Rutile TiO₂ Creates Advanced Na-Storage Materials

High Resolution Image Download MS PowerPoint Slide Rutile-type titanium oxide (TiO 2 ) is a resource-rich and inexpensive material with a one-dimensional ion-diffusion path along the c -axis. However, it has received no attention as an anode material for Na-ion batteries because of its low electronic conductivity and limited ion diffusion in the ab -plane direction. We have revealed for the first time the reversible Na insertion–extraction reaction of rutile TiO 2 and have recently reported the improvement in the anode performances by doping with various impurity elements such as Nb 5+, Ta 5+, and In 3+ . In this Review, we introduce a material chemistry methodology to enhance the anode properties of the rutile TiO 2 electrode by impurity doping, introduction of oxygen vacancies, formation of single-crystalline particles, and reduction of their aspect ratio. The knowledge is remarkably effective for creating advanced high-performance anode materials with not only using rutile TiO 2 but also using anatase TiO 2 and other titanium-based oxides.