A crystal-oriented reconstructed zinc anode, its preparation method and application

Abstract

This invention discloses a crystal-oriented reconstructed zinc anode, its preparation method, and its application. The preparation method of the crystal-oriented reconstructed zinc anode includes the following steps: (1) uniformly mixing an active material or its precursor, a solvent, and a polymer to obtain an electrospinning solution, and preparing a self-supporting electrode by electrospinning; (2) drying the self-supporting electrode obtained in step (1), and then attaching the self-supporting electrode to the top and bottom using a flexible substrate, and sintering it under pressure; (3) depositing zinc on the sintered self-supporting electrode in step (2) using an electrodeposition method. The zinc anode structure prepared by the crystal-oriented reconstructed zinc anode method of this invention is controllable, and it is easy to realize the in-situ composite of various active materials with the self-supporting electrode and the release of electrode stress. It can promote the directional reconstruction of zinc crystals along specific crystal planes, which is beneficial to improving the cycle life of the zinc anode and enhancing the electrochemical performance and cycle stability of zinc-based batteries.

Description

Technical Field

[0001] This invention belongs to the field of zinc battery technology, specifically relating to a crystal-oriented reconstructed zinc anode, its preparation method, and its application. Background Technology

[0002] Zinc-based batteries benefit from the high reserves of zinc metal, low cost, non-toxicity, ease of processing, and high energy density (5855 mAh cm⁻¹). -3 High stability and chemical compatibility in aqueous electrolytes, two-electron redox properties, and high negative electrode capacity (820 mAh g). -1 Zinc-based batteries have become the preferred choice for next-generation energy storage batteries. However, due to uneven nucleation, uncontrollable growth methods, and inconsistent interfacial ion flux, zinc anodes suffer from problems such as dendrite formation, corrosion, passivation, and deformation during the reaction process, which severely restricts the large-scale application of zinc-based batteries.

[0003] The crystal orientation of zinc determines the morphology and structure during zinc deposition. By controlling the zinc crystal orientation, the surface smoothness and coating density can be effectively improved to enhance cycle life. The anode crystal structure of rolled zinc metal foil is mainly oriented along the (101) crystal plane, which exhibits significant polarization during electrochemical reactions and is prone to dendrite growth. However, when zinc crystals are deposited along the (002) crystal plane, a uniform electric field can be formed, promoting the epitaxial growth of zinc to form a relatively smooth surface and obtaining an ideal zinc anode structure.

[0004] The stress distribution of the deposition substrate and the high lattice matching of the surface determine the deposition direction of zinc crystals. However, existing crystal orientation control techniques have significant limitations. They cannot simultaneously control the active material and substrate stress, making them unsuitable for large-scale application. Furthermore, they can only temporarily alleviate crystal orientation issues and cannot fundamentally solve the crystal reconstruction problem (Li, X. et al. ACS Nano 2021, 15, 9, 14631–14642).

[0005] Therefore, there is an urgent need to develop a method that can achieve the orientational reconstruction of zinc crystals along specific crystal planes to manufacture high-performance zinc anodes and promote their large-scale application in secondary zinc-based batteries. Summary of the Invention

[0006] To address the problems of poor bonding between the substrate and active material, excessive residual stress on the substrate, and imperfect crystal orientation methods in existing technologies, this invention proposes a crystal-oriented reconstructed zinc anode, its preparation method, and its application. This invention utilizes an integrated manufacturing method for high-lattice-matched active material and self-supporting electrode, along with an electrode stress release method, to achieve crystal-oriented reconstruction of the zinc anode through electrode deposition. This allows the zinc crystals to be oriented along specific crystal planes to obtain a smooth surface structure, improving the performance of the zinc anode and broadening its application in secondary zinc-based batteries.

