Amorphous LiAlSiO4 coating modifies the crystal structure stability and electrochemical behaviors of nanocrystalline LiCoO2 at 4.6 V

The mechanically stable and Li+-conducting solid solution of lithium aluminosilicate (LiAlSiO4 or Li2O·Al2O3·2SiO2, LASO) has been regarded as one of effective coating materials to suppress the adverse transformation of well-crystallized LiCoO2 (LCO) into Li-insulating Co3O4, but its functional mechanism is still ambiguous so far. In this study, as-prepared LCO nanocrystallites are previously dispersed in the formation system of amorphous LASO, and the resulting LCO@LASO is applied as Li+-ion battery cathodes to elaborate a reinforcing mechanism of the amorphous coating for the Li+-ion insertion/extraction behaviors of 4.6 V LiCoO2. Aside from a synergistic effect of the three components (i.e., Li2O, Al2O3 and SiO2) in coating layer, the much higher high-rate capability (i.e., 149.1 mAh g-1, 2.0 C) and long-term cycling stability (160.1 mAh g-1, 0.5 C, the 360th cycle) of LCO@LASO than those (50.5 mAh g-1, 2.0 C; 142.4 mAh g-1, 0.1 C, the 100th cycle) of the uncoated counterpart suggests a potential application of the amorphous LASO in achieving the high-voltage electrochemical properties of nanocrystalline LiCoO2 in future.