Lithium-ion batteries that employ an electrolyte consisting of LiFSI and TMP are shown to have better cycle performance than conventional carbonate electrolyte batteries at elevated temperatures. Additionally, an inorganic alumina or silica separator also improves cycling performance at high temperatures. Half-cells of Li metal and Li2TiO3 were constructed with LiFSI/TMP electrolyte and inorganic separators and cycled at increasing temperatures. Their cycle performance was compared to batteries with the same anode and cathode material that were prepared with conventional components. Half-cells using either the novel electrolyte or inorganic separators were able to continue cycling at temperatures up to 80 ℃, long after the conventionally prepared batteries had failed. A cell with a combination of the LiFSI/TMP electrolyte and silica separator still showed 75% capacity retention after 10 cycles at 85 ℃ as well.