Porous Si/C Composite Electrodes from Methane Pyrolysis Carbon
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Solution Overview
Problem
The existing methods for producing hydrogen from methane through pyrolysis using a catalyst result in carbon products contaminated with impurities, which are not suitable for high-value applications, and there is a need for improved electrode materials that combine the conductivity of carbon with the high capacity of silicon while addressing volume changes and conductivity issues in lithium-ion batteries.
Innovation Solution
A silicon-carbon (Si/C) composite is prepared by removing iron impurities from solid carbon produced during methane pyrolysis using an iron-based catalyst, forming a porous carbon material with increased micropore, mesopore, and macropore volumes, and then attaching silicon to this material, which is used as an electrode material in batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon is used as electrode material, then conductivity is improved, but capacity is insufficient
Solution Approach 1:
The patent creates a Si/C composite electrode material where silicon particles are embedded in a carbon matrix. This composite structure combines the high conductivity of carbon with the high theoretical capacity of silicon (4200 mAh/g), achieving both electrical performance and high capacity in the same electrode material system.
2Quantity of substance
If silicon is used to replace carbon, then capacity is improved, but volume change and conductivity are worsened
Solution Approach 1:
The patent uses a carbon matrix as a flexible constraint structure that accommodates silicon's volume expansion during lithiation. The carbon shell/thin film structure allows volume change while maintaining structural integrity and preventing electrode disintegration, thus stabilizing the composite electrode during cycling.
Solution Approach 2:
The carbon matrix acts as an intermediary between silicon particles and the electrolyte, providing a conductive network that maintains electrical connectivity even when silicon expands. The carbon phase mediates the mechanical stress and volume change, protecting the silicon from direct contact with electrolyte that would cause decomposition.
3Productivity
If iron-based catalyst is used for methane pyrolysis, then hydrogen production is improved, but carbon product contains impurities
Solution Approach 1:
The patent applies heat treatment at high temperature (1600-3000°C) to change the physical and chemical parameters of the carbon material. This thermal processing removes iron impurities from the carbon product through evaporation and oxidation, transforming the impure catalytic carbon into high-purity porous carbon suitable for electrode applications.
Solution Approach 2:
The patent discards the iron catalyst impurities through heat treatment while recovering and utilizing the carbon structure formed during methane pyrolysis. The iron impurities are removed via evaporation and oxidation, leaving behind the valuable porous carbon framework that is then used as electrode material after silicon incorporation.
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 resulting Si/C composite exhibits enhanced electrode performance, including improved charging and discharging capacities and initial coulombic efficiency, comparable to commercial electrode materials, while utilizing low-cost carbon by-products from hydrogen production, thus offering economic feasibility and high-value application potential.
Implementation Method 1
a process has been developed to produce hydrogen from methane through pyrolysis using a catalyst, for example, a ferric oxide (Fe2O3) catalyst
Implementation Method 2
removing iron impurities from the solid iron-containing carbon by heat treatment to form a porous carbon-based material
Data Source
Figure 1
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Figure 3A~3C
AI summary
The present invention relates to a silicon-carbon (Si/C) composite that is prepared by combining silicon with a porous carbon-based material, which is obtained by removing iron impurities from solid carbon produced during pyrolysis for converting a methane-containing feedstock into hydrogen in the presence of an iron-based catalyst. The present invention further relates to a method for making the silicon-carbon (Si/C) composite and a use thereof as electrode material.