Multi-Layer Silicon-Carbon Anode Structure for Stable High Capacity
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Solution Overview
Problem
Conventional graphite anode materials in lithium-ion batteries have a limited theoretical specific capacity, and silicon-based negative electrodes face significant volume variation, which impedes their practical implementation due to challenges in achieving a uniformly dispersed silicon-carbon blend.
Innovation Solution
A multi-layer composite material comprising a carbon matrix, nano silicon-based composite material, and a carbon shell, prepared through vapor deposition and coating processes, forms amorphous Si—C and Si—N bonds, with boron and phosphor doping to stabilize the structure and enhance electrochemical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative electrodes are used to increase theoretical capacity, then energy density is improved, but volume expansion of 300%-400% occurs during cycling
Solution Approach 1:
The patent embeds silicon particles within a carbon matrix structure, creating a nested configuration where silicon is contained inside carbon. This nested design allows silicon to expand and contract within the confines of the carbon matrix, accommodating the 300%-400% volume expansion without compromising the overall structural integrity of the electrode material.
Solution Approach 2:
The patent creates a composite material system combining silicon and carbon, where each component compensates for the other's deficiencies. Silicon provides high theoretical capacity while carbon provides structural stability and conductivity. The composite structure enables silicon to maintain its high capacity advantage while the carbon framework constrains volume expansion and ensures electrical conductivity.
2Ease of manufacture
If physical mixing method is used to incorporate carbon materials, then ease of manufacture is improved, but uniform dispersion of silicon-carbon blend cannot be achieved
Solution Approach 1:
The patent replaces the mechanical mixing process with a chemical vapor deposition process. Instead of physically mixing silicon and carbon powders, the invention uses chemical reactions to deposit carbon atoms directly onto silicon particles, forming a uniform carbon matrix. This substitution of mechanical mixing with a chemical deposition process ensures homogeneous distribution of carbon throughout the silicon structure.
Solution Approach 2:
The patent introduces gaseous compounds as intermediaries in the synthesis process. These gaseous precursors serve as mediators that deposit carbon atoms uniformly onto silicon particles during the vapor deposition process, ensuring homogeneous distribution without the need for mechanical mixing. The gaseous intermediaries enable controlled and uniform carbon deposition throughout the silicon-carbon composite.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The composite material exhibits reduced volume expansion, improved cycle performance, and enhanced rate capability by stabilizing the silicon structure and facilitating lithium ion intercalation and deintercalation.
Implementation Method 1
the nano silicon-based composite material is prepared by means of vapor deposition of silane and one or more of gaseous compounds containing any one of C, N, B and P elements
Implementation Method 2
the carbon shell coats the outer layer of the carbon matrix on which the nano silicon-based composite material is deposited
Data Source
AI summary
A multi-layer composite material comprises a carbon matrix, a nano silicon-based composite material, and a carbon shell. The carbon matrix is a matrix material used for depositing the nano silicon-based composite material. The nano silicon-based composite material is prepared by vapor deposition of silane and one or more gaseous compounds containing any one of C, N, B and P elements. Carbon atoms in the nano silicon-based composite material are uniformly embedded and distributed in an atomic scale, and the carbon atoms and silicon atoms are combined to form amorphous Si—C bonds. Nitrogen atoms and the silicon atoms are combined to form amorphous Si—N bonds. Boron doping and/or phosphor doping forms defects in silicon crystals in the nano silicon-based composite material. The carbon shell coats the outer layer of the carbon matrix on which the nano silicon-based composite material is deposited.