Challenges of today for Na-based batteries of the future: From materials to cell metrics

Several emerging battery technologies are currently on endeavour to take a share of the dominant position taken by Li-ion batteries in the field of energy storage. Among them, sodium-based batteries offer a combination of attractive properties i.e., low cost, sustainable precursors and secure raw material supplies. Na-based batteries include related battery concepts, such as Na-ion, all solid-state Na batteries, Na/O2 and Na/S, that differ in key components and in redox chemistry, and therefore result in separate challenges and metrics. Na-ion batteries represent an attractive solution which is almost ready to challenge Li-ion technology in certain applications; the other cell concepts represent a more disruptive innovation, with a higher performance gain, provided that major hurdles are overcome. The present review aims at highlighting the most promising materials in the field of Na-based batteries and challenges needed to be addressed to make this technology industrially appealing, by providing an in-depth analysis of performance metrics from recent literature. To this end, half-cell reported metrics have been extrapolated to full cell level for the more mature Na-ion technology to provide a fair comparison with existing technologies.