Porous Silicon Composition Using Surface Al Diffusion for Cycle Stability
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Solution Overview
Problem
Existing methods for manufacturing porous silicon materials are inadequate in addressing the expansion and contraction issues of silicon during charge and discharge cycles, and require high-temperature processing, which complicates the manufacturing process and does not effectively enhance electrochemical characteristics.
Innovation Solution
A method involving the preparation of a silicon alloy with a high Al content, followed by particle formation, pore formation through acid treatment, and heat treatment to diffuse Al to the surface, resulting in a porous silicon material with improved electrochemical characteristics, specifically designed for use in power storage devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-temperature melting and substitution treatment is used to manufacture porous silicon material, then the porous structure can be formed, but the manufacturing process becomes complex and requires high equipment requirements
Solution Approach 1:
The invention changes the manufacturing parameters from high-temperature melting (above 1000°C) to low-temperature processes (room temperature to 600°C). Specifically, it uses mechanical alloying at room temperature to create Si-Al alloys, followed by selective Al dissolution at low temperatures to form porous silicon, thereby avoiding complex high-temperature equipment while achieving the desired porous structure
Solution Approach 2:
The invention replaces the thermal field (high-temperature melting and substitution) with a chemical field (selective dissolution of Al from Si-Al alloy). Instead of using heat to separate elements, the process uses chemical reagents to selectively dissolve Al, leaving behind a porous silicon structure. This substitution simplifies the manufacturing process and reduces equipment requirements
2Manufacturing precision
If Si content in alloy is increased to 50% or more, then porous silicon can be formed, but the effectiveness in reducing expansion and contraction problems is insufficient
Solution Approach 1:
The invention uses partial action by not completely dissolving Al from the Si-Al alloy. Instead of removing all Al, it retains controlled amounts (0.1-10 wt%) that are sufficient to enhance electrochemical characteristics while the porous structure formed by selective dissolution continues to effectively suppress volume expansion. This partial removal strategy optimizes both structural integrity and electrochemical performance
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 method significantly improves the electrochemical characteristics of the porous silicon material, enhancing charge and discharge cycle performance and energy density by mitigating volume expansion and contraction, leading to a high-performance power storage device.
Implementation Method 1
a heat treatment step of heating the porous material to diffuse elements other than Si to a surface of the porous material
Data Source
AI summary
The manufacturing method of a porous silicon material of the present disclosure includes a particle forming step of melting a raw material containing Al as a first element in an amount of 50% by mass or more and Si in an amount of 50% by mass or less to obtain a silicon alloy, a pore forming step of removing the first element from the silicon alloy to obtain a porous material, and a heat treatment step of heating the porous material to diffuse elements other than Si to a surface of the porous material.