A new ionic liquid-based electrolyte for lithium batteries operating at an elevated temperature of 55°C was prepared by combining N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide (PP13TFSI) and lithium bis(fluorosulfonyl)imide (LiFSI). The electrolyte does not contain volatile organic components and is thermally stable (up to 285°C) and ionically conductive (2.6mScm−1 at 55°C). The 0.7m LiFSI–PP13TFSI electrolyte has been shown to work effectively with a graphite anode due to the ability of the FSI anions to create a stable solid electrolyte interface on graphite. A discharge capacity of 340–345mAhg−1 was achieved at C/10 rate with a coulombic efficiency of 97–98%. The electrolyte is also compatible with LiCo1/3Mn1/3Ni1/3O2 (NMC) cathode material. At the C/10 rate, we achieved a discharge capacity of 160mAhg−1. The coulombic efficiency remains high above 99%.