Inverse‐direction Growth of TiO2 Microcones by Subsequent Anodization in HClO4 for Increased Performance of Lithium‐Ion Batteries

Abstract The effect of second anodization on anodically fabricated TiO 2 microcones is investigated with the aim of enhancing the lithium‐ion battery performances; these microcones are treated with a trace concentration of an electrolyte of HClO 4 . Unlike in the case of second anodization in H 2 SO 4 or H 3 PO 4 , which leads to breakdown of the structures of the microcones, the HClO 4 ‐treated TiO 2 microcones maintain their unique morphological crystalline structures; this enables the inverse growth of an oxide layer. Particularly, protruding nanoparticles provide a large surface area and thus a higher areal capacity, wherein lithium ions can be stored; these particles are formed on the back‐hemisphere layers of the microcones with an increase in the overall thickness of the barrier oxide layer. The HClO 4 ‐treated TiO 2 microcones exhibit an areal capacity of approximately 1.6 times than that of pristine TiO 2 microcones as well as an excellent cycling stability and capacity retention.