Modulating electronic structure of honeycomb-like Ni2P/Ni12P5 heterostructure with phosphorus vacancies for highly efficient lithium-oxygen batteries

Abstract

Lithium-oxygen batteries (LOBs) have been attracting incremental attention beyond conventional Li-ion batteries owing to their superior theoretical energy density (~3500 Wh kg−1). Developing gas diffusion electrodes with high catalytic activity for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is considered as one of the most promising strategies to promote the practical application of this novel system. Herein, a honeycomb-like Ni2P/Ni12P5 heterostructure with abundant phosphorus vacancies in situ growing on Ni foam (Ni2P/Ni12P5@NF) is developed as an effective and stable electrode for LOBs. Phosphorus vacancies are capable of inducing delocalization of constrained electrons near the Ni-P bonds, thereby regulating the band gap to enhance both the conductivity and the catalytic activity for oxygen electrode reactions. In addition, the modulation of electronic structure along the heterogeneous interface between Ni12P5 and Ni2P optimizes the adsorption of oxygenated intermediates, which is beneficial to accelerate the interface reaction kinetics of oxygen electrode reactions. Impressively, the LOBs with Ni2P/Ni12P5@NF containing abundant phosphorus vacancies exhibit low overpotential of 0.89 V, ultra-high discharge specific capacity of 13254.1 mA h g−1, and remarkable durability of over 500 h. This work concerning engineering heterostructure with rich vacancies can provide new guidance for the development of high performance electrocatalysts.