Metal negative electrode material with in-situ generated bacterial cellulose protective layer on surface and preparation method of metal negative electrode material

Abstract

The invention discloses a metal negative electrode material with a bacterial cellulose protective layer generated on the surface in situ and a preparation method, and the method comprises the following steps: adding Komagataeibacter sucrofermentans bacterial mother liquor into a sterilized culture medium, carrying out constant temperature static culture, and biosynthesizing bacterial cellulose; putting the metal sheet into a culture medium, and generating a bacterial cellulose coating layer on the surface of the metal sheet through in-situ polymerization; and taking out the metal sheet, and performing soaking, washing and vacuum drying to obtain the metal sheet negative electrode BC (at) Metal with a bacterial cellulose protective layer on the surface. The ultrathin three-dimensional nano reticular fiber layer is polymerized in situ on the surface of the prepared zinc metal negative electrode, is tightly combined with the zinc metal negative electrode, is not easy to fall off, has high mechanical strength, has super-hydrophilicity and capability of promoting zinc ion transmission, and can improve the electrochemical performance of the zinc negative electrode in the water-based zinc ion battery. The method is simple in preparation flow, controllable in process, good in stability, capable of achieving batch production and suitable for macro preparation.

Description

Technical Field

[0001] The present invention belongs to the technical field of new battery materials, and relates to a metal negative electrode material modified by a biological strategy and a preparation method thereof, in particular to a metal negative electrode material with a bacterial cellulose protective layer in-situ generated on the surface and a preparation method thereof. Background Art

[0002] With the acceleration of the global industrialization process, the excessive dependence of mankind on fossil energy has caused many serious environmental problems, such as global warming and air pollution. In this context, accelerating the development and utilization of new energy has become an urgent task. Renewable energy (such as solar energy, wind energy, and water energy) and clean energy (such as hydrogen energy and nuclear energy) have attracted much attention due to their sustainability. To ensure energy security and achieve stable large-scale energy storage and supply, it is particularly urgent to develop green and sustainable large-scale energy storage devices. An ideal large-scale electrical energy storage system (EES) should have characteristics such as low cost, high reliability, good safety, environmental friendliness, high energy efficiency, long cycle life, and high weight energy and power density. Electrochemical energy storage devices dominate among many energy storage systems due to their high energy density and good cycle stability, showing broad application prospects. Lithium-ion batteries have been widely used in the energy storage field due to their high energy density (150 - 265 Wh kg -1 ), high conversion efficiency, long cycle life, and fast charge and discharge capabilities. However, the limited lithium resources, high cost, and safety problems caused by the flammability and toxicity of organic electrolytes severely limit the application of lithium-ion batteries in large-scale energy storage. In the context of energy transformation and sustainable development, developing battery technologies with high safety, high stability, low cost, and environmental friendliness is still the core direction of future battery research.

[0003] Zinc resources are rich in reserves and widely distributed, with significant economic advantages. Its theoretical specific capacity is as high as 820 mAh g -1 , and the volume specific capacity reaches 5855 mAh cm -3 , showing excellent mass and volume energy densities. In addition, zinc shows high environmental humidity tolerance, high hydrogen evolution overpotential, and good safety in aqueous electrolytes, and is non-toxic. These characteristics make metallic zinc an ideal negative electrode material and have attracted extensive attention from the research community. Aqueous zinc-ion batteries (AZIBs) are considered to be one of the most promising large-scale energy storage systems due to their low cost, high safety, environmental friendliness, and excellent electrochemical performance. Compared with organic electrolytes, aqueous electrolytes have high ionic conductivity (~1 S cm -1), which can achieve fast ion transport, thereby increasing the charge and discharge rate of the battery. At the same time, the low toxicity of aqueous electrolytes makes it more environmentally friendly. Therefore, AZIB is considered to be a strong candidate technology for large-scale electrochemical energy storage due to its price advantage, environmental friendliness and high safety, and is expected to become an alternative energy storage system for lithium-ion batteries. Although zinc-ion batteries have many advantages, their service life and performance are still difficult to meet the needs of practical applications. Compared with alkaline electrolytes, neutral and weakly acidic electrolytes can effectively reduce the formation of by-products such as Zn(OH)2 and ZnO. However, during the cycle process, the zinc metal anode still faces serious side reactions such as corrosion, hydrogen evolution, dendrite growth and passivation. These side reactions lead to reduced Coulombic efficiency (CE), rapid capacity decay and poor battery reversibility, further exacerbating the risk of battery short circuit.

