Stabilizing 4.6 V LiCoO2 by Lithium Compensative Additives

The 4.6 V-class LiCoO₂/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 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/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.