[0007] This invention employs electrospinning to manufacture a self-supporting electrode with in-situ composite of highly lattice-matched active materials. Stress release of the electrode is achieved through stress transfer on a flexible substrate. The zinc crystal is oriented and reconstructed using an electrodeposition method, allowing the zinc crystal to grow along a specific crystal plane to obtain a smooth surface structure. This improves the performance of the zinc anode and promotes its application in secondary zinc-based batteries.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] A method for preparing a crystal-oriented reconstructed zinc anode includes the following steps:

[0010] (1) The self-supporting electrode is fabricated by electrospinning with high lattice matching active material in situ composite, specifically including: mixing the active material or the precursor of the active material, solvent and polymer to obtain an electrospinning solution, and preparing the self-supporting electrode by electrospinning.

[0011] (2) A method for pre-releasing stress of a self-supporting electrode is provided, which specifically includes: drying the self-supporting electrode obtained in step (1), then attaching the self-supporting electrode to the top and bottom with a flexible substrate, and sintering under pressure.

[0012] (3) Deposit zinc into the self-supporting electrode after sintering in step (2) using the electrodeposition method to obtain a crystal-oriented reconstructed zinc anode.

[0013] Preferably, the active material in step (1) has a hexagonal crystal system, wherein the size of the secondary axis direction in the unit cell is...

[0014] More preferably, the active material comprises any one or a mixture of hexagonal boron nitride (h-BN), hexagonal tungsten oxide (WO3), carbon nitride (g-C3N4), zinc oxide (ZnO), silicon carbide (SiC), and graphene; the concentration of the active material in the electrospinning solution is 1-10 wt%.

[0015] Preferably, the precursor of the active substance in step (1) is boric acid and dicyandiamine; the molar ratio of boric acid and dicyandiamine is 1:1-8:1; and the total concentration of boric acid and dicyandiamine in the electrospinning solution is 1-10 wt%.

[0016] Preferably, the solvent in step (1) is any one or a mixture of dimethylformamide, alcohol, deionized water, and N-methylpyrrolidone; the polymer is any one or a mixture of polyvinylpyrrolidone, polyacrylonitrile, polymethyl acrylate, and polyvinyl alcohol; and the concentration of the polymer in the electrospinning solution is 8-30 wt%.

[0017] Preferably, the flexible substrate in step (2) is any one of flexible hydrophilic carbon cloth, flexible carbon fiber felt, and flexible carbon mesh; the applied pressure ranges from 0.5 to 10 N; the sintering is performed at 200-500°C for 0.5-8 h under oxidizing conditions, or at 700-1200°C for 0.5-10 h under carbonizing conditions; the oxidizing conditions are performed in an air atmosphere; the carbonizing conditions use a nitrogen or argon atmosphere with a gas flow rate of 40-150 sccm.

[0018] Preferably, the electrodeposition method in step (3) is a two-electrode electrodeposition method with a self-supporting electrode as the working electrode and a zinc sheet as the counter electrode; or a three-electrode electrodeposition method with a self-supporting electrode as the working electrode, a platinum sheet or platinum mesh as the counter electrode, and Ag / AgCl as the reference electrode.

[0019] Preferably, the electrodeposition method in step (3) employs either the constant current method or the constant voltage method; the current density range of the constant current method is -0.5 to -100 mA cm⁻¹. -2 Capacity is 5-100mAh cm -2 The constant voltage method has a voltage range of -0.01 to -2V and a capacity of 5-100mAh cm⁻¹. -2 .

[0020] Preferably, the electrolyte used in the electrodeposition method in step (3) is a zinc salt solution; the zinc salt is any one of zinc sulfate, zinc chlorate, zinc acetate, and zinc trifluoromethanesulfonate, and the concentration of the zinc salt solution is 0.3-3 mol / L.

[0021] The crystal-oriented reconstructed zinc anode prepared by the above method.

[0022] The above-mentioned crystal-oriented reconstructed zinc anode is used in zinc-air batteries, zinc-air composite batteries, zinc-ion batteries, zinc-ion supercapacitors, and zinc flow batteries (zinc-based energy storage devices).

