The combined impact of trimethyloctadecylammonium chloride and sodium fluoride on cycle life and energy efficiency of soluble lead-acid flow battery

The development and commercialization of SLRFB is obstructed due to its limited cycle life. The cycle life is prevented due to the formation of Pb dendrites, sluggish kinetics of Pb+2/PbO2 redox species, partial reversibility of PbO2, and O-2 evolution during charging. SLRFB has common electrolyte reservoir, therefore, it is desirable to add both anode and cathode benefitting additives together in the electrolyte. But, such kind of study is very limited in the literature. By considering this, first time, the present work demonstrates the combined effect of trimethyloctadecylammonium chloride and NaF/LiF as electrolyte additives on the electrochemical performance and cycle life of SLRFB. Compared with the pristine electrolyte, the kinetics and reversibility of Pb2+/PbO2 redox couple are improved in the presence of additives. Both Pb and PbO2 electrodeposits are smooth, compact and uniform in the presence of additives. The lifespan of SLRFB without any additive is limited to 45 charge/discharge cycles due to shorting of the electrodes. The CE has been decreased from 93 % to 74 % in 46th cycles at a charging current density of 20 mA cm(2). However, in the presence of additives, the cell has been successfully cycled for over 500 cycles with an average CE, VE and EE of 94 %, 78 % and 74 % respectively. The cell also showed the maximum specific capacity 50 mAh cm(-2) over 100 cycles when cycled at 50 mA cm(2) current density for 1 h, such high current density operation is very scarce in the literature.