Zinc ion battery electrolyte containing polysaccharide zinc chelate as well as preparation method and application of zinc ion battery electrolyte

Abstract

The invention relates to a zinc ion battery electrolyte containing polysaccharide zinc chelate as well as a preparation method and application thereof, the electrolyte comprises a deionized water solvent, a soluble zinc salt solute and a polysaccharide zinc chelate additive, and the addition amount of the polysaccharide zinc chelate additive is 0.20 mmol / L to 1.35 mmol / L; the polysaccharide zinc chelate additive is any one or more of zinc hyaluronate, zinc tannate, algal polysaccharide zinc, rice bran polysaccharide zinc chelate and multiflower knotweed vine polysaccharide chelated zinc. A trace amount of green and safe polysaccharide zinc chelate additive is added into the zinc salt water electrolyte, so that on one hand, hydrogen evolution side reaction is effectively inhibited, and on the other hand, dendritic crystal growth on the surface of a negative electrode is inhibited; when the electrolyte is applied to the aqueous zinc ion battery, the cycle stability of the battery can be remarkably improved, and the cycle life of the zinc ion battery is effectively prolonged.

Description

Technical Field

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

[0002] With the rapid development of renewable energy, batteries, as an important part of energy storage systems, need to meet the requirements of high safety, low cost, and long life. Compared with traditional lithium-ion batteries, aqueous batteries have the advantages of intrinsic safety, environmental protection, and long cycling life, and are the most powerful competitors for next-generation large-scale energy storage battery technologies. Aqueous zinc-ion batteries (AZIBs) have a high theoretical specific capacity (820 mAh•g -1 and 5855 mAh•cm -3 ), a low electrode potential (-0.76 V vs standard hydrogen electrode), as well as advantages such as low cost, high safety, and environmental friendliness, and are regarded as strong competitors to lithium-ion batteries and have received much attention.

[0003] At present, the industrialization of aqueous zinc-ion batteries is still in its infancy, and the research results in the laboratory have not been well verified in large-scale tests. Mainly, problems such as zinc anodes (dendrites, corrosion, hydrogen evolution) and cathodes (dissolution, structural collapse) seriously limit the cycle life and Coulomb efficiency of the batteries. Currently, the use of electrolyte additives to optimize the stability of zinc-ion batteries has been widely studied. Among the reported electrolyte additives for zinc-ion batteries, Patent CN115332646A discloses an electrolyte for zinc-ion batteries using organic small molecule compounds such as dimethyl sulfoxide and N,N-dimethylformamide that are completely or partially soluble in water as additives, and uses organic solvents to weaken the hydrogen bonds of water to inhibit the hydrogen evolution reaction, effectively improving the high-temperature performance of the battery. Patent CN113948779A uses oxygen-containing salts or organic small molecule compounds containing S and F substitution groups as additives, which can form an inorganic solid protective film on the surface of the electrode material and improve the cycle stability of the battery material. However, most of these organic small molecule compounds are organic solvents with certain toxicity, and the addition concentration in the electrolyte is relatively high (0.05 - 0.5 mol / L), making it difficult to meet the requirements of safety, environmental protection, and low cost for aqueous zinc-ion batteries.

[0004] Organic polymer chemicals have the advantages of high stability, characteristic structure and adjustable functional group design, and are increasingly being used as additives to improve the performance of aqueous zinc-ion batteries. Patent CN114388903 A uses a green and safe carboxymethyl cellulose as an electrolyte additive for zinc-ion batteries, and uses a large number of highly hydrophilic hydroxyl functional groups on the carboxymethyl cellulose polymer to regulate the zinc ion solvation structure, thereby alleviating zinc dendrite growth and extending battery life. However, although this type of additive with only a single action site can optimize zinc deposition / stripping behavior to a certain extent, it is still difficult to achieve long-term and stable interface regulation under trace addition conditions. Summary of the invention

