Nitrogen-Doped Carbon-Coated TiO₂/TiF₃ Heterostructure Nanoboxes with Enhanced Lithium and Sodium Storage Performance

TiO2 is the most promising anode material for lithium-/sodium-ion batteries (LIBs/SIBs) for grid-scale energy storage. However, the use of TiO2 anodes is greatly restricted by the low theoretical capacity, inferior electrical conductivity, and slow ion diffusion. In this study, nitrogen-doped carbon-coated TiO2/TiF3 heterostructure nanoboxes with a hierarchically porous yolk–shell structure were successfully fabricated and demonstrated impressive electrochemical performance when employed as anodes for LIBs and SIBs. Specifically, this anode delivers a high lithium storage capacity of 245 mA h g–1 at 100 mA g–1 after 100 cycles and excellent rate capability up to 5000 mA g–1 with a capacity of 71 mA h g–1. In addition, it also delivers a considerable sodium storage capacity of 112 mA h g–1 at 50 mA g–1 after 100 cycles. The enhanced lithium and sodium storage performance is attributed to the TiO2/TiF3 heterostructure that improves both specific capacity and charge transfer, conductive carbon frameworks, and hierarchically porous yolk–shell structure with open diffusion channels.