Bacterial cellulose modified zinc metal negative electrode and preparation method and application thereof

Abstract

This invention discloses a bacterial cellulose-modified zinc metal anode, its preparation method, and its application, belonging to the field of zinc-ion batteries. The bacterial cellulose-modified zinc metal anode comprises zinc metal and a bacterial cellulose layer coated on the surface of the zinc metal. This invention, by coating the zinc metal surface with a uniform bacterial cellulose coating, avoids direct contact between the zinc metal and the electrolyte, reduces side reactions, and allows the -COOH and -OH groups of the bacterial cellulose coating to readily adsorb Zn. 2+ , making Zn 2+ The distribution becomes more uniform, inducing Zn 2+ Uniform deposition of Zn inhibits the growth of zinc dendrites; on the other hand, the bacterial cellulose layer has a three-dimensional porous structure, which can reduce the growth of Zn. 2+ Transport barriers promote zinc deposition and dissolution, which is beneficial for increasing the Zn content inside zinc batteries. 2+ Improve transmission efficiency and structural stability, thereby enhancing the cycle stability and lifespan of aqueous zinc-ion batteries.

Description

Technical Field

[0001] This invention relates to the field of zinc-ion battery technology, specifically to a bacterial cellulose-modified zinc metal anode, its preparation method, and its application. Background Technology

[0002] With the ever-increasing demand for energy, traditional fossil fuels are facing depletion. The development and research of renewable and clean energy sources such as solar and wind power have become inevitable. However, the application of these renewable energy sources is limited by climate, time, space, and geographical conditions, hindering their development. In contrast, rechargeable batteries have shown advantages in stability and convenient energy storage. Due to their long cycle life, high energy density, and high rechargeability, lithium-ion batteries dominate electric vehicles and portable electronic devices. However, the high price of lithium metal leads to high production costs for lithium-ion batteries, and the limited reserves of lithium in the Earth's crust prevent them from meeting the growing demand for energy storage devices. Zinc (Zn) metal stands out among other alkali metals due to its high theoretical capacity (820 mA·h / g), low plating / stripping potential, and ease of processing, becoming one of the key research directions for sustainable energy storage systems. Zinc-based batteries with zinc as the negative electrode, such as zinc-air batteries, Zn-V₂O₅ batteries, and Zn-MnO₂ batteries, have been extensively studied. More importantly, its high conductivity, high power density, high stability and safety in water lay the foundation for aqueous zinc-ion batteries to become a key research direction in the future.

[0003] However, aqueous zinc-ion batteries also have some problems. Dendrite formation and interfacial side reactions hinder their practical application, severely affecting battery stability and lifespan, and easily leading to battery failure. Severe dendrite problems can puncture the separator and cause short circuits, and even result in the formation of "dead zinc" (fractured dendrites). Corrosion of zinc metal leads to battery capacity degradation, reduces the reactive specific surface area of ​​the zinc anode, and decreases charging efficiency. In addition, inert corrosion substances generated on the electrode surface can hinder Zn... 2+ Transport issues reduce the reversibility of the negative electrode. To address these existing problems, researchers have proposed strategies to improve the stability of the traditional solid-liquid interface of zinc negative electrodes from different perspectives by analyzing the interfacial dendrite growth mechanism. For example, some researchers have introduced a porous nano-CaCO3 coating on the zinc metal surface. The high porosity makes it easy for the electrolyte to penetrate, thereby promoting the formation of a uniform electrolyte flux on the negative electrode surface. However, inorganic coatings are usually applied to the negative electrode surface with a binder, and the uneven contact between the nanoparticles and the binder can affect the Zn... 2+ The uniformity of transport affects the deposition uniformity of the zinc anode. Furthermore, scientists have used polymer coatings such as polyacrylonitrile and polyvinyl chloride to coat the Zn anode surface to optimize Zn deposition. 2+Uniformity of zinc ion deposition. For example, Chinese patent CN112490396A discloses a zinc anode, its preparation method, and an aqueous zinc-ion battery. The zinc anode includes a zinc sheet and a modified polyacrylonitrile coating on the surface of the zinc sheet. The modified polyacrylonitrile in the coating is obtained by pre-oxidizing polyacrylonitrile at a temperature of 150–500°C. In this invention, polyacrylonitrile is pre-oxidized at 150–500°C. The resulting modified polyacrylonitrile has abundant polar bonds, such as NH bonds, on its surface. These polar bonds guide the uniform deposition of zinc ions, thereby inhibiting dendrite growth. The organic coating formed based on the modified polyacrylonitrile protects the zinc anode from electrolyte corrosion. A uniform coating is beneficial for Zn… 2+ Uniform transport, but dense surface coating will affect Zn 2+ The transmission dynamics are hindered, increasing the battery's internal resistance and causing unnecessary energy loss.