[0004] Modification of the negative electrode of zinc-ion batteries is an important means to improve the overall performance of the battery, including alloying treatment, modification of the negative electrode surface structure and zinc negative electrode interface protection. For example, the method of zinc negative electrode interface protection can be used to adjust the electrode / electrolyte interface in disguise by introducing a coating, provide more nucleation sites, promote uniform zinc deposition and reduce side reactions. At present, these strategies are basically completed using physical or chemical methods. For example, using a physical scraper method or spin coating method to coat a protective layer on the surface of the zinc negative electrode can effectively isolate the direct contact between the zinc negative electrode and the electrolyte, and reduce side reactions such as hydrogen evolution and corrosion. Or use a surface chemical modification method to form a stable interface layer on the surface of the zinc negative electrode through chemical reaction, regulate the nucleation and deposition behavior of zinc ions, and make it more uniform. However, these methods all have certain defects. The physical coating has poor bonding strength with the zinc negative electrode, and the coating may fall off due to mechanical stress or chemical corrosion, resulting in a decrease in the modification effect. Surface chemical modification usually requires complex chemical reaction conditions, which may be accompanied by a certain degree of pollution. Its production cost is high and it is often impossible to achieve large-scale mass production.

[0005] Upon retrieval, "Research on Electrophoretic Cellulose Surface Modification of Metallic Zinc Anode and Performance of Zinc-Ion Batteries" (Wang Yanyan of Yanshan University) discloses that a bacterial cellulose coating layer was constructed on the surface of metallic zinc foil through an electrophoretic deposition process, and the surface of the metallic zinc anode was modified to promote the uniform deposition of zinc ions, achieving the purpose of suppressing side reactions such as dendrite growth and hydrogen evolution corrosion and improving electrochemical performance. However, it has problems such as complex process, insufficient material bonding force, and lack of environmental friendliness: 1) Process complexity: To construct a bacterial cellulose coating layer through the electrophoretic deposition process, it is necessary to rely on an external electric field, a conductive substrate, and precise solution control (such as pH, conductivity, etc.). The equipment investment is large and the energy consumption is high, making large-scale production difficult. 2) Material bonding force: During the electrophoretic deposition process, cellulose particles are deposited on the zinc surface driven by the electric field, which may lead to loose fiber distribution or poor orientation, affecting the bonding strength between the protective layer and the zinc substrate. 3) Lack of environmental friendliness: Electrophoretic deposition may introduce impurities and affect the battery performance.

[0006] CN 119505604 A discloses that bacterial cellulose was modified with ammonium dihydrogen phosphate and urea to obtain phosphorylated bacterial cellulose. After adding water and dispersing, it was drop-coated on the surface of the zinc anode. After drying, the surface of the zinc anode was modified with a phosphorylated bacterial cellulose coating. However, it also has defects such as insufficient coating bonding force and difficulty in large-scale preparation: 1) Insufficient coating bonding force: Phosphorylated bacterial cellulose adheres to the zinc surface by the drop-coating method, which relies on physical adsorption or van der Waals force. The coating formed by the drop-coating method is prone to peeling due to mechanical stress or electrolyte scouring during long-term cycling, affecting the long-term effectiveness of the protective layer. Specifically, in the drop-coating method process, the fluidity and surface tension of the phosphorylated bacterial cellulose dispersion may lead to uneven coating thickness (such as edge effect), and it is difficult to form a dense network at the microscale. 2) Difficulty in large-scale preparation: The drop-coating method requires precise control of the dispersion concentration, coating speed, and drying conditions, and the process parameters are highly sensitive. Summary of the Invention