[0023] The key features of this invention are:

[0024] (1) Unlike traditional electrodes where the active material and conductive network are physically bonded, this invention proposes to grow highly lattice-matched active materials in situ on the surface of a self-supporting electrode using electrospinning, thereby improving the bonding ability and mass transfer rate between the active material and the conductive substrate. The electrode structure prepared based on the method proposed in this invention is controllable and easily tunable, facilitating the organic integration of various active materials with the self-supporting electrode, and enabling expanded applications in this field.

[0025] (2) This invention creatively proposes an electrode stress relief method, which solves the problem of excessive stress during the heat treatment of self-supporting electrodes. It can effectively improve the mechanical properties of the electrode, reduce residual stress, and promote the directional reconstruction of zinc crystals. The method proposed in this invention can realize the controllable regulation of the stress of self-supporting electrodes, is applicable to most self-supporting electrodes, and is highly operable, cost-controllable, and has a significant effect on electrode stress regulation. It is particularly suitable for large-scale applications of electrode stress regulation.

[0026] (3) The integrated manufacturing method and stress release method of high lattice matching active material and self-supporting electrode proposed in this invention can be used to prepare a high-performance deposition substrate that is conducive to guiding the directional reconstruction of zinc crystal. The directional reconstruction of zinc anode crystal can be achieved by electrodeposition, so that zinc crystal can be epitaxially grown along a specific crystal plane to obtain a smooth surface structure, thereby improving the performance of zinc anode and broadening its application in secondary zinc-based batteries.

[0027] (4) The zinc anode crystal orientation reconstruction method and the zinc anode prepared by the present invention can be used on a large scale in secondary zinc-based batteries such as zinc-air batteries, zinc-air composite batteries, zinc-ion batteries, zinc-ion supercapacitors, and zinc flow batteries. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the zinc anode crystal directional reconstruction method of the present invention.

[0029] Figure 2 The figures are finite element simulation diagrams of stress relief of self-supporting electrodes in Example 1 and Comparative Examples 1 and 2.

[0030] Figure 3 The diagram shows the mechanical performance test results of the self-supporting electrodes in Example 1 and Comparative Example 1.

[0031] Figure 4 The images show SEM images of the zinc anode reconstructed using crystal orientation in Example 1 and the zinc anode in Control Example 1.

[0032] Figure 5 The XRD patterns are of the zinc anode reconstructed using crystal orientation in Example 1 and the zinc anode in Control Example 1.

[0033] Figure 6 The graph shows the cycle performance of a symmetrical cell using a crystal-oriented reconstructed zinc anode in Example 1, a zinc anode in Comparative Example 1, and a commercial zinc foil.

[0034] Figure 7 The graph shows the cycle performance of the zinc-V2O5 battery using a crystal-oriented reconstructed zinc anode in Example 1 and a zinc anode in Control Example 1. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to the embodiments.

[0036] Compare with Example 1

[0037] In the control example, no active material was added. 3g of polyacrylonitrile was added to 30ml of dimethylformamide and stirred thoroughly for 24h to obtain a spinning solution. A self-supporting electrode membrane was prepared by electrospinning (electrospinning parameters were the same as in Example 1).

[0038] After electrospinning, the self-supporting electrode film is removed, dried, and cut into 15cm×10cm pieces. No substrate is used in the heat treatment. After oxidation at 280℃ for 2 hours, it is treated at 1000℃ for 2 hours in an argon atmosphere with an argon gas flow rate of 100sccm.

[0039] like Figure 2 , 3 As shown, the control example has higher surface stress and poorer mechanical properties.

[0040] The prepared self-supported electrode was cut into 12 cm diameter electrodes. A zinc sheet was used as the counter electrode, and the cut self-supported electrode was used as the working electrode. 2 mol / L zinc sulfate was used as the electrolyte, and an electrode was prepared at 5 mA cm⁻¹. -2 A zinc anode with crystal orientation reconstruction was obtained by electroplating at a current density for 4 hours.

[0041] like Figure 4 , 5 As shown, the control example has a crystal plane dominated by (101), which cannot achieve crystal orientation reconstruction. The electron microscope image shows an irregular dendritic morphology.

