An investigation of the structure of the active mass of the negative plate of lead—acid batteries

The formation of the negative plate of the lead—acid battery has been shown to take place in two stages. During the first stage, lead monoxide and basic lead sulphates are partially reduced to lead and partially react with H2SO4 to give PbSO4. These processes proceed at a neutral pH. SEM micrographs show that the lead crystals are interlinked in a skeletal primary network and that the PbSO4 crystals form on the surface of this structure. During the second stage, PbSO4 is reduced to lead under acidic conditions. Lead crystals are precipitated on the lead skeleton and form a secondary structure different from that of the primary skeleton. Upon discharge, current is generated mainly at the expense of the oxidation of the secondary structure lead crystals. The functions of the two types of structures have been identified. The primary (skeleton) structure serves as both a current collector and a mechanical support of the lead obtained during the second stage. The secondary (energetic) structure participates mainly in the charge—discharge processes of the negative plate.