[0005] In view of the current technical deficiencies, the present invention provides a zinc ion battery electrolyte containing polysaccharide zinc chelate, a preparation method and an application thereof. The present invention adds a trace amount of green and safe polysaccharide zinc chelate additives to a zinc salt electrolyte, and utilizes the bifunctional sites of the hydrophilic group and the zinc-philic coordination group in the polysaccharide zinc chelate structure. On the one hand, the zinc ion solvation structure is optimized by reducing the number of active water molecules, thereby inhibiting the hydrogen evolution side reaction, and on the other hand, uniform zinc ion deposition is achieved by constructing a zinc ion directional transmission channel, thereby inhibiting the growth of dendrites on the negative electrode surface. The electrolyte is applied to an aqueous zinc ion battery, which can significantly improve the cycle stability of the battery and effectively extend the cycle life of the zinc ion battery.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: A zinc ion battery electrolyte containing polysaccharide zinc chelate, the electrolyte comprising a deionized water solvent, a soluble zinc salt solute and a polysaccharide zinc chelate additive, wherein the addition amount of the polysaccharide zinc chelate additive is 0.20 mmol / L to 1.35 mmol / L; the polysaccharide zinc chelate additive is any one or more of zinc hyaluronate, zinc tannate, seaweed polysaccharide zinc, rice bran polysaccharide zinc chelate, and Polygonum multiflorum polysaccharide zinc chelate.

[0007] Preferably, the soluble zinc salt solute is any one or more of zinc sulfate, zinc acetate, zinc nitrate, zinc chloride, zinc bromide, zinc trifluoromethanesulfonate, and zinc iodide.

[0008] Preferably, the concentration of the soluble zinc salt solute is 0.5 mol / L to 4.0 mol / L.

[0009] Preferably, the polysaccharide zinc chelate additive is hyaluronic acid zinc (HA-Zn), the molecular formula of which is [Zn(C 14 H 20 O 11 N)2] n , molecular weight is 30,000 to 50,000 Da.

[0010] Preferably, the addition amount of the polysaccharide zinc chelate additive is 0.50 mmol / L. The addition amount of the polysaccharide zinc chelate additive in the present invention can achieve long-term and stable interfacial regulation under the conditions of trace or even ultra-trace addition.

[0011] The present invention also provides a method for preparing the zinc-ion battery electrolyte containing the polysaccharide zinc chelate, which includes the following steps: Step S1: Mix the soluble zinc salt and deionized water in a certain proportion, and ultrasonically dissolve it at room temperature until the solution is completely clear, transparent and free of precipitation to obtain a mixed solution; Step S2: Add the polysaccharide zinc chelate additive to the mixed solution in Step S1, and ultrasonically dissolve it until the polysaccharide zinc chelate additive is completely dissolved to obtain an aqueous zinc-ion battery electrolyte.

[0012] In addition, the present invention also provides the application of the above-mentioned zinc-ion battery electrolyte containing the polysaccharide zinc chelate in an aqueous zinc-ion battery.

[0013] Preferably, the aqueous zinc-ion battery is any one of a zinc-zinc symmetric battery (Zn||Zn symmetric battery), a zinc-copper half-cell (Zn||Cu half-cell), and a zinc-vanadium dioxide full-cell (Zn||VO2 full-cell).

[0014] Preferably, the zinc-zinc symmetric battery is composed of a 50-μm-thick zinc foil, a glass fiber separator, and an aqueous zinc-ion battery electrolyte; the zinc-copper half-cell is composed of a commercial 50-μm-thick zinc foil, a commercial copper foil current collector, a glass fiber separator, and an aqueous zinc-ion battery electrolyte; the zinc-vanadium dioxide full-cell is composed of a commercial 50-μm-thick zinc foil, a commercial vanadium dioxide positive electrode sheet, and an aqueous zinc-ion battery electrolyte.

[0015] Preferably, the zinc-zinc symmetric battery stably cycles for more than 4700 hours at a current density of 1 mA•cm -2 and a capacity density of 1 mAh•cm -2 ; the zinc-copper half-cell cycles more than 1400 times at a current density of 5 mA•cm -2 and a capacity density of 1 mAh•cm -2 .

