A method for preparing a pre-oxidized carbon fiber composite graphene-based electrode felt, an electrode felt and a battery

Abstract

The application discloses a kind of based on pre-oxidized carbon fiber composite graphene electrode soft felt preparation method, electrode soft felt and battery, first by the way of plasma CVD method on the surface of carbon fiber growth oxygen is used to pre-oxidize carbon fiber, and graft oxygen-containing functional groups without destroying the internal structure of carbon fiber;Then again with graphene oxide reaction forms graphene composite carbon fiber filament;Finally, based on graphene composite carbon fiber filament is made into preform.The scheme is based on pre-oxidized carbon fiber composite graphene preparation and forms high-performance electrode soft felt, effectively improves the contact site of electrode, increases energy density, and can effectively overcome the problems existing in prior art.

Description

Technical Field

[0001] This invention relates to new energy electrode materials, specifically to a preparation method for electrode soft felt. Background Technology

[0002] Currently, most carbon fiber soft felts are made from short carbon fibers using non-woven needle punching methods, and are used as electrode materials in flow batteries and fuel cells. Because carbon fiber itself is a single-element carbon material, its chemically stable properties make it difficult to combine with other materials, significantly increasing the difficulty of its modification and composite processing, which limits its performance in applications. Therefore, existing carbon fiber soft felts mainly suffer from the following problems in practical applications:

[0003] (1) Although existing carbon fiber soft felt can meet the requirements of battery contact and conductivity, existing carbon fiber soft felt used in batteries has problems such as few contact points, low electrolyte permeability coefficient, and poor binding ability with active materials. The permeability coefficient and the ability to bind with active materials directly determine the amount of active materials that react with the electrolyte flowing into the electrode felt during the charging and discharging process and the reversibility of the active materials, which in turn determines the performance of the battery coulombic efficiency, energy efficiency, and energy density. Existing carbon fiber soft felt used in batteries has a low permeability coefficient, low activity, poor reaction of active materials, and high side reaction, which makes it difficult for existing carbon fiber soft felt to show good performance in the use of high energy density batteries.

[0004] (2) Carbon fiber itself is chemically stable, difficult to be oxidized, and difficult to be combined with other materials, which affects the actual performance of existing carbon fiber soft felt.

[0005] Chinese patent application CN110931270A discloses a substrate-based graphene-based electrode fiber with high charge storage capacity and its preparation method. The method uses an aqueous solution of graphene oxide as the main raw material, and then coats the fiber substrate with graphene oxide or graphene oxide composites through a simple alternating impregnation process. Subsequently, the graphene oxide is reduced to reduced graphene oxide through chemical reduction or thermal reduction, thereby preparing a substrate-based graphene-based electrode fiber with excellent mechanical and energy storage properties. Linear supercapacitors using this substrate-based graphene-based electrode fiber as the electrode exhibit very large areal specific capacitance and very high energy density. However, in practice, due to the highly stable surface chemical properties of carbon fibers, it is difficult to combine or react with other materials. Therefore, the graphene impregnation and reduction method mentioned in this method makes it difficult to establish a strong bond between graphene and carbon fibers, resulting in poor strength. When used as an energy storage material, it is prone to powder shedding and detachment during charging and discharging.

[0006] The article "Preparation and Performance Study of Multi-scale Graphene-Carbon Fiber Reinforced C-SiC Composites" (Cai Zitian, pp. 21-24, Chongqing Jiaotong University, June 2019) discloses a method for preparing graphene-carbon fiber preforms. Specifically, it provides a technical solution and approach for modifying the carbon fiber surface with concentrated nitric acid. However, this method will damage the carbon fiber structure itself, forming varying degrees of damage and pores on the carbon fiber surface and inside, affecting the final strength. Furthermore, concentrated nitric acid has certain hazards and pollution, is not environmentally friendly, and is difficult to remove after the reaction. Therefore, the overall practicality of this solution is poor.

