The crystal structures of lead dioxides from the positive plate of the lead/acid battery

Abstract

Full profile neutron powder diffraction structure refinements have been performed on electrolytically- and chemically-prepared varieties of the dimorphs of lead dioxide, the primary constituents in the charged positive plate of the lead/acid battery. Electrolytic samples of α-PbO 2 (columbite related structure) contain significant amounts of noncrystalline material, have severe cation disorder, and display evidence of severe lattice strain and unit cell incoherency in the [010] direction. On the other hand, chemically-prepared varieties of α-PbO 2 are more highly crystalline, are essentially stoichiometric, and are well ordered. Electrolytic samples of β-PbO 2 (rutile structure) from both new and used battery plates also contain more noncrystalline material than chemically-prepared forms, but all varieties are near-stoichiometric, well ordered, and structurally indistinguishable insofar as coherent neutron diffraction is concerned. Given that positive plates cycled under normal conditions for long periods of time consist primarily of the beta form of lead dioxide, the onset of battery failure is therefore not manifest in the long range crystal structure of this dioxide. In view of the high proportion of noncrystalline material present in electrolytic samples of PbO 2, property changes previously associated with loss of crystalline dioxide activity may relate instead to the “amorphous” component of the positive plate mass.