Stabilizing the surface of Li2NiO2 cathode additive by coating amorphous niobium oxy-carbide for lithium-ion batteries

The formation of solid electrolyte interphase at the first cycle has raised technical issues of capacity loss in anode materials for lithium-ion batteries. As one solution, using Li-excess Li2NiO2 as a cathode additive aims to compensate for the initial Li+ consumption by anode materials using some of the high irreversible capacity. However, Li2NiO2 is insufficient for satisfying atmospheric stability, which induces spontaneous side reactions (e.g. Li2CO3 and LiOH), resulting in an increase of interfacial resistance for Li+ migration. In addition, the small but significant evolution of oxygen (O2) gas during the charge process over 3.8 V vs. Li/Li+ brings an extra caution for safety concerns. There is no doubt that structural stabilization of Li2NiO2 is a prerequisite for practical use in lithium-ion batteries. In this study, we propose a surface coating of amorphous niobium oxycarbide (NbOxCy) onto Li2NiO2 particles to improve their atmospheric stability, together with suppression of O2 gas evolution. Owing to its distinctive physicochemical properties, NbOxCy is beneficial for enhancing vulnerability to moisture as well as scavenging any residual O2 gas. In practice, the adoption of NbOxCy-coated Li2NiO2 improved electrochemical performance in full cells and was verified as a strategic solution to two fundamental challenges.