The formation of lead dendrites easily causes short circuiting during charging in lead methanesulfonate flow batteries. In this work, tin(II) methanesulfonate is used as an additive to improve the surface morphology of the lead layer. It has been found that the lead layer is smooth and compact in an electrolyte of 1.5 M Pb(CH3SO3)2 + 1.0 M CH3SO3H with 8 m mol l−1 of additive. During charging, lead and tin can be co-deposited to increase the density of the nucleus number and decrease the diffusion rate of Pb2+. The type of nucleation of lead is changed from three-dimensional instantaneous nucleation to three-dimensional progressive nucleation in the process controlled by the diffusion of Pb2+. This is beneficial for the formation of small-sized lead particles, leveling the morphology of the lead layer, and inhibiting the formation of lead dendrite. The energy efficiency of the flow cell is around 80%, and 380 cycles are achieved in the electrolyte of 1.5 M Pb(CH3SO3)2 + 1.0 M CH3SO3H with 8 mmol l−1 of tin(II) methanesulfonate.
Lead-carbon composites are effective additives in lead-carbon negative electrode due to their beneficial influences on the performance of negative electrode of lead-carbon battery operated under high-rate partial-state-of-charge duty. In this paper, to further investigate the effects of the lead monoxide (PbO) deposition ratio of activated carbon (AC) based lead-carbon composite additives, we prepared lead-carbon composites (termed as PbO@AC) with different controllable PbO deposition ratios successfully through a facile coupled chemical-deposition/pyrolysis strategy. The hydrogen evolution reaction of AC and lead-carbon electrode is effectively inhibited through the deposition of PbO. PbO@AC-2 sample with a PbO deposition ratio of 9.9% exhibits the best electrochemical performances when used as the negative electrode additive. The evidently enhanced performances of lead-carbon electrodes, such as rate capability and cycling life under high-rate partial-state-of-charge operation, indicate the beneficial effects of deposited PbO. Particularly, PbO@AC-2 battery exhibits the longest cycling life of more than 10,000 cycles which is 1.956 times that of lead-carbon battery with AC as the negative electrode additive. The improved performances of lead-carbon electrode enabled by PbO@AC-2 originate from both the inhibition of hydrogen evolution reaction and the enhanced electrochemical reversibility of the Pb/PbSO 4 redox reaction . PbO@AC-2 exhibits the best trade-off between inhibiting hydrogen evolution and building extra electrochemical active area for the deposition of Pb.
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