Charging lithium polysulfides by cationic lithium nitrate species for low-temperature lithium−sulfur batteries

Ether based electrolyte exhibits extraordinarily high lithium-ion conductivity at low temperature due to inherent low melting point and strong coordination strength of ether solvents. However, such fascinating properties do not bring desired low-temperature electrochemical performances of lithium–sulfur (Li–S) batteries. One of the critical challenges is the tendency to generate massive Li polysulfide (LiPS) clusters at sub-zero temperature, which hinders mass transport and retards polysulfide lithiation during discharge. Declustering LiPSs at low temperature is a prerequisite endeavour to expedite the reaction kinetics. Lithium nitrate (LiNO₃) has been ubiquitously employed to protect Li anode, while its strong coordination strength to break LiPS clusters and generate charged LiPS species remains elusive. This work demonstrates the importance of cationic Li_δ[LiNO₃]^δ+ species that can facilitate the formation of charged LiPSs. Such charged LiPSs are, experimentally and theoretically, proved to promote the LiPS conversion kinetics at low temperature. It is expected to enrich LiPS solvation fundamentals and shed light on unique neutral molecule to charge LiPSs for facile LiPS conversion.