Hydrogel electrolyte material for zinc ion battery as well as preparation method and application of hydrogel electrolyte material

Abstract

The invention provides a hydrogel electrolyte material for a zinc ion battery as well as a preparation method and application of the hydrogel electrolyte material, and relates to the technical field of zinc ion batteries. The hydrogel electrolyte material is prepared from the following components in parts by mass: 131 to 524 parts of acrylamide, 140 to 561 parts of ethylene glycol bis (tetraacetic acid), 228 to 916 parts of isocyano ethyl methacrylate, 1150 parts of zinc sulfate heptahydrate and pure water. According to the hydrogel electrolyte material prepared by the invention, molecules such as polyacrylamide, ethylene glycol ditetraacetic acid and isocyano ethyl methacrylate are mutually connected to form a space gridding structure, so that the growth of zinc dendrites is effectively inhibited, and zinc ions can be uniformly deposited, so that the cycling stability of a battery is remarkably improved, and the service life of the battery is prolonged. Meanwhile, the energy density of the battery is also improved, an electrochemical window is widened, and the overall electrochemical performance of the battery is enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of zinc-ion batteries, and particularly to a hydrogel electrolyte material for zinc-ion batteries, a preparation method thereof, and an application thereof. Background Art

[0002] With the continuous consumption of resources on the earth, people's attention to new energy resources has increased day by day. As an important energy storage device, batteries have received great attention under such a trend. In particular, aqueous zinc-ion batteries have gradually become a research hotspot due to their advantages such as low cost, high safety, high capacity, and long cycle life. Zinc metal is not only rich in resources and low in price, but also relatively safe to use, with a theoretical capacity as high as 819 mAh·g -1 . However, aqueous zinc-ion batteries face problems such as a narrow voltage window, low energy density, and are prone to zinc dendrite formation and side reactions at a small current. To reduce these problems, researchers are committed to developing a new electrolyte material to inhibit the formation of zinc dendrites and reduce the occurrence of side reactions, thereby improving the overall performance of zinc-ion batteries.

[0003] Hydrogels are formed by the cross-linking of hydrated polymer segments, and a large amount of water fills the gaps between them. Visually, they usually appear as a soft and moist material. There are abundant hydrophilic groups on the segments of this material, endowing the hydrogel with good water absorption and retention properties. Some hydrogels can even absorb about 2000 times their own weight of water. These hydrophilic groups can provide a large number of adsorption sites for electrolyte ions in the solution, making the hydrogel one of the ideal materials for electrolytes. More importantly, hydrogels have good designability and adjustability, which enables modified hydrogels to adapt to a variety of uses, such as stretchable hydrogels, self-healing hydrogels, mechanochromic hydrogels, degradable hydrogels, and so on. In the application of zinc-ion batteries, hydrogel electrolytes exhibit excellent flexibility. Even after being bent, knotted, twisted, or even immersed in water, they can still maintain stable electrochemical performance, showing broad application prospects.

[0004] Therefore, there is an urgent need to develop a new hydrogel electrolyte material suitable for zinc-ion batteries to further improve the performance of zinc-ion batteries. Summary of the Invention

[0005] In view of this, the present invention provides a hydrogel electrolyte material for zinc-ion batteries, a preparation method thereof, and an application thereof. The hydrogel system is composed of acrylamide-ethylene glycol bis(tetraacetic acid)-isocyanatoethyl methacrylate. Its construction strategy is simple, and the prepared zinc-ion battery has strong cycle stability, high Coulomb efficiency, and high energy density.

[0006] In a first aspect, the present invention provides a hydrogel electrolyte material for a zinc ion battery, which comprises the following components, measured by mass: 131 to 524 parts of acrylamide, 140 to 561 parts of ethylene glycol ditetraacetic acid, 228 to 916 parts of isocyanoethyl methacrylate, 1437 to 1438 parts of zinc sulfate heptahydrate and pure water.

[0007] On the basis of the above technical solution, preferably, the material further comprises 10 to 50 parts of an initiator.

[0008] On the basis of the above technical solution, preferably, the initiator is selected from one or more of ammonium persulfate, potassium persulfate or azobisisobutyronitrile.

[0009] In a second aspect, the present invention relates to a method for preparing the above-mentioned hydrogel electrolyte material for zinc ion batteries, comprising the following steps:

[0010] Zinc sulfate heptahydrate, acrylamide, ethylene glycol ditetraacetic acid and isocyanoethyl methacrylate were stirred and mixed in pure water, and then an initiator was added, and the mixture was stirred continuously and then allowed to stand to prepare a hydrogel electrolyte for zinc ion batteries.

