, electroexfoliated graphene and bacterial cellulose is (30-45):10:15.

[0013] The present invention also provides a graphene pseudocapacitive electrode material modified by an expansion-oxidation strategy, which is prepared using the preparation method of the graphene pseudocapacitive electrode material modified by the expansion-oxidation strategy.

[0014] The present invention also provides an application of a graphene pseudocapacitive electrode material modified by an expansion-oxidation strategy, wherein the graphene pseudocapacitive electrode material modified by the expansion-oxidation strategy is used in a supercapacitor.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a method for preparing graphene pseudocapacitive electrode materials based on an expansion-oxidation strategy. The method combines physical expansion and chemical oxidation to prepare expanded-oxidized graphene. This expanded-oxidized graphene is then composited with electrically exfoliated graphene (which exhibits excellent conductivity) and high-strength bacterial cellulose to construct a three-dimensional porous interconnected conductive network. This synergistically enhances the electronic conductivity and ion migration rate of the electrode material, resulting in a flexible graphene pseudocapacitive electrode material with a high specific surface area, abundant pseudocapacitive active sites, and stable double-layer capacitance characteristics. Specifically, the method first induces an expansion and reduction reaction in the graphene oxide film under ambient pressure via flame heating. Simultaneous expansion and partial reduction under ambient pressure effectively overcome the challenge of graphene sheet stacking, significantly increasing the specific surface area and forming a hierarchical porous structure. Secondly, a mixed acid controlled oxidation technique is used to precisely oxidize the expanded graphene, selectively optimizing the type and distribution of oxygen-containing functional groups on the surface, enriching carboxyl groups (-COOH) with higher pseudocapacitive activity, while inhibiting the excessive generation of hydroxyl groups (-OH), thereby significantly enhancing the Faraday pseudocapacitive contribution of the material. Finally, by combining the obtained expanded-oxidized graphene with electroexfoliated graphene and bacterial cellulose flexibility, a three-dimensional porous interconnected conductive network is constructed, synergistically improving the electronic conductivity and ion migration rate of the electrode material.

[0016] The graphene pseudocapacitive electrode material and its application based on the expansion-oxidation strategy modification provided by this invention possess all the advantages of the above-mentioned preparation method of graphene pseudocapacitive electrode material based on the expansion-oxidation strategy modification. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 SEM images of expanded graphene and expanded-oxidized graphene are shown; among them, Figure 1 a is the SEM image of the expanded graphene in the comparative example; Figure 1 b is a SEM image of the expanded-oxidized graphene in Example 5; Figure 2 Optical photographs of graphene oxide, expanded graphene, and expanded-oxidized graphene in Example 5; wherein, Figure 2 The image on the left is an optical photograph of graphene oxide. Figure 2The image in the middle is an optical photograph of expanded graphene. Figure 2 The image on the right is an optical photograph of expanded-oxidized graphene. Figure 3 The graph shows the relationship between the specific capacitance of the graphene composite film material prepared in the comparative example and the current density. Figure 4 The graph shows the relationship between the specific capacitance and current density of the graphene pseudocapacitive electrode materials modified by the expansion-oxidation strategy prepared in Examples 1-6. Figure 5 The image shows the CV curves of the graphene pseudocapacitive electrode material modified by the expansion-oxidation strategy prepared in Example 5 at different scan rates. Figure 6 The infrared spectra of the graphene composite film material prepared in the comparative examples and the graphene pseudocapacitive electrode materials modified by the expansion-oxidation strategy prepared in Examples 1-6 are shown. Detailed Implementation

[0019] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0020] This invention provides a method for preparing a graphene pseudocapacitive electrode material modified based on an expansion-oxidation strategy, comprising the following steps: Step 1: Add water to the graphene oxide and stir until a dough-like consistency is formed, resulting in graphene oxide dough. The water content of the graphene oxide dough is 3%-8%.

[0021] Step 2: Cold press the graphene oxide dough to obtain a graphene oxide film. The cold pressing pressure is 8-10 MPa, and the cold pressing time is 8-10 min.

