Interfacial Electron Redistribution of Hydrangea-like NiO@Ni 2 P Heterogeneous Microspheres with Dual-Phase Synergy for High-Performance Lithium-Oxygen Battery.

Lithium-oxygen batteries (LOBs) with ultra-high theoretical energy density (≈3500 Wh kg -1 ) are considered as the most promising energy storage systems. However, the sluggish kinetics during the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) can induce large voltage hysteresis, inferior roundtrip efficiency and unsatisfactory cyclic stability. Herein, hydrangea-like NiO@Ni 2 P heterogeneous microspheres are elaborately designed as high-efficiency oxygen electrodes for LOBs. Benefitting from the interfacial electron redistribution on NiO@Ni 2 P heterostructure, the electronic structure can be modulated to ameliorate the chemisorption of the intermediates, which is confirmed by density functional theory (DFT) calculations and experimental characterizations. In addition, the interpenetration of the PO bond at the NiO@Ni 2 P heterointerface leads to the internal doping effect, thereby boosting electron transfer to further improve ORR and OER activities. As a result, the NiO@Ni 2 P electrode shows a low overpotential of only 0.69 V, high specific capacity of 18254.1 mA h g -1 and superior long-term cycling stability of over 1400 h. The exploration of novel bifunctional electrocatalyst in this work provides a new solution for the practical application of LOBs.