Non-Aqueous Electrolytes for Sodium-Ion Batteries: Challenges and Prospects Towards Commercialization

Integration of Na-ion batteries (NIBs) as a complementary energy storage device to the presently dominating Li-ion battery (LIB) technology is a must, considering the cost and sustainability issues of lithium. However, despite the important laboratory-scale achievements concerning Na-ion electrodes and electrolytes, the improvements needed for realizing battery devices to meet users demands are being relatively slow. More specifically, the development of suitable electrolytes remains as the bottleneck that restrains this technology from meeting the commercial requirements, hence defining a future challenge. This review explains the design strategies in use for NIB electrolytes with a special emphasis on intrinsic differences between Li- and Na-ion chemistries, which are at the origin of difficulties associated with the discovery of optimum electrolytes for NIBs. We highlight the key requirements that an electrolyte must satisfy and related experimental techniques that could be used for quick screening of NIB electrolytes in laboratory-scale for exploiting in commercial NIB devices.