Lamellar Silicon Anode Material for Lithium-Ion Diffusion Paths
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Solution Overview
Problem
Existing methods for manufacturing silicon-based negative electrode active materials face limitations in reducing grain size and forming effective lithium-ion diffusion paths, leading to volume expansion and degradation of battery performance.
Innovation Solution
A lamellar structure silicon-based active material is formed by alloying with metal elements like Al, Ni, Co, Ti, Mn, Cu, Cr, Fe, Zr, Ag, or Au, adjusting the size of primary silicon and interlamellar spacing to facilitate lithium-ion diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based compound is used as negative electrode active material to increase capacity, then discharge capacity is improved, but volume expansion occurs during charging which disconnects conductive path and degrades battery characteristics
Solution Approach 1:
The silicon-based active material is divided into fine particles with controlled grain size (10-100 μm) to reduce volume expansion effects. The segmentation into smaller units prevents excessive expansion that would disconnect conductive paths, while maintaining high discharge capacity through increased surface area and lithium ion diffusion efficiency.
Solution Approach 2:
The grain size parameter of silicon-based particles is precisely controlled within 10-100 μm range, and oxygen content is adjusted to 1-30 wt% to optimize performance. These parameter changes balance capacity and structural stability, preventing conductive path disconnection while maintaining high discharge capacity.
2Speed
If grain size of silicon active material is reduced to form diffusion paths, then lithium-ion diffusion is improved, but manufacturing precision is limited due to high crystallinity of MG-Si
Solution Approach 1:
The grain size is controlled within 10-100 μm and oxygen content within 1-30 wt% through optimized casting and pulverization parameters. These parameter ranges achieve sufficient lithium-ion diffusion rates while being manufacturable from MG-Si, overcoming the limitation of high crystallinity.
Solution Approach 2:
Oxygen is introduced into the silicon-based active material during the casting process before pulverization, creating a eutectic structure that facilitates grain size control. This preliminary action enables subsequent grain size reduction to 10-100 μm while maintaining manufacturing feasibility.
3Productivity
If casting and pulverization method is used to manufacture negative electrode active material, then production efficiency is improved, but grain size cannot be reduced below hundreds of μm to several mm due to high crystallinity
Solution Approach 1:
Oxygen is added during the casting process to create a eutectic structure with controlled grain formation. This preliminary action enables the subsequent pulverization to achieve 10-100 μm grain size from MG-Si, overcoming the typical limitation of hundreds of μm to several mm while maintaining high manufacturing efficiency.
Solution Approach 2:
The casting parameters are optimized to control oxygen content at 1-30 wt%, which creates a eutectic structure that facilitates grain size reduction during pulverization. This parameter change enables achieving 10-100 μm grain size while maintaining high productivity through conventional casting and pulverization processes.
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 lamellar structure enhances cycle capacity retention and initial capacity efficiency by forming phase boundaries that act as diffusion paths for lithium ions, improving battery performance.
Implementation Method 1
when a lamellar-form silicon active material is formed by alloying with a metal element that undergoes a eutectic reaction with silicon
Implementation Method 2
a boundary between the two phases in the active material is formed, which acts as a diffusion path for lithium ions
Data Source
Figure 1~3
AI summary
The present application relates to a negative electrode active material, a method for manufacturing a negative electrode active material, a negative electrode composition, a negative electrode for a lithium secondary battery including the same, and a lithium secondary battery including a negative electrode.