Batteries – Battery Types – Lead-Acid Battery | Negative Electrode

The negative plate consists of negative lead grid and negative active mass (NAM). The lead grid supports the NAM and it is a current conductor for the electricity generated in the NAM, as well as a conductor for the charge current. The lead grids are produced from different lead alloys—high or low lead-antimony alloys, or lead-calcium-tin alloys. NAM is a porous mass of sponge metallic lead, which is oxidized during the discharge to lead sulfate. During the charge this lead sulfate is reduced again to porous metallic lead. The NAM structure features two types of lead crystal organization—skeleton, built of interconnected crystals with irregular shapes and energetic structure, which consists of small sized individual Pb crystals grown over the skeleton. The capacity of the negative plate is determined by the energetic structure, which appears and disappears during each charge-discharge cycle. The end of the life of the negative plates is reached when the energetic structure is converted into skeleton. The reason for this conversion during the battery operation is the degradation of the expander, due to the oxygen attack and high temperature. The sulfation of the NAM is the other main reason for battery failure.