Micro/nanostructured TiNb2O7-related electrode materials for high-performance electrochemical energy storage: recent advances and future prospects

Abstract

The increasing demand for large-scale electrochemical energy storage, such as lithium ion batteries (LIBs) for electric vehicles and smart grids, requires the development of advanced electrode materials. Ti–Nb–O compounds as some of the most promising intercalation-type anode materials have attracted a lot of attention owing to their high theoretical capacity (388–399 mA h g⁻¹) arising from the multiple redox pairs (Ti⁴⁺/Ti³⁺, Nb⁵⁺/Nb⁴⁺, and Nb⁴⁺/Nb³⁺), high safety, and superior cycling stability. However, their intrinsic low electronic conductivity and slow solid-state ion diffusion lead to unsatisfactory rate performance. To overcome these drawbacks, various efficient strategies have been proposed to improve the performance of Ti–Nb–O compounds, especially TiNb₂O₇. This Review aims to provide rational understanding of how structural engineering approaches (e.g., dimensional/morphological control, doping/hybridizing with exotic elements/components, carbon coating/compositing, etc.) improve the electrochemical properties of micro/nanostructured TiNb₂O₇-based anode materials. In addition, other Ti–Nb–O compounds with different compositions as anodes for LIBs and micro/nanostructured TiNb₂O₇-based anodes for other energy storage systems (sodium-ion batteries, hybrid supercapacitors, and vanadium redox flow batteries) are discussed. Finally, the challenges and opportunities for micro/nanostructured TiNb₂O₇-related electrode materials for high-performance energy storage applications are highlighted.