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.