[0007] Chinese patent application CN103321035A discloses a method for surface modification of carbon fiber by plasma grafting graphene oxide; and Chinese patent application CN103321034A discloses a method for surface modification of carbon fiber by plasma grafting carbon nanotubes. Both disclose a scheme for functionalizing carbon fiber surface using plasma. Although this is more environmentally friendly and safer than the schemes disclosed in the previous articles, the specific technical solution involves using plasma of various small gas molecules to treat the carbon fiber surface for a short time at room temperature. This is essentially an activation process for the carbon fiber surface. No stable chemical bonds are formed between carbon and oxygen. The result is merely to activate the carbon fiber surface to facilitate grafting with other materials, but it cannot achieve true oxidation or functionalization of the carbon fiber with other groups. As is well known, the connection after surface activation is a combination of van der Waals forces and electrostatic adsorption, which is completely different from the chemical bond formed through a chemical reaction. The final connection structure has low stability and connection strength, which cannot meet practical requirements. Summary of the Invention

[0008] To address the problems existing in existing carbon fiber soft felts and existing carbon fiber and graphene composite reinforced materials, the present invention aims to provide a method for preparing electrode soft felts. This method pre-oxidizes carbon fibers by growing oxygen on the carbon fiber surface using plasma CVD, and then prepares a high-performance electrode soft felt based on the pre-oxidized carbon fiber and graphene composite, effectively improving the contact sites of the electrode and increasing energy density. Furthermore, the present invention provides the electrode soft felt prepared by this method and a battery using the electrode soft felt.

[0009] To achieve the above objectives, the present invention provides a method for preparing electrode soft felt based on pre-oxidized carbon fiber composite graphene, comprising:

[0010] (1) Place the carbon fiber filament in a high-temperature furnace, and pass a mixture of 10% oxygen and 90% argon gas into the high-temperature furnace. At the same time, set the temperature to 250-400℃ and introduce oxygen treated by a plasma generator into the high-temperature furnace so that oxygen atoms can grow continuously on the surface of the carbon fiber for 1-2 hours to obtain oxidized carbon fiber filament.

[0011] (2) Select graphene oxide of uniform specifications, prepare it into an aqueous solution of the corresponding concentration, stir it evenly, let it stand, and shear it horizontally to make the graphene oxide solution oriented.

[0012] (3) The oxidized carbon fiber filaments obtained in step (1) are pulled in one direction through the highly oriented graphene oxide solution in step (2) so that the graphene sheets are uniformly attached to the carbon fiber filaments and then dried. In the obtained mixed material, the relative weight ratio of graphene sheets to carbon fiber filaments is 1:15-20.

[0013] (4) Place the dried graphene-coated carbon fiber obtained in step (3) into a polytetrafluoroethylene reaction vessel, add 5-10 wt% reducing agent, and carry out hydrothermal reduction treatment. The hydrothermal treatment temperature is 200-240℃ and the heat treatment time is 8-12h. Finally, take it out and dry it to obtain graphene composite carbon fiber.

[0014] In some embodiments of the present invention, the graphene oxide used in the preparation method is a highly oriented small-sized graphene oxide slurry.

[0015] In some embodiments of the present invention, the preparation method is based on graphene composite carbon fiber filaments to make a preform, in which the graphene composite carbon fiber filaments are combed into a web and laid into a fiber web, and multiple layers of web are sequentially stacked and the stacked multiple layers of web are repeatedly needle-punched to make a preform.

[0016] To achieve the above objectives, the present invention provides an electrode soft felt, which is prepared by the above-described electrode soft felt preparation method.

[0017] In some embodiments of the present invention, the specific surface area of ​​the electrode felt is increased by 1-2 times, the conductivity is increased by 30-50%, and the ion adsorption capacity is increased by 1-2 times.

[0018] To achieve the above objectives, the present invention provides a battery in which electrodes are formed using the aforementioned electrode felt.

[0019] In some embodiments of the present invention, the battery specific capacity is increased by 20-30%, the battery life is increased by 10-20%, and it can accept larger current charging and discharging.

[0020] The electrode felt preparation method based on pre-oxidized carbon fiber composite graphene provided in this invention has the following advantages compared with the prior art:

[0021] (1) In this scheme, the connection of graphene sheets can effectively improve the overall chemical activity of carbon fiber composite material, increase the active sites of the electrode reaction products, and effectively solve the problem of the difficulty of combining electrode felt with other materials.