[0011] On the basis of the above technical solution, preferably, the stirring and mixing time is 2 to 4 hours; and the continued stirring time is 12 to 20 minutes.

[0012] In a third aspect, the present invention provides a method for preparing a hydrogel battery separator, comprising immersing the battery separator in the above-mentioned hydrogel electrolyte material for zinc ion batteries and curing to obtain the hydrogel battery separator.

[0013] On the basis of the above technical solution, preferably, the immersion time is 18 to 24 hours; and the curing time is 5 to 8 minutes.

[0014] In a fourth aspect, the present invention relates to a hydrogel battery separator prepared by the above preparation method.

[0015] In a fifth aspect, the present invention relates to the use of a hydrogel battery separator in a zinc ion battery.

[0016] In a sixth aspect, the present invention provides a zinc ion battery, comprising the above-mentioned hydrogel battery separator.

[0017] The present invention provides a zinc ion battery hydrogel electrolyte material and a preparation method and application thereof, which have the following beneficial effects compared with the prior art:

[0018] (1) The hydrogel electrolyte material prepared by the present invention can effectively inhibit the growth of zinc dendrites through the spatial grid structure formed by the interconnection of molecules such as polyacrylamide, ethylene glycol bis(tetraacetic acid), and isocyanatoethyl methacrylate, enabling uniform deposition of zinc ions, thereby significantly improving the cycle stability of the battery. In addition, the application of the semi-solid electrolyte not only allows for a higher loading of electrode materials per unit volume, supports operation at higher current densities, and thus enhances the energy density of the battery; it also broadens the electrochemical window and enhances the overall electrochemical performance of the battery.

[0019] (2) The hydrogel electrolyte material of the present invention is not only applicable to aqueous zinc-ion batteries, but also can be applied to soft-pack batteries and commercial stable electrolytes, and has potential application value in flexible wearable electronic products. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0021] Figure 1 It is a schematic diagram of the synthesis principle of the grid hydrogel electrolyte provided by the present invention;

[0022] Figure 2 It is an optical example diagram of the grid hydrogel electrolyte of Examples 1-4 of the present invention;

[0023] Figure 3 It is a spectral analysis diagram of the grid hydrogel electrolyte of Examples 1-2 of the present invention;

[0024] Figure 4 It is an electrochemical test picture of the grid hydrogel electrolyte of Examples 1-2 of the present invention;

[0025] Figure 5 It is a battery cycle performance diagram of the Zn||Zn symmetric battery assembled with the hydrogel battery separator prepared in Examples 1-2 of the present invention at different current densities;

[0026] Figure 6 It is a battery cycle performance diagram of the Zn||VO2 full battery assembled with the hydrogel battery separator prepared in Example 1 of the present invention at different current densities;

[0027] Figure 7 It is a scanning electron microscope (SEM) diagram of the Zn||Zn symmetric battery assembled with the hydrogel battery separator prepared in Example 1 of the present invention at different current densities;

[0028] Figure 8 SEM images of the Zn||Cu battery assembled with the hydrogel battery separator prepared in Example 1 of the present invention at different current densities. Detailed implementation manners

[0029] Next, in combination with the implementation manners of the present invention, the technical solutions in the implementation manners of the present invention will be clearly and completely described. Obviously, the described implementation manners are only a part of the implementation manners of the present invention, rather than all the implementation manners. Based on the implementation manners in the present invention, all other implementation manners obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0030] As Figure 1 shown, in order to construct a new type of spatially meshed semi-solid hydrogel electrolyte, the inventors selected three additives: acrylamide (AM), ethylene glycol tetraacetic acid (EGTA), and isocyanatoethyl methacrylate (MIE). These three additives react chemically to jointly form a hydrogel system with specific structures and functions: First, acrylamide, as a common polymer monomer, can form a long-chain molecular structure through double-bond polymerization reactions. These long-chain molecules further crosslink to form the basic framework of the hydrogel. Second, ethylene glycol tetraacetic acid participates in the reaction under hydration, and its multiple hydroxyl groups interact with the long-chain molecules of acrylamide, enhancing the network stability of the hydrogel. At the same time, EGTA can also improve the biocompatibility and ion conductivity of the hydrogel. Finally, isocyanatoethyl methacrylate plays a key role in the reaction between the cyanate group and the hydroxyl group. It not only participates in the formation of the hydrogel network but also introduces specific chemical groups, endowing the hydrogel with additional functions and characteristics, strengthening the stability of the spatial meshing, and providing more ion transport channels.

