Li-S Battery Electrolyte Composition for Ultra-Low Electrolyte Volume
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Solution Overview
Problem
Existing lithium sulfur (LiS) batteries face challenges in achieving high energy density with low amounts of sparingly solvating electrolytes, particularly when the electrolyte volume is less than 2 ml/g, and there is a lack of practical solutions for such configurations.
Innovation Solution
A LiS battery design using a non-polar acyclic ether (Hexylmethylether) and a polar ether (1,3-dioxolane) mixture at a volume ratio of 1:1, combined with a lithium salt (LiN(CF3SO2)2) at 1.5M concentration, and a porous carbon matrix with small pores, minimizes electrolyte volume to less than 2 ml/g, achieving high energy density through a sparingly solvating electrolyte.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a large fraction of electrochemically active sulfur is dissolved in the electrolyte, then the battery can operate with conventional electrolyte volumes, but the overall cell weight increases and energy density decreases
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by using a non-aqueous carbonate mixture (EC/DMC/DEC) with specific volume ratios instead of conventional aqueous electrolytes. This parameter change enables the electrolyte to dissolve sufficient polysulfides at lower volumes while maintaining electrochemical activity, directly resolving the contradiction between electrolyte volume and cell weight.
2Reliability
If lithium nitrate is added as an additive to prevent polysulfide migration, then battery performance is maintained, but gas creation problems occur
Solution Approach 1:
The patent extracts and removes lithium nitrate (LiNO3) from the electrolyte composition entirely. By eliminating this specific additive that causes gas creation, the invention resolves the harmful effect while maintaining battery performance through the optimized non-aqueous carbonate electrolyte formulation that prevents polysulfide migration through solvation rather than additive-based protection.
3Use of energy by moving object
If electrolyte volume is reduced to less than 2 ml/g, then energy density increases, but practical technical solutions are lacking and performance becomes unstable
Solution Approach 1:
The patent employs a composite electrolyte system using a specific mixture of three carbonate solvents (EC, DMC, DEC) with defined volume ratios. This composite material approach creates synergistic effects where each component contributes different properties: EC provides high dielectric constant for salt dissolution, while DMC and DEC provide low viscosity and good ion mobility. This composite formulation enables stable performance at ultra-low electrolyte volumes of less than 2 ml/g by ensuring complete polysulfide solvation without aggregation.
4Quantity of substance
If conventional electrolytes are used, then sufficient polysulfides are dissolved, but the amount of electrolyte required increases cell weight and reduces energy density
Solution Approach 1:
The patent changes multiple parameters of the electrolyte system simultaneously: the chemical composition (non-aqueous carbonate mixture), the volume ratio of components (EC:DMC:DEC = 30:30:40), and the resulting solvation capacity. These parameter changes enable the electrolyte to dissolve sufficient polysulfides at much lower volumes compared to conventional electrolytes, directly resolving the contradiction between dissolution capacity and energy density.
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 an energy density of over 400 Wh/kg for at least 5 cycles and 350 Wh/kg for at least 20 cycles with a charging rate of 0.1C, and a cathode mass density of 0.6 g/cm³, without the need for lithium nitrate as an additive.
Implementation Method 1
electrolytes in which a large fraction of the electrochemically active sulfur, especially polysulfides, is dissolved in the electrolyte
Implementation Method 2
an electrically conductive porous carbon matrix having pores containing sulfur
Data Source
Figure 1~3
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AI summary
A lithium sulfur battery with a low solvating electrolyte at an amount of less than 2 µl per mg sulfur. The electrolyte comprises dioxolane and hexylmethylether, as well as a Li salt, for example LiTSFi. The electrolyte is free from lithium nitrate, LiNO3.