Contents lists available at ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour Controllable synthesis of nanohorn-like architectured cobalt oxide for hybrid supercapacitor application Periyasamy Sivakumar a,b , Milan Jana a , Manikantan Kota a , Min Gyu Jung a , Aharon Gedanken b,* , Ho Seok Park a,c,d,** a School of Chemical Engineering, Sungkyunkwan University, 2066, Seoburo, Jangan-gu, Suwon, 440-746, South Korea b Department of Chemistry and the Institute for Nanotechnology and Advanced Materials (BINA), Bar-Ilan University, Ramat Gan, 5290002, Israel c Department of Health Sciences and Technology, Samsung Advanced Institute for Health Sciences and Technology (SAIHST), Sungkyunkwan University, 2066, Seoburo, Jangan-gu, Suwon, 440-746, South Korea d SKKU Advanced Institute of Nano Technology (SAINT), Sungkyunkwan University, 2066, Seoburo, Jangan-gu, Suwon, 440-746, South Korea HIGHLIGHTS • Nanohorn-like Co 3 O 4 architectures are synthesized. • The high specific capacitance of 2751 F g -1 is obtained at the opti- mized temperature. • Energy density of hybrid super- capacitor is ∼31.70 W h kg -1 . • Capacitance retention is 91.37% over 350,000 charge-discharge cycles. GRAPHICAL ABSTRACT ARTICLE INFO Keywords: Hybrid device Nanoarchitecture Cobalt oxide Supercapacitor High energy Electrode materials ABSTRACT We demonstrate a facile and controllable synthesis of horn-like Co 3 O 4 nanostructures through a solvothermal process followed by calcination at different temperatures. The particle sizes and defects of the as-obtained Co 3 O 4 nanohorns are controlled with respect to calcining temperatures, while preserving the horn-like morphology. In particular, the Co 3 O 4 nanohorn electrodes prepared at 300 °C reveal the specific capacitance of ∼2751 F g -1 and the rate capability of 46.8%, which is greater than those of materials obtained at 350, 400, and 450 °C. In order to enlarge the potential window, a hybrid supercapacitor is configured with the Co 3 O 4 nanohorn and activated carbon used as positive and negative electrodes, respectively. The as-fabricated hybrid supercapacitor shows high specific capacitance of ∼101 F g -1 and the rate capability of 80.5%. The energy and power densities of hybrid supercapacitor are ∼31.70 W h kg -1 and 16.71 kW kg -1 , respectively, along with 91.37% of capacitance retention over 350,000 cycles. These energy and power densities of the hybrid supercapacitors are approxi- mately 8.5 and 3.5 times greater than values of Co 3 O 4 symmetric supercapacitor. https://doi.org/10.1016/j.jpowsour.2018.09.026 Received 11 June 2018; Received in revised form 20 August 2018; Accepted 11 September 2018 * Corresponding author. Department of Chemistry and the Institute for Nanotechnology and Advanced Materials (BINA), Bar-Ilan University, Ramat Gan, 5290002, Israel. ** Corresponding author. School of Chemical Engineering, Sungkyunkwan University, 2066, Seoburo, Jangan-gu, Suwon, 440-746, South Korea. E-mail addresses: gedanken@biu.ac.il (A. Gedanken), phs0727@skku.edu (H.S. Park). Journal of Power Sources 402 (2018) 147–156 0378-7753/ © 2018 Elsevier B.V. All rights reserved. T