Aqueous zinc battery electrolyte and preparation method thereof

Abstract

The invention relates to the technical field of aqueous zinc batteries, in particular to an aqueous zinc battery electrolyte and a preparation method thereof. The method comprises the following steps: adding cerous nitrate and hydroxyethyl cellulose (HEC) as composite additives into a zinc sulfate solution to obtain the aqueous zinc battery electrolyte; by adding rare earth cerium ions and hydroxyethyl cellulose, self-corrosion of a zinc negative electrode is effectively relieved, a hydrogen evolution reaction is inhibited, meanwhile, a negative electrode interface is regulated and controlled, zinc dendritic crystal growth is reduced, and finally the cycle stability, coulombic efficiency and long cycle life of the battery are improved. The cerous nitrate and the hydroxyethyl cellulose have good compatibility with the electrolyte and the electrode material, and no additional side reaction is caused.

Description

Technical Field

[0001] This invention relates to the field of aqueous zinc battery technology, specifically to an aqueous zinc battery electrolyte and its preparation method. Background Technology

[0002] Currently, aqueous zinc-ion batteries have become a research hotspot for large-scale energy storage systems due to their advantages such as high safety, high theoretical capacity, and high ionic conductivity. The mainstream electrolyte is an aqueous zinc sulfate system, but the zinc anode in this system faces serious problems such as corrosion, hydrogen evolution reaction, and zinc dendrite growth.

[0003] In existing solutions, electrolyte additive technology is widely used, mainly including metal ion additives, surfactant additives, SEI film-forming additives, and complexing additives. Metal ion additives (such as Bi³⁺, Pd²⁺, Co²⁺, etc.) can inhibit zinc dendrite formation by preferentially reducing and forming heterogeneous nucleation sites; surfactant additives reduce hydrogen evolution reaction by forming a protective layer through reducing interfacial tension; SEI film-forming additives can form a protective film on the negative electrode surface to isolate active water; and complexing additives stabilize zinc ions through coordination.

[0004] However, existing technologies have significant shortcomings: single additives have limited effects, metal ion additives are insufficient in inhibiting dendrite growth but not corrosion, surface-active additives have insignificant corrosion inhibition effects and may hinder the electrochemical behavior of zinc, and SEI film formation and complexing additives have poor stability under complex operating conditions. At the same time, existing additive systems cannot simultaneously address the three core issues of zinc anode corrosion, dendrite growth, and hydrogen evolution reaction, resulting in short cycle life, poor stability, and low coulombic efficiency of batteries. Furthermore, some additives have compatibility issues with electrolytes or electrode materials, which can easily trigger new side reactions and fail to meet the needs of practical applications. Summary of the Invention

[0005] The purpose of this invention is to provide an aqueous zinc battery electrolyte and its preparation method to solve the problems mentioned in the background art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for preparing an aqueous zinc battery electrolyte, comprising the following steps: Step 1: Add zinc sulfate heptahydrate to deionized water and make up to volume to prepare an electrolyte-based standard solution; Step 2: Add cerium nitrate hexahydrate to deionized water and make up to volume to prepare an inorganic additive standard solution; Step 3: Add hydroxyethyl cellulose to deionized water and make up to volume to prepare a standard solution of organic additives; Step 4: Add the inorganic additive standard solution and the organic additive standard solution to the electrolyte base standard solution and stir to prepare the aqueous zinc battery electrolyte.

[0007] Furthermore, in step 1, the concentration of zinc sulfate in the electrolyte base standard solution is 1 mol / L.

[0008] Furthermore, in step 2, the concentration of cerium nitrate in the inorganic additive standard solution is 40 g / L.

[0009] Furthermore, in step 3, the concentration of hydroxyethyl cellulose in the organic additive standard solution is 0.5 g / L.

[0010] Furthermore, in step 4, the concentration of zinc sulfate in the aqueous zinc battery electrolyte is 1 mol / L, the concentration of cerium nitrate is 0.1~1 g / L, and the concentration of hydroxyethyl cellulose is 10~20 ppm.

[0011] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The aqueous zinc battery electrolyte provided by the present invention uses rare earth cerium ions as inorganic additives and hydroxyethyl cellulose (HEC) as organic additives to form a composite additive system in zinc sulfate aqueous solution. By utilizing the synergistic effect of Ce³⁺ film formation and corrosion inhibition and HEC to adjust the electrolyte viscosity, the problems of zinc anode corrosion, dendrite growth and poor cycle stability are solved at the same time.

[0012] In this invention, the core mechanism of action of the inorganic additives is as follows: Firstly, it can form a zinc negative electrode corrosion inhibition and interface protection film.

