Analysis of the Lithium Storage Mechanism in the SiO x /C Composite Based on the Performance Variation Applied to a Lithium-Ion Battery

TheSiO( x )/C composite, as a form ofsilicon-based materials, has been considered as an attractive alternativeanode for next-generation lithium-ion batteries. The porous SiO0.71C1.95N0.47 anode material exhibitingrobust Si-O skeletons wrapped by carbon layers is successfullyprepared and delivers an initial capacity of over 1700 mAh g(-1) with an initial coulombic efficiency of 69.4% and favorable cyclelife. Both Si (2p) X-ray photoelectron spectroscopy (XPS) and Si-29 nuclear magnetic resonance (NMR) demonstrate the existenceof SiO4 and SiO3C units as main lithium storagesites in the original state. The XPS curve moved toward the directionof the binding energy decreasing with NMR spectra shifting to a highfield after the first lithiation process. The massive capacity lossduring the first discharge and charge cycle results from the formationof irreversible Li silicate (Li2SiO4). The fluctuationof the charge and discharge capacity, including a persistent declineduring the first 30 cycles and a continuous elevation in the following400 cycles, could be attributed to the participated degree of reversibleLi silicate (Li2SiO3 and Li2Si2O5) in the delithiation process. The Si-Oskeletons are gradually corroded and ultimately destroyed in the final400 cycles, leading to the sharp drop of the cycling performance ofthe half-cell.

Automated summary

The SiO(x)/C composite, as a silicon-based material, is a promising alternative anode for next-generation lithium-ion batteries. The porous SiO0.71C1.95N0.47 anode material with robust Si-O skeletons wrapped by carbon layers exhibits excellent initial capacity, coulombic efficiency, and cycle life.