Tetraethylthiophene-2,5-diylbismethylphosphonate: A Novel Electrolyte Additive for High-Voltage Batteries.

In this work, a novel high-voltage electrolyte additive, tetraethylthiophene-2,5-diylbismethylphosphonate (TTD), was synthesized, and the influence of TTD on the electrolyte and its electrochemical performance under different voltages were studied by changing the content of the TTD additive. The results showed that the TTD additive significantly improved the capacity, cycle stability, and rate capability of batteries when charging/discharging at high voltages. After adding 1 % TTD to the basic electrolyte, the capacity retention rate of batteries after 200 cycles at 4.2, 4.3, 4.4, and 4.5 V increased by 20.8, 18.3, 50, and 31.9 %, respectively. In addition, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) results showed that TTD could effectively inhibit the decomposition of the electrolyte and participate in the formation of a uniform, thin, and stable cathode electrolyte interphase (CEI) film on the electrode surface, thereby effectively inhibiting the side reaction between the electrolyte decomposition product and the CEI membrane, and finally improving the high-voltage performance of the battery. The TTD additive may provide a cost-effective solution for high-performance high-voltage electrolytes.