Self-Organised TiO2 Nanotubes for 2D or 3D Li-Ion Microbatteries

This paper presents a Review on the development of thin-film (all-solid-state) Li-ion microbatteries. The need to move from 2D to 3D configurations, the ever-increasing necessity to adopt Li-ion or rocking-chair technology in microbatteries, and the development of new processing techniques and materials are discussed. Materials based on TiO2 are very promising as negative electrodes for Li-ion microbatteries. Strong emphasis is placed on the possibility of utilising TiO2, especially self-supported nanotubular TiO2, as an anode material for commercial 2D or 3D Li-ion microbatteries. The use of TiO2 is ecologically and economically competitive and provides cells with low self-discharge while eliminating the risk of overcharging due to its relatively high operating voltage. The high operating voltage of TiO2 also presents the advantage of negligible electrolyte decomposition. Each polymorphic form of TiO2 (anatase, rutile, TiO2(B), or brookite) has an attractive lithium storage behaviour, especially, when nanostructured. Owing to their remarkable nanoarchitecture, TiO2 nanotubes grown by potentiostatic anodization, and their derivatives (cation-or anion-doped and hierarchical composites with nanostructured metals or metal oxides), deserve attention for the fabrication of 2D or 3D Li-ion microbatteries.