Lead-acid cell electromotive force

Gaston Plante combined a Pb/PbS04 with a Pb02/PbS04 electrode in sulfuric acid solution and obtained an electrochemical power source with high electromotive force. In 1860, he announced the invention of this power source as an electrochemical lead—acid cell of high power at a meeting of the French Academy of Sciences. 

So the electromotive force for the lead—acid cell can be expressed by ... 

Dependence of the Electromotive Force of a Lead—Acid Cell... 

The electromotive force of the cell with no ion transfer (AE ) is 2.040 V and it is determined on the basis of Gibbs free energies of the products and reagents participating in the reaction. The concentration of H2SO4 and the temperature of the cell will also impact the cell electromotive force. The open cell potential for lead-acid batteries is 2.10 to 2.13 V and the nominal voltage of a single practical lead-acid battery is 2 V. 

In this cell, the following independent phases must be considered platinum, silver, gaseous hydrogen, solid silver chloride electrolyte, and an aqueous solution of hydrogen chloride. In order to be able to determine the EMF of the cell, the leads must be made of the same material and thus, to simplify matters, a platinum lead must be connected to the silver electrode. It will be seen in the conclusion to this section that the electromotive force of a cell does not depend on the material from which the leads are made, so that the whole derivation could be carried out with different, e.g. copper, leads. In addition to Cl- and H30+ ions (further written as H+), the solution also contains Ag+ ions in a small concentration corresponding to a saturated solution of silver chloride in hydrochloric acid. Thus, the following scheme of the phases can be written (the parentheses enclose the species present in the given phase) ... 

Equation 5.12 indicates that sulfuric acid has a strong effect on the cell voltage of the lead-acid battery. Table 5.10 lists the calculated and measured open cell voltages (or electromotive force) as a function of sulfuric acid concentration [11]. It can be seen that the cell voltage increases with an increasing sulfuric acid concentration, which is exactly the tendency predicted by Equation 5.12. 

---