[0031] Therefore, based on the above findings, the inventors proposed a hydrogel electrolyte material for zinc-ion batteries, which includes the following components in parts by mass: 131-524 parts of acrylamide, 140-561 parts of ethylene glycol bis(tetraacetic acid), 228-916 parts of isocyanatoethyl methacrylate, 1437-1438 parts of zinc sulfate heptahydrate, and pure water. The preparation of this hydrogel electrolyte material includes the following steps: stirring and mixing zinc sulfate heptahydrate, acrylamide, ethylene glycol bis(tetraacetic acid), and isocyanatoethyl methacrylate in pure water, adding an initiator, continuing to stir, and then standing to obtain the hydrogel electrolyte for zinc-ion batteries.

[0032] This hydrogel material forms a semi-solid hydrogel electrolyte with a novel spatial grid structure through three additives, namely acrylamide, ethylene glycol tetraacetic acid, and isocyanatoethyl methacrylate, under the action of an initiator, via a hydration reaction, a double-bond polymerization reaction, and an amine-alcohol reaction. This electrolyte not only exhibits semi-solid characteristics, effectively reducing the direct contact between the electrolyte and the zinc electrode, inhibiting the disordered growth of zinc electrode dendrites and the occurrence of side reactions, but also its spatial grid structure provides multi-channel ion migration paths, significantly accelerating the rapid transfer of zinc ions in the electrolyte and enhancing the ionic conductivity of zinc ions. In the electrochemical impedance spectroscopy (EIS) test at the solid-liquid interface, the electrolyte system containing various macromolecular structure additives exhibits an ionic conductivity level comparable to that of the base electrolyte. Meanwhile, the zinc-ion battery using this gel electrolyte demonstrates good cycle stability in both half-cell and full-cell tests, which benefits from the excellent performance of the base electrolyte and the special structure of the new electrolyte. In addition, due to its semi-solid characteristics, it can load more electrode materials per unit volume and operate efficiently in a higher current density cycle, thereby increasing the energy density. This new type of hydrogel electrolyte material not only maintains the ultra-high ionic conductivity of aqueous zinc-ion batteries but also significantly improves the cycle stability and energy density of the battery. It is suitable for large-scale applications in flexible wearable electronic products and shows broad application prospects due to its excellent flexibility and adaptability. In short, this electrolyte material integrating multiple advantages brings new development opportunities to the field of zinc-ion batteries.

[0033] The following further describes the present invention in conjunction with specific embodiments, and the protection scope of the present invention is not limited by the following embodiments. Unless otherwise specified, the main materials involved in the following examples are all conventional commercially available products. Exemplarily: The battery separator material is purchased from the GF / A glass fiber separator of the Whatman brand.

[0034] Example 1

[0035] Prepare a 10% mass fraction of grid hydrogel electrolyte

[0036] This example provides a hydrogel electrolyte material for zinc-ion batteries, including the following preparation steps:

[0037] S1. Dissolve 1150 mg of zinc sulfate heptahydrate in 1.8 ml of ultrapure water to prepare a 2 M ZnSO4 solution;

[0038] S2. Dissolve 52.4 mg of acrylamide, 56.1 mg of ethylene glycol bis(tetraacetic acid), and 91.54 mL of isocyanatoethyl methacrylate in the 1.8 ml of 2 M ZnSO4 solution obtained in step S1, and stir in the dark for 0.5 h to obtain a clear electrolyte solution;

[0039] S3. Add 30 mg of the thermal initiator ammonium persulfate to the clarified electrolyte solution in step S2, and continue stirring for 15 min in the dark to obtain a hydrogel electrolyte material.

[0040] Based on the hydrogel electrolyte material obtained from the above steps, a hydrogel battery separator is prepared by the following method:

[0041] Under dark conditions, soak the battery separator statically in the hydrogel electrolyte material prepared in step S3 for 24 h, then take it out and place it under a thermal light source for thermal curing for 5 min to obtain a hydrogel battery separator.

