Zinc ion battery electrolyte film and preparation method and application thereof

Abstract

The application discloses a zinc ion battery electrolyte film and a preparation method and zinc ion battery thereof, and the electrolyte film is prepared by cross-linking reaction of chitosan, ester cross-linking agent and zinc ion transmission promoter in a solvent; according to mass percentage, raw material components of the electrolyte film include: 15-25wt% of chitosan, 3-8wt% of ester cross-linking agent, 1-5wt% of zinc ion transmission promoter, and the rest is solvent; the zinc ion transmission promoter is a compound containing a pi electron structure. The electrolyte film of the application forms uniform ion conduction channels and stable cross-linking structures on the surface and inside of chitosan, can effectively improve the zinc ion migration rate, inhibit the growth of zinc dendrites, and at the same time, enhance the mechanical stability of the film, and significantly optimize the electrochemical performance of the zinc ion battery. The electrolyte film has excellent ion conductivity, mechanical stability and structural durability, and the assembled zinc ion battery exhibits long cycle life, high coulomb efficiency and stable discharge specific capacity.

Description

Technical Field

[0001] This invention relates to the field of electrolyte technology, and more specifically, to a zinc-ion battery electrolyte membrane, its preparation method, and a zinc-ion battery. Background Technology

[0002] Zinc-ion batteries have become a popular research area in large-scale energy storage due to their abundant raw material reserves, low cost, environmental friendliness, and high theoretical capacity. However, the liquid electrolyte used in traditional zinc-ion batteries suffers from problems such as easy leakage and poor safety. Furthermore, the growth of zinc dendrites can puncture the separator, causing short circuits and severely affecting the battery's cycle life and safety. At the same time, existing electrolyte membrane substrate materials often suffer from insufficient mechanical stability and poor compatibility with zinc ions, limiting their application.

[0003] As one of the core components of zinc-ion batteries, the electrolyte membrane not only needs to have good zinc-ion conductivity, but also needs to isolate the positive and negative electrodes and ensure structural stability. Chitosan, as a natural polymer material, has good biocompatibility, easy film formation, and hydrophilicity, making it a potential substrate material for electrolyte membranes. However, pure chitosan membranes have defects such as insufficient mechanical strength and low cross-linking degree, and are extremely prone to swelling or even dissolving in aqueous electrolytes.

[0004] In existing technologies, crosslinking agents are often used to modify chitosan membranes to improve their stability. Common crosslinking agents, such as aldehydes like glutaraldehyde and glyoxal, have high crosslinking efficiency, but they also possess high biotoxicity. Furthermore, the crosslinked membrane material often becomes brittle and its flexibility significantly decreases, making it difficult to meet the requirements of battery winding and assembly. While natural iridoid crosslinking agents have lower toxicity, they are expensive and have a slow crosslinking reaction rate, which is not conducive to large-scale production. In addition, regarding improving ionic conductivity, existing technologies often introduce inorganic fillers or conductive polymers, but simple physical blending often leads to uneven dispersion, easily forming defects within the membrane, which in turn hinders uniform ion transport.

[0005] Therefore, developing an electrolyte membrane with chitosan as the matrix, using low-toxicity and high-efficiency ester crosslinking agents to construct a stable structure, and combining it with uniformly distributed transport promoters to form a high-efficiency ion conduction channel is of great significance for promoting the practical application of zinc-ion batteries. Summary of the Invention

[0006] The purpose of this invention is to provide a zinc-ion battery electrolyte membrane, its preparation method, and a zinc-ion battery. The electrolyte membrane uses chitosan as a matrix, constructs a stable cross-linked structure through an ester cross-linking agent, and forms a highly efficient ion conduction channel by combining it with a zinc ion transport promoter. This effectively improves the zinc ion migration efficiency, enhances the mechanical stability of the membrane, and significantly improves the electrochemical performance of the zinc-ion battery.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A zinc-ion battery electrolyte membrane is prepared by a cross-linking reaction of chitosan, an ester cross-linking agent, and a zinc ion transport promoter in a solvent. By mass percentage, its raw material components include: 15-25 wt% chitosan, 3-8 wt% ester cross-linking agent, 1-5 wt% zinc ion transport promoter, and the balance being solvent. The zinc ion transport promoter is a compound containing a π-electron structure.

[0009] The zinc ion transport promoter is a compound containing a π-electron structure.

