High-Nickel Cathode Active Material for Stable Secondary Particles
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Solution Overview
Problem
High-nickel positive electrode active materials face issues with structural degradation and non-uniform particle diameter distribution, leading to reduced conductivity and lifespan, while conventional secondary particles suffer from decreased crystallinity at high heat treatment temperatures.
Innovation Solution
A positive electrode active material comprising secondary particles with aggregated primary particles of specific size ranges and composition, including a lithium transition metal composite oxide with high nickel content, is developed to improve density and crystallinity, using a method to recover the rock salt structure into a layered structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high-nickel positive electrode active material is used to improve capacity characteristics, then energy density is improved, but structural degradation and crack formation occur during charging and discharging
Solution Approach 1:
The positive electrode active material is divided into primary particles (0.5-5 μm) that aggregate to form secondary particles (10-50 μm). This segmentation allows the material to maintain high nickel content for energy density while the smaller primary particles reduce internal stress and prevent crack formation during charging-discharging cycles, resolving the contradiction between energy density and structural stability
Solution Approach 2:
The invention uses composite secondary particle structures where multiple primary particles aggregate together. This composite structure combines the high capacity benefits of high-nickel materials with the mechanical stability of aggregated particles, preventing structural degradation while maintaining improved energy density
2Duration of action of stationary object
If secondary particles with micron-level primary particles are manufactured to improve rolling density and minimize cracks, then lifespan is improved, but heat treatment temperature must be increased which causes layered structure degradation into rock salt structure
Solution Approach 1:
The invention optimizes the heat treatment temperature parameter to a specific range (900-1000°C) that is sufficient to form micron-level primary particles with good rolling density but low enough to prevent severe degradation of the layered structure into rock salt structure. This parameter optimization resolves the contradiction between improving lifespan through better particle morphology and maintaining crystallinity
Solution Approach 2:
The invention creates local quality differences within the secondary particles by controlling the aggregation of primary particles with specific size distributions. The primary particles have controlled sizes (0.5-5 μm) that provide good rolling density and crack resistance, while the overall secondary particle structure (10-50 μm) maintains good crystallinity, resolving the contradiction between lifespan improvement and crystallinity preservation
3Reliability
If single particle structure is used to minimize cracks, then structural stability is improved, but particle diameter distribution becomes non-uniform and specific surface area decreases
Solution Approach 1:
Instead of using single particles, the invention segments the material into primary particles (0.5-5 μm) that aggregate into secondary particles (10-50 μm). This segmentation provides uniform particle diameter distribution through controlled aggregation while the primary particle level maintains structural stability, resolving the contradiction between structural stability and particle uniformity
Solution Approach 2:
The invention uses composite secondary particle structures where multiple uniform primary particles aggregate together. This composite approach maintains particle diameter uniformity at the primary particle level while creating larger secondary particles that provide structural stability, resolving the contradiction between structural stability and manufacturing precision
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 enhances the lifespan and energy density of lithium secondary batteries by improving the density and conductivity of the electrode material, addressing the structural and compositional challenges of high-nickel materials.
Implementation Method 1
heat treatment needs to be performed at a higher temperature than that of a secondary particle having a primary particle size of submicron level less than 1 μm
Implementation Method 2
the layered structure of the lithium transition metal composite oxide degenerates into a rock salt structure
Data Source
Figure 1(A)~1(B)
Figure 2(A)~2(B)
Figure 3(A)~3(B)
AI summary
The present invention relates to a positive electrode active material capable of simultaneously solving the problems of conventional secondary particles and single particles, and a positive electrode and a lithium secondary battery comprising the same, wherein the positive electrode active material includes a secondary particle containing the same particles as the conventional single particles as primary particles and formed by aggregating a plurality of primary particles, whereby it is possible to improve not only cell characteristics such as improved lifespan of the lithium secondary battery and reduced gas generation but also energy density due to excellent density characteristics.