2,3,4,5,6-Pentafluorophenyl Methanesulfonate as a Versatile Electrolyte Additive Matches LiNi_0.5Co_0.2Mn_0.3O₂/Graphite Batteries Working in a Wide-Temperature Range

An electrolyte using 2,3,4,5,6-pentafluorophenyl methanesulfonate (PFPMS) as a versatile additive is investigated through calculating the molecular orbital energies of additives and solvents and designing the electrolyte composition, and the comparative performances of LiNi_0.5Co_0.2Mn_0.3O₂/graphite cells operating in a wide-temperature range are improved. It is revealed that PFPMS can form interfacial films on both the cathode and anode surfaces, resulting in a decrease of the cell impedance and the side reactions between the active materials and electrolyte. Compared to the cells without additive of 74.9% and those with vinylene carbonate (VC) of 76.7%, the cycling retention of the cell with 1.0 wt % PFPMS reaches 91.7% after 400 cycles at room temperature. In particular, for the high-temperature storage at 60 °C for 7 d, the cell containing 1.0 wt % PFPMS exhibits optimal capacity retention of 86.3% and capacity recovery of 90.6%; for the low-temperature discharge capacity retention at -20 °C, the cell with 1.0 wt % PFPMS maintains at 66.3% at 0.5 C, while for the cells without additive and containing 1.0 wt % VC, their retention values are 55.0 and 62.1%, respectively. The excellent cycling, wide-temperature practicability, and rate capability of the cells with PFPMS demonstrate that the electrolyte with PFPMS additive is promising for applications in LiNi_0.5Co_0.2Mn_0.3O₂/graphite batteries.