Bacterial cellulose / resin composite material, and preparation method and application thereof

Abstract

The application discloses a bacterial cellulose / resin composite material and a preparation method and application thereof, and relates to the technical field of electrode materials. The composite material has vertically arranged pores; and the pore wall of the pores is composed of a porous disordered hard carbon structure and a strip-shaped graphite layer interpenetrated in the porous disordered hard carbon structure. The application further provides a preparation method and application of the composite material. The composite material provided by the application has the porous disordered hard carbon structure interpenetrated with the strip-shaped graphite layer, has rich sodium storage sites such as interlayer and pores, and can improve the capacity of a low-voltage platform region. Meanwhile, the composite material has a large specific surface area and the strip-shaped graphite layer interpenetrated in the disordered region, accelerates the transmission process of sodium ions, makes the sodium ions still have a high platform region capacity under a high current density, and can improve the overall energy density of a full battery.

Description

Technical Field

[0001] This invention relates to the field of electrode materials technology, specifically to a bacterial cellulose / resin composite material, its preparation method, and its application. Background Technology

[0002] With "carbon peaking and carbon neutrality" becoming a global consensus, the new energy industry is experiencing explosive growth, and its proportion in the overall energy system is rapidly increasing. New energy sources are intermittent and unstable; therefore, energy storage systems can be used to store electricity that cannot be connected to the grid, achieving peak shaving and valley filling, which is an effective way to reduce energy waste. Currently, lithium-ion batteries, which are widely used in electrochemical energy storage systems, are facing problems such as resource scarcity, rising costs, and safety concerns.

[0003] Sodium, belonging to the same group as lithium, has more abundant and more evenly distributed resources, thus offering a greater cost advantage. Sodium-ion batteries are also safer than lithium-ion batteries. However, the energy density of sodium-ion batteries is lower than that of lithium-ion batteries, making them promising for energy storage applications where energy density requirements are lower and cost is more sensitive. Currently, sodium-ion battery anode materials mainly include titanium-based materials, organic materials, alloy materials, metal oxides / sulfides, and carbon-based materials. Among carbon-based materials, hard carbon, with its highly disordered structure, abundant defect concentration, high heteroatom content, and unique microstructure including large interlayer spacing, abundant porosity and defects, and surface functional groups, can provide a large number of sodium storage sites, resulting in high reversible capacity. However, hard carbon is composed of randomly oriented and short-distance ordered graphite microcrystals, micropores, and highly disordered amorphous carbon regions, leading to structural inhomogeneity and complexity. However, the charge-discharge curves of hard carbon exhibit a certain regularity, consisting of a high-voltage ramp region (0.10-1.00 V) and a low-voltage plateau region (0.01-0.10 V). The high-voltage ramp region is attributed to the adsorption process, mainly influenced by edge defects and functional groups, while the low-voltage plateau region is primarily attributed to interlayer insertion and pore filling of graphite. However, as the current density increases, the plateau capacity is affected by low conductivity and poor sodium ion diffusion kinetics, becoming the rate-determining step in the entire charge-discharge process. Those skilled in the art have constructed hard carbon with abundant micropores to obtain high reversible capacities (up to 360 mAh g⁻¹). -1 This can reduce capacity loss at high current densities. Meanwhile, by increasing the temperature or adding a catalyst, highly graphitized hard carbon can be obtained, resulting in better rate performance. However, this leads to a low or absent low-voltage plateau, which is detrimental to improving the overall energy density of the battery.