[0013] Ce 3+ In a weakly acidic zinc sulfate electrolyte, it reacts with hydroxide ions (OH-) in the solution. − A multi-step chemical reaction occurs, forming a dense rare-earth conversion film (containing cerium hydroxide, cerium oxide, etc.) in situ, which covers the surface of the zinc anode. The key reaction equations are as follows: Step 1: Ce 3+ With OH − Combined to form cerium hydroxide precipitate: 2 Ce 3+ + 6 OH − = 2 Ce(OH)3↓ Step 2: Cerium hydroxide is further oxidized to cerium oxide: 2 Ce 3+ + 3 H2O+ 1 / 2 O2 = 2 CeO2↓+ 6 H + Step 3: Partial cerium hydroxide is continuously oxidized to generate Ce. 4+ hydroxide: 4 Ce(OH)3+ O2+ 2 H2O = 4 Ce(OH)4↓ Step 4: Tetravalent cerium hydroxide can be reversibly converted to Ce during battery charging and discharging. 3+ : Ce(OH)4+ 4 H + + e − = Ce 3+ + 4 H2O During the electrochemical reaction, Ce 3+ Through the above four steps of reaction, Ce is achieved. 3+ To Ce 4+ The change, followed by a reversible reaction, transforms into Ce. 3+ This allows for the maintenance of the dynamic stability of the rare earth conversion film on the zinc anode surface.

[0014] Secondly, Ce regulates the inhibition of zinc dendrite growth and deposition behavior. 3+ The reduction potential is higher than that of Zn 2+ Preferential reduction and formation of uniformly distributed metal sites on the zinc anode surface serve as heterogeneous nucleation centers, dispersing local current density and preventing concentrated zinc ion deposition. This nucleation regulation promotes uniform zinc deposition, alleviates the rapid dendrite growth caused by the "point effect," reduces dead zinc formation, and improves the reversibility of zinc deposition / stripping. Simultaneously, Ce... 3+ It can increase the nucleation overpotential of zinc deposition, further optimize the deposition morphology, make the zinc anode surface smoother, and reduce the risk of short circuit caused by dendrite penetration of the separator.

[0015] Third, optimize charge transfer dynamics. Ce 3+ Adsorbed at the interface between the zinc anode and the electrolyte, it can adjust the interfacial electric field distribution, reduce charge transfer resistance, and promote Zn absorption. 2+ Interfacial migration and charge exchange enhance electrochemical kinetic reaction rates, providing support for long-term cycling stability.

[0016] The auxiliary mechanism of the organic additives of this invention is as follows: On the one hand, HEC can effectively regulate the stability of the electrolyte system. As a water-soluble polymer, HEC can increase the viscosity and consistency of zinc sulfate electrolyte, improve the wettability and adhesion of the electrolyte to the electrode, maintain the uniform distribution of the electrolyte inside the battery, and reduce the problem of uneven deposition caused by local concentration gradients.

[0017] On the other hand, HEC can inhibit the corrosion reaction on the surface of the weak zinc anode. HEC adheres to the zinc anode surface through electrostatic adsorption, forming a thin adsorption film, which reduces the contact between zinc metal and active water molecules to a certain extent, lowers the hydrogen evolution reaction rate, and significantly reduces the corrosion current density. However, due to the large molecular weight of HEC, this adsorption film also forms a slight barrier layer, which has a weak inhibitory effect on the electrochemical behavior of zinc. Therefore, its corrosion inhibition effect is not significant when used alone.

[0018] The electrolyte of this invention uses Ce 3+ As the main component, by adding appropriate amounts of HEC and Ce 3+ To create a synergistic effect, with Ce 3+ The corrosion inhibition, dendrite regulation, and kinetic optimization effects of HEC are dominant. The adsorption film formed by HEC on the zinc electrode surface can assist Ce 3+ The generated conversion membrane exists stably, and Ce is enhanced through interface modification. 3+ The composite additive effectively regulates the zinc ion deposition rate and mitigates the destructive effect of dendrite growth on battery stability. XRD and SEM tests show that when the composite additive is applied, the diffraction peaks of corrosion products on the zinc anode surface almost disappear, the morphology is more regular, and the uneven deposition problem present in the presence of HEC alone is eliminated. The electrolyte of this invention significantly improves the long cycle life of the zinc electrode. Experiments show that the battery performance is optimal when its content in the electrolyte system is 10-20 ppm. Attached Figure Description

[0019] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 These are the XRD characterization results of the zinc sheet after being soaked in the electrolyte in Experiment 1 of this invention; Figure 2 These are the SEM characterization results of the zinc sheet after being soaked in the electrolyte in Experiment 1 of this invention; Figure 3 These are the Tafel polarization curve test results from Experiment 1 of this invention; Figure 4 These are the EIS AC impedance test results from Experiment 2 of this invention; Figure 5 These are the cycle stability test results of Zn||Zn symmetric cell deposition / stripping in Experiment 2 of this invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0021] All materials used in this invention are commercially available products.

