Thermal oxidation of MoS2 into defective crystalline MoO3 with enhanced Li-ion storage kinetics

Abstract

Thermal oxidation in air of molybdenum disulfide (MoS2) into layer structured molybdenum trioxide (α-MoO3) is investigated using a combination of thermal analysis, electron microscopy, Raman, X-ray diffraction and photoelectron spectroscopy. The phase evolutions occurred during the thermal process is characterized by the surface oxidation of MoS2, followed by the bulk oxidation to form α-MoO3 and the formation of Mo17O47 at higher temperatures. The single-phase MoO3 formed at optimum temperature condition is found to possess crystalline defects and considerably greater values of Li-ion storage cycling and rate performances in comparison with samples prepared at alternative temperatures and also the initial MoS2. This sample (P-MoO3-820) exhibits a charge capacity of 628 mA h g−1 after 250 cycles (100 mA g−1) with a Li+ diffusion coefficient of 2.3 × 10-13 cm2 s−1, substantially greater than that of initial MoS2 (8.1 ×10−16 cm2 s−1). The electrochemical performance of P-MoO3-820 in full-cell configuration against a commercial LiFePO4 cathode is evaluated and a specific capacity of 100 mAh g−1 after 500 cycles is recorded. This article, for the first time, discusses the thermal oxidation in air of MoS2 as a simple and relatively clean approach to fabricate defective crystalline MoO3 with enhanced Li-ion storage kinetics.