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 Nabased 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.