M-SiOx Anode Material Phase Balance for Silicon Volume Stability
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Solution Overview
Problem
Lithium secondary batteries with silicon-based particles face limitations in initial efficiency and lifespan due to excessive volume changes during charging and discharging, which are not effectively controlled by existing coatings or polymer composites, leading to reduced capacity retention and increased resistance.
Innovation Solution
A negative electrode active material comprising silicon-based particles represented by M-SiOx (where M is Li, Mg, Ca, or Ti) with a crystalline and amorphous phase ratio of 20 wt % to 70 wt %, prepared through vacuum-heating and solid-phase condensation, minimizing internal structural changes and optimizing lithium absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a SiO2 layer or carbon coating layer is formed on the silicon-based particle surface, then volume control is improved, but efficiency is reduced due to excessive coating
Solution Approach 1:
The invention changes the chemical composition parameter by introducing aluminum oxide (Al2O3) into the coating layer formulation. This creates a composite coating with optimized properties that controls volume expansion while maintaining efficiency, resolving the trade-off between volume stability and performance
Solution Approach 2:
The invention uses a composite coating layer comprising SiO2, carbon, and Al2O3. This composite structure combines the volume control benefits of SiO2, the conductivity benefits of carbon, and the structural stability benefits of Al2O3, achieving both volume control and efficiency simultaneously
2Stability of the object's composition
If a polymer composite is added on the carbon coating layer, then volume change control is improved, but resistance increases due to decreased conductivity
Solution Approach 1:
The invention creates a multi-component composite coating layer combining SiO2, carbon, and Al2O3 in specific proportions. The carbon component maintains conductivity while SiO2 and Al2O3 provide volume control, achieving both requirements simultaneously rather than sequentially as in prior art
Solution Approach 2:
The invention optimizes the local composition of the coating layer by distributing different materials (SiO2, carbon, Al2O3) in specific ratios throughout the coating structure. This localized optimization ensures that conductivity and volume control properties are balanced at every point in the coating layer
3Stability of the object's composition
If the silicon-based particle is excessively coated, then volume control is improved, but lithium ion absorption is hindered and capacity is reduced
Solution Approach 1:
The invention optimizes the thickness and composition parameters of the coating layer by incorporating Al2O3 and controlling the ratios of SiO2, carbon, and Al2O3. This creates a coating that is thin enough to allow lithium ion penetration but thick enough to control volume expansion, resolving the contradiction between protection and accessibility
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 initial efficiency and lifespan characteristics by controlling volume changes and reducing irreversible reactions, resulting in improved discharge capacity and cycle stability.
Implementation Method 1
the M-SiOx includes a crystalline phase and an amorphous phase, and includes the amorphous phase at 20 wt % to 70 wt % based upon a total weight of the M-SiOx
Implementation Method 2
vacuum-heating a powder mixture of Si and SiO2 to form SiOx
Implementation Method 3
mixing the SiOx vapor and the M vapor and solid-phase condensing the mixture of the SiOx vapor and the M vapor
Implementation Method 4
a negative electrode active material in which lithium ions exiting the positive electrode are intercalated and deintercalated
Data Source
AI summary
A negative electrode active material for a lithium secondary battery, which includes a silicon-based particle represented by M-SiOx, wherein M is Li, Mg, Ca, Al, or Ti, and 0≤x<2, wherein the M-SiOx includes an amorphous phase at 20 wt % to 70 wt % based upon a total weight of the M-SiOx, thereby exhibiting excellent initial efficiency and lifespan characteristics, and a preparation method thereof.