Lithium-Sulfur Battery Electrolyte for Polysulfide Leaching Suppression
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Solution Overview
Problem
Lithium-sulfur batteries face issues with lithium polysulfide leaching, leading to capacity degradation and reduced cycle life due to the high solubility of ether-based solvents, which results in incomplete utilization of theoretical discharging capacity and energy density.
Innovation Solution
An electrolyte comprising a benzene-based compound and 1,3-dioxolane as non-aqueous organic solvents, with a specific volume ratio and lithium salt, is used to suppress lithium polysulfide leaching, enhancing the battery's capacity and cycle life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ether-based solvents are used in the electrolyte to improve lithium polysulfide solubility and reactivity, then the electrochemical reaction efficiency is improved, but lithium polysulfide leaching and shuttle phenomenon occur leading to capacity degradation and reduced cycle life
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte solvent from conventional ether-based solvents to a specific mixture of cyclic carbonate (15-30 vol%) and chain carbonate (70-85 vol%). This parameter change in solvent type and composition fundamentally alters the solubility characteristics of lithium polysulfide, reducing leaching while maintaining adequate reaction efficiency.
Solution Approach 2:
The patent employs a composite electrolyte system combining two different carbonate solvents (cyclic and chain types) in specific proportions. This composite approach leverages the complementary properties of each solvent: cyclic carbonate provides moderate polysulfide solubility while chain carbonate provides high ionic conductivity and low viscosity, achieving a balance between reaction efficiency and cycle stability.
2Reliability
If the electrolyte content is minimized to reduce lithium polysulfide leaching, then capacity degradation is reduced, but the viscosity increases during charging/discharging causing overvoltage
Solution Approach 1:
The patent optimizes the electrolyte composition parameters by selecting specific carbonate solvents with appropriate viscosity and ionic conductivity characteristics. The chain carbonate component (70-85 vol%) particularly contributes to low viscosity and high ionic conductivity, allowing adequate electrolyte content to be maintained without excessive viscosity increase, thus preventing overvoltage while still reducing polysulfide leaching compared to ether-based systems.
3Quantity of substance
If sulfur content in the positive electrode is increased to achieve higher theoretical capacity, then energy density is improved, but lithium polysulfide dissolution and shuttle phenomenon are exacerbated
Solution Approach 1:
The patent changes the electrolyte solvent parameters from ether-based to carbonate-based (cyclic + chain mixture), fundamentally altering the solubility environment for lithium polysulfide. This parameter change in solvent chemistry reduces the dissolution tendency of polysulfides, allowing higher sulfur content (60-90 wt% in the positive electrode) to be utilized without exacerbating the shuttle phenomenon.
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 proposed electrolyte effectively inhibits lithium polysulfide leaching, maximizing positive electrode capacity and ensuring stable cycle life, thereby improving the overall performance and operational stability of lithium-sulfur batteries.
Implementation Method 1
An electrolyte comprising a benzene-based compound and 1,3-dioxolane as non-aqueous organic solvents, with a specific volume ratio and lithium salt, is used to suppress lithium polysulfide leaching
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 more specifically, the electrolyte comprises a first solvent comprising a benzene-based compound and a second solvent comprising 1,3-dioxolane as a non-aqueous organic solvent, thereby suppressing the leaching of lithium polysulfide and thus enabling high capacity and long cycle life of the lithium-sulfur battery.