Constructing a universal artificial polymeric ionic liquid interfacial film for graphite anode and High-Voltage cathode

Abstract

The electrode/electrolyte interface stability is crucial for the cycling stability and the safety of lithium-ion batteries. Construction of a superior interfacial film is of vital significance to promote battery performance. For this purpose, we develop a universal polymeric ionic liquid (PIL) as an artificial interfacial film to suppress the electrolyte decomposition on the electrode surface. The PIL interfacial film shows outstanding properties such as high mechanical modulus, superb shape compliance, excellent electrochemical stability. Moreover, abundant cations in the PIL matrix can combine PF6− and carbonate solvents by Coulombic interaction and promote Li+ migration. Hence, the modified graphite anode with PIL layer achieves an improved cyclability with 89% of capacity retention after 150 cycles at 1C with a high initial Coulombic efficiency (96%), which is higher than that of the bare graphite anode. Meanwhile, the modified LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode also maintains 90% of initial capacity (186 mAh/g) after 120 cycles at high temperature (55 °C) and high voltage (cut-off charging voltage of 4.5 V), much better than that of the bare NCM622||Li half-cell (only 2.7%).