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The long-lasting aqueous zinc-ion battery electrolyte prepared in the present invention has a large number of strongly hydrophilic groups such as hydroxyl groups, carboxyl groups, and phosphate groups in its polysaccharide zinc chelate additive. The strong hydrogen bond action of these groups greatly reduces the activity of free water molecules, and at the same time will spontaneously preferentially adsorb on the surface of the zinc negative electrode to form a uniform zinc negative electrode interface protection layer, thereby inhibiting the occurrence of hydrogen evolution corrosion and side reactions, and improving the cycle stability and long-term performance.

[0017] 2. In the present invention, the molecular structure of the polysaccharide zinc chelate additive simultaneously contains zincophilic coordination groups, and these specific sites construct a directional transport and migration channel for zinc ions from the electrolyte to the zinc negative electrode interface, thereby realizing the uniform deposition of zinc ions on the surface of the negative electrode and effectively inhibiting the growth of dendrites.

[0018] 3. On the basis of not changing the basic physical properties such as the pH value and viscosity of the aqueous zinc ion battery electrolyte and not modifying the typical battery assembly process, by adding a trace amount of a green, low-cost and highly safe polysaccharide zinc chelate additive, the electrochemical properties such as the cycle stability and corrosion resistance of the zinc negative electrode are significantly improved. The zinc-zinc symmetric battery using the long-lasting aqueous zinc ion battery electrolyte of the present invention can stably cycle for more than 4700 hours at a current density of 1 mA·cm -2 and a capacity density of 1 mAh·cm -2 , and the zinc-copper half-cell can cycle more than 1400 times at a current density of 5 mA·cm -2 and a capacity density of 1 mAh·cm -2 . Description of the Drawings

[0019] Figure 1 In (a), it is an image of a commercial zinc sheet after being immersed in the electrolyte of Example 1 for 12 days; Figure 1 In (b), it is an image of a commercial zinc sheet after being immersed in the electrolyte of Example 2 for 12 days; Figure 1 In (c), it is an image of a commercial zinc sheet after being immersed in the electrolyte of Comparative Example 1 for 12 days; Figure 2 In (a), it is a nano-infrared imaging diagram of the surface ether bond functional groups of a commercial zinc sheet after being immersed in the electrolyte of Example 1 for 12 days, rinsed and dried; Figure 2 In (b), it is a nano-infrared imaging diagram of the surface ether bond of a commercial zinc sheet after being immersed in the electrolyte of Comparative Example 1 for 12 days, rinsed and dried; Figure 2 In (c), it is a nano-infrared imaging diagram of the surface carboxyl functional groups of a commercial zinc sheet after being immersed in the electrolyte of Example 3 for 12 days, rinsed and dried; Figure 2 In (d), it is a nano-infrared imaging diagram of the carboxyl functional groups of a commercial zinc sheet after being immersed in the electrolyte of Comparative Example 1 for 12 days, rinsed and dried; Figure 3 In (a), it is an SEM image of the surface of a commercial zinc sheet after electroplating at a current density of 5 mA·cm -2 for 1 h in the electrolyte of Example 1; Figure 3 In (b), it is an SEM image of the surface of a commercial zinc sheet after electroplating at a current density of 5 mA·cm -2 for 1 h in the electrolyte of Example 2; Figure 3In (c), it is the SEM image of the surface of a commercial zinc sheet after electroplating for 1 h at a current density of 5 mA·cm -2 in the electrolyte of Example 4; Figure 3 In (d), it is the SEM image of the surface of a commercial zinc sheet after electroplating for 1 h at a current density of 5 mA·cm -2 in the electrolyte of Comparative Example 1; Figure 4 are the Coulomb efficiency test comparison curves of half-cells assembled with a commercial zinc sheet, a copper foil, and the 2M zinc sulfate aqueous solution obtained in Comparative Example 1 and the aqueous zinc-ion battery composite electrolytes containing zinc polysaccharide chelate additives in Example 1, Example 3, and Comparative Example 2 at a current density of 5 mA·cm -2 and a capacity density of 1 mAh·cm -2 ; Figure 5 are the time-voltage comparison diagrams of the cycle stability test of symmetric cells assembled with a commercial zinc sheet and the 2M zinc sulfate aqueous solution obtained in Comparative Example 1 and the aqueous zinc-ion battery composite electrolytes containing zinc polysaccharide chelate additives in Example 1, Example 4, and Comparative Example 3 at a current density of 1 mA·cm -2 and a capacity density of 1 mAh·cm -2 ; Figure 6 are the discharge specific capacity and Coulomb efficiency diagrams of full cells assembled with commercial VO2 and the 2M zinc sulfate aqueous solution obtained in Comparative Example 1 and the aqueous zinc-ion battery composite electrolyte containing zinc polysaccharide chelate additive in Example 1 during cycling at a current density of 1 A·g -1 ; Detailed Embodiments

