Electrolyte of aqueous zinc ion battery and preparation method and application thereof

Abstract

The application provides a kind of electrolyte of aqueous zinc ion battery and its preparation method and application, including medium viscosity (200~400 mPa.s) chitosan and L-ascorbic acid, wherein the mass ratio of the chitosan added to the volume of the solvent in the electrolyte is 0.4 g / L~3.2g / L.The electrolyte of the application forms a macromolecular complex through ion adsorption by introducing chitosan and L-ascorbic acid, and establishes a dynamic and dense protective interface on the surface of zinc negative electrode by using its specific adsorption group (such as enediol structure), thereby achieving synergistic effect from two aspects of solvation structure regulation and interface chemical modification, and ultimately improving the cycle life and electrochemical performance of aqueous zinc ion battery.

Description

Technical Field

[0001] This invention relates to the field of aqueous zinc-ion battery electrolytes, specifically to aqueous zinc-ion battery electrolytes, their preparation methods, and applications. Background Technology

[0002] With the increasing demand for battery safety, cost and environmental friendliness from the new energy vehicle and large-scale energy storage markets, aqueous zinc-ion batteries have become an electrochemical energy storage system with great development potential due to their inherent safety, abundant resources and simple manufacturing process.

[0003] However, the commercialization of AZIBs is limited by its core component—the electrolyte—and the resulting zinc anode interface problems. For example, uneven distribution of zinc ions during deposition can lead to the formation of zinc dendrites, which may puncture the separator and cause a short circuit in the battery. Side reactions such as hydrogen evolution reaction (HER) can cause zinc corrosion and the generation of insoluble byproducts (such as ZnO and Zn(OH)2), which not only consume the active material in the cathode material but also increase the internal pressure of the battery, posing a safety hazard. The theoretical decomposition voltage of water is only 1.23 V. The narrow electrochemical window of aqueous zinc-ion batteries not only limits the application of high-voltage cathode materials but also restricts the improvement of the energy density of aqueous zinc-ion battery cathode materials.

[0004] In existing technologies, researchers have extensively explored the introduction of various functional additives into the electrolyte to improve the stability of zinc anodes. However, the design of most current additives still has significant limitations: their functions are often relatively singular, either focusing solely on building a physical barrier at the anode interface to isolate water molecules, or solely on regulating the zinc ion solvation structure to guide deposition. These approaches struggle to simultaneously and synergistically address the interrelated challenges of dendrite growth and exacerbated side reactions. This singular focus limits further improvements in the overall battery performance.

[0005] Therefore, developing a composite additive system that can simultaneously achieve the dual functions of interface shielding and deposition induction has become an urgent and challenging issue in this field. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide an electrolyte for an aqueous zinc-ion battery, its preparation method, and its application. This electrolyte is based on the synergistic composition of natural medium-viscosity chitosan and ascorbic acid. Through the in-situ interaction of the two in the electrolyte, it simultaneously achieves the dual functions of interface shielding and deposition induction, thereby simultaneously and efficiently solving the problems of dendrite growth and side reactions of the zinc anode.

[0007] In a first aspect, an electrolyte comprises chitosan and L-ascorbic acid, wherein the chitosan is a medium-viscosity chitosan, and the mass ratio of the added chitosan to the volume of the solvent in the electrolyte is 0.4 g / L to 3.2 g / L.

[0008] Furthermore, the mass ratio of chitosan to L-ascorbic acid is 1:(1~2).

[0009] Furthermore, the electrolyte also includes a zinc salt and a solvent; The zinc salt includes one or more of zinc sulfate heptahydrate, zinc chloride, and zinc trifluoromethanesulfonate; the solvent is deionized water, pure water, ultrapure water, or mineral water.

[0010] Secondly, the present invention provides a method for preparing the electrolyte, comprising the following steps: (1) The chitosan, L-ascorbic acid and a portion of the solvent are mixed and protonated to obtain a mixed solution; (2) The mixed solution, zinc salt and remaining solvent are mixed to obtain the electrolyte.

