Fluidized Bed Cathode Coating Process for Uniform Surface Protection
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Solution Overview
Problem
Lithium ion batteries face issues with undesired reactions on the surface of cathode active materials, leading to decomposition of the electrolyte or solvent, and challenges in achieving uniform coating due to particle size and agglomeration, which reduces coating efficiency.
Innovation Solution
A process involving treating particulate materials like lithiated nickel-cobalt aluminum oxides and layered lithium transition metal oxides with metal alkoxides or alkyl metal compounds in a fluidized bed, followed by moisture treatment, to achieve at least 80% coating of particles with a thickness of 0.1 to 50 nm, using a reactor with a gas velocity gradient to prevent agglomeration and ensure even coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If particulate materials are coated to protect the surface, then undesired reactions on the cathode surface are prevented, but coating uniformity deteriorates due to particle agglomeration
Solution Approach 1:
The coating process is divided into multiple sequential steps (e.g., silane treatment followed by metal oxide coating), where each step addresses specific aspects of surface protection. This segmented approach allows for better control of coating uniformity while maintaining surface protection benefits
Solution Approach 2:
A preliminary silane treatment step is performed before the main metal oxide coating. This preliminary action modifies the particle surface to improve subsequent coating adhesion and uniformity, preventing agglomeration issues during the main coating process
2Reliability
If conventional coating methods are used, then surface protection is achieved, but reaction time becomes unduly long
Solution Approach 1:
A fluidized bed reactor system is used to deliver reactants as gas or vapor phases to the particulate material. This pneumatic approach dramatically increases the surface area contact between reactants and particles, reducing reaction time from hours to minutes while maintaining effective surface protection
Solution Approach 2:
The coating process utilizes phase transitions of reactants (e.g., liquid to vapor) to enhance mass transfer to the particle surfaces. The vapor-phase reactants condense and react on the particle surfaces, enabling rapid and uniform coating formation in short reaction times
3Productivity
If gas velocity is increased in fluidized bed, then coating efficiency improves, but particle agglomeration worsens
Solution Approach 1:
The gas velocity in the fluidized bed is dynamically controlled and optimized for each specific step of the coating process. Different velocity profiles are used for different stages (e.g., lower velocity during sensitive coating steps, higher velocity for mixing), allowing both high coating efficiency and prevention of agglomeration
Solution Approach 2:
Different regions of the fluidized bed are maintained at different gas velocities to create optimal local conditions. The gas distribution is non-uniform, with higher velocities in regions needing better mixing and lower velocities in regions where gentle coating is required, achieving both efficiency and 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 process achieves high efficiency in coating cathode active materials, ensuring that over 75% of each particle's surface is coated, preventing non-coated areas from reacting, and breaking up agglomerates to access the full particle surface, thereby enhancing battery performance.
Implementation Method 1
treating said cathode active material with a metal alkoxide or metal amide or alkyl metal compound in a fluidized bed
Implementation Method 2
treating said cathode active material with a metal alkoxide or metal amide or alkyl metal compound in a fluidized bed
Implementation Method 3
treating the material obtained in step (b) with moisture in a fluidized bed
Data Source
AI summary
Process for making an at least partially coated particulate material, said process comprising the following steps: (a) providing a particulate material selected from lithiated nickel-cobalt aluminum oxides and layered lithium transition metal oxides, (a) treating said cathode active material with a metal alkoxide or metal amide or alkyl metal compound in a fluidized bed, (b) treating the material obtained in step (b) with moisture in a fluidized bed, and, optionally, repeating the sequence of steps (b) and (c), wherein the superficial gas velocity in the fluidized beds in steps (b) and (c) decreases with increasing reactor height.