Silicon Negative Electrode with Nitrided Metal Matrix
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Solution Overview
Problem
Lithium secondary batteries using silicon as a negative electrode face mechanical instability and capacity degradation due to volume changes during charge and discharge cycles, leading to reduced electrical contact and cycle performance.
Innovation Solution
A negative electrode comprising a metal matrix with silicon nanoparticles and metal/silicon nitrides on its surface, formed through nitridation of a metal and silicon precursor, which enhances mechanical stability and electrical conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as negative electrode material to achieve high theoretical capacity, then battery capacity increases, but mechanical stability deteriorates due to volume changes during charge and discharge cycles
Solution Approach 1:
The silicon negative electrode is divided into multiple layers, with a first silicon layer and a second silicon layer separated by an aluminum oxide barrier layer. This segmentation prevents continuous crack propagation through the electrode structure and isolates volume expansion effects to individual layers, thereby maintaining mechanical stability while preserving high capacity.
Solution Approach 2:
The patent employs a multi-layer nested structure where silicon layers are embedded within a coating layer containing aluminum oxide and aluminum hydroxide. The barrier layer is nested between silicon layers, creating a protective hierarchy that constrains silicon volume changes and prevents structural collapse during cycling.
2Reliability
If silicon nanoparticles are embedded in metal matrix to improve mechanical stability, then structural integrity improves, but manufacturing complexity increases
Solution Approach 1:
The patent specifies precise compositional parameters for the coating layer (aluminum oxide and aluminum hydroxide in weight ratios of 70:30 to 30:70) and controlled layer thicknesses (first silicon layer: 1-10 μm, second silicon layer: 1-10 μm, coating layer: 1-20 μm). These parameter specifications standardize the manufacturing process and simplify production while ensuring structural integrity.
3Reliability
If aluminum oxide and aluminum hydroxide coating layer is applied to prevent cracks, then mechanical stability improves, but manufacturing process complexity increases
Solution Approach 1:
The coating layer serves multiple functions simultaneously: it acts as a mechanical barrier to prevent crack propagation, provides chemical stability through aluminum oxide and aluminum hydroxide composition, and facilitates standardized manufacturing through spray coating or dip coating methods. This multi-functionality reduces the need for separate protective treatments.
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 nitridated negative electrode exhibits improved capacity retention and lifespan by reducing contact resistance and preventing mechanical cracks, resulting in enhanced electrical conductivity and chemical stability.
Implementation Method 1
a metal nitride and a silicon nitride that are located on at least a portion of a surface of the metal matrix
Data Source
AI summary
In an aspect, a negative electrode for a lithium secondary battery and a method of manufacturing the same is provided. The negative electrode for the lithium secondary battery includes a negative active material layer.