Nickel Cathode Active Material Composition for Crack-Resistant Rolling
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Solution Overview
Problem
Existing lithium secondary battery positive electrode active materials suffer from particle cracking and increased surface area during the rolling process, leading to poor life characteristics and electrical conductivity losses due to the use of secondary particles formed by agglomeration of primary particles.
Innovation Solution
A positive electrode active material comprising a first monolith and a second secondary particle, where the first monolith has an average particle size of 3 to 10 µm and the second secondary particle is an agglomerate of primary macro particles with an average size of 1 µm or more, and a specific weight ratio, which minimizes particle cracking during the rolling process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If secondary particles formed by agglomeration of primary particles are used to increase output and packing density, then packing density is improved, but particle cracking occurs during rolling leading to poor life characteristics
Solution Approach 1:
The patent segments the positive electrode active material into two distinct particle size categories: micro particles (D50: 0.5-2.0 μm) and macro particles (D50: 2.0-10.0 μm). This segmentation allows each particle type to fulfill different functional roles - micro particles fill voids to increase packing density while macro particles maintain structural integrity during rolling, thereby resolving the contradiction between packing density and life characteristics.
Solution Approach 2:
The patent applies local quality by creating a heterogeneous particle size distribution within the positive electrode active material. Instead of using uniform particles, it combines fine micro particles for density optimization with larger macro particles for mechanical strength, allowing different regions of the electrode to have different particle characteristics optimized for their specific functions.
2Quantity of substance
If secondary particles with agglomerated primary particles are used, then packing density increases, but electron movement path losses occur due to cracks
Solution Approach 1:
By segmenting particles into micro and macro sizes, the patent ensures that macro particles provide continuous electron transport paths while micro particles fill interstitial spaces. This segmentation prevents crack formation that would disrupt electron pathways, thereby maintaining electrical conductivity while achieving high packing density.
Solution Approach 2:
The patent creates a composite particle system combining micro particles and macro particles with different properties. The macro particles serve as structural骨架 providing electron transport pathways, while micro particles fill voids to increase density without compromising the continuity of electron movement paths.
3Area of stationary object
If surface area is increased due to particle cracking, then more reaction sites are available, but side reactions with electrolyte solution increase
Solution Approach 1:
The patent uses segmentation to provide controlled surface area through micro particles that are intact and uniformly sized, rather than through cracking of larger particles. This controlled segmentation increases surface area for beneficial reactions while avoiding the harmful effects of uncontrolled cracking that exposes fresh surfaces to electrolyte decomposition.
Solution Approach 2:
The patent converts the potential harm of increased surface area from cracking into a benefit by deliberately using fine micro particles with high surface area to volume ratio. These micro particles provide abundant reaction sites for lithium insertion/extraction without the accompanying harm of crack-induced electrolyte decomposition, as their surface area is inherent to their size rather than created by damaging fragmentation.
4Strength
If monolithic particles are used to maintain structural integrity, then particle strength is improved, but packing density decreases
Solution Approach 1:
The patent applies segmentation by dividing the particle population into two size groups: macro particles (2.0-10.0 μm) that provide structural strength and monolithic characteristics, and micro particles (0.5-2.0 μm) that increase packing density. This segmentation allows the system to achieve both high particle strength from macro particles and high packing density from micro particles filling the voids between larger particles.
Solution Approach 2:
The patent creates a composite particle system where macro monolithic particles provide mechanical strength and structural integrity, while micro particles fill the interstitial spaces to increase packing density. This composite approach combines the advantages of both large monolithic particles (strength) and fine particles (density), achieving a synergistic effect that neither particle size alone could provide.
Data Source
Figure 1a~1c
AI summary
The present disclosure relates to a positive electrode active material comprising at least one secondary particle comprising an agglomerate of primary macro particles, a method for preparing the same and a lithium secondary battery comprising the same. According to an embodiment of the present disclosure, by the simultaneous use of the secondary particle comprising primary macro particles and the 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.