Novel Pb alloys based composite foams containing hybrid pores produced by liquid metallurgy for lightweight batteries

High-quality novel Pb alloys based composite foams reinforced with fly ash cenospheres of different diameters in a variety of volume fractions were successfully synthesized by stir casting. Several crucial parameters such as wetting between the cenospheres and molten Pb alloy, volume fraction and size of the cenospheres, melt temperature, rate of cenosphere addition, stirring time and speed, foaming agent amount, foaming temperature and foaming time were optimized to produce high-quality composite foams. The microstructure of the composite foams revealed uniform cell distribution and size with mostly closed cell structure. The cells were measured to be of the size range of 290–430 μm. Microscopy and spectroscopy of the composite foams indicated that limited or no interfacial reaction products are formed between fly ash cenospheres and Pb alloys. The specific discharge electrical capacity of the composite foams was higher than those of the Pb alloys used in conventional Pb-acid batteries. Moreover, the weights of the composite foam electrodes were much lower than those of the conventional lead alloys, providing benefits in transportation applications. The cyclic voltammetric and galvanostatic polarization results indicated that the rates of oxidation of Pb into PbSO₄ in the composite foam were much lower than those in Pb-grids and the oxidation of the Pb in the positive and negative grids occurred at much lower voltage than that in composite foams.