Porous Lithium Metal Composite Oxide for High-Rate Cathodes
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Solution Overview
Problem
There is a demand for lithium secondary batteries to improve further in terms of initial discharge capacity and rate performance.
Innovation Solution
A lithium metal composite oxide is developed with specific void characteristics, including secondary particles that have voids with controlled aspect ratios and distributions, and a composition of Li, Ni, and optionally Co and Mn, to enhance the performance of lithium secondary batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the pore structure of lithium metal composite oxide is optimized to improve output, then the battery output is improved, but the initial discharge capacity and rate performance are insufficient
Solution Approach 1:
The invention changes the geometric parameters of voids within secondary particles, specifically controlling the aspect ratio to 1.8-5.0 and the equivalent circle diameter to 0.2-0.5 μm. These parameter changes optimize both the initial discharge capacity and rate performance while maintaining high battery output, resolving the contradiction between power and reliability.
2Quantity of substance
If the void size and distribution in secondary particles are increased to improve capacity, then the initial discharge capacity is improved, but the rate performance deteriorates
Solution Approach 1:
The invention optimizes the size parameter (equivalent circle diameter of 0.2-0.5 μm) and distribution parameters (aspect ratio of 1.8-5.0, ratio of secondary particles with voids of 3-95%) of voids within secondary particles. This dual optimization of size and distribution enables both high initial discharge capacity and high rate performance to be achieved simultaneously.
3Quantity of substance
If the particle packing density is increased to improve capacity, then the quantity of active material is improved, but the lithium ion diffusion and electron conduction are hindered
Solution Approach 1:
The invention introduces a controlled porous structure within secondary particles, where voids with specific aspect ratios (1.8-5.0) and sizes (0.2-0.5 μm equivalent circle diameter) create internal pathways for lithium ion diffusion and electron conduction. This porous structure allows high particle packing density to be maintained while ensuring efficient ion and electron transport, resolving the contradiction between capacity and conductivity.
Data Source
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Figure 3
AI summary
The present invention relates to a lithium metal composite oxide comprising a plurality of secondary particles which are aggregates of primary particles, wherein: at least a part of the secondary particles have voids therein; with respect to outline shape of the voids exposed in cross-sections of the secondary particles having voids therein, an area-weighted average aspect ratio of the voids with an equivalent circle diameter of 0.2 µm or more is 1.8 or more and 5.0 or less; and a ratio of number of the secondary particles having the voids with an equivalent circle diameter of 0.5 µm or more to total number of the secondary particles is 3 % or more and 95 % or less.