Electrolyte reactivity, oxygen states, and degradation mechanisms of nickel-rich cathodes

Understanding interactions at electrode interfaces is a key aspect of building better batteries. This work explores the interface between fully lithiated/delithiated Ni-rich cathodes and organic electrolytes using density functional theory and ab initio molecular dynamics. By analyzing the behavior of LiBF4 and LiPF6 salts, we gain valuable insights into atomic-level interactions at the cathode-electrolyte interface. We observe significantly higher surface activity in delithiated cathodes relative to lithiated cathodes (forming O2 species in peroxide form), transitioning from a singlet state into a triplet state while being released from the cathode. Ethylene carbonate dissociation, triggered by surface oxygen radicals, often generates CO2 and CO on the surface. Variations in Ni and O atomic charges reveal how different lithiation levels affect surface behavior, while the degree of hydrogen passivation significantly influences surface degradation. Lower passivation promotes O2 evolution, while higher levels lead to H2O formation. These findings highlight the potential of targeted surface modifications to enhance battery performance and safety. [Display omitted] •Delithiated Ni-rich cathodes exhibit higher surface reactivity than lithiated ones•Surface passivation influences initial degradation pathways significantly•Surface radical oxygen forms peroxide ions that trigger electrolyte breakdown•Understanding interface reactivity paves the way for targeted surface modifications Peiris et al. investigate the interfacial chemistry between Ni-rich cathodes and electrolytes. Their results reveal heightened reactivity in delithiated cathodes and identify key degradation pathways triggered by the state of lithiation and surface passivation, which underscores the importance of understanding interfacial interactions to guide future surface modifications.