Carbon-based fiber sheet and lithium-sulfur battery including same
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Solution Overview
Problem
Lithium-sulfur batteries face capacity and lifecycle decline due to lithium polysulfide elution and diffusion from the positive electrode, leading to reduced charging capacity and energy storage efficiency.
Innovation Solution
A carbon-based fiber sheet doped with a high concentration of nitrogen is interposed between the positive electrode and the separator in the lithium-sulfur battery, effectively adsorbing lithium polysulfide and suppressing its diffusion, thereby enhancing battery capacity and lifecycle properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium-sulfur battery uses sulfur-based material as positive electrode active material, then theoretical energy density reaches 2600 Wh/kg, but lithium polysulfide dissolves in electrolyte and diffuses away from positive electrode, reducing charging capacity
Solution Approach 1:
A separator coated with nitrogen-doped carbon material is introduced as an intermediary between the positive electrode and negative electrode. This separator acts as a mediator that selectively adsorbs lithium polysulfide through nitrogen-containing functional groups while maintaining ion transport, preventing polysulfide diffusion to the negative electrode and reducing the shuttle effect
Solution Approach 2:
The separator is designed with a porous structure to maintain high ion conductivity while providing sufficient surface area for lithium polysulfide adsorption. The porous morphology allows efficient lithium ion transport while the nitrogen-doped carbon surface captures polysulfide species, resolving the contradiction between energy density and polysulfide loss
2Reliability
If lithium polysulfide diffuses into negative electrode and reacts with lithium, then corrosion of lithium metal negative electrode occurs, but battery lifecycle and capacity retention deteriorate
Solution Approach 1:
The nitrogen-doped carbon separator serves as a protective intermediary that intercepts lithium polysulfide before it reaches the negative electrode. By adsorbing polysulfide species on its surface, the separator prevents direct contact between polysulfide and lithium metal, eliminating corrosion while maintaining long-term battery operation
Solution Approach 2:
The separator converts the harmful effect of lithium polysulfide diffusion into a beneficial adsorption process. The nitrogen-containing groups on the separator surface specifically bind to lithium polysulfide, transforming the problematic dissolved polysulfide into a stabilized adsorbed state that prevents further harmful reactions
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 high-nitrogen-doped carbon-based fiber sheet significantly improves the lithium-sulfur battery's capacity retention and cycling stability by preventing polysulfide shuttle reactions, maintaining high discharge efficiency even after multiple cycles.
Implementation Method 1
the carbon-based fiber sheet doped with a high concentration of nitrogen is interposed between the positive electrode and the separator in the lithium-sulfur battery, effectively adsorbing lithium polysulfide and suppressing its diffusion
Data Source
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AI summary
The present invention relates to a carbon-based fiber sheet and a lithium-sulfur battery including the same. The carbon-based fiber sheet for the lithium-sulfur battery according to the present invention is doped with a high concentration of nitrogen and thus plays a role of preventing diffusion by adsorbing lithium polysulfide eluted from a positive electrode during charging and discharging, thereby suppressing a shuttle reaction and thus improving capacity and lifecycle properties of the lithium-sulfur battery.