[0022] Step 3: Under normal pressure, the graphene oxide film is heated by flame to induce expansion and reduction reactions, yielding expanded graphene. The flame heating temperature is 200-400℃, and the heating time is 5-8 minutes.

[0023] Step 4: Add expanded graphene to a mixed acid solution and stir to carry out an oxidation reaction to obtain expanded-oxidized graphene. The mixed acid solution is a mixture of concentrated sulfuric acid, concentrated nitric acid, and water; preferably, the volume ratio of concentrated sulfuric acid to concentrated nitric acid is 3:1; the volume ratio of the sum of the volumes of concentrated sulfuric acid and concentrated nitric acid to the volume of water in the mixed acid solution is (16-100):(0-84); after adding expanded graphene to the mixed acid solution, the mass percentage of expanded graphene in the mixed acid solution is 2-5 wt%; the oxidation reaction temperature is 0-40℃, and the oxidation reaction time is 6-12 h.

[0024] Step 5: Mix expanded-oxidized graphene, electroexfoliated graphene, and bacterial cellulose, and then perform vacuum-assisted filtration to obtain graphene pseudocapacitive electrode material modified based on the expanded-oxidation strategy. The mass ratio of expanded-oxidized graphene, electroexfoliated graphene, and bacterial cellulose is (30-45):10:15.

[0025] Preparation principle: The method for preparing graphene pseudocapacitive electrode materials based on an expansion-oxidation strategy described in this invention induces the instantaneous expansion of the graphene oxide film by flame heating under ambient pressure, achieving simultaneous expansion and partial reduction under ambient pressure. This effectively overcomes the problem of graphene sheet stacking, significantly increases the specific surface area, and forms a hierarchical porous structure. Subsequently, a mixed acid controlled oxidation technique is used, i.e., a concentrated sulfuric acid / concentrated nitric acid system is used to precisely oxidize the expanded graphene, enriching the carboxyl groups (-COOH) with higher pseudocapacitive activity, while inhibiting the excessive generation of hydroxyl groups (-OH), thus obtaining expanded-oxidized graphene. The study involved the selective optimization of the type and distribution of oxygen-containing functional groups on the surface of graphene by precisely controlling the acid concentration, reaction temperature, and time. This significantly increased the -COOH / -OH ratio to 2:1, thereby significantly enhancing the Faraday pseudocapacitive contribution of the material. Finally, by combining expanded-oxidized graphene with electroexfoliated graphene and bacterial cellulose, a three-dimensional porous interconnected conductive network was constructed. This synergistically improved the electronic conductivity and ion migration rate of the electrode material, resulting in a flexible graphene pseudocapacitive electrode material with high specific surface area, abundant pseudocapacitive active sites, and stable double-layer capacitance characteristics.

[0026] Of particular note is that this invention abandons traditional high-temperature inert atmosphere reduction expansion or complex hydrothermal / solvothermal methods, organically combining physical expansion with chemical oxidation. It utilizes flame heating to instantly vaporize the interlayer moisture in graphene oxide, achieving simultaneous expansion and reduction under normal pressure, effectively overcoming the challenge of graphene sheet stacking. Subsequently, a mixed acid system of concentrated sulfuric acid / concentrated nitric acid is used to precisely oxidize the expanded graphene, controlling the relative content of -COOH and -OH in the oxygen-containing functional groups, making its surface rich in more -COOH functional groups with higher pseudocapacitive activity, thereby significantly enhancing the Faraday pseudocapacitive contribution of the material. Furthermore, by combining the obtained expanded graphene with highly conductive electroexfoliated graphene and a high-strength bacterial cellulose flexible matrix, a three-dimensional porous interconnected conductive network is constructed, improving the electron conductivity and ion migration rate of the electrode.

[0027] The graphene pseudocapacitive electrode material prepared by this invention has high specific surface area, abundant pseudocapacitive active sites, and stable double-layer capacitance characteristics. Among them, the high specific surface area can effectively alleviate the surface area loss caused by agglomeration, and the high density of -COOH functional groups enhances the abundance of pseudocapacitive active sites, realizing the efficient synergy of the two energy storage mechanisms of double-layer capacitance and pseudocapacitance.

