Silicon Oxide Negative Active Material Composite for Lithium Battery
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Solution Overview
Problem
Lithium batteries with silicon oxide as a negative active material face unsatisfactory conductivity and lifetime characteristics due to volumetric changes during charging and discharging, and existing methods for forming a carbon coating layer do not adequately address these issues.
Innovation Solution
A negative active material composite with a matrix of silicon oxide, silicon carbide, and carbon, along with a carbon coating film, is formed using an arc discharging process, where silicon particles are uniformly dispersed in the matrix to prevent particle agglomeration and improve conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon oxide is used as a negative active material, then capacity is improved, but conductivity and lifetime characteristics deteriorate
Solution Approach 1:
The patent uses a composite material structure consisting of silicon oxide particles dispersed in a silicon-base inorganic compound matrix (Si-C-O or Si-C-N composite, SiN x, SiO y, or SiC z). This composite structure allows the silicon oxide to provide high capacity while the matrix provides structural stability and conductivity, resolving the contradiction between capacity and reliability.
Solution Approach 2:
The silicon-base inorganic compound acts as an intermediary matrix that surrounds and supports the silicon oxide particles. This intermediary structure prevents direct contact between silicon oxide particles, reducing particle destruction during volume changes while maintaining conductivity through the matrix material.
2Reliability
If a carbon coating layer is formed on silicon oxide surface, then conductivity is improved, but lifetime characteristics remain unsatisfactory
Solution Approach 1:
The patent creates a composite structure where silicon oxide particles are embedded in a silicon-base inorganic compound matrix with carbon content. This composite provides both the conductivity benefits of carbon coating and the structural stability needed for long lifetime, as the matrix accommodates volume changes better than a simple carbon coating.
Solution Approach 2:
The invention applies different properties to different parts of the electrode material: silicon oxide particles provide high capacity locally, while the surrounding silicon-base inorganic compound matrix provides structural stability and conductivity. This local differentiation allows each component to optimize its function without compromising the other.
3Reliability
If silicon particles are dispersed in silicon-base inorganic compound matrix, then particle destruction is prevented, but manufacturing complexity increases
Solution Approach 1:
The arc discharge method allows the silicon-base inorganic compound matrix to form around the silicon oxide particles in situ during the synthesis process. The high-energy arc discharge environment enables direct formation of the protective matrix structure without requiring separate coating or assembly steps, reducing manufacturing complexity while maintaining particle protection.
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 solution enhances the discharge capacity, conductivity, and cycle efficiency of lithium batteries by preventing particle destruction and maintaining conductivity without compromising capacity or lifetime characteristics.
Implementation Method 1
supplying silicon particles and silicon oxide to a carbon rod in an arc discharging device; and arc discharging the negative electrode and the positive electrode of the arc discharging device
Data Source
Figure 1~2A
Figure 2B~3
Figure 4
AI summary
A negative active material (10) including: a composite (11) including a matrix (11) comprising silicon oxide, silicon carbide, carbon and silicon particles (12) dispersed in the matrix (11); and a carbon coating film (13) formed on a surface of the composite (11), wherein an intensity ratio of a SiC peak to a Si peak in an X-ray diffraction spectrum is at least 1, a method of preparing the negative active material, a negative electrode including the negative active material, and a lithium battery including the electrode.