A High-Performance Li₂FeSiO₄/C Cathode Enhanced by a Novel Liquid-State Carbon Source

摘要

A novel liquid-state carbon source, [2-[(2R,3S,4R)-3,4-dihydroxytetrahydrofuran-2-yl]-2-hydroxyethyl] dodecanoate (sorbitan monolaurat, Span-20, C18H34O6), is used to synthesize Li2FeSiO4/C by thesol-gel method. X-ray diffraction and scanning electron microscope measurements are carried out todetermine the crystal structures, morphologies and particle sizes of the resulting products. The resultsshow that Li2FeSiO4/C has pure phase and the average particle size of Li2FeSiO4 is in 20-30 nm. Theresult of Raman spectroscopy measurement indicates that the liquid-state carbon source can be proneto generate the carbon materials with high-ordered structure compared to the solid-state carbon source.The Li2FeSiO4/C cathode delivers an initial discharge capacity of 187 mAh g-1 at 0.1 C rate, and it alsoshows good rate performance and stable cycle performance, indicating that the liquid-state carbonsource helps to improve the electrochemical performance of the Li2FeSiO4/C cathode. By analyzingelectrochemical impedance spectra, it is concluded that the carbon coating layer generated from theliquid-state Span-20 enhances the electrode/electrolyte interface characterization and improves the Li+diffusion.