[0022] (2) The electrode felt prepared by this scheme can effectively improve the conductivity of the battery, enabling the battery to rapidly and reversibly de-intercalate and de-intercalate the electrode active material during high-current charging and discharging, thereby reducing the occurrence of side reactions. In flow batteries, the viscous electrolyte needs to wet the electrode felt during charging and discharging, undergoing electrochemical reactions and adhering to the active sites on the electrode felt. Simultaneously, the electrolyte is constantly in a high-pressure, high-speed flow state, causing severe erosion and damage to the electrode felt. If the internal fiber bonding of the electrode felt is poor, it is easily destroyed, leading to a sharp decrease in the battery's coulombic efficiency and energy efficiency. This scheme achieves a strong bond between graphene and carbon fiber, ensuring that the structure is not damaged during rapid adsorption and de-intercalation. Furthermore, the high conductivity and adhesion properties of graphene allow the active material to deposit and react on the electrode, preventing side reactions from occurring, thus solving the problem of high-current charging and discharging.

[0023] (3) The electrode soft felt prepared by this scheme can effectively increase the active sites of the overall electrode felt, making it possible to adsorb more electrode active materials, thereby increasing the overall energy density of the battery. Attached Figure Description

[0024] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0025] Figure 1 This is a microstructure diagram of the graphene sheet composite carbon fiber filament in an example of the present invention;

[0026] Figure 2 This is a macroscopic view of the graphene-carbon fiber composite electrode felt in an example of the present invention.

[0027] Figure 3 This is a comparison diagram showing the adhesion effect of active materials during the use of the battery in the example of the present invention;

[0028] Figure 4 This is a cross-sectional and surface photograph of the composite soft felt in this invention.

[0029] Explanation of the labels in the diagram:

[0030] 10-Carbon fiber filament; 20-Graphene; 30-Functional group; 40-Active site. Detailed Implementation

[0031] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific illustrations.

[0032] By studying the characteristics and problems of existing carbon fiber soft felt, the inventors innovatively pre-oxidized carbon fibers by growing oxygen on the surface of carbon fibers using plasma CVD. This method can graft oxygen-containing functional groups onto the carbon fiber without changing its structure and strength, thereby increasing the grafting sites for other materials and making the subsequent chemical reaction more effective. This effectively overcomes the problems that carbon fibers are difficult to oxidize and difficult to combine with other materials.

[0033] This method differs from conventional plasma surface activation technology in its pre-oxidation of carbon fibers. Instead, it employs plasma chemical vapor deposition (PCVD) growth, using carbon fibers as the substrate. Oxygen atoms are plasma-ionized to form charged oxygen atoms. Under high-temperature conditions of 250-400℃, oxygen atoms grow in a regular arrangement on the carbon fiber substrate, forming a regularly arranged CO and C=O bond structure. This oxidizes the carbon fibers without damaging their structure or affecting their strength. Furthermore, the carbon and oxygen elements are connected by very strong chemical bonds, and the oxygen groups are arranged in a regular pattern.

[0034] Meanwhile, the inventors further discovered that functionalized graphene oxide materials exhibit better adsorption and recombination capabilities; and that modification of graphene can further enhance the adsorption and recombination capabilities of the originally stable sp... 2 The chemical bonds open, becoming sp 3 Its active functional groups can further combine with other materials under specific conditions.

[0035] Building upon this, the inventors innovatively reacted oxidized carbon fibers with graphene oxide to form graphene-composite carbon fiber filaments, effectively increasing the contact points of the electrodes, thereby enhancing the conductivity and energy density of the electrode felt.

[0036] Specifically, this method involves reacting graphene oxide and carbon fibers with oxygen grown on their surface via plasma CVD under hydrothermal conditions, rather than reacting directly in a high-temperature water environment. Instead, a high-temperature and high-pressure reaction environment is created in a hydrothermal sealed reactor. This approach facilitates full contact between graphene and carbon fibers and reduces the activation energy of oxygen functional groups, thereby promoting the reaction process between graphene and carbon fibers.

[0037] Based on the above scheme, the present invention provides a method for preparing electrode soft felt based on pre-oxidized carbon fiber composite graphene. The preparation method first adopts plasma chemical vapor deposition (CVD) growth technology, with carbon fiber as the substrate, and grows oxygen atoms on the surface of the fiber to form oxidized carbon fiber material.

