Micro- and nanomorphology coexisting in titanium dioxide coating for application as anode material in secondary lithium-ion batteries

Titanium dioxide has recently attracted attention as an anode material for use in lithium-ion batteries, owing to its high reversible capacity and durable charge/discharge characteristics. The aim of the study is to combine micro-arc oxidation (MAO) and post-alkali treatment to realize an anatase titanium dioxide (TiO2) scaffold layer on titanium plates. Using this combination, coexisting micro- and nanomorphology can be realized in the TiO2 layer. This increases the specific surface area of the TiO2 layer and thereby improves the charge capacity and charge/discharge rate of the anode. The effectiveness of MAO to fabricate a micrometer-scale porous TiO2 structure on titanium plate, and the formation of nano-flakes by alkali treatment on porous anatase TiO2 layer was demonstrated. Further, numerous 40-80 nm alkali-treatment-induced nano-flakes grew all over the oxide surface, substantially increasing its specific surface area. The measured electrochemical properties demonstrate that at potentials of − 1.98 V and − 0.56 V vs. Ag/AgCl, lithium ions were respectively inserted into and extracted from the TiO2 layer with nano-flakes. The nano-flakes promote faster lithium-ion insertion and extraction and higher associated number of charge than the MAO TiO2. The detailed charging/discharging kinetic processes of the MAO, annealed MAO, alkali-treated MAO, and annealed and alkali-treated MAO specimens were determined using electrochemical impedance spectroscopy, thus providing further insight into the performance of the TiO2 coating.