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

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.