Thiophene-2-carbonitrile: a bifunctional electrolyte additive to improve the performance of lithium-ion batteries

Thiophene-2-carbonitrile (CT) is used as an electrolyte additive to improve the cycle performance of Li/LiNi 0.5 Mn 1.5 O 4 (LNMO) cells. The effects of CT on the electrode interface and cycling performance of Li/LNMO cells are studied by electrochemical methods such as charge–discharge measurements, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and other characterization methods. Results show that CT can be oxidized before the electrolyte, forming a polythiophene protective film on the electrode surface, which improves the interphase stability of the electrode/electrolyte. The Li|1.0 M LiPF 6 -EC/EMC/DMC (1:1:1, v/v/v) |LNMO cell with 0.1 wt% CT shows a capacity retention of 91.2% after 300 cycles at a charge–discharge rate of 1 C between 3.5 and 4.95 V. The addition of thiophene-2-carbonitrile can significantly improve the cycle performance of Li/LiNi 0.5 Mn 1.5 O 4 .