Surface Design Engineering of LiTaO3 Coating on Li-Excess Li2NiO2 Cathode Additive for Lithium-Ion Batteries

Abstract

The latest research has mainly focused on enhancement in the energy density of lithium-ion batteries (LIBs) to satisfy the rigorous industrial demands. As the most common approach for improving the energy density of LIBs, the utilization of high capacity anode materials, such as silicon suboxide (SiOx), has been highlighted, instead of graphite. SiOx anodes are known to have a high specific capacity and low operating voltage (< 0.5 V vs. Li/Li+). However, the severe initial capacity loss induced by the formation of solid electrolyte interphase (SEI) limits their commercial use in LIBs. To compensate for the initial loss of available Li+, the application of Li-excess cathode additives has been considered as the most practical strategy for supplying surplus Li+ during the initial charge process. In this respect, Li2NiO2 is a suitable cathode additive because it offers a high initial charge capacity (≥ 320 mAh g-1) and a compatible operating voltage with commercial cathode materials. Surface protection of Li2NiO2 is still required, however, due to its vulnerability to moisture (H2O) and carbon dioxide (CO2) in the ambient atmosphere. Moreover, Li2NiO2 becomes more structurally unstable during cycle due to oxygen (O2) gas evolution, leading to the formation of microcracks. To overcome these obstacles, we suggest a functional LiTaO3 coating layer onto the surface of Li2NiO2 for structural stabilization. In practice, the LiTaO3 coating layer can effectively suppress the production of impurities (i.e., LiOH and Li2CO3) at the surface of Li2NiO2 after air exposure. Furthermore, the gas evolution and microcracks can be minimized by enhancing the structural stability of Li2NiO2 during cycling. These synergetic effects of the LiTaO3 coating layer can provide clear insights for the development of Li-excess cathode additives for achieving advanced LIBs.