Lead-Acid Batteries

To date, the most widely used rechargeable battery is the lead-acid battery. Every automobile should have one with six cells. For a fully charged lead-acid battery, the positive electrode is made of PbO2 and the negative electrode is made of pure lead. The electrolyte is diluted sulfuric acid. After discharging, both the positive electrode and the negative electrode become PbSO4. Sulfuric acid is thus consumed. By measuring the specific gravity of the electrolyte, and thus the concentration of sulfuric acid, the state of discharging, thus the energy remaining, can be determined.

The electrochemistry is as follows. During discharging, at the positive electrode, PbO2 is reduced,

Подпись:Подпись:PbO2 + H2SO4 + 2e“ PbSO4 + 2OHA

At the negative electrode, lead is oxidized,

Pb + H2 SO4 -^ PbSO4 + 2H+ + 2eA

During charging, at the positive electrode, PbSO4 is oxidized,

At the negative electrode, PbSO4 is reduced,

PbSO4 + 2H+ + 2e – Pb + H2SO4. (12.21)

Lead is a heavy and toxic metal. Sulfuric acid is a dangerous liquid. The lifetime is short (300 cycles). Therefore, it is not suitable for portable devices and automobiles. However, since lead is intrinsically an inexpensive metal and can be recycled, the overall cost is low. It is expected that such batteries will still be extensively used in the foreseeable future, for example, as energy storage devices in remote areas or in the basements of residential buildings to store solar electricity.

Updated: August 23, 2015 — 6:33 pm