Effects of an in-situ water-repelling interphase formation for LiNiO₂via anions in aqueous electrolytes

This work investigates the influence of an in-situ formed water-repellent interphase on the electrochemical performance of LiNiO₂(LNO) electrodes, which are typically known to exhibit significantly poor compatibility with aqueous-based solutions, employed in aqueous lithium-ion batteries (ALIBs). The study primarily focuses on how the adsorption energies of water molecules and various anions onto the LNO surface impact interfacial stability across different aqueous electrolytes. These interfacial interactions are closely tied to the electrochemical behavior of the LNO material. A combination of electrochemical characterization techniques, including operando measurements, and first-principles density functional theory (DFT) simulations are employed to elucidate the mechanism of anion-induced in-situ interphase formation and its subsequent effect on electrochemical performance. The findings indicate that the SO₄²⁻anion, possessing both strong adsorption affinity to the LNO surface and kosmotropic characteristics, facilitates the generation of a water-repelling interphase layer. This layer effectively reduces direct contact between LNO and water molecules, thereby mitigating side reactions associated with water-induced degradation. Consequently, this leads to enhanced electrochemical properties, such as improved cycling stability and higher Coulombic efficiency.