Coated Lithium Cobaltate Particles for High-Voltage Stability
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Solution Overview
Problem
Current lithium ion secondary batteries face issues with capacity deterioration, short battery life, gas generation, and thermal instability, particularly at high temperatures, due to limitations in the positive electrode active material's ability to maintain high energy density and cycle stability.
Innovation Solution
A positive electrode active material is developed with a complex oxide particle coated with elements from Groups 2 to 13 and phosphorus, silicon, or germanium, where these elements show different distributions, enhancing lithium ion diffusion and stability, thereby improving charge and discharge efficiency and suppressing gas generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the charging voltage is increased to increase energy density, then the capacity of the battery is improved, but capacity deterioration occurs and battery life becomes short
Solution Approach 1:
The patent applies composite materials by coating the surface of lithium cobaltate particles with a composite layer containing lithium phosphate and metal oxide. This composite structure protects the bulk material from degradation while enabling high-voltage operation, thus maintaining high capacity over extended cycle life.
Solution Approach 2:
The patent applies local quality by creating a surface coating layer with different chemical composition and properties than the bulk material. The coating layer is specifically designed to provide chemical stability and protect against degradation at the surface, while the bulk lithium cobaltate maintains its high-capacity electrochemical properties.
2Quantity of substance
If the charging voltage is increased to increase energy density, then the capacity of the battery is improved, but gas is generated in high-temperature environments causing liquid leakage and deformation
Solution Approach 1:
The patent uses a composite coating layer combining lithium phosphate and metal oxide to suppress gas generation at high temperatures. This composite structure provides thermal stability and prevents the harmful gas evolution that occurs with conventional materials when operated at high voltages and temperatures.
Solution Approach 2:
The patent applies preliminary anti-action by pre-coating the lithium cobaltate surface with a protective layer before battery operation. This coating prevents chemical reactions and gas generation at the electrode-electrolyte interface, especially under high-temperature conditions, thereby preventing liquid leakage and battery deformation.
3Reliability
If a coating layer is applied to improve cycle characteristic and thermal stability, then reliability is improved, but lithium ion diffusion may be inhibited
Solution Approach 1:
The patent applies local quality by creating a coating layer with specific local properties that differ from the bulk material. The coating is designed to be thin and selectively permeable, providing protection where needed while allowing lithium ion transport. The metal oxide component specifically facilitates ion diffusion while the lithium phosphate provides structural stability.
Solution Approach 2:
The patent applies porous materials by using a coating structure that allows lithium ion transport. The coating layer is designed with sufficient porosity and ion-conducting pathways to maintain fast ion diffusion kinetics while providing protective functions. The metal oxide component contributes to creating ion-conducting channels through the coating layer.
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 solution achieves high capacity, extended cycle life, and reduced gas generation in lithium ion secondary batteries, even at high temperatures, by optimizing the distribution of coating elements on the complex oxide particles, leading to improved energy density and thermal stability.
Implementation Method 1
enhancing lithium ion diffusion and stability
Implementation Method 2
enhancing thermal stability by coating a metal oxide on the surface of a positive electrode active material
Data Source
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AI summary
A positive electrode active material includes: a complex oxide particle containing at least lithium and one or plural transition metals; and a coating layer provided in at least a part of the complex oxide particle, wherein the coating layer contains at least one element M which is different from the principal transition metal constituting the complex oxide particle and which is selected among elements belonging to the Groups 2 to 13, and at least one element X selected among phosphorus (P), silicon (Si) and germanium (Ge), and the element M and the element X show different distribution from each other in the coating layer.