Exfoliated Graphite as a Potential Host for Zinc Oxide Nanorods-Based Symmetric Flexible Supercapacitor

Supercapacitors (SCs) have drawn a considerable concentration because of their magnificent power density, extended cycle life, rapid charge/discharge rate, and with nearly negligible short–circuit problems compared to conventional batteries and capacitors. Carbon–based nanomaterials are widely used for supercapacitor electrodes because of their enormous surface area and electrical conductivity. Here we propose a symmetric supercapacitor made of exfoliated graphite (EXG) as a host with the composites of ZnO nanorods (NRs) in different ratios to show its capability to store the enhanced energy in a simple system. Highly porous exfoliated graphite was synthesized using the thermal exfoliation method of a chemically treated natural graphite flakes (NGFs) and compressed to paper with ZnO NRs synthesized by the hydrothermal route. SCs contain compressed electrodes of the EXG-10% ZnO NRs composite. The electrochemical behavior of SCs was investigated using Cyclic Voltammetry (CV) in 0 to 0.6 V potential window at different scan rates. The measured areal–specific capacitance is ~15 mF/cm2 at 10 mV/s scan rate for 10% ZnO NRs and EXG composite electrode. The capacity retention is more than 95% after the 1000 cycles at a higher scan rate, suggesting highly stable electrodes. Electrochemical impedance analysis is also carried out before and after the complete cycling to analyze the electrode interface resistance. The pseudocapacitive materials have high specific capacitance and low cycle life while carbon materials have long cycle life and less specific capacitance. This work employs less weight percentage of ZnO as a potential booster to increase the capacitance of EXG-based symmetric SC. EXG-10% ZnO NRs composite is a highly stable electrode material for symmetric SC with optimal capacity.