Phosphate-Coated Cathode Particles for Solid-State Battery Heat Suppression
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Solution Overview
Problem
The thermal stability of positive electrode active material layers in all-solid-state batteries is insufficient, leading to increased heat generation and reduced battery capacity due to direct contact between the solid electrolyte and the positive electrode active material, which can result in electrode deterioration.
Innovation Solution
A composite particle is developed comprising a lithium-containing composite oxide with a layered rock salt structure coated with a phosphate compound, where the coating film covers at least a part of the positive electrode active material particle, with specific mass fractions of phosphorus and lithium, and a coverage rate of 80% or more, to suppress heat generation and enhance thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating film is formed on the positive electrode active material particle surface, then resistance is reduced due to inhibition of direct contact between solid electrolyte and positive electrode active material, but thermal stability remains insufficient and heat generation is large
Solution Approach 1:
The patent applies composite materials by forming a coating film containing phosphate compounds (such as lithium phosphate) on the surface of positive electrode active material particles. This composite structure combines the benefits of the base material with the protective properties of the phosphate coating, achieving both low resistance and high thermal stability simultaneously
Solution Approach 2:
The patent changes the chemical composition parameters of the coating film by controlling the phosphate compound content and its distribution. By adjusting the concentration and type of phosphate compounds in the coating, the film achieves optimal balance between electrical resistance and thermal stability properties
2Temperature
If phosphate compound is added to suppress heat generation, then thermal stability is improved, but the coating film composition and manufacturing complexity increase
Solution Approach 1:
The patent applies local quality by concentrating phosphate compounds specifically at the surface region of the positive electrode active material particles. This localized approach provides thermal stability where it is most needed (at the interface with solid electrolyte) without requiring phosphate compounds throughout the entire particle structure, thus reducing overall complexity
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 effectively reduces heat generation from the positive electrode, improving thermal stability and maintaining battery capacity by inhibiting direct contact between the solid electrolyte and the positive electrode active material, thereby preventing electrode deterioration.
Implementation Method 1
it is considered that, for example, oxygen released by a positive electrode in an overcharged state at a high temperature reacts with phosphoric acid, and the sulfide gas can be suppressed from being generated
Implementation Method 2
resistance can be reduced due to inhibition of direct contact between a solid electrolyte and the positive electrode active material particle by the coating film
Data Source
AI summary
A composite particle includes a positive electrode active material particle and a coating film. The positive electrode active material particle contains a lithium-containing composite oxide having a layered rock salt structure, and the coating film covers at least a part of a surface of the positive electrode active material particle. The coating film contains a phosphate compound, and satisfies a relationship of the following formula (1): XP/T ≥ 0.04 (1). In the above formula (1), XP indicates a mass fraction of phosphorus contained in the composite particle measured by inductively coupled plasma atomic emission spectroscopy, and T indicates a film thickness of the coating film measured by a scanning electron microscope.