Surface Modified Silicon Oxide Particles for Lithium Battery Anodes
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Solution Overview
Problem
Rechargeable lithium batteries face challenges with negative active materials that have high surface oxygen ratios, leading to increased resistance and deterioration of electrochemical properties and cycle-life due to the natural layer of silicon dioxide on silicon oxide particles.
Innovation Solution
Surface-modified silicon oxide particles with a controlled silicon-to-oxygen ratio (Si/O) between 1.0 and 2.4 are created by selectively etching silicon dioxide from the surface, resulting in a concentration gradient that decreases silicon and increases oxygen from the surface to the core, improving electrochemical properties and cycle-life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon oxide particles with natural silicon dioxide layer are used as negative active material, then high capacity can be achieved, but surface resistance increases and electrochemical properties deteriorate
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of silicon and oxygen elements within the particle structure. The surface region has a higher silicon concentration and lower oxygen concentration compared to the core, which locally optimizes the surface for lithium ion insertion/extraction while maintaining the bulk silicon oxide structure for capacity. This gradient structure resolves the contradiction by making different regions of the same material serve different functions.
Solution Approach 2:
The patent changes the compositional parameters of the silicon oxide particles by controlling the silicon-to-oxygen ratio to be between 1.0 and 2.4 (preferably 1.2-2.0). This parameter change from the natural SiO2 stoichiometry (Si/O = 0.5) creates a non-stoichiometric silicon oxide that has reduced surface resistance while maintaining structural stability and lithium storage capacity.
2Stability of the object's composition
If silicon oxide particles with high oxygen content on surface are used, then structural stability is maintained, but cycle-life deteriorates due to increased resistance
Solution Approach 1:
The concentration gradient structure creates local quality differences where the core maintains high oxygen content for structural stability while the surface has lower oxygen content for reduced resistance. This spatial differentiation allows the material to simultaneously achieve both structural stability and improved cycle-life performance.
Solution Approach 2:
The patent creates a composite-like structure within the silicon oxide particle itself, with a core region rich in oxygen for stability and a surface region rich in silicon for conductivity. This internal composite structure allows the single material to exhibit multiple beneficial properties that would be contradictory in a homogeneous material.
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 modified silicon oxide particles exhibit improved cycle-life and electrochemical properties by reducing surface resistance and enhancing the capacity and efficiency of lithium batteries, with specific surface areas ranging from 10 to 500 m2/g and an average particle diameter of 0.1 μm to 100 μm.
Implementation Method 1
surface modified silicon oxide particles having a bulk formula represented by SiOx (0.5≤x≤1.5) and a silicon-to-oxygen ratio ranging from about 1.0 to about 2.4 on the surface
Data Source
AI summary
In an aspect, a negative active material for a rechargeable lithium battery including surface modified silicon oxide particles is disclosed.