Porous Silicon Material with Al Surface Diffusion for Cycle Stability
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Solution Overview
Problem
Existing manufacturing methods for porous silicon materials are inadequate in reducing the issues of expansion and contraction of silicon during charge and discharge cycles, and require high-temperature processing, which complicates the production process and affects electrochemical characteristics.
Innovation Solution
A manufacturing method involving a silicon alloy with a high Al content, where Al is removed to create a porous structure and then diffused to the surface through heat treatment, resulting in a porous silicon material with improved electrochemical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a silicon alloy with high Al content (50% by mass or more) is used and Al is removed to create porous structure, then the porosity and electrochemical characteristics are improved, but the manufacturing process becomes more complex due to the additional heat treatment step required to diffuse Al to the surface
Solution Approach 1:
The invention applies preliminary action by incorporating Al into the silicon alloy before porous structure formation. The Al is initially mixed with Si to form an alloy, then removed after pore formation to create the porous structure. This preliminary incorporation allows Al to diffuse to the surface during heat treatment, forming a protective layer that prevents silicon oxidation while maintaining high porosity (50-95%). The sequence of operations (alloy formation → pore formation → heat treatment) resolves the contradiction by achieving precise porosity control through the systematic arrangement of manufacturing steps.
2Reliability
If high-temperature heat treatment is applied to diffuse Al to the surface, then the electrochemical characteristics are improved, but the manufacturing process requires high temperature treatment which complicates production
Solution Approach 1:
The invention applies parameter changes by optimizing the heat treatment temperature range to 400-1100°C. Within this range, Al effectively diffuses to the silicon surface to form a protective layer, improving electrochemical characteristics such as charge-discharge cycle stability. The specific temperature parameters are controlled to achieve the desired Al diffusion and surface modification without excessive energy consumption or process complexity. This parameter optimization resolves the contradiction between improving reliability and managing temperature requirements.
3Manufacturing precision
If Al is completely removed from the silicon alloy, then the porous structure is achieved, but the electrochemical performance is insufficient compared to having Al on the surface
Solution Approach 1:
The invention applies local quality by creating a non-uniform distribution of Al within the porous silicon structure. Al is removed from the bulk to maintain high porosity and create the porous framework, but simultaneously diffused to the surface through heat treatment to form a localized protective layer. This results in a material with different compositions at different locations: the interior maintains high porosity for ion transport, while the surface has Al enrichment for protection and enhanced electrochemical performance. This spatial differentiation resolves the contradiction between porous structure formation 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 enhances the electrochemical performance of porous silicon materials by mitigating volume expansion and contraction, leading to improved charge and discharge cycle characteristics and increased capacity and energy density in power storage devices.
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
Implementation Method 2
micronization resulting from the volumetric expansion and contraction of an active material during charge and discharge
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.