All-solid-state Lithium-sulfur Battery Cathode Composite
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Solution Overview
Problem
The cathode in all-solid-state lithium-sulfur batteries experiences volume changes during charging and discharging, leading to increased resistance and decreased discharge capacity due to the expansion and shrinkage of sulfur, which disrupts electron and ion conduction paths.
Innovation Solution
A cathode mixture comprising sulfur, carbon nanotubes, and an Li2S—P2S5 based solid electrolyte, forming a composite that maintains conductivity by suppressing path disruptions during volume changes, with the carbon nanotubes improving electron conductivity and the Li2S—P2S5 ensuring ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If sulfur is used as the active material in the cathode, then the battery can achieve high discharge capacity, but the volume of sulfur changes during charging and discharging, causing electron and ion conduction paths to be cut and resistance to increase
Solution Approach 1:
The patent uses carbon nanotubes to form a flexible three-dimensional network structure that envelops sulfur particles. This carbon nanotube shell acts as a flexible container that can accommodate the volume expansion and contraction of sulfur during charge-discharge cycles without breaking, thereby maintaining continuous electron and ion conduction paths despite the volume changes of sulfur
Solution Approach 2:
The patent creates a composite material system consisting of sulfur particles embedded in a carbon nanotube network with Li2S-P2S5 solid electrolyte. This composite structure combines the high capacity of sulfur with the structural stability and conductivity of carbon nanotubes, and the ion conductivity of the solid electrolyte, resolving the contradiction between capacity and conduction path stability
2Stability of the object's composition
If the cathode structure is rigid to maintain structural integrity, then the shape stability is improved, but the volume changes of sulfur during charging and discharging still cause path cutting and increased resistance
Solution Approach 1:
The patent transitions from a rigid cathode structure to a dynamic flexible structure using carbon nanotubes. The carbon nanotube network can dynamically adjust its configuration to accommodate sulfur's volume changes during charge-discharge cycles, maintaining both structural integrity and conduction path continuity through its flexible and reversible deformation capability
Solution Approach 2:
The carbon nanotube network forms a flexible shell structure around sulfur particles, replacing rigid binders. This flexible shell can elastically deform with sulfur's volume changes while maintaining the overall structural integrity of the cathode and ensuring continuous conduction paths
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 composite cathode effectively maintains electron and ion conduction paths, enhancing the discharge capacity of the battery by stabilizing the sulfur volume changes during charging and discharging.
Implementation Method 1
the sulfur, the carbon nanotube, and the P2S5 form a composite
Implementation Method 2
the sulfur and the CNT form a composite. Thus, the S-CNT-P2S5 composite makes it possible to suppress cutting of an electron conduction path
Implementation Method 3
an Li2S—P2S5 based solid electrolyte contained in the cathode makes it possible to secure a long ion conduction path
Implementation Method 4
an Li2S—P2S5 based solid electrolyte
Data Source
AI summary
Provided is a cathode for an all-solid-state lithium-sulfur battery that makes the discharge capacity improved. The cathode for an all-solid-state lithium-sulfur battery includes: a cathode mixture containing sulfur, a carbon nanotube, P2S5, and an Li2S—P2S5 based solid electrolyte, wherein the sulfur, the carbon nanotube, and the P2S5 form a composite, and the cathode mixture contains higher than 0 wt % and lower than 20 wt % of the carbon nanotube.