[0007] Aiming at the deficiencies of the above-mentioned existing technologies, the present invention provides a zinc metal negative electrode material with a highly stable surface in-situ generated bacterial cellulose protective layer based on a biological strategy modification and a preparation method thereof. The highly innovative biological method effectively solves problems such as the long preparation process of the zinc negative electrode interface protective layer and the weak binding ability between zinc and the protective layer. In the BC@Zn negative electrode prepared by the present invention, the bacterial cellulose has a high crystallinity and rich hydroxyl functional groups, making the hydrogen bond interaction between cellulose relatively strong, which endows the cellulose separator with ideal mechanical properties, excellent hydrophilicity, uniform pore structure and high insulation. It can slow down the hydrogen evolution reaction and water-related side reactions while physically inhibiting the growth of zinc dendrites; the zinc electrode directly participates in the synthesis of bacterial cellulose through in-situ polymerization, achieving close fitting with the electrode surface. This close combination not only forms a stable interface conducive to the rapid transmission of zinc ions, but also significantly inhibits the activity of water molecules due to the presence of a large number of polymer molecules at the interface, thereby effectively slowing down the occurrence of side reactions such as the hydrogen evolution reaction. In addition, the zinc electrode undergoes a reduction reaction before electrochemical cycling, completing chemical polishing of the surface, eliminating the surface passivation layer, and exposing a large number of highly active zinc sites, providing favorable conditions for the uniform deposition and dissolution of initial zinc. The excellent interface combination and the polished zinc surface work together to provide an extremely low surface energy barrier for the nucleation of zinc, inducing zinc to preferentially grow along the (002) crystal plane, thereby achieving uniform deposition and stripping of zinc, and significantly improving the stability and cycle life of the zinc negative electrode.

[0008] The object of the present invention is achieved through the following technical solutions:

[0009] The present invention provides a metal negative electrode material with a surface in-situ generated bacterial cellulose protective layer, and the material has a three-layer structure system of "metal matrix layer - interface layer - functional layer"; the functional layer is a biosynthetic functional layer with a three-dimensional nano-network structure, and the interface layer is a chemical bonding interface layer formed between the metal matrix layer and the biosynthetic functional layer.

[0010] As an embodiment, the metal matrix layer is a single metal or an alloy composed of single metal elements; the single metals include zinc, aluminum, iron, magnesium, tin, and copper. In some embodiments, the metal matrix layer is a zinc single metal or an alloy.

[0011] As an embodiment, for the biosynthetic functional layer with a three-dimensional nano-network structure, the biosynthetic functional layer is a product of bacterial biosynthesis in a culture medium, has a three-dimensional nano-network structure, and contains rich hydroxyl functional groups.

[0012] As an embodiment, during the in-situ polymerization process, bacteria undergo an oxidation reaction on the metal matrix to generate bacterial cellulose, and the metal and bacterial cellulose are tightly combined at the interface to form a firmly bonded interface conducive to rapid ion transmission, that is, an interface layer is formed.

[0013] The present invention also relates to a preparation method of a zinc metal negative electrode material with a bacterial cellulose protective layer generated in situ on the surface, which is prepared by in-situ synthesis of bacteria using a biological method.

[0014] The biological method uses the natural synthesis ability of bacteria themselves, and relies on β-D-glucose monomers to form polymers through β-1,4-glycosidic bonds. In some implementation examples, the bacteria used is Komagataeibacter sucrofermentans. The in-situ synthesis is that after the zinc sheet is placed in the bacterial solution, a reduction reaction occurs on the surface of the highly active zinc sheet, and the bacteria undergo an in-situ polymerization process on the zinc sheet surface, forming bacterial cellulose that tightly binds to the zinc electrode surface, and a thin natural 3D network cross-linked protective layer structure is loaded on the zinc electrode surface. Technologically, the present invention realizes the short-process preparation and green and pollution-free preparation of the zinc negative electrode interface protective layer through the technology of in-situ synthesis of bacteria by biological methods. At the same time, in terms of structure, not only is the physical and mechanical properties of the protective layer less damaged, but also the problem of poor interfacial bonding effect between the protective layer and zinc is effectively solved, realizing the surface polishing of the zinc negative electrode and the in-situ synthesis of the protective layer. In addition, bacterial cellulose forms a complex and fine three-dimensional cross-linked network structure with a large number of hydroxyl groups on the zinc surface, effectively inhibiting the hydrogen evolution reaction and water-related side reactions of the zinc anode, which is beneficial to the reversible deposition and stripping of zinc.

[0015] As an implementation example, the preparation method of the zinc negative electrode material with a bacterial cellulose protective layer generated in situ on the surface includes the following steps:

[0016] S1. After the bacterial medium is sterilized, the bacterial mother liquor of (Komagataeibacter sucrofermentans) is added, and it is cultured statically at a constant temperature;

[0017] S2. The metal substrate is placed in the medium added with the bacterial mother liquor, and a bacterial cellulose coating layer is generated on the metal substrate surface through in-situ polymerization;

[0018] S3. The metal sheet is taken out, soaked and / or rinsed with deionized water, soaked and / or rinsed with absolute ethanol, and after vacuum drying, a metal negative electrode material with a bacterial cellulose protective layer on the surface is obtained.

