Conjugated Polymers as Organic Electrodes for Metal-Air Batteries

As compared to the Li-S and Li-ion batteries, the metal-air batteries technology projects itself as a promising candidate for energy storage exhibiting large energy densities. At the cathode of the metal air battery, the reactions are mostly electrochemical processes engaging oxygen reduction and/or oxygen evolution. Oxygen electrocatalyst associated with the cathode plays a major role in determining the characteristics of a metal-air battery from the point of view of power density, rate capacity, the efficiency of capacity retention, and cycling stability. Different materials have been tested and were observed to efficiently improve the oxygen reduction and/or evolution, including conductive polymers, carbonaceous materials noble metals, alloys, nitrides, and oxides. Electrically conductive polymers (CPs), like polypyrrole, polyaniline, polythiophene, poly(3-methyl) thiophene, and poly(3,4-ethylene dioxythiophene, projects themselves as promising electrocatalysts which can effectively replace the noble metals in metal-air batteries. CPs possess both polymer and metal-like characteristics and have garnered large attention as a result of their redox properties, low cost, and improved electric conductivity. Even though the study of the CPs as electrocatalysts has preceded in the initial stages, it is largely restricted as a result of their comparatively smaller conductivity, and inferior efficiency. Vapor phase polymerization is considered as the recent most efficient process of chemical polymerization resulting in the synthesis of CPs with controllable morphology, large conductivity, and improved stability. For providing access to the current improvements in the field of metal-air batteries and realizing advancement in their development, this chapter comprehensively and systematically compares, summarizes, and discusses the state-of-the-art of aqueous and/or nonaqueous metal-air batteries.