Lithium Sulfur Battery Electrolyte Polysulfide Control
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Solution Overview
Problem
Lithium sulfur batteries face issues with sulfur elution into the electrolyte, leading to poor cycle stability and reduced capacity, especially when using high surface density positive electrodes.
Innovation Solution
An electrolytic solution with a polysulfide concentration of 10 mM to 400 mM, containing a liquid complex or salt that is insoluble in polysulfides and a solvent that is soluble, helps prevent sulfur elution, maintaining high capacity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a nonaqueous electrolytic solution containing lithium ion is used in a lithium sulfur battery, then sulfur reacts with lithium ion during charge-discharge to be gradually eluted into the electrolytic solution as polysulfide, but this causes redox shuttle and poor cycle stability
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolytic solution by introducing specific additives (cyclic sulfate esters and chain sulfate esters) to modify the solubility characteristics of polysulfides, thereby controlling the elution behavior and improving cycle stability while maintaining capacity
Solution Approach 2:
The patent uses sulfate ester compounds as intermediary substances that mediate between the sulfur positive electrode and lithium ion electrolyte, preventing direct harmful interactions while facilitating beneficial electrochemical reactions
2Reliability
If an electrolytic solution in which glyme and an alkali metal salt form a complex is used to suppress elution of polysulfide, then polysulfide elution is suppressed, but the reaction between sulfur and lithium ion is reduced, reducing capacity and making cycle characteristics unstable
Solution Approach 1:
The patent modifies the electrolyte composition by adding specific sulfate esters to the glyme-alkali metal salt complex system, adjusting the polysulfide solubility parameters to achieve both suppression of elution and maintenance of reaction activity
Solution Approach 2:
The patent creates a composite electrolytic solution system combining glyme, alkali metal salt, cyclic sulfate ester, and chain sulfate ester, where each component contributes specific properties that collectively resolve the contradiction between suppressing elution and maintaining capacity
3Quantity of substance
If a positive electrode having a high surface density is used, then electricity storage performance is improved, but the reaction between sulfur and lithium ion is significantly reduced, reducing capacity and making cycle characteristics unstable
Solution Approach 1:
The patent adjusts the electrolyte composition parameters to optimize the interface between high surface density positive electrode and electrolyte, ensuring sufficient reaction kinetics while maintaining high capacity and cycle stability
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 solution achieves high capacity and cycle stability in lithium sulfur batteries, even with high surface density positive electrodes, by controlling the polysulfide concentration and solubility in the electrolyte.
Implementation Method 1
the electrolytic solution contains: at least one of a liquid complex and a liquid salt in which a polysulfide is insoluble or almost insoluble; and a solvent in which a polysulfide is soluble
Implementation Method 2
the electrolytic solution has a Li2S8 saturation sulfur concentration of 10 mM or more and 400 mM or less
Implementation Method 3
sulfur contained in a positive electrode reacts with a lithium ion in an electrolytic solution during charge-discharge
Implementation Method 4
a negative electrode containing a material for occluding and releasing a lithium ion
Data Source
AI summary
A battery includes a positive electrode containing sulfur, a negative electrode containing a material for occluding and releasing a lithium ion, and an electrolytic solution. The electrolytic solution contains at least one of a liquid complex and a liquid salt in which a polysulfide is insoluble or almost insoluble, and a solvent in which a polysulfide is soluble. The electrolytic solution has a Li2S8 saturation sulfur concentration of 10 mM or more and 400 mM or less.