Silicon Oxide Composite Anode with MgxSiOy Shell for Volume Expansion
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Solution Overview
Problem
Conventional anode materials for lithium secondary batteries, such as silicon and silicon oxide, face challenges with volume expansion, irreversible reactions, and low initial charge/discharge efficiency, leading to reduced capacity and stability.
Innovation Solution
A silicon oxide composite is developed with a core-shell structure, comprising a Si cluster and MgxSiOy (0.5≤x≤2, 2.5≤y≤4) on the peripheral portion, formed through a gaseous reaction of Si/SiOx/SiO2 with metallic magnesium, followed by carbon coating, to enhance capacity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as anode material to achieve high theoretical capacity of 4200 mAh/g, then capacity is improved, but volume expansion by 300% or higher causes pulverization and electrical deionization
Solution Approach 1:
The patent embeds Si clusters within a magnesium silicate matrix, creating a nested core-shell structure where the Si cluster is contained within the protective MgxSiOy shell. This nesting approach allows the high-capacity Si to be isolated from direct contact with electrolyte while still enabling Li ion diffusion, thus maintaining capacity while preventing pulverization.
Solution Approach 2:
The patent creates a composite material consisting of Si clusters and magnesium silicate (MgxSiOy), combining the high capacity of silicon with the structural stability and volume expansion buffering capability of magnesium silicate. This composite structure prevents pulverization while maintaining electrochemical performance.
2Reliability
If silicon oxide is used to improve volume expansion rate and lifetime characteristics, then stability is improved, but initial charge/discharge efficiency decreases to 75% or less due to non-reversible reaction
Solution Approach 1:
The patent creates a non-uniform structure where Si clusters are concentrated in the core region while the peripheral region consists of magnesium silicate. This local quality differentiation allows the core Si to provide high capacity while the peripheral MgxSiOy layer buffers volume expansion and prevents irreversible reactions, achieving both high initial efficiency and good lifetime characteristics.
3Reliability
If carbon coating is applied to silicon particles to prevent pulverization, then stability is improved, but control of volume expansion and contraction is limited
Solution Approach 1:
The patent changes the material parameter from conventional carbon coating to magnesium silicate coating, which has different physical and chemical properties. Magnesium silicate provides superior adaptability for volume expansion control due to its crystal structure that can accommodate lattice changes, unlike carbon which has limited expansion control capability.
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 composite exhibits a high capacity maintaining rate and improved initial charge/discharge efficiency, surpassing conventional materials by maintaining a higher capacity and reducing irreversible reactions.
Implementation Method 1
evaporating the Si/SiOx/SiO2 raw material powder mixture and metallic magnesium, respectively, reacting them, and then depositing the resultant to form an oxide composite
Implementation Method 2
reacting them, and then depositing the resultant to form an oxide composite
Implementation Method 3
evaporating the Si/SiOx/SiO2 raw material powder mixture and metallic magnesium, respectively, reacting them, and then depositing the resultant to form an oxide composite
Data Source
AI summary
The present invention relates to a silicon oxide composite for a lithium secondary battery anode material and a method for manufacturing same and, more specifically, to a silicon oxide composite for a lithium secondary battery anode material and a method for manufacturing same, wherein the silicon oxide composite comprises a Si cluster and MgxSiOy(0≤x≤3, 0≤y≤5) formed on a peripheral portion of the Si cluster.