[0038] Based on this, carbon fiber material with oxygen grown on the surface of carbon fiber by plasma CVD is reacted with specific graphene oxide under hydrothermal conditions to form graphene composite carbon fiber filaments; finally, a preform is made based on the graphene composite carbon fiber filaments.

[0039] Thus, the preparation scheme for this electrode soft felt is achieved through the following steps in sequence:

[0040] (1) Place the carbon fiber filament in a high-temperature furnace, and pass a mixture of 10% oxygen and 90% argon gas into the furnace. Set the temperature to 250-400℃. Before the oxygen is introduced into the furnace, ionization treatment is performed to obtain charged oxygen ions. The formation of plasma here is achieved by using a plasma generator to apply electrons to the surface of the material to make the atoms charged, forming a uniform charged ion state, i.e., a plasma beam. These ion state substances can reduce the reaction activation energy and can react with materials without active carbon on the surface.

[0041] In this step, charged oxygen ions are further grown on the carbon fiber surface for 1-2 hours to obtain carbon fiber filaments with oxygen grown on the carbon fiber surface by plasma CVD.

[0042] (2) Select graphene oxide of uniform specifications, prepare it into an aqueous solution of the corresponding concentration, stir it evenly, let it stand, and shear it horizontally to make the graphene oxide solution oriented.

[0043] (3) The carbon fiber filaments obtained in step (1) by growing oxygen on the carbon fiber surface by plasma CVD are pulled in one direction in a highly oriented graphene oxide solution at a pulling speed of 0.05 m / min to 3 m / min, so that the graphene sheets are uniformly attached to the carbon fiber filaments; then they are dried in an oven at 80°C for 0.5-1 h. In the resulting mixed material, the relative weight ratio of graphene sheets to carbon fiber filaments is 1:15-20.

[0044] (4) Place the graphene-coated dry carbon fiber filaments formed in step (3) into a polytetrafluoroethylene reaction vessel, add 5-10wt% reducing agent, and perform hydrothermal reduction treatment. The hydrothermal treatment temperature is 200-240℃, the pressure range is 20-22MPa, and the heat treatment time is 8-12h. Finally, take it out and dry it at 80℃ for 30min-1h to obtain graphene composite carbon fiber filaments.

[0045] In step (1) of this preparation scheme, plasma chemical vapor deposition technology is used to decompose oxygen molecules under the action of plasma to form single-atom charged particles, which are then orderly grown and arranged on the carbon fiber substrate. This process reduces the activation energy and improves the nucleation and growth ability of particles. Unlike the high-temperature decomposition effect of ordinary chemical vapor deposition technology, plasma CVD does not require a particularly high-temperature environment, and it is also different from plasma surface activation technology, which only charges the material surface.

[0046] Through extensive experimentation and creative work, this preparation method uses a mixture of 10% oxygen and 90% argon in step (1). This ensures that the carbon fiber has oxidizing properties without excessive oxidation. At the same time, the reaction temperature is set at 250-400℃ to avoid excessively high temperatures that could increase the degree of oxidation and damage the substrate.

[0047] In some embodiments of the present invention, small-sized graphene oxide sheets are used to prepare solutions of appropriate concentrations. The use of small-sized graphene oxide sheets effectively increases the bonding ability with the carbon fiber surface, allowing them to be arranged perpendicular to the carbon fiber surface rather than wrapping around it, thus increasing the specific surface area.

[0048] The electrode felt formed in this way has high conductivity in battery applications, which is beneficial for the transport of electrons and particles. At the same time, the high specific surface area is also beneficial for increasing the active sites of the electrode material, adsorbing and attaching more active materials, improving the energy storage density of the battery and improving ion transport.

[0049] In some embodiments of the present invention, in step (2), when preparing the graphene solution, a small-sized graphene oxide slurry is used, with the corresponding graphene size being 2-4 μm and the number of layers being 2-5. The concentration of the prepared graphene solution is 2-5 mg / mL. When preparing the graphene solution based on such graphene, it is easier to achieve uniform dispersion in the carbon fiber system. At the same time, relative to the size of the carbon fibers, graphene of this size is less likely to encapsulate the carbon fibers, thus exposing the graphene sheets in space. This is beneficial for increasing the specific surface area and for acting as a bridge between the carbon fiber filaments.