[0042] The control example performed poorly in both symmetrical and full-cell tests. Figure 6 , Figure 7 ).

[0043] Compare with Example 2

[0044] Comparative Example 2 used hexagonal boron nitride (h-BN) as the active material, and no stress release was performed during heat treatment. 0.62 g of boric acid, 0.42 g of dicyandiamine, and 3 g of polyacrylonitrile were added to 30 ml of dimethylformamide and stirred thoroughly for 24 h to obtain a spinning solution. A self-supporting electrode film was prepared by electrospinning (electrospinning parameters were the same as in Example 1).

[0045] After electrospinning, the self-supporting electrode film is removed, dried, and cut into 15cm × 10cm pieces. No substrate is used during heat treatment, and no stress release is performed. After oxidation at 260℃ for 2 hours, it is treated at 1000℃ for 2 hours under an argon atmosphere, with an argon gas flow rate of 100 sccm. Figure 2 , 3 As shown, the control example 2 has higher surface stress and poorer mechanical properties.

[0046] The electrodeposition and battery test parameters for Comparative Example 2 are the same as those for Comparative Example 1.

[0047] Example 1

[0048] Using hexagonal boron nitride (h-BN) as the active material, 0.62 g boric acid, 0.42 g dicyandiamine, and 3 g polyacrylonitrile were added to 30 ml dimethylformamide and stirred thoroughly for 24 h to obtain a spinning solution. A self-supporting electrode membrane was prepared by electrospinning.

[0049] The parameters for electrospinning are as follows: the injection pump speed is 0.08 ml / h, the applied voltage is 26 kV, and the distance between the needle and the collector is 12 cm.

[0050] After electrospinning, the self-supporting electrode film is removed, dried, and cut into 15cm × 10cm pieces. Using carbon cloth as a flexible substrate, a pressure of 4N is applied (e.g., ...). Figure 1 After oxidation at 280℃ for 2 hours, it was treated at 1000℃ for 2 hours under an argon atmosphere, with an argon gas flow rate of 100 sccm.

[0051] like Figure 2 , 3 As shown, the self-supporting electrode stress relief method proposed in this invention can effectively relieve electrode stress and reduce residual electrode stress.

[0052] The prepared self-supported electrode was cut into 12cm dendrites. A zinc sheet was used as the counter electrode, and the cut self-supported electrode was used as the working electrode. 2mol / L zinc sulfate was used as the electrolyte, and an electrode was prepared at 5mA cm⁻¹. -2 A zinc anode with crystal orientation reconstruction was obtained by electroplating at a current density for 4 hours.

[0053] like Figure 5 As shown, the proportion of (002) crystal planes in the zinc anode prepared by the crystal reconstruction method proposed in this invention is significantly higher than that in the control example, proving that the method proposed in this invention can achieve directional reconstruction of the zinc anode crystal along the (002) crystal plane.

[0054] from Figure 4 It can be seen that the zinc anode prepared by the method proposed in this invention has a regular planar structure that grows epitaxially along the fiber surface, while the control example has an irregular dendritic morphology.

[0055] The same zinc anode was prepared as the working electrode and counter electrode using the above method for the symmetrical cell (the zinc anode of the control example and the commercial zinc foil were tested using the same method).

[0056] like Figure 6 As shown, a symmetric cell based on crystal-oriented reconstructed zinc anode operates at 1 mA cm⁻¹. -2 Current density, 1 mAh cm⁻¹ -2The zinc anode with oriented crystal reconstruction can operate stably for 420 hours with an overpotential of only 20mV, while the symmetric battery with an unoriented zinc anode (Control Example 1) has a cycle life of only 100 hours, and the commercial zinc foil short-circuited after 60 hours. The test results demonstrate that the zinc anode with oriented crystal reconstruction has significantly improved deposition / stripping behavior and cycle stability, effectively suppressing zinc dendrites and preventing short circuits caused by puncturing the separator, thereby improving the safety and cycle life of zinc-based batteries.

