Nickel Cathode Particle Segmentation for Crack-Resistant Rolling
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Solution Overview
Problem
Lithium secondary batteries face particle cracking and reduced life characteristics during the rolling process due to electron movement path losses and side reactions with the electrolyte, particularly when using secondary particles formed by agglomeration of primary particles.
Innovation Solution
A positive electrode active material comprising a combination of a monolith and a secondary particle formed by agglomeration of primary macro particles, with controlled particle sizes and strengths, to minimize cracking and improve life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If secondary particles formed by agglomeration of primary particles are used to increase output and press density, then energy density is improved, but particle cracking occurs during rolling process leading to poor life characteristics
Solution Approach 1:
The positive electrode active material is segmented into two distinct particle size groups: small particles (D50: 3-10 μm) and large particles (D50: 10-20 μm). This segmentation allows small particles to fill voids between large particles, increasing packing density and energy density, while the large particles provide structural integrity and resistance to cracking during the rolling process, thus improving life characteristics.
2Volume of stationary object
If secondary particles with agglomerated primary particles are used, then press density is improved, but electron movement path losses increase due to particle cracking
Solution Approach 1:
The particle size segmentation into small (D50: 3-10 μm) and large (D50: 10-20 μm) particles enables efficient space utilization, achieving high press density without the need for heavily agglomerated secondary particles. The small particles fill the interstices between large particles, creating a compact structure that maintains good electron transport pathways and reduces electron movement path losses.
3Volume of stationary object
If secondary particles with agglomerated primary particles are used, then press density is improved, but side reactions with electrolyte solution increase due to increased surface area from cracks
Solution Approach 1:
By segmenting the particle size distribution into small (D50: 3-10 μm) and large (D50: 10-20 μm) particles, the invention achieves high press density through efficient packing rather than through particle agglomeration that creates cracks. This eliminates the source of increased surface area that would otherwise lead to excessive side reactions with the electrolyte solution.
4Strength
If monolith with larger average particle size is used, then particle strength is improved, but electron transport path length increases
Solution Approach 1:
The invention uses a segmented particle size distribution with large particles (D50: 10-20 μm) providing structural strength and small particles (D50: 3-10 μm) filling the spaces between them. This segmentation ensures that the electron transport path length remains short as electrons can move through the closely packed small particles, while the large particles maintain overall particle strength.
Data Source
AI summary
Provided is a positive electrode active material comprising at least one secondary particle comprising an agglomerate of a primary macro particle, a method for preparing the same and a lithium secondary battery comprising the same.By the simultaneous use of the secondary particle comprising a primary macro particle and a monolith, it is possible to provide a nickel-based positive electrode active material with reduced particle cracking in the positive electrode active material during a rolling process and improved charge/discharge cycling characteristics.