Aqueous zinc ion battery electrolyte of difunctional additive containing ether group and nitrile group

Abstract

The invention provides an aqueous zinc ion battery electrolyte containing an ether group and nitrile group bifunctional additive. The amount of solvated water outside the solvated sheath can be remarkably reduced by utilizing strong interaction between water and ether groups, so that side reactions in electrolyte are reduced. Besides, nitrile groups are adsorbed on the surface of a zinc negative electrode, growth of a diffusion induction (002) crystal face is adjusted during zinc ion deposition, growth of zinc dendritic crystals and negative electrode corrosion caused by the electrolyte are effectively prevented, and a design thought of a novel aqueous zinc ion battery electrolyte is provided.

Description

Technical Field

[0001] This invention relates to the field of aqueous zinc-ion battery technology, and particularly to aqueous zinc-ion battery electrolytes containing ether- and nitrile-based bifunctional additives, their preparation methods, and applications. Background Technology

[0002] Aqueous zinc-ion batteries (AZIBs) have great potential for large-scale energy storage systems due to their advantages such as high safety, low cost and simple production environment requirements, which to some extent make up for the shortcomings of lithium-ion batteries. However, AZIBs suffer from irregular zinc dendrite growth and water-induced parasitic reactions during charge and discharge, resulting in poor reversibility and cycle instability of the zinc anode, which exacerbates the degradation of the electrochemical performance of AZIBs and hinders their commercialization. In recent years, in order to improve the stability of zinc anodes, a lot of work has been devoted to zinc structure optimization, surface modification, electrolyte optimization and separator design. Among them, electrolyte optimization is the easiest to operate and the lowest cost method. Adding functional additives to the electrolyte can regulate the solvation structure and form a stable passivation layer at the electrode interface. For example, (1) additives containing amino and hydroxyl groups can form a metal-organic molecular layer at the anode electrolyte interface, thereby inducing zinc ion deposition and blocking water molecules outside the metal-organic molecular layer. This method effectively solves the problems of zinc dendrites and zinc metal corrosion and significantly improves the cycle performance of zinc anodes. Meanwhile, when used in conjunction with suitable cathode materials in full batteries, it significantly slows down the capacity decay of the battery [CN116565347 A]. (2) Additives containing ketone and ester groups can change the solvation structure of zinc ions. At the same time, these additive molecules adsorb onto the surface of the zinc anode, inducing zinc ions to deposit in a more thermodynamically stable manner parallel to the (002) crystal plane, effectively solving problems such as zinc dendrite formation and hydrogen evolution reaction, and significantly improving the cycle performance of the zinc anode. In addition, this additive can be used in conjunction with suitable cathodes in batteries, effectively slowing down the capacity decay [CN 117613432 A]. Therefore, electrolyte additives for aqueous zinc-ion batteries need to have multiple types of functional groups to play different roles. However, research on such multifunctional additives is still insufficient. It is urgent to develop multifunctional additives to stabilize the zinc anode and thus improve the performance of aqueous zinc-ion batteries. Summary of the Invention

[0003] The main objective of this invention is to provide an aqueous zinc-ion battery electrolyte containing ether- and nitrile-based bifunctional additives, its preparation method, and its applications. The ether- and nitrile-based bifunctional additives of this invention can significantly improve the cycle performance of aqueous zinc-ion batteries. This invention utilizes the strong interaction between water and ether groups to significantly reduce the amount of solvated water outside the solvation sheath, thereby reducing side reactions in the electrolyte. Furthermore, the nitrile groups adsorbed on the zinc anode surface regulate the diffusion-induced (002) crystal plane growth during zinc ion deposition, effectively preventing zinc dendrite growth and electrolyte-induced anode corrosion.

[0004] To achieve the above objectives, this invention provides a method for preparing an aqueous zinc-ion battery electrolyte containing ether- and nitrile-based bifunctional additives, comprising the following steps: Step 1: Dissolve the soluble zinc salt in deionized water to obtain the basic aqueous zinc salt electrolyte; Step 2: Add bifunctional additives containing ether and nitrile groups, and let stand for 12 hours to obtain an aqueous zinc-ion battery electrolyte containing bifunctional additives containing ether and nitrile groups. The concentration of the soluble zinc salt is 0.2–4 mol / L; the amount of the bifunctional additive containing ether and nitrile groups is 1%–10% by volume, with the optimal volume ratio being 5%; the additive contains the structural formula RO-CH2CH2CN, where the R group can be -CH3, -C2H5, -CH2CH2OCH3, or -CH2CH2OCH2CH2CN, as shown in the following formula:

[0005] The present invention also provides a battery comprising the above-mentioned aqueous zinc-ion battery electrolyte.

[0006] Further, the soluble zinc salt is at least one of zinc sulfate, zinc sulfate hydrate, zinc chloride, zinc chloride hydrate, zinc acetate, zinc acetate hydrate, zinc trifluoromethanesulfonate, and zinc trifluoromethanesulfonate hydrate.

