PROTON INSERTION REACTIONS IN LAYERED TRANSITION-METAL OXIDES

The several different types of insertion reactions are briefly reviewe d, and an example, the so-called ''nickel electrode'', which actually involves a proton-driven reaction between Ni(OH)2 and NiOOH is discuss ed in some detail. This electrode has been widely used in battery tech nology, e.g. on the positive side of Cd/Ni, Zn/Ni, Fe/Ni, H-2/Ni, and metal hydride/Ni cells, in some cases for a very long time. It has rel atively rapid kinetics and exhibits unusually good cycling behavior. T his is directly related to its mechanism of operation, which involves a solid state proton insertion reaction. While the attractive properti es of this electrode have led to many investigations, there are still a number of aspects of its operation that are generally not understood , but can be explained in terms of the microstructural and thermodynam ic aspects of this insertion reaction.