[0019] In step S1, due to the use of a biological method to prepare bacterial cellulose by using the synthesis ability of bacteria themselves, the synthesis ability of bacterial cellulose is closely related to the concentration of the bacterial solution. And a metal substrate such as a zinc sheet itself has a certain antibacterial effect, so the bacterial mother liquor needs to be added and cultured for a period of time, and the zinc sheet can be put in after the concentration of the bacterial solution is increased to a certain level to improve the reaction rate.

[0020] In step S2, for in-situ polymerization, after putting a metal matrix such as a zinc sheet into the bacterial solution, a reduction reaction occurs on the surface of the highly active zinc sheet, and the bacteria undergo an in-situ polymerization process on the zinc sheet surface. During the in-situ polymerization process, the zinc negative electrode directly participates, a reduction reaction occurs on the surface to generate free electrons, inducing the bacteria to undergo an oxidation reaction on the zinc sheet to generate bacterial cellulose. Zinc and bacterial cellulose are tightly combined at the interface, and the surface is continuously cross-linked to form a bacterial cellulose network, finally in-situ generating a highly stable zinc negative electrode material with a bacterial cellulose protective layer.

[0021] As an implementation example, in step S1, the formula of the bacterial medium is: dissolve 100 g of glucose and 10 g of yeast extract in every 1000 mL of deionized water.

[0022] As an implementation example, in step S1, the sterilization is steam sterilization at 110 - 130 °C for 1 - 60 minutes. In some specific implementation examples, heat up to 121 °C and steam sterilize for 20 minutes.

[0023] As an implementation example, in step S1, the volume ratio of the added bacterial mother liquor is 5% - 20% of the medium.

[0024] As an implementation example, in step S1, the constant-temperature static culture is static culture in a constant-temperature incubator at 28 ± 0.5 °C for 3 - 10 days. To avoid contamination by miscellaneous bacteria, the medium before culture needs to be sterilized at high temperature, and the operation process is completed entirely in a sterile operating table. 28 °C is the most suitable environmental temperature for bacterial growth. To shorten the culture cycle, the proportion of the added bacterial mother liquor needs to exceed 5%, and the culture days need to exceed 3 days. To avoid waste and excessive bacterial concentration corroding the zinc sheet, the proportion of the added bacterial mother liquor should not exceed 20%, and the culture days should not exceed 10 days.

[0025] As an implementation example, in step S2, for a metal matrix such as a zinc sheet, use sandpaper to polish it to 1500 - 7000 mesh to remove part of the oxide layer on the surface in advance. Since a reduction reaction will occur on the zinc sheet during the in-situ polymerization process, the thickness of the used zinc sheet cannot be lower than 30 μm to prevent excessive consumption of zinc during the reaction. The zinc sheet placed in the bacterial solution can be immersed or placed on the liquid surface.

[0026] As an implementation example, in step S2, a metal matrix such as a zinc sheet is directly immersed in the bacterial solution to obtain BC@Zn modified on both sides; or use an inert substance such as polyimide tape to protect one side of the metal matrix such as a zinc sheet, and remove the inert substance after the culture ends to obtain BC@Zn modified on one side. As a new biosynthetic method, the surface modification scheme of one side or both sides can be selected by the method of protecting with an inert material.

[0027] As an implementation, in step S3, the soaking time in deionized water is 3 - 15 minutes, and the number of rinsing times is 0 - 5 times.

[0028] As an implementation, in step S3, the soaking time in absolute ethanol is 3 - 15 minutes, and the number of rinsing times is 0 - 5 times.

[0029] As an implementation, in step S3, the residual culture medium and bacteria on the surface of BC@Zn are not cleaned, and it is necessary to soak and rinse with deionized water and absolute ethanol. To avoid secondary corrosion of zinc metal, the soaking time and number of times of cleaning need to be controlled.

[0030] As an implementation, in step S3, the temperature of vacuum drying is 40 - 60 °C, and the drying time is 1 - 4 hours. To avoid oxidation of zinc metal, the drying process needs to be carried out in a vacuum environment.

[0031] As an implementation, the use of the foregoing metal negative electrode material, or the metal negative electrode material prepared according to the foregoing method.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1) The raw materials for making the present invention are cheap and pollution-free, and the bacteria, culture medium and synthesized bacterial cellulose used are all non-toxic and environmentally friendly; by the technology of in-situ synthesis of bacteria by biological methods, a zinc negative electrode material with a bacterial cellulose protection layer in-situ generated on the surface is prepared. The method is simple, the process is stable, the synthesis route is simple, the process is clean and environmentally friendly, and the preparation process is short. It can realize the short-process preparation of the zinc negative electrode interface protection layer in a mild environment and can be used for large-scale production.