[0028] In this invention, high-energy-density graphene electrode materials were prepared through a simple process involving high-temperature rapid vaporization and expansion of water molecules, oxidation treatment, and vacuum-assisted filtration. Graphene pseudocapacitive electrode materials with different electrochemical properties can be obtained by controlling the oxidation time and temperature, and can be applied to supercapacitors to improve their performance. The preparation process is simple and efficient, the reaction conditions are mild, energy consumption is significantly reduced, and the raw materials are readily available, demonstrating great potential for large-scale production and industrial application.

[0029] The following specific embodiments further explain the preparation method of the graphene pseudocapacitive electrode material based on the expansion-oxidation strategy provided by the present invention: Example 1 This embodiment 1 provides a method for preparing a graphene pseudocapacitive electrode material modified based on an expansion-oxidation strategy, including the following steps: Step 1: Add 1 mL of deionized water to 100 mg of graphene oxide and stir to promote water evaporation until a dough is formed, thus obtaining graphene oxide dough; wherein, the water content of the graphene oxide dough is 3%.

[0030] Step 2: Place the graphene oxide dough between two polytetrafluoroethylene films and transfer it to a flatbed cold press for cold pressing to obtain a graphene oxide film; wherein, the cold pressing pressure is 8MPa and the cold pressing time is 8min.

[0031] Step 3: Place the graphene oxide film in an open aluminum container and heat the bottom of the container with an alcohol lamp to evaporate the water molecules in the graphene oxide film, thereby inducing the graphene oxide film to expand and undergo a reduction reaction to obtain expanded graphene; wherein, the flame heating temperature is 200℃ and the heating time is 8min.

[0032] Step 4: Add expanded graphene to a mixed acid solution and stir at 0°C for 6 hours to obtain expanded-oxidized graphene. The mixed acid solution is a mixture of concentrated sulfuric acid, concentrated nitric acid, and water. The volume ratio of concentrated sulfuric acid to concentrated nitric acid is 3:1. The volume ratio of the sum of the volumes of concentrated sulfuric acid and concentrated nitric acid to water in the mixed acid solution is 16:84. After adding expanded graphene to the mixed acid solution, the mass percentage of expanded graphene in the mixed acid solution is 2 wt%.

[0033] Step 5: Mix expanded-oxidized graphene, electroexfoliated graphene, and bacterial cellulose in a mass ratio of 40:10:15, and prepare a graphene pseudocapacitive electrode material modified by an expanded-oxidation strategy using vacuum-assisted filtration technology.

[0034] Example 2 This embodiment 2 provides a method for preparing a graphene pseudocapacitive electrode material modified based on an expansion-oxidation strategy, including the following steps: Step 1: Add 1 mL of deionized water to 100 mg of graphene oxide and stir to promote water evaporation until a dough is formed, thus obtaining graphene oxide dough; wherein, the water content of the graphene oxide dough is 8%.

[0035] Step 2: Place the graphene oxide dough between two polytetrafluoroethylene films and transfer it to a flatbed cold press for cold pressing to obtain a graphene oxide film; wherein, the cold pressing pressure is 9 MPa and the cold pressing time is 9 min.

[0036] Step 3: Place the graphene oxide film in an open aluminum container and heat the bottom of the container with an alcohol lamp to evaporate the water molecules in the graphene oxide film, thereby inducing the graphene oxide film to expand and undergo a reduction reaction to obtain expanded graphene; wherein, the flame heating temperature is 300℃ and the heating time is 8min.

[0037] Step 4: Add expanded graphene to a mixed acid solution and stir at 0°C for 6 hours to obtain expanded-oxidized graphene. The mixed acid solution is a mixture of concentrated sulfuric acid, concentrated nitric acid, and water. The volume ratio of concentrated sulfuric acid to concentrated nitric acid is 3:1. The volume ratio of the sum of the volumes of concentrated sulfuric acid and concentrated nitric acid to water in the mixed acid solution is 32:68. After adding expanded graphene to the mixed acid solution, the mass percentage of expanded graphene in the mixed acid solution is 3 wt%.

