CN-121983687-A - Electrolyte leveling agent and preparation method and application thereof

Abstract

The invention belongs to the field of electrochemical power supplies, and particularly relates to an electrolyte leveling agent, a preparation method and application thereof. The invention has both electrostatic shielding effect and anion anchoring function. The molecules can be adsorbed on the surface of an alkali metal electrode, metal ions are guided to be uniformly deposited through electrostatic shielding to inhibit dendrites, interface anions are enriched through electrostatic interaction, and a firm SEI layer rich in metal fluoride is promoted to be formed. This synergistic strategy of leveling and anchoring is expected to optimize both deposition kinetics and interfacial chemistry, thereby significantly improving the long cycle performance and safety of alkali metal cells, especially under severe temperature conditions. The leveling agent molecule has low cost, is commercially available, is simple to synthesize, is easy to produce and apply in large scale, and provides a new potential direction for developing the next-generation lithium metal battery electrolyte with high performance, wide temperature range and high safety.

Inventors

• YE HUAN
• LI YINGXIAN
• CAO FEIFEI

Assignees

• 华中农业大学

Dates

Publication Date

20260505

Application Date

20251231

Claims (10)

1. 1. An electrolyte leveling agent, characterized in that the leveling agent at least comprises an organic small molecule containing N, S, O electron-rich groups.
2. 2. The electrolyte leveling agent according to claim 1, wherein the leveling agent molecule is at least one selected from the group consisting of quaternary ammonium compounds having a structure represented by formula (I), cis-decahydronaphthalene, thiourea, toluidine blue, and 1, 4-butynediol. R 1 R 2 R 3 R 4 N + X - (I) In formula (I), R 1 、R 2 、R 3 and R 4 are each independently selected from alkyl of C 1 -C 6 , and X - is selected from halide.
3. 3. The electrolyte leveling agent according to claim 1 or 2, wherein the leveling agent molecule is present in the electrolyte in an amount of 0.05 to 10% by mass.
4. 4. An electrolyte for an alkali metal cell, said electrolyte comprising an alkali metal salt, an organic solvent, and a leveler molecule according to any one of claims 1-3.
5. 5. The electrolyte for an alkali metal cell as claimed in claim 4, wherein the alkali metal salt comprises at least one of a lithium salt, a sodium salt, or a potassium salt, and the concentration of the alkali metal salt is 0.5 mol/L to 2 mol/L.
6. 6. The electrolyte for an alkali metal cell as claimed in claim 4, wherein the organic solvent is at least one selected from the group consisting of ethylene carbonate, diethyl carbonate, dimethyl carbonate, methylethyl carbonate, 1, 3-dioxolane, ethylene glycol dimethyl ether, and tetrahydrofuran.
7. 7. The electrolyte for an alkali metal cell as claimed in claim 4, further comprising a film-forming additive in the electrolyte, wherein the film-forming additive is present in an amount of 1 to 15% by volume of the electrolyte.
8. 8. The method for producing an electrolytic solution according to any one of claims 4 to 7, comprising the steps of: Stirring and dissolving the leveling agent molecules in a basic electrolyte under the protection of inert atmosphere to obtain the electrolyte, wherein the basic electrolyte is a mixed solution of 1M of LiPF 6 and 1:1 in volume ratio of EC to DEC and contains 10. 10 vol% of fluoroethylene carbonate, the mass ratio of the leveling agent molecules to the basic electrolyte is 0.02:1.98, the stirring temperature is room temperature to 50 ℃, the stirring time is 12 to 36 hours, the inert atmosphere is argon atmosphere, and the water and oxygen content in a glove box is lower than 0.01 and ppm.
9. 9. An alkali metal cell comprising a negative electrode, a separator, a positive electrode, and the electrolyte of any one of claims 4-7.
10. 10. Use of a leveler molecule according to any one of claims 1 to 3 or an electrolyte according to any one of claims 4 to 7 in an alkali metal cell.

