Silicon-Carbon Anode Composition With Reduced SiO2 Surface Layer
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Solution Overview
Problem
Existing negative electrode materials for lithium ion secondary batteries, while improved with tungsten compounds and silicon, still have room for enhanced performance.
Innovation Solution
A negative electrode material comprising carbon, sodium tungstate, and a silicon material, where the silicon material has a surface layer with a ratio of elemental silicon to SiO2 of 3 or more on an atomic concentration basis, as measured by X-ray photoelectron spectroscopy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon particles are added to the negative electrode material, then battery capacity can be improved, but the oxide layer on silicon surface reduces lithium ion diffusivity and performance
Solution Approach 1:
The patent removes the harmful oxide layer (SiO2) from the silicon particle surface through chemical treatment with HF or NH4F solution, extracting the problematic component that impedes lithium ion diffusion while preserving the beneficial silicon core for high capacity
Solution Approach 2:
The patent applies different properties to different parts of the silicon structure: the surface is treated to be oxide-free for optimal lithium ion contact and diffusion, while the interior maintains the high-capacity silicon structure, creating a gradient of properties from surface to core
2Reliability
If tungsten compound is disposed on graphite surface, then lithium ion diffusivity is improved, but there is room for further performance improvement
Solution Approach 1:
The patent combines multiple beneficial components into a unified negative electrode structure: graphite provides stable lithium ion diffusion pathways, sodium tungstate enhances conductivity and diffusion, and oxide-free silicon particles contribute high capacity, creating a synergistic composite material that achieves superior overall performance
Solution Approach 2:
The patent creates a composite negative electrode material comprising graphite, sodium tungstate, and silicon particles with controlled oxide content, where each component contributes specific properties that collectively enhance battery performance beyond what any single material could achieve alone
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 proposed negative electrode material achieves improved performance by reducing the oxide layer on the silicon surface, enhancing lithium ion diffusivity, and maintaining high capacity and charge mobility.
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
Data Source
AI summary
Performance is improved. There is provided a negative electrode material for a battery, in which the negative electrode material includes carbon, sodium tungstate, and silicon particles 33 including silicon, and in the silicon particle 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 when measured by X-ray photoelectron spectroscopy is 3 or more on an atomic concentration basis.