[0038] Step 5: Mix expanded-oxidized graphene, electroexfoliated graphene, and bacterial cellulose in a mass ratio of 42:10:15, and prepare a graphene pseudocapacitive electrode material modified by an expanded-oxidation strategy using vacuum-assisted filtration technology.

[0039] Example 3 This embodiment 3 provides a method for preparing a graphene pseudocapacitive electrode material modified based on an expansion-oxidation strategy, including the following steps: Step 1: Add 1 mL of deionized water to 100 mg of graphene oxide and stir to promote water evaporation until a dough is formed, thus obtaining graphene oxide dough; wherein, the water content of the graphene oxide dough is 8%.

[0040] Step 2: Place the graphene oxide dough between two polytetrafluoroethylene films and transfer it to a flatbed cold press for cold pressing to obtain a graphene oxide film; wherein, the cold pressing pressure is 10MPa and the cold pressing time is 10min.

[0041] Step 3: Place the graphene oxide film in an open aluminum container and heat the bottom of the container with an alcohol lamp to evaporate the water molecules in the graphene oxide film, thereby inducing the graphene oxide film to expand and undergo a reduction reaction to obtain expanded graphene; wherein, the flame heating temperature is 300℃ and the heating time is 5min.

[0042] Step 4: Add expanded graphene to a mixed acid solution and stir at 0°C for 6 hours to obtain expanded-oxidized graphene. The mixed acid solution is a mixture of concentrated sulfuric acid, concentrated nitric acid, and water. The volume ratio of concentrated sulfuric acid to concentrated nitric acid is 3:1. The volume ratio of the sum of the volumes of concentrated sulfuric acid and concentrated nitric acid to water in the mixed acid solution is 64:32. After adding expanded graphene to the mixed acid solution, the mass percentage of expanded graphene in the mixed acid solution is 4 wt%.

[0043] Step 5: Mix expanded-oxidized graphene, electroexfoliated graphene, and bacterial cellulose in a mass ratio of 45:10:15, and prepare a graphene pseudocapacitive electrode material modified by an expanded-oxidation strategy using vacuum-assisted filtration technology.

[0044] Example 4 This embodiment 4 provides a method for preparing a graphene pseudocapacitive electrode material modified based on an expansion-oxidation strategy, including the following steps: Step 1: Add 1 mL of deionized water to 100 mg of graphene oxide and stir to promote water evaporation until a dough is formed, thus obtaining graphene oxide dough; wherein, the water content of the graphene oxide dough is 5%.

[0045] Step 2: Place the graphene oxide dough between two polytetrafluoroethylene films and transfer it to a flatbed cold press for cold pressing to obtain a graphene oxide film; wherein, the cold pressing pressure is 8MPa and the cold pressing time is 10min.

[0046] Step 3: Place the graphene oxide film in an open aluminum container and heat the bottom of the container with an alcohol lamp to evaporate the water molecules in the graphene oxide film, thereby inducing the graphene oxide film to expand and undergo a reduction reaction to obtain expanded graphene; wherein, the flame heating temperature is 300℃ and the heating time is 8min.

[0047] Step 4: Add expanded graphene to the mixed acid solution and stir at 0°C for 6 hours to obtain expanded-oxidized graphene. The mixed acid solution is a mixture of concentrated sulfuric acid, concentrated nitric acid and water. The volume ratio of concentrated sulfuric acid to concentrated nitric acid is 3:1. The volume ratio of the sum of the volumes of concentrated sulfuric acid and concentrated nitric acid to water in the mixed acid solution is 85:15. After adding expanded graphene to the mixed acid solution, the mass percentage of expanded graphene in the mixed acid solution is 5 wt%.

[0048] Step 5: Mix expanded-oxidized graphene, electroexfoliated graphene, and bacterial cellulose in a mass ratio of 41:10:15, and prepare a graphene pseudocapacitive electrode material modified by an expanded-oxidation strategy using vacuum-assisted filtration technology.

