Bucket effect on high-performance Li–O2 batteries based on P-doped 3D NiO microspheres with conformal growth of discharge products

Abstract

Rechargeable Li–O₂ batteries are a remarkable technology for electrical energy conversion and storage owing to their exceptionally high theoretical energy density versus that of commercial Li-ion batteries. However, this promising system still suffers from limited practical energy density, poor cycling stability, severe side reactions, high overpotentials, etc. In this work, NiO materials with different P doping contents were synthesized by hydrothermal and subsequent annealing methods, which served as cathode catalysts for Li–O₂ batteries. The introduction of P heteroatoms effectively rationalized the charge distribution on the P–NiO surfaces, enabling remarkable advancement of the reaction kinetics. This is because a large number of Ni–P coordination groups were produced as emerging catalytic sites, thus greatly reducing the Gibbs energy barriers during cycling. P–NiO also realizes superior electrochemical performance of Li–O₂ batteries by modulating the affinity for intermediates and regulating the formation/decomposition of conformal thin-film Li₂O₂ in discharge and charge processes. As expected, the P–NiO cathode delivered a remarkable electrochemical performance for Li–O₂ electrocatalysis. This research contributes to an in-depth understanding of the relationship between electronic structures on oxygen electrocatalyst surfaces and electrocatalytic activities in Li–O₂ batteries.