Titanium niobium oxides (TiNb2O7): Design, fabrication and application in energy storage devices

With the increasing demand of electrochemical energy storage, Titanium niobium oxide (TiNb2O7), as an intercalation-type anode, is considered to be one of the most prominent materials due to high voltage (~1.6 V vs. Li+/Li), large capacity with rich redox couples (Ti4+/Ti3+, Nb4+/Nb3+, Nb5+/Nb4+) and good structure stability. In this review, we summarize the crystal structure, synthesis methods, applications of TiNb2O7 as electrodes for energy storage devices (e.g., rechargeable batteries, hybrid supercapacitors, and hydrogen storage). In addition, the effects of modification strategies (micro/nano-architectures control, doping, carbon coating/compositing) on the Li-ion storage capability of TiNb2O7 are discussed. The development trend and challenges of TiNb2O7 electrodes for energy storage are highlighted. This review can provide direction for the future research of energy storage materials, and stimulate more unique discoveries of the intercalation-type materials.