Effect of depth of discharge on morphology and size of sulfate particles in VRLA battery electrodes

Abstract

Lead-acid battery is widely used as automotive starting, lighting, and ignition (SLI) batteries. Due to economic of the production and rather simple manufacturing process, the lead-acid battery remains as a feasible type of battery for renewable energy storage application. However, the cycle life of battery is limited to several hundreds of cycles depends on operational conditions. The aim of the present work was to study the effect of depth of discharge (DoD) on the cycle life of a battery which is relevant for battery in renewable energy applications. The battery samples used in the present work were prepared from commercial SLI battery. The sample was cycled in 2 electrode systems at constant current charging and discharging procedure in an Autolab PGSTAT 302 N at different DoD, i.e. 40%, 60%, and 80% for 80 cycles. Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD) were used to characterize active materials after the cycle life test. The cycle test showed a significant formation of lead sulfate (PbSO4) on the negative and positive electrode and the highest level was found at 80% DoD. The sulfation decreased as DoD was reduced. Excessive lead sulfate (PbSO4) formation was found on the negative electrode at all the DoD regimes. This result indicates that decreasing cycle life of valve regulated lead acid (VRLA) battery is mostly caused by sulfation on the negative electrode.