Tributylmethylphosphonium Bis(trifluoromethylsulfonyl)amide as an Effective Electrolyte Additive for Lithium Secondary Batteries

This work presents a study on an additive behavior of tributylmethylphosphonium bis(trifluoromethylsulfonyl)amide in lithium battery electrolytes. Electrolytic properties of a lithium hexafluorophosphate-based organic electrolyte mixed with phosphonium salt were examined in comparison with those of the corresponding ammonium-based electrolyte. The conductivity and viscosity of the mixed phosphonium electrolyte were similar to those of the corresponding ammonium electrolyte. However, the mixed phosphonium electrolyte gave relatively high voltammetric response and charge-discharge cycling efficiency to its containing lithium battery cell when compared to not only the corresponding ammonium electrolyte but also to the highly conductive organic electrolyte mixed with no additives. These results suggest that phosphonium salt is regarded as an effective electrolyte additive for lithium secondary batteries.