[0010] In this invention, chitosan serves as the matrix, providing the basic framework for the electrolyte membrane. Its excellent hydrophilicity facilitates electrolyte wetting and zinc ion diffusion. Ester crosslinking agents react with chitosan molecular chains to form a stable three-dimensional network structure, significantly improving the mechanical strength and structural durability of the electrolyte membrane and preventing membrane damage during battery cycling. Zinc ion transport promoters can construct continuous ion conduction channels, further enhancing the zinc ion migration rate. The three components work synergistically to comprehensively optimize the overall performance of the electrolyte membrane.

[0011] Furthermore, the ester crosslinking agent is any one of methyl methacrylate, hydroxyethyl methacrylate, isobornyl methacrylate, glycidyl methacrylate, and butyl methacrylate.

[0012] Furthermore, the zinc ion transport promoter is any one of polythiophene, polyaniline, and covalent triazine.

[0013] Furthermore, the crosslinking reaction conditions include heat treatment or ultraviolet irradiation treatment, wherein the heat treatment temperature is 40-80℃. This temperature range can promote the full bonding and crosslinking reaction between each component and the matrix material, avoiding component decomposition due to excessively high temperatures or affecting the crosslinking effect due to excessively low temperatures.

[0014] Furthermore, the chitosan has a molecular weight of 50,000-200,000 Da and a degree of deacetylation ≥85%. Chitosan within this parameter range exhibits both good film-forming properties and solubility, and can fully react with ester crosslinking agents to form a stable structure.

[0015] Further, the solvent is preferably a 1-5 wt% aqueous solution of acetic acid, formic acid, or lactic acid. Acidic aqueous solutions have good solubility for chitosan and can promote the cross-linking reaction (such as transesterification or ring-opening reaction) between ester cross-linking agents and chitosan, which is beneficial for forming a homogeneous composite modified system. Mixed solvents of N,N-dimethylformamide, acetone, tetrahydrofuran, ethyl acetate, etc., with water can also be used.

[0016] A method for preparing the zinc-ion battery electrolyte membrane includes the following steps:

[0017] Weigh out chitosan, ester crosslinking agent, and zinc ion transport promoter, add them to the solvent, and stir until completely dissolved to form a homogeneous solution. Pour the solution into a mold, let it stand for 10-30 minutes, and then heat it in an environment of 40-80℃ for 1-3 hours for crosslinking treatment. Remove the treated material from the mold, clean it to remove uncrosslinked components from the surface, and obtain the zinc ion battery electrolyte membrane.

[0018] Furthermore, the temperature for the heating crosslinking treatment was 80°C, and the treatment time was 12 hours.

[0019] A zinc-ion battery includes the aforementioned electrolyte membrane, zinc-based negative electrode, positive electrode, and electrolyte, wherein the electrolyte is one of a 1-3 mol / L zinc sulfate solution, a zinc sulfate-lithium sulfate mixed solution, a zinc sulfate-zinc chloride mixed solution, or a zinc sulfate-manganese sulfate mixed solution.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] This invention uses chitosan as the matrix material, combined with ester crosslinking agents and zinc ion transport promoters to construct a composite system, forming a highly efficient ion conduction channel with a zinc ion conductivity of up to 10. -3 The S / cm ratio is above 100%, significantly higher than that of traditional glass fiber membranes or pure chitosan membranes. The cross-linking reaction between ester cross-linking agents and chitosan significantly improves the mechanical stability and structural durability of the electrolyte membrane. At the same time, the composite system can effectively inhibit zinc dendrite growth, improving the coulombic efficiency and cycle stability of the battery. The preparation process is simple, the conditions are mild, it is easy to scale up production, and the raw materials used are inexpensive and environmentally friendly, showing broad application prospects. Attached Figure Description

[0022] Figure 1 This is a scanning electron microscope image of the electrolyte membrane prepared in Example 1 of the present invention.

[0023] Figure 2 These are AC impedance test diagrams of zinc symmetric batteries assembled with electrolyte membranes prepared in Examples 1, 2, 3, 4 and Comparative Examples 1, 2, 3 of the present invention.

[0024] Figure 3 This is a discharge specific capacity diagram of the full cells assembled with the electrolyte membranes prepared in Example 1 and Comparative Example 1 of the present invention.

[0025] Figure 4 These are rate performance test graphs of zinc symmetric batteries assembled with electrolyte membranes prepared in Example 1 and Comparative Example 1 of this invention. Detailed Implementation

[0026] Numerous specific details are set forth in the following description to provide a full understanding of the invention. However, the invention can be practiced in many other ways than those described herein, and similar modifications can be made by those skilled in the art without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0028] It should be noted that, unless otherwise specified, the raw materials, instruments, etc. involved in this invention are all commercially available products.