[0020] The technical solutions of the present invention will be further specifically described below through examples. These examples are for the purpose of illustrating the present invention and not for limiting it. All other examples obtained by those of ordinary skill in the art based on the examples in this application without creative efforts shall fall within the scope of protection of this application.

[0021] The test methods used in the examples are all conventional methods unless otherwise specified; the reagents and materials used are all commercially available unless otherwise specified.

[0022] Example 1 Preparation of electrolyte: Weigh 5.74 g of zinc sulfate heptahydrate (ZnSO4·7H2O) and dissolve it in 7.48 mL of deionized water to prepare a 2 mol / L (M) ZnSO4 solution for later use. Add 0.2 g of zinc hyaluronate (HA-Zn) powder (Mw = 40,000 Da) to the above ZnSO4 solution, and place it in an ultrasonic cleaner and shake until completely dissolved to obtain a colorless and clear electrolyte with a zinc hyaluronate concentration of 0.50 mmol / L.

[0023] Battery assembly: Take a commercial zinc foil with a thickness of 50 µm, cut a zinc electrode sheet with a diameter of φ12 mm, wash it with absolute ethanol and dry it for later use; take a glass fiber separator, cut a round piece with a diameter of φ16 mm for later use; take a commercial copper foil current collector, cut a copper current collector round piece with a diameter of φ12 mm, wash it with absolute ethanol and dry it for later use. Take a commercial VO2 electrode sheet, cut a VO2 current collector round piece with a diameter of φ12 mm, wash it with absolute ethanol and dry it for later use. Stack the zinc electrode sheet, separator, and zinc electrode sheet in sequence and place them in a CR2032-type battery case, and drop 60 µL - 100 µL of electrolyte to moisten its interior to assemble a CR2032-type Zn||Zn symmetric button battery, denoted as Zn||Zn-(HA-Zn). 0.50 Stack the copper current collector, separator, and zinc electrode sheet in sequence and place them in a CR2032-type battery case, and drop 60 µL - 100 µL of electrolyte to moisten its interior to assemble a CR2032-type Zn||Cu button half-cell, denoted as Zn||Cu-(HA-Zn). 0.50 Stack the VO2 current collector, separator, and zinc electrode sheet in sequence and place them in a CR2032-type battery case, and drop 60 µL - 100 µL of electrolyte to moisten its interior to assemble a CR2032-type Zn||VO2 button full cell, denoted as Zn||VO2-(HA-Zn). 0.50 。

[0024] Battery testing: The testing method for the Zn||Zn symmetric battery is as follows: Constant current charge and discharge at a current density of 1 mA / cm 2 until 1 mAh / cm 2 , and cycle like this. The testing method for the Zn||Cu half-cell is as follows: Constant current discharge at a current density of 5 mA / cm 2 for 12 min and then constant current charge to 1 V at the same current density, and cycle like this. The testing method for the Zn||VO2 full cell is as follows: Perform charge and discharge testing at a current density of 1 A·g -1 . In addition, perform Tafel corrosion current testing on the Zn||Zn symmetric battery, with parameters of -0.25 V - 0.25 V and a scanning rate of 1 mV / s.

