A facile hydrothermal process with hexadecyltrimethyl ammonium bromide (CTAB) as the soft template is proposed to tune the morphology and size of cobalt hydroxide (Co(OH)(2)). Monodisperse beta-phase Co(OH)(2) nanowires with uniform size are obtained by controlling the CTAB content and the reaction time. Due to the uniform well-defined morphology and stable structure, the Co(OH)(2) nanowires material exhibits high capacitive performance and long cycle life. The specific capacitance of the Co(OH)(2) nanowires electrode is 358 F g(-1) at 0.5 A g(-1), and even 325 F g(-1) at 10 A g(-1). The specific capacitance retention is 86.3% after 5000 charge-discharge cycles at 2 A g(-1). Moreover, the asymmetric supercapacitor is assembled with Co(OH)(2) nanowires and nitrite acid treated activated carbon (NTAC), which shows an energy density of 13.6 Wh kg(-1) at the power density of 153 W kg(-1) under a high voltage of 1.6 V, and 13.1 Wh kg(-1) even at the power density of 1.88 kW kg(-1). (C) 2014 Elsevier B.V. All rights reserved.