Improved Cycling Stability of LiCoO at 4.5 V via Surface Modification of Electrodes with Conductive Amorphous LLTO Thin Film.

The stability issue of LiCoO cycled at high voltages is one of the burning questions for the development of lithium ion batteries with high energy density and long cycling life. Although it is effective to improve the cycling performance of LiCoO via coating individual LiCoO particles with another metal oxides or fluorides, the rate capacity is generally compromised because the typical coating materials are poor conductors. Herein, amorphous LiLaTiO, one of the most successful solid electrolytes, was directly deposited on the surface of made-up LiCoO electrodes through magnetron sputtering. Not only the inherent conductive network in the made-up LiCoO electrodes was retained, but also the Li transport in bulk and across the cathode-electrolyte interface was enhanced. In addition, the surface chemical analysis of the cycled LiCoO electrodes suggests that most of the stability issues can be addressed via the deposition of amorphous LiLaTiO. With an optimized deposition time, the LiCoO electrodes modified by LiLaTiO performed a steady reversible capacity of 150 mAh/g at 0.2 C with the cutoff voltage from 2.75 to 4.5 V vs. Li/Li and an 84.6% capacity gain at 5 C comparing with the pristine one.