Lithium-Sulfur Battery Electrolyte for Smooth Polysulfide Conversion
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Solution Overview
Problem
Lithium-sulfur secondary batteries exhibit low output power characteristics and reduced life due to the non-smooth conversion process of sulfur to lithium polysulfide and lithium sulfide, and side reactions with the anode, hindering their commercialization.
Innovation Solution
An electrolyte with optimized mixing energies and solubilities for dilithio peroctasulfide (Li2S8) and lithium sulfide (Li2S) is developed, using a non-aqueous solvent composition with specific ratios of furan-based and chain ether-based compounds, and controlled lithium salt and additive concentrations to facilitate smooth conversion processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional electrolytes are used in lithium-sulfur batteries, then the battery can operate, but the conversion process from sulfur to lithium polysulfide and lithium sulfide is non-smooth and slow, resulting in low output power characteristics
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing a chain ether-based compound (specifically 1,3-propanesultone) with controlled concentration (0.1-5.0 wt%). This parameter change modifies the electrolyte's interaction with lithium polysulfides, accelerating the conversion process from sulfur to lithium sulfide and improving output power characteristics without compromising battery operation
Solution Approach 2:
The patent creates a composite electrolyte system by combining conventional electrolyte components with 1,3-propanesultone additive. This composite approach integrates the beneficial properties of traditional electrolytes with the unique reactivity of the sultone compound, achieving both smooth conversion process and high output power characteristics
2Duration of action of moving object
If lithium polysulfide is formed during oxidation/reduction reactions, then the battery can charge/discharge, but side reactions occur between lithium polysulfide and the anode, reducing battery life characteristics
Solution Approach 1:
The 1,3-propanesultone additive acts as an intermediary substance that mediates the interaction between lithium polysulfide and the anode. It forms a protective interface layer that prevents direct harmful contact between lithium polysulfide and the anode material, thereby eliminating side reactions while maintaining normal charge/discharge operations
Solution Approach 2:
The patent converts the potentially harmful interaction between lithium polysulfide and the anode into a beneficial protective mechanism. The 1,3-propanesultone reacts with lithium polysulfide to form a stable interface layer that protects the anode, transforming what would be a harmful side reaction into a protective effect that extends battery life
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 enhances output power characteristics, particularly in the 70-80% state of charge range, and reduces side reactions, thereby improving the life characteristics of lithium-sulfur secondary batteries.
Implementation Method 1
a continuous reduction reaction of sulfur (e.g., Sa) contained in the cathode and a continuous oxidation reaction of metallic lithium contained in the anode occur within each electrode and the electrolyte
Implementation Method 2
the remaining lithium polysulfide (Li2Sn; n is 4, 6 or 8) may be in a liquid state dissolved in the electrolyte
Implementation Method 3
a continuous reduction reaction of sulfur (e.g., Sa) contained in the cathode and a continuous oxidation reaction of metallic lithium contained in the anode occur within each electrode and the electrolyte
Data Source
AI summary
The present disclosure relates to an electrolyte for a lithium-sulfur secondary battery that can improve output power characteristics of lithium-sulfur secondary batteries, and a lithium-sulfur secondary battery including the same. The electrolyte for the lithium-sulfur secondary battery includes a lithium salt, a non-aqueous solvent and an additive, wherein a first mixing energy (Gmix1) of the electrolyte and dilithio pertetrasulfide (Li2S8) and a second mixing energy (Gmix2) of the electrolyte and lithium sulfide (Li2S) are each within a certain range.