Composite electrolyte for inhibiting zinc dendrite and application thereof

Abstract

The application discloses a composite electrolyte for inhibiting zinc dendrite and prolonging the cycle life of a battery and application thereof. The solvent of the composite electrolyte is a mixture of inorganic solvent and organic solvent, the volume ratio of the inorganic solvent to the organic solvent is 1 / 9-3 / 7, and the organic solvent is ethylene glycol methyl ether (MOE). The composite electrolyte provided by the application can destroy the original water solvation shell of zinc ions, adjust the deposition process of the zinc ions, and make the zinc ions tend to deposit on the (002) crystal surface. Thus, the occurrence of side reactions such as dendrite and hydrogen evolution is inhibited, and the service life of the aqueous zinc ion battery is prolonged, and the cycle stability is improved. In addition, the composite electrolyte provided by the application has low preparation cost, and provides a strategy for developing high-performance aqueous zinc ion batteries in the future.

Description

Technical Field

[0001] This invention relates to a battery electrolyte, specifically a composite electrolyte that inhibits zinc dendrite formation and improves battery cycle life. Background Technology

[0002] Currently, lithium-ion batteries occupy a huge market share in energy storage devices, and their widespread use has brought great convenience to human life. However, lithium-ion batteries also have shortcomings, such as high cost, environmental unfriendliness, and low safety, which limit their development.

[0003] Therefore, there is an urgent need to find a better energy storage device. Aqueous multivalent rechargeable ion batteries are considered a promising next-generation energy storage device to replace rechargeable lithium-ion batteries. In particular, aqueous zinc-ion batteries have received widespread attention from scientists in recent years because zinc is abundant on Earth and has a large theoretical specific capacity (mass specific capacity 820 mA hg). -1 Volumetric capacity 5855 mA h cm -3 Zinc anodes, with their low redox potential (relative to the hydrogen standard potential of -0.76V) and high safety, are aeroe materials with good overall performance in chemical power sources. However, the presence of side reactions, zinc dendrites, and low coulombic efficiency in zinc anodes reduce their reversibility, which greatly hinders the development of aqueous zinc-ion batteries. Therefore, improving the reversibility of zinc anodes is essential to advancing the development of aqueous zinc-ion batteries. Summary of the Invention

[0004] Purpose of the invention: The present invention aims to provide a composite electrolyte that can suppress zinc dendrites and improve battery cycle life, which is beneficial to improving the electrochemical performance of the battery; another purpose of the present invention is to provide an application of the composite electrolyte in an aqueous zinc-ion battery.

[0005] Technical Solution: This invention improves the environment of the zinc anode in the electrolyte by using a composite electrolyte, where the electrolyte is dissolved in two solvents. The composite electrolyte is prepared using ultrapure water and ethylene glycol monomethyl ether (MOE) as solvents. MOE has a higher Goodman donor number and higher electron cloud density for oxygen atoms than water, enhancing the strength of the H₂O covalent bond. Thus, the organic solvent MOE can disrupt the interactions between water and water, and between water and zinc ions, breaking down the original hydrosolubilization shell of zinc ions and altering the Zn₂O₃ covalent bond strength. 2+The solvation structure of the composite electrolyte inhibits hydrogen evolution. The deposition behavior of zinc ions in the composite electrolyte is adjusted compared to that of a simple electrolyte, transforming the chaotic and disordered deposition of zinc ions into deposition tending towards the (002) crystal plane. Simultaneously, the increased nucleation overpotential of zinc ions slows down the deposition time. These factors keep the zinc anode surface smooth during cycling, thereby improving the reversibility of the zinc anode. Furthermore, this composite electrolyte is inexpensive, which is significant for constructing high-performance and low-cost aqueous zinc-ion batteries.

[0006] The composite electrolyte for inhibiting zinc dendrites and improving battery cycle life described in this invention is a mixture of inorganic and organic solvents, with a volume ratio of 1 / 9 to 3 / 7, wherein the organic solvent is ethylene glycol methyl ether.

[0007] Furthermore, the composite electrolyte can regulate the formation of zinc (002) crystal planes and suppress hydrogen evolution side reactions.

[0008] Furthermore, the inorganic solvent is ultrapure water.

[0009] Furthermore, the resistance of the ultrapure water is 18-25 MΩ.

[0010] Furthermore, the electrolyte in the composite electrolyte is a zinc salt, such as zinc sulfate, zinc chloride, zinc nitrate, zinc acetate, etc.

[0011] Furthermore, the concentration of the composite electrolyte is 1 mol / L to 3 mol / L.

[0012] Furthermore, the amount of organic solvent in the aqueous zinc-ion battery composite electrolyte is 0–3 ml.

[0013] The composite electrolyte described in this invention can be applied to aqueous zinc-ion batteries. The aqueous zinc-ion battery includes a positive electrode, a negative electrode, a separator, and the aqueous zinc-ion battery electrolyte.