[0004] To simultaneously improve the capacity and rate performance of materials, those skilled in the art have mainly focused on introducing heteroatoms such as N, S, and P, and exploring various novel carbon precursors, primarily by increasing the carbonization temperature of the material, thereby simultaneously promoting the formation of closed pores and graphite crystallites. However, as the temperature increases, sodium ions become increasingly difficult to insert into the graphite layer (<0.36 nm), accompanied by increased costs. Furthermore, a comprehensive and clear understanding of the intrinsic charge storage mechanism during the charging and discharging process of hard carbon remains under debate. Summary of the Invention

[0005] To address the shortcomings of existing technologies, various novel carbon precursors primarily promote the formation of closed pores and graphite crystals by increasing the carbonization temperature of the material. However, as the carbonization temperature increases, the graphitization degree of the carbon material increases, resulting in an interlayer spacing of less than 0.36 nm for (002) layers, making it difficult for sodium ions to insert into the graphite interlayers. This invention provides a bacterial cellulose / resin composite material, its preparation method, and its application. This bacterial cellulose / resin composite material has a porous, disordered hard carbon structure with interpenetrating striped graphite layers, possessing abundant sodium storage sites such as interlayers and pores, which can improve the capacity in the low-voltage plateau region. Simultaneously, its large specific surface area and the interpenetrating striped graphite layers within the disordered region accelerate the sodium ion transport process, enabling it to maintain a high plateau region capacity even at high current densities, thus improving the overall energy density of the full battery.

[0006] To achieve the above objectives, a first aspect of the present invention provides a bacterial cellulose / resin composite material having oriented vertical channels; the channel walls are composed of a porous disordered hard carbon structure and strip-shaped graphite layers interspersed within the porous disordered hard carbon structure.

[0007] Preferably, the porous disordered hard carbon structure is obtained by carbonization of water-soluble resin; the ribbon-like graphite layer is obtained by carbonization of bacterial cellulose.

[0008] Preferably, the mass ratio of bacterial cellulose to water-soluble resin is 1:6 to 12.

[0009] Preferably, the carbonization treatment temperature is 800–2000℃; the treatment time is 0.5–12h.

[0010] Preferably, the water-soluble resin includes melamine-formaldehyde resin and / or resorcinol-formaldehyde resin; or epoxy resin.

[0011] A second aspect of this invention provides a method for preparing a bacterial cellulose / resin composite material, comprising the following steps:

[0012] The bacterial cellulose dispersion was dispersed in a water-soluble resin solution to obtain a mixed liquid;

[0013] The mixed liquid was subjected to directional freezing and then vacuum freeze-drying to obtain the freeze-dried complex;

[0014] The freeze-dried composite was pre-oxidized in air at 230–320°C for 1–3 h, and then carbonized in an inert atmosphere to obtain a bacterial cellulose / resin composite material.

[0015] Preferably, the bacterial cellulose dispersion is prepared by the TEMPO method from bacterial cellulose gel.

[0016] Preferably, the directional freezing process includes pouring the mixed liquid into a vertical directional freezing device and adding liquid nitrogen to perform directional freezing.

[0017] Preferably, the vacuum freeze-drying temperature is -60 to -45°C, and the drying time is 24 to 48 hours.

[0018] A third aspect of the present invention provides the application of a bacterial cellulose / resin composite material in a sodium-ion battery anode material.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] This invention provides a bacterial cellulose / resin composite material, its preparation method, and its applications. This composite material, featuring ribbon-like graphite layers interspersed within a porous, disordered hard carbon structure, serves as a sodium-storage anode material. The key advantage lies in the construction of numerous ribbon-like graphite layers within a large-area porous, disordered carbon region, acting as sodium-ion transport channels. Simultaneously, the interspersed ribbon-like graphite layers within the porous, disordered hard carbon structure accelerate the sodium-ion transport process, maintaining a high plateau capacity even at high current densities and thus improving the overall energy density of the full battery.

[0021] In the preparation process of this invention, a conductive fiber network is mainly constructed in the resin using an ice-templating method to obtain a porous, disordered hard carbon structure with a high proportion of carbon. The ice-templating strategy generates ordered, layered channels, accelerating the extrusion of small molecules at high temperatures, thereby improving the overall graphitization degree of the material. Furthermore, the added bacterial cellulose not only enhances conductivity but also forms numerous ribbon-like graphite layers in the resin region as transport channels. Specifically, after the resin material is pre-oxidized, the continuous extrusion of small molecules at high temperatures generates numerous closed pores, which not only increases the capacity at high current densities but also improves the capacity proportion in the low-voltage plateau region. As a bacterial cellulose / resin composite material, it exhibits excellent rate performance as a sodium-ion battery anode material. Therefore, this special hard carbon composite structure ensures the material's capacity at high current densities while maintaining a high capacity proportion in the plateau region. Attached Figure Description

[0022] Figure 1 This is a TEM image of the bacterial cellulose / resin composite material prepared in Example 1.

