Silicon-WO3 Anode Material With Controlled Surface Oxide
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Solution Overview
Problem
Existing negative electrode materials for lithium-ion rechargeable batteries, such as those containing tungsten trioxide or silicon, have room for improvement in performance.
Innovation Solution
A negative electrode material comprising carbon, tungsten trioxide, and a silicon material with a specific ratio of elemental silicon to silicon oxide in the surface layer, as measured by X-ray photoelectron spectroscopy, is developed to enhance performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is added to improve capacity, then battery capacity increases, but surface oxide formation increases causing higher impedance
Solution Approach 1:
The patent applies inert atmosphere by conducting silicon particle preparation in an atmosphere with oxygen concentration of 5% or less. This prevents excessive oxidation of the silicon particle surfaces during preparation, maintaining the Si/SiO2 ratio above 3 while still allowing controlled oxide formation for performance improvement.
2Reliability
If tungsten trioxide is applied to improve lithium ion diffusivity, then battery performance improves, but there is room for further performance enhancement
Solution Approach 1:
The patent uses composite materials by combining carbon, tungsten trioxide, and silicon particles with controlled Si/SiO2 ratio. This composite structure leverages the lithium ion diffusivity enhancement from tungsten trioxide while the optimized silicon component contributes to higher capacity, achieving both improved reliability and increased quantity of substance.
3Stability of the object's composition
If silicon particle surface is oxidized to improve stability, then material stability increases, but lithium ion penetration is hindered
Solution Approach 1:
The patent applies parameter changes by precisely controlling the Si/SiO2 atomic concentration ratio to be 3 or more. This optimized ratio balances material stability from surface oxide with lithium ion penetration capability, neither fully oxidized nor completely reduced state.
Solution Approach 2:
The patent uses inert atmosphere preparation with oxygen concentration of 5% or less to control the oxidation level of silicon particle surfaces, achieving the desired Si/SiO2 ratio that provides both stability and ion penetration.
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 improved negative electrode material enhances the capacity and reduces impedance by minimizing surface oxide thickness, facilitating lithium ion penetration and desorption.
Implementation Method 1
a ratio of an amount of Si in Si2p derived from elemental silicon to an amount of Si in Si2p derived from SiO2 in a surface layer is 3 or more, on an atomic concentration basis, as measured by X-ray photoelectron spectroscopy
Implementation Method 2
facilitating lithium ion penetration and desorption
Data Source
AI summary
To improve performance. A negative electrode material is a negative electrode material for a battery, and includes carbon, tungsten trioxide, and silicon particles (33) including silicon, and in the silicon particles (33), a ratio of the amount of Si in Si2p derived from elemental silicon to the amount of Si in Si2p derived from SiO2 in a surface layer is 3 or more, on an atomic concentration basis, as measured by X-ray photoelectron spectroscopy.