Silicon-Carbon Anode Composition for Capacity-Stability Balance
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Solution Overview
Problem
Silicon-based negative electrode materials exhibit a large volume expansion rate and poor cycle stability during the charge-discharge process, leading to reduced battery cycle performance.
Innovation Solution
A silicon-carbon composite material is developed, comprising two types of silicon-carbon composite particles with different silicon contents and carbon matrices, where the first particle has a higher silicon content for higher gram capacity and the second particle has a lower silicon content for improved cycle stability, along with specific pore structures and surface areas to manage volume changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative electrode materials are used to achieve high specific capacity, then gram capacity is improved, but volume expansion rate increases and cycle stability deteriorates
Solution Approach 1:
The patent applies local quality by creating a non-uniform silicon content distribution within the composite particles. The surface region has lower silicon content (first silicon-containing compound) while the interior maintains higher silicon content (second silicon-containing compound). This spatial variation in composition allows the surface to provide structural stability during cycling while the interior delivers high capacity through silicon's lithium alloying reactions.
Solution Approach 2:
The patent employs composite materials by combining silicon-containing compounds with carbon material to form a composite particle structure. The carbon component provides dimensional stability and electrical conductivity, while the silicon components deliver high capacity. The composite structure mitigates silicon's volume expansion by confining it within the carbon matrix, thereby improving cycle stability while maintaining high gram capacity.
2Quantity of substance
If silicon content is increased to improve gram capacity, then energy density is improved, but volume expansion rate increases leading to poor cycle performance
Solution Approach 1:
The patent implements local quality through a core-shell like structure where the surface layer (first silicon-containing compound) has optimized silicon content for stability, while the core (second silicon-containing compound) has high silicon content for energy density. This local differentiation allows the material to achieve both high energy density from the silicon-rich core and good cycle performance from the silicon-poor surface layer that experiences less volume expansion stress.
Data Source
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AI summary
A negative electrode active material, a secondary battery and an electrical apparatus. The negative electrode active material includes a silicon-carbon composite material, where the silicon-carbon composite material includes a first silicon-carbon composite particle and a second silicon-carbon composite particle; the first silicon-carbon composite particle includes a first carbon matrix having a pore structure and a first silicon-based material arranged in the pore structure of the first carbon matrix; the second silicon-carbon composite particle includes a second carbon matrix having a pore structure and a second silicon-based material arranged in the pore structure of the second carbon matrix; and a mass percentage content of a silicon element in the first silicon-carbon composite particle is greater than a mass percentage content of a silicon element in the second silicon-carbon composite particle. The silicon-carbon negative electrode material has good cycle stability as well as high gram capacity, which can improve an energy density and cycle performance of the battery.