Ionic liquids, electrolyte solutions including the ionic liquids, and energy storage devices including the ionic liquids

Abstract

An ionic liquid including a phosphazene compound that has a plurality of phosphorus-nitrogen units and at least one pendant group bonded to each phosphorus atom of the plurality of phosphorus-nitrogen units. One pendant group of the at least one pendant group comprises a positively charged pendant group. Additional embodiments of ionic liquids are disclosed, as are electrolyte solutions and energy storage devices including the embodiments of the ionic liquid.

What is claimed is: 
     
         1 . An energy storage device, comprising:
 a positive electrode, a negative electrode, a separator between the positive electrode and the negative electrode, and an electrolyte solution, the electrolyte solution comprising:
 at least one solvent; 
 at least one lithium salt; and 
 an ionic phosphazene compound comprising a plurality of phosphorus-nitrogen units, the ionic phosphazene compound comprising:
 a positively charged pendant group bonded to at least one of the phosphorus atoms of the plurality of phosphorus-nitrogen units; 
 a positively charged nitrogen atom on one of the plurality of phosphorus-nitrogen units; or 
 a positively charged phosphorus atom on one of the plurality of phosphorus-nitrogen units.