Effect of electrolytes on electrical charge storage performance in a compost-based symmetric device

Abstract

The prevalence of compost and its integration within the bio-circular economy, facilitating the seamless conversion of bio-waste into compost, present an auspicious avenue for the exploration of renewable energy storage solutions. Thus, the current study investigates the effect of electrolytes on faradic and non-faradic processes of charge storage in a symmetrical device design based on compost. The inquiry examines the composts as an electrode material and the influence of various current collectors (G–G, Cu–Cu and IN–IN) across distinct aqueous electrolyte environments (1 M KNO₃, 1 M KCl and 1 M KOH). The findings reveal the composts’ capacity to accommodate both capacitive and non-capacitive charge storage processes within a symmetric dual-current collector apparatus, showcasing the multifaceted charge storage modalities akin to those observed in capacitors and batteries. The electrochemical assessments, conducted through cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) profiling, and electrochemical impedance spectroscopy (EIS), elucidate the non-faradaic and faradaic charge storage mechanisms in terms of the charge storage efficiency, temporal characteristics of the charge and discharge cycle, specific capacitance, and specific capacity. The results obtained evince the superior charge storage capabilities of the compost samples across various electrolyte solutions relative to the aqueous media. The compost specimen featuring a C:N ratio of 145.44 in a 1 M KCl solution assembled in a symmetric G–G current collectors device exhibited the optimal electrochemical performance. At a scan rate of 100 mV/s within a potential window of ± 4.5 V, the CV studies exhibited an area under the curve of 3.3142C, a specific capacitance of 18.4mF/g and a specific capacity of 82.8 mC/g, while the GCD studies were characterised by a charging time of 51 s, a discharging time of 47.2 s, a specific capacitance of 10.4 mF/g and a specific capacity of 94.4 mC/g at an applied current of 400 mA within a potential window of ± 4.5 V.