Through TEM observations it was established that PbO2 particles of the positive active mass are heterogeneous in mass distribution. Using electron micro‐micro‐diffraction it was found that PbO2 particles are built up of zones of α‐normaland/normalorβ‐PbO2 crystal structure with various orientation, and of amorphous zones. The latter are more transparent for the electron beam and are assumed to be hydrated. It was determined, through XPS (x‐ray photoelectron spectroscopy), that at least 30% of the PbO2 surface is hydrated. The changes in the crystal part of the active mass particles are followed during charge, discharge, open circuit, and overcharge. It was established that H2SO4 adsorption on the surface of the particles brings about an increase in their amorphous part. When the positive active mass is washed, its crystal part increases. It was also found that O2 causes amorphization of the particles, too. Oxygen atoms are sorbed by the PbO2 particles and increase their zones of disorder. A mechanism of formation of PbO2 particles during battery charge is proposed taking into account the processes of dehydration. OH− ions are assigned a considerable role in the interaction of the particles with the solution or with the neighboring particles.

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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 .

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