Composite Cathode Coating for Stable High-Conductivity Solid-State Batteries
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Solution Overview
Problem
Existing lithium-ion batteries face issues of low thermal stability, ignitability, and leakage due to the use of organic liquid electrolytes, and oxide-based solid electrolyte shells in all-solid-state batteries reduce performance due to low ionic conductivity and resistive layers.
Innovation Solution
A composite positive electrode active material is developed with a coating layer containing a compound represented by Chemical Formula 1, combining lithium halides and lithium metal halides to enhance ionic conductivity and electrochemical stability, thereby suppressing side reactions with solid electrolytes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an oxide-based solid electrolyte shell is created on the positive electrode active material to prevent direct contact with sulfide-based solid electrolyte, then electrochemical stability is improved, but ionic conductivity decreases due to low conductivity of the oxide shell
Solution Approach 1:
The patent applies composite materials by creating a dual-layer coating structure consisting of an inner oxide-based solid electrolyte shell (providing electrochemical stability) and an outer fluoride-based solid electrolyte shell (providing high ionic conductivity). This composite structure resolves the contradiction by combining materials with complementary properties, where each layer performs its specialized function without compromising the other.
Solution Approach 2:
The fluoride-based solid electrolyte layer acts as an intermediary between the oxide-based shell and the sulfide-based bulk solid electrolyte. This intermediary layer maintains the protective function of the oxide shell while providing a high-conductivity pathway for ion transport, thus mediating between the conflicting requirements of stability and conductivity.
2Reliability
If a shell-shaped oxide-based solid electrolyte is created to suppress side reactions, then electrochemical stability is improved, but a resistive layer is formed causing performance decrease
Solution Approach 1:
The patent uses composite materials with a dual-layer structure where the inner oxide layer provides electrochemical stability and the outer fluoride layer provides high ionic conductivity. This composite approach eliminates the performance degradation caused by single-material shells by combining the advantages of both material types.
Solution Approach 2:
The patent applies local quality by assigning different functional properties to different regions of the coating structure. The inner layer is optimized for chemical stability (oxide), while the outer layer is optimized for ion transport (fluoride). Each layer has locally optimized properties suited to its specific function, resolving the contradiction between stability and performance.
Data Source
AI summary
An embodiment provides a composite positive electrode active material including: a positive electrode active material; and a coating layer on a surface of the positive electrode active material, the coating layer including a compound represented by Chemical Formula 1. Chemical formula 1 is as described in the specification.