[0007] Furthermore, the battery is a symmetrical battery composed of commercially available 200µm thick zinc foil, a glass fiber separator, and an aqueous zinc-ion battery electrolyte; or a half-cell composed of commercially available 200µm thick zinc foil, a commercial current collector, and an aqueous zinc-ion battery electrolyte; or an aqueous zinc-ion full cell composed of commercially available 200µm thick zinc foil as the negative electrode, a vanadium-based layered material as the positive electrode, and an aqueous zinc-ion battery electrolyte; wherein the vanadium-based layered material is vanadium pentoxide.

[0008] Furthermore, the operating density of the battery is 0.1 mA / cm². 2 ~10mA / cm 2 .

[0009] Furthermore, the current collector is any one of copper foil, copper mesh, stainless steel mesh, and titanium foil.

[0010] The advantages and positive effects of this invention are as follows:

[0011] This invention designs an aqueous electrolyte containing bifunctional additives of ether and nitrile groups. The strong interaction between water and ether groups significantly reduces the amount of solvated water outside the solvation sheath, thereby reducing side reactions in the electrolyte. Furthermore, the nitrile groups adsorb onto the zinc anode surface, regulating the diffusion-induced growth of the (002) crystal plane during zinc ion deposition, effectively suppressing zinc dendrite growth and electrolyte-induced anode corrosion. This provides a novel design concept for aqueous electrolytes. Attached Figure Description

[0012] Appendix Figure 1 The graph shows the cycling performance of Zn||Zn symmetric cells in the electrolytes prepared in Examples 1, 5, 6 and Comparative Example 1.

[0013] Appendix Figure 2 The graph shows the cycling performance of Zn||Zn symmetric cells in the electrolytes prepared in Examples 1, 2, 3, 4 and Comparative Example 1.

[0014] Appendix Figure 3 Comparative scanning electron microscope (SEM) images of the zinc anode surface of a Zn||Zn symmetric cell after cycling in the electrolytes prepared in Example 1 and Comparative Example 1.

[0015] Appendix Figure 4 Coulombic efficiency diagrams for Zn||Cu asymmetric batteries in the electrolytes prepared in Example 1 and Comparative Example 1 during long-cycle operation.

[0016] Appendix Figure 5 The graph shows the long-cycle performance of the Zn||V2O5 full cell in the electrolytes prepared in Example 1 and Comparative Example 1. Detailed Implementation

[0017] In order to provide a detailed description of the invention's content, specific features, and effects, exemplary embodiments are described below in conjunction with the accompanying drawings. This detailed description should not be considered as a limitation of the invention, but rather as a more detailed description of certain aspects, characteristics, and embodiments of the invention.

[0018] The described embodiments are merely some, not all, of the embodiments of the present invention. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the protection scope of the present invention.

[0019] In the following examples, battery performance tests were conducted using the Xinwei Battery Testing System and the Chenhua Electrochemical Workstation. To measure the long cycle time of the symmetric battery, two treated zinc foils were used as two electrode plates. The electrolyte prepared in the following examples was used, and a glass fiber separator was used to assemble a 2025 coin cell. Testing was performed at a constant current density and constant time. To measure the coulombic efficiency of the battery, copper foil or zinc foil was used as the positive and negative electrodes, respectively. The electrolyte prepared in the following examples was used, and a glass fiber separator was used to assemble a 2025 coin cell. Testing was performed at a given current density and deposition time.

[0020] Example 1

[0021] To prepare a 1 mol / L zinc trifluoromethanesulfonate electrolyte containing 5 vol% MEON: Weigh 0.8317 g of zinc trifluoromethanesulfonate and dissolve it in 2.0 mL of deionized water; then add 0.1 mL of MEON additive; after dissolving, let it stand for 12 h for later use.

[0022] Example 2

[0023] To prepare a 1 mol / L zinc trifluoromethanesulfonate electrolyte containing 5 vol% MON: Weigh 0.8317 g of zinc trifluoromethanesulfonate and dissolve it in 2.0 mL of deionized water; then add 0.1 mL of MON additive; after dissolving, let it stand for 12 h.

[0024] Example 3

[0025] To prepare a 1 mol / L zinc trifluoromethanesulfonate electrolyte containing 5 vol% EON: Weigh 0.8317 g of zinc trifluoromethanesulfonate and dissolve it in 2.0 mL of deionized water; then add 0.1 mL of EON additive; after dissolving, let it stand for 12 h for later use.

[0026] Example 4

[0027] To prepare a 1 mol / L zinc trifluoromethanesulfonate electrolyte containing 5 vol% NEON: Weigh 0.8317 g of zinc trifluoromethanesulfonate and dissolve it in 2.0 mL of deionized water; then add 0.1 mL of NEON additive; after dissolving, let it stand for 12 h for later use.

[0028] Example 5

[0029] To prepare a 1 mol / L zinc trifluoromethanesulfonate electrolyte containing 10 vol% MEON: Weigh 0.8317 g of zinc trifluoromethanesulfonate and dissolve it in 2.0 mL of deionized water; then add 0.2 mL of MEON additive; after dissolving, let it stand for 12 h for later use.

