Cathode Coating Reducing Rocksalt Formation in Lithium Batteries
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Solution Overview
Problem
Existing positive electrode materials with large primary particles form a rocksalt structure on the surface, leading to deteriorated electrochemical performance due to high contact with electrolytic solutions, and existing methods to increase particle size further degrade performance.
Innovation Solution
A positive electrode active material with a metal oxide core having a layered structure and a coating layer with a smaller interplanar distance than the core, composed of elements like Co, Al, and Zr, to modify the surface structure and improve electrochemical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the size of primary particles is increased using a sintering agent or flux, then the plate density of the electrode is improved, but a rocksalt structure is produced on the surface portion of the particles which deteriorates the electrochemical performance
Solution Approach 1:
The invention applies a coating layer with different properties (smaller interplanar distance) only on the surface portion of the positive electrode active material particles. This local modification allows the bulk material to maintain its high-density structure while the surface exhibits improved electrochemical characteristics, resolving the contradiction between plate density and electrochemical performance.
Solution Approach 2:
The invention creates a composite structure consisting of the metal oxide core (with layered structure) and the coating layer (with smaller interplanar distance). This composite material combines the advantages of both components: the core provides high plate density while the coating layer provides superior electrochemical performance by preventing rocksalt structure formation.
2Quantity of substance
If a secondary particle form is used formed by agglomeration of primary particles, then the plate density is improved, but the large powder specific surface area causes high possibility of gassing and deterioration of life characteristics
Solution Approach 1:
The coating layer is applied specifically on the surface of the particles to modify only the surface properties. This local modification reduces the harmful surface area effects (gassing and life deterioration) while preserving the beneficial bulk properties (plate density) of the secondary particle structure.
Solution Approach 2:
The coating layer acts as an intermediary between the particle interior and the electrolytic solution. It mediates the interaction by providing a protective interface that reduces direct contact between the electrolyte and the particle surface, thereby reducing gassing and improving life characteristics while maintaining good electrochemical performance.
3Reliability
If the interplanar distance of the layered structure is reduced in the coating layer, then the electrochemical performance is enhanced, but the manufacturing complexity increases
Solution Approach 1:
The invention changes the structural parameter (interplanar distance) of the coating layer to achieve improved electrochemical performance. By controlling the coating composition and processing conditions, the interplanar distance is reduced to enhance lithium ion diffusion and electrochemical activity, while the overall manufacturing process remains feasible through standard coating techniques.
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 modified surface structure enhances electrochemical performance, reducing resistance and increasing lifespan, while maintaining high energy density and capacity.
Implementation Method 1
an average interplanar distance value of the layered structure included in the coating layer is smaller than an average interplanar distance value of the layered structure included in the metal oxide
Data Source
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AI summary
The present exemplary embodiments relate to a positive electrode active material for a lithium secondary battery, and a lithium secondary battery including the same. The positive electrode active material for a lithium secondary battery according to an exemplary embodiment includes: a metal oxide which is in the form of a single particle and includes a layered structure; and a coating layer which is positioned on the surface of the metal oxide and includes a layered structure, wherein an average interplanar distance value of the layered structure included in the coating layer is smaller than an average interplanar distance value of the layered structure included in the metal oxide.