Hierarchical TiO2-x nanoarchitectures on Ti foils as binder-free anodes for hybrid Li-ion capacitors.

Hybrid Li-ion capacitor (LIC) draws more attention as novel energy storage device owing to its high power density and high energy density. Designing three-dimensional electrode materials is beneficial for improving electrochemical performance of LICs. Herein, an improved hydrothermal method combined with an ion-exchange reaction is used to manufacture oxygen vacancies (OVs)-doping TiO2 (TiO2-x) nanowires/nanosheets (NWS) on Ti-foil. Then TiCl4 treatment is performed to form TiO2-x NWS/nanocrystallines (NWSC). These-obtained hierarchical nanoarchitectures assumes enrich electro-active sites and contact areas, which can improve electron transference and structural stability. The TiO2-x NWSC is used as binder-free anode for Li-ion battery and achieves high specific capacity (300 mAh g-1 at 0.1 A g-1), excellent rate capability (102 mAh g-1 at 5 A g-1) and long cycle stability (44% after 1000 cycles at 1 A g-1). LICs assembled with a TiO2-x NWSC anode and an activated carbon cathode have an energy density of 44.2 W h kg-1 at the power density of 150 W kg-1. Therefore, the TiO2-x NWSC is a potential candidate for high energy and high power electrochemical energy storage devices.