The physico-chemical properties (T-g, T-c, T-m, T-dec, viscosity, conductivity), of the 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide [BMPyr][TFSI] room temperature ionic liquid are investigated. The influence of tantalum pentafluoride salt (TaF5) addition on the viscosity and the conductivity of the electrolyte is also reported as a function of temperature. The Arrhenius and several VTF equations are used to adjust the data and are all shown to provide satisfactory fits. Finally, the hole theory is applied to qualitatively explain the experimental changes of the viscosity and the conductivity. (C) 2016 Elsevier B.V. All rights reserved.