[0042] Example 2

[0043] Prepare a 20% mass fraction grid hydrogel electrolyte

[0044] This example provides a hydrogel electrolyte material for a zinc-ion battery, including the following preparation steps:

[0045] S1. Dissolve 1150 mg of zinc sulfate heptahydrate in 1.6 ml of ultrapure water to prepare a 2 M ZnSO4 solution;

[0046] S2. Dissolve 104.8 mg of acrylamide, 112.2 mg of ethylene glycol bis(tetraacetic acid), and 183.08 mL of isocyanatoethyl methacrylate in 4 ml of the 2 M ZnSO4 solution in step S1, and stir in the dark for 1 h to obtain a clarified electrolyte solution;

[0047] S3. Add 30 mg of the thermal initiator ammonium persulfate to the clarified electrolyte solution in step S2, and continue stirring for 15 min in the dark to obtain a hydrogel electrolyte material.

[0048] Based on the hydrogel electrolyte material obtained from the above steps, a hydrogel battery separator is prepared by the following method:

[0049] Under dark conditions, soak the battery separator statically in the hydrogel electrolyte material prepared in step S3 for 24 h, then take it out and place it under a thermal light source for thermal curing for 5 min to obtain a hydrogel battery separator.

[0050] Example 3

[0051] Prepare a 30% mass fraction grid hydrogel electrolyte

[0052] This example provides a hydrogel electrolyte material for a zinc-ion battery, including the following preparation steps:

[0053] S1. Dissolve 1150 mg of zinc sulfate heptahydrate in 1.4 ml of ultrapure water to prepare a 2 M ZnSO4 solution;

[0054] S2. Dissolve 157.2 mg of acrylamide, 168.3 mg of ethylene glycol bis(tetraacetic acid), and 274.62 mg of isocyanatoethyl methacrylate in 1.4 ml of 2 M ZnSO4 solution in step S1, and stir in the dark for 4 h to obtain a clear electrolyte solution;

[0055] S3. Add 30 mg of thermal initiator ammonium persulfate to the clear electrolyte solution in step S2, and continue to stir in the dark for 15 min to obtain a hydrogel electrolyte material.

[0056] Based on the hydrogel electrolyte material obtained from the above steps, a hydrogel battery separator is prepared by the following method:

[0057] Under dark conditions, soak the battery separator statically in the hydrogel electrolyte material prepared in step S3 for 24 h, then take it out and place it under a heat source for thermal curing for 5 min to obtain a hydrogel battery separator.

[0058] In the process of preparing a 30% mass fraction of grid hydrogel electrolyte, due to continuous stirring, the hydrogel electrolyte with too high a mass fraction directly solidifies at room temperature and cannot be tested in the next step.

[0059] Example 4

[0060] Prepare a 40% mass fraction of grid hydrogel electrolyte

[0061] This example provides a hydrogel electrolyte material for zinc-ion batteries, including the following preparation steps:

[0062] S1. Dissolve 1150 mg of zinc sulfate heptahydrate in 1.2 ml of ultrapure water to prepare a 2 M ZnSO4 solution;

[0063] S2. Dissolve 209.6 mg of acrylamide, 224.4 mg of ethylene glycol bis(tetraacetic acid), and 366.16 mg of isocyanatoethyl methacrylate in 1.2 ml of 2 M ZnSO4 solution in step S1, and stir in the dark for 4 h to obtain a clear electrolyte solution;

[0064] S3. Add 30 mg of thermal initiator ammonium persulfate to the clear electrolyte solution in step S2, and continue to stir in the dark for 15 min to obtain a hydrogel electrolyte material.

[0065] Based on the hydrogel electrolyte material obtained from the above steps, a hydrogel battery separator is prepared by the following method:

[0066] Under dark conditions, soak the battery separator statically in the hydrogel electrolyte material prepared in step S3 for 24 h, then take it out and place it under a heat source for thermal curing for 5 min to obtain a hydrogel battery separator.

[0067] During the preparation of the grid-shaped hydrogel electrolyte with a mass fraction of 40%, due to continuous stirring, the hydrogel electrolyte with too high a mass fraction solidified directly at room temperature and could not be tested further.

[0068] The inventors added specific additives in proportions of 10%, 20%, 30% and 40% by mass fraction to prepare a solution with a mixed mass percentage of X% (acrylamide (AM) + isocyanatoethyl methacrylate (MIE) + ethylene glycol bis(tetraacetic acid) (EGTA)) + (100 - X)% H2O, where the X values were set to 10, 20, 30 and 40 respectively, corresponding to Examples 1 to 4. In these experiments, acrylamide (AM), isocyanatoethyl methacrylate (MIE) and ethylene glycol bis(tetraacetic acid) (EGTA) always maintained a molar ratio of 5:4:1, were mixed and dissolved in ultrapure water, and an appropriate amount of zinc sulfate heptahydrate was added to ensure that the molar concentration of the electrolyte reached 1 - 2 mol / L. After sufficient stirring until the solution changed from grayish-white to clear and transparent. During the preparation process, the hydrogel electrolyte materials prepared in Examples 1 to 4 were successively as Figure 2 shown.