Description

Electrolyte leveling agent and preparation method and application thereof Technical Field The invention belongs to the field of electrochemical power supplies, and particularly relates to an electrolyte leveling agent, a preparation method and application thereof. Background Rechargeable alkali metal batteries (e.g., lithium, sodium, potassium metal batteries) are considered ideal choices for next generation high energy density energy storage systems due to their extremely high theoretical specific capacity and low electrochemical potential of the negative electrode material. The theoretical specific capacity of the lithium metal negative electrode is up to 3830 and mAh g –1, the potential is as low as-3.04V (vs. SHE), and the sodium and potassium metal negative electrodes have the potential advantages of rich resources and lower cost. However, all alkali metal anodes present a fundamental challenge in practical applications in that metal deposition tends to exhibit dendritic or mossy-like irregular growth during repeated electroplating/stripping cycles. At the same time, the dendrite structure has large specific surface area and unstable solid electrolyte interface film, which can aggravate electrolyte decomposition, and cause irreversible loss of active metal and electrolyte, so that the coulomb efficiency of the battery is low and the cycle life is rapidly reduced. To inhibit dendrite growth, researchers have explored a variety of strategies, including mainly (1) constructing artificial SEI or three-dimensional conductive carriers to physically block or guide metal deposition, (2) developing solid electrolytes to provide mechanical barriers, and (3) optimizing liquid electrolyte compositions, particularly introducing functional additives. Among them, electrolyte additive modification is considered as one of the most practical approaches due to its ease of implementation and good compatibility with existing battery production processes. Conventional additives, such as fluoroethylene carbonate, lithium nitrate, etc., passivate the electrode surface, primarily by participating in the formation of the SEI. However, such additives are continuously consumed during cycling, resulting in dynamic evolution of the SEI and reduced interfacial stability over time. Conventional SEI film-forming additives regulate metal ion deposition behavior by forming a protective layer at the negative electrode interface, but they are continuously consumed in cycles, resulting in unstable interfaces, and difficult to achieve long-term cycles. Recently, researchers are inspired by the interface regulation concept in the metal electroplating industry, and the concept of an electroplating additive is introduced into an alkali metal battery system, so that a new idea is provided for regulating the metal ion deposition morphology. Plating levelers are a class of additives that preferentially adsorb onto microscopic raised areas of plated articles, and by inhibiting the metal deposition rates in these "peak areas" while promoting the continued deposition in "valley areas", a leveled, dense coating is achieved. However, the currently reported electroplating additives or related strategies still have the problems of high synthesis cost, complex preparation process, poor performance in a wide temperature range and the like. Therefore, developing an electrolyte additive that is low in cost, easy to synthesize, and capable of effectively stabilizing an alkali metal negative electrode in a wide temperature range is critical to promoting practical application of lithium metal batteries. Disclosure of Invention The invention aims to overcome the defects of short cycle life, poor safety, poor wide-temperature-range performance and the like caused by dendrite growth and unstable interface in the existing alkali metal battery (such as a lithium, sodium, potassium and other metal batteries), and provides an electrolyte additive based on a synergistic mechanism of an electroplating leveler and anion anchoring, an electrolyte containing the electrolyte additive and application of the electrolyte additive in the alkali metal battery. The additive can effectively inhibit the growth of alkali metal dendrites, construct a stable inorganic enrichment solid electrolyte interface layer, and remarkably improve the cycle stability, coulombic efficiency and wide-temperature-range working performance of an alkali metal battery. The invention adopts the following technical scheme to realize the purpose: an electrolyte leveling agent comprising at least one small organic molecule containing N, S, O electron-rich groups. The leveling agent molecule is at least one of quaternary ammonium salt compound with a structure shown in a formula (I), cis-decahydronaphthalene, thiourea, toluidine blue and 1, 4-butynediol. R1R2R3R4N+X- (I) In formula (I), R 1、R2、R3 and R 4 are each independently selected from alkyl of C 1-C6, and X - is selected from halide. Preferably, the l