Porous Cathode Active Material Structure for Lower Battery Resistance
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Solution Overview
Problem
Existing positive electrode active materials in secondary batteries face challenges in reducing battery resistance, particularly due to localized charge/discharge reactions at the surface of secondary particles, which limits the overall performance.
Innovation Solution
The positive electrode active material is designed with a secondary particle structure that includes radially extending crystallites and open pores between them, with specific geometric relationships and compositions to enhance the reaction area and reduce resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If crystallites are densely packed in secondary particle, then structural integrity is improved, but electrolyte penetration and reaction area are reduced
Solution Approach 1:
The patent introduces open pores with diameters of 0.2 μm or more between crystallites in the secondary particle structure. These pores allow electrolyte penetration deep into the particle interior, increasing the reaction area while maintaining structural integrity through the controlled porous architecture.
Solution Approach 2:
The secondary particle is segmented into multiple crystallites with specific radial arrangements. This segmentation creates internal pathways and increases surface area for reactions, allowing electrolyte access to interior regions while maintaining overall particle strength through the organized crystallite structure.
2Stability of the object's composition
If charge/discharge reactions are localized at the surface of secondary particle, then structural stability is improved, but battery resistance is increased
Solution Approach 1:
The patent transitions reactions from surface-only (2D) to interior-accessible (3D) by creating radial pathways through the secondary particle. Crystallites are arranged radially with open pores extending from the surface toward the center, enabling electrolyte penetration and reactions throughout the particle volume, thereby reducing resistance while maintaining stability.
Solution Approach 2:
Different regions of the secondary particle are designed with different properties: the outer region maintains structural stability through dense crystallite packing, while the interior region accessible through radial pores enables enhanced reactions. This local differentiation allows simultaneous optimization of stability and resistance.
3Speed
If open pores with large diameter are formed between crystallites, then electrolyte penetration is improved, but particle density is reduced
Solution Approach 1:
The patent employs a controlled porous structure with open pores of specific diameter (0.2 μm or more) arranged radially between crystallites. This porous architecture enables rapid electrolyte penetration while minimizing volume loss through optimized pore distribution and sizing, balancing penetration speed with particle density.
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 250 nm or more.