Composite Battery Electrode Particles for Filling Density
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Solution Overview
Problem
Existing lithium-ion secondary batteries face challenges in achieving high energy density and capacity retention due to large specific surface areas and aggregation of particles, which lead to decreased filling properties and discharging capacity.
Innovation Solution
The use of composite particles where first particles are coated with second particles, with a specific circularity and particle diameter ratio, to improve filling rates and prevent cracking, thereby enhancing discharging capacity and capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If primary particles with uniform particle size are used to improve filling properties, then filling properties are improved, but specific surface area increases and capacity retention decreases
Solution Approach 1:
The invention divides particles into two size categories: primary particles (1-10 μm) for good filling properties and secondary particles (0.1-1 μm) for high specific surface area. By segmenting the particle size distribution rather than using uniform particles, the patent achieves both good filling properties and high capacity retention, resolving the technical contradiction between these two parameters.
Solution Approach 2:
The patent applies different particle sizes to different functional requirements: larger primary particles (1-10 μm) are used where filling density is important, while smaller secondary particles (0.1-1 μm) are used where high specific surface area is needed for electrochemical performance. This local quality differentiation allows simultaneous optimization of both filling properties and capacity retention.
2Reliability
If a grinding step is added for granulation to improve battery characteristics, then battery characteristics are improved, but productivity decreases
Solution Approach 1:
The patent performs preliminary granulation during the synthesis process itself, rather than adding a separate grinding step after synthesis. By incorporating granulation into the formation process, the patent achieves good battery characteristics without the time loss of an additional processing step, thus maintaining high productivity while improving battery performance.
3Quantity of substance
If fine particles are aggregated on the peripheries of core particles to increase energy density, then energy density is improved, but filling properties are not improved and discharging capacity decreases
Solution Approach 1:
The patent changes the particle size parameters to resolve this contradiction. By using primary particles of 1-10 μm with appropriate size distribution rather than smaller core particles, the patent achieves both high energy density (through optimized particle packing) and good filling properties. The specific parameter optimization allows simultaneous improvement of both parameters.
4Manufacturing precision
If particle aggregates are used to improve filling properties, then filling properties are improved, but specific surface area increases and capacity retention decreases
Solution Approach 1:
The patent segments particles into primary particles (1-10 μm) that form the aggregate structure for good filling properties, and secondary particles (0.1-1 μm) that provide high specific surface area. This segmentation allows the aggregate to have both good packing characteristics and sufficient surface area for high capacity retention, resolving the technical contradiction.
Solution Approach 2:
The patent creates a composite particle structure combining primary particles and secondary particles with different size characteristics. This composite structure allows the aggregate to simultaneously achieve good filling properties (from the primary particle framework) and high capacity retention (from the secondary particle surface area), resolving the contradiction between these two parameters.
Data Source
AI summary
An active material for a nonaqueous electrolyte secondary battery includes first particles and second particles provided to coat the first particles so as to be scattered on the surfaces of the first particles. The circularity of the first particles coated with the second particles is 0.800 to 0.950, and the ratio r1/r2 of the average particle diameter r1 of the second particles to the average particle diameter r2 of the first particles is 1/20 to 1/2.