Principles Determining the Voltages and Capacities of Electrochemical Cells

Abstract

In the earlier chapter we saw that the fundamental driving force across an electrochemical cell is the virtual chemical reaction that occurs if materials in the two electrodes are to react with each other. If the electrolyte is a perfect filter that allows the passage of ionic species, but not electrons, the cell voltage (when no current is passing through the system) is determined by the differences in the electrically neutral chemical compositions of the electrodes. The identity and properties of the electrolyte and the phenomena that occur at the electrode/electrolyte interfaces play no role. Likewise, it is the properties of the electrodes that determine the capacity of an electrochemical cell. These general principles are extended further in this chapter. Emphasis is placed on the equilibrium, or near-equilibrium, state. This addresses the ideal properties of systems, which provide the upper limits for various vital parameters.