INTERNATIONAL JOURNAL of RENEWABLE ENERGY RESEARCH M. Obeidat and M. A. Gharaibeh, Vol.8, No.3, September, 2018 Electrochemical Performance of MnO 2 for Energy Storage Supercapacitors in Solid-State Design Amr M. Obeidat*‡, Mohammad A. Gharaibeh** *Department of Electrical Engineering, Faculty of Engineering, Hashemite University, 13115 Zarqa, JORDAN **Department of Mechanical Engineering, Faculty of Engineering, Hashemite University, 13115 Zarqa, JORDAN (amrobeidat@hu.edu.jo, mohammada_fa@hu.edu.jo) ‡ Corresponding Author: Amr M. Obeidat, Hashemite University, 13115 Zarqa, JORDAN, Tel: +962 (5) 3903333-4468, amrobeidat@hu.edu.jo Received: 25.12.2017 Accepted:08.03.2018 Abstract- In this work, solid-state supercapacitors with ionic liquid gel polymer electrolyte and MnO 2 electrodes were fabricated and characterized. The MnO 2 electrode was prepared by ultra-short pulsed electrochemical deposition over flexible graphite substrates. The ionic liquid gel polymer electrolyte was prepared by immobilizing ionic liquid BMIBF 4 with PVdF- HFP. The electrochemical performance of the solid-state supercapacitor was evaluated by three electrochemical characterization techniques including cyclic voltammetry (CV), galvanostatic charge-discharge (CD), and electrochemical impedance spectroscopy (EIS). CV measurements were conducted at two different voltage ranges showing typical capacitive character evidenced from the nearly rectangular shape. Charge-discharge analysis showed specific energy and specific power values of 1.27 Wh kg -1 and 0.292 kW kg -1 , respectively. EIS analysis confirmed the capacitive character of the device and produced an areal capacitance density of 39.68 mF cm -2 (equivalent to a specific capacitance of 36.68 F g -1 ). The presence of MnO 2 in the electrodes was confirmed by Raman spectroscopy with two major peaks observed at 550 cm -1 and 630 cm -1 . Keywords Supercapacitors; Pseudocapacitors; Manganese Oxide; Energy Storage; Solid-State Design; Pulsed Electrochemical Deposition 1. Introduction Due to their sustainability and cost effectiveness, renewable and efficient energy systems including energy storage technologies are being actively researched [1-8]. Supercapacitors are electrochemical energy storage devices that are designed to bridge the gap between batteries and conventional capacitors. Supercapacitors have attracted significant attention due to their high power density, excellent reversibility, and high cycle life. Furthermore, they can be used in a wide variety of applications including portable electronics, memory back-up systems, hybrid electric vehicles, and military missile systems [9]. Depending on the electrode material, supercapacitors are generally classified into electrical double layer capacitors (EDLCs) and pseudocapacitors. EDLCs are designed with carbon materials such as graphene and carbon nanotubes. Pseudocapacitors are designed with conducting polymers such as polypyrrole, polyaniline, and polythiophene, and transition metal oxides such as RuO 2 , Fe 3 O 4 , and MnO 2 [10, 11]. RuO 2 has shown the highest electrochemical performance among all transition metal oxides. However, the very high cost and low porosity of RuO 2 limited the viability of this material [12, 13]. MnO 2 is a good replacement of RuO 2 due to its low cost, high energy density, natural abundance, and environmental friendliness [10, 11, 14-19]. Furthermore, MnO 2 has a high theoretical specific capacitance of 1370 F g -1 [13, 14, 16, 18-20]. However, this value was rarely achieved in practice due to the low electrical conductivity of MnO 2 [9, 16, 18, 20]. Different synthesis techniques have been reported and used to prepare MnO 2 including co-precipitation, thermal decomposition, hydrothermal synthesis, sol-gel processes, physical vapor deposition, dip coating, electrophoresis, deposition from