[0004] Based on this, develop a method that can guide Zn 2+ Uniform deposition, suppression of dendrite growth, and improvement of Zn 2+ The zinc metal anode with high transmission efficiency is of great significance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, one objective of this invention is to provide a bacterial cellulose-modified zinc metal anode. By coating the zinc metal surface with a uniform bacterial cellulose coating, the uniform network structure and surface functional groups not only optimize Zn but also enhance its overall performance. 2+ Uniform transport, inducing Zn 2+ Uniform deposition can also reduce Zn content through a three-dimensional porous structure. 2+ Transport barriers promote zinc deposition and dissolution, thereby improving the cycle stability of zinc-ion batteries.

[0006] The objective of this invention is achieved through the following technical solutions.

[0007] A bacterial cellulose-modified zinc metal anode comprises zinc metal and a bacterial cellulose layer coated on the surface of the zinc metal.

[0008] This invention involves coating a zinc metal surface with a uniform bacterial cellulose coating. This avoids direct contact between the zinc metal and the electrolyte, reduces side reactions, and allows the -COOH and -OH groups of the bacterial cellulose coating to readily adsorb Zn. 2+ , making Zn 2+ The distribution becomes more uniform, inducing Zn 2+ Uniform deposition of Zn inhibits the growth of zinc dendrites; on the other hand, the bacterial cellulose layer has a three-dimensional porous structure, which can reduce the growth of Zn. 2+ Transport barriers promote zinc deposition and dissolution, which is beneficial for increasing the Zn content inside zinc batteries.2+ Improve transmission efficiency and structural stability, thereby enhancing the cycle stability and lifespan of zinc-ion batteries.

[0009] The zinc metal anode modified with bacterial cellulose in this invention has the following characteristics: ① It can avoid direct contact between zinc metal and electrolyte, reducing side reactions; ② The negatively charged groups such as -COOH and -OH on the surface of the bacterial cellulose coating easily adsorb Zn. 2+ Optimize the Zn content in aqueous electrolyte 2+ Concentration distribution induces uniform Zn deposition and inhibits zinc dendrite growth; ③ Bacterial cellulose can self-assemble into a flexible continuous film through a three-dimensional hydrogen bond network. The orderly three-dimensional cross-linked network structure constructed from one-dimensional bacterial cellulose exhibits excellent thermal stability and mechanical strength, while also possessing good electrolyte wettability. After the electrolyte solution successfully wets the three-dimensional channels of the bacterial cellulose film, the traditional point-to-point contact method is transformed into a large-area contact, forming a stable three-dimensional ion / electron transport channel, ensuring Zn deposition. 2+ The rapid transport and high thermal safety of Zn help improve its thermal performance. 2+ ④ Bacterial cellulose has excellent biocompatibility and biodegradability, and extremely high strength and elasticity, providing a pathway to realize fully degradable Zn bio-batteries.

[0010] In this invention, the thickness of the bacterial cellulose layer can be 0.01 to 0.10 mm, preferably 0.05 mm.

[0011] In this invention, the preparation method of the bacterial cellulose-modified zinc metal anode includes the following steps:

[0012] S1. Surface pretreatment of zinc metal;

[0013] S2. The bacterial cellulose gel is uniformly coated on the pretreated zinc metal surface, and then dried and cured to obtain bacterial cellulose modified zinc metal;

[0014] S3. The bacterial cellulose-modified zinc metal is aged at room temperature and then the surface is polished to obtain the bacterial cellulose-modified zinc metal anode.

[0015] Preferably, in step S1, the specific operation of surface pretreatment is as follows: the zinc metal surface is polished with sandpaper, and then ultrasonically cleaned with anhydrous ethanol 3 to 5 times.

[0016] Preferably, in step S2, the concentration of the bacterial cellulose gel is ≥99%.

[0017] Preferably, in step S2, the coating process uses the following parameters: ambient temperature of 28-35°C, relative humidity of 70%-90%, coating speed of 2-4 m / min, and pressure of 0.1-0.3 MPa.

