Rock-Salt Cathode Particle Shape for Lower Polarization
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Solution Overview
Problem
Existing lithium-metal composite oxides with a rock-salt structure have limited capacity improvement despite efforts to enhance them, primarily due to uneven particle shapes and high tortuosity of electron conduction paths, leading to uneven charge-discharge reactions and increased polarization.
Innovation Solution
Control the average roundness and aspect ratio of lithium-metal composite oxide particles to 0.55 or more and less than 2.10, respectively, to promote uniform charge-discharge reactions and reduce polarization, thereby increasing discharge capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium-metal composite oxide with rock-salt structure is used to achieve high capacity, then energy density is improved, but particle shape uniformity deteriorates leading to uneven charge-discharge reactions
Solution Approach 1:
The patent applies parameter changes by controlling the average roundness of particles to 0.55 or more and aspect ratio to less than 2.10. This specific parameter control transforms the particle morphology to achieve both high capacity and uniform charge-discharge reactions, resolving the contradiction between quantity of substance and reaction uniformity.
Solution Approach 2:
The patent utilizes spheroidality by specifying that particles should have an average roundness of 0.55 or more. This curvature control makes particles more spherical, which reduces tortuosity of electron conduction paths and promotes uniform charge-discharge reactions across the particle surfaces, thereby maintaining reaction stability while achieving high capacity.
2Ease of manufacture
If particle shape is not controlled, then manufacturing is simpler, but electron conduction path tortuosity increases leading to polarization
Solution Approach 1:
The patent applies parameter changes by defining specific ranges for average roundness (0.55 or more) and aspect ratio (less than 2.10). These parameter specifications provide clear manufacturing targets that balance ease of production with performance requirements, reducing polarization while maintaining manufacturability.
3Quantity of substance
If high capacity materials are used, then energy density is improved, but particle shape uniformity deteriorates leading to increased polarization
Solution Approach 1:
The patent resolves this contradiction by implementing specific parameter changes: controlling average roundness to 0.55 or more and aspect ratio to less than 2.10. These parameter controls ensure that high-capacity lithium-metal composite oxide particles maintain uniform shapes, which reduces tortuosity of electron conduction paths and minimizes polarization losses while preserving high discharge capacity.
Solution Approach 2:
The patent applies spheroidality by requiring particles to have an average roundness of 0.55 or more. This spherical morphology reduces the tortuosity of electron conduction paths within and between particles, enabling efficient electron transport that reduces polarization. Simultaneously, the controlled spheroidal shape maintains high surface area for electrochemical reactions, preserving high discharge capacity.
Data Source
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AI summary
A positive electrode active material for secondary batteries contains a lithium-metal composite oxide having a rock-salt type crystal structure assignable to space group Fm-3m. The lithium-metal composite oxide contains at least Li and Mn. The average roundness of particles of the lithium-metal composite oxide is 0.55 or more.