The numerical value of the ionic conductivity of ILs does not reflect their ability to conduct Li + ions. Lithium transference number (T Li ) reflects the relative contributions of the charged species to the transfer of the total charge . The higher the value of the T Li , the greater will be the relative contribution to the charge transport. The T Li , i.e., the contribution to the ionic conductivity due to the Li + ion transport, can be approximated from D through an equation [151]: