Cathode Active Material Particle Structure for Lower Battery Resistance
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Solution Overview
Problem
Existing cathode active materials face challenges in reducing battery resistance and improving durability, particularly due to the sharp particle size distribution of primary particles.
Innovation Solution
The cathode active material is composed of secondary particles formed from 3 to 20 primary particles with a broad particle size distribution, specifically a DFWHM of 0.10 μm or more, which promotes lithium diffusion and reduces battery resistance while maintaining a decreased contact area with the electrolyte, enhancing durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If primary particles have a sharp particle size distribution, then manufacturing precision is improved, but battery resistance increases
Solution Approach 1:
The patent changes the particle size distribution parameter from sharp to broad (DFWHM ≥ 0.10 μm) to reduce battery resistance. This parameter change allows primary particles of various sizes to coexist within secondary particles, promoting lithium diffusion pathways and reducing overall battery resistance while maintaining controlled aggregation through the secondary particle structure.
2Productivity
If the contact area between secondary particles and electrolyte is increased, then discharge capacity is improved, but durability decreases
Solution Approach 1:
The patent applies local quality by creating heterogeneous particle size distributions within secondary particles, where smaller primary particles provide increased contact area with electrolyte for improved discharge capacity, while the overall secondary particle structure maintains appropriate size and morphology for durability. The broad DFWHM enables this localized optimization within the aggregate structure.
3Productivity
If primary particles are aggregated into secondary particles, then discharge capacity is improved, but battery resistance increases
Solution Approach 1:
The patent changes the particle size distribution parameter (DFWHM ≥ 0.10 μm) of primary particles within secondary particles to broaden the size range. This enables smaller primary particles to provide shorter lithium diffusion paths and increased electrolyte contact, reducing battery resistance while maintaining the aggregate structure's high discharge capacity.
Solution Approach 2:
The patent creates a composite structure where primary particles with diverse sizes are aggregated into secondary particles. This composite approach combines the advantages of small particles (short diffusion paths, high surface area) with the benefits of large particles (structural stability), achieving both high discharge capacity and low battery resistance.
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 broad particle size distribution of primary particles within the secondary particles reduces battery resistance and improves durability, as evidenced by lower initial resistance and higher capacity retention during repeated charge/discharge cycles.
Implementation Method 1
there is a possibility that the presence of primary particles of various sizes coexisting promotes lithium (Li) diffusion within the secondary particles
Implementation Method 2
Synthesizing a lithium metal composite oxide by subjecting the mixture to a heat treatment under an oxygen atmosphere
Data Source
AI summary
The cathode active material includes a plurality of secondary particles. Each of the secondary particles includes three to twenty primary particles. The primary particles contain a lithium metal composite oxide. A structure of the lithium metal composite oxide is a layered-rocksalt structure. The particle size distribution of the primary particles has “Dmin” of 0.3 μm or more and “DFWHM” of 0.10 μm or more. The particle size distribution is number-based distribution. The Dmin indicates a smallest diameter in the particle size distribution. The DFWHM indicates full width at half maximum of a greatest peak of the particle size distribution.