[0029] Example 1

[0030] A composite modified zinc-ion battery electrolyte membrane is prepared by the following steps: 7.5g of chitosan (molecular weight 100,000 Da, degree of deacetylation 90%), 1.5g of glycidyl methacrylate, and 0.8g of covalent triazine are weighed and added to 100mL of 2wt% acetic acid aqueous solution. The solution is stirred at 60℃ for 3 hours until completely dissolved, forming a homogeneous composite modified system. The composite modified system solution is cast into a 10*10*0.5cm volume polytetrafluoroethylene mold, allowed to stand for 30 minutes, and then placed in a 60℃ oven for crosslinking treatment for 2 hours. The treated electrolyte membrane is removed, rinsed three times with deionized water to remove uncrosslinked components from the surface, and then dried in a 60℃ vacuum drying oven for 12 hours to obtain the zinc-ion battery electrolyte membrane. Figure 1 The SEM images show that a uniform and dense modified layer is formed on the surface of the electrolyte membrane, and continuous porous channels are constructed inside.

[0031] Example 2

[0032] Compared with Example 1, the difference is that the heating crosslinking treatment temperature is 40°C and the treatment time is 3 hours, so as to prepare a chitosan-based composite electrolyte membrane with low temperature and long treatment time.

[0033] Example 3

[0034] Compared with Example 1, the difference is that the zinc ion transport promoter is 1.6g of covalent triazine, and chitosan-based composite electrolyte membranes with different component ratios of zinc ion transport promoters are prepared.

[0035] Example 4

[0036] Compared with Example 1, ultraviolet irradiation treatment was used instead of heating treatment, and the irradiation time was 30 min to prepare an ultraviolet irradiated crosslinked chitosan-based composite electrolyte membrane.

[0037] Comparative Example 1

[0038] Compared with Example 1, the difference is that no composite modification treatment is performed on the chitosan matrix material. Preparation method: 7.5g of chitosan was weighed and dissolved in 100mL of 2wt% acetic acid aqueous solution without adding any crosslinking agent or accelerator. After stirring and dissolving, the mixture was directly cast into a film and dried to obtain a pure chitosan film.

[0039] Comparative Example 2

[0040] Compared to Example 1, the difference is that no zinc ion transport promoter is added. Preparation method: Weigh 7.5g chitosan and 1.5g glycidyl methacrylate, dissolve them in 100mL of 2wt% acetic acid aqueous solution, without adding covalent triazine. Subsequent crosslinking and processing steps are the same as in Example 1.

[0041] Comparative Example 3

[0042] Compared to Example 1, the difference lies in the addition of glutaraldehyde as the crosslinking agent, and the absence of a zinc ion transport promoter. Preparation method: Weigh 7.5g chitosan and 1.5g glutaraldehyde, dissolve them in 100mL of 2wt% acetic acid aqueous solution, without adding covalent triazine. Subsequent crosslinking and processing steps are the same as in Example 1.

[0043] Performance testing

[0044] The assembly of zinc-ion batteries follows this sequence: positive electrode shell, positive electrode material (NH4V5O) 10 The components include an electrolyte membrane, an electrolyte solution (2 mol / L ZnSO4 solution), a zinc negative electrode, and a negative electrode shell. For a zinc symmetric battery, both electrodes on both sides of the membrane are zinc foil; the electrolyte volume is 180 μL.

[0045] Figure 2Impedance spectra of zinc symmetric batteries assembled with electrolyte membranes prepared in Examples 1, 2, 3, and 4, and Comparative Examples 1, 2, and 3, from 100,000 Hz to 0.1 Hz, are shown. The comparison reveals that the semicircle diameters (representing charge transfer impedance) of Examples 1, 2, 3, and 4 are significantly smaller than those of Comparative Examples 1, 2, and 3, indicating that Examples 1, 2, 3, and 4 exhibit lower charge transfer resistance and superior interfacial electrochemical performance. The semicircle diameters of Examples 2, 3, and 4 are very close to those of Example 1, indicating that the charge transfer impedance of these three examples is at the same level as that of Example 1. Comparative Example 3 uses glutaraldehyde as a crosslinking agent, which is an aliphatic dialdehyde (-CHO) crosslinking agent. It constructs a relatively rigid crosslinking network by forming a Schiff base through the aldehyde group and the primary amino group of chitosan. The crosslinking agent used in Example 1 has different active groups, resulting in a more flexible crosslinking network that can introduce polar sites favorable for ion transport. As can be seen from the figure, the semicircle diameter of Comparative Example 3 is significantly larger than that of Example 1, indicating that its charge transfer impedance (Rct) is much higher than that of Example 1, directly reflecting the difference in the resistance to zinc ion transfer at the interface. The increased charge transfer impedance also implies greater interfacial stress leading to breakage gaps, further indicating its low mechanical properties.