[0011] Thirdly, the present invention provides an electrolyte in which additives having the following chemical structure are added:

[0012] Where n represents the degree of aggregation.

[0013] Fourthly, the present invention provides an aqueous zinc-ion battery, the aqueous zinc-ion battery comprising a positive electrode, the above-described electrolyte or an electrolyte prepared by the above-described preparation method.

[0014] Furthermore, in a Zn / / Zn symmetric cell, under conditions of a current density of 1 mA and a capacity of 0.5 mAh, the total time for which the Zn / / Zn symmetric cell can cycle stably without short circuit is not less than 800 h, preferably not less than 1500 h; after the electrolyte is deposited at a current of 10 mA for 30 min, the surface of the Zn / / Zn symmetric zinc anode is very uniform, zinc ions are deposited in a directional and tilted manner, dendrite growth is suppressed, and the surface roughness of the zinc anode is controlled within 3.0 μm. Using zinc foil as the anode and NH4V4O4... 10 In a full battery composed of positive electrodes, after 1000 charge-discharge cycles, its capacity retention rate is controlled at more than 40%, preferably more than 50%.

[0015] This invention provides an electrolyte for an aqueous zinc-ion battery, its preparation method, and its application, which has at least the following beneficial effects: This invention introduces chitosan and L-ascorbic acid to form a macromolecular complex that is structurally stable and functionally synergistic through ion adsorption, and utilizes its specific adsorption groups (such as enediol structures) to establish a dynamic and dense protective interface on the zinc anode surface, thereby achieving synergistic effects from two levels: solvation structure regulation and interface chemical modification, ultimately comprehensively improving the cycle life and electrochemical performance of the aqueous zinc-ion battery. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 The electrolytes prepared in Example 2 and Comparative Example 1 were tested in an aqueous zinc-ion battery at 1 mA cm⁻¹. -2 The current density and time-voltage curves at a capacity of 0.5 mAh; Figure 2 Scanning electron microscope images of the zinc anode surface after the electrolytes prepared in Example 2 and Comparative Examples 1 and 4 were deposited in an aqueous zinc-ion battery at a current density of 10 mA for 30 min. Figure 3 The images show a comparison of laser scanning confocal microscopy images of the zinc anode surface after the electrolytes prepared in Example 2 and Comparative Example 1 were deposited in an aqueous zinc-ion battery at a current density of 10 mA for 30 min. Among them, (a) and (b) are the 3D scanning images and corresponding surface roughness fitting images of the laser scanning microscope in Example 2, and (c) and (d) are the 3D scanning images and corresponding surface roughness fitting images of the laser scanning microscope in Comparative Example 1.

[0018] Figure 4 The image shows an in-situ optical microscope image of the electrolytes prepared in Example 2 and Comparative Examples 1 and 4 charged at 10 mA for 60 min in an aqueous zinc-ion battery. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] In a first aspect, embodiments of the present invention provide an electrolyte comprising medium-viscosity chitosan (200 ~ 400 mPa.s) and L-ascorbic acid, wherein the mass ratio of chitosan added to the volume ratio of the solvent in the electrolyte is 0.4 g / L ~ 3.2 g / L.

[0021] According to the inventors' research and analysis, this invention achieves precise control of the interfacial chemical behavior of the electrolyte by introducing chitosan and L-ascorbic acid. Chitosan and L-ascorbic acid form a macromolecular complex with stable structure and synergistic function through ion adsorption. On the one hand, the protonated amino groups of chitosan reconstruct the solvation structure of zinc ions, guiding the uniform nucleation of zinc. On the other hand, the preferential adsorption of the olefinic groups of L-ascorbic acid on the zinc anode surface forms a dense dynamic protective film, effectively blocking the contact between water molecules and zinc. Thus, the two core problems of dendrite growth and aggravated side reactions are solved simultaneously, significantly better than the case of adding a single substance.

