Potentials and potential gradients are important in battery systems. The difference in the potentials of the two electrodes determines the voltage of electrochemical cells, being larger when they are charged, and smaller when they are discharged. On the other hand, potential gradients are the driving forces for the transport of species within electrodes.
All potentials (potential energies) are relative, rather than having absolute values. Since they cannot be measured on an absolute scale it is desirable to establish useful references against which they can be measured. This is not the case in electrochemistry alone, but is true for all disciplines. For example, when dealing with the potential energies of electrons in solids the solid-state physics community uses two different references, depending upon the problem being addressed. One is the potential energy of an electron at the bottom of the valence band in a solid, and the other is the so-called vacuum level, the energy of an isolated electron at an infinite distance from the solid in question. There is no universal relation between these two reference potentials, as the first is dependent upon the identity of the material involved, while the latter is not. This matter is discussed in Sect. 13.1.
KeywordsSolid Electrolyte Neutral Species Transference Number Electrochemical Potential Reversible Hydrogen Electrode
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