Silicon Anode Composite Using 3D Lithium Aluminosilicate Matrix
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Solution Overview
Problem
Conventional lithium ion secondary battery negative electrode active materials, such as those disclosed in Patent Literatures 1 to 3, do not employ a Li—Al—Si—O-based compound with a three-dimensional network structure, leading to a decrease in discharge capacity retention ratio (cycle characteristic) due to the collapse of silicon particles during lithium storage and release.
Innovation Solution
A lithium ion secondary battery negative electrode active material is developed, where silicon particles are dispersed in a matrix with a lithium aluminosilicate having a three-dimensional network structure, represented by the general formula LiAlxSiyO1/2+3x/2+2y+δ, where x satisfies 0.4≤x≤2.5, y satisfies 0.4≤y≤6.8, and δ satisfies −0.4≤δ≤0.4.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon particles are used as negative electrode active material to improve charging capacity, then charging capacity is improved, but discharge capacity retention ratio deteriorates due to particle collapse
Solution Approach 1:
The patent uses a composite material structure where silicon particles are dispersed in a lithium aluminosilicate glassy phase matrix. This composite structure allows the silicon to provide high charging capacity while the glassy matrix provides structural stability to prevent particle collapse during cycling, thereby maintaining discharge capacity retention ratio.
Solution Approach 2:
The lithium aluminosilicate glassy phase acts as a flexible matrix that can accommodate the volume expansion and contraction of silicon particles during lithium insertion and extraction. This flexible matrix structure prevents the silicon particles from collapsing while allowing the necessary volume changes for charge-discharge cycles.
2Reliability
If silicon oxide is used to suppress silicon expansion and contraction, then cycle characteristic is improved, but coulombic efficiency deteriorates due to side reactions
Solution Approach 1:
The patent changes the chemical composition parameters by using lithium aluminosilicate glassy phase instead of pure silicon oxide. This compositional change modifies the chemical properties to reduce side reactions with lithium while maintaining the structural benefits of oxide-based materials for suppressing silicon expansion and contraction.
Solution Approach 2:
The lithium aluminosilicate glassy phase serves as an intermediary material between the silicon particles and the electrolyte. It provides the structural support and chemical stability benefits of oxide materials while reducing the harmful side reactions that occur with pure silicon oxide, thus improving coulombic efficiency.
3Loss of energy
If Li-Si-O-based negative electrode with doped lithium is developed to improve coulombic efficiency, then coulombic efficiency is improved, but discharge capacity retention ratio deteriorates
Solution Approach 1:
The patent employs a composite material system where silicon particles are dispersed in a lithium aluminosilicate glassy phase. This composite structure simultaneously achieves good coulombic efficiency (through the lithium-doped glassy phase) and excellent discharge capacity retention ratio (through the three-dimensional network structure that prevents particle collapse).
Solution Approach 2:
The patent applies different properties to different parts of the composite material: the silicon particles provide high capacity, the glassy phase provides structural stability and suppresses particle collapse, and the lithium doping in the glassy phase improves coulombic efficiency. This local differentiation of functions resolves the contradiction between coulombic efficiency and capacity retention.
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 proposed active material effectively suppresses the collapse of silicon particles, thereby maintaining a superior discharge capacity retention ratio (cycle characteristic) and enhancing the overall performance of lithium ion secondary batteries, especially in in-vehicle applications.
Implementation Method 1
silicon particles being dispersed in a matrix whose main phase is a lithium aluminosilicate having a three-dimensional network structure
Data Source
AI summary
A lithium ion secondary battery negative electrode active material capable of suppressing decrease in discharge capacity retention ratio (cycle characteristic) even after repeating charge and discharge. The lithium ion secondary battery negative electrode active material is a composite with silicon particles being dispersed in a matrix that contains a lithium aluminosilicate having a three-dimensional network structure, wherein the lithium aluminosilicate is represented by the following general formula (1):LiAlxSiyO1/2+3x/2+2y+δ (1),wherein in the general formula (1), x satisfies 0.4≤x≤2.5, y satisfies 0.4≤y≤6.8, and δ satisfies −0.4≤δ≤0.4.