Effect of graphite concentration on the electrochemical performance of a novel α-MnO₂-expanded graphite-PVDF composite cathode material based on FTO substrate

Abstract

A facile chemical reduction method is employed for the synthesis of α-MnO2 followed by ultrasonication with synthetic graphite and poly (vinylidene pyrrolidone) PVDF for the development of α-MnO2-expanded graphite-PVDF (MGP) composite. Known masses of MGP composite are drop-casted on a fluorine-doped tin oxide (FTO) conducting glass substrate for the fabrication of composite electrodes to use as the cathode. The compositional effects of various weight percentages of graphite on the electrochemical performance of the MGP composite are studied. The increase in graphite’s weight percentage is always accompanied by an equal reduction in the weight of MnO2 by maintaining a constant amount of PVDF. We demonstrate a maximum electrochemical performance for the composite containing 80% MnO2, 10% expanded graphite, and 10% PVDF, further increases in graphite concentration (reduction in that of MnO2) have detrimental effects on the performance. The basis characterisation of the composite is carried out using XRD, FTIR, UV-VIS, AFM, and SEM and the electrochemical studies are done using CV, GCD and EIS. We observe both faradaic and non-faradaic charge storage mechanisms in the composite samples with a 35% capacitive contribution and a 65% diffusive contribution to the total capacitance. Moreover, the composite electrode demonstrates a maximum specific capacitance of 358 F/g at 10 mV/s with an outstanding power density of 2.8 KW/Kg.