[0018] More preferably, in step S2, the coating process uses the following parameters: ambient temperature of 28°C, ambient relative humidity of 80%, coating speed of 3 m / min, and pressure of 0.2 MPa.

[0019] By controlling the coating conditions, the thickness of the bacterial fiber coating can be adjusted, and the bacterial cellulose can be evenly distributed on the zinc metal surface. After drying, curing, aging at room temperature, and surface polishing, the best modification effect can be obtained, forming a thin and stable protective film.

[0020] Preferably, the drying and curing temperature is 60–90°C and the time is 20–36 hours.

[0021] Another object of the present invention is to provide the application of the bacterial cellulose-modified zinc metal anode in an aqueous zinc-ion battery.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] (1) This invention achieves this by coating a uniform bacterial cellulose coating on the zinc metal surface, which avoids direct contact between the zinc metal and the electrolyte and reduces side reactions. At the same time, the -COOH and -OH groups of the bacterial cellulose coating easily adsorb Zn. 2+ , making Zn 2+ The distribution becomes more uniform, inducing Zn 2+ Uniform deposition of Zn inhibits the growth of zinc dendrites; on the other hand, the bacterial cellulose layer has a three-dimensional porous structure, which can reduce the growth of Zn. 2+ Transport barriers promote zinc deposition and dissolution, which is beneficial for increasing the Zn content inside zinc batteries. 2+ Improve transmission efficiency and structural stability, thereby enhancing the cycle stability and lifespan of aqueous zinc-ion batteries.

[0024] (2) The NH4VO3||Zn full cell based on the zinc metal anode of this invention, after 2500 stable cycles at a current density of 5 A / g, still maintains a specific capacity of 95 mAh / g, with a capacity retention of 90.48% and a coulombic efficiency of 96.8%, demonstrating good capacity retention and coulombic efficiency. The Zn||Zn symmetric cell based on the zinc metal anode of this invention, at a current density of 5 mA / cm², exhibits good capacity retention and coulombic efficiency. -2 The current density, charge / discharge time are 12 minutes each, and the specific capacity is 1 mAh cm⁻¹. -2 It exhibits stable cycling for over 550 hours, demonstrating good cycle stability. Attached Figure Description

[0025] Figure 1 This is a process flow diagram for manufacturing the bacterial cellulose-modified zinc metal anode of the present invention.

[0026] Figure 2 A schematic diagram of a button cell assembly for Zn||Zn symmetric cells and NH4VO3||Zn full cells;

[0027] Figure 3 This is a SEM image of the zinc metal anode modified with bacterial cellulose in Example 1.

[0028] Figure 4 This is a long-cycle diagram of a Zn||Zn symmetric cell based on a zinc metal anode modified with bacterial cellulose from Example 1 and a bare zinc sheet;

[0029] Figure 5 The cycling performance of the NH4VO3||Zn full cell based on the zinc metal anode modified with bacterial cellulose in Example 1 is shown in the figure.

[0030] Figure 6 The CV diagram is shown for the NH4VO3||Zn full cell based on the zinc metal anode modified with bacterial cellulose in Example 1. Detailed Implementation

[0031] The applicant will now provide a detailed description of the method of the present invention with reference to specific embodiments, in order to enable those skilled in the art to clearly understand the present invention. However, the following embodiments should not be construed in any way as limiting the scope of protection claimed in the present invention.

[0032] Example 1

[0033] like Figure 1 As shown, this embodiment provides a method for preparing a bacterial cellulose-modified zinc metal anode, including the following steps:

[0034] S1. Perform surface pretreatment on zinc metal. The specific treatment method is as follows: first, polish with 80-grit sandpaper for 2 minutes, then ultrasonically clean with 99% anhydrous ethanol 3-5 times, 1 minute each time;

[0035] S2. Wet the bottom of the zinc metal from step S1 with a small amount of anhydrous ethanol, then attach it tightly to the petri dish. Under the conditions of an ambient temperature of 28℃ and an ambient relative humidity of 80%, coat the zinc metal surface with a 99% concentration bacterial cellulose hydrogel with a thickness of 0.03mm at a coating speed of 3m / min and a pressure of 0.2MPa. Then place the coated zinc metal in an electric heating drying oven for drying and curing at a temperature of 85℃ for 24h.

