Tris(pentafluoro)phenylborane electrolyte additive regulates the highly stable and uniform CEI membrane components to improve the high-voltage behaviors of NCM811 lithium-ion batteries

The introduction of 0.6 TPFPB to the baseline can not only facilitate the electrochemical performance of Half-cell, but also enhance the stabilize the properties of Full cells, meanwhile resulting in the formation of superior B- and F-CEI layer. • 1 TPFPB can enhance the cycling stability of the NCM811-Li half-cells or NCM811-graphite full-cells at high voltage. • Even at 60 ℃ and high voltage, the electrochemical stability of the TPFPB-containing NCM811-graphite full-cell had also been improved. • The CEI interfacial film of the cells containing TPFPB is more uniform and dense after cycling at 4.5 V. • The TPFPB molecules have the lowest LUMO values and higher HOMO values, which is able to prioritize redox reactions and participate in the formation of CEI films. • TPFPB has the lowest binding energy with Li + , which can reduce the de-solvation process of Li + , and have the highest binding energy with Co 4+ . Broadening the charging and discharging voltage window of high nickel cathode material NCM811 is the most expected method to improve the high specific energy density of batteries currently, yet the cathode-electrolyte interface (CEI) formed by the oxidized and decomposed products of carbonate-based electrolyte under high voltage are always so unsatisfied. Therefore, a voltage-stabilizer, TPFPB (Tris(pentafluoro)phenylborane), added into baseline electrolyte (1 M LiPF 6 in EC:EMC:DMC=1:1:1 vol%) to promote the electrochemical performance of the battery at 4.5 V. The results interpret that the TPFPB-contained NCM811-Li half-cells exhibit high specific capacity (167.10 mAh/g), excellent capacity retention rate (CRR) (75.37 %), and high rate performance (173.3 mAh/g at 5C) during 4.5 V. Meanwhile, through the analysis of the physical characterization techniques. the B- and F-rich interfacial layer, named as CEI film, existing at the interface between the cathode and the electrolyte, produced under 4.5 V, is superior, resulting in impeding the structural collapse of the cathode material and the continued dissolution of transition metal ions (TM n + ) from the cathode material, as well as, ameliorate the electrochemical polarization of the battery, ultimately, it can stabilize the electrochemical performance of the battery under high voltage. Therein, the present work elucidate a new and substantial approach to enhance the high-voltage performances of rich-Ni cathode materials.