Investigating impact of charging parameters on discharge efficiency of sodium polysulfide-bromide flow battery

Abstract

The polysulfide-bromide flow battery (PSB) stands out as a promising option, owing to the availability of raw materials like sodium polysulfide and sodium bromide solutions, easily sourced from Southeast Asia. This investigation concentrates on the PSB, with the aim of inspecting the numerous factors that influence its charge behavior, subsequently affecting its discharging efficiency. Five critical parameters of charging process underwent investigation: reaction kinetics affected by applied current, mass transfer influenced by flow rate, stoichiometry impacted by electrolyte ratio, durability influenced by storage time, and concentration gradient influenced by electrolyte volume. This article also presented the influence of electrolyte stability during storage, which directly impacts the state of charge (SOC) of the PSB. The stability of electrolytes was monitored, with data collected at hourly intervals initially and subsequently at 10-hour intervals throughout the study period. The research examines the performance of PSB in comparison with the widely recognized Vanadium Redox Flow Battery (VRFB). The battery exhibited its highest performance when charged with a current of 0.15 A, a flow rate of 20 ml min⁻¹, an electrolyte ratio of 1:1, and a volume of 50 ml. Under these conditions, the discharge efficiency was 19 % higher compared to the least favorable condition.