[0022] Example 1: A method for preparing an aqueous zinc battery electrolyte, comprising the following steps: Step 1: Add zinc sulfate heptahydrate to deionized water and make up to volume to prepare an electrolyte base standard solution; the concentration of zinc sulfate in the electrolyte base standard solution is 1 mol / L; Step 2: Add cerium nitrate hexahydrate to deionized water and make up to volume to prepare an inorganic additive standard solution; the concentration of cerium nitrate in the inorganic additive standard solution is 40 g / L; Step 3: Add hydroxyethyl cellulose to deionized water and make up to volume to prepare an organic additive standard solution; the concentration of hydroxyethyl cellulose in the organic additive standard solution is 0.5 g / L; Step 4: Add the inorganic additive standard solution and the organic additive standard solution to the electrolyte base standard solution and stir to prepare an aqueous zinc battery electrolyte; in the aqueous zinc battery electrolyte, the concentration of zinc sulfate is 1 mol / L, the concentration of cerium nitrate is 1 g / L, and the concentration of hydroxyethyl cellulose is 10 ppm; denoted as "1M ZnSO4 + 1 g / L Ce(NO3)3 + 10 ppm HEC".

[0023] Example 2: A method for preparing an aqueous zinc battery electrolyte, comprising the following steps: Step 1: Add zinc sulfate heptahydrate to deionized water and make up to volume to prepare an electrolyte base standard solution; the concentration of zinc sulfate in the electrolyte base standard solution is 1 mol / L; Step 2: Add cerium nitrate hexahydrate to deionized water and make up to volume to prepare an inorganic additive standard solution; the concentration of cerium nitrate in the inorganic additive standard solution is 40 g / L; Step 3: Add hydroxyethyl cellulose to deionized water and make up to volume to prepare an organic additive standard solution; the concentration of hydroxyethyl cellulose in the organic additive standard solution is 0.5 g / L; Step 4: Add the inorganic additive standard solution and the organic additive standard solution to the electrolyte base standard solution and stir to prepare an aqueous zinc battery electrolyte; in the aqueous zinc battery electrolyte, the concentration of zinc sulfate is 1 mol / L, the concentration of cerium nitrate is 1 g / L, and the concentration of hydroxyethyl cellulose is 20 ppm; denoted as "1M ZnSO4 + 1 g / L Ce(NO3)3 + 20 ppm HEC".

[0024] Comparative Example 1: Without adding cerium nitrate and HEC, the electrolyte prepared was a 1 mol / L zinc sulfate pure electrolyte, denoted as "1MZnSO4".

[0025] Comparative Example 2: Without the addition of HEC, the electrolyte prepared has a zinc sulfate concentration of 1 mol / L and a cerium nitrate concentration of 1 g / L, denoted as "1M ZnSO4 + 1 g / L Ce(NO3)3".

[0026] Comparative Example 3: Without adding cerium nitrate, the electrolyte prepared has a zinc sulfate concentration of 1 mol / L and a HEC concentration of 10 ppm, denoted as "1M ZnSO4 + 10ppm HEC".

[0027] Comparative Example 4: Without adding cerium nitrate, the electrolyte prepared has a zinc sulfate concentration of 1 mol / L and a HEC concentration of 20 ppm, denoted as "1M ZnSO4 + 20ppm HEC".

[0028] Experiment 1: Zinc sheets were used as negative electrodes and tested by XRD and SEM characterization after being immersed in different electrolytes (the electrolytes prepared in Comparative Examples 1-4 and Examples 1-2) for 15 days.

[0029] Figure 1 The XRD characterization results of zinc sheets in each experimental group are shown in Figure (1a). As can be seen from Figure (1a), the characteristic peaks of by-product impurities in the zinc sheets after soaking mainly appear in the range of 10~30° in 2θ. By observing the magnified view of this range in Figure (1b), it can be found that the characteristic peaks of by-products in comparative examples 1, 3, and 4 are more obvious.

[0030] Combination Figure 2 The SEM characterization results show that when the electrolyte contains Ce³⁺, it can react with hydroxide ions in the solution to generate cerium hydroxide and cerium oxide, forming a dense protective film on the zinc surface. The SEM characterization results further support the XRD test results, showing that the diffraction peaks of the corrosion products of the zinc electrode almost disappear in the electrolyte with added cerium nitrate.

