Dual-Layer Cathode Coating for Low-Resistance Solid-State Batteries
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Solution Overview
Problem
Batteries face challenges in reducing interfacial resistance, which affects their performance, particularly due to oxidative decomposition of sulfide solid electrolytes during charging and variations in battery characteristics despite using the same coating material.
Innovation Solution
A coated active material with a dual-layer coating system, where the first coating layer contains a halide solid electrolyte and the second layer is a lithium-containing oxide, applied to the positive electrode active material, controlling the specific surface area change between 62.8% reduction and 3.79% increase to inhibit interfacial resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-layer coating is applied to the positive electrode active material, then the coating process is simple, but the battery resistance remains high due to oxidative decomposition of sulfide solid electrolytes
Solution Approach 1:
The coating is divided into two distinct layers: a first coating layer containing a sulfide solid electrolyte in contact with the positive electrode active material, and a second coating layer containing an oxide solid electrolyte located outside the first coating layer. This segmentation allows each layer to perform its specific function - the sulfide layer provides good interfacial contact and ionic conductivity, while the oxide layer prevents oxidative decomposition, thereby reducing battery resistance without excessive complexity
Solution Approach 2:
The invention uses a composite coating structure combining two different solid electrolyte materials (sulfide and oxide) with complementary properties. The sulfide solid electrolyte provides high ionic conductivity and good interfacial contact, while the oxide solid electrolyte provides oxidation resistance. This composite approach resolves the contradiction by achieving low resistance through material property complementarity rather than simple structural complexity
2Manufacturing precision
If the specific surface area changes significantly after coating, then the coating coverage may be insufficient, but reducing the specific surface area too much decreases the active material surface area available for reactions
Solution Approach 1:
The invention specifies that the percentage of change in specific surface area from the positive electrode active material coated with the second coating layer to the coated active material is greater than or equal to −62.8% and less than or equal to +3.79%. This parameter control ensures that the coating is applied uniformly without excessive thickness that would overly reduce the surface area, maintaining both coating precision and sufficient reactive surface area
Data Source
AI summary
A coated active material includes a positive electrode active material and a coating layer coating at least a portion of a surface of the positive electrode active material. The coating layer includes a first coating layer and a second coating layer. The first coating layer is located outside of the second coating layer. A percentage of change in specific surface area from a specific surface area of the positive electrode active material coated with the second coating layer to a specific surface area of the coated active material is greater than or equal to −62.8% and less than or equal to +3.79%.