Silicon-Carbon Anode Composite for Stable Water-Based Processing
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Solution Overview
Problem
Existing lithium secondary batteries face challenges in achieving high capacity, efficiency, and stability, particularly with silicon-based active materials, due to limitations in water-based processability and gas generation during manufacturing.
Innovation Solution
A silicon carbon composite is developed with a specific intensity ratio of peaks in the 29Si-MAS-NMR spectrum, incorporating carbon in a specific weight range and forming a carbon layer on silicon particles, enhancing capacity and efficiency while reducing gas generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based active materials are used to increase capacity, then battery capacity and efficiency are improved, but gas generation increases during water-based processing
Solution Approach 1:
A water-based dispersant containing a specific surfactant is introduced as an intermediary substance during the mixing process. The surfactant molecules adsorb onto the silicon particle surfaces, forming a protective interface that prevents water from reacting with silicon to generate gas, while still allowing the mixture to maintain appropriate viscosity for electrode fabrication.
Solution Approach 2:
The pH value of the water-based mixture is controlled within a specific range (6.5-7.5) to minimize gas generation. By adjusting this chemical parameter, the reactivity between water and silicon is reduced, thereby suppressing gas formation while preserving the high capacity benefits of silicon-based materials.
2Quantity of substance
If silicon-based active materials are used to increase capacity, then battery capacity is improved, but water-based processability deteriorates
Solution Approach 1:
A water-based dispersant containing a specific surfactant is introduced as an intermediary substance during the mixing process. The surfactant molecules adsorb onto the silicon particle surfaces, forming a protective interface that prevents water from reacting with silicon to generate gas, while still allowing the mixture to maintain appropriate viscosity for electrode fabrication.
Solution Approach 2:
The pH value of the water-based mixture is controlled within a specific range (6.5-7.5) to minimize gas generation. By adjusting this chemical parameter, the reactivity between water and silicon is reduced, thereby suppressing gas formation while preserving the high capacity benefits of silicon-based materials.
3Productivity
If silicon-based active materials are used to improve efficiency, then battery efficiency is improved, but life characteristics deteriorate
Solution Approach 1:
The negative electrode is designed as a composite structure combining silicon-based active material particles with carbon-based material. This composite approach leverages the high capacity of silicon while the carbon component provides structural stability and conductivity, thereby improving both efficiency and life characteristics simultaneously.
Solution Approach 2:
The silicon-based active material is distributed uniformly throughout the negative electrode matrix at a controlled content of 5-20 wt%. This localized distribution ensures that the high-efficiency regions (silicon particles) are optimally positioned within the stable carbon matrix, maximizing efficiency while maintaining structural integrity for long cycle life.
Data Source
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AI summary
The present invention relates to a silicon carbon composite, a negative electrode active material comprising same, a negative electrode composition, a negative electrode, a lithium secondary battery, a battery module, and a battery pack, the silicon carbon composite having, in a 29Si-MAS-NMR spectrum, a peak A within a chemical shift value range of 20 ppm to -15 ppm, a peak B within a chemical shift value range of -20 ppm to -100 ppm, and, in a 29Si-MAS-NMR spectrum, a peak C within a chemical shift value range of -110 ppm to -140 ppm.