Heterostructure engineering of MnO/TiO2 embedded in N-doped hollow carbon nanofibers for superior sodium storage

TiO2-based materials are viewed as promising anodes for sodium-ion batteries due to their high theoretical capacity and superior structural stability, but they suffer from low electron conductivity and sluggish Na+ diffusion kinetics, which leads to inferior rate performance and cyclability. Herein, a novel MnO/TiO2 embedded into N-doped hollow carbon nanofibers (MnO/TiO2@N-C) is proposed to address this challenge via combining the heterostructure engineering and nanostructure designing. The integrated design greatly enhances the Na+ transfer and adsorption, provides more active interfacial sites and promotes the electric conductivity. The first -principle density functional theory calculations manifest that the constructed hetero-interfaces between MnO and TiO2 induce strong electric fields and accelerate Na+ transfer. Due to these merits, the MnO/TiO2@N-C exhibits a high reversible discharge capacity of 406.5 mA h g-1 at 0.3 A/g, superior rate capability (213.3 mA h g-1 at 3 A/g), and exceptional cycling performance (99.3 % capacity retention after 10,000 cycles at 3 A/g). In addition, the Na full cell based on MnO/TiO2@N-C anode exhibits a promising energy density of 332.8 Wh kg- 1 at 677.1 W Kg-1. This work offers a novel and an interesting strategy to improve electrochemical sodium storage of TiO2-based materials, which is significant for the practical applications of sodium-ion batteries.