[0049] Example 5 This embodiment 5 provides a method for preparing a graphene pseudocapacitive electrode material modified based on an expansion-oxidation strategy, including the following steps: Step 1: Add 1 mL of deionized water to 100 mg of graphene oxide and stir to promote water evaporation until a dough is formed, thus obtaining graphene oxide dough; wherein, the water content of the graphene oxide dough is 8%.

[0050] Step 2: Place the graphene oxide dough between two polytetrafluoroethylene films and transfer it to a flatbed cold press for cold pressing to obtain a graphene oxide film; wherein, the cold pressing pressure is 10MPa and the cold pressing time is 10min.

[0051] Step 3: Place the graphene oxide film in an open aluminum container and heat the bottom of the container with an alcohol lamp to evaporate the water molecules in the graphene oxide film, thereby inducing the graphene oxide film to expand and undergo a reduction reaction to obtain expanded graphene; wherein, the flame heating temperature is 350℃ and the heating time is 6min.

[0052] Step 4: Add expanded graphene to a mixed acid solution and stir at 0°C for 6 hours to obtain expanded-oxidized graphene. The mixed acid solution is a mixture of concentrated sulfuric acid, concentrated nitric acid, and water. The volume ratio of concentrated sulfuric acid to concentrated nitric acid is 3:1. The volume ratio of the sum of the volumes of concentrated sulfuric acid and concentrated nitric acid to water in the mixed acid solution is 100:0. After adding expanded graphene to the mixed acid solution, the mass percentage of expanded graphene in the mixed acid solution is 2 wt%.

[0053] Step 5: Mix expanded-oxidized graphene, electroexfoliated graphene, and bacterial cellulose in a mass ratio of 40:10:15, and prepare a graphene pseudocapacitive electrode material modified by an expanded-oxidation strategy using vacuum-assisted filtration technology.

[0054] Example 6 This embodiment 6 provides a method for preparing a graphene pseudocapacitive electrode material modified based on an expansion-oxidation strategy, including the following steps: Step 1: Add 1 mL of deionized water to 100 mg of graphene oxide and stir to promote water evaporation until a dough is formed, thus obtaining graphene oxide dough; wherein, the water content of the graphene oxide dough is 8%.

[0055] Step 2: Place the graphene oxide dough between two polytetrafluoroethylene films and transfer it to a flatbed cold press for cold pressing to obtain a graphene oxide film; wherein, the cold pressing pressure is 10MPa and the cold pressing time is 10min.

[0056] Step 3: Place the graphene oxide film in an open aluminum container and heat the bottom of the container with an alcohol lamp to cause the water molecules in the graphene oxide film to evaporate, thereby inducing the graphene oxide film to expand and undergo a reduction reaction to obtain expanded graphene; wherein, the flame heating temperature is 400℃ and the heating time is 8min.

[0057] Step 4: Add expanded graphene to a mixed acid solution and stir at 0°C for 12 hours to obtain expanded-oxidized graphene. The mixed acid solution is a mixture of concentrated sulfuric acid, concentrated nitric acid, and water. The volume ratio of concentrated sulfuric acid to concentrated nitric acid is 3:1. The volume ratio of the sum of the volumes of concentrated sulfuric acid and concentrated nitric acid to water in the mixed acid solution is 100:0. After adding expanded graphene to the mixed acid solution, the mass percentage of expanded graphene in the mixed acid solution is 5 wt%.

[0058] Step 5: Mix expanded-oxidized graphene, electroexfoliated graphene, and bacterial cellulose in a mass ratio of 40:10:15, and prepare a graphene pseudocapacitive electrode material modified by an expanded-oxidation strategy using vacuum-assisted filtration technology.

[0059] Comparative Example This comparative example provides a method for preparing a graphene composite film material, including the following steps: Step 1: Add 1 mL of deionized water to 100 mg of graphene oxide and stir to promote water evaporation until a dough is formed, thus obtaining graphene oxide dough; wherein, the water content of the graphene oxide dough is 5%.