[0057] from Figure 7 It can be seen that the zinc-V2O5 battery based on crystal-oriented reconstruction of the zinc anode can achieve a cycle life of up to 4000 cycles and a coulombic efficiency of nearly 100%, which is far superior to the zinc-V2O5 battery without crystal-oriented reconstruction.

[0058] The experimental results demonstrate that the in-situ composite method of self-supporting electrode and high lattice-matched active material proposed in this invention can manufacture a highly efficient and stable self-supporting electrode; electrode stress release can effectively release residual stress and reduce the zinc nucleation and diffusion barrier; based on this, the directional reconstruction of zinc anode crystals can be achieved through electrodeposition, improving electrode stability. Batteries based on the directional reconstruction of the zinc anode crystal exhibit better electrochemical performance and cycle life.

[0059] Example 2

[0060] This embodiment differs from Embodiment 1 in that hexagonal tungsten oxide (WO3) is used as the active material. 2.32g of hexagonal tungsten oxide powder and 3g of polyvinyl alcohol are added to 30ml of deionized water and stirred thoroughly for 24 hours to obtain a spinning solution. A self-supporting electrode membrane is prepared using electrospinning. After electrospinning, the self-supporting electrode membrane is removed, dried, and cut into 15cm × 20cm pieces. Flexible carbon fiber felt is used as the flexible substrate, and a pressure of 3N (e.g., ...) is applied. Figure 1 The self-supported electrode was oxidized at 280℃ for 2 hours, followed by treatment at 1000℃ for 2 hours under an argon atmosphere with an argon gas flow rate of 100 sccm. The prepared self-supported electrode was then cut into 12 cm diameter electrodes. A zinc sheet was used as the counter electrode, and the cut self-supported electrode served as the working electrode. 3 mol / L zinc acetate was used as the electrolyte, and the electrolyte was applied at 8 mA cm⁻¹. -2 A zinc anode with oriented crystal reconstruction was obtained by electroplating at a current density for 4 hours. The battery test parameters for Example 2 were the same as those for Example 1.

[0061] Example 3

[0062] This embodiment differs from Embodiment 1 in that graphene is used as the active material. A suspension containing 3g of graphene (8wt%) and 3g of polyvinyl alcohol are added to 30ml of deionized water and stirred thoroughly for 24 hours to obtain a spinning solution. A self-supporting electrode membrane is prepared by electrospinning. After electrospinning, the self-supporting electrode membrane is removed, dried, and cut into 15cm×15cm pieces. A flexible carbon mesh is used as a flexible substrate, and a pressure of 6N (e.g., ...) is applied. Figure 1 The self-supported electrode was oxidized at 280℃ for 2 hours, followed by treatment at 950℃ for 2 hours under an argon atmosphere with an argon gas flow rate of 100 sccm. The prepared self-supported electrode was then cut into 14 cm diameter electrodes. A zinc sheet was used as the counter electrode, and the cut self-supported electrode served as the working electrode. 2 mol / L zinc chloride was used as the electrolyte, and the electrolyte was applied at 10 mA cm⁻¹. -2 A zinc anode with oriented crystal reconstruction was obtained by electroplating at the current density for 2 hours. The battery test parameters for Example 3 were the same as those for Example 1.

[0063] Example 4

[0064] This embodiment differs from Example 1 in that g-C3N4 is used as the active material. 0.84g of dicyandiamine (a precursor to g-C3N4) and 3g of polyacrylonitrile are added to 30ml of dimethylformamide and stirred thoroughly for 24 hours to obtain a spinning solution. A self-supporting electrode membrane is prepared using electrospinning. After electrospinning, the self-supporting electrode membrane is removed, dried, and cut into 15cm × 20cm pieces. A flexible carbon mesh is used as the flexible substrate, and a pressure of 4N (e.g., ...) is applied. Figure 1 The self-supported electrode was oxidized at 280℃ for 2 hours, followed by treatment at 900℃ for 2 hours under an argon atmosphere with an argon gas flow rate of 100 sccm. The prepared self-supported electrode was then cut into 10 cm diameter electrodes. A zinc sheet was used as the counter electrode, and the cut self-supported electrode served as the working electrode. 2 mol / L zinc sulfate was used as the electrolyte, and the electrolyte was applied at 5 mA cm⁻¹. -2 A zinc anode with oriented crystal reconstruction was obtained by electroplating at the current density for 6 hours. The battery test parameters for Example 4 were the same as those for Example 1.