[0023] Figure 2 This is a SEM image of the bacterial cellulose / resin composite material prepared in Example 1, perpendicular to the pore direction.

[0024] Figure 3 This is a SEM image of the bacterial cellulose / resin composite material prepared in Example 1, parallel to the pore direction.

[0025] Figure 4 This is the XRD pattern of the bacterial cellulose / resin composite material prepared in Example 1.

[0026] Figure 5 This is a rate performance graph of the bacterial cellulose / resin composite material prepared in Example 1 under different current densities.

[0027] Figure 6 The voltage-capacity curves of the bacterial cellulose / resin composite material provided in Example 1 as a negative electrode material for sodium-ion batteries are shown.

[0028] Figure 7 The bacterial cellulose / resin composite material prepared in Example 1 was subjected to a current density of 0.5 A g. -1 Cyclic performance under certain conditions.

[0029] Figure 8 The graph shows the rate performance of the bacterial cellulose / resin composite material provided in Example 6 under different current densities.

[0030] Figure 9 The graph shows the rate performance of the bacterial cellulose / resin composite material provided in Example 8 under different current densities.

[0031] Figure 10 The graph shows the rate performance of the bacterial cellulose / resin composite material provided in Example 9 under different current densities.

[0032] Figure 11 The graph shows the rate performance of the bacterial cellulose / resin composite material provided in Comparative Example 1 under different current densities.

[0033] Figure 12 The voltage-capacity curves of the bacterial cellulose / resin composite material provided in Comparative Example 1 as the negative electrode material for sodium-ion batteries are shown. Detailed Implementation

[0034] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the present invention.

[0035] A first aspect of the present invention provides a bacterial cellulose / resin composite material having oriented vertical channels; the pore walls of the channels are composed of a porous disordered hard carbon structure and strip-shaped graphite layers interspersed within the porous disordered hard carbon structure. The composite material has micron-sized oriented vertical channels.

[0036] The porous, disordered hard carbon structure is obtained by carbonization of a water-soluble resin; the ribbon-like graphite layer is obtained by carbonization of bacterial cellulose. The carbonization process is carried out at a temperature of 800–2000°C for 0.5–12 hours. The water-soluble resin includes melamine-formaldehyde resin and / or resorcinol-formaldehyde resin; or epoxy resin.

[0037] This invention provides a bacterial cellulose / resin composite material with ribbon-like graphite layers interspersed within a porous, disordered hard carbon structure as a sodium-storage anode material. The main advantage is the construction of numerous ribbon-like graphite layers within a large-area porous, disordered carbon region, serving as sodium-ion transport channels. Simultaneously, the interspersed ribbon-like graphite layers within the porous, disordered hard carbon structure accelerate the sodium-ion transport process, maintaining a high plateau capacity even at high current densities, thus improving the overall energy density of the entire battery.

[0038] A second aspect of this invention provides a method for preparing a bacterial cellulose / resin composite material, comprising the following steps:

[0039] The bacterial cellulose dispersion was dispersed in a water-soluble resin solution to obtain a mixed liquid;

[0040] The mixed liquid was subjected to directional freezing and then vacuum freeze-drying to obtain the freeze-dried complex;

[0041] The freeze-dried composite was pre-oxidized in air at 230–320°C for 1–3 h, and then carbonized in an inert atmosphere to obtain a bacterial cellulose / resin composite material.

[0042] The bacterial cellulose dispersion is prepared from bacterial cellulose gel using the TEMPO method. The directional freezing process involves pouring the mixed liquid into a vertically directional freezing apparatus and adding liquid nitrogen for directional freezing. The vacuum freeze-drying temperature is -50°C, and the drying time is 36 hours.