[0069] From Figure 2 it can be seen that: regardless of whether the molar concentration of the electrolyte solution is 1 mol / L or 2 mol / L, it was found that only when the mass fraction of the additive was 10% and 20%, the hydrogel electrolyte could form a uniform and transparent electrolyte system. Therefore, subsequent tests were carried out on the hydrogel electrolytes prepared in Examples 1 and 2.

[0070] Spectral analysis was carried out on the hydrogel electrolytes prepared in Example 1 and Example 2, as Figure 3 shown. Figure 3 a respectively shows the changes in characteristic peaks of five samples at different wavenumbers, successively including: pure water (H2O), 2M zinc sulfate solution (2M ZnSO4), the hydrogel electrolyte prepared in Example 1 with a concentration of 1 mol / L (10%-L), the hydrogel electrolyte prepared in Example 1 with a concentration of 2 mol / L (10%-S), the hydrogel electrolyte prepared in Example 2 with a concentration of 1 mol / L (20%-L) and the hydrogel electrolyte prepared in Example 2 with a concentration of 2 mol / L (20%-S).

[0071] From Figure 3 a it can be seen that: the single water molecule H2O shows a characteristic O-H bond stretching vibration peak at 3200 - 3600 cm -1 which is mainly caused by the symmetric stretching vibration of the O-H bond. When the basic electrolyte zinc sulfate (ZnSO4) is added to the system, in addition to the O-H bond stretching vibration peak of the above water molecules, a sulfate ion (SO4 -1 appears at a position of about 981 cm2- ) characteristic Raman peaks, which represent the stretching vibration of the S-O bond. This characteristic peak can be observed in all basic electrolytes containing zinc sulfate. Further, in the successfully prepared grid hydrogel electrolytes with different mass fractions (10% and 20%), in addition to the O-H bond and SO4 2- characteristic peaks mentioned above, after the curing process, a new Raman peak appears at approximately 2975 cm -1 . The reason for the appearance of this new peak is that during the curing process, the double bonds between the original monomers undergo a polymerization reaction, forming a stable polymer network structure, thus introducing new chemical bonds or changing the original chemical environment. This change not only proves the successful progress of the polymerization reaction but also provides direct evidence for evaluating the structural integrity of the hydrogel electrolyte. Therefore, through the analysis of these characteristic peaks, the composition and structural characteristics of the hydrogel electrolyte can be effectively monitored and confirmed.

[0072] Figure 3 Figures b respectively show the infrared spectral analysis of four samples at different wavenumbers, including in sequence: pure water (H2O), 2M zinc sulfate solution (2M ZnSO4), 2 mol / L hydrogel electrolyte prepared in Example 1 (10%-2M ZnSO4), 2 mol / L hydrogel electrolyte prepared in Example 2 (20%-2MZnSO4)

[0073] As can be seen from Figure 3 Figure b: As the mass fraction of the gel additive increases, the wavenumbers of the stretching vibration peak of the O-H bond and the bending vibration peak of the H-O-H related to water molecules gradually decrease. This phenomenon indicates that the strength of the O-H bond within water molecules gradually weakens with the increase in the additive concentration. Generally, this change implies that the hydrogen bond interaction between water molecules is affected and becomes weaker. This may be because the additive molecules interfere with the hydrogen bond network between water molecules, resulting in changes in their structure and interaction. Specifically, when water molecules are fixed in a certain medium or structure formed by the gel electrolyte, the vibration of the hydrogen bonds between them will be restricted, leading to a weakening of the hydrogen bond vibration intensity. In this case, the degree of freedom of water molecules is limited, making the energy of the hydrogen bond vibration lower, manifested as a shift or weakening of the characteristic wavenumber in the infrared spectrum. This immobilized state not only changes the structure of water molecules themselves but also affects the way they interact with other molecules, which is then reflected in their infrared spectral characteristics. Therefore, the inventor infers that after adding various gel electrolytes, the positions of water molecules are relatively fixed, reducing their original ability to freely form hydrogen bonds. These changes are reflected as a decrease in wavenumber in the spectral analysis, revealing the changes in the intermolecular interaction and structural characteristics of water molecules under different conditions.

