Sulfur Dioxide and Sulfolane as Additives in Organic Electrolytes to Develop Room-Temperature Sodium Batteries

Sodium metal anodes have attracted great attention for the development of a next generation of high-energy batteries because of their high theoretical capacity (1166 mAh·g−1), low redox potential (−2.71 V vs. SHE), and abundance. However, sodium reacts with most of the liquid electrolytes described to date and it has the shortcoming of dendrite formation during sodium deposition. Several strategies have been proposed to overcome these issues, including the incorporation of electrolyte additives. This work reports on the use of SO2 and sulfolane as additives in organic electrolytes to modify the sodium–electrolyte interphase, making the sodium plating/stripping process more robust. Not only is the process more stable in the case of sodium metal anodes, but also the use of copper substrates is enabled. In fact, high-quality sodium films on copper have been attained by adding small mole fractions of the additives, which paves the way for the development of anode-free batteries. In a general vein, this work stresses the importance of researching on compatible and cost-effective additives that can be easily implemented in practice.This research was partially funded by the Ministerio de Ciencia e Innovación/Agencia Estatal de Investigación/Fondos FEDER through project RTI2018-102061-B-I00 and by the Generalitat Valenciana through project PROMETEO/2020/089