The effect of electrolyte and additive concentration on zinc–nickel flow cell performance

The influence of zinc electrode substrate, electrolyte flow rate and current density on zinc-nickel flow cell performance

“…In many cases the performance of the cell rapidly becomes erratic, demonstrating poor and fluctuating coulombic efficiencies. This behaviour was reported in our previous work [11,43], the low coulombic efficiency during the initial cycles is due to the limited discharge capacity of the nickel electrode.…”

“…5a displays this trend in coulombic efficiency with flow rate and demonstrates that this also applies when no electrolyte additive is present. The coulombic efficiencies are consistently lower in the case of no additive, however, indicating the benefit of the addition of 15 mM TEAH electrolyte additive previously reported [11,43].…”

“…Where L is the length of the electrode in the streamwise direction and Sc is the Schmidt number. A diffusion coefficient of 2.25 x 10 -6 cm 2 s -1 has been employed, as determined through RDE experimentation reported in our previous work [43].…”

“…The graphite / PVDF composite (BMA5) selected in section 3.1 is employed as the zinc electrode substrate material, and an electrolyte velocity of 7 cm s -1 selected following the results in section 3.2.1. A current density of 20 mA cm -2 and a 15 mM concentration of TEAH additive is utilised in a 6 M KOH / 0.5 M ZnO electrolyte, this being identified as a promising addition to the electrolyte in our previous work [11,43].…”

“…Though there are some studies reporting these substrate materails for zinc electrode but often in the static battery system, the published papers on the effect of substrate materials on zinc electrode in flowing electrolyte environments has been rare. Then based on experimental data, the best performing substrate is utilised in a zinc-nickel flow cell under varying electrolyte flow rates and current densities, employing our preceding findings on electrolyte composition and concentration [11,43], with an aim of demonstrating stable and highly efficient operation of Zn-Ni RFB system.…”