Core-Shell Cathode Precursor for High-Ni Crack and Gas Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional nickel cobalt manganese-based lithium composite transition metal oxide secondary particles have low structural and chemical stability, leading to particle cracking and gas production during lithium secondary battery operation, especially when high-Ni content is used for high capacity, resulting in poor thermal stability and electrochemical performance.
Innovation Solution
A secondary particle precursor for the positive electrode active material is developed with a core-shell structure, where the core has higher porosity than the shell, and the particles are agglomerates of primary macro particles with increased average particle and crystal sizes, reducing particle cracking and improving gas performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional secondary particles are formed by agglomeration of primary micro particles, then high specific surface area is achieved, but particle cracking occurs during rolling process
Solution Approach 1:
The invention divides the secondary particle into multiple primary macro particles (each with diameter ≥1 μm) that are loosely aggregated, rather than using fine primary micro particles. This segmentation approach maintains high specific surface area while each primary macro particle retains sufficient mechanical strength to resist cracking during rolling.
Solution Approach 2:
The invention changes the particle size parameter of primary particles from micrometer scale (conventional) to macro particle scale (≥1 μm diameter). This parameter change fundamentally alters the mechanical properties, providing sufficient strength to withstand rolling while maintaining high surface area through the multi-particle aggregation structure.
2Quantity of substance
If high-Ni content is used to ensure high capacity, then energy density is improved, but structural and chemical stability deteriorates
Solution Approach 1:
The invention applies local quality by creating a core-shell structure where the surface region (shell) has different composition and properties from the interior (core). The shell contains lower Ni content and higher Co/Mn content to provide stability, while the core maintains high Ni content for capacity, thus resolving the contradiction locally.
Solution Approach 2:
The invention uses composite material strategy by combining multiple transition metal elements (Ni, Co, Mn) in a core-shell configuration. The composite structure allows high-Ni core for capacity while the outer shell provides structural stability, achieving both high capacity and stability simultaneously.
3Quantity of substance
If secondary particles are formed by agglomeration of primary micro particles, then high capacity is achieved, but gas production increases during cell operation
Solution Approach 1:
The secondary particle is segmented into multiple discrete primary macro particles (3-10 particles per secondary particle) rather than being a single dense mass. This segmentation reduces internal stress concentration and prevents crack formation that would otherwise lead to gas production during cycling.
Solution Approach 2:
Changing the primary particle size to macro scale (≥1 μm) fundamentally reduces the number of grain boundaries and defect sites compared to fine micro particles. This parameter change decreases the nucleation sites for gas formation while maintaining high capacity through the aggregated structure.
Data Source
AI summary
A secondary particle precursor, a positive electrode active material and a lithium secondary battery prepared from the same, and a method of preparing the same are disclosed herein. In some embodiments, a secondary particle precursor comprises one or more particles having a core and a shell surrounding the core, wherein a particle size (D50) of the secondary particle precursor is 6±2 μm, a particle size (D50) of the core is 1 to 5 μm, and the core has higher porosity than the shell. A positive electrode active material prepared using the secondary particle precursor has an increased press density and reduced cracking.