Submicron Silicon Powder Low Oxygen Passivation
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Solution Overview
Problem
Submicron silicon powders used in lithium-ion batteries oxidize rapidly, leading to high oxygen content and significant capacity losses due to irreversible reactions, limiting their performance and lifespan.
Innovation Solution
A submicron sized silicon powder with a controlled surface layer of SiOx (0<x<2) is synthesized using a gas phase technology, involving vaporization, quenching, and passivation in an oxygen-containing gas at controlled temperatures to maintain low oxygen content (<3% by weight) and prevent further oxidation, allowing for stable passivation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If submicron silicon powder is exposed to air, then surface area and reactivity are improved for battery performance, but oxygen content increases rapidly leading to capacity losses
Solution Approach 1:
The patent applies preliminary action by performing passivation treatment during the powder synthesis process itself, rather than attempting to prevent oxidation afterward. The controlled oxygen exposure during synthesis creates a protective SiOx surface layer before the powder is fully formed, preventing subsequent rapid oxidation when exposed to air.
Solution Approach 2:
The patent utilizes parameter changes by controlling the oxygen partial pressure and temperature during synthesis to achieve a specific surface layer composition (SiOx with 0<x<2). By adjusting these parameters, the surface layer provides protective function while maintaining low overall oxygen content (<3 wt%), resolving the contradiction between surface area and oxygen content.
2Quantity of substance
If submicron silicon powder is synthesized to enhance energy density, then battery capacity is improved, but first-cycle irreversible capacity loss increases due to surface oxidation
Solution Approach 1:
The patent converts the harmful effect of oxidation into a beneficial protective mechanism. By introducing controlled oxygen during synthesis, a surface layer forms that prevents further oxidation and reduces irreversible capacity loss. The harmful oxidation is transformed into a protective surface treatment that enhances overall battery performance.
Solution Approach 2:
The patent changes the oxidation state parameter from complete oxidation (SiO2) to partial oxidation (SiOx with 0<x<2), creating an optimal surface layer that provides protection without excessive oxygen content. This parameter optimization reduces first-cycle irreversible capacity while maintaining high energy density.
3Quantity of substance
If conventional silicon negative electrode materials are used, then theoretical capacity is high, but volume expansion upon lithium intercalation causes poor cycle life
Solution Approach 1:
The patent applies segmentation by dividing the silicon structure into submicron particles with controlled surface layers. This segmentation reduces the impact of volume expansion on overall electrode integrity, as the small particle size and protective surface layer prevent structural degradation during cycling, thereby extending cycle life while maintaining high capacity.
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 approach results in a silicon-based negative electrode material with reduced first-cycle irreversible capacity and maintained high reversible capacity, ensuring stable performance and longevity in lithium-ion batteries.
Implementation Method 1
involving vaporization, quenching, and passivation
Implementation Method 2
involving vaporization, quenching, and passivation
Implementation Method 3
passivation in an oxygen-containing gas at controlled temperatures to maintain low oxygen content
Data Source
AI summary
A submicron sized Si based powder having an average primary particle size between 20 nm and 200 nm, wherein the powder has a surface layer comprising SiOx, with 0<x<2, the surface layer having an average thickness between 0.5 nm and 10 nm, and wherein the powder has a total oxygen content equal or less than 3% by weight at room temperature. The method for making the powder comprises a step where a Si precursor is vaporized in a gas stream at high temperature, after which the gas stream is quenched to obtain Si particles, and the Si particles are quenched at low temperature in an oxygen containing gas.