[0025] Physical and chemical property analysis: The zinc sheet was electroplated at a current density of 5 mA·cm -2 in a 2 M zinc sulfate electrolyte containing 0.50 mmol / L zinc hyaluronate additive for 1 h, and then the surface morphology of the zinc sheet was characterized by scanning electron microscopy; after the zinc sheet was immersed in a 2 M zinc sulfate electrolyte containing 0.50 mmol / L zinc hyaluronate additive for 12 days, rinsed and dried, the distribution of zinc hyaluronate characteristic groups on the surface of the zinc sheet was characterized by nano-infrared spectroscopy.

[0026] Example 2 In this example, a parallel test similar to that of Example 1 was carried out. The concentration of zinc hyaluronate in the electrolyte was 0.25 mmol / L, and the rest of the operation steps were the same as those in Example 1, and a colorless and clear electrolyte was obtained. At the same time, button cells were assembled in the same manner as in Example 1, where the Zn||Zn symmetric cell and the Zn||Cu half-cell were denoted as Zn||Zn-(HA-Zn) 0.25 and Zn||Cu-(HA-Zn) 0.25 respectively.

[0027] Example 3 In this example, a parallel test similar to that of Example 1 was carried out. Zinc tannate was used as an electrolyte additive with a concentration of 0.50 mmol / L (Mw = 40,000 Da), and the rest of the operation steps were the same as those in Example 1, and a colorless and clear electrolyte was obtained. At the same time, button cells were assembled in the same manner as in Example 1, where the Zn||Zn symmetric cell and the Zn||Cu half-cell were denoted as Zn||Zn-(CHO-Zn) 0.50 and Zn||Cu-(CHO-Zn) 0.50 respectively.

[0028] Example 4 In this example, a parallel test similar to that of Example 3 was carried out. The concentration of zinc tannate in the electrolyte was 0.25 mmol / L, and the rest of the operation steps were the same as those in Example 3, and a colorless and clear electrolyte was obtained. At the same time, button cells were assembled in the same manner as in Example 1, where the Zn||Zn symmetric cell and the Zn||Cu half-cell were denoted as Zn||Zn-(CHO-Zn) 0.25 and Zn||Cu-(CHO-Zn) 0.25 respectively.

[0029] Comparative Example 1 In this comparative example, no additive was added, and the electrolyte was only a 2 mol / L ZnSO4 solution. All other operating steps were the same as those in Example 1. Meanwhile, button cells were assembled and tested in the same manner as in Example 1. Among them, the Zn||Zn symmetric cell, Zn||Cu half-cell, and Zn||VO2 full cell were denoted as Zn||Zn-Blank, Zn||Cu-Blank, and Zn||VO2-Blank, respectively.

[0030] Comparative Example 2 In this comparative example, 0.02 g of zinc hyaluronate was weighed using a high-precision balance and added to 7.48 mL of 2 M (mol / L) ZnSO4 solution to obtain an electrolyte with a concentration of 0.05 mmol / L. All other operating steps were the same as those in Example 1. Meanwhile, button cells were assembled and tested in the same manner as in Example 1. Among them, the Zn||Zn symmetric cell and Zn||Cu half-cell were denoted as Zn||Zn-(HA-Zn) 0.05 and Zn||Cu-(HA-Zn) 0.05 .

[0031] Comparative Example 3 In this comparative example, 0.004 g of zinc tannate was weighed using a high-precision balance and added to 7.48 mL of 2 M (mol / L) ZnSO4 solution to obtain an electrolyte with a concentration of 0.01 mmol / L. All other operating steps were the same as those in Example 1. Meanwhile, button cells were assembled and tested in the same manner as in Example 1. Among them, the Zn||Zn symmetric cell and Zn||Cu half-cell were denoted as Zn||Zn-(HA-Zn) 0.01 and Zn||Cu-(HA-Zn) 0.01 .

