Mn3O4/Ni(OH)(2) nanocomposites are simply synthesized by a hydrothermal reaction between MnCl2 center dot 4H(2)O, NiCl2 center dot 6H(2)O and NaOH at 200 degrees C. Compared with the individual Ni(OH)(2) and Mn3O4 prepared under the same conditions, the Mn3O4/Ni(OH)(2) composite hydrothermally treated for 5 h achieves excellent specific capacitance (707 F g(-1) at 1 A g(-1) in 1 M KOH electrolyte) and remarkable long-term cycling stability (retaining a capacitance retention of 89% after 2000 cycles at 2 A g(-1)). Meanwhile, the asymmetric supercapacitor constructed by the Mn3O4/Ni(OH)(2) composite and active carbon delivers an energy density of 17.8 W h kg(-1) at a power density of 162 W kg(-1). The outstanding performance is attributable to the synergistic compositing effect of Mn3O4 and Ni(OH)(2), yielding not only the mutual doping of Mn3+ in Ni(OH)(2) and Ni2+ in Mn3O4 to improve the electronic conductivity of the Mn3O4/Ni (OH)(2) composite but also the suitable mesoporous structure for electrolyte transfer. Thus the Mn3O4/Ni (OH)(2) composites will be alternative candidates as practical electrode materials for pseudocapacitors. (C) 2017 Elsevier Ltd. All rights reserved.