Graphite-Silicon Anode Particles With Low Chromaticity b*
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Solution Overview
Problem
Existing negative electrode materials for secondary batteries, such as those described in Patent Literatures 1 to 3, have high chromaticity b* values due to large particle size and exposed silicon, leading to insufficient battery characteristics in lithium-ion secondary batteries.
Innovation Solution
The use of particles with a chromaticity b* of 2.0 or less, comprising graphite (A) and silicon-containing particles (B) with specific physical properties, such as a d50 of 0.3 μm or more and SiOx in the range of 0.5 to 1.5, which are mixed and subjected to spheroidization treatment to enhance their compositeness and reactivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If particles with large particle size and exposed silicon are used (as in Patent Literatures 1-3), then the manufacturing process is simpler, but the chromaticity b* value increases leading to insufficient battery characteristics
Solution Approach 1:
The invention changes the particle size parameter (reducing to d50 of 0.3 μm or more) and compositional parameters (controlling SiOx ratio of 0.5 to 1.5) to achieve chromaticity b* of 2.0 or less, thereby improving battery characteristics while maintaining manufacturing feasibility
Solution Approach 2:
The invention uses composite particles comprising graphite (A) and silicon-containing particles (B) with specific properties, creating a composite material that achieves both good battery characteristics and acceptable manufacturing conditions
2Quantity of substance
If silicon-containing particles with high exposed silicon content are used, then the capacity increases, but the reactivity with electrolyte increases causing deterioration
Solution Approach 1:
The invention optimizes the SiOx ratio parameter to 0.5 to 1.5 and controls particle size at d50 of 0.3 μm or more, which reduces the harmful reactivity with electrolyte while maintaining high capacity through controlled silicon content
Solution Approach 2:
The invention creates particles with non-uniform structure where silicon-containing particles are distributed within graphite matrix, providing different local properties: graphite provides stability and low reactivity, while silicon provides high capacity
Data Source
AI summary
Particles may have a chromaticity b* of 2.0 or less. Such particles may include graphite (A) and particles (B) containing a silicon element. The chromaticity b* of the particles is preferably 0.2 or more and 1.1 or less, and the chromaticity a* of the particles is preferably 0.2 or more and 1.2 or less. A method can manufacture a secondary battery including a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode includes a current collector and a negative electrode active material layer disposed on the current collector, and the negative electrode active material layer contains such graphite.