Battery Cathode Granulation for Uniform Secondary Particles
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Solution Overview
Problem
Existing methods for synthesizing disordered rock salt structure lithium-rich oxide cathode materials result in inhomogeneous particle morphology with multimodal size distribution, leading to poor electrochemical performance, increased reactivity, and reduced energy density due to electrolyte degradation and grain formation during current collector coating.
Innovation Solution
A process involving a granulation step in a mixture of immiscible organic solvents to form spheroidal secondary particles with a unimodal size distribution, reducing primary particle size to less than 2 µm and agglomerating them into secondary particles with controlled morphology and higher density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If mechanosynthesis is used to synthesize cathode materials, then production cost is reduced by eliminating cobalt and nickel, but particle morphology becomes inhomogeneous with multimodal size distribution leading to poor electrochemical performance
Solution Approach 1:
The patent applies preliminary action by performing a first grinding step to reduce primary particle size to nanometric dimensions (less than 1000 nm) before the second grinding step. This preliminary size reduction prepares the particles for controlled agglomeration during the subsequent granulation process, ensuring that the final secondary particles have uniform morphology and size distribution while maintaining the cost benefits of mechanosynthesis
Solution Approach 2:
The patent uses an intermediary liquid medium (water or organic solvent) during the second grinding step to facilitate controlled agglomeration of primary particles into secondary particles with desired morphology. This liquid intermediary enables the transformation from inhomogeneous nanometric particles to uniformly shaped secondary particles with controlled size distribution, resolving the morphology control issue while maintaining production cost efficiency
2Length of moving object
If particle size is reduced to nanometric value by grinding, then particle size is reduced to less than 1000 nm, but cycling performance decreases due to electrolyte degradation and surface densification
Solution Approach 1:
The patent merges multiple primary particles into secondary particles through controlled agglomeration in a liquid medium. This combining approach creates larger secondary particles (with Dv0.5 between 1-50 μm) that have reduced specific surface area compared to individual nanometric particles, thereby reducing electrolyte degradation and surface densification while maintaining the fine particle size benefits for electrochemical performance
Solution Approach 2:
The patent creates a nested structure where multiple primary particles (nanometric grains) are embedded within secondary particles. This nested arrangement allows the material to benefit from both the nanometric primary particle size (which provides good electrochemical activity) and the larger secondary particle structure (which reduces harmful surface effects and improves cycling stability)
3Object-affected harmful factors
If particles are pulverized to nanometric size, then reactivity increases, but energy density is reduced due to increased reactivity and energy loss in electrochemical cell
Solution Approach 1:
By merging nanometric primary particles into secondary particles, the patent reduces the total specific surface area of the material. This reduction in surface area decreases the reactivity with electrolyte and ambient air, thereby reducing energy loss through side reactions while maintaining the high electrochemical activity provided by the nanometric primary particle structure
4Ease of manufacture
If inhomogeneous particle morphology is produced by mechanosynthesis, then production is simplified, but grain formation occurs during current collector coating complicating fabrication
Solution Approach 1:
The patent performs preliminary grinding and controlled agglomeration steps before the coating process to pre-form particles with optimal morphology and size distribution. This preliminary preparation ensures that the material is ready for smooth coating onto current collectors without grain formation, maintaining the simplicity of mechanosynthesis while improving coating processability
Solution Approach 2:
The liquid medium used during the second grinding step serves as an intermediary that enables controlled agglomeration into uniformly shaped secondary particles. This intermediary process transforms the inhomogeneous particles from mechanosynthesis into uniformly shaped secondary particles that coat smoothly onto current collectors, eliminating grain formation while keeping the overall process simple
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 improved electrochemical performance, reduced reactivity, and increased energy density by forming spheroidal secondary particles with a controlled size distribution, facilitating easier handling and coating into electrodes.
Implementation Method 1
a granulation step of the material in pulverized form, the material consisting of a mixture of particles, called primary particles, of substantially unimodal size distribution and of average volume diameter, determined by laser diffraction, less than or equal to 2 µm
Data Source
Figure 1a~1d
Figure 2a~2c
Figure 3a~3c
AI summary
The invention relates to a method for preparing a cathode material for a battery, comprising a step of obtaining this cathode material in the form of a mixture of so-called primary particles, with a monomodal size distribution and a volume average diameter less than or equal to 2 µm, then a step of shaping said mixture of primary particles by granulation by grinding in a ball mill, in a mixture of organic solvents comprising a polar organic solvent and an apolar organic solvent, the polar organic solvent and the apolar organic solvent being immiscible. The cathode material in particulate form thus obtained has good electrochemical performance, low reactivity and high energy density.