Effects of additives on the morphology and stability of PbO2 films electrodeposited on nickel substrate for light weight lead-acid battery application

Abstract

Abstract This work investigated the effects of NaF and sodium dodecyl sulfate (SDS) on the morphology and stability of electrodeposited PbO2 film. The PbO2 electrodeposition was conducted on the Ni-substrate by galvanostatic anodic deposition in acidic Pb(NO3)2 solution to be employed as a positive electrode in the lightweight lead-acid battery. The stability and electrochemical properties of the film were investigated by cyclic voltammetry in 4.7 mol L−1 H2SO4. Phase constituents and microstructures of the deposited PbO2 before and after cycling was characterized using atomic force microscope (AFM), scanning electron microscope (SEM), and X-ray diffraction spectroscopy. Experimental results show that current density and the concentration of Pb(NO3)2 and NaF positively affected the current efficiency for PbO2 deposition. A mixed-phase (ɑ-PbO2 and β-PbO2), relatively less stable (persist up to 80 cycles) and larger-grained deposit with low charge-discharge density was produced in the absence of SDS. The addition of a small amount of SDS in the electrolyte increased the proportion of β-PbO2 having compact and small-grained crystals resulting in the improvement of the stability (persist up to 300 cycles) and charge-discharge density of the PbO2 film in the battery environment. The density functional theory (DFT) calculation confirmed that the higher binding energy of H2O to the defected PbO2 sites caused by high cycling was mainly responsible for enormous oxygen evolution which eventually resulted in the failure of the positive electrode and water loss of the battery during operation.