[0022] In the structure of medium viscosity chitosan (200 ~ 400 mPa.s), the main repeating unit is 2-amino-2-deoxy-β-D-glucanopyranose (β-D-glucosamine), while a small amount of N-acetyl-β-D-glucanopyranose (derived from the partial deacetylation of the raw material chitin) remains. Each glucosamine unit contains one amino group (-NH2) and one hydroxyl group (-OH), and the N-acetylglucosamine unit contains one hydroxyl group and one acetylamino group (-NHCOCH3). These functional groups are the core sites for its interaction with L-ascorbic acid and zinc ions.

[0023] The mass ratio of chitosan added to the volume of solvent in the electrolyte is 0.4 g / L to 3.2 g / L, for example, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 0.0, 3.1, 3.2 g / L, etc., preferably 0.8 to 2.0 g / L.

[0024] The appropriate amount of chitosan added can achieve optimal interface (electrode-electrolyte interface, i.e., solid-liquid interface) regulation while maintaining excellent ion conductivity, thereby improving the cycle life of aqueous zinc-ion batteries.

[0025] In some specific embodiments, the mass ratio of medium-viscosity chitosan to L-ascorbic acid can be 1:(1~2), for example, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, or any range of adjacent values, preferably 1:1 to 1:1.3. More preferably, it is 1:1.1, which ensures complete dissolution of chitosan. Adding too much L-ascorbic acid can affect battery performance and easily lead to side reactions.

[0026] The mass ratio of chitosan to L-ascorbic acid within the above range is beneficial for inhibiting the growth of zinc dendrites, reducing the generation of side reactions such as hydrogen evolution, optimizing ionic conductivity, and improving the electrochemical performance of aqueous zinc-ion batteries.

[0027] The total mass concentration of chitosan and L-ascorbic acid meets the above range. Chitosan complexes zinc ions through hydroxyl and amino groups, resulting in a uniform negative electric field distribution. L-ascorbic acid increases zinc nucleation sites through ethylene glycol adsorption. Together, they induce smooth deposition of zinc ions, significantly reducing the short-circuit risk of dendrites piercing the diaphragm and synergistically constructing a stable interface.

[0028] In some specific embodiments, the electrolyte may also include zinc salt and solvent.

[0029] Specifically, the zinc salt may include one or more of zinc sulfate heptahydrate, zinc chloride, zinc trifluoromethanesulfonate, etc., with zinc sulfate heptahydrate being preferred.

[0030] Zinc salts are Zn in electrolytes 2+ The main source is the core carrier for energy storage and release in aqueous zinc-ion batteries. Zinc salts meet the above requirements and can participate in the formation of the interface SEI (solid electrolyte interphase) membrane. They can work synergistically with chitosan and L-ascorbic acid to control the solvation structure of zinc ions, reduce free water activity, and inhibit hydrogen evolution and zinc corrosion.

[0031] Solvents may include water (deionized water, pure water, ultrapure water, or mineral water, etc.).

[0032] Solvents that meet the above criteria can better dissolve zinc salts, chitosan, and L-ascorbic acid, thereby forming a homogeneous and stable solution system.

[0033] In a second aspect, the present invention provides a method for preparing the above-mentioned electrolyte, comprising the following steps: (1) mixing medium viscosity chitosan (200 ~ 400 mPa.s), L-ascorbic acid and a portion of solvent, and performing a protonation reaction to obtain a mixed solution; (2) mixing the mixed solution, zinc salt and the remaining solvent to obtain an electrolyte.

[0034] For example, step (1) may specifically include: mixing chitosan and L-ascorbic acid in water and carrying out a protonation reaction to obtain a mixed solution.

[0035] Specifically, L-antiseptic acid can be dissolved in water to obtain an acidic solution, and then chitosan can be added.

[0036] Chitosan has a viscosity of 200 mPa•s to 400 mPa•s (medium viscosity).