[0043] In the preparation process of this invention, a conductive fiber network is mainly constructed in the resin using an ice-templating method to obtain a porous, disordered hard carbon structure with a high proportion of carbon. The ice-templating strategy generates ordered, layered channels, accelerating the extrusion of small molecules at high temperatures, thereby improving the overall graphitization degree of the material. Furthermore, the added bacterial cellulose not only enhances conductivity but also forms numerous ribbon-like graphite layers in the resin region as transport channels. Specifically, after the resin material is pre-oxidized, the continuous extrusion of small molecules at high temperatures generates numerous pores, which not only increases the capacity at high current densities but also improves the capacity proportion in the low-voltage plateau region. The bacterial cellulose / resin composite material provided by this invention exhibits excellent rate performance as a sodium-ion battery anode material. Therefore, this special hard carbon composite structure ensures the material's capacity at high current densities while maintaining a high capacity proportion in the plateau region.

[0044] A third aspect of the present invention provides the application of a bacterial cellulose / resin composite material in a sodium-ion battery anode material.

[0045] It should be noted that, unless otherwise specified, the experimental methods used in the following examples are conventional methods; and the reagents and materials used are commercially available unless otherwise specified.

[0046] The melamine-formaldehyde resin solution used in the following examples was prepared according to the following steps:

[0047] Add 1.26g of melamine and 2.6mL of formaldehyde solution to 10mL of deionized water, and slowly heat to 90℃ in an oil bath while stirring continuously until the solution is clear to obtain a melamine-formaldehyde resin solution.

[0048] The resorcinol-formaldehyde resin solution used in the following examples was prepared according to the following steps:

[0049] Add 1.1g of resorcinol and 1mL of formaldehyde solution to 10mL of deionized water, heat to 90℃ in an oil bath, and stir continuously for 10min to obtain a resorcinol-formaldehyde resin solution.

[0050] The bacterial cellulose dispersion used in the following examples is a 5 mg / mL bacterial cellulose gel prepared by the TEMPO method. -1 A bacterial cellulose dispersion. The bacterial cellulose gel used in the examples was purchased from Guilin Qihong Technology Co., Ltd.; the bacterial cellulose content in the bacterial cellulose gel was 0.5% by mass.

[0051] The preparation method for the bacterial cellulose dispersion is as follows:

[0052] First, rinse the bacterial cellulose (BC) membrane with deionized water (DIW), and then soak it in deionized water for 3 days.

[0053] Next, the BC membrane, measuring 12 cm × 24 cm, was oxidized with 2,2,6,6-tetramethylpiperidine-1-oxygen (TEMPO). The membrane was cut into small pieces and immersed in 100 ml of deionized water containing 0.032 g TEMPO, 0.2 g sodium bromide, and 20 ml of 9% NaClO solution. Throughout the reaction, the pH was controlled at 9-10 at room temperature using diluted hydrochloric acid (0.1 M) and 0.1 M NaOH until the pH remained constant.

[0054] Then, the TEMPO-oxidized bacterial cellulose was washed three times with DIW and suspended in DIW to form BC slurry.

[0055] Finally, the prepared slurry was diluted to 4 mg / mL. -1 The mixture was stirred with a magnetic stirrer for 12 hours to obtain a clear bacterial cellulose dispersion (BCNF).

[0056] Example 1

[0057] A method for preparing a bacterial cellulose / resin composite material includes the following steps:

[0058] (1) Add 0.63g of melamine and 1.3mL of formaldehyde solution to 5mL of deionized water, heat slowly to 90℃ in an oil bath, and stir continuously until the solution is clear; obtain melamine-formaldehyde resin solution; add 0.55g of resorcinol and 1mL of formaldehyde solution to another 5mL of deionized water, heat to 90℃ in an oil bath, and stir continuously for 10min; obtain resorcinol-formaldehyde resin solution;

[0059] (2) Pour the melamine-formaldehyde resin solution and the resorcinol-formaldehyde resin solution into a beaker and mix to obtain a mixed resin solution. Then add 20 mL of 5 mg / mL solution to the resin solution. -1 The bacterial cellulose dispersion was thoroughly stirred and then sonicated for 1 hour to ensure uniform dispersion, thus obtaining a mixed liquid.