[0036] S3. After drying, the zinc metal is placed at room temperature (25°C) and allowed to stand for 2 hours. Then, the surface is polished with 240-grit sandpaper for 2-3 times, 1 minute each time, to obtain the bacterial cellulose-modified zinc metal negative electrode (denoted as BC-coated zinc sheet).

[0037] Figure 3 This is a SEM image of the zinc metal anode modified with bacterial cellulose obtained in this embodiment. As can be seen from the image, the bacterial cellulose is uniformly distributed on the zinc metal surface, and the bacterial cellulose film has a three-dimensional porous structure.

[0038] Example 2

[0039] like Figure 1 As shown, this embodiment provides a method for preparing a bacterial cellulose-modified zinc metal anode, including the following steps:

[0040] S1. Perform surface pretreatment on zinc metal. The specific treatment method is as follows: first, polish with 80-grit sandpaper for 2 minutes, then ultrasonically clean with 99% anhydrous ethanol 3-5 times, 1 minute each time;

[0041] S2. Wet the bottom of the zinc metal from step S1 with a small amount of anhydrous ethanol, then attach it tightly to the petri dish. Under the conditions of an ambient temperature of 35℃ and an ambient relative humidity of 70%, coat the zinc metal surface with a 99% concentration bacterial cellulose hydrogel with a thickness of 0.03mm at a coating speed of 2m / min and a pressure of 0.1MPa. Then place the coated zinc metal in an electric heating drying oven for drying and curing at a temperature of 60℃ for 36h.

[0042] S3. Place the dried zinc metal at room temperature (25°C) for 2 hours to age, then polish the surface with 240-grit sandpaper 2-3 times, 1 minute each time, to obtain the bacterial cellulose modified zinc metal anode.

[0043] Example 3

[0044] like Figure 1 As shown, this embodiment provides a method for preparing a bacterial cellulose-modified zinc metal anode, including the following steps:

[0045] S1. Perform surface pretreatment on zinc metal. The specific treatment method is as follows: first, polish with 80-grit sandpaper for 2 minutes, then ultrasonically clean with 99% anhydrous ethanol 3-5 times, 1 minute each time;

[0046] S2. Wet the bottom of the zinc metal from step S1 with a small amount of anhydrous ethanol, then attach it tightly to the petri dish. Under the conditions of an ambient temperature of 32℃ and an ambient relative humidity of 85%, coat the zinc metal surface with a 99% concentration bacterial cellulose hydrogel with a thickness of 0.03mm at a coating speed of 4m / min and a pressure of 0.3MPa. Then place the coated zinc metal in an electric heating drying oven for drying and curing at a temperature of 90℃ for 20h.

[0047] S3. Place the dried zinc metal at room temperature (25°C) for 2 hours to age, then polish the surface with 240-grit sandpaper 2-3 times, 1 minute each time, to obtain the bacterial cellulose modified zinc metal anode.

[0048] Application examples

[0049] Button cells of Zn||Zn symmetric cells and NH4VO3||Zn full cells were prepared using the zinc metal anode modified with bacterial cellulose in Examples 1-3, and their electrochemical performance was tested.

[0050] The assembly flowchart of the Zn||Zn symmetric cell is as follows: Figure 2 As shown in the right figure, using glass fiber as the diaphragm and 2M ZnSO4 aqueous solution as the electrolyte, according to... Figure 2 As shown in the right figure, the negative electrode shell, BC-coated zinc sheet, separator, BC-coated zinc sheet, gasket, spring sheet and positive electrode shell are stacked in sequence to assemble a button cell.

[0051] The assembly flowchart of the NH4VO3||Zn full cell is as follows: Figure 2 As shown in the left figure, the preparation method of the positive electrode is as follows: (NH4)2V 10 O 25 • 8H₂O nanosheets were mixed with PVDF and Super P at a mass ratio of 7:2:1, NMP solvent was added, and the mixture was stirred until homogeneous. The mixture was then coated onto carbon paper and dried in a vacuum oven at 80°C for 24 hours. After cooling, it was cut into circular films with a diameter of 12 mm to obtain the positive electrode. Then, a BC-coated zinc sheet was used as the negative electrode, glass fiber as the separator, and 2M zinc trifluoromethanesulfonate as the electrolyte. Figure 2 The sequence shown in the left figure is used to assemble an NH4VO3||Zn button cell.

[0052] The assembled batteries were tested for electrochemical performance using a battery testing system.

