Coated Disordered Rocksalt Cathodes for High-Voltage Cycle Stability
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Solution Overview
Problem
Disordered rocksalt materials used in lithium ion batteries exhibit poor capacity retention due to instability and side reactions during high voltage cycling, leading to reduced cycle life and cell resistance.
Innovation Solution
A coating layer comprising oxides, phosphates, or fluorides is applied to the surface of disordered rocksalt materials to stabilize the cathode, reducing side reactions and improving cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If disordered rocksalt materials are used as cathode material, then high specific energy density is achieved, but poor capacity retention occurs during cycling
Solution Approach 1:
The patent applies composite materials by combining disordered rocksalt cathode material with a coating layer comprising lithium phosphate and lithium phosphide. This composite structure maintains the high energy density of the rocksalt material while the coating layer provides stability during cycling, resolving the contradiction between high specific energy density and poor capacity retention.
Solution Approach 2:
The coating layer acts as an intermediary between the disordered rocksalt material and the electrolyte. It mediates the interaction by preventing direct contact and harmful side reactions, thereby improving capacity retention while preserving the high energy density characteristics of the rocksalt material.
2Use of energy by moving object
If disordered rocksalt materials are cycled at high voltage, then high energy density is achieved, but side reactions with residual lithium salts increase cell resistance
Solution Approach 1:
The coating layer serves as an intermediary barrier that prevents direct interaction between the high-voltage rocksalt material and residual lithium salts in the electrolyte. This mediation reduces side reactions and the generation of harmful factors, thereby lowering cell resistance while maintaining high energy density.
Solution Approach 2:
The coating layer is applied in advance to prevent side reactions before they can occur during high-voltage cycling. By establishing this protective barrier beforehand, the patent prevents the formation of harmful by-products that would increase cell resistance, thus maintaining low resistance while achieving high energy density.
3Reliability
If coating layer is applied to stabilize disordered rocksalt material, then capacity retention is improved, but initial capacity may be reduced
Solution Approach 1:
The patent applies local quality by creating a coating layer with specific composition (lithium phosphate and lithium phosphide) only on the surface of the rocksalt particles. This localized modification provides stability and improves capacity retention without significantly affecting the bulk material's capacity, thus resolving the contradiction between improved reliability and maintained quantity of substance.
Solution Approach 2:
The patent employs parameter changes by carefully controlling the coating thickness and composition ratios to optimize performance. By adjusting these parameters, the coating provides sufficient protection to improve capacity retention while minimizing the impact on initial capacity, effectively resolving the trade-off between reliability and quantity of substance.
Data Source
AI summary
A cathode includes a disordered rocksalt phase material and a coating layer disposed on a surface of the disordered rocksalt phase material. The coating layer may include one or more of an oxide, a phosphate, a phosphide, or a fluoride.