[0060] The mass ratio of bacterial cellulose to mixed resin is 1:10; the mixed resin includes melamine-formaldehyde resin and resorcinol-formaldehyde resin in equal mass ratios.

[0061] (3) Pour the mixed liquid into the vertical directional freezing device, pour in liquid nitrogen, and begin directional freezing;

[0062] (4) Place the frozen sample into a vacuum freeze dryer and dry it at -50℃ for 36 hours to obtain the freeze-dried complex;

[0063] (5) The freeze-dried complex was first pre-oxidized in air at 280°C for 2 hours, and then argon gas was introduced at 5°C for 1 minute. -1 The temperature was raised to 1100℃ and held for 2 hours to obtain a bacterial cellulose / resin composite material.

[0064] Example 2

[0065] The bacterial cellulose / resin composite material was prepared using the method described in Example 1, with the following differences:

[0066] In step (5), the freeze-dried complex is first pre-oxidized in air at 230°C for 2 hours, and then argon gas is introduced at 5°C for 1 minute. -1 The temperature was raised to 2000℃ and held for 0.5 hours to obtain a bacterial cellulose / resin composite material.

[0067] Example 3

[0068] The bacterial cellulose / resin composite material was prepared using the method described in Example 1, with the following differences:

[0069] In step (5), the freeze-dried complex is first pre-oxidized in air at 320°C for 2 hours, and then argon gas is introduced at 5°C for 1 minute. -1 The temperature was raised to 800℃ and held for 12 hours to obtain a bacterial cellulose / resin composite material.

[0070] Example 4

[0071] The bacterial cellulose / resin composite material was prepared using the method described in Example 1, with the following differences:

[0072] In step (2), the mass ratio of bacterial cellulose to mixed resin is 1:8.

[0073] Example 5

[0074] The bacterial cellulose / resin composite material was prepared using the method described in Example 1, with the following differences:

[0075] In step (2), the mass ratio of bacterial cellulose to mixed resin is 1:6.

[0076] Example 6

[0077] The bacterial cellulose / resin composite material was prepared using the method described in Example 1, with the following differences:

[0078] In step (2), the mass ratio of bacterial cellulose to mixed resin is 1:12.

[0079] Example 7

[0080] A method for preparing a bacterial cellulose / resin composite material includes the following steps:

[0081] (1) Add 0.63g of melamine and 1.3mL of formaldehyde solution to 5mL of deionized water, heat slowly to 90℃ in an oil bath, and stir continuously until the solution is clear; obtain melamine-formaldehyde resin solution;

[0082] (2) After pouring the melamine-formaldehyde resin solution into a beaker, add 20 mL of 5 mg / mL solution to the melamine-formaldehyde resin solution. -1 The bacterial cellulose dispersion was thoroughly stirred and then sonicated for 1 hour to ensure uniform dispersion, thereby obtaining a mixed liquid; wherein the mass ratio of bacterial cellulose to melamine-formaldehyde resin was 1:10.

[0083] (3) Pour the mixed liquid into the vertical directional freezing device, pour in liquid nitrogen, and begin directional freezing;

[0084] (4) Place the frozen sample into a vacuum freeze dryer and dry it at -50℃ for 36 hours to obtain the freeze-dried complex;

[0085] (5) The freeze-dried complex was first pre-oxidized in air at 280°C for 2 hours, and then argon gas was introduced at 5°C for 1 minute. -1 The temperature was raised to 1100℃ and held for 2 hours to obtain bacterial cellulose / resin composite material.