[0050] It should be noted that, in this invention, the inventors, through extensive experimentation and creative work, determined that, based on the subsequent specific pre-oxidation steps, the graphene solution in this step needs to be prepared using graphene with a size of 2-4 μm and 2-5 layers to achieve a concentration of 2-5 mg / mL. If graphene with a size smaller than this range is used to prepare the solution, the graphene size is too small, resulting in poor bridging between the specific surface area and the carbon fibers. If graphene with a size larger than this range is used to prepare the solution, it is easy to form a graphene sheet encapsulating the carbon fiber filaments, which is not conducive to improving the adsorption capacity.

[0051] In some examples of the present invention, the carbon fiber used is preferably carbon fiber with a diameter of 5-20 μm. The inventors determined through a large number of experiments and creative work that the combination of carbon fiber with graphene with other diameters is not good. If the diameter is too thin, it is easy to be wrapped, and if the diameter is too thick, the function of graphene material in increasing surface area and bridging cannot be reflected.

[0052] Based on the characteristics of the combination between graphene and carbon fiber, this preparation scheme innovatively uses small-sized graphene sheets and carbon fibers with a diameter of 5-20 μm to effectively prevent graphene from wrapping the carbon fibers during the reaction process. In this way, under the hydrothermal conditions in step (3), the graphene is completely unbound and can form a one-dimensional connection with the nearby carbon fibers. Since the oxygen functional groups on the carbon fibers are arranged in a regular manner, the graphene will connect to the carbon fiber surface as much as possible in a certain regular way. This will make the site activation energy the lowest when it is vertically aligned, and thus connect into an alignment state perpendicular to the carbon fiber filament.

[0053] In some embodiments of the present invention, when ionizing oxygen before it is introduced into the high-temperature furnace in step (1), a plasma pipeline can be added before the oxygen is introduced into the high-temperature furnace, so that the oxygen passes through the plasma generator before entering the furnace and obtains charged anions. Specifically, under the ionization excitation of the plasma, the original oxygen atoms or oxygen molecules absorb electrons excited by the plasma device, thereby forming electronegative anions.

[0054] Furthermore, in step (1), when carbon fiber filaments are oxidized with 10% anionic oxygen and 90% argon at a temperature of 250-400°C, preferably 300°C, oxygen etching can be formed on the surface of the carbon fiber filaments, that is, oxygen-containing functional groups are connected to the surface of the carbon fiber filaments, thereby improving the chemical activity of the carbon fiber filaments and facilitating their subsequent bonding with graphene.

[0055] It should be noted here that the ratio of anionic oxygen to argon is calculated by volume, that is, 10% anionic oxygen and 90% argon by volume.

[0056] Furthermore, for this scheme, the preferred volume ratio of anionic oxygen to argon is 1:9. If the oxygen ratio is higher than this, it can easily cause irreversible damage to the carbon fiber structure, reducing the strength of the final product; if the oxygen ratio is lower than this, the oxidation effect will be insufficient, resulting in poor reactivity with graphene in the later stages.

[0057] As an example, when implementing this scheme, it is preferred to ensure the ratio by controlling the flow rate of anionic oxygen and argon, but it is not limited to this and other methods can be used as needed.

[0058] In this scheme, in step (3), the oxidized carbon fiber filaments are pulled in one direction through a highly oriented graphene solution. The preferred pulling speed is 0.05 m / min to 3 m / min, so that the graphene sheets are uniformly attached to the carbon fiber filaments. This pulling method can help the graphene to be oriented in the super-pulling direction. The more regular the arrangement, the higher the strength of the overall structure, the better the ion mobility during charging and discharging, and the fewer side reactions.

[0059] In some embodiments of the present invention, during the hydrothermal reduction treatment in step (4), it is preferable to place the graphene-coated carbon fiber filaments in a polytetrafluoroethylene (PTFE) reactor, add 5-10 wt% of a reducing agent, and perform hydrothermal reduction treatment at a temperature of 200-240°C for 8-12 hours. A PTFE reactor is used here because PTFE is chemically stable and will not be corroded during the internal reaction process. Furthermore, PTFE has high strength and high temperature resistance, allowing it to withstand long-term stable use under high temperature and high pressure conditions.

