Improving long-term cyclic performance of LiNi0.8Co0.15Al0.05O2 cathode by introducing a film forming additive

Layered structure Ni-rich LiNi0.8Co0.15Al0.05O2 cathode has been considered as a higher energy density candidate, but the problems of poor interface stability and cyclic performance restrain its further application. Herein, a functional vinyl (-C=C-) group allylboronic acid pinacol ester (ABAPE) is introduced as a film forming additive. Linear sweep voltammetry test shows ABAPE could be oxidized prior to blank electrolyte on the cathode and prevent the electrolyte decomposition. The LiNi0.8Co0.15Al0.05O2/graphite pouch cells which contained 1.5% ABAPE shows remarkable cyclic performance of 87.7% capacity retention compared with 71.8% of blank electrolyte after 500 cycles. This is attributed to the protective surface layer which prevents the further decomposition of electrolyte and transition metal ion dissolution, thus stabilizing the electrode-electrolyte interface. Scanning electron microscopy and X-ray photoelectron spectroscopy results also demonstrate that there are less unwanted lithium compounds on the additive-contained cathode.