▎ 摘　　要

The evolution of advanced supercapacitors depends highly on the design and synthesis of electrodes with rational morphology and structure. In this paper, a facile methanol-assisted solvothermal method is reported for the synthesis of spherical hydrated manganese vanadate (MnV2O6.2H2O)-reduced graphene oxide (rGO) nanosheets hybrid. In particular, the utilization of methanol can not only change the isotropy growth of MnV2O6 but also suppresses the phase-transformation process (from orthorhombic to monoclinic) by preventing the deintercalation of crystal water. Remarkably, the MnV2O6.2H2O exhibits a superior specific capacity of 1678.5 F g-1 which is nearly four times more than that of MnV2O6 (410.2 F g-1) at 2 A g-1. After integrating with graphene, MnV2O6.2H2O spheres are uniformly encapsulated by graphene sheets with a size reduction from 1 mu m to 200 nm. And a "GO-assisted Ostwald ripen-splitting" mechanism is proposed to explain the formation of MnV2O6.2H2O-rGO. Consequently, the MnV2O6.2H2O-rGO hybrid exhibits significantly improved conductivity, enhanced specific capacity (1976.3 F g-1 at 2 A g-1) and good rate capability (1422.5 F g-1 at 10 A g-1 and 1155.5 F g-1 at 20 A g-1) as well as excellent cycling stability (94.2% capacitance retention after 10,000 cycles). Moreover, the assembled asymmetric supercapacitor using MnV2O6.2H2O-rGO (the positive electrode) and activated carbon (the negative electrode) shows a superior energy density of 51.5 Wh.kg- 1 at the power density of 849.2 W kg-1.