CN-122000459-A - Thioether compound electrolyte of functional diluent

CN122000459ACN 122000459 ACN122000459 ACN 122000459ACN-122000459-A

Abstract

An electrolyte taking thioether compounds as functional diluents relates to the technical field of lithium ion batteries. The electrolyte comprises lithium salt, a solvent for dissolving the lithium salt, a diluent and an additive, wherein the diluent is a thioether compound. By introducing thioether compounds as functional diluents, a local high-concentration electrolyte system is constructed, and the ionic conductivity and the lithium ion migration number of the electrolyte are effectively improved. The diluent has special affinity with the SPAN positive electrode, can inhibit polysulfide dissolution from physical and chemical layers, optimize potential distribution and ion desolvation process at the interface of the positive electrode, and participate in forming a CEI interface rich in LiF which is favorable for lithium ion transmission. According to the invention, three functions of optimizing a solvation structure, anchoring active substances and constructing a stable interface are simultaneously realized by introducing a thioether functional diluent, and the rate capability and the cycle stability of the Li-SPAN battery are obviously improved.

Inventors

CHEN JUN
ZHU CHUNYAN
ZHAO JIAHUA
LI YUAN
YAN HAN
Ni Youxuan
LU YONG
LI HAIXIA

Assignees

南开大学

Dates

Publication Date: 20260508
Application Date: 20260121

Claims (8)

1. An electrolyte taking a thioether compound as a functional diluent comprises lithium salt, a solvent for dissolving the lithium salt, a diluent and an additive, and is characterized in that the diluent is the thioether compound; the thioether compound comprises at least one of dimethyl sulfide, dipropyl disulfide or dipropyl trisulfide; The lithium salt comprises at least one of lithium bis (trifluoromethylsulfonyl) imide, lithium bis (fluorosulfonyl) imide, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium dioxalate borate, lithium difluorooxalate borate or lithium perchlorate; The solvent for dissolving the lithium salt comprises at least one of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, tetrahydrofuran, ethylene carbonate, propylene carbonate, dimethyl carbonate or methyl ethyl carbonate; The additive comprises at least one of triethyl phosphate, fluoroethylene carbonate or vinylene carbonate; wherein the concentration of the lithium salt is 0.5-3.0 mol/L; the volume ratio of the solvent for dissolving the lithium salt to the thioether compound is 9:1-5:5; The additive is used in an amount of 1-10% by mass of the electrolyte.
2. The electrolyte using thioether compound as functional diluent according to claim 1, wherein the lithium salt is lithium bis (fluorosulfonyl) imide.
3. The electrolyte using thioether compound as functional diluent according to claim 1, wherein the solvent for dissolving the lithium salt is ethylene glycol diethyl ether.
4. The electrolyte using a thioether compound as a functional diluent according to claim 1, wherein the thioether compound is dipropyl sulfide.
5. The electrolyte using thioether compound as functional diluent according to claim 1, wherein the additive is triethyl phosphate.
6. Use of the electrolyte of any one of claims 1-5 with thioether compounds as functional diluents in lithium metal batteries.
7. A lithium metal battery comprising the electrolyte of any one of claims 1-5.
8. The lithium metal battery of claim 7, wherein the positive electrode of the lithium metal battery is a vulcanized polyacrylonitrile and the negative electrode is lithium metal.

Description

Thioether compound electrolyte of functional diluent Technical Field The invention belongs to the field of lithium ion batteries, and particularly relates to an electrolyte taking thioether compounds as functional diluents. Background Under the background of global energy transformation and rapid development of new energy automobile industry, development of secondary batteries with high energy density, long cycle life and rapid charging capability has become a core challenge in the energy storage field. Traditional lithium ion batteries are limited by the theoretical capacity of the positive electrode material and key metal resources, and development faces bottlenecks. The Sulfidized Polyacrylonitrile (SPAN) anode can effectively inhibit polysulfide shuttling by virtue of a unique solid-solid conversion mechanism, and is considered to be one of ideal candidates for constructing high-energy lithium metal batteries. However, the intrinsic electron/ion conductivity of SPAN materials is low, resulting in serious shortages of fast charge performance. At high current densities, retarded ion transport kinetics and unstable electrode/electrolyte interfaces can cause severe polarization and capacity fade, which have become critical obstacles limiting their practical use. The electrolyte is a core for regulating and controlling ion transmission and interface stability in the battery. Therefore, it is important to design a high performance fast charge electrolyte system that matches it. The Local High Concentration Electrolyte (LHCE) strategy improves macro-processability of the high concentration electrolyte while maintaining its excellent interfacial properties by introducing a "diluent". Wherein the choice of diluent directly determines the overall performance of LHCE. At present, fluoroether and the like are widely adopted as diluents in researches, and the high oxidation stability and flame retardance of fluoroether and the like are mainly utilized. However, the design concept of such conventional diluents focuses on "chemical inertness" and physical tuning, and for SPAN-like electrodes with specific surface chemistry, there is a lack of active interface tuning functionality. Furthermore, highly fluorinated components often result in a significant increase in electrolyte density (> 1.4 g mL-1), which is detrimental to the overall energy density of the cell. More importantly, the operating voltage window of the SPAN system is relatively mild and the extreme oxidation resistance requirements for the co-solvent are not necessary. Therefore, the limitation of the traditional 'inert' cosolvent is broken through, and the development of the functional cosolvent capable of actively participating in and optimizing the SPAN interface chemical process is of great significance for releasing the quick charge potential of the Li|SPAN battery. Disclosure of Invention The invention aims to provide an electrolyte taking a thioether compound as a functional diluent, which aims at solving the problems of slow lithium ion transmission dynamics and poor electrode/electrolyte interface stability in the existing Li-SPAN battery system. In order to achieve the aim of the invention, the invention adopts the following technical scheme: in a first aspect, the invention provides an electrolyte with a thioether compound as a functional diluent, which comprises a lithium salt, a solvent for dissolving the lithium salt, a diluent and an additive. The diluent is thioether compound. The thioether compound comprises at least one of dimethyl sulfide, dipropyl disulfide or dipropyl trisulfide. The lithium salt comprises at least one of lithium bis (trifluoromethylsulfonyl) imide, lithium bis (fluorosulfonyl) imide, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium dioxalate borate, lithium difluorooxalate borate or lithium perchlorate. The solvent for dissolving the lithium salt comprises at least one of 1, 2-diethoxyethane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, tetrahydrofuran, ethylene carbonate, propylene carbonate, dimethyl carbonate or methyl ethyl carbonate. The additive comprises at least one of triethyl phosphate, fluoroethylene carbonate or vinylene carbonate. Wherein the concentration of the lithium salt is 0.5-3.0 mol/L; the volume ratio of the solvent for dissolving the lithium salt to the thioether compound is 9:1-5:5; The additive is used in an amount of 1-10% by mass of the electrolyte. Preferably, the lithium salt is lithium bis-fluorosulfonyl imide. Preferably, the solvent for dissolving the lithium salt is ethylene glycol diethyl ether (DEE). Preferably, the thioether compound is Dipropyl Sulfide (DS). Preferably, the additive is triethyl phosphate (TEP). In a second aspect, the invention provides a lithium metal battery, wherein the electrolyte is the electrolyte using a thioether compound as a functional diluent, the negative electrode is lithium metal, and the positive electrode is vulcani