[0032] Analysis of Physicochemical Properties and Testing of Electrochemical Performance Observe the zinc sheets soaked in the electrolyte in Example 1, Example 2, and Comparative Example 1. As Figure 1 shown, specifically, the image of the commercial zinc sheet soaked in the aqueous zinc-ion battery electrolyte containing the polysaccharide zinc chelate additive in Example 1 after 12 days is as shown in Figure 1 (a); the image of the commercial zinc sheet soaked in the aqueous zinc-ion battery electrolyte containing the polysaccharide zinc chelate additive in Example 2 after 12 days is as shown in Figure 1 (b); the image of the commercial zinc sheet soaked in the 2 M zinc sulfate aqueous solution electrolyte obtained in Comparative Example 1 after 12 days is as shown in Figure 1 (c). From Figure 1 (a), Figure 1 (b), and Figure 1As can be seen from (c) in the figure, a white substance is adsorbed on the surface of the zinc sheets in Example 1 and Example 2; while no white substance is found on the surface of the zinc sheet in Comparative Example 1, but a layer of shiny by-product basic zinc sulfate Zn4SO4(OH)6·5H2O is distributed, which preliminarily proves the adsorption distribution of zinc hyaluronate and zinc tannate on the zinc negative electrode, as well as the protective effect on the zinc negative electrode.

[0033] Since the molecular structures of zinc hyaluronate and zinc tannate contain characteristic groups such as ether bonds and carboxyl groups, as Figure 2 shown, a nano-infrared spectrometer was further used to characterize the distribution of characteristic groups on the surface of the dried zinc sheet. Specifically, the nano-infrared imaging map of the ether bond functional groups on the surface of a commercial zinc sheet after being soaked in the aqueous zinc ion battery electrolyte containing a polysaccharide zinc chelate additive in Example 1 for 12 days, rinsed and dried is as shown in Figure 2 Figure (a) in the figure; the nano-infrared imaging map of the ether bond on the surface of a commercial zinc sheet after being soaked in the 2M zinc sulfate aqueous solution electrolyte obtained in Comparative Example 1 for 12 days, rinsed and dried is as shown in Figure 2 Figure (b) in the figure; the nano-infrared imaging map of the carboxyl functional groups on the surface of a commercial zinc sheet after being soaked in the aqueous zinc ion battery electrolyte containing a polysaccharide zinc chelate additive in Example 3 for 12 days, rinsed and dried is as shown in Figure 2 Figure (c) in the figure; the nano-infrared imaging map of the carboxyl functional groups on the surface of a commercial zinc sheet after being soaked in the 2M zinc sulfate aqueous solution electrolyte obtained in Comparative Example 1 for 12 days, rinsed and dried is as shown in Figure 2 Figure (d) in the figure. It can be seen that obvious ether bond signals can be found on the surface of the zinc sheet in Example 1 ( Figure 2 Figure (a) in the figure), and obvious carboxyl signals can be found on the surface of the zinc sheet in Example 3 ( Figure 2 Figure (c) in the figure), and both are evenly distributed on the surface of the zinc sheet, indicating that both zinc hyaluronate and zinc tannate are evenly adsorbed on the surface of the zinc sheet, and it also proves the uniform distribution of zinc ion transport shuttle sites (zincophilic coordination structures) on it, which creates excellent conditions for the directional screening transport and uniform deposition of zinc ions. On the contrary, no ether bond and carboxyl signals are observed on the surface of the zinc sheet soaked in the zinc sulfate electrolyte in Comparative Example 1 ( Figure 2 Figure (b) in the figure, Figure 2 Figure (d) in the figure).

[0034] The deposition morphologies on the surfaces of the zinc negative electrodes in Example 1, Example 2, Example 4, and Comparative Example 1 were characterized by SEM, as shown in Figure 3 shown. Specifically, the SEM image of the surface of a commercial zinc sheet after electroplating at a current density of 5 mA·cm -2 in the composite electrolyte of the aqueous zinc ion battery containing a polysaccharide zinc chelate additive in Example 1 for 1 h is as shown in Figure 3as shown in (a) of; the SEM image of the surface of commercial zinc sheet after electroplating for 1 h at a current density of 5 mA·cm in the aqueous zinc-ion battery composite electrolyte containing polysaccharide zinc chelate additive in Example 2 is as -2 shown in Figure 3 (b) of; the SEM image of the surface of commercial zinc sheet after electroplating for 1 h at a current density of 5 mA·cm in the aqueous zinc-ion battery composite electrolyte containing polysaccharide zinc chelate additive in Example 4 is as -2 shown in Figure 3 (c) of; the SEM image of the surface of commercial zinc sheet after electroplating for 1 h at a current density of 5 mA·cm in the 2M zinc sulfate aqueous solution electrolyte obtained in Comparative Example 1 is as -2 shown in Figure 3 (d) of.

