Microwave-assisted hydrothermal synthesis of vanadium oxides for Li-ion supercapacitors: The influences of Li-ion doping and crystallinity on the capacitive performances

► VOx·nH2O with excellent capacitive behavior can be synthesized rapidly by an MAHS method. ► The crystal size and spacing distance of two adjacent layers are affected by the MAHS temperature and adding LiCl. ► The above two factors show great influences on the Li-ion intercalation capacity and rate. ► Doping Li ions into VOx·nH2O enlarges the spacing distance of adjacent layers and crystal size of VOx·nH2O. ► Doping Li ions into VOx·nH2O enhances its specific capacitance and prolongs its cycle life.