[0031] Figure 2 The SEM test results also showed that Ce³⁺ can regulate the negative electrode interface and provide uniform nucleation sites, while HEC can increase the electrolyte viscosity. The synergistic effect of the two can increase the overpotential for zinc ion nucleation and reduce local current concentration. Therefore, compared with Figure (2b), the zinc surface deposition is more uniform and there is no obvious dendrite growth in Figures (2e) and (2f), which shows that the addition of HEC produces a synergistic effect with Ce³⁺.

[0032] To further illustrate that the presence of Ce³⁺ effectively improves corrosion resistance, Tafel polarization curves were tested on zinc anodes using electrolytes prepared in Example 1, Comparative Example 1, and Comparative Example 3 (three-electrode test system, initial voltage (V) ± 0.15V, scan rate: 5mV / s). Figure 3 The results are from the Tafel polarization curve test. Figure 3 The Tafel polarization curves show that, in the electrolyte prepared in Comparative Example 3, the corrosion potential of the zinc electrode was optimized from -0.9840V to -0.9631V, effectively improving the corrosion resistance.

[0033] Experiment 2: To further illustrate Ce 3+ The effect of hydroxyethyl cellulose on the interface performance of zinc electrode / electrolyte was investigated. Zn was used as the positive and negative electrodes. Zn||Zn symmetric cells were assembled using electrolytes prepared in Examples 1-2 and Comparative Examples 1-4, and their AC impedance was tested. Figure 4 These are the results of EIS AC impedance testing. Figure 4 This indicates that the introduction of Ce into the electrolyte 3+ After the addition of the additive, the charge transfer resistance (Rct) value of the zinc electrode surface decreased significantly, while when the HEC additive acted alone, it significantly increased the charge transfer resistance of the zinc electrode surface.

[0034] To further illustrate the effect of electrolyte additives on the long-cycle stability (zinc deposition / stripping) of the zinc anode, Zn||Zn symmetric cells were assembled using electrolytes prepared in Examples 1, 1, 2, and 3, and constant current charge-discharge tests were conducted at a current density of 2 mA / cm². 2 The depth of charge / discharge is 1.0 mAh / cm. 2 . Figure 5 The results show the cycle stability test results of the zinc anode in different electrolytes.

[0035] Figure 5 As can be seen, in Comparative Example 1, the battery voltage fluctuated after approximately 200 hours of cycling; in Comparative Example 2, the voltage fluctuated after approximately 300 hours of cycling; and in Comparative Example 3, the voltage fluctuated after approximately 380 hours of cycling. In contrast, in Example 1, the battery could cycle stably for over 530 hours. The experimental results demonstrate that the synergistic effect of cerium nitrate and hydroxyethyl cellulose can significantly improve the cycling stability of zinc electrode deposition / stripping.

[0036] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0037] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An aqueous zinc battery electrolyte, comprising zinc sulfate, cerium nitrate, hydroxyethyl cellulose, and water, characterized in that: In the aqueous zinc battery electrolyte, the concentration of zinc sulfate is 1 mol / L, the concentration of cerium nitrate is 0.1~1 g / L, and the concentration of hydroxyethyl cellulose is 10~20 ppm.

2. A method for preparing the aqueous zinc battery electrolyte as described in claim 1, characterized in that: Includes the following steps: Step 1: Add zinc sulfate heptahydrate to deionized water and make up to volume to prepare an electrolyte-based standard solution; Step 2: Add cerium nitrate hexahydrate to deionized water and make up to volume to prepare an inorganic additive standard solution; Step 3: Add hydroxyethyl cellulose to deionized water and make up to volume to prepare a standard solution of organic additives; Step 4: Add the inorganic additive standard solution and the organic additive standard solution to the electrolyte base standard solution and stir to prepare the aqueous zinc battery electrolyte.

3. The preparation method according to claim 2, characterized in that: In step 1, the concentration of zinc sulfate in the electrolyte base standard solution is 1 mol / L.

4. The preparation method according to claim 2, characterized in that: In step 2, the concentration of cerium nitrate in the inorganic additive standard solution is 40 g / L.

5. The preparation method according to claim 2, characterized in that: In step 3, the concentration of hydroxyethyl cellulose in the organic additive standard solution is 0.5 g / L.

6. The preparation method according to claim 2, characterized in that: In step 4, the concentration of zinc sulfate in the aqueous zinc battery electrolyte is 1 mol / L, the concentration of cerium nitrate is 0.1~1 g / L, and the concentration of hydroxyethyl cellulose is 10~20 ppm.

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