[0037] Protonation reactions can include the amino protonation of chitosan (non-covalent interaction), and the enediol structure of L-ascorbic acid can ionize H in an aqueous environment. + This causes the molecules to carry a partial negative charge; the amino groups of chitosan can be protonated under acidic conditions (-NH4+). 3+ The positively charged L-ascorbic acid olefin structure and the amino group of chitosan form an electrostatic bond through positive and negative charge attraction, further enhancing the synergistic effect between molecules.

[0038] Furthermore, the protonation reaction is based on the biomolecular material (chitosan), forming a mixed solution through a Brewster acid-base neutralization reaction.

[0039] The protonation reaction process can be illustrated as shown in Equation 1: Formula 1.

[0040] n represents the degree of polymerization, which is related to the degree of polymerization of chitosan, i.e., the number of repeating units in the chitosan molecular chain.

[0041] The temperature for the protonation reaction can be 20℃ to 25℃, for example, 20, 21, 22, 23, 24, 25℃ or any two of these values.

[0042] The protonation reaction time can be 10 min to 15 min, for example, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, or any two of these values.

[0043] The mixed solution (chitosan-L-ascorbic acid mixed solution) can be a homogeneous and transparent solution, and undissolved chitosan may also be dispersed in the mixed solution.

[0044] For example, step (2) may specifically include: mixing zinc salt with solvent to obtain zinc salt solution, and then mixing the mixed solution with zinc salt solution to obtain electrolyte.

[0045] The concentration of the zinc salt solution can be from 1 mol / L to 3 mol / L, for example, 1, 2, or 3 mol / L, preferably 2 mol / L.

[0046] Thirdly, embodiments of the present invention provide an aqueous zinc-ion battery, comprising a positive electrode, a negative electrode, and the electrolyte described above or the electrolyte prepared by the above preparation method.

[0047] The positive electrode may include a current collector material and a positive electrode material coated on the surface of the current collector material.

[0048] Current collector materials can include metallic materials, such as zinc foil, copper foil, and titanium foil.

[0049] The positive electrode material (active material) may include at least one of manganese-based materials, vanadium-based materials, Prussian blue analogues, polyaniline, elemental iodine, and basic zinc sulfate, preferably vanadium-based materials, and more preferably ammonium tetravanadate (NH4V4O). 10 ).

[0050] The negative electrode may include a current collector material, and further, the current collector material may include at least one of zinc foil and copper foil.

[0051] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0052] Example 1 This embodiment provides a method for preparing an electrolyte, including: (1) First, dissolve 8.8 mg L-antioxidant in 10 ml of deionized water to obtain an acidic solution. Then add 8 mg chitosan, stir for 10 min, and carry out a protonation reaction. The protonation reaction temperature is 20 °C and the time is 15 min to obtain a mixed solution. (2) Mix 5.7512g of zinc sulfate heptahydrate (zinc salt) with 10ml of deionized water (solvent) to obtain a zinc salt solution. Then mix the mixed solution with the zinc salt solution and stir for 15min to obtain an electrolyte.

[0053] In this embodiment, the mass ratio of chitosan added to the volume of solvent in the electrolyte is 0.4 g / L, and the mass ratio of chitosan to L-ascorbic acid is 1:1.1.

[0054] Example 2 This embodiment is basically the same as Example 1, except that: the mass of chitosan added is 16 mg, the mass of L-antioxidant added is 17.6 mg, and the volume ratio of the added chitosan mass to the solvent in the electrolyte is 0.8 g / L.

[0055] Example 3 This embodiment provides a method for preparing an electrolyte, including: (1) First, dissolve 26.25 mg L-antioxidant in 10 ml of deionized water to obtain an acidic solution. Then add 24 mg chitosan and stir for 30 min to carry out a protonation reaction. The protonation reaction temperature is 25 °C and the time is 10 min to obtain a mixed solution. (2) Mix 5.7512g of zinc sulfate heptahydrate (zinc salt) with 10ml of deionized water (solvent) to obtain a zinc salt solution. Then mix the mixed solution with the zinc salt solution and stir for 15min to obtain an electrolyte. The ratio of the mass of chitosan added to the volume of the solvent in the electrolyte is 1.2g / L.