[0035] Since the uniform distribution of polysaccharide zinc chelate on the zinc surface can construct a directional transport channel for zinc ion shuttle, in Example 1 ( Figure 3 (a) of), Example 2 ( Figure 3 (b) of), Example 4 ( Figure 3 (c) of), zinc ions show a horizontal growth deposition behavior, and are stacked parallel and orderly on the negative electrode surface as a whole, finally forming a uniform, dense, nucleated and refined deposition structure, effectively inhibiting the growth of zinc dendrites; while in Comparative Example 1 ( Figure 3 (d) of), the two-dimensional diffusion behavior of zinc ions is obvious, and unevenly stacked zinc clusters are formed on the negative electrode surface, with larger and more dispersed crystal nuclei. The SEM imaging results also show that the addition of hydrophilic polysaccharide zinc chelate additive helps to form a uniform zinc deposition morphology.

[0036] Zn||Cu-(HA-Zn) in Example 1 0.50 , Zn||Cu-(CHO-Zn) in Example 3 0.50 , Zn||Cu-Blank in Comparative Example 1 and Zn||Cu-(HA-Zn) in Comparative Example 2 0.50 The Coulomb efficiency and cycle life curves of the coin-type half-cells are as Figure 4 shown. In Comparative Example 1 and Comparative Example 2, the number of stable cycles is less than 160 and 180 respectively at a current density of 5 mA·cm -2 and a capacity density of 1 mAh·cm -2 , and the Coulomb efficiencies are only 99.1% and 99.26% respectively, showing poor cycle performance. Since the polysaccharide zinc chelate additive contains a large number of hydrophilic hydroxyl groups and zincophilic coordination structures, which can effectively inhibit the hydrogen evolution side reaction and dendrite growth, Example 1 and Example 3 at a current density of 5 mA·cm -2 and a capacity density of 1 mAh·cm -2The zinc-ion battery with long cycle performance and high rate performance can stably cycle for more than 1400 cycles and 850 cycles respectively under the capacity density, and has Coulomb efficiencies as high as 99.65% and 99.59% respectively, which can significantly improve the cycle life and Coulomb efficiency.

[0037] Zn||Zn-(HA-Zn) in Example 1 0.50 、Zn||Cu-(CHO-Zn) in Example 4 0.25 、Zn||Zn-Blank in Comparative Example 1 and Zn||Cu-(CHO-Zn) in Comparative Example 3 0.01 The cycle stability and cycle life curves of the symmetric coin cells are as Figure 5 shown. In Example 1 and Example 4, at a current density of 1 mA·cm -2 and a capacity density of 1 mAh·cm -2 , they can stably cycle for more than 4700 h and 3100 h, showing excellent cycle stability and life; while in Comparative Example 1 and Comparative Example 3, at a current density of 1 mA·cm -2 and a capacity density of 1 mAh·cm -2 , the stable cycle time is less than 120 h and 190 h, and their cycle stability and life are far lower than those of Example 1 and Example 4. The test results of the Zn-Zn symmetric battery prove that the addition of trace polysaccharide zinc chelate can effectively extend the cycle life and stability of the battery.

[0038] Zn||VO2-(HA-Zn) in Example 1 0.50 and the capacity retention and cycle life curves of the Zn||VO2-Blank coin full cells in Comparative Example 1 are as Figure 6 shown. The full cell in Example 1 can stably cycle up to 910 cycles at a current density of 1 A·g -1 without obvious capacity decay; while the full cell in Comparative Example 1 at a current density of 1 A·g -1 has a significant drop in capacity retention to below 60% after 209 charge-discharge cycles. The full cell test results prove that the addition of trace polysaccharide zinc chelate has a significant effect on improving the capacity retention and cycle life of the battery.

