Lithium-Sulfur Battery 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 the difficulty in maintaining high sulfur loading and low porosity, leading to increased overvoltage and decreased performance.
Innovation Solution
A lithium-sulfur secondary battery design incorporating a nitrile-based solvent, fluorinated ether-based solvent, and disulfide-based solvent in specific volume ratios, along with a positive electrode having a porosity of 50 to 70% and sulfur loading of 2.5 to 5.0 mg/cm², to enhance electrolyte solution conductivity and reduce viscosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the content of electrolyte solution is decreased to achieve high energy density, then the energy density is improved, but the viscosity is increased rapidly and overvoltage increases causing battery deterioration
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte solution by introducing a specific cyclic carbonate solvent (1,3-propanesultone) and controlling its content within 5-50 wt%, which fundamentally alters the viscosity-voltage relationship of the system, allowing low electrolyte content without the harmful viscosity increase and overvoltage effects
Solution Approach 2:
The patent creates a composite electrolyte system by combining 1,3-propanesultone with other carbonate solvents (EC, PC, DMF, NMP) in specific ratios, where the cyclic structure of 1,3-propanesultone provides unique properties that prevent the harmful effects of high viscosity and overvoltage while maintaining high energy density
2Use of energy by moving object
If the content of electrolyte solution is decreased to achieve high energy density, then the energy density is improved, but the fluidity of active material decreases and side reactions increase
Solution Approach 1:
The patent changes the chemical parameters of the electrolyte by using 1,3-propanesultone with specific molecular structure and controlling its concentration (5-50 wt%), which maintains appropriate fluidity and chemical stability even at low electrolyte volumes, preventing side reactions and ensuring reliable battery operation
Solution Approach 2:
The 1,3-propanesultone acts as an intermediary substance that mediates between the electrode materials and the electrolyte solution, controlling the chemical environment to prevent harmful side reactions while maintaining stable battery operation under high energy density conditions
3Use of energy by moving object
If sulfur loading is increased to achieve high energy density, then the energy density is improved, but the porosity increases making it difficult to operate normally
Solution Approach 1:
The patent changes the electrode structural parameters by optimizing sulfur loading to 2.5-5.0 mg/cm² and controlling porosity within 50-70%, creating a balanced structure that achieves high energy density while maintaining operational stability and proper electrolyte distribution
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 battery achieves increased initial discharging capacity and average discharging voltage by optimizing solvent composition and electrode conditions, reducing overvoltage and improving overall performance.
Implementation Method 1
an ether-based solvent such as dioxolane and dimethoxy ethane, which are highly soluble for lithium polysulfide, is used as a solvent for the electrolyte solution
Implementation Method 2
The lithium cation produced by the oxidation reaction of lithium is transferred to the positive electrode through the electrolyte
Implementation Method 3
lithium which is a negative electrode active material is oxidized while releasing electron and thus ionizing
Implementation Method 4
the sulfur-based material which is a positive electrode active material is reduced while accepting the electron
Implementation Method 5
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
Disclosed is a lithium-sulfur secondary battery including a positive electrode, a negative electrode, a separator, and an electrolyte solution, wherein the electrolyte solution contains a lithium salt and a solvent, the solvent includes a nitrile-based solvent, a fluorinated ether-based solvent, and a disulfide-based solvent in a specific volume ratio, and thus for the positive electrode that satisfies the specific conditions of high loading and low porosity, the initial discharging capacity and average discharging voltage of the lithium-sulfur secondary battery containing the electrolyte solution may be improved.