[0053] Figure 4This is a long-cycle comparison graph of the Zn||Zn symmetric cell based on the zinc metal anode modified with bacterial cellulose in Example 1 and the bare zinc sheet Zn||Zn symmetric cell. As can be seen from the graph, the Zn||Zn symmetric cell based on the zinc metal anode modified with bacterial cellulose in Example 1 exhibits longer cycling performance at 5 mA cm⁻¹. -2 At a current density of 12 min for each charge and discharge time, 1 mAh cm⁻¹ -2 At specific capacity, it exhibits stable cycling for over 550 hours. Furthermore, the partial cycling diagram shows that, compared to a conventional bare zinc sheet Zn||Zn symmetric cell, the Zn||Zn symmetric cell based on the bacterial cellulose-modified zinc metal anode of Example 1 has essentially the same polarization voltage, but its voltage polarization is more stable, consistently maintaining a stable overpotential of 45mV, demonstrating stable long-cycle performance. This indicates that the bacterial cellulose-modified zinc metal anode of the present invention promotes Zn... 2+ Uniform deposition inhibits the growth of zinc dendrites and significantly improves cycle stability.

[0054] Figure 5 The graph shows the cycling performance of the NH4VO3||Zn full cell based on the zinc metal anode modified with bacterial cellulose in Example 1. As can be seen from the graph, the NH4VO3||Zn full cell based on the zinc metal anode modified with bacterial cellulose in Example 1, after 2500 stable cycles at a current density of 5 A / g, still maintains a specific capacity of 95 mAh / g, with a capacity retention of 90.48% and a coulombic efficiency of 96.8%, exhibiting good capacity retention and coulombic efficiency. The voltage-capacity curve also shows that during the initial cycling process, the capacity increases with the activation of the battery internally and the activation process of active material insertion. At 2000 cycles, the specific capacity of the fully charged battery still reaches 100 mAh / g, demonstrating excellent long-cycle performance and superior long-cycle capacity.

[0055] Figure 6 The figure shows the CV curve of the NH4VO3||Zn full cell based on the zinc metal anode modified with bacterial cellulose in Example 1. As can be seen from the figure, the potentials of the two oxidation peaks are approximately 0.7V and 1.0V, corresponding to VO3. - In the two oxidation processes, the potentials of the two reduction peaks are approximately 0.6V and 0.9V, with roughly the same peak spacing. Furthermore, the ratio of the currents from the two oxidation peaks to the currents from the reduction peaks is close to 1, indicating that the reaction has good reversibility. At this point, VO3... - The oxides were reduced to VO3. - .

[0056] 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 method for preparing a bacterial cellulose-modified zinc metal anode, characterized in that, Includes the following steps: S1. Surface pretreatment of zinc metal; S2. Bacterial cellulose gel is uniformly coated onto the pretreated zinc metal surface, and then dried and cured to obtain bacterial cellulose-modified zinc metal; the concentration of the bacterial cellulose gel is ≥99%; S3. The bacterial cellulose-modified zinc metal is aged at room temperature and then the surface is polished to obtain the bacterial cellulose-modified zinc metal anode. The bacterial cellulose-modified zinc metal anode comprises zinc metal and a bacterial cellulose layer coated on the surface of the zinc metal, wherein the thickness of the bacterial cellulose layer is 0.01~0.10 mm.

2. The method for preparing a bacterial cellulose-modified zinc metal anode according to claim 1, characterized in that, In step S1, the specific operation of surface pretreatment is as follows: polish the zinc metal surface with sandpaper, and then perform ultrasonic cleaning with anhydrous ethanol 3 to 5 times.

3. The method for preparing a bacterial cellulose-modified zinc metal anode according to claim 1, characterized in that, In step S2, the coating process uses the following parameters: ambient temperature of 28~35℃, relative humidity of 70%~90%, coating speed of 2~4m / min, and pressure of 0.1~0.3MPa.

4. The method for preparing a bacterial cellulose-modified zinc metal anode according to claim 3, characterized in that, In step S2, the coating process uses the following parameters: ambient temperature of 28°C, relative humidity of 80%, coating speed of 3 m / min, and pressure of 0.2 MPa.

5. The method for preparing a bacterial cellulose-modified zinc metal anode according to claim 1, characterized in that, The drying and curing temperature is 60~90℃, and the time is 20~36h.

6. The application of the bacterial cellulose-modified zinc metal anode prepared by the method of claim 1 in an aqueous zinc-ion battery.

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