π-type orbital hybridization and reactive oxygen quenching induced by Se-doping for Li-rich Mn-based oxide cathode

Abstract

Li-rich Mn-based oxide cathodes for next generation high-energy-density batteries are unprecedentedly enticing; however, its implementation has been largely plagued by capacity fading and potential decline, mainly associated with the irreversible lattice oxygen redox and structure rearrangements. Hereby, electrochemically stable Li-rich Mn-based oxide cathode is successfully designed by manipulating molecular polarity within host structure through the introduction of Se. Notably, the restructured electronic distribution around lattice oxygen is aroused from weak electronegativity of Se in the bulk. It is beneficial for enhancing the π -type orbital hybridization between O 2p and Mn 3d(t 2g ) due to the lowered energy level of O 2p states, resulting in the mitigation of lattice oxygen loss, which is strongly validated by ex-situ soft/hard X-ray absorption spectroscopy coupled with density functional theory calculations. Concomitantly, reactive oxygen species is deactivated with anti-aging effects in the primary/second particle sub-surface, considerably suppressing the S N 2 attack related to electrolyte decomposition and subsequent transition metals dissolution to render a well-knit cathode electrolyte interface, intensively verified by time-off light secondary-ion mass spectrometry. Greatly, the as-designed Se-LRM delivers excellent long cycling stability after 400 loops with only a 0.029% capacity fading and 1.37 mV potential decline per cycle. Given this, this elaborate work might inaugurate a potential avenue for rationally tuning the structure/interface evolution towards advanced electrodes in lithium-ion batteries.