Solid-State Battery Cathode Layer for Longer Active Material Interfaces
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Solution Overview
Problem
High resistance in batteries due to a short contact interface length between cathode active material particles and solid electrolyte particles, even when the area ratio of the solid electrolyte is high in the cathode layer.
Innovation Solution
A cathode layer design with cathode active material particles having an average diameter of 2.5 μm to 4.5 μm and a normalized interface length value A of 1.15 μm−1 or more, achieved by controlling the average particle diameter, volume ratio of solid electrolyte, and coating ratio, to enhance the contact area between the cathode active material and solid electrolyte.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the area ratio of solid electrolyte in the cathode layer is increased, then the ionic conductivity is improved, but the contact interface length between cathode active material particles and solid electrolyte particles becomes short, resulting in high resistance
Solution Approach 1:
The patent changes the particle size parameter of cathode active material to a specific range (2.5-4.5 μm average diameter) to optimize the balance between solid electrolyte area ratio and contact interface length. This parameter adjustment enables both high ionic conductivity and sufficient contact interface for low resistance.
Solution Approach 2:
The patent creates a composite cathode layer structure combining cathode active material particles with solid electrolyte particles in a specific configuration. This composite structure ensures both adequate solid electrolyte area for ionic conductivity and sufficient contact interface length between materials to reduce resistance.
2Object-generated harmful factors
If the particle diameter of cathode active material is decreased to increase contact area, then the interface length is improved, but the filling ratio and density of the cathode layer decrease
Solution Approach 1:
The patent optimizes the particle diameter parameter to a specific range (2.5-4.5 μm) that balances contact interface length and filling ratio. This intermediate particle size provides sufficient contact area for low resistance while maintaining adequate filling ratio for high energy density.
Data Source
AI summary
A cathode layer comprising at least a cathode active material and a solid electrolyte, wherein the cathode active material is cathode active material particles, an average particle diameter of the cathode active material particles is 2.5 μm or more and 4.5 μm or less, and a normalized interface length value A (μm−1) obtained by dividing a length (μm) of an interface between the cathode active material and the solid electrolyte confirmed from a SEM image of a cross section of the cathode layer by an area (μm2) of the cathode active material in SEM image is 1.15 or more.