[0086] Example 8

[0087] A method for preparing a bacterial cellulose / resin composite material includes the following steps:

[0088] (1) Take 5 mL of deionized water, add 0.55 g of resorcinol and 1 mL of formaldehyde solution, heat to 90 °C in an oil bath and stir continuously for 10 min; obtain resorcinol-formaldehyde resin solution;

[0089] (2) After pouring the resorcinol-formaldehyde resin solution into a beaker, add 20 mL of 5 mg / mL resorcinol-formaldehyde resin solution to the beaker. -1 The bacterial cellulose dispersion was thoroughly stirred and then sonicated for 1 hour to ensure uniform dispersion, thereby obtaining a mixed liquid; wherein the mass ratio of bacterial cellulose to resorcinol-formaldehyde resin was 1:10.

[0090] (3) Pour the mixed liquid into the vertical directional freezing device, pour in liquid nitrogen, and begin directional freezing;

[0091] (4) Place the frozen sample into a vacuum freeze dryer and dry it at -50℃ for 36 hours to obtain the freeze-dried complex;

[0092] (5) The freeze-dried complex was first pre-oxidized in air at 280°C for 2 hours, and then argon gas was introduced at 5°C for 1 minute. -1The temperature was raised to 1100℃ and held for 2 hours to obtain bacterial cellulose / resin composite material.

[0093] Example 9

[0094] A method for preparing a bacterial cellulose / resin composite material includes the following steps:

[0095] (1) Prepare an aqueous solution of epoxy resin material; wherein the epoxy resin material is bisphenol A type epoxy resin;

[0096] (2) Pour the aqueous solution of epoxy resin material into a beaker, then add 20 mL of 5 mg / mL solution. -1 The bacterial cellulose dispersion was thoroughly stirred and then sonicated for 1 hour to ensure uniform dispersion, thus obtaining a mixed liquid.

[0097] (3) Pour the mixed liquid into the vertical directional freezing device, pour in liquid nitrogen, and begin directional freezing;

[0098] (4) Place the frozen sample into a vacuum freeze dryer and dry it at -50℃ for 36 hours to obtain the freeze-dried complex;

[0099] (5) The freeze-dried complex was first pre-oxidized in air at 280°C for 2 hours, and then argon gas was introduced at 5°C for 1 minute. -1 The temperature was raised to 1100℃ and held for 2 hours to obtain a bacterial cellulose / resin composite material.

[0100] Comparative Example 1

[0101] The bacterial cellulose / resin composite material was prepared using the method described in Example 1, with the following differences:

[0102] In step (5), pre-oxidation at 280°C in air for 2 hours is not performed.

[0103] To illustrate the structure of the bacterial cellulose / resin composite material provided by the present invention, since the composite materials prepared in the embodiments of the present invention have the same structure, only the bacterial cellulose / resin composite material prepared in Example 1 will be used as an example for illustration.

[0104] Figure 1 These are TEM images of the bacterial cellulose / resin composite material provided in Example 1, wherein... Figure 1 Are TEM images of samples a and b taken from the same sample, or from two different samples? Figure 1 The TEM images show distinct banded graphite layers, mainly from... Figure 1 (a) and Figure 1As can be seen in (b), there is a distinct banded graphite layer that runs through the material, which is significantly higher than the surrounding disordered region. Its diameter is about 5-20 nm. By measuring the banded graphite layer in the TEM image, the interlayer spacing is about 0.38-0.40 nm, which is consistent with the interlayer spacing of the (002) crystal plane calculated by XRD measurement and Bragg's formula as d = 0.38 nm.

[0105] Figure 2 This is a SEM image of the bacterial cellulose / resin composite material prepared in Example 1, perpendicular to the pore direction. Figure 3 This is a SEM image of the bacterial cellulose / resin composite material prepared in Example 1, parallel to the pore direction. From... Figure 2 and Figure 3 Vertically aligned channels with a diameter of 10-20 μm were constructed using the ice template method. The channel walls were formed by bacterial cellulose being compressed to the periphery by ice crystals and then cured with resin, exhibiting distinct strip-like fibrous protrusions on the surface. This facilitates the rapid extrusion of small molecules and increases the degree of graphitization in the material, which is consistent with... Figure 1 The TEM image shown clearly shows a banded graphite layer. Furthermore, the pore walls are composed of resin-encapsulated bacterial cellulose, with visible striations of the bacterial cellulose on the pore wall surface, thus forming a conductive fiber network that accelerates the rapid transport of sodium ions and electrons. Ultimately, this material exhibits excellent rate performance and a low voltage plateau capacity as a sodium-ion battery, providing a suggestion for further commercialization of sodium-ion batteries.