[0074] The hydrogel battery separators prepared in Example 1 and Example 2 were respectively assembled into zinc-ion button batteries, including the following steps:

[0075] Use the positive and negative electrode cases of the button battery, stainless steel gaskets of a specific specification, stainless steel funnel shrapnel of a specific specification, zinc sheets, and the cured hydrogel electrolyte separator and other parts to assemble the button battery.

[0076] Among them, the model of the positive and negative electrode cases is No. 2032, the specification of the stainless steel gasket is ф16.1*0.5mm, the specification of the stainless steel shrapnel is ф15.4*1.1mm, the specification of the zinc sheet is ф10*0.1mm, and the specification of the glass fiber separator is ф18.5mm.

[0077] The following electrochemical tests were carried out on the zinc-ion button batteries prepared in Example 1 and Example 2, and the test results are as Figure 4 shown.

[0078] Figure 4 a shows the electrochemical performance results of the zinc-ion button battery tested by linear sweep voltammetry (LSV) at a scan rate of 0.01 mV / s. The results show that: at a scan rate of 0.01 mV / s, using a 10% mass fraction of the grid hydrogel electrolyte, that is, the battery assembled in Example 1 has an electrochemical platform voltage reaching 2.05 V, which has a wider electrochemical window compared to the 2M ZnSO4 basic electrolyte (1.88 V). The battery assembled with a 20% mass fraction of the grid hydrogel electrolyte, that is, Example 2, also shows an increased electrochemical window, which is 0.22 V higher than the basic electrolyte and reaches 2.1 V.

[0079] Figure 4 b shows the cycle stability and Coulomb efficiency of the zinc-ion button batteries assembled in Example 1 and Example 2. The results show that: the battery assembled with a 10% mass fraction of the grid hydrogel electrolyte, that is, Example 1, can stably cycle up to 700 times and maintain a high Coulomb efficiency of 99.5%. This high Coulomb efficiency not only ensures the capacity retention rate in subsequent full battery tests but also effectively improves the power output and battery sustainability.

[0080] Figure 4Figure c shows the test results of the electrochemical impedance spectroscopy (EIS) of the zinc-ion button batteries assembled with Example 1 and Example 2. The results show that: under the set scanning rate of 0.01 V / s and frequency range from 0.1 Hz to 100,000 Hz, the grid-like hydrogel electrolyte with a mass fraction of 10%, that is, the battery assembled with Example 1 shows lower electrochemical impedance than the battery assembled with Example 2 with a concentration of 20%. Compared with the 2M ZnSO4-based electrolyte, that is, the ordinary zinc-ion button battery, although the electrochemical impedance values do not change much, they all maintain a relatively high ionic conductivity. These findings indicate that the grid-like hydrogel electrolyte prepared by the present invention has significant potential in improving battery performance.

[0081] To verify the long-cycle performance of the gel electrolytes with two different mass fractions, the inventors further assembled the hydrogel battery separators prepared in Example 1 and Example 2 into Zn||Zn symmetric batteries and carried out constant current charge and discharge tests. The current density used was 1 mA·cm -2 / 1 mAh·cm -2 , and a grid-like electrolyte was prepared with 1M ZnSO4 as the base electrolyte. The test results are as Figure 5 shown.

[0082] Figure 5 Figure a shows the performance of the grid-like hydrogel electrolytes with mass fractions of 10% and 20% prepared with 1M ZnSO4 as the base electrolyte in the Zn||Zn symmetric battery after 100 hours and 210 hours of cycling. The results show that: for the electrolytes with mass fractions of 10% and 20%, serious polarization increase and irreversible phenomena occurred after 100 hours and 210 hours of cycling, seriously affecting the long-cycle stability of the battery. Therefore, we increased the concentration of the base electrolyte to 2M and prepared grid-like hydrogel electrolytes with different mass fractions according to the original ratio, and carried out constant current charge and discharge tests on the Zn||Zn symmetric battery under the same conditions. The results are as Figure 5 shown in Figure b.

[0083] Figure 5b shows the long - cycle stability of Zn||Zn symmetric cells assembled with grid - shaped hydrogel electrolytes with different mass fractions (10% and 20%) after increasing the concentration of the basic electrolyte to 2M in the galvanostatic charge - discharge test. The results show that in the 2M ZnSO4 basic electrolyte, the electrolytes with both mass fractions exhibit better long - cycle stability. In particular, the cell assembled with 10% 2M ZnSO4 grid - shaped hydrogel can be stably cycled for up to 1000 hours, while the one with 20% can be stably cycled for 400 hours, but also shows a trend of increasing polarization voltage in the later stage. This indicates that the 10% 2M ZnSO4 grid - shaped hydrogel electrolyte has better performance in the long - cycle stability of symmetric cells.

