Porous waxberry-like MnO2/La2O3 microspheres for high performance asymmetric supercapacitor

In this paper, porous waxberry-like microspheres structures of MnO2/La2O3 (Mn-La) composites were synthesized via a facile two-pot hydrothermal method. The microstructure and chemical composition of as-prepared Mn-La composites were characterized by a series of techniques such as XRD, SEM, TEM, HRTEM, XPS and BET. The results show that the pure MnO2 microspheres were covered with its large amount of well-ordered nanorods, and La2O3 was distributed evenly on MnO2 surface to constitute Mn-La composites. Meanwhile, the electrochemical tests reveal that sample Mn-La10 (molar ratio (MnO2)-Mn-n:(La2O3)-La-n = 1:0.1) exhibited the highest specific capacitance (Cm) (245.4 Fg(-1) at a current density of 0.3 Ag-1, 1.5 times of MnO2), good rate performance and excellent cycling stability (97.5% capacitance retention after 3000 cycles at current density of 2.0 Ag-1). In general, suitable amount of La2O3 doping, based on the synergistic effect between MnO2 and La2O3, is helpful to improve the capacitance performance of composites. Furthermore, an asymmetric supercapacitor (Mn-La10//AC), with Mn-La10 as the positive electrode and activated carbons as the negative electrode, displays high energy density of 25.8 Wh kg(-1) with a maximum power density of 0.3 kW kg(-1) under potential window of 2.0 V. (C) 2017 Elsevier Ltd. All rights reserved.