Conformal coating of PbO2 around boron doped diamond coated carbon felt positive electrode for stable and high-capacity operation of soluble lead redox flow battery

Abstract

The commercialization of soluble lead redox flow battery (SLRFB) is challenging due to its limited cycle life, lower areal capacity, Pb dendrite formation, and positive electrode corrosion. However, improvements are made to a certain extent by employing additives chemistry in terms of electrolyte modification. One of the major problems in SLRFB is carbon corrosion at higher current densities. Therefore, electrode modification, specifically on the positive side, is required to improve the cyclability of SLRFB further. There is minimal literature on this aspect.Given this, efforts are being made to enhance the electrochemical performance of SLRFB by employing a boron doped diamond (BDD) coated carbon felt (CF) as the positive electrode. The BDD coated CF electrode possesses a high surface area (7.1 m2g−1) compared to bare CF (0.6 m2g−1), i.e., BDD creates porous morphology, which enables a high mass transfer and hence reduces concentration polarisation. BDD coating on the CF delays the OER and reduces the overpotential for PbO2 deposition/dissolution. The cell with BDD coated CF electrode is successfully cycled for >300 charge/discharge cycles @ 40 mA cm−2 with average coulombic efficiency (CE), voltage efficiency (VE) and energy efficiency (EE) of 97 %, 71 % and 69 % respectively. The EE is improved by 8 % in the presence of BDD coated CF as compared to CF electrode. SLRFB cell with BDD coated CF electrode has reached 80 mAh cm−2 areal capacity.