[0084] The inventor further adjusted the current condition to 0.1 mA·cm -2 / 0.1 mAh·cm -2 and conducted a galvanostatic charge - discharge test on the Zn||Zn symmetric cell assembled with 10% grid - shaped hydrogel electrolyte, as shown in Figure 5 c.

[0085] As can be seen from Figure 5 c: The cell assembled with this electrolyte can be stably cycled for 1800 hours under this condition, while maintaining a polarization voltage below 50 mV, which further demonstrates its advantage in improving the long - cycle stability of the cell.

[0086] The inventor tested the 10% / 20% - 2M ZnSO4 grid - shaped hydrogel electrolytes that were successfully configured and showed good long - cycle stability at different gradient current densities, keeping the fixed deposition capacity of 1 mAh·cm -2 unchanged, and conducted galvanostatic charge - discharge tests on Zn||Zn symmetric cells with current densities of 1, 3, 5, and 10 mA·cm -2 respectively. The test results are shown in Figure 5 d.

[0087] As can be seen from Figure 5 d: The cell assembled with 10% - 2M ZnSO4 grid - shaped hydrogel electrolyte can be cycled at different current densities and still maintain good performance when returning to a current density of 1 mA·cm -2 , demonstrating its wide applicability and excellent cycle stability.

[0088] The inventor assembled the hydrogel battery separator prepared in Example 1 with the cathode material VO2 and metallic zinc into a Zn||VO2 cell, and conducted a capacity comparison test on 2M ZnSO4 and 10% - 2M ZnSO4 grid - shaped hydrogel electrolytes at different current densities, as shown in Figure 6As shown. During the test, at current densities of 0.1, 0.2, 0.3, 0.5, 0.8, 1, and 2 A·g -1 respectively, each cycle was repeated five times.

[0089] As Figure 6 shown in a, the Zn||VO2 battery using a 10%-2M ZnSO4 meshed hydrogel electrolyte exhibited higher stability and high specific capacity performance than the 2M ZnSO4 basic electrolyte at all tested current densities, indicating its higher energy density.

[0090] The inventor used a current density of 0.2 A·g -1 to conduct a constant current charge-discharge long cycle test on the prepared Zn||VO2 battery. The test results are as Figure 6 shown in b. The results show that the battery using the 2M ZnSO4 electrolyte showed overcharge after 28 cycles, and the specific capacity decreased significantly in subsequent cycles. However, the battery using the 10%-2M ZnSO4 meshed hydrogel electrolyte still maintained a specific capacity of 210 mAh·g -1 after 200 charge-discharge cycles, and the capacity retention rate reached 90%.

[0091] The inventor used a current density of 5 A·g -1 to conduct a constant current charge-discharge long cycle test on the prepared Zn||VO2 battery. The test results are as Figure 6 shown in c. The results show that the traditional aqueous electrolyte of 2M ZnSO4 could not effectively complete the charge-discharge cycle, while the battery using the 10%-2M ZnSO4 meshed hydrogel electrolyte could stably cycle 1000 times and finally reached a specific capacity of 80 mAh·g -1 with a capacity retention rate of 82%.

[0092] The inventor observed the growth status of zinc dendrites at the interface between the Zn||Zn symmetric battery electrode and the electrolyte and on the zinc negative electrode interface after cycling the hydrogel battery separator using Example 1 by scanning electron microscopy (SEM). The results are as Figure 7 shown. The cycling conditions were a current density of 1 mA·cm -2 / 1 mAh·cm -2 .

[0093] From Figure 7 a and Figure 7 b, it can be seen that on the zinc metal negative electrode interface using the 2M ZnSO4 basic electrolyte, hexagonal plate-like zinc metal dendrites were presented. These dendrites grew, extended, and branched irregularly, forming a complex structure and network morphology. This irregular growth pattern seriously damaged the stability of the battery interface and affected the cycling stability of the insertion / extraction process. Figure 7 c andFigure 7 d shows the SEM images of the zinc negative electrode interface of the battery assembled with a 10%-2M ZnSO4 grid hydrogel electrolyte. In contrast, it can be found that the growth morphology of zinc dendrites has changed significantly. The originally multi-edged hexagonal shape has become more uniform, and the dendrites can be tiled on the zinc metal electrode interface. This uniform deposition effectively ensures the stable settlement of zinc ions, thus greatly improving the long-cycle stability of the battery.

