Graphite Negative Electrode Material for Fast Charging and Cycle Life
Solution Overview
Problem
Lithium ion secondary batteries face challenges in achieving quick charging characteristics and cycle characteristics, with existing materials not adequately addressing the need for improved performance in both areas.
Innovation Solution
A negative electrode material comprising aggregated or bonded flat graphite particles with specific surface area and graphitization degree optimizations, including a cumulative volume-based particle diameter of 8.0% or less at 9.516 µm, standard deviation of 0.22 or less, and a specific surface area of 3.0 m²/g or less, along with a graphitization degree of 93% or more, to enhance quick charging and cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the specific surface area of graphite particles is increased to improve quick charging performance, then lithium ion insertion/extraction speed improves, but the contact area with electrolyte increases leading to more decomposition reactions and reduced cycle life
Solution Approach 1:
The patent optimizes the specific surface area parameter to a specific range (0.5-6.0 m²/g) to balance quick charging performance and cycle stability. By controlling this physical parameter, the invention achieves both fast lithium ion insertion/extraction and reduced electrolyte decomposition.
Solution Approach 2:
The patent applies different surface treatments to different portions of the graphite particles. The surface layer is modified to reduce reactivity with electrolyte while maintaining internal porosity for fast ion transport, creating local quality differences that resolve the contradiction between speed and reliability.
2Productivity
If the particle size distribution is widened to improve manufacturing efficiency, then production speed increases, but battery performance uniformity deteriorates
Solution Approach 1:
The patent controls the particle size distribution parameters (D50, D10, D90) within specific ranges and maintains the ratio (D90-D10)/D50 below 0.22. This parameter optimization enables efficient manufacturing while ensuring uniform battery performance across production batches.
3Reliability
If the graphitization degree is increased to improve electrical conductivity, then charge acceptance improves, but manufacturing complexity and energy consumption increase
Solution Approach 1:
The patent optimizes the graphitization degree to a specific range (93% or more) rather than pursuing maximum graphitization. This parameter optimization achieves sufficient electrical conductivity for high-performance batteries while avoiding the exponentially increasing manufacturing complexity and energy consumption associated with higher graphitization levels.
Data Source
AI summary
A negative electrode material for a lithium ion secondary battery includes particles in a state in which a plurality of flat graphite particles are aggregated or bonded, and in the negative electrode material, with respect to a volume-based particle diameter measured by a laser diffraction/scattering method, a cumulative value at 9.516 µm is 8.0% or less, a standard deviation of a particle size distribution is 0.22 or less, and a specific surface area is 3.0 m2/g or less.