Electrochemical performances of KOH activated carbon coated vanadium oxide with sucrose as carbon source for sulfur immobilizers of lithium-sulfur batteries

摘要

Lithium-sulfur batteries due to high theoretical specific capacity have attracted extensive attention for many years. In this paper, we obtain a type of KOH activated sucrose carbonization coated V2O5 as sulfur immobilizers. X-ray diffraction and Raman spectrum tests illustrate that after carbon coating and sulfur loading, the V2O5 has been transformed into low valence vanadium oxide (VO2) and carbon has a high defect concentration after KOH activated. Scanning electron microscopy observes that the micromorphology of V2O5@C matrix materials with the ratio of V2O5 and sucrose to 1:3 shows a rose-like shape and lamellar thickness can be controlled below 100 nm. And after sulfur loading, the morphology of the original matrix material can still be maintained even at sulfur loading mass ratio to 1:5.Cyclic voltammetry and electrochemical impedance spectroscopy tests show that this cathode in the proportions of V2O5@C and S to 1:4 has the greatest superb electrochemical reversibility and the fastest electron transport rate. Charge and discharge tests show that the initial specific discharge capacities can respectively achieve to 831.54, 736.95 and 670.00 mAh.g(-1) at 0.05, 0.1 and 0.2C current rate and can be stable 100 charge and discharge cycles at 0.2C.