High-voltage LiNi0.4Co0.4Mn0.2O2/graphite pouch battery cycled at 4.5 V with a LiDFP-based electrolyte

Increasing the charging cutoff voltage is an effective method for improving the energy density of lithium-ion batteries. However, the conventional carbonate-based electrolyte with LiPF 6 is unstable when the end-of-charge voltage up to 4.5 V (vs. Li/Li + ), resulting in poor cycling stability of LIBs. In this work, when 1.0 wt% LiDFP is added into the conventional electrolyte for LiNi 0.4 Co 0.4 Mn 0.2 O 2 /graphite pouch cells, the capacity retention of the cell is significantly improved from 22.9 to 87.6% after 100 cycles, even a high capacity retention of 81.0% is maintained after 200 cycles. The results of spectroscopic and electrochemical techniques indicate that the passivation film induced by LiDFP can be formed simultaneously at both cathode and anode surfaces. The improvement of cell high-voltage performance can be credited to the addition of LiDFP, which effectively inhibited the dissolution of transition metals and the side reaction of electrolyte on the cathode and anode surfaces.