Tripropyl borate was investigated as a low cost anion receptor to improve the performance of lithium-ion cells. The impact of tripropyl borate was examined using lithium-ion cells comprising a negative electrode of mesocarbon microbeads, a positive electrode of Li-1.1[Mn1/3Ni1/3Co1/3](0.9)O-2 and an LiPF6-based electrolyte. It was found that the performance of the cells was improved by adding a proper amount of tripropyl borate (<= 0.1 wt%) to the LiPF6-based electrolyte. However, a small amount of gas was observed from cells with high contents of tripropyl borate when cycled at 55 degrees C, and as a result, the performance of the cells deteriorated. (C) 2007 Published by Elsevier Ltd.