[0030] Example 6

[0031] To prepare a 1 mol / L zinc trifluoromethanesulfonate electrolyte containing 1 vol% MEON: Weigh 0.8317 g of zinc trifluoromethanesulfonate and dissolve it in 2.0 mL of deionized water; then add 0.02 mL of MEON additive; after dissolving, let it stand for 12 h for later use.

[0032] Comparative Example 1

[0033] To prepare a 1 mol / L zinc trifluoromethanesulfonate electrolyte: Weigh 0.7921 g of zinc trifluoromethanesulfonate and dissolve it in 2.0 mL of deionized water; after dissolution, let it stand for 12 h for later use.

[0034] like Figure 1 As shown, at 1mA / cm 2 1mAh / cm 2 Under the test conditions, the symmetric cell using a 1 mol / L Zn(OTf)₂ electrolyte cycled stably for approximately 300 h, after which a sudden decrease in polarization voltage occurred, indicating a short circuit. With a 1 mol / L Zn(OTf)₂ + 5 vol% MEON electrolyte, the nucleation overpotential was significantly increased, which helped refine the nucleation grains and promote uniform zinc deposition. In this electrolyte system, the cycle life of the symmetric cell reached 2300 h, far exceeding the cycle life of the symmetric cell without additives (300 h), indicating that the use of additives significantly improved the long-term cycling stability of the zinc anode.

[0035] like Figure 2 As shown, at 5mA / cm 2 1mAh / cm 2 Under the test conditions, symmetric cells using 1 mol / L Zn(OTf)₂ electrolyte cycled stably for approximately 40 hours, after which a sudden decrease in polarization voltage indicated a short circuit. With additives of 5 vol% MEON, 5 vol% MON, 5 vol% EON, and 5 vol% NEON, the nucleation overpotential was significantly increased, which helped refine the nucleation grains and promote uniform zinc deposition. In these electrolyte systems, the cycle lives of the symmetric cells reached 350 h, 200 h, 230 h, and 280 h, respectively, far exceeding the cycle life of the symmetric cells without additives (40 h). This indicates that the use of these additives significantly improved the long-term cycling stability of the zinc anode.

[0036] like Figure 3 As shown, at 1mA / cm 2 1mAh / cm 2 After cycling for 300 hours under the test conditions, the zinc anode of the symmetrical battery using 1 mol / L Zn(OTf)2 electrolyte exhibited a noticeably uneven surface. Figure 3a) indicates irregular zinc deposition in the control electrolyte; when using a 1 mol / L Zn(OTf)2 + 5 vol% MEON electrolyte ( Figure 3 b) The zinc anode surface of the symmetrical battery is smoother, indicating that the 3-(ethoxymethoxy)propionitrile additive promotes the uniform deposition of zinc.

[0037] like Figure 4 As shown, at 2mA / cm 2 0.5mAh / cm 2 Under the test conditions, using 1 mol / L Zn(OTf)2 + 5 vol% MEON electrolyte for 600 cycles provided an ultra-stable coulombic efficiency of 98.60%. In contrast, using 1 mol / L Zn(OTf)2 electrolyte, after 30 cycles, due to the continuous occurrence of side reactions and significant zinc dendrite growth, the coulombic efficiency was extremely unstable and could not be stabilized, with an average coulombic efficiency of only 94.39%. This confirms the inhibitory effect of the 3-(ethoxymethoxy)propionitrile additive on undesirable zinc dendrites and by-products.

[0038] like Figure 5 As shown, the Zn||V₂O₅ battery using 5 vol% MEON electrolyte exhibits high cycle stability, with a capacity retention of 70.69% after 80 cycles. In contrast, the Zn||V₂O₅ battery using 1 mol / L Zn(OTf)₂ electrolyte shows significant fluctuations after 70 cycles, likely due to severe dendrite growth piercing the separator and leading to battery failure, demonstrating the practicality of the 3-(ethoxymethoxy)propionitrile additive.

[0039] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. An aqueous zinc-ion battery electrolyte comprising a bifunctional additive of ether and nitrile groups, characterized in that, The electrolyte comprises a bifunctional additive containing ether group and nitrile group, deionized water and zinc salt.

2. The aqueous zinc-ion battery electrolyte of claim 1, wherein, The bifunctional additive containing ether group and nitrile group has a structural formula of R-O-CH2CH2CN, wherein the R group is -CH3, -C2H5, -CH2CH2OCH3 or -CH2CH2OCH2CH2CN.

3. The aqueous zinc-ion battery electrolyte of claim 1, wherein, The content of the bifunctional additive containing ether group and nitrile group in the electrolyte ranges from 1% to 10% by volume, and the recommended optimal volume ratio is 5%.

4. The aqueous zinc-ion battery electrolyte of claim 1, wherein, The zinc salt is one or more of zinc sulfate, a hydrate of zinc sulfate, zinc chloride, a hydrate of zinc chloride, zinc acetate, a hydrate of zinc acetate, zinc trifluoromethane sulfonate and a hydrate of zinc trifluoromethane sulfonate.

5. The aqueous zinc-ion battery electrolyte of claim 1, wherein, The molar concentration of the zinc salt is 0.2-4 mol / L.

Images