Stabilizing 4.6 V LiCoO2 by Lithium Compensative Additives

The 4.6 V-class LiCoO 2 /SiO x full cell exhibits an ultrahigh energy density. However, a large amount of Li + ions are consumed by the SiO x anode in the initial cycle, bringing in the lithium deficiency issue to the battery system and aggravating the structural degradation of LiCoO 2 (LCO) at high voltages. In this study, we demonstrate that via adding a sacrificial lithium compensative additive (LCA) Li 2 NiO 2 (LNO), the capacity and cycling performance of the 4.6 V LiCoO 2 /SiO x full cell can be effectively improved. Comprehensive investigations on its working mechanisms reveal that LNO can irreversibly release Li + ions in the initial cycles, which alter the delithiation equilibrium of LCO to mitigate the formation of lithium-deficient layers, as evidenced by in situ X-ray diffraction (XRD), in situ Raman spectroscopy, and transmission electron microscopy (TEM) results. These results prove that utilizing LCA is a promising strategy to stabilize LCO at high voltages in lithium-deficient systems, which is enlightening to other cathodes.