Lithium-Sulfur Cell Electrolyte Composition for High Sulfur Loading
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Solution Overview
Problem
Existing lithium-sulfur secondary batteries face challenges in achieving high energy density due to limitations in the reactivity of sulfur and the characteristics of the electrolyte solution, which affect the porosity and loading of the positive electrode.
Innovation Solution
The lithium-sulfur secondary battery is designed with a positive electrode having a specific SC factor value, achieved by optimizing the porosity and sulfur loading, and an electrolyte solution comprising a solvent with a DV2 factor value of 1.75 or less and a fluorinated ether-based solvent, which improves the energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the content of the electrolyte solution is decreased to construct a high energy density battery, then the energy density is improved, but the concentration of lithium polysulfide in the electrolyte solution is increased, causing decreased fluidity and increased side reactions
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte solution by introducing specific additives (LiNO3 at 0.5-5 wt%, sulfur compounds at 0.1-5 wt%, and carboxylic acid derivatives at 0.1-5 wt%) to modify the behavior of lithium polysulfide in the electrolyte, enabling high energy density while maintaining stability
Solution Approach 2:
The patent uses specific chemical compounds as intermediaries that mediate between the lithium polysulfide and the electrolyte solution, reducing harmful side reactions and improving fluidity while maintaining high concentration conditions
2Quantity of substance
If sulfur is used as a positive electrode active material to achieve high theoretical energy density, then the energy storage capacity is improved, but the reactivity with electrons and lithium ions is poor due to low electrical conductivity
Solution Approach 1:
The patent uses conductive additives and surface modifiers as intermediaries to facilitate electron and ion transfer between sulfur and the electrolyte, improving reactivity while maintaining high sulfur content for energy density
Solution Approach 2:
The patent modifies the physical and chemical parameters of sulfur through compound formation and surface treatment to enhance its electrical conductivity and reactivity with lithium ions
3Quantity of substance
If a low porosity positive electrode is used to increase loading, then the energy density is improved, but the reactivity and lifetime characteristics are affected due to limited electrolyte access
Solution Approach 1:
The patent optimizes the porosity parameter to a specific range (30-60%) that balances loading capacity with electrolyte penetration, achieving high energy density while maintaining reactivity and lifetime characteristics
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 configuration enables the lithium-sulfur secondary battery to achieve a high energy density, exceeding that of conventional batteries, while maintaining performance without degradation.
Implementation Method 1
the oxidation reaction of lithium is a process by which lithium metal releases electron and is converted to lithium cation form
Implementation Method 2
the reduction reaction of sulfur is a process by which the S—S bond accepts two electrons and is converted to a sulfur anion form
Implementation Method 3
The lithium cation produced by the oxidation reaction of lithium is transferred to the positive electrode through the electrolyte and is combined with the sulfur anion generated by the reduction reaction of sulfur to form a salt
Data Source
AI summary
A lithium-sulfur secondary battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte solution are provided. The positive electrode has an SC factor value of 0.45 or more. The electrolyte solution includes a solvent and a lithium salt, and the solvent includes a first solvent having a DV2 factor value of 1.7 or less, and a second solvent which is a fluorinated ether-based solvent.