Lithium-Sulfur Battery Electrolyte With Cyclic Anhydride SEI Protection

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Solution Overview

Problem

The existing lithium-sulfur secondary batteries face issues with electrolyte solution decomposition, leading to deteriorated lifetime characteristics due to the use of ether-based solvents, which increase viscosity and cause overvoltage, especially when minimizing electrolyte content for high energy density applications.

Innovation Solution

Incorporating a cyclic anhydride compound as an additive in the electrolyte solution containing a lithium salt and non-aqueous solvent, with specific lithium salts and solvent ratios, to form a stable Solid Electrolyte Interphase (SEI) film, preventing decomposition and improving lifetime characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If ether-based solvent is used to dissolve lithium polysulfide and improve reactivity, then the reactivity of sulfur is improved, but the lifetime characteristics of the battery are deteriorated due to decomposition and viscosity increase

Engineering Contradiction:

Improvereactivity of sulfurVSAvoidlifetime characteristics of battery

Core Design Contradiction:

SpeedVSDuration of action of stationary object

Solution Approach 1:

A cyclic carboxylate compound is introduced as an intermediary substance in the electrolyte solution. This additive acts as a mediator that modifies the interaction between the ether-based solvent and lithium polysulfide, preventing harmful decomposition while maintaining the beneficial high reactivity. The cyclic carboxylate compound specifically coordinates with lithium ions to form stable complexes, thereby suppressing the decomposition of ether-based solvent and extending battery lifetime without sacrificing sulfur reactivity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention changes the chemical composition parameters of the electrolyte solution by adding a cyclic carboxylate compound (0.1-10 wt% based on total electrolyte weight). This parameter change transforms the electrolyte system from a simple ether-based solution to a complexed system where the cyclic carboxylate modifies the solvation structure around lithium ions, thereby changing the decomposition behavior and viscosity characteristics while preserving high reactivity.

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If the content of electrolyte solution is minimized to achieve high energy density, then the energy density is improved, but the viscosity increases rapidly and overvoltage occurs

Engineering Contradiction:

Improveenergy density of batteryVSAvoidviscosity of electrolyte solution

Core Design Contradiction:

Use of energy by moving objectVSForce

Solution Approach 1:

The cyclic carboxylate compound serves as a mediator that maintains optimal viscosity even at minimized electrolyte content. By forming stable complexes with lithium ions, it prevents excessive viscosity increase that would otherwise occur when electrolyte content is reduced for high energy density applications.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Quantity of substance

If ether-based solvent is used to dissolve lithium polysulfide, then the solubility is improved, but decomposition of electrolyte solution occurs leading to harmful by-products

Engineering Contradiction:

Improvesolubility of lithium polysulfideVSAvoiddecomposition of electrolyte solution

Core Design Contradiction:

Quantity of substanceVSObject-generated harmful factors

Solution Approach 1:

The invention converts the potentially harmful decomposition reaction of ether-based solvent into a beneficial process. The cyclic carboxylate compound preferentially reacts with lithium ions to form stable complexes, which prevents the ether-based solvent from decomposing. This transforms what would be a harmful decomposition pathway into a controlled coordination chemistry system that enhances stability while maintaining solubility.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The electrolyte solution effectively prevents decomposition and enhances the lifetime of lithium-sulfur secondary batteries by forming a stable SEI film, thereby improving the battery's performance and longevity.

Implementation Method 1

Methodology Applied

Scientific EffectSolid Electrolyte Interphase (SEI) film formation:

Implementation Method 2

The lithium cation produced by the oxidation reaction of lithium is transferred to the positive electrode through the electrolyte and is combined with the sulfur anion generated by the reduction reaction of sulfur to form a salt.

Methodology Applied

Scientific EffectIon transfer: Electrolyte

Data Source

PatentEP4142009B1Electrolyte solution for lithium-sulfur secondary battery, and lithium-sulfur secondary battery comprising same

Publication Date: 2025.07.30 LG ENERGY SOLUTION LTD

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AI summary

The present invention relates to an electrolyte solution for a lithium-sulfur secondary battery comprising a lithium salt, a non-aqueous solvent and a cyclic anhydride compound, and a lithium-sulfur secondary battery containing the same.