Negative Electrode Particle Sphericity for Energy Density and Dynamics
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Solution Overview
Problem
Current secondary batteries face a challenge in balancing the compaction density and dynamic performance of negative electrode sheets, as increasing compaction density to enhance energy density leads to a loss of dynamics, and irregularly shaped particles with surface defects affect cycling performance.
Innovation Solution
A negative electrode sheet with a specific ratio of equivalent average spherical diameter (R50) to median particle diameter (Dv50) of 0.7≤R50/Dv50≤0.95 is used, ensuring a balance between energy density and dynamic performance by controlling the regularity of negative active particles, which are typically carbon-based, silicon-based, or metallic inorganic materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the compaction density of the negative electrode sheet is increased to enhance energy density, then the energy density is improved, but the dynamic performance is lost
Solution Approach 1:
The invention changes the particle size distribution parameters by controlling the ratio of equivalent average spherical diameter to median particle diameter within 0.85≤R50/Dv50≤0.95. This parameter optimization enables the negative electrode sheet to achieve both high compaction density (improving energy density) and good dynamic performance, resolving the contradiction between these two properties
Solution Approach 2:
The invention uses a composite particle size distribution strategy, combining different sized particles with specific size ratios. This composite approach allows small particles to fill voids between larger particles, achieving high compaction density while maintaining sufficient porosity for electrolyte penetration and ion transport, thus balancing energy density and dynamic performance
2Quantity of substance
If irregularly shaped particles with surface defects are used, then the compaction density may be improved, but the cycling performance deteriorates
Solution Approach 1:
The invention optimizes the particle shape parameter by controlling the sphericity ratio R50/Dv50 within a specific range. This parameter control ensures particles are sufficiently spherical to provide good cycling performance and stable solid electrolyte interface (SEI) formation, while still achieving high compaction density through optimized size distribution
Solution Approach 2:
The invention applies different particle characteristics to different size segments. By controlling the overall size distribution and sphericity ratio, it ensures that particles have the appropriate local properties (sphericity and size) to simultaneously achieve high compaction density and excellent cycling performance through stable SEI formation
Data Source
AI summary
A negative electrode sheet and a screening method thereof, a battery and an electric equipment are provided. The negative electrode sheet comprises a current collector and a negative active material layer arranged on the current collector. The negative active material layer has negative active particles, and each negative active particle satisfy the relation: 0.7≤R50/Dv50≤0.95; R50 is an equivalent average spherical diameter of the negative active particles, and Dv50 is a corresponding particle diameter when a cumulative volume fraction in a volume-based distribution reaches 50% in the particle diameter distribution measurement by a laser scattering method.