Ion Transport in Glyme- and Sulfolane-Based Highly Concentrated Electrolytes

Highly concentrated electrolytes (HCEs) have a similarity to ionic liquids (ILs) in high ionic nature, and indeed some of HECs are found to behave like an IL. HCEs have attracted considerable attention as prospective candidates for electrolyte materials in future lithium secondary batteries owing to their favorable properties both in the bulk and at the electrochemical interface. In this study, we highlight the effects of the solvent, counter anion, and diluent of HCEs on the Li+ ion coordination structure and transport properties (e. g., ionic conductivity and apparent Li+ ion transference number measured under anion-blocking conditions, tLiabc ${{t}_{{\rm L}{\rm i}}<^>{{\rm a}{\rm b}{\rm c}}}$ ). Our studies on dynamic ion correlations unveiled the difference in the ion conduction mechanisms in HCEs and their intimate relevance to tLiabc ${{t}_{{\rm L}{\rm i}}<^>{{\rm a}{\rm b}{\rm c}}}$ values. Our systematic analysis of the transport properties of HCEs also suggests the need for a compromise to simultaneously achieve high ionic conductivity and high tLiabc ${{t}_{{\rm L}{\rm i}}<^>{{\rm a}{\rm b}{\rm c}}}$ values.

Automated summary

Highly concentrated electrolytes (HCEs) have similar properties to ionic liquids (ILs) due to their high ionic nature, and some HCEs behave like ILs. HCEs have potential as electrolyte materials for future lithium secondary batteries due to their favorable properties both in bulk and at the electrochemical interface. This study investigates the effects of solvent, counter anion, and diluent of HCEs on the Li+ ion coordination structure and transport properties, revealing the difference in ion conduction mechanisms and their relationship to tLiabc values.