Composite Cathode Coating for Solid-State Battery Oxidation Control
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Solution Overview
Problem
Batteries using solid electrolytes face safety issues due to oxidation of the electrolyte by oxygen from the positive electrode active material, leading to temperature increase and potential malfunction or casing damage.
Innovation Solution
A coated active material is developed with a first solid electrolyte layer containing Li, M, and X (where M is a metalloid or metal element and X is F, Cl, Br, or I) and a second base material layer, with a specific surface area ratio of the coated material to the positive electrode active material of less than or equal to 42%, enhancing oxidation resistance and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solid electrolyte coating is applied to the positive electrode active material, then oxidation resistance is improved, but the specific surface area ratio becomes too high leading to excessive coating thickness and reduced battery performance
Solution Approach 1:
The patent optimizes the specific surface area ratio parameter to be 42% or less, and controls the coating thickness to be 1 nm or more and 10 nm or less. By precisely controlling these parameters, the coating provides sufficient oxidation protection while preventing excessive thickness that would hinder ion transport and reduce battery performance.
Solution Approach 2:
The patent uses a composite coating structure consisting of a first solid electrolyte layer containing Li, M, and X elements, and a second base material layer. This composite structure allows the first layer to provide oxidation resistance while the second layer provides structural support, achieving both protection and performance requirements.
2Reliability
If the coating layer thickness is increased to improve oxidation resistance, then safety is improved, but charge-discharge efficiency and power characteristics deteriorate
Solution Approach 1:
The patent establishes an optimal coating thickness range of 1 nm to 10 nm, which is thick enough to provide oxidation protection and improve safety, but thin enough to allow efficient lithium ion transport. This parameter optimization ensures both safety enhancement and maintenance of charge-discharge efficiency.
Solution Approach 2:
The coating is applied selectively to the surface of the positive electrode active material particles, providing oxidation protection only where needed at the particle surface, while the interior particles remain unaffected. This localized approach maintains bulk material performance and ion transport pathways.
3Temperature
If a thicker coating layer is used to prevent oxidation, then thermal stability is improved, but the battery may experience excessive heat generation due to increased resistance
Solution Approach 1:
The patent controls the coating thickness to be 1 nm or more and 10 nm or less, which provides sufficient thermal stability and oxidation protection while minimizing the increase in electrical resistance. This thin coating reduces energy loss as heat compared to thicker coatings.
Solution Approach 2:
The composite structure with a thin first solid electrolyte layer and second base material layer provides thermal stability without the excessive resistance associated with thick single-layer coatings. The second layer helps maintain low resistance while the first layer provides oxidation and thermal protection.
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 coated active material improves battery safety by inhibiting oxidation and heat generation, while maintaining charge-discharge efficiency and power characteristics, and can further enhance safety with a ratio of less than or equal to 40% without excessive coating thickness.
Implementation Method 1
improving the safety of a battery by inhibiting oxidation and heat generation
Implementation Method 2
inhibiting oxidation and heat generation
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, which contains a first solid electrolyte, and a second coating layer, which contains a base material. The first coating layer is located outside of the second coating layer. The first solid electrolyte contains Li, M, and X, where M is at least one selected from the group consisting of metalloid elements and metal elements other than Li, and X is at least one selected from the group consisting of F, Cl, Br, and I. A ratio of a specific surface area of the coated active material to a specific surface area of the positive electrode active material coated with the second coating layer is less than or equal to 42%.