[0056] Example 4 This embodiment provides a method for preparing an electrolyte, including: (1) First, dissolve 35 mg L-antioxidant in 10 ml of deionized water to obtain an acidic solution. Then add 32 mg chitosan, stir for 20 min, and carry out a protonation reaction. The protonation reaction temperature is 23 °C and the time is 12 min to obtain a mixed solution. (2) Mix 5.7512g of zinc sulfate heptahydrate (zinc salt) with 10ml of deionized water (solvent) to obtain a zinc salt solution. Then mix the mixed solution with the zinc salt solution and stir for 15min to obtain the electrolyte. The mass ratio of chitosan added to the volume of solvent in the electrolyte is 1.6g / L.

[0057] Example 5 This embodiment is basically the same as Embodiment 1, except that: the mass of L-ascorbic acid added is 70 mg, the mass of chitosan is 64 mg, and the volume ratio of the added chitosan to the solvent in the electrolyte is 3.2 g / L.

[0058] Comparative Example 1 Mix 5.7512g of zinc sulfate heptahydrate (zinc salt) with 20ml of deionized water (solvent) to obtain a zinc salt solution, which is the electrolyte.

[0059] Comparative Example 2 The method is basically the same as in Example 2, except that chitosan is not added, and 17.6 mg of L-antioxidant is dissolved in 10 ml of deionized water to obtain an acidic solution. Mix 5.7512g of zinc sulfate heptahydrate (zinc salt) with 10ml of deionized water (solvent) to obtain a zinc salt solution. Then mix the mixed solution with the zinc salt solution and stir for 15min to obtain an electrolyte.

[0060] Comparative Example 3 The process is basically the same as in Example 2, except that L-ascorbic acid is not added. Instead, 16 mg of chitosan is dispersed in 10 ml of deionized water and stirred for 10 min to obtain a dispersion. 5.7512g of zinc sulfate heptahydrate (zinc salt) was mixed with 10ml of deionized water (solvent) to obtain a zinc salt solution. Then the dispersion was mixed with the zinc salt solution and stirred for 15min to obtain the electrolyte.

[0061] Comparative Example 4 The method is basically the same as Comparative Example 1, except that water-soluble chitosan—chitosan nitrate—is added to Comparative Example 1. 16 mg of water-soluble chitosan is dissolved in 10 ml of deionized water and stirred for 10 min to obtain a mixed solution. Mix 5.7512g of zinc sulfate heptahydrate (zinc salt) with 10ml of deionized water (solvent) to obtain a zinc salt solution. Then mix the mixed solution with the zinc salt solution and stir for 15min to obtain an electrolyte.

[0062] Test case Negative electrode preparation: Use zinc foil (current collector material) with a thickness of 20μm, clean it with anhydrous ethanol, dry it, and cut it into round pieces with a diameter of 14mm using a slicer.

[0063] Positive electrode preparation: Use a 10μm thick copper sheet (current collector material) and cut it into zinc-copper battery positive electrode pieces using a slicing machine. NH4V4O 10 Cathode material preparation: First, 1.170g of ammonium metavanadate (NH4VO3, purity 99.0%, Sigma-Aldrich) was dissolved in 35ml of deionized water and stirred at 70℃ until a yellow solution was formed. Then, 1.35g of oxalic acid (H2C2O4, purity 99.0%, Sigma-Aldrich) was added and continuously added under magnetic stirring until the solution turned dark green. The mixture was transferred to a pressure vessel with a polytetrafluoroethylene liner and kept at 180℃ for 48h. After cooling, the precipitate was washed with deionized water and dried at 60℃.

[0064] NH4V4O 10 Acetylene black (Super P) and polyvinylidene fluoride (PVDF, binder) are mixed in a mass ratio of 7:2:1, using N-methylpyrrolidone (NMP) as the solvent, and NH4V4O 10 The mass is 28mg. After grinding, it is coated on titanium foil, dried at 60℃ for 12h, and then cut into 14mm round pieces to be used as the positive electrode of the full cell.

