MOF-assisted three-dimensional TiO2@C core/shell nanobelt arrays as superior sodium ion battery anodes

An original electrode, 3D TiO2@C core/shell nanobelt arrays with controllable carbon coating thickness, was successfully constructed in this work. The 3D TiO2 nanobelts were directly grown on Ti foil, and then were coated with a layer of metal-organic framework (MOF). After thermal annealing, a porous carbon layer with tunable thickness was coated onto the 3D TiO2 nanobelts through changing the MOF thickness. The as-prepared TiO2@C-2 h with 5-nm-thick carbon layer presented an excellent discharge capacity of 210.5 mAh g−1 after 100 cycles at a current density of 50 mA g−1, which is 38% higher than that of pure TiO2 electrode without carbon coating. Moreover, it can maintain a reversible capacity of 141 mAh g−1 after 1000 cycles at a current density of 200 mA g−1, and a good rate performance with 33% of capacity retention when the current density increasing from 50 to 5000 mA g−1. All the results indicate that the TiO2@C core/shell nanobelt array is a promising anode for sodium-ion batteries.