Graphitic Negative Electrode Material for Li-Ion Batteries
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Solution Overview
Problem
Existing lithium-ion secondary battery negative electrode materials fail to provide excellent pulse charge characteristics, cycle characteristics, and storage characteristics, particularly when using graphitic particles with high aspect ratios, which are not effective for pulse charging.
Innovation Solution
A negative electrode material comprising graphitic particles with a standard deviation of degree of circularity between 0.05 and 0.10 and carbon particles with an average degree of circularity of 0.94 or less, along with specific particle size and mass ratios, is used to enhance pulse charge, cycle, and storage characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If graphitic particles with high aspect ratio are used, then continuous rapid input characteristics are improved, but pulse charge characteristics deteriorate
Solution Approach 1:
The invention changes the shape parameter of graphitic particles from high aspect ratio to substantially spherical shape (degree of circularity 0.92 or more), which fundamentally alters the particle morphology to achieve both rapid input and excellent pulse charge characteristics simultaneously
Solution Approach 2:
The invention creates a composite negative electrode material comprising substantially spherical graphitic particles and amorphous carbon particles, where the amorphous carbon particles fill interstices and provide additional lithium ion insertion sites, enhancing both continuous rapid input and pulse charge characteristics
2Quantity of substance
If graphitic particles with high degree of circularity are used, then capacity is improved, but irreversible capacity increases
Solution Approach 1:
The invention combines substantially spherical graphitic particles (high degree of circularity) with amorphous carbon particles, where the amorphous carbon component reduces irreversible capacity through its unique structure that facilitates smoother lithium ion insertion and extraction, while the spherical graphite particles maintain high capacity
3Manufacturing precision
If graphitic particles with narrow size distribution are used, then manufacturing precision is improved, but charge-discharge characteristics deteriorate
Solution Approach 1:
The invention uses a composite of substantially spherical graphitic particles with controlled size distribution and amorphous carbon particles with different size characteristics, where the size distribution of graphitic particles is controlled at 0.03 or less for manufacturing precision, while the composite structure maintains excellent charge-discharge characteristics
Data Source
AI summary
A negative electrode material for a lithium-ion secondary battery includes: graphitic particles having a standard deviation of degree of circularity of from 0.05 to 0.10 in a range in which a cumulative frequency of degree of circularity from a lower degree of circularity is from 10% by particle to 90% by particle in a cumulative frequency distribution with respect to a degree of circularity obtained using a flow-type particle analyzer; and carbon particles having an average degree of circularity of 0.94 or less, the average degree of circularity being obtained using a flow-type particle analyzer.