Evolution of β-PbO2 crystal structure with cycle life during rapid and conventional charging of lead acid batteries using neutron diffraction

Time of flight neutron diffraction of active material from lead acid batteries has characterized changes in crystallographic parameters of PbO₂ from initial formation to battery failure for both rapid and conventional charging. PbO₂ is nonstoichiometric and evolves from near Pb_0.92O₂ in initial formation to Pb_0.96O₂. The a₀/c₀ of the tetragonal β-PbO₂ structure likewise shows a detectable decrease with cycle life. Displacement parameters for Pb show nearly identical trends for both rapid and conventional charging over the life of the active material. The changes in the shape of the Pb displacement ellipsoid may be correlated with Pb occupancy and based on other published data may reflect changes in noncrystallographic H content of the β-PbO₂ structure. These crystallographic changes do not necessarily cause capacity loss