Driving the Interfacial Ion-Transfer Kinetics by Mesoporous TiO2 Spheres for High-Performance Aqueous Zn-Ion Batteries.

The aqueous zinc-ion batteries (ZIBs) have been considered as a promising energy storage device. However, the ion transfer at the Zn metal anode-electrolyte interface is limited by the sluggish kinetics resulting in high interface resistance. Herein, mesoporous TiO2 (m-TiO2) is coated on the Zn foil (Zn-TiO2) driving the ion's faster transfer to reduce interface resistance (70.1 Ω vs 799.3 Ω of bare Zn). The lower interface resistance is ascribed to shortening the ion transfer path provided by the mesoporous structure and the smaller Zn2+ absorption energy barrier of the surface of the Zn-TiO2 anode as well as the unobstructed ion transfer path at the crystal planes (100) of TiO2, which have been supported by the density functional theory (DFT) calculation and experiments. Therefore, the Zn-TiO2 anodes in the symmetrical cells display a low voltage hysteresis (36.5 mV) and long-term cycling stability (500 h at 4.4 mA cm-2). Especially, the Zn-TiO2/MnO2 full cells show superior cycling performance with a high capacity of 269.8 mAh g-1 after 50 cycles at 0.2 A g-1 and 210.9 mAh g-1 after 1000 cycles at 0.5 A g-1. The analysis of ion-transfer kinetics at the interface provides deep enlightenment and reference for the study of the metal anodes.