[0094] It can be seen from this that the 10%-2M ZnSO4 grid hydrogel electrolyte not only exhibits excellent performance in the constant current charge-discharge test, but also has obvious advantages in inhibiting the growth of zinc dendrites.

[0095] The inventor assembled a Zn||Cu battery with the hydrogel battery separator prepared in Example 1 and tested it. The test conditions were as follows: at current densities of 1 and 10 mA·cm -2 , and deposition capacities of 1 and 10 mAh·cm -2 , the charging deposition time was 1 hour each time, and the deposition of zinc ions on the Cu metal foil of the positive electrode under different electrolyte conditions was observed. As Figure 8 shown.

[0096] Based on the test at a small current density, from the Figure 8 SEM images from a to b on the left, it can be seen that in the battery using the 2M ZnSO4 basic electrolyte, the zinc dendrites grown on the Cu foil appear in a cluster state and maintain their typical hexagonal plate-like morphology. This irregular growth mode greatly affects the stability of the electrode interface and the battery performance. In contrast, Figure 8 c to d on the left show that in the battery using the 10%-2M ZnSO4 grid hydrogel electrolyte under the same charging deposition conditions, similar to the case of the symmetric battery, the growth of zinc dendrites becomes more uniform, and a "smooth" zinc metal layer is formed on the electrode interface. This indicates that the spatially networked hydrogel structure effectively guides the uniform deposition of zinc ions and avoids the growth of irregular dendrites.

[0097] Based on the test at a large current density, the growth rate of zinc dendrites in the battery using the 2M ZnSO4 basic electrolyte is significantly accelerated, forming a morphology of layer-by-layer iteration and flat growth. Nevertheless, the battery using the 10%-2M ZnSO4 grid hydrogel electrolyte still exhibits better zinc ion deposition behavior, reducing the generation of disordered dendrites, thus protecting the electrode interface.

[0098] It can be seen from this that the spatially networked hydrogel electrolyte designed by the present invention can not only exhibit excellent performance in the constant current charge and discharge test, but also effectively inhibit the disordered growth of zinc dendrites and improve the long-cycle stability of the battery. Especially in the protection of the zinc metal negative electrode, this new electrolyte shows significant advantages, demonstrating its great potential in improving the battery performance.

[0099] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A hydrogel electrolyte material for zinc ion batteries, characterized in that: The invention comprises the following components by weight: 131 to 524 parts of acrylamide, 140 to 561 parts of ethylene glycol ditetraacetic acid, 228 to 916 parts of isocyanoethyl methacrylate, 1150 parts of zinc sulfate heptahydrate and pure water.

2. The hydrogel electrolyte material according to claim 1, characterized in that The material also includes 10 to 50 parts of an initiator.

3. The hydrogel electrolyte material according to claim 2, characterized in that The initiator is ammonium persulfate or potassium persulfate.

4. A method for preparing a hydrogel electrolyte material for zinc ion batteries according to any one of claims 1 to 3, characterized in that: The following steps are involved: Zinc sulfate heptahydrate, acrylamide, ethylene glycol ditetraacetic acid and isocyanoethyl methacrylate were stirred and mixed in pure water, and then an initiator was added, and the mixture was stirred continuously and then allowed to stand to prepare a hydrogel electrolyte for zinc ion batteries.

5. The method for preparing a hydrogel electrolyte material according to claim 4, characterized in that: The stirring and mixing time is 2 to 4 hours; the continued stirring time is 12 to 20 minutes.

6. A method for preparing a hydrogel battery separator, comprising a battery separator, characterized in that: The battery separator is immersed in the hydrogel electrolyte material for zinc ion batteries according to any one of claims 1 to 3, and cured to obtain a hydrogel battery separator.

7. The method for preparing a hydrogel battery separator according to claim 6, characterized in that: The soaking time is 18 to 24 hours; the curing time is 5 to 8 minutes.

8. A hydrogel battery separator, characterized in that: The method is prepared according to claim 6 or 7.

9. Use of the hydrogel battery separator as claimed in claim 8 in zinc ion batteries.

10. A zinc ion battery, characterized in that: Comprising the hydrogel battery separator as claimed in claim 8.

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