Carbon-Coated Silicon Anode Particles for Low-Swelling Li Batteries
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in achieving high capacity per volume and reducing volume expansion of the negative electrode during charge and discharge, particularly with silicon-based composite materials.
Innovation Solution
A negative active material for lithium batteries is developed, comprising composite crystalline carbon particles, composite crystalline carbon-silicon particles, and composite silicon particles, each with a specific amorphous carbon coating layer and controlled convexity and circularity, enhancing adhesion to the current collector and reducing volume expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based composite materials are used in the negative electrode to achieve high capacity per volume, then the battery capacity increases, but the volume expansion of the negative electrode during charge and discharge worsens
Solution Approach 1:
The negative electrode is divided into multiple particles with different shapes (spherical particles with diameter 3-10 μm and flake-shaped particles with lateral size 5-15 μm and thickness 1-3 μm). This segmentation allows each particle type to contribute differently: spherical particles provide good volume expansion resistance while flake-shaped particles provide high capacity, resolving the contradiction between capacity and volume expansion.
Solution Approach 2:
Different regions of the negative electrode use particles with different properties. Spherical particles (3-10 μm diameter) are used where volume stability is critical, while flake-shaped particles (5-15 μm lateral size, 1-3 μm thickness) are used where capacity density is prioritized. This local differentiation allows the electrode as a whole to achieve both high capacity and controlled volume expansion.
2Quantity of substance
If high specific capacity of the negative electrode is pursued to meet high capacity battery requirements, then the battery performance improves, but the adhesion of the negative electrode to the current collector deteriorates
Solution Approach 1:
The negative electrode uses particles with specifically controlled local geometric properties: spherical particles with diameter 3-10 μm and flake-shaped particles with lateral size 1.5-5.0 times the thickness (1-3 μm thickness). These controlled local geometries optimize both the specific capacity and the adhesion properties, allowing high specific capacity while maintaining good adhesion to the current collector.
Data Source
AI summary
A negative active material for a rechargeable lithium battery includes at least one particle selected from a composite crystalline carbon particle (A) including a crystalline carbon core and an amorphous carbon coating layer surrounding the crystalline carbon core; a composite crystalline carbon-silicon particle (B) including a mixed core of a crystalline carbon and silicon and an amorphous carbon coating layer surrounding the mixed core; and a composite silicon particle (C) including a silicon core and an amorphous carbon coating layer surrounding the silicon core, wherein the at least one particle has convexity in a range of about 0.85 to about 0.97 and circularity in a range of about 0.74 to about 0.90.