[0060] Step 2: Place the graphene oxide dough between two polytetrafluoroethylene films and transfer it to a flatbed cold press for cold pressing to obtain a graphene oxide film; wherein, the cold pressing pressure is 9 MPa and the cold pressing time is 9 min.

[0061] Step 3: Place the graphene oxide film in an open aluminum container, and heat the bottom of the open aluminum container with an alcohol lamp to induce the graphene oxide film to expand and undergo a reduction reaction to obtain expanded graphene; wherein, the flame heating temperature is 400℃ and the heating time is 5min.

[0062] Step 4: Mix expanded graphene, electrostripped graphene, and bacterial cellulose in a mass ratio of 30:10:15, and prepare graphene composite membrane material by vacuum-assisted filtration technology.

[0063] Performance Description: As attached Figure 1 As shown, attached Figure 1 The image presents SEM images of expanded graphene and expanded-oxidized graphene; among them, Figure 1 a is the SEM image of the expanded graphene in the comparative example; Figure 1 b is a SEM image of the expanded-oxidized graphene in Example 5; from the appendix Figure 1As can be seen, expanded graphene was obtained by flame heating of graphene oxide films under normal pressure. The expanded graphene exhibits a fluffy, porous, and highly wrinkled layered structure, fundamentally different from the morphology of traditional graphene and graphene prepared by ordinary redox methods. The expanded graphene possesses a unique morphology of interwoven "sheet stacking" and "nanoscale pores," a direct result of the rapid vaporization of water molecules between graphene oxide layers induced by direct flame. The enormous expansion force generated by the instantaneous vaporization of interlayer water forces the graphene sheets to separate and fix, forming a permanent porous structure. Furthermore, the rapid expansion through water molecule vaporization results in a larger specific surface area compared to graphene oxide, with more active sites and pore structures appearing on the surface, leading to more efficient charge storage. This process, particularly from the attached... Figure 1 As can be seen in b, after further oxidation to introduce functional groups, the expanded-oxidized graphene exhibits obvious wrinkling, and the arrangement of graphene sheets is optimized.

[0064] Appendix Figure 2 Optical photographs of graphene oxide, expanded graphene, and expanded-oxidized graphene in Example 5 are shown in the appendix. Figure 2 As can be seen, under the same mass, the powder volume decreases in the order of expanded graphene, expanded-oxidized graphene, and graphene oxide. This decreasing trend is attributed to the morphological changes caused by the changes in surface functional groups, which further confirms that rapid water vapor expansion effectively changes the microstructure of graphene powder and increases its specific surface area.

[0065] As attached Figure 3 As shown, attached Figure 3 The figure shows the relationship between the specific capacitance of the graphene composite film material prepared in the comparative example and the current density; from the attached figure... Figure 3 As can be seen from the comparison, the graphene composite film material prepared in the comparative example has a performance of 1 mA / cm². -2 The specific capacitance can reach 211 F / g, which is due to the fact that the expansion of water molecules improves the specific surface area and conductivity of the material, thereby increasing the charge storage capacity of the electrode.