[0106] Figure 4 This is the XRD pattern of the bacterial cellulose / resin composite material prepared in Example 1. Figure 4 The XRD pattern clearly shows that it is a typical hard carbon XRD pattern, as there are broad peaks at 23.6° corresponding to the (002) crystal plane and at 43.6° corresponding to the (100) crystal plane. Using Bragg's formula, the interlayer spacing of the (002) crystal plane can be calculated to be d = 0.38 nm. This is consistent with... Figure 1 The interlayer spacing measured in the TEM image is consistent.

[0107] To further illustrate the application of the bacterial cellulose / resin composite material provided by this invention as a negative electrode material for sodium-ion batteries, the bacterial cellulose / resin composite materials prepared in the examples and comparative examples were tested for relevant performance as negative electrode materials for sodium-ion batteries.

[0108] The bacterial cellulose / resin composite material prepared in Example 1 was used as the negative electrode material for a sodium-ion battery and assembled into a CR2032 coin cell. A sodium sheet (Φ=16, purity >99.9%) was used as the counter electrode, and a glass fiber membrane (Φ=18) was used as the separator. 1 mol L... -1The CR2032 battery was constructed using a NaPF6 and dimethyl ether (DME) mixture as the electrolyte in an argon-filled glove box. The electrodes were fabricated using a cast film, with the slurry consisting of 80% active material, 10% PVDF solution, 10% acetylene black, and 1-methyl-2-pyrrolidone (NMP) by mass. The electrode film substrate was copper foil. Electrode lamination was performed at 0.05, 0.1, 0.2, 0.5, 1, 2, and 5 A g. -1 Charge-discharge performance was tested under different current densities, with a charge-discharge voltage range of 0.01-3.0V. Rate performance is as follows: Figure 5 As shown, the product was measured at concentrations of 0.05, 0.1, 0.2, 0.5, 1, 2, and 5 μg. -1 The reversible capacities at the given current densities were 350, 330, 314, 286, 262, 223, and 130 mAh g, respectively. -1 From the voltage-capacity curve Figure 6 It can be seen that its voltage platform capacity accounts for 2A g -1 At current densities up to 70%, even at current densities reaching 5A g. -1 There is also a low-voltage platform of over 50%. From a cycling performance perspective, such as... Figure 7 It can be seen that the capacity can reach 281 mAh g after 490 cycles at a current density of 0.5 A. -1 Therefore, the bacterial cellulose / resin composite material provided by this invention exhibits excellent rate performance as a negative electrode material for sodium-ion batteries.

[0109] from Figure 8 It can be seen that, Figure 8 The graph shows the rate performance of the bacterial cellulose / resin composite material provided in Example 6 under different current densities. The mass ratio of bacterial cellulose to mixed resin was 1:12. Figure 8 It can be observed that the material exhibits good capacity at low current densities, but its capacity rapidly decreases with increasing current density, especially at 5 Ag. -1 Post-capacity 48mAh g -1 This shows that when the resin ratio is high, the rate performance of the material is poor. This is because there are fewer graphitization channels inside the material, the degree of graphitization is low, resulting in slow sodium ion transport kinetics.

[0110] from Figure 9 It can be seen that, Figure 9 The graph shows the rate performance of the bacterial cellulose / resin composite material provided in Example 8 under different current densities. The bacterial cellulose / resin composite material, prepared solely using resorcinol-formaldehyde resin, from... Figure 9The study revealed that the material exhibits good capacity at low current densities, but its capacity rapidly decreases with increasing current density, indicating poor rate performance. This suggests that the lack of melamine-formaldehyde resin composite material results in a lack of nitrogen doping, leading to a decrease in the material's electrical and ionic conductivity.

