Porous Silicon Negative Electrode for Lithium Battery Volume Expansion
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Solution Overview
Problem
Rechargeable lithium batteries face challenges with silicon-based negative electrode active materials due to high volume expansion and brittleness, leading to reduced cycle life and capacity.
Innovation Solution
A porous silicon-based negative electrode active material is developed by mixing porous silica with aluminum powder and heat-treating the mixture to form porous silicon and aluminum oxide, which reduces volume expansion and improves stability, and can include additional metal oxides for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative electrode active material is used to achieve high capacity, then capacity per gram is improved, but volume expansion occurs during lithium absorption and storage
Solution Approach 1:
The patent employs porous silicon as the negative electrode active material. The porous structure provides internal void spaces that can accommodate lithium ions during insertion and extraction cycles, allowing the material to achieve high capacity while the porous framework absorbs and distributes the mechanical stress of volume expansion, preventing structural collapse and maintaining electrode integrity over multiple cycles.
Solution Approach 2:
The patent creates a composite structure by combining porous silicon with conductive carbon materials and binding agents. This composite approach maintains the high capacity of silicon while the carbon matrix provides structural stability and electrical conductivity, accommodating the volume changes of silicon during lithiation and delithiation without compromising electrode integrity.
2Quantity of substance
If silicon-based negative electrode active material is used to achieve high capacity, then capacity per gram is improved, but brittleness increases leading to rapid crack formation
Solution Approach 1:
The porous structure of silicon provides inherent mechanical flexibility and stress distribution capabilities. The interconnected pore network allows the material to deform elastically during volume changes, preventing stress concentration that would lead to crack formation in dense crystalline silicon, thereby maintaining electrode integrity over multiple charge-discharge cycles.
Solution Approach 2:
By combining porous silicon with ductile carbon materials and flexible binding agents, the composite structure compensates for the inherent brittleness of silicon. The carbon matrix and binder provide mechanical reinforcement and flexibility, allowing the electrode to withstand repeated volume expansion and contraction without developing cracks that would degrade performance.
3Volume of moving object
If alloying with silicon is performed to reduce volume expansion, then volume expansion rate is reduced, but metal atomization occurs and cycle characteristic is declined
Solution Approach 1:
The porous silicon structure inherently accommodates volume changes during lithium insertion and extraction, reducing the effective volume expansion rate compared to dense silicon. The porous framework provides mechanical缓冲 (buffering) that prevents the extreme volume changes that lead to atomization, while maintaining structural integrity and good cycle characteristics over multiple charge-discharge cycles.
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 effectively reduces volume expansion and improves the cycle life and charge-discharge characteristics of lithium batteries by stabilizing the silicon structure with aluminum oxide and other metal oxides, enhancing the battery's overall performance.
Implementation Method 1
oxidizing all or part of the aluminum powder as an aluminum oxide while at the same time reducing all or part of the porous silica as a porous silicon (Si) by heat-treating a mixture of the porous silica with the aluminum powder
Implementation Method 2
oxidizing all or part of the aluminum powder as an aluminum oxide while at the same time reducing all or part of the porous silica as a porous silicon (Si) by heat-treating a mixture of the porous silica with the aluminum powder
Data Source
AI summary
The present invention relates to a method of preparing a porous silicon-based negative electrode active material comprising: mixing a porous silica (SiO2) and an aluminum powder; oxidizing all or part of the aluminum powder as an aluminum oxide while at the same time reducing all or part of the porous silica as a porous silicon (Si) by heat-treating a mixture of the porous silica with the aluminum powder, a negative electrode active material, and a rechargeable lithium battery including the same.