Cobalt-Coated High-Nickel Cathode Material for Crack-Resistant Output
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Solution Overview
Problem
High-nickel positive electrode active materials in lithium secondary batteries face issues with structural stability and lifespan due to volume expansion-contraction, leading to cracks and increased resistance, especially when used in the form of single or pseudo-single particles, which affects capacity and output performance.
Innovation Solution
A high-nickel positive electrode active material in the form of a single or pseudo-single particle with a specific relationship between the average particle diameter, D50, and cobalt content in the coating layer, optimized to minimize surface resistance and crack generation, is developed, ensuring stable crystal structure and improved lifespan and output properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-nickel positive electrode active material (Ni content ≥80 at%) is used to increase battery capacity, then capacity is improved, but structural stability is reduced leading to crack generation and lifespan degradation
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the inner core region contains high-nickel content (≥80 at%) for high capacity, while the outer shell region has reduced nickel content and increased cobalt content (≥5 at%) for structural stability. This spatial differentiation of composition allows simultaneous achievement of high capacity and long lifespan by assigning different functional qualities to different regions of the same particle.
Solution Approach 2:
The patent employs composite materials by combining nickel-based lithium composite metal oxide with cobalt-containing compounds to form a multi-phase composite structure. The composite consists of a high-nickel core phase for capacity and a cobalt-enriched shell phase for stability, creating a synergistic material system that overcomes the limitations of pure high-nickel materials.
2Reliability
If single particle or pseudo-single particle form is used, then particle strength is improved reducing cracks, but contact interface with electrolyte is reduced leading to longer lithium ion diffusion path and poor output performance
Solution Approach 1:
The patent applies segmentation by dividing the single/pseudo-single particle into multiple nodules (2-50 nodules per particle) with specific size distributions. This internal segmentation increases the surface area and contact interface with electrolyte while maintaining the overall particle integrity and strength, thereby improving both output performance and lithium ion diffusion without sacrificing particle strength.
Solution Approach 2:
The patent utilizes dimensionality change by controlling the three-dimensional arrangement and size distribution of nodules within the particle. By optimizing the spatial configuration of nodules in different dimensions, the patent increases the effective surface area and electrolyte contact interface while maintaining the pseudo-single particle structure, thus improving output performance without compromising particle strength.
3Power
If bimodal positive electrode active material (mixing small-diameter particles and secondary particles) is used to compensate single particle problems, then output performance is improved, but breakage of weak secondary particles increases leading to more side reactions with electrolyte
Solution Approach 1:
The patent applies local quality by creating a size-distributed nodule structure within each particle, where smaller nodules provide high surface area for output performance and larger nodule aggregates provide structural strength. This internal size differentiation eliminates the need for mixing separate small and large particles, avoiding the breakage issue while maintaining high output performance and reducing side reactions.
Data Source
AI summary
A positive electrode active material includes a nickel-based lithium composite metal oxide having a Ni content of 80 atm % or greater among transition metals except lithium, and in the form of a single particle or pseudo-single particle. The nickel-based lithium composite metal oxide has a coating layer positioned on the surface thereof, wherein the coating layer contains cobalt. The positive electrode active material also satisfies [Equation 1] 1≤XY/Z≤3, wherein X is the molar number (mol %) of Co in the coating layer based on 100 moles of the nickel-based lithium composite metal oxide, Y is the average particle diameter (μm) of nodules of the nickel-based lithium composite metal oxide, and Z is D50 (μm) of the positive electrode active material, wherein Z is from 5 μm to 12 μm.