[0060] Furthermore, in step (4), this scheme innovatively employs a reducing agent to generate a large amount of gas during the hydrothermal reduction process. Combined with the internal evaporation and vaporization of water, this allows the pressure to quickly reach close to 22 MPa (the supercritical temperature of water) within the 200-240°C temperature range that polytetrafluoroethylene (PTFE) can withstand, without needing to reach a high temperature of 374°C. This completely solves the problem of achieving the supercritical state of water at lower temperatures. Simultaneously, this scheme drastically reduces the chemical bonding energy and increases the chemical bond strength by operating in the supercritical state of water, thus significantly improving reaction efficiency and achieving a highly efficient chemical reaction. Compared to the conventional subcritical state (i.e., hydrothermal temperature below 200°C and pressure approximately 8 MPa), this scheme achieves the supercritical state of water at lower temperatures by adding a reducing agent during the hydrothermal reduction process, greatly improving the chemical reaction effect.

[0061] Furthermore, the reducing agent used here can be hydroiodic acid, sodium borohydride, lithium aluminum hydride, etc. These reducing agents are used to reduce the oxygen-containing functional groups in the system, thereby enabling the oxygen-free graphene and carbon fibers to form carbon-carbon bonds, improving conductivity and bonding strength.

[0062] In addition, this scheme uses a reducing agent of 5-10 wt%, a hydrothermal treatment temperature of 200-240℃, and a heat treatment time of 8-12 h. This hydrothermal reduction process provides excellent reaction conditions for the reduction reaction, which can effectively promote the reduction reaction and the bonding between graphene and carbon fiber.

[0063] In some examples of the present invention, the electrode soft felt preparation scheme is further based on obtaining graphene composite carbon fiber filaments to make a preform. The graphene composite carbon fiber filaments obtained in step (4) are combed into a net and laid into a fiber net. The multi-layer net is stacked in sequence and the stacked multi-layer net is repeatedly needle-punched to make a preform.

[0064] Furthermore, in the electrode soft felt preparation scheme, during needle punching, the superimposed multi-layer mesh advances horizontally, and a needle plate covered with needles moves downwards and back and forth on the superimposed multi-layer mesh. The sides of the needles have hooks, which will lift some fibers upwards to form fiber bundles. The vertical fiber bundles fix the mesh layer, and finally form longitudinal fibers of a certain density entangled together, combining the superimposed multi-layer mesh into a solid whole.

[0065] As described above, this invention presents a novel approach to preparing electrode felt based on pre-oxidized carbon fiber composite graphene. It innovatively modifies the carbon fibers to improve their chemical activity. Furthermore, it employs plasma CVD to oxidize the carbon fiber filaments by growing oxygen on the carbon fiber surface. This allows for the grafting of oxygen-containing functional groups without damaging the internal structure of the carbon fibers, facilitating their reaction with graphene oxide. This increases the bonding force between the carbon fibers and graphene during the chemical reaction, forming graphene-composite carbon fiber filaments. The resulting composite material effectively solves the problems of insufficient active sites and conductivity inherent in carbon fibers, further improving the conductivity and increasing the energy density of the electrode felt.

[0066] Based on this, the small-sized graphene 20 used has more boundaries and functional groups 30 compared to existing large-sized graphene oxide, increasing the bonding rate with the carbon fiber 10 surface. Furthermore, compared to the large diameter of carbon fibers, it allows for a more vertically close packing of graphene 20 on the carbon fiber 10 surface, rather than encapsulation by large-sized graphene, thus creating effective bonding sites 40, such as... Figure 1 and Figure 3 As shown.

[0067] Meanwhile, due to the high conductivity of graphene, the conductivity of the electrode is effectively improved, which speeds up the conversion of ions or electrons and reduces the occurrence of side reactions.

[0068] See further Figure 2 The figure shown is a macroscopic effect diagram of the graphene carbon fiber composite electrode felt prepared based on the scheme of the present invention. It can be seen that the preparation of electrode felt based on the scheme of the present invention can effectively increase the active sites of the overall electrode felt, providing the possibility for it to absorb more electrode active materials.

