Oxide-Coated Carbon Fiber Cathodes for Stable Solid-State Batteries
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Solution Overview
Problem
All-solid-state batteries face challenges due to the poor thermodynamic stability of sulfide solid electrolytes, leading to degradation at interfaces, which results in reduced Li+ mobility and rapid capacity fade in cathode composite layers, especially with high cathode active material percentages and low solid electrolyte percentages.
Innovation Solution
A cathode layer comprising cathode active material particles, sulfide solid electrolyte, and carbon fibers coated with an oxide material, such as Li3B11O18, which reduces sulfide solid electrolyte degradation by providing electrical insulation and maintaining electron conduction pathways, thereby enhancing cycle stability and initial capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If carbon fiber is added to improve electrical conduction and initial capacity, then electron conduction pathways increase and CAM utilization improves, but SE degradation accelerates and capacity fade increases
Solution Approach 1:
An oxide coating layer is introduced as an intermediary between the carbon fiber and sulfide solid electrolyte. This coating acts as a mediator that prevents direct harmful interactions while maintaining beneficial electrical conduction, thereby resolving the contradiction between initial capacity improvement and cycle stability
Solution Approach 2:
The invention creates a composite structure by coating carbon fiber with oxide materials. This composite material combines the electrical conductivity of carbon fiber with the stability of oxide coatings, enabling both high initial capacity and sustained cycle performance
2Productivity
If the percentage of cathode active material is increased to improve capacity, then initial capacity increases, but SE degradation increases due to reduced SE content and increased interface reactions
Solution Approach 1:
The oxide coating on carbon fiber serves as a protective intermediary that reduces harmful interfacial reactions between CAM and SE. This allows higher CAM content to be used without proportionally increasing SE degradation, as the coating prevents direct contact and reactive interactions
Solution Approach 2:
The oxide coating provides localized protection at the carbon fiber/SE interface where degradation occurs most severely. By treating only the critical interfacial regions with protective coating, the system can accommodate higher CAM percentages while maintaining SE stability
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 solution significantly reduces sulfide solid electrolyte degradation, resulting in improved cycle-life stability and high initial specific capacities near 100% cathode active material utilization, maintaining battery performance over multiple cycles.
Implementation Method 1
carbon fibers coated with an oxide material, such as Li3B11O18, which reduces sulfide solid electrolyte degradation by providing electrical insulation and maintaining electron conduction pathways
Data Source
AI summary
Disclosed is a cathode composite layer for an all solid-state battery, comprising particles of a cathode active material (CAM), a solid electrolyte (SE), an electrically conductive carbon fiber coated with an oxide material. In one embodiment, the present disclosure provides an all solid-state battery comprising the cathode composite layer, wherein the battery has an increased capacity and cycle stability due to the reduced SE degradation.