Ni3Se2 and Co-doped Ni3Se2 cauliflower-like nanostructures are synthesized using a simple and feasible electrochemical deposition technique. Electrochemical measurements of the resultant nanostructures in 1 M KOH electrolyte solution revealed that the energy storage performance of the cauliflower-like Ni3Se2 nanostructures was considerably improved by cobalt doping. Particularly, 6 wt% Co-doped Ni3Se2 electrodes exhibited remarkable high specific capacity (179.34 mAh g(-1)) and excellent stability with capacity retention of 85.9% over 1000 cycles because of their high electrical conductivity. Furthermore, to verify the feasibility of the optimized Co-doped Ni3Se2 electrodes for practical applications, Zn ion batteries were constructed by using a Zn plate as the anode and the Co-doped Ni3Se2 nanostructures as the cathode. The constructed Zn ion battery achieved high energy and power densities of 199.34 W h kg(-1) and 24,510 W kg(-1) at the current densities of 1 and 20 A g(-1), respectively. In addition, up to 2.2 electrons per formula unit of Ni3Se2 were successfully utilized, indicating considerably higher utilization of Ni2+/Ni1+ redox sites by Co doping the selenite. This work demonstrated an effectual strategy for rational design of highly robust, low-cost flexible electrodes for energy storage devices. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.