Nickel Cathode Macro-Particle Structure to Prevent Rolling Cracks
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Solution Overview
Problem
Conventional NCM based lithium composite transition metal oxide secondary particles, formed by agglomeration of primary micro particles, exhibit high specific surface area and low particle rigidity, leading to particle cracking during the rolling process, resulting in low structural and thermal stability, especially in high-Ni variants.
Innovation Solution
A method to prepare a positive electrode active material comprising secondary particles formed by agglomerating primary macro particles, with controlled sintering temperatures and compositions, ensuring the primary macro particles have an average size of 2 µm or more and a crystal size ratio of 8 or more, minimizing cracking during rolling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If secondary particles are formed by agglomeration of primary micro particles, then high specific surface area is achieved, but particle rigidity is low leading to severe particle cracking during rolling process
Solution Approach 1:
The invention changes the particle size parameter from micro-scale (0.5-2 μm) to macro-scale (2-10 μm) primary particles. This parameter change fundamentally alters the mechanical properties, providing sufficient particle rigidity to withstand rolling pressure while maintaining adequate surface area for lithium ion insertion/extraction reactions.
2Strength
If primary particle size is increased to improve particle rigidity, then particle cracking is reduced, but specific surface area decreases
Solution Approach 1:
The invention uses partial agglomeration of primary macro particles to form secondary particles. The secondary particle structure provides mechanical strength through the agglomerate framework while the individual primary macro particles maintain sufficient size for rigidity. This partial action approach balances both requirements rather than using complete agglomeration which would excessive reduce surface area.
3Productivity
If conventional sintering is used to form secondary particles, then production efficiency is maintained, but particle cracking occurs during rolling process
Solution Approach 1:
The invention performs preliminary sintering to form primary macro particles with adequate rigidity before the rolling process. By pre-establishing the mechanical strength of primary particles through controlled sintering conditions (temperature, time, atmosphere), the subsequent rolling process can proceed without severe particle cracking, ensuring both production efficiency and structural stability.
4Quantity of substance
If high-Ni NCM based lithium composite transition metal oxide is used to achieve high capacity, then energy density is improved, but structural and chemical stability is reduced
Solution Approach 1:
The invention changes the particle size parameter to macro-scale (2-10 μm) which fundamentally alters the mechanical behavior. Larger particles have lower surface area to volume ratio, reducing surface stress concentration and improving structural stability. This parameter change allows high-Ni compositions to maintain both high capacity and improved structural/chemical stability during cycling.
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 provides a nickel-based positive electrode active material with high press density, long life, and improved gas performance by growing the primary macro particle size and crystal size, reducing cracking and increasing stability.
Implementation Method 1
mixing a nickel-based transition metal oxide precursor having a tap density of 2.0 g/cc or less and a lithium precursor and performing primary sintering; and performing secondary sintering on the primary sintered product
Data Source
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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, there is provided a positive electrode active material comprising secondary particles with improved resistance by simultaneously growing the average particle size (D50) and the crystal size of the primary macro particle. According to an embodiment of the present disclosure, it is possible to provide a nickel-based the positive electrode active material with high press strength, long life and good gas performance.