A simple boron-containing molecule, tripropyl borate (TPB), is used as an electrolyte additive to stabilize the interface between spinel lithium manganese oxide (LiMn2O4) and carbonate-based electrolyte under elevated temperature. Electrochemical measurements indicate that the cyclic stability of LiMn2O4 electrode can be significantly improved by TPB. The capacity retention of LiMn2O4 at 1C after 200 cycles under 55°C is improved from 47% to 74% by adding 3% TPB into a standard electrolyte (1.0molL−1 LiPF6-EC/EMC/DEC (3/5/2, in weight)). Most importantly, the self-discharge of LiMn2O4 under 55°C, which takes place dramatically in the standard electrolyte, is effectively suppressed in 3% TPB-containing electrolyte. Theoretical calculations and physical characterizations demonstrate that a protective cathode electrolyte interface (CEI) film is formed on LiMn2O4 from the preferential oxidation of TPB, which suppresses the oxidation decomposition of the standard electrolyte. Due to the incorporation of boron, the CEI film formed from TPB is beneficial to the rate capability of LiMn2O4.