•Tripropyl borate (TPB) is able to stabilize the LiMn2O4/carbonate-based electrolyte interface.•A protective cathode film is formed on LiMn2O4 due to the preferential oxidation of TPB.•Unnecessary electrolyte decomposition products can be reduced by applying TPB.•The stabilized interface benefits the cyclic stability and avoids the self-discharge of LiMn2O4.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 (1.0 mol L−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.

•Charged LiNi1/3Co1/3Mn1/3O2 cathode to 4.5 V suffers serious self-discharge with a potential drop up to 1.0 V.•The mechanism involves the interaction between charged LiNi1/3Co1/3Mn1/3O2 and electrolyte without any limitation.•Self-discharge leads to the formation of over-lithiated compound combined with electrolyte decomposition products.The self-discharge mechanism of LiNi1/3Co1/3Mn1/3O2 cathode for lithium ion battery at high potential (4.5 V) has been understood through physical and electrochemical characterizations including charge/discharge test, electrochemical impedance spectroscopy (EIS), inductively coupled plasma atomic emission spectrometer (ICP-AES), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). It is found that the charged LiNi1/3Co1/3Mn1/3O2 cathode to 4.5 V suffers seriously self-discharge. After storage for 8 days, the potential of the cathode charged to 4.2 V remains stable, while that of the charged cathode to 4.5 V decreases from 4.5 to 1.0 V, The characterizations, from SEM, TEM, ICP-AES, and XRD, demonstrate that this self-discharge results from the interaction between charged LiNi1/3Co1/3Mn1/3O2 and electrolyte, which causes the dissolution of transition metals from LiNi1/3Co1/3Mn1/3O2 and the successive decomposition of the electrolyte.