[0034] 2) The synthesized bacterial cellulose in the present invention forms an ultra-thin natural 3D network cross-linked protection structure on the surface of zinc metal. The special cross-linked structure endows the cellulose diaphragm with ideal mechanical properties, excellent hydrophilicity and uniform pore structure; bacterial cellulose contains rich hydroxyl functional groups, and the hydrophilic hydroxyl groups form a strong hydrogen bond network with water molecules, reducing the free water in the electrolyte, lowering the activity of the hydrogen evolution reaction, effectively inhibiting the hydrogen evolution reaction and the water-related side reaction of the zinc anode, and being beneficial to the reversible deposition and stripping of zinc.

[0035] 3) The zinc anode material with a bacterial cellulose protective layer synthesized in the present invention is not a simple physical composite of bacterial cellulose and the zinc anode. During the in-situ polymerization process, the zinc anode directly participates, and a reduction reaction occurs on the surface to generate free electrons, inducing the oxidation reaction of bacteria on the zinc sheet to produce bacterial cellulose. Zinc and bacterial cellulose are tightly bonded at the interface, providing a firmly bonded interface that is conducive to rapid ion transport. There is a complex and delicate three-dimensional cross-linked bacterial cellulose with a large number of hydroxyl groups on the interface surface. Its three-dimensional porous structure can evenly distribute zinc ions, reduce local overpotential, and thus inhibit the formation of dendrites; by reducing the bond energy between zinc ions and anions and solvated free water, the side reaction between the electrolyte and the zinc anode is further reduced; its hydrophilic surface can promote the infiltration of the electrolyte and improve the ion transport efficiency; its high crystallinity and hydrogen bond network can improve the overall stability of the separator; by inhibiting dendrite growth and side reactions, the cycle life of the zinc-ion battery is significantly improved.

[0036] 4) Compared with the scheme of constructing a bacterial cellulose coating layer on the surface of metallic zinc foil by electrophoretic deposition, the biological process of the present invention is simple, the equipment is simple and the energy consumption is low, and the process is green and environmentally friendly; the bacteria grow in-situ, and the cellulose fibers can form a three-dimensional network structure on the zinc surface, having a denser "metal matrix layer - interface layer - functional layer" three-layer structure system, which improves the interface stability; moreover, the biological method relies on bacterial metabolism to directly synthesize cellulose, without chemical additives, and the material has higher purity, which is more in line with the trend of green manufacturing; that is, on the premise of avoiding complex processes and chemical pollution, a highly cohesive, structurally uniform and environmentally friendly bacterial cellulose protective layer is constructed on the zinc surface through biological in-situ synthesis technology, thereby long-term inhibiting dendrite growth and side reactions and improving the cycle stability of the zinc anode.

[0037] 5) Compared with the scheme of modifying a phosphorylated bacterial cellulose coating on the zinc anode surface by the drop-coating method, the biological in-situ growth of the present invention directly forms a three-dimensional network structure of cellulose through bacterial metabolism, forming a stronger physical-chemical binding force with the zinc substrate, and having a denser "metal matrix layer - interface layer - functional layer" three-layer structure system; the in-situ grown cellulose forms a uniformly covered nanofiber network through bacterial self-assembly, which can adapt to the zinc surface morphology and effectively inhibit dendrite penetration; moreover, the biological method of the present invention can achieve large-area uniform film formation by regulating culture conditions (such as temperature, pH), which is more suitable for large-scale production. Description of the Drawings

[0038] By reading the detailed description of the non-limiting embodiments with reference to the following drawings, other features, objects and advantages of the present invention will become more apparent:

[0039] Figure 1 It is a process flow chart of the biological method of bacterial in-situ synthesis;

[0040] Figure 2 SEM images (20 μm) of polished pure zinc foil and zinc foil with a bacteriocellulose protective layer in-situ formed on the surface;

[0041] Figure 3 SEM images (200 nm) of zinc foil with a bacteriocellulose protective layer in-situ formed on the surface;

[0042] Figure 4 SEM images (10 μm) of the cross-section of zinc foil with a bacteriocellulose protective layer in-situ formed on the surface; specifically, the side morphology of the zinc negative electrode with in-situ grown bacteriocellulose protective layer at 2500-fold magnification;