[0066] As attached Figure 4 As shown, attached Figure 4 The figure shows the relationship between the specific capacitance and current density of the graphene pseudocapacitive electrode materials modified by the expansion-oxidation strategy prepared in Examples 1-6; from the appendix... Figure 4 As can be seen from the data, the graphene pseudocapacitive electrode material prepared in Example 1 exhibits performance at 1 mA / cm². -2The specific capacitance can reach 256 F / g, which is attributed to the optimized distribution of surface functional groups and arrangement of graphene sheets under the oxidation of expanded graphene in mixed acid, representing a 121% improvement compared to the graphene composite film material prepared in the comparative example; the graphene pseudocapacitive electrode material prepared in Example 2 achieves a specific capacitance of 1 mA / cm². -2 The specific capacitance can reach 286 F / g, which is attributed to the optimized distribution of surface functional groups and arrangement of graphene sheets under the oxidation of expanded graphene in mixed acid, representing a 135% improvement compared to the graphene composite film material prepared in the comparative example; the graphene pseudocapacitive electrode material prepared in Example 3 achieves a specific capacitance of 1 mA / cm². -2 The specific capacitance can reach 328 F / g, which is attributed to the optimized distribution of surface functional groups and arrangement of graphene sheets under the oxidation of expanded graphene in mixed acid, representing a 155% improvement compared to the graphene composite film material prepared in the comparative example; the graphene pseudocapacitive electrode material prepared in Example 4 achieves a specific capacitance of 1 mA / cm². -2 The specific capacitance can reach 355 F / g, which is attributed to the optimized distribution of surface functional groups and arrangement of graphene sheets under the oxidation of expanded graphene in mixed acid, representing a 168% improvement compared to the graphene composite film material prepared in the comparative example; the graphene pseudocapacitive electrode material prepared in Example 5 achieves a specific capacitance of 1 mA / cm². -2 The specific capacitance can reach 399 F / g, which is attributed to the optimized distribution of surface functional groups and arrangement of graphene sheets under the oxidation of expanded graphene in mixed acid, representing a 189% improvement compared to the graphene composite film material prepared in the comparative example; the graphene pseudocapacitive electrode material prepared in Example 6 achieves a specific capacitance of 1 mA / cm². -2 The specific capacitance can reach 324 F / g, which is due to the optimization of the distribution of surface functional groups and the arrangement of graphene sheets under the oxidation of expanded graphene by mixed acid, which is 153% higher than that of the graphene composite film material prepared in the comparative example.

[0067] As attached Figure 5 As shown, attached Figure 5 The appendix provides CV curves of the graphene pseudocapacitive electrode material modified by the expansion-oxidation strategy prepared in Example 5 at different scan rates; from the appendix... Figure 5 As can be seen from the CV curve, there is a pair of pseudocapacitive peaks, which further verifies that the material is a pseudocapacitive material.

[0068] As attached Figure 6 As shown, attached Figure 6 The appendix provides infrared spectra of the graphene composite film materials prepared in the comparative examples and the graphene pseudocapacitive electrode materials modified by the expansion-oxidation strategy prepared in Examples 1-6; Figure 6As can be seen from the comparison, the graphene composite film material prepared in the comparative example has a performance at 3300 cm⁻¹. -1 A weak hydroxyl (OH) peak is observed at a wavelength of 1000 cm⁻¹. -1 The presence of weak carboxyl (C=O) peaks on both sides indicates the presence of a small number of hydroxyl, carboxyl, or carbonyl functional groups on its surface; the graphene pseudocapacitive electrode materials prepared in Examples 1-6 exhibit infrared spectroscopy at 1720 cm⁻¹. -1 The presence of a distinct carbonyl (C=O) peak at the specified wavelength, along with characteristic peaks corresponding to hydroxyl and carboxyl groups, indicates that functional groups have been successfully introduced into the material, thereby enhancing its electrochemical activity.

[0069] This invention provides a method for preparing graphene pseudocapacitive electrode materials based on an expansion-oxidation strategy. Through a synergistic expansion-oxidation modification strategy, a graphene-based electrode material with high pseudocapacitive properties is successfully prepared. This material exhibits unique multi-level channels and precisely regulated functional groups in its structure. Specifically, firstly, flame heating induces the instantaneous vaporization of interlayer water in the graphene oxide film, achieving simultaneous expansion and partial reduction, effectively suppressing graphene sheet stacking, forming a fluffy, porous three-dimensional conductive network, and significantly increasing the specific surface area. Subsequently, [the method is described in the original text]. The expanded product is controlled to oxidation using a concentrated sulfuric acid / concentrated nitric acid mixed acid system, which precisely controls the type and distribution of oxygen-containing functional groups on the surface, enriches carboxyl groups (-COOH) with higher pseudocapacitive activity, and inhibits the excessive generation of hydroxyl groups (-OH), thus significantly increasing the -COOH / -OH ratio and significantly enhancing the Faraday pseudocapacitive contribution of the material. The graphene pseudocapacitive electrode material prepared by this invention can be used as an electrode material for supercapacitors and is very suitable for flexible electronics, wearable devices and high-power energy storage systems, etc., and has good industrial application value.

