Manganese–cobalt oxide as an effective bifunctional cathode for rechargeable Zn–air batteries with a compact quad-cell battery design

Abstract

Metal–air batteries, which are economical and ecological alternatives to Li-ion batteries, have become an important energy storage system. In this study, bimetallic oxides of widely accepted transition metal oxides like MnCo₂O₄ and NiFe₂O₄ have been explored to fabricate an efficient rechargeable Zn–air battery. The synthesis of these materials involves a single step direct decomposition of constituent metallic salts using polyvinyl pyrrolidone as a stabilizer cum nanostructure growth modifier by a simple open-air spray pyrolysis. The well characterized materials are used as cathodes in the assembly of a Zn–air battery that delivers a decent specific capacity of 780.1 mA h g⁻¹. It also offers long term charge–discharge for more than 900 cycles with a week-long break-free operational stability under a small voltage gap (0.65–0.73 V). Finally, a unique and compact quad-cell solid state battery design has been introduced using these cathodes and chemically modified anodes resembling the commercial lithium-ion mobile phone battery. This tiny portable Zn–air battery displays an open circuit potential (OCP) of 4.46 V.