[0111] from Figure 10 It can be seen that, Figure 10 The graph shows the rate performance of the bacterial cellulose / resin composite material provided in Example 9 under different current densities. The bacterial cellulose / resin composite material was prepared using bisphenol A type epoxy resin as the epoxy resin material. Figure 10 It can be observed that the material exhibits good capacity at low current densities, but its capacity rapidly decreases with increasing current density, indicating poor rate performance. This suggests that the lack of melamine-formaldehyde resin composite results in insufficient nitrogen doping, leading to a decrease in the material's electrical and ionic conductivity.

[0112] from Figure 11 It can be seen that, Figure 11 The graph shows the rate performance of the bacterial cellulose / resin composite material provided in Comparative Example 1 under different current densities. The bacterial cellulose / resin composite material was obtained without pre-oxidation during the preparation process. Figure 11 It can be clearly observed that the capacity of the unoxidized composite material is lower than that of the preoxidized material, only 150 mAh g. -1 This is because pre-oxidation increases the number of oxygen-containing functional groups in the material, thereby enhancing its cross-linking degree. During the subsequent high-temperature carbonization process, small oxygen-containing molecules such as CO and CO2 escape from the material, leaving abundant pores inside and increasing the material's capacity.

[0113] from Figure 6 and Figure 12 It is evident that pre-oxidation increases the oxygen content of the precursor, enhances the cross-linking degree of the carbonized material, forms more micropores at high temperatures, extends the low-voltage discharge plateau region of the material during electrochemical testing, and ultimately improves the electrochemical performance of the material. In contrast, the capacity of the plateau region in the un-pre-oxidized material in the comparative example is significantly lower than that of the material provided in the examples.

[0114] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A bacterial cellulose / resin composite material, characterized in that, The composite material has oriented vertical channels; the channel walls are composed of a porous disordered hard carbon structure and strip-shaped graphite layers interspersed in the porous disordered hard carbon structure. The porous, disordered hard carbon structure is obtained by carbonization of water-soluble resin; the ribbon-like graphite layer is obtained by carbonization of bacterial cellulose. The mass ratio of bacterial cellulose to water-soluble resin is 1:6~12; The carbonization treatment temperature is 800~2000℃; the treatment time is 0.5~12 h; The water-soluble resin includes melamine-formaldehyde resin and / or resorcinol-formaldehyde resin; or epoxy resin; The bacterial cellulose / resin composite material is prepared according to the following steps: The bacterial cellulose dispersion was dispersed in a water-soluble resin solution to obtain a mixed liquid; The mixed liquid was subjected to directional freezing and then vacuum freeze-drying to obtain the freeze-dried complex; The freeze-dried composite was pre-oxidized in air at 230-320°C for 1-3 hours, and then carbonized in an inert atmosphere to obtain a bacterial cellulose / resin composite material. The bacterial cellulose dispersion is prepared by the TEMPO method from bacterial cellulose gel.

2. A method for preparing the bacterial cellulose / resin composite material according to claim 1, characterized in that, Includes the following steps: The bacterial cellulose dispersion was dispersed in a water-soluble resin solution to obtain a mixed liquid; The mixed liquid was subjected to directional freezing and then vacuum freeze-drying to obtain the freeze-dried complex; The freeze-dried composite was pre-oxidized in air at 230-320°C for 1-3 hours, and then carbonized in an inert atmosphere to obtain a bacterial cellulose / resin composite material.

3. The method for preparing the bacterial cellulose / resin composite material according to claim 2, characterized in that, The directional freezing process includes pouring the mixed liquid into a vertical directional freezing device and adding liquid nitrogen to perform directional freezing.

4. The method for preparing the bacterial cellulose / resin composite material according to claim 2, characterized in that, The vacuum freeze-drying temperature is -60~-45℃, and the drying time is 24~48h.

5. The application of the bacterial cellulose / resin composite material according to claim 1 in the anode material of sodium-ion batteries.

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