Synthesis of MoO2/Mo2C/RGO composite in supercritical fluid and its enhanced cycling stability in Li-ion batteries

Abstract Herein, we present a new strategy for inhibiting the volume expansion of MoO 2 during lithiation and delithiation by preparing MoO 2 /Mo 2 C core-shell particles deposited on reduced graphene oxide (RGO). The MoO 2 /Mo 2 C/RGO composite was synthesized by first preparing the MoO 2 /RGO composite in supercritical methanol (scMeOH) followed by carbothermal hydrogen reduction. Carbon migration from RGO and organic moieties attached to the surface of MoO 2 particles synthesized in scMeOH produced a Mo 2 C film during carbothermal reduction. When tested as an anode in lithium ion batteries, the MoO 2 /Mo 2 C/RGO composite exhibited an increased initial coulombic efficiency (77%), long-term cyclability (500 mAh g −1 at 50 mA g −1 after 150 cycles), and high-rate performance (200 mAh g −1 at 1 A g −1 ) compared with those of the MoO 2 /RGO composite (53%; 280 mAh g −1 at 50 mA g −1 after 150 cycles; 120 mAh g −1 at 1 A g −1 ). Electrochemical impedance spectra showed that the MoO 2 /Mo 2 C/RGO composite exhibited reduced solid electrolyte interphase (SEI) resistance and facilitated Li ion transport into the electrode. The presence of Mo 2 C with low electrochemical activity, but high electronic conductivity, could decrease SEI formation and suppress volume expansion, which prolonged the cycling life.