Orthorhombic PbO Formation during the Discharge of Lead Acid Batteries PbO2 Active Mass

Abstract

Through TEM observations it was established that the lead acid battery PbO2 active mass crystals have a nonhomogeneous mass distribution and contain some defects in their crystal lattice. By electron diffraction analysis of the active mass agglomerates and individual crystals it was determined that β‐PbO2 is formed in the long and needle‐like crystals, while α‐PbO2 is formed in the short and slab‐like crystals often with a nonuniform shape. During plate discharge, besides the PbSO4 crystals, fine orthorhombic normalPbO false(normalort‐normalPbOfalse) crystals are formed as well. This fact is explained by the proton‐electron mechanism of PbO2 reduction. The difficult penetration of SO42− ions into the agglomerates' micropores causes alkalization of the solution in them and creates conditions for the formation of normalort‐normalPbO . Since the molar volumes of normalort‐normalPbO and PbO2 are almost equal, the transport of H+ ions and of water along the agglomerates' micropores is not impeded by the reduction PbO2→normalPbO . This reaction allows the PbO2 crystals in the agglomerates' interior to take part in the discharge process, thus a high coefficient of active mass utilization is achieved. When the discharge is stopped, normalort‐normalPbO reacts with H2SO4 forming PbSO4 .

Studies of the pulse charge of lead-acid batteries for PV applications

“…Considering the gel-crystal model of the lead dioxide, the particles building the positive active material consist of crystalline core of ␣-or ␤-PbO 2 while the surface, which is in contact with the H 2 SO 4 solution, is hydrated [40][41][42][43][44][45][46][47][48][49]. The hydrated parts consist of hydrated polymer chains of lead dioxide, denoted as PbO(OH) 2 (along these chains electrons ensure the electric connection between the electrolyte and the crystalline lead dioxide).…”

“…The appearance of a pseudo-inductive loop in the Nyquist plot clearly shows the proceeding of chemical processes in the mechanism of the positive plate discharge. According to the gel-crystal model of the lead dioxide the mechanism of the discharge of the positive plate can be presented as follows [40][41][42]44,51,52]:…”

“…The produced water molecules hydrate further the crystalline part of the lead dioxide (Reaction (4a)). The formed Pb(OH) 2 can be neutralized by more protons coming from the electrolyte or can decompose to orthorhombic-PbO [41] and water. The last processes are the diffusion of Pb 2+ towards the volume of the PAM pores and precipitation of PbSO 4 .…”

“…(4b). This reaction can proceed both on the surface and in the volume of the hydrated lead dioxide by solid-state diffusion of H + in the lead dioxide [61] especially when the surface is covered with Pb(OH) 2 or orthorhombic-PbO which is not electrochemically active [41].…”

Influence of Mg2+, Al3+, Co2+, Sn2+ and Sb3+ on the electrical performance of doped β-lead dioxide

“…According to Pavlov et al [3] during discharge of the positive battery plate, the reduction of PbO 2 and PbO(OH) 2 to PbSO 4 proceeds in two stages. The first is electrochemical and occurs in the bulk of the agglomerates and particles and gives Pb(OH) 2 .…”