Lithium-Sulfur Battery Separator Sulfur Support
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Solution Overview
Problem
Lithium-sulfur batteries have poor lifetime characteristics and low volumetric energy density due to the low reversibility and stability of lithium metal and the migration of polysulfides, which reduces the capacity and efficiency of the battery.
Innovation Solution
Incorporating a separator that supports elemental sulfur or lithium sulfide and an interlayer containing elemental sulfur or lithium sulfide particles in the electrolyte region, allowing for increased energy density and capacity without the need for additional conductive materials or thickening the positive electrode mixture layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sulfur is supported in porous carbon to increase contact area, then electric conductivity is improved, but manufacturing cost increases and active material content is limited
Solution Approach 1:
The patent extracts sulfur from the porous carbon support structure and places it directly in the electrolyte solution. This eliminates the need for expensive porous carbon materials while maintaining electrochemical functionality, as sulfur particles can directly receive electrons from the electrolyte without requiring carbon support for conductivity enhancement.
Solution Approach 2:
The electrolyte solution acts as an intermediary medium that enables electron transfer to sulfur particles suspended in it. Instead of relying on carbon as a conductive bridge, the electrolyte itself facilitates the electrochemical reaction by serving as the conductive medium that directly contacts sulfur particles.
2Quantity of substance
If sulfur content in positive electrode is increased to improve energy density, then volumetric energy density should increase, but current density decreases
Solution Approach 1:
The patent applies a fluid-based approach by suspending sulfur particles in the electrolyte solution rather than embedding them in a solid electrode matrix. This allows the sulfur to be distributed throughout the electrolyte volume, maintaining high surface area contact with the conductive electrolyte medium and enabling high current density even with increased sulfur content.
3Quantity of substance
If lithium metal is used as negative electrode for high theoretical capacity, then energy density is improved, but reversibility and stability decrease leading to poor lifetime
Solution Approach 1:
The patent converts the harmful effect of polysulfide migration to the lithium negative electrode into a beneficial feature. By allowing polysulfides to migrate and react with lithium, the system forms lithium polysulfide complexes that remain soluble in the electrolyte, preventing permanent capacity loss and improving cycle life while maintaining high capacity.
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 approach enhances the energy density and capacity of lithium-sulfur batteries by increasing the amount of sulfur or lithium sulfide, while minimizing the proportion of conductive materials and preventing polysulfide migration, thus improving the battery's lifetime and performance.
Implementation Method 1
solid sulfur particles which are electrically separated from a positive electrode can also participate in the reaction, and thus it was confirmed that electric charges are transferred at a solid-liquid interface
Data Source
AI summary
The present invention provides: i) a lithium-sulfur battery in which solid sulfur is introduced into an electrolytic region between a positive electrode and a negative electrode; ii) a lithium-sulfur battery comprising a middle layer containing elemental sulfur (S8) or lithium sulfide (Li2S) in an electrolytic region between a positive electrode and a negative electrode; and iii) a lithium-sulfur battery having a separator supporting sulfur particles or lithium sulfide particles between a positive electrode and a negative electrode.