Cathode Active Material Particle Size Distribution for Battery Density
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Solution Overview
Problem
Current cathode active materials for lithium ion secondary batteries face challenges in achieving high packing properties and volume capacity density, with existing methods either leading to excessive particle size, increased surface area, safety concerns, or poor handling efficiency, and inadequate cycle properties.
Innovation Solution
A cathode active material comprising a mixture of large and small particles with specific particle size distributions, where the mixture is pressed to maintain a high porosity and controlled particle size changes, allowing for efficient packing without excessive surface area exposure, achieved through a method involving the mixing and firing of lithium composite oxides with nickel, cobalt, and manganese compounds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the average particle size of cathode active material is increased to improve pressed density, then the pressed density increases, but the specific surface area decreases leading to reduced reaction interface and lower intercalation reaction rate
Solution Approach 1:
The invention segments the particle population into two distinct size categories: large particles (10-30 μm) that provide high pressed density and structural stability, and small particles (0.1-10 μm) that provide high specific surface area and fast reaction kinetics. This segmentation allows each particle size to fulfill its specific function without compromising the other.
Solution Approach 2:
The invention applies local quality by assigning different particle sizes to different functional requirements within the same electrode material. Large particles are optimized for packing density and mechanical strength, while small particles are optimized for surface reactivity and ion transport. The dual-mode particle size distribution creates local optimization throughout the electrode structure.
2Productivity
If small particles are used to increase specific surface area and reaction interface, then the intercalation reaction rate improves, but the pressed density decreases and handling efficiency deteriorates
Solution Approach 1:
The invention segments the particle population into two distinct size categories: large particles (10-30 μm) that provide high pressed density and structural stability, and small particles (0.1-10 μm) that provide high specific surface area and fast reaction kinetics. This segmentation allows each particle size to fulfill its specific function without compromising the other.
3Manufacturing precision
If primary particles are allowed to grow excessively large to improve pressed density, then the pressed density increases, but the specific surface area becomes too small reducing the reaction interface with electrolyte
Solution Approach 1:
The invention segments the particle population into two distinct size categories: large particles (10-30 μm) that provide high pressed density and structural stability, and small particles (0.1-10 μm) that provide high specific surface area and fast reaction kinetics. This segmentation allows each particle size to fulfill its specific function without compromising the other.
4Manufacturing precision
If a mixed powder with wide particle size distribution is used to improve packing properties, then the pressed density improves, but the particle size control becomes difficult and electrochemical properties deteriorate
Solution Approach 1:
The invention applies local quality by assigning different particle sizes to different functional requirements within the same electrode material. Large particles are optimized for packing density and mechanical strength, while small particles are optimized for surface reactivity and ion transport. The dual-mode particle size distribution creates local optimization throughout the electrode structure.
Solution Approach 2:
The invention applies parameter changes by precisely controlling the particle size distribution parameters within specific ranges rather than using a wide uncontrolled distribution. The particle size is controlled within 0.1-30 μm with specific sub-distributions for small (0.1-10 μm) and large (10-30 μm) particles, ensuring optimal electrochemical performance while maintaining high pressed density.
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 solution results in a cathode active material with enhanced packing properties and volume capacity density, improving battery performance by maintaining a stable particle size distribution and preventing excessive surface area exposure, thus enhancing safety and cycle efficiency.
Implementation Method 1
the function E(x) of a particle size x of a particle contained in a mixture B′ after the mixture B is pressed by 1.92 t/cm2
Implementation Method 2
it is possible to improve the packing properties, since small particles will enter into spaces among large particles
Implementation Method 3
a method for its production which comprises mixing a powder P which is a collection of plural particles having different particle sizes and which is made of large particle size lithium composite oxide
Data Source
AI summary
To provide a cathode active material for a lithium ion secondary battery, which has high packing properties and high volume capacity density, and a method for its production. A cathode active material for a lithium ion secondary battery is used, which comprises a mixture B of a collection of many large particles having different particle sizes and a collection of many small particles having different particle sizes, wherein the function F(x) of a particle size x of a particle contained in the mixture B and its frequency F has a relation of the formula 1, the function E(x) of a particle size x of a particle contained in a mixture B′ after the mixture B is pressed and its frequency E has a relation of the formula 2, the rate of change of the median size μ′g relative to μg is at most 10%, and the rate of change of the median size μ′h relative to μh is at least 20%,F(x)=Ag×12πσgxexp{-(logx-μg)22σg2}+Ah×12πσhxexp{-(logx-μh)22σh2}Formula1E(x)=Ag′×12πσg′xexp{-(logx-μg′)22σg′2}+Ah′×12πσh′xexp{-(logx-μh′)22σh′2}Formula2