Aluminum-Boron Cathode Coating for High-Nickel Surface Stability
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Solution Overview
Problem
Lithium composite oxides used in secondary batteries suffer from stability issues due to surface reactions with impurities and electrolytes, leading to reduced lifespan and performance, particularly when exposed to the atmosphere or contact with electrolytes, especially with high nickel content.
Innovation Solution
A cathode active material is developed with a first coating part containing aluminum and a second coating part containing boron, sequentially formed on the surface of a lithium composite oxide, which stabilizes the surface structure and reduces reaction areas with the electrolyte.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium composite oxide with high nickel content is used to increase capacity, then battery capacity is improved, but surface stability deteriorates due to formation of lithium impurities (LiOH, Li2CO3) and increased side reactions with electrolyte
Solution Approach 1:
The patent introduces an aluminum-containing coating layer as an intermediary substance between the high-nickel lithium composite oxide surface and the electrolyte. This coating layer acts as a protective mediator that prevents direct contact between the unstable high-nickel surface and the electrolyte, thereby maintaining surface stability while preserving the high capacity benefits of high-nickel content
Solution Approach 2:
The patent creates a composite surface structure by combining lithium composite oxide with high nickel content and an aluminum-containing coating layer. This composite material approach allows the inner high-nickel core to provide high capacity while the outer aluminum-containing layer provides surface stability and resistance to side reactions
2Quantity of substance
If washing process is used to remove lithium impurities, then purity is improved, but specific surface area increases which activates side reactions with electrolyte and deteriorates surface structure stability
Solution Approach 1:
The patent applies preliminary action by forming the aluminum-containing coating layer on the surface before the lithium composite oxide is exposed to the electrolyte during battery operation. This pre-formed coating prevents the instability that would otherwise result from washing-induced surface area increase, as the coating is already in place to protect the surface structure
3Reliability
If aluminum coating is formed to stabilize surface structure, then surface stability is improved, but manufacturing complexity increases due to additional coating process
Solution Approach 1:
The patent utilizes parameter changes by controlling the pH value within a specific range (6.5 to 8.5) during the coating process. This parameter control allows the aluminum-containing coating to form under relatively mild conditions, simplifying the manufacturing process while still achieving the desired surface stability
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 aluminum and boron coatings enhance the stability and electrical properties of the cathode active material, improving the lifespan and high-temperature stability of lithium secondary batteries.
Implementation Method 1
a first coating part formed on a surface of the lithium composite oxide and containing aluminum
Implementation Method 2
a second coating part formed on the first coating part and containing boron
Data Source
AI summary
A cathode active material for a lithium secondary battery of embodiments of the present invention includes a lithium composite oxide, a first coating part formed on a surface of the lithium composite oxide and containing aluminum, and a second coating part formed on the first coating part and containing boron. Thereby, stability and electrical characteristics of the secondary battery may be improved.