Improvement in High-voltage Performance of Lithium-ion Batteries Using Bismaleimide as an Electrolyte Additive

• Bismaleimide is found as an additive to enhance electrolyte performance.
• Performance of LiCoO2/Li cells is improved while charging the cell up to 4.5 V.
• The electrolyte stability is improved to be 5.0 V after the addition.
• The surface film formation on cathode is crucial during first cycles.

N,N′-4,4′-diphenylmethane-bismaleimide (BMI) is attempted to enhance the high-voltage performance for lithium-ion batteries. When 0.1% (m/v) BMI is added into the control electrolyte, the high-voltage cycling performance of LiCoO2/Li cells is improved evidently while charging the cell up to 4.5 V rather than the conventional 4.2 V. Analysis of scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) demonstrate that an interface film forms on the cathode surface from BMI in electrolyte. AC impedance spectra and charge/discharge test were tested after incubation of the charged cell at 60 °C. Linear sweep voltammetry (LSV) is used to test the electrochemical stability window of the electrolyte with BMI addition. The results demonstrate that the improvement of high-voltage performance is attributed to the surface film on cathode. In addition, the BMI addition does not cause damage in conventional performance with 4.2 V electrochemical window. The BMI-containing electrolyte provides high-voltage cycling performance with 4.5 V electrochemical window, making LiCoO2 battery a simple and promising system for applications with high energy density.