[0069] See further Figure 3 The figure shows a comparison of the adhesion effect of active materials in batteries using electrode felt prepared according to the present invention during use. As can be seen from the figure, when the electrode felt prepared according to the present invention is applied to a battery, due to the increase in active sites 40, it can absorb more electrode active materials, thereby effectively increasing the overall energy density of the battery. Furthermore, it can improve the battery's conductivity, allowing the battery to quickly deintercalate and deintercalate electrode active materials during high-current charging and discharging, reducing the occurrence of side reactions and solving the problem of high-current charging and discharging.

[0070] The implementation process and corresponding performance of the solution provided by this invention will be further illustrated below through specific examples.

[0071] Example 1

[0072] In this example, based on the above-mentioned electrode soft felt preparation scheme based on pre-oxidized carbon fiber composite graphene, the corresponding electrode soft felt is prepared through the following specific process steps.

[0073] (1) Place the carbon fiber filament in a high-temperature furnace, and pass a mixture of 10% oxygen and 90% argon gas into the furnace. Set the temperature to 300°C. Before the oxygen is introduced into the furnace, add a plasma pipeline so that the oxygen passes through the plasma generator first when it enters the furnace to obtain charged cations, so that the carbon fiber is continuously oxidized for 2 hours to obtain carbon fiber filament with oxygen grown on the surface of the carbon fiber by plasma CVD.

[0074] (2) Select graphene oxide, prepare a solution of the corresponding concentration, stir evenly, let stand, and shear horizontally to orient the graphene oxide solution; wherein the size of the graphene is 3μm, the number of layers is 4, and the solution is prepared as a graphene oxide solution with a concentration of 3mg / mL.

[0075] (3) The carbon fiber filaments on which oxygen is grown on the carbon fiber surface by plasma CVD are pulled in one direction in a highly oriented graphene solution at a pulling speed of 0.05 m / min so that the graphene sheets are uniformly attached to the carbon fiber filaments; and then placed in an oven at 80℃ to dry for 1 h.

[0076] (4) Place the graphene-coated carbon fiber filaments in a polytetrafluoroethylene reaction vessel, add 5-10 wt% of the reducing agent hydroiodic acid, and carry out hydrothermal reduction treatment. The hydrothermal treatment temperature is 200℃, the pressure is as high as 22 MPa, and the heat treatment time is 12 h. Finally, take it out and dry it at 80℃ for 1 h to obtain graphene composite carbon fiber filaments.

[0077] (5) The carbon fiber filaments are combed into a web and laid into a fiber web. The multi-layer web is then stacked in a cyclic manner and repeatedly needled to form a preform. During needled treatment, the multi-layer web moves horizontally, and a needle plate covered with needles moves back and forth downwards on top of the multi-layer web. The sides of the needles have hooks that lift some fibers upwards to form fiber bundles. The vertical fiber bundles fix the web, and finally, a certain density of longitudinal fibers are entangled together, combining the multi-layer web into a solid whole.

[0078] See Figure 4 The diagram shows a cross-section and surface of the composite soft felt formed according to this embodiment.

[0079] Examples 2-6

[0080] Here, Examples 2-6 are implemented based on the steps and schemes given in Example 1, and based on the specific parameters in Table 1. That is, except for the data in the table, the other steps and conditions are the same as in Example 1.

[0081] Table 1

[0082]

[0083] To further illustrate the technical features of the present invention, corresponding comparative examples are provided here for embodiments 1-6 above:

[0084] Here, comparative embodiments 1-4 are implemented based on the steps and schemes given in embodiment 1, and based on the specific parameters in Table 2. That is, except for the data in the table, the other steps and conditions are the same as in embodiment 1.

[0085] Table 2

[0086]

[0087]

[0088] The corresponding test results in Tables 1 and 2 are obtained for the composite soft felt prepared for each example, with a soft felt compression rate of 20%.

[0089] Conductivity is expressed as resistivity; the lower the resistivity, the better the conductivity. The permeability coefficient represents the activity level of the electrode felt; high-activity electrode felts have high permeability coefficients, while low-activity electrode felts have low permeability coefficients. The density of the electrode felt also reflects the porosity of the electrode; high-porosity electrode felts have low density and large specific surface area, which facilitates electrolyte flow and active material adhesion, thus improving battery energy efficiency and coulombic efficiency.

