The impact of nano-scaled materials on advanced metal-air battery systems

Non-aqueous metal-air battery technology promises to provide electrochemical energy storage with the highest specific energy density. Such technology seems particularly advantageous being implemented in long-range electric vehicles. Up to now, almost all efforts in the field are focused on Li-air cells, and the air cathode is often considered as the most challenging component of such nonaqueous metal-air cell. The major challenges, which the research community is focusing on, are the limited ability of the air cathodes to accommodate a significant amount of metal oxide, high charge over-voltage, low cycle life and low power capabilities of the cell. By comprehensively reviewing the studies conducted so far, the aim of this extended review is to demonstrate that the implementation of nanoengineered materials (predominantly carbon-based nanomaterials, specifically, graphene and carbon nanotubes) is a promising approach to increase metal-air energy performance and, particularly, cathode ability to accommodate larger amount of metal oxide. The advantages of nanosized catalysts are also being heavily discussed; the employment of such catalysts is favorable once being implemented either onto a regular carbon black substrate, or along with nanoscaled substrate. The combination of nanoscaled supporting substrate with a proper catalyst manifests itself as a promising technology for decreasing the charge over-voltage, as well. The knowledge emerged from the vast studies on Li-air cell technology may be also applied to other non-aqueous metal-air battery technology systems.