Porous Cathode Active Material Structure for Battery Endurance
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Solution Overview
Problem
Existing positive electrode active materials face challenges in enhancing battery endurance due to stress concentration between crystallites during charge and discharge cycles, leading to detachment and degradation of nascent surfaces.
Innovation Solution
A positive electrode active material with a secondary particle structure featuring radially extending crystallites and open pores between them, optimized by specific geometric relationships and compositions, is developed to mitigate stress and enhance endurance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If long pores reaching inside secondary particles are formed to enhance output properties, then power density is improved, but structural integrity deteriorates leading to reduced battery endurance
Solution Approach 1:
The patent applies porous materials by forming open pores on the surface of secondary particles with controlled pore diameters of 20 nm or more. These surface pores provide adequate pathways for electrolyte penetration and lithium ion transport to enhance output properties, while avoiding the formation of long internal pores that would compromise structural integrity and lead to crystallite detachment during charge-discharge cycles.
Solution Approach 2:
The patent implements local quality by creating a differentiated pore structure where open pores are concentrated on the particle surface rather than extending deeply inside. This localized porosity optimizes electrolyte access and ion transport at the surface level while maintaining dense, structurally sound interiors that prevent stress concentration and crystallite detachment, thereby resolving the contradiction between power output and battery endurance.
2Quantity of substance
If crystallites are densely packed to improve capacity, then energy density is enhanced, but stress concentration increases causing crystallite detachment
Solution Approach 1:
The patent introduces surface open pores with diameters of 20 nm or more that act as stress relief zones. These pores are strategically positioned on the particle surface to provide expansion space during charge-discharge cycles, reducing stress concentration between densely packed crystallites and preventing detachment while maintaining high capacity.
Solution Approach 2:
The patent applies beforehand cushioning by pre-forming open pores on the particle surface before battery operation. These pores serve as predetermined stress absorption zones that accommodate volume changes of crystallites during lithium insertion and extraction, preventing stress concentration and crystallite detachment from the outset while maintaining dense packing for high capacity.
Data Source
AI summary
A positive electrode active material comprises a secondary particle. The secondary particle includes crystallites. The crystallites extend radially from a center of the secondary particle toward outside. Each of the crystallites includes a lithium-metal composite oxide. The lithium-metal composite oxide has a lamellar-rock-salt-type structure. In a surface of the secondary particle, an open pore is formed between the crystallites that are adjacent to each other. The open pore has a pore diameter of 20 nm or more.