[0046] Figure 3 The graph shows the discharge specific capacity of the full cells assembled with the electrolyte membranes prepared in Example 1 and Comparative Example 1 at a current density of 5 amperes per gram. Analysis shows that the discharge specific capacity of both samples decreases with increasing cycle number, but the discharge specific capacity of Example 1 is consistently much higher than that of Comparative Example 1 (maintaining a higher value both initially and after cycling), and the decrease trends of the two are similar. This indicates that Example 1 has superior energy storage capacity.

[0047] Figure 4The rate performance of full cells assembled with the electrolyte membranes prepared in Example 1 and Comparative Example 1 at current densities of 0.1, 0.5, 1, 2, 3, and 5 mA / cm² is shown. The curves exhibit a "sawtooth cycle" corresponding to multiple charge-discharge processes. As time progresses, the current density gradually increases, and the voltage fluctuation amplitude gradually changes. At low current densities, the voltage curves of both examples are similar in shape. At high current densities, the voltage fluctuation of Example 1 is more stable and the curve is more regular, while the voltage fluctuation of Comparative Example 1 is relatively more dispersed. This indicates that the voltage stability of Example 1 at different current densities, especially at high current densities, is superior to that of Comparative Example 1, demonstrating better rate adaptability of electrochemical performance. The absence of any voltage drops, spikes, or short circuits indicates that no coarse dendrites capable of piercing the electrolyte appeared on the zinc anode surface. This further proves that the chitosan-based composite electrolyte membrane of the present invention has excellent ion conductivity and the ability to suppress dendrite growth, significantly improving the rate performance of the battery. The regular time-voltage curves of the symmetrical cell at different current density rates, without sudden voltage shifts, indicate that the electrode and electrolyte maintain a tight and continuous interfacial contact without interfacial contact failure due to electrolyte membrane damage. This indirectly proves that the electrolyte membrane of this system has excellent mechanical properties, can effectively resist interfacial stress, maintain membrane structural integrity, and ensure the stability of the electrochemical interface.

[0048] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A zinc-ion battery electrolyte membrane, characterized in that, The electrolyte membrane is prepared by a cross-linking reaction of chitosan, ester cross-linking agent, and zinc ion transport promoter in a solvent. By mass percentage, its raw material components include: 15-25 wt% chitosan, 3-8 wt% ester cross-linking agent, 1-5 wt% zinc ion transport promoter, with the balance being solvent. The zinc ion transport promoter is a compound containing a π-electron structure. The ester cross-linking agent is any one of methyl methacrylate, hydroxyethyl methacrylate, isobornyl methacrylate, glycidyl methacrylate, and butyl methacrylate. The zinc ion transport promoter is any one of polythiophene, polyaniline, and covalent triazine.

2. The electrolyte membrane according to claim 1, characterized in that, The reaction conditions for the crosslinking reaction include heat treatment or ultraviolet irradiation treatment, wherein the heat treatment temperature is 40-80℃.

3. The electrolyte membrane according to claim 1, characterized in that, The chitosan has a molecular weight of 50,000-200,000 Da and a degree of deacetylation ≥85%.

4. The electrolyte membrane according to claim 1, characterized in that, The solvent is any one of 1-5 wt% aqueous solutions of acetic acid, formic acid, lactic acid, N,N-dimethylformamide, acetone, tetrahydrofuran, ethyl acetate, and water.

5. The method for preparing the zinc-ion battery electrolyte membrane according to any one of claims 1-4, characterized in that, The process includes the following steps: Weigh chitosan, ester crosslinking agent, and zinc ion transport promoter, add them to a solvent, and stir until completely dissolved to form a homogeneous solution; Pour the solution into a mold, let it stand for 10-30 minutes, and then heat it in an environment of 40-80℃ for crosslinking treatment for 1-3 hours; Remove the treated material from the mold, clean it to remove uncrosslinked components from the surface, and obtain the zinc ion battery electrolyte membrane.

6. The preparation method according to claim 5, characterized in that, The temperature for the heating crosslinking treatment was 80℃, and the treatment time was 12h.

7. A zinc-ion battery, characterized in that, The electrolyte includes the electrolyte membrane, zinc-based negative electrode, positive electrode, and electrolyte as described in any one of claims 1-4, wherein the electrolyte is one of a 1-3 mol / L zinc sulfate solution, a zinc sulfate-lithium sulfate mixed solution, a zinc sulfate-zinc chloride solution, or a zinc sulfate-manganese sulfate mixed solution.

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