[0070] The above embodiments are merely one of the implementation methods for achieving the technical solution of the present invention. The scope of protection claimed by the present invention is not limited to this embodiment, but also includes any variations, substitutions and other implementation methods that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention.

Claims

1. A method for preparing a graphene pseudocapacitive electrode material modified based on an expansion-oxidation strategy, characterized in that, include: Under normal pressure, graphene oxide film is heated by flame to induce expansion and reduction reactions in the graphene oxide film, thus obtaining expanded graphene. Expanded graphene was added to a mixed acid solution and stirred to carry out an oxidation reaction, yielding expanded-oxidized graphene. Expanded-oxidized graphene, electroexfoliated graphene, and bacterial cellulose were mixed and subjected to vacuum-assisted filtration to obtain a graphene pseudocapacitive electrode material modified based on an expansion-oxidation strategy.

2. The method for preparing a graphene pseudocapacitive electrode material modified by an expansion-oxidation strategy according to claim 1, characterized in that, The preparation process of graphene oxide thin films is as follows: Water is added to graphene oxide and stirred until a dough-like consistency is formed, resulting in graphene oxide dough; the water content of the graphene oxide dough is 3%-8%; The graphene oxide dough was cold-pressed to obtain a graphene oxide film.

3. The method for preparing a graphene pseudocapacitive electrode material modified by an expansion-oxidation strategy according to claim 2, characterized in that, In the process of cold pressing graphene oxide dough to obtain graphene oxide film, the cold pressing pressure is 8-10 MPa and the cold pressing time is 8-10 min.

4. The method for preparing a graphene pseudocapacitive electrode material modified by an expansion-oxidation strategy according to claim 1, characterized in that, Under normal pressure, graphene oxide films are heated by flame to induce expansion and reduction reactions, resulting in expanded graphene. The flame heating temperature is 200-400℃ and the heating time is 5-8 minutes.

5. The method for preparing a graphene pseudocapacitive electrode material modified by an expansion-oxidation strategy according to claim 1, characterized in that, The mixed acid solution is a mixture of concentrated sulfuric acid, concentrated nitric acid and water; wherein the volume ratio of concentrated sulfuric acid to concentrated nitric acid is 3:1; and the volume ratio of the sum of the volumes of concentrated sulfuric acid and concentrated nitric acid to the volume of water in the mixed acid solution is (16-100):(0-84).

6. The method for preparing a graphene pseudocapacitive electrode material modified by an expansion-oxidation strategy according to claim 5, characterized in that, After adding expanded graphene to the mixed acid solution, the mass percentage of expanded graphene in the mixed acid solution is 2-5 wt%.

7. The method for preparing a graphene pseudocapacitive electrode material modified by an expansion-oxidation strategy according to claim 1, characterized in that, Expanded graphene was added to a mixed acid solution and stirred to carry out an oxidation reaction to obtain expanded-oxidized graphene. The oxidation reaction temperature was 0-40℃ and the oxidation reaction time was 6-12h.

8. The method for preparing a graphene pseudocapacitive electrode material modified by an expansion-oxidation strategy according to claim 1, characterized in that, In the raw materials of graphene pseudocapacitive electrode materials modified by the expansion-oxidation strategy, the mass ratio of expanded-oxidized graphene, electroexfoliated graphene and bacterial cellulose is (30-45):10:

15.

9. A graphene pseudocapacitive electrode material modified based on an expansion-oxidation strategy, characterized in that, The graphene pseudocapacitive electrode material modified by the expansion-oxidation strategy as described in any one of claims 1-8 was prepared.

10. The application of the graphene pseudocapacitive electrode material modified by the expansion-oxidation strategy as described in claim 9, characterized in that, The application of graphene pseudocapacitive electrode materials modified by the expansion-oxidation strategy in supercapacitors.

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