Solid-State Cathode Composite to Reduce Sulfide Electrolyte Heat Release
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Solution Overview
Problem
Sulfide solid-state electrolytes, such as argyrodite-type electrolytes, tend to react exothermically with common cathode materials like nickel, manganese, and cobalt at high temperatures, posing safety concerns due to the energy release proportional to the state-of-charge (SOC) of the cathode.
Innovation Solution
A cathode composite composition comprising a blend of single-crystal and polycrystalline cathode active materials combined with a solid sulfide electrolyte, such as Li7−yPS6−yXy, where 0≤y≤2 and X is a halogen, which reduces the exothermic reaction and enhances safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If sulfide solid-state electrolytes are used with common cathode materials, then ionic conductivity is improved, but exothermic reaction and safety deteriorate
Solution Approach 1:
An intermediate coating layer is applied to the cathode material surface to act as a barrier between the sulfide solid-state electrolyte and the cathode active material. This coating prevents direct contact and exothermic reaction while allowing ionic transport, thus resolving the contradiction between maintaining high ionic conductivity and preventing harmful exothermic reactions.
Solution Approach 2:
The cathode structure is designed as a composite system consisting of the cathode active material, the intermediate coating layer, and the sulfide solid-state electrolyte. This composite structure allows the system to benefit from the high ionic conductivity of sulfide electrolytes while the coating layer mitigates the exothermic reaction issue through material composition design.
2Stability of the object's composition
If single-crystal cathode active material is used, then structural stability is improved, but manufacturing complexity increases
Solution Approach 1:
The single-crystal cathode active material is pre-synthesized and prepared as ready-to-use components before assembly into the battery structure. This preliminary preparation of high-quality single crystals with controlled properties allows the final assembly process to be simplified, reducing overall manufacturing complexity while maintaining the structural stability benefits of single-crystal materials.
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 cathode composite composition achieves reduced heat flow and higher onset temperature, thereby improving safety and stability, with ionic conductivity ranging from 2 to 6 mS/cm and capacity greater than 130 mAh/g.
Implementation Method 1
sulfide solid-state electrolytes (SSE) (e.g., Argyrodite Li6PS5Cl) tend to react exothermally at high temperatures with commonly used cathode materials such as nickel, manganese, and cobalt (NMC)
Implementation Method 2
the cathode composite composition may have an ionic conductivity of at least 2 mS/cm
Data Source
AI summary
The present disclosure provides cathode compositions comprising solid-state electrolytes and cathode active materials. The cathode active materials may be single crystal, polycrystalline, or a combination thereof. The present disclosure also relates to cathodes made from the cathode composition.