Binary Electrodes Under Equilibrium or Near-Equilibrium Conditions

The theoretical basis for understanding and predicting the composition-dependence of the potentials, as well as the capacities, of both binary (two element) and ternary (three element) alloys has now been established. The relevant principles of binary systems are discussed in this chapter. Ternary systems are treated in the next chapter.

Under equilibrium and near-equilibrium conditions, these important practical parameters are directly related to the thermodynamic properties and compositional ranges of the pertinent phases in the respective phase diagrams. Their behavior can be understood under dynamic conditions by simple deviations from such equilibrium conditions. In other cases, however, metastable phases may be present in the microstructure of an electrode whose properties are considerably different from those of absolutely-stable phases. The influence of metastable microstructures is discussed in a later chapter. In addition, it is possible that the compositional changes occurring in an electrode during the operation of an electrochemical cell can cause amorphization of its structure. This is also discussed later.