Bimodal Cathode Coating for Stable Lithium Secondary Batteries
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Solution Overview
Problem
Bimodal-type positive electrode active materials experience reduced electrochemical properties and stability due to non-uniform coating layer formation on small and large particles, leading to issues like cell swelling and reduced cycle life.
Innovation Solution
A bimodal-type positive electrode active material comprising a first lithium composite oxide with a specific grain boundary density and a second lithium composite oxide with a different grain boundary density, both coated with metal oxides, ensuring a balanced occupancy ratio of coating layers to enhance stability and electrochemical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If small particles and large particles are simultaneously calcined with coating raw material, then coating layer is formed on particle surfaces, but non-uniform coating occurs due to predisposition toward small particles with larger specific surface area, reducing electrochemical properties and stability
Solution Approach 1:
The patent divides the coating process into two separate stages: first calcining small particles with coating raw material to form a coating layer, then separately calcining large particles with coating raw material. This segmentation prevents the coating raw material from being preferentially consumed by small particles during simultaneous calcination, ensuring uniform coating distribution across both particle sizes and improving both coating uniformity and electrochemical stability.
2Quantity of substance
If bimodal-type positive electrode active material is used to increase integration density and energy density, then energy density per unit volume increases, but non-uniform coating formation occurs leading to cell swelling and reduced cycle life
Solution Approach 1:
The patent applies segmentation by separating the coating process into two distinct calcination steps: first treating small particles with coating raw material, then treating large particles with coating raw material. This ensures that both particle sizes receive adequate coating without the raw material being preferentially consumed by small particles, thereby maintaining coating uniformity while preserving the high energy density benefits of the bimodal structure and preventing cell swelling and cycle life reduction.
Data Source
Figure 1~2
AI summary
The present invention relates to a positive electrode active material and a lithium secondary battery including the same, and more particularly, to a bimodal-type positive electrode active material including a first lithium composite oxide, which is a small particle, and a second lithium composite oxide, which is a large particle, these particles having different particle diameters, wherein the positive electrode active material makes it possible to prevent deterioration in electrochemical properties and stability thereof, which are generated due to nonuniform formation of a coating layer at least partially coating surfaces of the small and large particles, a positive electrode including the positive electrode active material, and a lithium secondary battery using the same.