Sulfur-Doped Graphene as a Rational Anode for an Ionic Liquid Based Hybrid Capacitor with a 3.5 V Working Window
Navajsharif S. Shaikh, Vaibhav C. Lokhande, Pimsuda Pansa‐Ngat, S.B. Ubale, Jasmin S. Shaikh, Supareak Praserthdam, Sandip Sabale, C.D. Lokhande, Taeksoo Ji, Pongsakorn Kanjanaboos
Abstract
In this work, the facile thermal annealing of graphene oxide in a H2S atmosphere was used to obtain sulfur-doped graphene (SG) for anode materials for supercapacitors. The high electrical conductivity and the interconnected micro-pore structure of the SG electrode assisted in the fast transportation of electrons and ions at the electrode–electrolyte interface in the developed hybrid supercapacitors. The SG-based electrode resulted in an excellent specific capacitance of 460 F/g at 1 A/g. The nickel oxide could be obtained by a simple hydrothermal method, exhibiting a specific capacitance of 1236 F/g in 1 M KOH. The fabricated solid-state hybrid devices (Ss-HSCs) showed a high energy density of 21.8 Wh/kg at 661.7 W/kg power density with substantial cycling stability up to 89.0% over 1000 cycles in the PVA-KOH solid electrolyte. Considering pragmatic usages in heavy-duty appliances and hybrid vehicles, we fabricated quasi-solid-state ionic liquid BMIM-PF6/DMF based hybrid supercapacitors (Iq-HSCs) that were operated at 3.5 V. The Iq-HSC devices were capable of delivering 134.6 Wh/kg of the energy density at 1005.7 W/kg and the high power density with 69.3% capacitance retention over 1000 cycles.