MgCo2O4-based electrode materials for electrochemical energy storage and conversion: a comprehensive review

In the past few years, electrochemical energy storage (EES) systems including rechargeable metal-ion batteries and supercapacitors have received increasing attention because of their wide applications in public wearable and portable consumer electronics, electronic skin, and hybrid electric vehicles. Especially, hybrid supercapacitors (HSCs) or asymmetric supercapacitors (ASCs) assembled with battery-type and capacitive-type electrodes usually exhibit superior electrochemical performance by combining the advantages of high capacity from battery-type cathodes and broad voltage windows from electric double-layer capacitive anodes. However, the sluggish ion/electron diffusion and inferior structural stability of the battery-grade electrode materials may limit their actual applications in some fields requiring high-rate and long-life energy storage and conversion. Much effort has been focused on the development of cathode materials with high-performance. As a spinel binary metal cobaltite, MgCo2O4 has attracted extensive attention in EES because of its high theoretical capacity, relatively better environmental friendliness and the abundant natural reserves of magnesium. In this work, current research progress regarding the synthetic strategies for powdered MgCo2O4, binder-free hetero-structure of MgCo2O4 on the current collector, and MgCo2O4-based composites and their applications in supercapacitors, Li-ion batteries, Mg-ion batteries, and some other rechargeable ion batteries is reviewed in detail. Finally, we put forward some conclusive remarks and perspectives on the future development of metal-ion batteries and supercapacitors with outstanding performance. Our intention is to provide some clues for the build-up of high-rate and long-life energy storage systems as well as guidance for future related research on other binary metal cobaltites in energy storage devices.