Highly Effective Solid Electrolyte Interphase-Forming Electrolyte Additive Enabling High Voltage Lithium-Ion Batteries

The electrochemical and thermal stabilities of commonly used LiPF<sub>6</sub>/organic carbonate-based electrolytes are still a bottleneck for the development of high energy density lithium-ion batteries (LIBs) operating at elevated cell voltage and elevated temperature. The use of intrinsic electrochemically stable electrolyte solvents, e.g. sulfones or dinitriles, has been reported as one approach to enable high voltage LIBs. However, the major challenge of these solvents is related to their poor reductive stability and lack of solid electrolyte interphase (SEI)-forming ability on the graphite electrode. Here, 3-methyl-1,4,2-dioxazol-5-one (MDO) is synthesized and investigated as new highly effective SEI-forming electrolyte additive which can sufficiently suppress electrolyte reduction and graphite exfoliation in propylene carbonate (PC)-based electrolytes. With the addition of only 2 wt % MDO, LiNi<sub>0.5</sub>Mn<sub>0.3</sub>Co<sub>0.2</sub>O<sub>2</sub> (NMC532)/graphite full cells containing a 1 M LiPF<sub>6</sub> in PC electrolyte reach a cycle life of more than 450 cycles while still having a capacity retention of 80%. In addition, MDO has proven to be oxidatively stable until potentials as high as 5.3 V vs Li/Li<sup>+</sup>. Further development of MDO and its derivatives as electrolyte additives is a step forward to high voltage stable electrolyte formulations based on alternative electrolyte solvents and high energy density LIBs.