[0014] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The composite electrolyte can effectively suppress zinc dendrites and improve the cycle life of the battery, improve the reversibility of the zinc anode, and exhibit better electrochemical performance; (2) The preparation method of the composite electrolyte is simple and can be obtained by a simple dissolution method, and then applied to aqueous zinc-ion battery electrolytes. Attached Figure Description

[0015] Figure 1 Linear voltammetric curves of Zn-Ti half-cells under simple electrolyte and composite electrolyte conditions;

[0016] Figure 2 Zn-Cu batteries with simple electrolytes and composite electrolytes at 1 mA cm⁻¹-2 Area capacity 0.5mAh cm -2 A comparison chart of Coulomb efficiency;

[0017] Figure 3 Symmetric zinc batteries with simple electrolyte and composite electrolyte at a current density of 2 mA cm⁻¹ -2 Area specific capacity 1mAh cm -2 A comparison chart of long loops;

[0018] Figure 4 Scanned images of zinc foil after battery cycling with simple electrolyte and composite electrolyte. Detailed Implementation

[0019] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0020] In the following examples, battery performance tests were conducted using the Blue Battery Testing System and the Chenhua Electrochemical Workstation. To measure the long cycle time of the symmetrical battery, two polished zinc foils were used as the two electrode plates. Using the electrolyte prepared in the following examples and glass fiber as the separator, a 2032 coin cell was assembled and tested at a constant current density and constant time. To measure the coulombic efficiency of the battery, copper foil and zinc foil were used as the positive and negative electrodes, respectively. Using the electrolyte prepared in the following examples and glass fiber as the separator, a 2032 coin cell was assembled and tested at a given current density and deposition time.

[0021] Example 1

[0022] Prepare a 1 mol / L zinc sulfate composite electrolyte containing 10% ethylene glycol methyl ether:

[0023] Weigh 2.8756g of zinc sulfate into a beaker and add 9.0ml of ultrapure water to dissolve it. Then, measure 1.0ml of ethylene glycol methyl ether solvent into the beaker and stir while adding until the zinc sulfate particles are completely dissolved. After dissolving, continue stirring to mix evenly.

[0024] Example 2

[0025] Prepare a 1 mol / L zinc sulfate composite electrolyte containing 20% ​​ethylene glycol methyl ether:

[0026] Weigh 2.8756g of zinc sulfate into a beaker and add 8.0ml of ultrapure water to dissolve it. Then, measure 2.0ml of ethylene glycol methyl ether solvent into the beaker and stir while adding until the zinc sulfate particles are completely dissolved. After dissolving, continue stirring to mix evenly.

[0027] Example 3

[0028] Preparation of a zinc sulfate composite electrolyte containing 1 mol / L 30% ethylene glycol methyl ether:

[0029] Weigh 2.8756g of zinc sulfate into a beaker and add 7.0ml of ultrapure water to dissolve it. Then, measure 3.0ml of ethylene glycol methyl ether solvent into the beaker and stir while adding until the zinc sulfate particles are completely dissolved. After dissolving, continue stirring to mix evenly.

[0030] Comparative Example

[0031] Prepare a 1 mol / L simple zinc sulfate solution:

[0032] Weigh 2.8756g of zinc sulfate into a beaker and add 10.0ml of ultrapure water to dissolve it; after dissolving, continue stirring to mix it evenly.

[0033] Figure 1 Linear cyclic voltammetry curves of Zn-Ti half-cells using a simple electrolyte and a composite electrolyte are shown. The graphs clearly show that, compared to the simple electrolyte, the nucleation overpotential of zinc ions is significantly increased in the composite electrolyte, resulting in higher nucleation overpotentials for Zn ions. 2+ The electrolyte promotes uniform and refined deposition, while a low nucleation overpotential has the opposite effect, causing the deposits to rapidly grow into dendrites due to the "tip effect." This indicates that this composite electrolyte can inhibit the formation of zinc dendrites and improve the cycle life of the battery.

[0034] Figure 2 This graph compares the coulombic efficiency of Zn-Cu batteries using a simple electrolyte and a composite electrolyte. The graph shows that in the composite electrolyte, the Zn... 2+ The reversibility of deposition and stripping is enhanced, and the coulombic efficiency is greater than 99.5%. Considering the impact of different composite electrolytes on the battery cycle time and coulombic efficiency, the composite electrolyte containing 20% ​​ethylene glycol monomethyl ether solvent can maximize the performance improvement of the battery.

[0035] Figure 3 This is a long-cycle graph showing the results of using simple and composite electrolytes for symmetric zinc batteries. As can be seen from the graph, the cycle time of the zinc-zinc symmetric battery with the composite electrolyte is significantly increased compared to the battery using the simple electrolyte.

[0036] Figure 4 The images are scanning electron microscope images of symmetrical zinc batteries after long cycles using simple and composite electrolytes. It is clear that the zinc anode surface is smooth after 200 cycles with the composite electrolyte, while the zinc anode surface has larger dendrites after 200 cycles with the simple electrolyte.

[0037] In summary, the simple and composite electrolytes prepared in this invention, when applied to aqueous zinc-ion battery electrolytes, can protect the zinc anode, suppress dendrite formation and corrosion, extend the service life of aqueous zinc-ion batteries, and improve the cycle stability of the batteries.

Claims

1. A composite electrolyte for inhibiting zinc dendrite growth to enhance the cycle life of a battery, characterized by, The solvent of the composite electrolyte is a mixture of inorganic and organic solvents, with a volume ratio of inorganic to organic solvent of 1 / 9 to 3 / 7. The organic solvent is ethylene glycol methyl ether, and the inorganic solvent is ultrapure water with a resistance of 18-25 MΩ.

2. The composite electrolyte according to claim 1, characterized in that, The composite electrolyte can regulate the formation of zinc (002) crystal planes and suppress hydrogen evolution side reactions.

3. The composite electrolyte according to claim 1, wherein The electrolyte in the composite electrolyte is a zinc salt.

4. The composite electrolyte according to claim 1, wherein The concentration of the composite electrolyte is 1 mol / L to 3 mol / L.

5. The application of the composite electrolyte according to any one of claims 1-4 in an aqueous zinc-ion battery.

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