[0065] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a crystal-oriented reconstructed zinc anode, characterized in that, Includes the following steps: (1) The active material or its precursor, solvent, and polymer are mixed evenly to obtain an electrospinning solution, and a self-supporting electrode is prepared by electrospinning. The active material includes any one or a mixture of hexagonal boron nitride, hexagonal tungsten oxide, carbon nitride, zinc oxide, silicon carbide, and graphene. The precursor of the active material is boric acid and dicyandiamine. (2) Dry the self-supporting electrode obtained in step (1), and then use a flexible substrate to attach the self-supporting electrode to the top and bottom, and sinter it under pressure. (3) Deposit zinc on the self-supporting electrode after sintering in step (2) using the electrodeposition method to obtain a crystal-oriented reconstructed zinc anode.

2. The preparation method according to claim 1, characterized in that, The concentration of the active substance in the electrospinning solution in step (1) is 1-10 wt%.

3. The preparation method according to claim 2, characterized in that, The active material has a hexagonal crystal system, with the secondary axis of the cell having a size of 2.2-3.2 Å.

4. The preparation method according to claim 1, characterized in that, Step (1); the molar ratio of boric acid and dicyandiamine is 1:1-8:1; the total concentration of boric acid and dicyandiamine in the electrospinning solution is 1-10 wt.

5. The preparation method according to claim 1, characterized in that, The solvent in step (1) is any one or a mixture of dimethylformamide, alcohol, deionized water, and N-methylpyrrolidone; the polymer is any one or a mixture of polyvinylpyrrolidone, polyacrylonitrile, polymethyl acrylate, and polyvinyl alcohol; and the concentration of the polymer in the electrospinning solution is 8-30 wt.

6. The preparation method according to claim 1, characterized in that, The flexible substrate in step (2) is any one of flexible hydrophilic carbon cloth, flexible carbon fiber felt, or flexible carbon mesh; the applied pressure ranges from 0.5 to 10 N; the sintering is performed at 200-500 ℃ for 0.5-8 h under oxidative conditions, or at 700-1200 ℃ for 0.5-10 h under carbonization conditions; the oxidative conditions are performed in an air atmosphere; the carbonization conditions use a nitrogen or argon atmosphere with a gas flow rate of 40-150 sccm.

7. The preparation method according to claim 1, characterized in that, The electrodeposition method described in step (3) is specifically: a two-electrode electrodeposition method with a self-supporting electrode as the working electrode and a zinc sheet as the counter electrode; or a three-electrode electrodeposition method with a self-supporting electrode as the working electrode, a platinum sheet or platinum mesh as the counter electrode, and Ag / AgCl as the reference electrode. The electrolyte used in the electrodeposition method in step (3) is a zinc salt solution; the zinc salt is any one of zinc sulfate, zinc chlorate, zinc acetate, and zinc trifluoromethanesulfonate, and the concentration of the zinc salt solution is 0.3-3 mol / L.

8. The preparation method according to claim 1, characterized in that, Step (3) describes an electrodeposition method that employs either a constant current method or a constant voltage method; the current density range of the constant current method is -0.5 to -100 mA cm⁻¹. -2 Capacity is 5-100 mAh cm -2 The constant voltage method has a voltage range of -0.01 to -2 V and a capacity of 5-100 mAh cm⁻¹. -2 .

9. A crystal-oriented reconstructed zinc anode prepared by the preparation method according to any one of claims 1-8.

10. The application of the crystal-oriented reconstructed zinc anode according to claim 9 in zinc-air batteries, zinc-ion batteries, zinc-ion supercapacitors, and zinc flow batteries.

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