[0039] In summary, the polysaccharide zinc chelate additive in the present invention contains a large number of hydrophilic groups and zincophilic coordination groups. Among them, strongly hydrophilic groups such as hydroxyl, carboxyl, and phosphate groups have strong hydrogen bond effects, which can greatly reduce the activity of free water molecules, optimize the solvation structure of zinc ions, and can spontaneously adsorb on the surface of the zinc negative electrode to form a uniform protective layer, thereby inhibiting hydrogen evolution corrosion and side reactions, and improving the cycle stability and long-term performance of the battery. At the same time, the zincophilic coordination sites in the molecular structure of the polysaccharide zinc chelate additive can serve as a directional transport and migration channel for zinc ions, thereby realizing the uniform deposition of zinc ions on the surface of the negative electrode, effectively inhibiting the growth of dendrites, and overall improving the cycle performance and rate performance of the aqueous zinc ion battery.

[0040] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present application.

Claims

1. A zinc-ion battery electrolyte containing polysaccharide zinc chelate, characterized in that: The electrolyte includes deionized water solvent, soluble zinc salt solute, and polysaccharide zinc chelate additive. The addition amount of the polysaccharide zinc chelate additive is 0.20 mmol / L to 1.35 mmol / L; the polysaccharide zinc chelate additive is any one or more of zinc hyaluronate, zinc tannate, zinc seaweed polysaccharide, zinc chelate of rice bran polysaccharide, and zinc chelate of polygonum multiflorum thunb. stem polysaccharide.

2. The zinc ion battery electrolyte containing polysaccharide zinc chelate according to claim 1, characterized in that: The soluble zinc salt solute is any one or more of zinc sulfate, zinc acetate, zinc nitrate, zinc chloride, zinc bromide, zinc trifluoromethanesulfonate, and zinc iodide.

3. The zinc ion battery electrolyte containing polysaccharide zinc chelate according to claim 1, wherein: The concentration of the soluble zinc salt solute is 0.5 mol / L to 4.0 mol / L.

4. The zinc ion battery electrolyte containing polysaccharide zinc chelate according to claim 1, characterized in that: The polysaccharide zinc chelate additive is zinc hyaluronate.

5. The zinc ion battery electrolyte containing polysaccharide zinc chelate according to claim 4, characterized in that: The addition amount of the polysaccharide zinc chelate additive is 0.50 mmol / L.

6. A method for preparing an electrolyte of a zinc ion battery containing a polysaccharide zinc chelate as described in claim 1, characterized in that It includes the following steps: Step S1: Mix the soluble zinc salt and deionized water in proportion, and ultrasonically dissolve at room temperature until the solution is completely clear, transparent, and without precipitation to obtain a mixed solution. Step S2: Add the polysaccharide zinc chelate additive to the mixed solution in Step S1, and ultrasonically dissolve until the polysaccharide zinc chelate additive is completely dissolved to obtain an aqueous zinc ion battery electrolyte.

7. Application of the zinc ion battery electrolyte of the polysaccharide zinc chelate described in Claim 1 in an aqueous zinc ion battery.

8. The application according to claim 7, wherein: The aqueous zinc ion battery is any one of a zinc-zinc symmetric battery, a zinc-copper half-cell, and a zinc-vanadium dioxide full cell.

9. The application according to claim 8, wherein: The zinc-zinc symmetric battery is composed of a 50 µm thick zinc foil, a glass fiber separator, and an aqueous zinc ion battery electrolyte; the zinc-copper half-cell is composed of a commercial 50 µm thick zinc foil, a commercial copper foil current collector, a glass fiber separator, and an aqueous zinc ion battery electrolyte; the zinc-vanadium dioxide full cell is composed of a commercial 50 µm thick zinc foil, a commercial vanadium dioxide positive electrode sheet, and an aqueous zinc ion battery electrolyte.

10. The application according to claim 8, wherein: The zinc–zinc symmetric battery exhibits stable cycling for over 4700 hours at a current density of 1 mA•cm -2 and a capacity density of 1 mAh•cm -2 . The zinc–copper half-cell undergoes cycling greater than 1400 cycles at a current density of 5 mA•cm -2 and a capacity density of 1 mAh•cm -2 .

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