Nickel Cathode Particle Structure for Rolling-Stable Capacity Retention
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Solution Overview
Problem
Lithium secondary batteries face challenges with particle cracking and low stability during the rolling process due to the agglomeration of primary micro particles, leading to reduced capacity retention and thermal instability in high-Ni NCM-based lithium composite transition metal oxides.
Innovation Solution
A nickel-based positive electrode active material is developed with secondary particles formed from agglomerates of primary macro particles, coated with lithium boron oxide, having a specific surface area and particle size distribution that minimizes BET change and porosity, thereby reducing particle cracking and enhancing stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If secondary particles are formed by agglomeration of primary micro particles, then capacity is increased, but particle cracking occurs during rolling process and stability decreases
Solution Approach 1:
The patent divides the secondary particle into multiple primary macro particles (1-5 μm) aggregated together, rather than using single large particles or fine micro particles. This segmentation allows the particle to maintain structural integrity during rolling while providing sufficient capacity through the aggregated structure.
Solution Approach 2:
The patent changes the particle size parameter from conventional micro particles (<1 μm) to macro particles (1-5 μm), and controls the specific surface area to 0.2-1.25 m²/g. This parameter change reduces particle cracking during rolling while maintaining electrochemical performance.
2Reliability
If monolith structure is used, then side reactions with electrolyte are reduced and stability is improved, but resistance increases and capacity retention decreases
Solution Approach 1:
The patent applies different properties to different parts of the particle system: the primary macro particles have controlled size and surface area to minimize side reactions, while the aggregated secondary particle structure provides sufficient capacity. This local quality differentiation resolves the contradiction between stability and resistance.
Solution Approach 2:
The patent creates a composite structure where multiple primary macro particles aggregate to form secondary particles, combining the benefits of larger particle stability with the electrochemical activity of distributed surface areas. This composite approach avoids the drawbacks of both monolith and fine particle structures.
3Quantity of substance
If high-Ni NCM-based lithium composite transition metal oxide is used, then capacity is increased, but thermal stability and structural stability decrease
Solution Approach 1:
The patent changes the particle morphology and size parameters (primary macro particles with D50 of 1-5 μm, specific surface area of 0.2-1.25 m²/g) to compensate for the reduced thermal stability of high-Ni materials. This parameter optimization reduces surface reactivity and improves thermal stability while maintaining high capacity.
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 improves capacity retention and life characteristics by controlling BET changes and sintering temperature, reducing particle cracking and fine particle formation, resulting in enhanced electrochemical performance and stability during the rolling process.
Implementation Method 1
all or part of a surface of the secondary particle or the primary macro particle is coated with a lithium boron oxide
Implementation Method 2
at least one secondary particle comprising an agglomerate of primary macro particles
Implementation Method 3
made of an active material capable of intercalating and deintercalating lithium ions
Data Source
AI summary
A positive electrode active material having 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 are provided. A positive electrode active material has improved capacity retention by controlling a BET change in an electrode rolling process.