Phosphorus-Coated Cathode Particles for Low-Resistance Solid-State Batteries
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Solution Overview
Problem
Existing methods for producing positive electrode active materials in all-solid-state batteries fail to sufficiently reduce resistance at the interface between the positive electrode and the sulfide solid electrolyte, limiting the battery's performance.
Innovation Solution
A composite particle is formed by coating a positive electrode active material with a phosphorus-containing film having a glass-transition temperature of 300°C or less, which is produced through a spray drying method, and the composite particle is then rolled with a sulfide solid electrolyte at 170°C or higher to enhance adhesion and reduce resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating film is formed on the positive electrode active material particle surface, then the reaction between the positive electrode active material and the solid electrolyte is suppressed, but the resistance is not sufficiently reduced
Solution Approach 1:
The patent applies parameter changes by controlling the glass-transition temperature (Tg) of the phosphorus compound coating film to be 300°C or less. This specific temperature parameter enables the coating film to exhibit flexible molecular motion at battery operating temperatures, which simultaneously suppresses unwanted reactions and reduces resistance. The Tg parameter is the critical control variable that resolves the contradiction between reaction suppression and resistance reduction.
Solution Approach 2:
The patent uses a composite material approach by forming a coating film composed of specific phosphorus compounds (such as Li3PO4, Li2SiO3-P2O5 glass, or their composites) on the positive electrode active material particle surface. This composite structure combines the reaction-suppressing properties of phosphorus-based materials with the low-Tg characteristics that enable resistance reduction, effectively resolving the technical contradiction.
2Stability of the object's composition
If the coating film has high stability to suppress reactions, then the adhesion between the positive electrode active material and the solid electrolyte is improved, but the flexibility and ion conductivity are reduced
Solution Approach 1:
The patent resolves this contradiction by changing the thermal parameter (glass-transition temperature) of the coating film material. By selecting phosphorus compounds with Tg ≤ 300°C, the coating film maintains compositional stability for reaction suppression while possessing sufficient molecular flexibility at operating temperatures to enable good adhesion and low resistance. The Tg parameter serves as the key control that balances stability and flexibility.
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 composite particle with a flexible phosphorus-containing coating film effectively reduces resistance and improves ion conductivity, enhancing the performance of the all-solid-state battery.
Implementation Method 1
A glass-transition temperature (Tg) of the coating film is 300° C. or less
Implementation Method 2
Produce the composite particle by drying the mixture by a spray drying method
Implementation Method 3
Rolling the positive electrode active material layer and the positive electrode current collector at 170° C. or higher
Data Source
AI summary
A composite particle includes a positive electrode active material particle and a coating film. In a method for producing the composite particle, the coating film covers at least a part of a surface of the positive electrode active material particle, the coating film contains a phosphorus compound, and a glass-transition temperature of the coating film is 300° C. or less.