[0065] Electrochemical performance evaluations were conducted using CR2025 coin cells with a separator made of 675 μm thick glass fiber (GF / D) and 80 μL of electrolyte injected into each coin cell.

[0066] Electrochemical performance testing: Constant current charge-discharge tests were performed on a NEWARE (CT-4008) testing instrument.

[0067] Calculation of capacity retention rate: Discharge specific capacity of the first test cycle / Discharge specific capacity of the first thousand cycles.

[0068] Scanning electron microscopy test: Scanning tests were performed on a field emission electron microscope instrument, model QUANTA 250 FEG, USA.

[0069] Laser scanning microscope test: The scanning test was performed on a three-dimensional laser microscopy imaging system, model VK-150K (Keyence, Japan).

[0070] In-situ optical microscopy test: Scanning test was performed on the Mingmei optical microscope instrument, model MshotMF31.

[0071] The test results of the electrolytes prepared in Examples 1-5 and Comparative Examples 1-3 for use in aqueous zinc-ion batteries are shown in Table 1.

[0072] Table 1. Test results of the examples and comparative examples.

[0073] Zn / / Zn 1 mA cm -2 0.5 mAh (h): Zinc foil was used as the positive and negative electrodes of an aqueous zinc-ion battery, respectively, at a current density of 1 mA cm⁻¹. -2 The deposition / stripping capacity per cycle is 0.5 mAh cm⁻¹. -2 Under the test conditions, the total time (in hours) during which the zinc symmetric battery can cycle stably without short circuit is determined.

[0074] Zn / / Zn 10 mA cm -2 1 mAh (h): Zinc foil was used as the positive and negative electrodes of an aqueous zinc-ion battery, respectively, at a current density of 10 mA cm⁻¹. -2 The deposition / stripping capacity per cycle is 1 mAh cm⁻¹ -2 Under the test conditions, the total time (in hours) during which the zinc symmetric battery can cycle stably without short circuit is determined.

[0075] Zn / / Cu 1 mA cm -2 0.5 mAh (cycle count): The total number of cycles in which zinc foil is used as the negative electrode and copper foil as the positive electrode, and zinc can maintain a high coulombic efficiency (usually close to 100%) on the copper current collector.

[0076] Zn / / NH4V4O 10 (Capacity retention): Using zinc foil as the negative electrode, NH4V4O 10The percentage of the capacity that can be released relative to the initial capacity of a full cell with a positive electrode and a current density of 1 A / g after 1000 charge-discharge cycles.

[0077] All of the above tests were conducted at room temperature.

[0078] Conclusion Analysis: Figure 1 The electrolyte prepared in Example 2, under the conditions of a current density of 1 mA and a capacity of 0.5 mAh, allows the Zn / / Zn symmetric battery (aqueous zinc-ion battery) to cycle stably without short circuit for a total time (cycle life) of over 2000 h, compared to only 380 h in Comparative Example 1.

[0079] like Figure 2 As shown, the surface morphology of the Zn / / Zn symmetrical zinc anode prepared by the electrolytes of Example 2, Comparative Example 1 and Comparative Example 4 after deposition at a current of 10 mA for 30 min was observed by scanning electron microscopy. The electrolyte of Example 2 was used. After zinc ion deposition, the surface of the anode was very uniform, and the zinc ions were deposited in a directional and tilted manner, which suppressed dendrite growth. The deposition on the surface of the anode of Comparative Example 4 was more regular, while the surface of the anode of Comparative Example 1 was very uneven, with zinc ions deposited randomly and a large amount of zinc oxide byproducts were generated, and dendrite growth was severe.

