Development of High-Performance Lead-Acid Batteries through Electrode and Electrolyte Additives
This presentation reports mitigation strategies for addressing the issues of sulfation and grid corrosion in lead–acid batteries through electrode and electrolyte additives and surface modifications of the plate and grid. Various types of carbon and metal oxide composites, such as C–SnO2, boron doped graphene and TiO2-reduced graphene oxide (RGO), have been successfully added to negative active-material (NAM) to reduce the problem of sulfation. The C-based additives have been found to provide greater conductivity, to control PbSO4 growth, to act as a capacitor, and to improve the overall electrochemical performance of lead–acid cells. It has been found that a C–SnO2/TiO2 composite occupies the pores of NAM, accesses electrolyte in the interior of the plate, restricts the PbSO4 growth and reduces hydrogen evolution, which thereby enhances charge-acceptance, high C-rate capacity and high-rate partial state-of-charge (HRPSoC) cycles. A surface modification strategy by depositing poly(3,4-ethylenedioxythiophene) (PEDOT) on the surface of the negative plate has been also studied to address the issue of sulfation. Lead–acid cells assembled with PEDOT-coated negative electrodes showed ~25 % increase in initial discharge capacity, excellent cycle performance at the C/5 rate, lower impedance, reduced hydrogen evolution, capacitive behaviour and a boost in charge-acceptance in comparison with conventional cells.
To address the issue of positive grid corrosion, a conducting polymer coating of polypyrrole (PPY) on the positive grid has been developed. The coating increases the corrosion resistance, inhibits the oxygen evolution rate, acts as an adhesion layer that helps to improve conductivity between the active mass layer and the grid, and reduces the formation of a passivation layer (PbO, PbSO4) on the surface of grid that, in turn, enhances capacity retention during prolonged cycling.
Meanwhile, a Na2EDTA chelating agent has been investigated as an electrolyte additive to reduce the issue of sulfation by controlling the size of PbSO4 crystal growth.
Associate Professor, Indian Institute of Technology Hyderabad, India
Surendra Kumar Martha graduated in 2006 from the Solid State and Structural Chemistry Unit of the Indian Institute of Science in Bangalore, India. He worked as a Postdoctoral Research Associate at the Oak Ridge National Laboratory, Tennessee, USA, and at the Bar-Ilan University in Israel. Surendra is now an Associate Professor in the Department of Chemistry at the Indian Institute of Technology in Hyderabad.