Enhanced cycle life of lead-acid battery using graphene as a sulfation suppression additive in negative active material

In this article, we report the addition of graphene (Gr) to negative active materials (NAM) of lead-acid batteries (LABs) for sulfation suppression and cycle-life extension. Our experimental results show that with an addition of only a fraction of a percent of Gr, the partial state of charge (PSoC) cycle life is significantly improved by more than 140% from 7078 to 17 157 cycles. The particle size on a charged Pb-graphene (PbG) plate after the PSoC test is also found to be reduced by around 25% when compare with a Pb plate. Charge and discharge densities measurements from the cyclic voltammetry (CV) test show an enhancement with the addition of Gr, indicating an improvement in the reversibility reaction of PbSO₄. An electrochemical model, which takes into account of reduced interfacial resistance, improved charge transfer and enhanced electroactive surface area, is proposed to elucidate the role of Gr throughout the course of a PSoC cycle test. It is demonstrated that experimental results are aligned with our proposed model with enhanced cycle life performance, where PbG plate maintains a higher electroactive surface area for adsorption and desorption of Pb²⁺ ions at the interface between active material and electrolyte occurs in parallel to reduced charge transfer.