Composite Cathode Coating for Lithium Battery Stability
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Solution Overview
Problem
Lithium-Ni composite oxides in lithium batteries have unstable structures and low thermal stability due to excessive lithium deintercalation, leading to capacity deterioration and side reactions with electrolytes, which affects battery performance.
Innovation Solution
A composite cathode active material with a core of lithium compound coated with a layer of at least two oxide phases having different structures, such as spinel-structured and layer-structured oxides, is developed to reduce surface lithium and inhibit side reactions, improving battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Li-Ni composite oxides are used as cathode active materials to reduce manufacturing costs and increase capacity, then energy density and productivity are improved, but structural stability and thermal stability deteriorate due to excessive lithium deintercalation
Solution Approach 1:
A coating layer comprising at least two oxide phases with different structures is introduced as an intermediary between the Li-Ni composite oxide core and the electrolyte. This coating layer mediates the interaction by reducing residual lithium on the surface and preventing direct contact between the unstable cathode material and electrolyte, thereby resolving the contradiction between high energy density and structural stability
Solution Approach 2:
The cathode active material is designed as a composite structure with a Li-Ni composite oxide core and a multi-phase oxide coating layer. This composite material approach allows the core to provide high capacity while the coating layer provides structural stability and thermal stability, resolving the contradiction between productivity and reliability
2Productivity
If a large amount of lithium is deintercalated from Li-Ni composite oxides during charging to increase capacity, then energy density is improved, but capacity retention and lifespan deteriorate due to structure collapse
Solution Approach 1:
The multi-phase oxide coating layer is formed beforehand on the cathode active material surface to cushion and prevent structure collapse during charging and discharging cycles. The coating layer absorbs mechanical stress and prevents oxygen deintercalation, thereby protecting the core structure and extending battery lifespan while maintaining high discharge capacity
Solution Approach 2:
The coating layer acts as an intermediary that protects the core Li-Ni composite oxide from direct exposure to harsh electrochemical environments during cycling. This intermediary layer prevents capacity deterioration and extends lifespan while allowing the core to deliver high discharge capacity
3Productivity
If residual lithium remains on the surface of Li-Ni composite oxides, then initial capacity is improved, but side reactions with electrolyte increase reducing thermal stability
Solution Approach 1:
The coating layer comprising at least two oxide phases serves as an intermediary between residual lithium on the cathode surface and the electrolyte. It selectively allows lithium to participate in initial capacity formation while preventing harmful side reactions with the electrolyte, thereby resolving the contradiction between initial capacity and thermal stability
Solution Approach 2:
The coating layer converts the potentially harmful residual lithium on the surface into a beneficial element by facilitating controlled reactions that form stable oxide phases. These phases then serve as protective layers that enhance thermal stability while maintaining the capacity benefits of residual lithium
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 cathode active material enhances initial capacity, rate capability, and lifespan of lithium batteries by stabilizing the structure and reducing gas generation, resulting in improved battery performance.
Implementation Method 1
Lithium remaining on the surface of the core may partially be involved in reactions with the coating layer to form the at least two oxide phases having different structures
Implementation Method 2
there is a need to stabilize the Li—Ni composite oxides to improve battery performance by reducing an amount of residual lithium therein and inhibiting side reactions between the composite cathode active material and an electrolyte
Data Source
AI summary
A composite cathode active material including a core comprising a lithium compound, and a coating layer formed on at least one portion of the core and including at least two oxide phases having different structures, a cathode and a lithium battery including the same, and a method of preparing the composite cathode active material.