[0043] Figure 5 XRD patterns of polished pure zinc foil and zinc foil with a bacteriocellulose protective layer in-situ formed on the surface;

[0044] Figure 6 Internal resistance graph of the symmetric cell of zinc foil with a bacteriocellulose protective layer in-situ formed on the surface;

[0045] Figure 7 Chronoamperometry test graph of the symmetric cell of zinc foil with a bacteriocellulose protective layer in-situ formed on the surface;

[0046] Figure 8 Tafel curve of the symmetric cell of zinc foil with a bacteriocellulose protective layer in-situ formed on the surface;

[0047] Figure 9 Long cycle performance graph of the symmetric cell of zinc foil with a bacteriocellulose protective layer in-situ formed on the surface;

[0048] Figure 10 Rate performance graph of the symmetric cell of zinc foil with a bacteriocellulose protective layer in-situ formed on the surface. Specific implementation mode

[0049] The present invention will be described in detail below in conjunction with the embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that those of ordinary skill in the art can make several adjustments and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0050] Example 1

[0051] In this example, a zinc negative electrode material with a bacteriocellulose protective layer in-situ formed on the surface was prepared using a culture solution and zinc flakes as raw materials, and the preparation method was biological in-situ synthesis by bacteria, as Figure 1 shown:

[0052] (1) Prepare a bacterial culture medium using 1000 mL of deionized water, 100 g of glucose, and 10 g of yeast extract (LP0021B, purchased from OXOID

[0053] ). Place the culture medium in a steam sterilizer, heat it to 121 °C, and sterilize for 20 minutes. In a laminar flow hood, mix 0.5 mL of the Komagataeibacter sucrofermentans (DSM 15973, Leibniz Institute DSMZ - German Collection of Microorganisms and Cell Cultures) bacterial mother liquor with 10 mL of the bacterial culture medium, and place it in a constant temperature incubator for static culture at 28 °C for 7 days.

[0054] (2) Polish a zinc sheet with a thickness of 0.03 mm to 1500 mesh using sandpaper, and cut the zinc sheet into circular pieces with a diameter of 12 mm. Place the cut zinc sheets under an ultraviolet lamp for sterilization, and place them on the liquid surface of the cultured bacterial solution in a laminar flow hood, then put them back into the constant temperature incubator for continued culture at 28 °C.

[0055] (3) After the zinc sheets are taken out after 9 days of static culture in the bacterial solution, first rinse them three times with deionized water, then soak them for 10 minutes, and then soak them in absolute ethanol for 5 minutes. Place them in a vacuum oven and dry at 50 °C for 2 hours to obtain zinc foil anodes BC@Zn with a bacterial cellulose protective layer on the surface. Its surface morphology is as shown in Figure 2 、 Figure 3 , and the cross - sectional morphology is as shown in Figure 4 .

[0056] Figure 5 is the XRD pattern of the zinc foil material with a bacterial cellulose protective layer in - situ generated on the surface. As can be seen from Figure 5 , only the characteristic peaks of zinc are present in the BC@Zn material, indicating that this process will not change the crystal structure of the zinc anode or generate other phases.

[0057] Example 2

[0058] (1) Prepare a bacterial culture medium using 1000 mL of deionized water, 100 g of glucose, and 10 g of yeast extract as the standard formula. Place the culture medium in a steam sterilizer, heat it to 121 °C, and sterilize for 20 minutes. In a laminar flow hood, mix 0.5 mL of the Komagataeibacter sucrofermentans bacterial mother liquor with 10 mL of the bacterial culture medium, and place it in a constant temperature incubator for static culture at 28 °C for 7 days.

[0059] (2) Polish the zinc sheet with a thickness of 0.03 mm to 1500 mesh using sandpaper, and cut the zinc sheet into circular pieces with a diameter of 12 mm. Place the cut zinc sheets under an ultraviolet lamp for sterilization, immerse them in the cultured bacterial solution in a laminar flow hood, and then put them back into the constant temperature incubator for continued cultivation at 28 °C.

[0060] (3) Take out the zinc sheets after static cultivation in the bacterial solution for 3 days, first rinse them three times with deionized water, then soak them for 10 minutes, and then soak them in absolute ethanol for 5 minutes. Place them in a vacuum oven and dry them at 50 °C for 2 hours to obtain zinc sheet anodes BC@Zn with a bacterial cellulose protective layer on the surface.

