Lithium-Sulfur Battery Electrolyte Composition for Polysulfide Suppression
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Solution Overview
Problem
Lithium-sulfur batteries face challenges with polysulfide elution from the positive electrode, increased material resistance of the electrolyte, and instability during low-temperature operation, which affects battery performance and safety.
Innovation Solution
The development of an electrolyte for lithium-sulfur batteries comprising a lithium salt and a nonaqueous solvent mixture, specifically including glycol ether, cyclic ether, and acyclic ether, where the acyclic ether is limited to 15 vol % or less and the ratio of glycol ether to acyclic ether is 5 or more, to suppress polysulfide elution and improve electrolyte resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ether-based solvents are used as electrolyte solvent to improve sulfur reactivity, then polysulfide elution increases and material resistance increases, but if traditional electrolytes are used, then low temperature operation stability deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing a specific cyclic carboxylate compound (γ-butyrolactone) and controlling the ratio of ether-based solvents to non-ether-based solvents. This parameter change reduces polysulfide elution while maintaining low temperature operation stability, resolving the contradiction between reliability and harmful factors.
Solution Approach 2:
The patent creates a composite electrolyte system combining ether-based solvents (for sulfur reactivity), non-ether-based solvents (γ-butyrolactone for polysulfide suppression), and lithium salts. This composite approach leverages the advantages of each component to simultaneously achieve good reactivity, reduced polysulfide elution, and stable low temperature operation.
2Quantity of substance
If acyclic ether is increased in the electrolyte composition, then polysulfide dissolution improves, but electrolyte resistance increases and low temperature performance deteriorates
Solution Approach 1:
The patent optimizes the concentration parameter of acyclic ether to 15 vol% or less and controls the ratio of glycol ether to acyclic ether at 5 or more. These parameter changes prevent excessive polysulfide dissolution that would increase electrolyte resistance, while still maintaining adequate dissolution through the balanced composition.
Solution Approach 2:
The patent creates local quality differentiation in the electrolyte by having different solvent components serve different functions: glycol ether and cyclic ether provide moderate polysulfide dissolution, while γ-butyrolactone specifically suppresses excessive dissolution and reduces resistance. This localized functional assignment resolves the contradiction between dissolution quantity and resistance.
3Object-generated harmful factors
If glycol ether ratio is increased to suppress polysulfide elution, then electrolyte viscosity increases, but if viscosity increases, then low temperature operation becomes difficult
Solution Approach 1:
The patent optimizes the glycol ether content to 65-80 vol% (not excessive) and controls the glycol ether to acyclic ether ratio at 5 or more. These parameter changes achieve effective polysulfide elution suppression while preventing viscosity from becoming too high, thereby maintaining low temperature operability.
Solution Approach 2:
The patent introduces γ-butyrolactone as an intermediary substance that mediates between glycol ether and polysulfide. It enhances the polysulfide suppression effect of glycol ether while having a minimal impact on viscosity compared to increasing glycol ether content directly. This intermediary approach resolves the contradiction between elution suppression and temperature performance.
4Power
If ether-based solvents are used to improve sulfur reactivity through liquid phase reaction, then battery life is affected by electrolyte amount, but gas production occurs at low temperature due to low boiling point
Solution Approach 1:
The patent changes the boiling point parameter of the electrolyte by incorporating γ-butyrolactone (boiling point 204°C) which has a significantly higher boiling point than traditional ether-based solvents. This parameter change suppresses gas production at low temperature while maintaining sulfur reactivity through the preserved ether-based solvent components.
Solution Approach 2:
The patent creates a composite electrolyte where ether-based solvents (DME, Dioxolane) provide sulfur reactivity through liquid phase reaction, while γ-butyrolactone provides thermal stability and prevents gas production. This composite material approach simultaneously achieves high sulfur reactivity and eliminates the harmful gas production effect.
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
This electrolyte composition effectively suppresses polysulfide elution, reduces overvoltage, enhances electrolyte resistance, and improves the battery's output characteristics, enabling stable low-temperature operation and extended cycle life.
Implementation Method 1
The lithium cation produced by the oxidation reaction of lithium migrates to the positive electrode via an electrolyte
Implementation Method 2
the reactivity of sulfur and the battery life are affected by the amount of the electrolyte... use, as the solvent of the electrolyte, ether-based solvents in which lithium polysulfide dissolves well
Data Source
AI summary
The present disclosure relates to an electrolyte for a lithium-sulfur battery and a lithium-sulfur battery comprising the same, and the electrolyte for the lithium-sulfur battery comprises a lithium salt and a nonaqueous solvent, wherein the nonaqueous solvent comprises glycol ether, cyclic ether and acyclic ether represented by the following chemical formula 1, the acyclic ether is included in an amount of 15 vol % or less based on the total volume of the nonaqueous solvent, and a ratio of a total volume of the glycol ether to a total volume of the acyclic ether is 5 or more:R1—O—R2 [Chemical formula 1]where R1 is an unsubstituted or substituted C1 to C3 alkyl group, and R2 is an unsubstituted or substituted C3 to C20 alkyl group.