Porous Positive Electrode Material for Stable Battery Resistance
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Solution Overview
Problem
The internal resistance of lithium ion secondary batteries using composite oxides as positive electrode active materials fluctuates significantly with changes in the depth of charge, which is undesirable.
Innovation Solution
A positive electrode active material composed of secondary particles with internal voids and specific elemental compositions, produced through a process involving mixing with an activation agent and separation of a slurry into solid and liquid components, to stabilize internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If composite oxide is used as positive electrode active material, then battery capacity is improved, but internal resistance fluctuates significantly with depth of charge
Solution Approach 1:
The patent applies porous materials by introducing voids within secondary particles that aggregate primary particles. These voids create internal pathways for ion transport, reducing resistance fluctuations during charge-discharge cycles while maintaining high capacity. The porous structure allows electrolyte penetration and facilitates lithium ion movement throughout the particle interior.
Solution Approach 2:
The patent segments the positive electrode active material into primary particles that aggregate to form secondary particles. This segmentation creates a hierarchical structure where smaller primary particles provide short ion diffusion paths, while the aggregated secondary particle structure provides mechanical stability and controlled porosity, thereby reducing internal resistance fluctuations.
2Reliability
If elements are added to improve battery characteristics, then performance is enhanced, but manufacturing complexity increases
Solution Approach 1:
The patent uses composite materials by combining multiple elements (Ni, Co, Mn, Fe, Al, P from element group 1 and Li, Na, K, Ca, Sr, Ba, Mg from element group 2) to form a multi-element oxide composite. This composite approach enhances battery characteristics through synergistic effects of different elements while maintaining a relatively simple manufacturing process using conventional solid-state reaction methods.
Data Source
AI summary
Please replace the abstract in the specification as filed with the below paragraph as follows: A positive electrode active material for a lithium secondary battery contains secondary particles in which primary particles are aggregated and satisfies (1) the secondary particles each internally have a plurality of voids, a cumulative frequency of 50% in an area-based cumulative frequency distribution of equivalent circle diameters of the voids based on cross-sectional images of the secondary particles is more than 0.2 μm and 0.65 μm or less, and a cumulative frequency of 50% in an area-based cumulative frequency distribution of circularity of the voids based on cross-sectional images of the secondary particles is 2.2 or more and 6.5 or less; and (2) the primary particles are formed of an oxide containing one or more from the group 1 and one or more from the group 2:group 1: Ni, Co, Mn, Fe, Al, and P; andgroup 2: Li, Na, K, Ca, Sr, Ba, and Mg.