[0061] Use a CR2023 type battery case and corresponding spring washer (Canrd), a glass fiber separator with a diameter of 16 mm and a width of (Whatman) as the separator, and 2M ZnSO4 solution as the electrolyte. The zinc sheet BC@Zn with a bacterial cellulose protective layer on the surface prepared is used as both the positive and negative electrode materials to assemble a symmetric button battery.

[0062] Figures 6 - 8 Respectively, are the internal resistance diagram, chronoamperometry test diagram, and Tafel curve of the zinc symmetric battery made of the zinc foil material with a bacterial cellulose protective layer generated in situ on the surface. As Figure 6 can be seen, compared with the battery assembled with the zinc sheets obtained by the preparation method of the present invention, the internal resistance of the zinc ion battery constructed with this BC@Zn material is significantly reduced. As Figure 7 can be seen, compared with the battery assembled with the zinc sheets obtained by the preparation method of the present invention, three-dimensional diffusion dominates during zinc deposition in the zinc ion battery constructed with this BC@Zn material, achieving uniform zinc deposition. As Figure 8 can be seen, compared with the battery assembled with the zinc sheets obtained by the preparation method of the present invention, the zinc ion battery constructed with this BC@Zn material has a more positive corrosion potential and a smaller corrosion current density, the zinc negative electrode has stronger corrosion resistance, and the anti-corrosion effect is better.

[0063] Example 3

[0064] (1) Prepare a bacterial culture medium with 1000 mL of deionized water, 100 g of glucose, and 10 g of yeast extract as the standard formula. Place the culture medium in a steam sterilizer, heat it to 121 °C, and sterilize it for 20 minutes. Mix 2 mL of the Komagataeibacter sucrofermentans bacterial mother liquor and 10 mL of the bacterial culture medium in a laminar flow hood, and place them in a constant temperature incubator for static cultivation at 28 °C for 5 days.

[0065] (2) Use sandpaper to polish a 0.05-mm-thick zinc sheet to 7000 mesh, and cut the zinc sheet into circular pieces with a diameter of 12 mm. Place the cut zinc sheets and polyimide tape under an ultraviolet lamp for sterilization. Stick the polyimide tape on one side of the zinc sheet in a laminar flow hood, immerse it in the cultured bacterial solution, and then put it back into the constant temperature incubator for continued cultivation at 28 °C.

[0066] (3) After the zinc sheets are taken out after static cultivation in the bacterial solution for 5 days, first rinse them three times with deionized water and then soak them for 10 minutes. After removing the polyimide tape, soak them in absolute ethanol for 5 minutes, and put them into a vacuum oven to dry at 50 °C for 2 hours to obtain zinc sheet anodes BC@Zn with a bacterial cellulose protective layer on the surface. Among them, the surface morphology of the zinc foil with a bacterial cellulose protective layer in-situ generated on the surface is as Figure 2 shown.

[0067] Figures 3 - 4 , Figures 9 - 10 are the SEM image, cross-sectional SEM image, long cycle performance image, and rate performance image of the zinc foil material with a bacterial cellulose protective layer in-situ generated on the surface (prepared zinc symmetric cells were tested). As can be seen from Figure 3 , there are a large number of three-dimensional cross-linked and intertwined nanocelluloses on the surface of the zinc sheet. These bacterial celluloses can uniformly distribute zinc ions, reduce local overpotential; can reduce the free water in the electrolyte, lower the activity of the hydrogen evolution reaction; and can promote the infiltration of the electrolyte, improve the ion transport efficiency; its high crystallinity and hydrogen bond network can improve the overall stability of the separator. As can be seen from Figure 4 , zinc and bacterial cellulose are tightly combined at the interface, providing a firmly bonded interface conducive to rapid ion transport; and due to the presence of a large number of polymer molecules at the interface, the activity of water molecules is greatly inhibited, thus inhibiting the occurrence of side reactions. As can be seen from Figure 9 , at a current density of 1 mA cm -2 , 1 mA h cm -2 , the BC@Zn material synthesized by the preparation method of the present invention exhibits an ultra-long cycle stability of more than 330 h. Figure 10 It reflects that when the current changes, the BC@Zn material synthesized by the preparation method of the present invention not only has a smaller polarization but also shows the most stable response.

