Stabilizing 4.6 V LiCoO2 by Lithium Compensative Additives

The 4.6 V-class LiCoO2/SiOx full cell exhibits an ultrahigh energy density. However, a large amount of Li+ ions are consumed by the SiOx anode in the initial cycle, bringing in the lithium deficiency issue to the battery system and aggravating the structural degradation of LiCoO2 (LCO) at high voltages. In this study, we demonstrate that via adding a sacrificial lithium compensative additive (LCA) Li2NiO2 (LNO), the capacity and cycling performance of the 4.6 V LiCoO2/SiOx 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.