[0080] Figure 3 To measure the surface morphology of the negative electrode of the Zn / / Zn symmetric cell using the electrolytes prepared in Example 2 and Comparative Example 1 using laser scanning microscopy, the surface roughness of the negative electrode of the Zn / / Zn symmetric cell was analyzed after deposition at a current of 10 mA for 30 min. When using the electrolyte of Example 2, the surface roughness of the zinc negative electrode was 2.553 μm, while when using the electrolyte of Comparative Example 1, the surface of the zinc negative electrode was very rough and had deep pores due to zinc stripping, with a roughness of 7.775 μm.

[0081] In-situ optical microscopy observations showed that at 10 mA / cm -2 Current density, 10 mAh / cm -2 After 1 hour of deposition at capacity, dendrite growth on the zinc anode surface using the electrolyte of Comparative Example 4 was relatively alleviated, but there were still obvious dendrites. Its deposition uniformity and flatness were still significantly worse than those using the electrolyte of Example 2 (which had no dendrites and a smooth surface). At the same time, it was significantly better than the anode using the electrolyte of Comparative Example 1, which produced a large number of irregular dendrites.

[0082] According to the test results in Table 1, the various embodiments of this invention used different amounts of chitosan as an additive in the zinc-ion battery electrolyte, which significantly improved the long-term cycle stability of the battery, especially when the chitosan addition amount was 0.8 g / L.-1 At that time, the battery's cycle performance reached its maximum value, indicating that 0.8g L -1 The optimal addition amount for binary additives.

[0083] In summary, this invention achieves precise control of the interfacial chemical behavior of the electrolyte by introducing chitosan and L-ascorbic acid, which greatly solves the problems of side reactions and zinc dendrite growth, thereby further improving the electrochemical performance of aqueous zinc-ion batteries.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrolyte, characterized in that, It includes chitosan and L-ascorbic acid, wherein the chitosan is a medium-viscosity chitosan, and the mass ratio of the added chitosan to the volume of the solvent in the electrolyte is 0.4 g / L to 3.2 g / L.

2. The electrolyte according to claim 1, characterized in that, The mass ratio of chitosan to L-ascorbic acid is 1:(1~2).

3. The electrolyte according to claim 1 or 2, characterized in that, The electrolyte also includes zinc salt and solvent; The zinc salt includes one or more of zinc sulfate heptahydrate, zinc chloride, and zinc trifluoromethanesulfonate; the solvent is deionized water, pure water, ultrapure water, or mineral water.

4. A method for preparing the electrolyte according to any one of claims 1-3, characterized in that, Includes the following steps: (1) The chitosan, L-ascorbic acid and a portion of the solvent are mixed and protonated to obtain a mixed solution; (2) The mixed solution, zinc salt and remaining solvent are mixed to obtain the electrolyte.

5. The method for preparing the electrolyte according to claim 4, characterized in that, The temperature of the protonation reaction is 20℃~25℃; the time of the protonation reaction is 10min~15min.

6. An electrolyte, characterized in that, The electrolyte contains additives having the following chemical structure: ， Where n represents the degree of aggregation.

7. An aqueous zinc-ion battery, characterized in that, It includes a positive electrode, a negative electrode, and an electrolyte as described in any one of claims 1-3 or 6, or an electrolyte prepared by any one of claims 4-5.

8. The aqueous zinc-ion battery according to claim 7, characterized in that, In a Zn / / Zn symmetric cell, under conditions of a current density of 1 mA and a capacity of 0.5 mAh, the total time for which the Zn / / Zn symmetric cell can cycle stably without short circuit is no less than 800 h, preferably no less than 1500 h. After the electrolyte is deposited at a current of 10 mA for 30 min, the surface of the Zn / / Zn symmetric zinc anode is very uniform, with zinc ions deposited in a directional and tilted manner, suppressing dendrite growth. The surface roughness of the zinc anode is controlled within 3.0 μm. Using zinc foil as the anode and NH4V4O4... 10 In a full battery composed of positive electrodes, after 1000 charge-discharge cycles, its capacity retention rate is controlled at more than 40%, preferably more than 50%.

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