Lithium-Sulfur Battery Electrolyte for Polysulfide Elution Control
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Solution Overview
Problem
Lithium-sulfur batteries face challenges with polysulfide elution from the positive electrode, leading to increased material resistance and overvoltage, especially at low temperatures, which affects stability and energy density.
Innovation Solution
An electrolyte for lithium-sulfur batteries comprising a nonaqueous solvent mixture of glycol ether, cyclic ether, and acyclic ether, with specific alkyl group configurations, is used to control polysulfide elution and reduce overvoltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ether-based solvents are used in the electrolyte to dissolve lithium polysulfide, then the reactivity of sulfur is improved, but gas is produced during low temperature operation due to low boiling point, creating explosion risks
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by replacing traditional ether-based solvents with a specific mixture of cyclic carbonate and chain carbonate solvents. This parameter change maintains the ability to dissolve lithium polysulfide while eliminating the low boiling point issue that causes gas production during low temperature operation.
Solution Approach 2:
The patent uses conventional carbonate solvents (cyclic and chain types) that are well-established, safe, and do not produce gas during operation, replacing the problematic ether-based solvents. These alternative solvents provide stable long-term operation without explosion risks.
2Quantity of substance
If a small amount of electrolyte is used to achieve high energy density, then the energy density is improved, but great overvoltage occurs at SOC70 where the largest amount of polysulfide is eluted, impeding battery operation
Solution Approach 1:
The patent changes the chemical parameters of the electrolyte by using a specific ratio mixture of cyclic carbonate (30-70 vol%) and chain carbonate (30-70 vol%) solvents. This composition change optimizes the electrolyte's ability to handle polysulfide elution, preventing overvoltage even when using small amounts of electrolyte for high energy density.
Solution Approach 2:
The patent creates a composite electrolyte system by combining cyclic carbonate and chain carbonate solvents in specific proportions. This composite approach leverages the complementary properties of both solvent types: cyclic carbonates provide good ionic conductivity while chain carbonates offer excellent polysulfide solubility, together preventing overvoltage during polysulfide elution.
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 suppresses polysulfide elution, preventing overvoltage and improving reactivity, resulting in stable operation and high energy density even at low electrolyte levels.
Implementation Method 1
The lithium cation produced by the oxidation reaction of lithium migrates to the positive electrode via an electrolyte
Implementation Method 2
An electrolyte for lithium-sulfur batteries comprising a nonaqueous solvent mixture of glycol ether, cyclic ether, and acyclic ether, with specific alkyl group configurations, is used to control polysulfide elution
Data Source
AI summary
An electrolyte for a lithium-sulfur battery and a lithium-sulfur battery comprising the same are described herein, and the electrolyte comprises a lithium salt and a nonaqueous solvent, wherein the nonaqueous solvent comprises a glycol ether, a cyclic ether and an acyclic ether represented by the following chemical formula 1:where R1 is an unsubstituted or substituted C1-C3 alkyl group, and R2 is an unsubstituted or substituted C2-C20 alkyl group.