Methyl p-toluenesulfonate as A Highly Effective Film-Forming Additive to Improve the Performance of A High-Voltage LiMn2O4 Cathode

The current study explores the film forming ability of a new additive Methyl ptoluene sulfonate (MPTS) on the LiMn2O4 2 O 4 (LMO) electrode and its effect on the electrochemical characteristics of lithium-ion battery. Based on the density functional theory analysis of the ionization energy (AIE) of MPTS and carbonate solvents, it was found that MPTS possesses the lowest AIE at 693.2 kJ/mol, suggesting a higher susceptibility to oxidation compared to the electrolyte solvents. Electrochemical and physicochemical analyses including linear sweep voltammetry, electrochemical impedance spectroscopy, field-emission scanning microscopy, indicated that the electrolyte with MPTS is prone to create a protective film with low impedance on the cathode electrode, which enhances the stability of the electrolyte and electrode upon battery cycling. The LMO/Li half-cell with 1.5% MPTS exhibits outstanding cyclic performance, retaining 90.53% of its capacity after 100 cycles, in comparison to 81.84% for the pristine electrolyte at high voltage. This improvement is because of the creation of a protective sulfur-containing layer on the cathode surface, which effectively prevents electrolyte degradation, reduces interfacial impedance, and enhances overall battery performance.