In this work, we report the preparation of Co-2(OH)(3)Cl nanoparticles with average size of similar to 20 nm and well-defined cubic shape at room temperature by an epoxide precipitation route. It was found that the as-prepared Co-2(OH)(3)Cl nanoparticles could be used as a promising new electrode material for application in redox supercapacitors due to its high electrochemical performance. It presented superior specific capacitance of 783 F g(-1) at low current density of 2.8 A g(-1) while it had a high value of 604 F g(-1) at high current density of 56.6 A g(-1), proving its excellent high rate performance. Its 75% capacitance retention after 10,000 cycles of charge-discharge demonstrated its long-life span. According to characterization results, the possible mechanism for the electrochemical process that Co-2(OH)(3)Cl nanoparticles under-went was proposed as a process of Co-2(OH)(3)Cl -> beta-Co(OH)(2) -> CoOOH -> CO3O4. (C) 2017 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.