Silicon Anode Core-Shell Coating for Cycle Stability
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Solution Overview
Problem
Lithium ion batteries face issues with cyclic capacity attenuation due to side reactions between silicon particles and the electrolytic solution, leading to continuous consumption of reversible lithium and capacity loss.
Innovation Solution
A silicon core-shell composite structure is designed with a silicon-containing substrate coated by an MySiOz layer and optionally a carbon layer, where M includes Li, Mg, Ca, Sr, Ba, Al, Ti, or Zn, to prevent direct contact with the electrolytic solution, thereby reducing side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon particles are used as anode material to achieve high capacity, then the specific capacity is improved, but the cycle performance deteriorates due to high reactivity with electrolytic solution causing continuous SEI film thickening
Solution Approach 1:
The patent applies composite materials by creating a core-shell structure where silicon particles are coated with a silicon oxide layer (SiOx where 0.5 ≤ x ≤ 2). This composite structure combines the high capacity advantage of silicon with the stability of silicon oxide, preventing direct contact between silicon and electrolyte while maintaining lithium ion insertion/extraction capability, thus improving cycle performance without sacrificing specific capacity
Solution Approach 2:
The patent employs parameter changes by controlling the oxidation state of the silicon surface (SiOx with varying x values between 0.5 and 2). By adjusting the oxygen content parameter, the material maintains both high lithium ion insertion/extraction capacity and stability against electrolyte decomposition, resolving the contradiction between high capacity and good cycle performance
2Use of energy by moving object
If silicon surface is exposed to electrolytic solution to enable lithium ion insertion and extraction, then the initial coulombic efficiency is improved, but capacity attenuation increases due to side reactions and SEI film formation
Solution Approach 1:
The patent introduces silicon oxide (SiOx) as an intermediary layer between silicon and the electrolytic solution. This intermediate layer allows lithium ion insertion and extraction to proceed efficiently while blocking direct contact between silicon and electrolyte, thereby preventing harmful side reactions and SEI film formation that cause capacity attenuation
Solution Approach 2:
The patent converts the harmful effect of silicon- electrolyte reactions into a beneficial protective silicon oxide layer through controlled oxidation. The silicon oxide layer, which would normally be considered a passive coating, actually serves as an active protective barrier that maintains high initial coulombic efficiency while preventing capacity loss during cycling
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 anode material exhibits improved cycle performance and high initial coulombic efficiency, maintaining specific capacity and reducing capacity attenuation.
Implementation Method 1
performing thermal oxidization treatment on the surface of a silicon-containing substrate to obtain a silicon material with silicon dioxide on the surface
Implementation Method 2
heat-treating the mixed material at 400 to 1600° C. for 1 to 5 hr to obtain the anode material
Data Source
AI summary
An anode material includes silicon-based particles, the silicon-based particles include a silicon-containing substrate; at least a part of the surface of the silicon-containing substrate has an MySiOz layer; M includes Li, Mg, Ca, Sr, Ba, Al, Ti, Zn, or any combination thereof; and 0<y<3, and 0.5<z<6. The anode material has relatively high first Coulombic efficiency and good cycle performance.