[0068] Example 4

[0069] (1) Prepare a bacterial culture medium using 1000 mL of deionized water, 100 g of glucose, and 10 g of yeast extract as the standard formula. Place the culture medium in a steam sterilizer, heat it to 121 °C, and sterilize for 20 minutes. In a laminar flow hood, mix 2 mL of the Komagataeibacter sucrofermentans bacterial mother liquor with 10 mL of the bacterial culture medium, and place it in a constant temperature incubator for static culture at 28 °C for 5 days.

[0070] (2) Use sandpaper to polish a 0.05-mm-thick zinc sheet to 7000 mesh, and cut the zinc sheet into circular pieces with a diameter of 14 mm. Place the cut zinc sheets and polyimide tape under an ultraviolet lamp for sterilization. In a laminar flow hood, stick polyimide tape on one side of the zinc sheet, immerse it in the cultured bacterial solution, and then place it back in the constant temperature incubator for continued culture at 28 °C.

[0071] (3) After the zinc sheets are taken out after 5 days of static culture in the bacterial solution, rinse them three times with deionized water first and then soak for 10 minutes. After removing the polyimide tape, soak them in absolute ethanol for 5 minutes, and place them in a vacuum oven to dry at 50 °C for 2 hours to obtain zinc sheet anodes BC@Zn with a bacterial cellulose protective layer on the surface.

[0072] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various deformations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A metal negative electrode material with an in-situ bacterial cellulose protective layer formed on the surface, characterized in that: The material has a three-layer structural system of "metal matrix layer-interface layer-functional layer"; the functional layer is a biosynthetic functional layer with a three-dimensional nano-network structure, and the interface layer is a chemically bonded interface layer formed between the metal matrix layer and the biosynthetic functional layer.

2. The metal negative electrode material according to claim 1, characterized in that: The metal matrix layer is a single metal or an alloy composed of single metal elements; the single metal includes zinc, aluminum, iron, magnesium, tin, and copper.

3. The metal negative electrode material according to claim 1, characterized in that: The biosynthetic functional layer is a product of biosynthesis by bacteria in a culture medium, has a three-dimensional nano-network structure, and contains abundant hydroxyl functional groups.

4. The metal negative electrode material according to claim 3, characterized in that: During the in-situ polymerization process, bacteria undergo an oxidation reaction on the metal substrate to generate bacterial cellulose, and the metal and bacterial cellulose are tightly combined at the interface to form an interface layer.

5. A method for preparing a metal negative electrode material according to claim 1, characterized in that: The method comprises the following steps: S1. After the bacterial culture medium is sterilized, bacterial mother solution is added and cultured statically at a constant temperature; S2, placing the metal substrate in a culture medium with bacterial mother solution added thereto, and generating a bacterial cellulose coating layer on the surface of the metal substrate through in-situ polymerization; S3. Take out the metal sheet, soak and / or rinse it with deionized water, soak and / or rinse it with anhydrous ethanol, and vacuum dry it to obtain a metal negative electrode material with a bacterial cellulose protective layer on the surface.

6. The preparation method according to claim 5, characterized in that: In step S1, at least one of the following technical features is also included: A1. The formula of bacterial culture medium is: dissolve 100 g glucose and 10 g yeast extract in every 1000 mL deionized water; A2. The sterilization is performed by heating the temperature to 110-130°C and steam sterilizing for 1-60 minutes; A3. The volume ratio of the bacterial mother solution added is 5%-20% of the culture medium; A4. The constant temperature static culture is a constant temperature static culture at 28±0.5°C for 3-10 days.

7. The preparation method according to claim 5, characterized in that: In step S2, at least one of the following technical features is also included: B1. The metal substrate is polished with 1500-7000 grit sandpaper; B2. The metal piece placed in the culture medium is immersed in the liquid or placed on the liquid surface.

8. The preparation method according to claim 7, characterized in that: The metal substrate is immersed in a culture medium to obtain BC@Zn with both sides modified; or an inert substance is used to protect one side of the metal substrate, and after the culture is completed, the inert substance is removed to obtain BC@Zn with one side modified; the inert substance comprises a polyimide tape.

9. The preparation method according to claim 5, characterized in that: In step S3, at least one of the following technical features is also included: C1. Soaking time in deionized water is 3-15 minutes, and the number of rinses is 0-5 times; C2, the soaking time of anhydrous ethanol is 3-15 minutes, and the number of rinses is 0-5 times; C3. The vacuum drying temperature is 40-60°C and the drying time is 1-4 hours.

10. A use of the metal negative electrode material according to claims 1-4, or the metal negative electrode material prepared by the method according to claims 5-9, characterized in that: Used to modify and optimize battery materials.

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