[0090] As shown in Table 2, among the four sets of comparative examples, comparative example 1 is an electrode felt with weak graphene bonding, comparative example 2 is an electrode felt oxidized by a strong oxidant, comparative example 3 is an electrode felt formed by adding unreduced graphene oxide, and comparative example 4 is an electrode felt formed without adding graphene.

[0091] Based on this, by comparing the test results of the electrode felts formed for the four comparative examples in Table 2 with the test results of the soft felts formed in Table 1, it can be seen that the degree of activation, the addition of graphene, and the processing technology of graphene addition will all affect the performance of the formed electrode felts.

[0092] Furthermore, based on the test results in Table 1 of this application, it can be seen that the electrode soft felt prepared by the preparation method given in this invention has significantly improved conductivity, permeability coefficient, and density, thereby comprehensively improving the performance of the electrode soft felt.

[0093] Furthermore, a performance comparison test was conducted between the electrode felts prepared in Examples 1-6 of Table 1 and the graphene-free electrode felts prepared by conventional methods. The test results are as follows:

[0094] Performance of existing graphene-free electrode felts: The specific surface area of ​​existing electrode felts is 1000 m². 2 / g, conductivity is 0.2-1Ω·mm, and ion adsorption capacity corresponds to specific surface area.

[0095] The electrode felt prepared by the method in this example was tested in multiple groups, and the measured specific surface area was 1200-1500 m². 2 The specific surface area is between 0.05 and 0.1 Ω·mm, while the conductivity is between 0.05 and 0.1 Ω·mm. The ion adsorption capacity corresponds to the specific surface area.

[0096] By comparison, it can be determined that the electrode soft felt formed in this example has a 20-50% increase in specific surface area, a 4-10 times increase in conductivity, and a 1-2 times increase in ion adsorption capacity.

[0097] Furthermore, when the electrode formed by the electrode soft felt prepared in this example is applied to a battery, compared with a battery using an electrode formed by carbon fiber soft felt, the energy density of the battery using the electrode soft felt prepared in this example is estimated to be increased by about 20-30%, the battery life is increased by 10-20%, and it can accept a larger current for charging and discharging. This results in a significant improvement in multiple aspects of the battery's performance, achieving unexpected results.

[0098] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing electrode soft felt based on pre-oxidized carbon fiber composite graphene, characterized in that, include: (1) Place the carbon fiber filament in a high-temperature furnace, and pass a mixture of 10% oxygen and 90% argon gas into the high-temperature furnace. At the same time, set the temperature to 250-400℃ and introduce oxygen treated by a plasma generator into the high-temperature furnace so that charged oxygen atoms grow and arrange in an orderly manner on the carbon fiber surface for 1-2 hours to obtain carbon fiber filament with oxygen growing on the carbon fiber surface. (2) Select graphene oxide with a size of 2-4 μm and 2-5 layers, prepare it into an aqueous solution with a concentration of 2-5 mg / mL, stir it evenly, let it stand, and shear it horizontally to orient the graphene oxide solution. (3) The carbon oxide filaments obtained in step (1) are pulled in one direction through the highly oriented graphene oxide solution in step (2) so that the graphene sheets are uniformly attached to the carbon fiber filaments and then dried. In the resulting mixed material, the relative weight ratio of graphene sheets to carbon fiber filaments is 1:15-20. (4) Place the dried graphene-coated carbon fiber filaments obtained in step (3) into a polytetrafluoroethylene reaction vessel, add 5-10 wt% reducing agent, and perform hydrothermal reduction treatment. The hydrothermal treatment temperature is 200-240℃ and the heat treatment time is 8-12h, so that the graphene is connected in an arrangement perpendicular to the surface of the carbon fiber filaments. Finally, take it out and dry it to obtain graphene composite carbon fiber filaments.

2. The method for preparing electrode soft felt based on pre-oxidized carbon fiber composite graphene according to claim 1, characterized in that, The preparation method is based on the graphene composite carbon fiber filaments. When making the preform, the graphene composite carbon fiber filaments are combed into a web and laid into a fiber web. The multi-layer web is then stacked in sequence and the stacked multi-layer web is repeatedly needle-punched to make the preform.

3. An electrode felt, characterized in that, The electrode felt is prepared using the electrode felt preparation method described in any one of claims 1-2.

4. A battery, characterized in that, The battery uses the electrode felt as described in claim 3 to form electrodes.

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