Fast-Charging and High Volumetric Capacity Anode Based on Co O /CuO@TiO Composites for Lithium-Ion Batteries.

This paper presents an investigation of anodic TiO nanotube arrays (TNAs), with a Co O /CuO coating, for lithium-ion batteries (LIBs). The coated TNAs are investigated using various analytical techniques, with the results clearly suggesting that the molar ratio of Co O /CuO in the TiO nanotubes substantially influences its battery performance. In particular, a cobalt/copper molar ratio of 2:1 on the TNAs (Co Cu @TNAs) features the best LIBs anode performance, exhibiting high reversible capacity and enhanced cycling stability. Noticeably, Co Cu @TNAs achieve excellent rate capability even after quite a high current density of 20.0 A g (≈25 C, where C corresponds to complete discharge in 1 h) and superior volumetric reversible capacity of ≈3330 mA h  cm . This value is approximately seven times higher than those of a graphite-based anode. This outstanding performance is attributed to the synergistic effects of Co Cu @TNAs: 1) the structural advantage of TNAs, with their large amount of free space to accommodate the large volume expansion during Li insertion/extraction and 2) the optimized ratio of Co O and CuO in the composite for improved capacity. In addition, no binder or conductive agent is used, which is partly responsible for the overall improved volumetric capacity and electrochemical performance.