Carbon-Coated Silicon Oxide Anode With Magnesium Silicate Balance
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Solution Overview
Problem
Lithium secondary batteries using silicon oxide as a negative electrode active material face issues with irreversible capacity due to the formation of lithium oxide, leading to low initial charge efficiency and reduced cycle life, necessitating a solution that minimizes lithium oxide production while maintaining high capacity and efficiency.
Innovation Solution
A negative electrode active material comprising a silicon oxide composite with magnesium silicate and a carbon coating layer, where the X-ray diffractometry shows peaks of Mg2SiO4 and MgSiO3 without MgO, and the carbon coating layer is present in a specific weight ratio, reducing water content and enhancing electrical conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If silicon oxide is used as a negative electrode active material, then cycle life characteristics are improved due to small volume change during charge and discharge, but initial charge efficiency deteriorates to 70-75% due to formation of lithium oxide and lithium silicide
Solution Approach 1:
Magnesium silicate acts as an intermediary substance that reacts with lithium during initial charge to form magnesium oxide and lithium silicide instead of forming lithium oxide. This intermediary reaction prevents the formation of inactive lithium oxide, thereby improving initial charge efficiency while maintaining the cycle life benefits of silicon oxide
Solution Approach 2:
The invention changes the chemical composition parameters of the negative electrode material by incorporating magnesium silicate in a specific amount (0.1-10 wt% based on total negative electrode active material). This parameter change modifies the initial charge reaction products, converting harmful lithium oxide formation into beneficial magnesium oxide formation, thus improving initial charge efficiency
2Quantity of substance
If silicon is used as a negative electrode active material, then capacity is improved to about 4200 mAh/g which is 10 times or more of graphite-based material, but volumetric swelling during charge and shrinking during discharge causes micronization and degradation of capacity
Solution Approach 1:
The invention uses a composite material system consisting of silicon oxide combined with magnesium silicate. This composite structure provides both high capacity (silicon oxide offers approximately 5 times the capacity of carbonaceous materials) and structural stability (silicon oxide's small volume change characteristics), while the magnesium silicate component further stabilizes the structure during electrochemical reactions
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 significantly improves initial capacity and cycle efficiency by reducing lithium oxide formation, resulting in enhanced battery performance and extended life characteristics.
Implementation Method 1
a carbon coating layer... reducing water content
Implementation Method 2
X-ray diffractometry of the negative electrode active material shows peaks of Mg2SiO4 and MgSiO3
Data Source
AI summary
Disclosed is a negative electrode active material which includes: a silicon oxide composite including i) Si, ii) a silicon oxide represented by SiOx (0<x≤2), and iii) magnesium silicate containing Si and Mg; and a carbon coating layer positioned on the surface of the silicon oxide composite and including a carbonaceous material, wherein X-ray diffractometry of the negative electrode active material shows peaks of Mg2SiO4 and MgSiO3 at the same time and shows no peak of MgO; the ratio of peak intensity, I (Mg2SiO4)/I (MgSiO3), which is intensity I (Mg2SiO4) of peaks that belong to Mg2SiO4 to intensity I (MgSiO3) of peaks that belong to MgSiO3 is smaller than 1, the peaks that belong to Mg2SiO4 are observed at 2θ=32.2±0.2°, and the peaks that belong to MgSiO3 are observed at 2θ=30.9±0.2°.