2D (Two-dimensional) Ni(OH)(2) nanosheets is synthesized by hydrothermal method with nickel nitrate hexahydrate and hexamethylenetetramine as raw materials. Herein, the effect of reaction temperature and time on the electrochemical performance of Ni(OH)(2) nanosheets are studied. The results showed that morphology and performance appeared great changes as the reaction time and temperature changed. The maximum specific capacitance of 1404.6 F g(-1) at current density of 1.5 A g(-1) by chronopotentiometry is achieved for Ni(OH)(2) nanosheets in 6.0M KOH when reaction temperature and time are 140 degrees C and 8 h. Moreover, the capacitance only reduced to 88% after 2000 times charge and discharge of constant current. Such results demonstrated that Ni(OH)(2) nanosheets is a promising electrode material for the practical application of high-performance supercapacitor and it is worthy of further investigation. (C) 2016 Elsevier B.V. All rights reserved.