Silicon-Oxygen-Carbon Anode Composite for Stable SEI and Cycle Life
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Solution Overview
Problem
The existing silicon-carbon composite materials for lithium-ion batteries face challenges with the uniform dispersion of silicon nanoparticles, leading to significant volume expansion and contraction during charge and discharge cycles, which results in poor cycle performance and electrode degradation due to the formation and damage of the SEI film.
Innovation Solution
A nano silicon-oxygen-carbon structural composite material is developed, where silicon nanoparticles are uniformly dispersed on a porous carbon substrate with a surface oxidized layer, separated and bounded by an oxygen-containing substance and optional carbon, using a specific preparation method that includes heat treatment and oxidation processes to control the size and distribution of silicon particles, thereby stabilizing the SEI film and reducing volume changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon nanoparticles are used to increase capacity, then the theoretical capacity increases from 372 mAh/g to 4200 mAh/g, but the volume expansion reaches 300% causing electrode pulverization and poor cycle stability
Solution Approach 1:
Silicon nanoparticles are nested within the porous structure of carbon substrate, forming a composite where the inner silicon particles are contained and protected by the outer carbon matrix. This nested structure allows the silicon to expand and contract within the porous carbon framework, preventing electrode pulverization while maintaining high lithium intercalation capacity.
Solution Approach 2:
The patent creates a composite material combining silicon nanoparticles with porous carbon substrate. The composite structure leverages the high capacity of silicon and the structural stability of carbon, achieving both high capacity (up to 4200 mAh/g theoretical) and good cycle stability by distributing volume changes throughout the composite framework.
2Stability of the object's composition
If silicon particles are dispersed to reduce volume effect, then the volume expansion is suppressed, but the particles tend to aggregate and fuse during charge and discharge processes
Solution Approach 1:
The porous carbon substrate is prepared in advance with a specific pore size distribution (0.003-0.05 cm³/g) and surface area (0.1-10 m²/g) before silicon nanoparticle introduction. This preliminary structuring of the carbon framework creates predetermined spaces and anchoring sites that prevent silicon particle aggregation during subsequent charge-discharge cycles, maintaining both volume stability and particle dispersion.
3Quantity of substance
If SEI film formation is allowed to occur, then the initial coulombic efficiency is reduced due to irreversible lithium consumption, but without SEI film the electrode surface is unstable
Solution Approach 1:
The porous carbon substrate provides locally different environments: the internal porous structure allows controlled SEI film formation with limited lithium consumption, while the overall composite structure maintains electrode surface stability. The local porous architecture enables the SEI film to form in a controlled manner, reducing irreversible lithium loss while ensuring surface protection.
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 lithium-ion battery with high capacity per gram, high initial coulombic efficiency, and improved cycle performance by effectively suppressing silicon particle aggregation and fusion, enhancing the electrochemical stability of the anode material.
Implementation Method 1
silicon nanoparticles are uniformly dispersed on a porous carbon substrate with a surface oxidized layer
Implementation Method 2
silicon nanoparticles are uniformly dispersed on a porous carbon substrate with a surface oxidized layer, separated and bounded by an oxygen-containing substance
Implementation Method 3
using a specific preparation method that includes heat treatment and oxidation processes to control the size and distribution of silicon particles
Implementation Method 4
using a specific preparation method that includes heat treatment and oxidation processes
Data Source
AI summary
The present disclosure provides a nano silicon-oxygen-carbon structural composite material, a preparation method thereof, an anode, and an electrochemical device. The composite material includes (Cx1—Oy1)—(Siz—Oy2—Cx2), wherein Cx1—Oy1 is a porous carbon substrate containing a surface oxidized layer, and 0.001≤y1/x1≤0.05; Siz—Oy2—Cx2 includes silicon nanoparticles, an oxygen-containing substance and an optional carbon, wherein the silicon nanoparticles, the oxygen-containing substance and the optional carbon are dispersedly distributed on the surface and/or within the pores of the porous carbon substrate containing a surface oxidized layer, and the oxygen-containing substance presents in a form of SiOδ, wherein 0≤δ≤2, 0.1≤z/x1≤2, 0.01≤y2/z≤0.15, and 0≤x2/z≤0.15. The silicon nanoparticles are uniformly dispersed in the composite material, separated and bounded by the oxygen-containing substance and the optional carbon, controlling their volume changes and possible fusion during charge and discharge cycles, thereby improving the cycle performance of lithium batteries.