LiTDI: A Highly Efficient Additive for Electrolyte Stabilization in Lithium-Ion Batteries

The poor stability of LiPF6-based electrolytes has always been a bottleneck for conventional lithium-ion batteries. The presence of inevitable trace amounts of moisture and the operation of batteries at elevated temperatures are particularly detrimental to electrolyte stability. Here, lithium 2-trifluoromethyl-4,5-dicyanoimidazole (LiTDI) is investigated as a moisture-scavenging electrolyte additive and can sufficiently suppress the hydrolysis of LiPF6. With 2 wt % LiTDI, no LiPF6 degradation can be detected after storage for 35 days, even though the water level in the electrolyte is enriched by 2000 ppm. An improved thermal stability is also obtained by employing the LiTDI additive, and the moisture-scavenging mechanism is discussed. The beneficial effects of the LiTDI additive on battery performance are demonstrated by the enhanced capacity retention of both the LiNi1/3Mn1/3Co1/3O2 (NMC)/Li and NMC/graphite cells at 55 °C. In particular, the increase in cell voltage hysteresis is greatly hindered when LiTDI is presented in the electrolyte. Further development of the LiTDI additive may allow the improvement of elevated-temperature batteries, as well as energy savings by reducing the amount of effort necessary for dehydration of battery components.