Di(methylsulfonyl) Ethane: New Electrolyte Additive for Enhancing LiCoO₂/Electrolyte Interface Stability under High Voltage

In the work reported in this article, di(methylsulfonyl) ethane (DMSE) was examined as a neoteric S-related electrolyte additive to elevate LiCoO2/electrolyte interfacial stability at 3.0–4.5 V (compared to Li/Li+). DMSE, when added to the electrolyte, can significantly enhance the high-voltage performance of LiCoO2/graphite cells. Meanwhile, capacity retention increased from 20.8 to 66.5% after 100 cycles owing to the adjunction of 0.5 wt % DMSE to the electrolyte (carbonate solvents and lithium salt). The density functional theory calculation results indicate that DMSE has a greater highest occupied molecular orbital energy in contrast to ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. Differential capacity versus voltage analysis and linear sweep voltammetry result indicate that DMSE is decomposed in preference to the electrolyte solvents. DMSE’s effects are distinguished by electrochemical impedance spectroscopy, Fourier transform infrared spectroscopy, X-ray-diffraction spectroscopy, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The outcomes indicate that the enhanced cycling performance is attributed to the involvement of DMSE in the generation of a thinner film on LiCoO2, which results in lower interfacial impedance and it protects the electrolyte from decomposition at high voltage.