Negative Electrode Particle Structure to Limit Si Battery Expansion
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries face expansion issues in their negative electrode active material layers due to internal stress generated during charging and discharging, particularly when graphite and Si-containing particles are used.
Innovation Solution
A non-aqueous electrolyte secondary battery design incorporating a negative electrode active material layer with first and second graphite particles of varying compressive elastic moduli and Si-containing particles, where the contact length between first graphite particles and Si-containing particles is greater than between second graphite particles, and specific mass and size ratios are maintained to minimize expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Si-containing particles are added to increase capacity, then battery capacity is improved, but negative electrode expansion occurs due to internal stress
Solution Approach 1:
The patent applies local quality by creating distinct regions within the negative electrode active material layer. First graphite particles with smaller particle sizes are positioned closer to Si-containing particles, while second graphite particles with larger particle sizes are positioned farther away. This spatial differentiation of particle properties optimizes stress distribution locally - smaller particles provide better contact and stress absorption near the expanding Si particles, while larger particles provide structural stability in regions less prone to expansion stress.
2Manufacturing precision
If graphite particles with different diameters are used, then electrode structure is optimized, but manufacturing complexity increases
Solution Approach 1:
The patent segments the graphite particle population into two distinct groups based on size: first graphite particles with smaller diameters (0.3-1.5 μm) and second graphite particles with larger diameters (1.5-3.0 μm). This segmentation allows each size group to fulfill specific functional roles - smaller particles for stress absorption and contact optimization near Si particles, and larger particles for structural framework provision. The segmentation is implemented through a two-stage slurry preparation process, which systematically manages the complexity of handling multiple particle sizes.
Solution Approach 2:
The patent extracts the graphite particle population into separate size-based categories rather than using a single uniform size distribution. By separating graphite particles into first and second groups with distinct size ranges, the invention enables independent optimization of each group's properties and positions them strategically within the electrode structure. This extraction approach simplifies the manufacturing process by treating each size group as a distinct component with specific placement requirements.
Data Source
AI summary
A non-aqueous electrolyte secondary battery includes a negative electrode active material layer including a negative electrode active material. The negative electrode active material includes first graphite particles, second graphite particles each having a compressive elastic modulus more than a compressive elastic modulus of each of the first graphite particles, and Si-containing particles. A contact length Lt1 between a first graphite particle and a Si-containing particle is equal to or more than a contact length Lt2 between a second graphite particle and the Si-containing particle.