With respect towards Li dendrite suppression, multiple approaches have been utilized in literature. The use of solid electrolytes as a mechanical barrier, or the use of specific organic solvent-based electrolytes (inclusive of alterations in cations/anions of salts) which control the properties of the solid-electrolyte interface (SEI) are noted observations5. Amongst the various classes of Li battery electrolytes developed to date, ionic liquids (ILs) have been utilized as electrolytes which can facilitate enhanced Li cycling efficiencies and favorable Li plating morphologies while being inherently non-volatile/non-flammable alternatives to commercially available organic electrolytes. Hence, ILs offer a potentially safer alternative to commercially available organic electrolytes1-3,5. Apart from non-volatility, ILs have demonstrated relatively higher decomposition temperatures to organic-solvent based electrolytes, high ionic conductivities and wider electrochemical windows6. Nonetheless, despite their noted advantages, ionic liquids do also display low conductivity and limited material options which exist as liquids at room temperature7. Within the ILs published to date, combinations of various cations (Imidazolium, Pyrrolidinium, Piperidinium, Ammonium, etc.) and anions (TFSI, FSI, BF4, DCA, etc.) have been presented – each with its own distinct advantage1. In all, through the capability to combine various cations and anions; the use of such ILs could produce a simpler and perhaps more uniform SEI, resulting in the improved cycling behaviors reported to date3,8-10.
However, to our knowledge, none of these reports have shown the capability to sustain dendrite-free Li growth upon application of practical cycling rates, and allow for stable cycling in the presence of water11,12. Here, we introduce a new class of ILs capable of sustaining dendrite-free Li morphologies at practical cycling rates. Further, we study the specific interactions of these ILs with Li metal, in the absence and presence of water in the electrolyte. Electrochemical results, along with fundamental analytical analyses will be presented and discussed.
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