Bifunctional Al₂O₃-Based Artificial Layers on LiNiO₂ Cathodes for High-Energy-Density Aqueous Li-Ion Batteries

Passivation films, commonly referred to as solid-electrolyte interphase and cathode-electrolyte interphase (CEI), are essential for the operation of rechargeable batteries due to their positive impact on electrochemical performances. This paper reports a bifunctional Al₂O₃ artificial layer on a LiNiO₂ (LNO) cathode for high-energy-density aqueous Li-ion batteries (ALIBs). As determined by first-principles density functional theory calculations, Al₂O₃ has a relatively high adsorption energy with H₂O molecules at the surface, which is expected to effectively block their direct contact with the LNO surface. The electrochemical characteristics of LNO cathodes can be improved by coating an Al₂O₃ layer, especially cyclability (capacity retention of ∼77.8% after 50 cycles), forming an effective CEI layer and providing stability to the LNO bulk structure. Particularly, the Al₂O₃ layer undergoes an in situ modification to the more stable Al(OH)₃ in the aqueous electrolyte, which has an important role in producing a more effective CEI layer and suppressing the interfacial side reactions. This paper presents a promising approach for LNO-based cathodes for high-energy-density ALIBs, with a crucial methodology to enhance their electrochemical properties, even in conventional aqueous solutions.