Aqueous lithium-ion batteries (ALiBs) present a promising avenue for safer and more sustainable energy storage solutions compared to traditional non-aqueous lithium-ion batteries. LiNiO2 (LNO) has emerged as a potential cathode material for ALiBs due to its high capacity potential and ability to facilitate Li⁺ intercalation over H⁺ intercalation in aqueous media. However, challenges remain regarding its stability and performance in aqueous electrolytes. In this study, we employ periodic density functional theory simulations to investigate the interactions between LNO surfaces and aqueous electrolytes, evaluating its viability as a cathode material for ALiBs. We have systematically and exhaustively studied the surface energetics, shedding light on the formation of NiOOHx species, one of the common issues associated with this material. We have evaluated the oxygen evolution reaction on LNO surfaces, revealing that they decompose water molecules into hydroxide and other intermediate species, thereby degrading the electrolyte. Our findings suggest that, despite their promising abilities for Li+ ion intercalation, the tendency to boost the generation of NiOOHx and its facility to decompose water at potentials lower than 1.23 V are important limitations for the battery performance

S.P.-P. appreciates the economic support of Marie Curie fellowship (H2020-MSCA-IF- 2020–101020330). A.P. is a Serra Húnter Fellow and received the ICREA Academia Prize 2019. M.S. and A.P. thank the Spanish MINECO for projects PID2020-13711GB-I00, PID2023-147424NB-I00, and PID2021-127423NB-I00, and the Generalitat de Catalunya for project 2021SGR623. Computational time at the MARENOSTRUM supercomputer has been provided by the Barcelona Supercomputing Centre through a grant from Red Española de Supercomputación, project (QHS-2022-3-0002)