Cation-Assisted Formation of Porous TiO2–x Nanoboxes with High Grain Boundary Density as Efficient Electrocatalysts for Lithium–Oxygen Batteries

Despite the ultrahigh energy density of rechargeable lithium–oxygen (Li-O2) batteries, their practical use is still hindered by the poor performance of electrocatalysts. Recently, porous and hollow nanostructured catalysts have been found to be promising electrocatalysts toward the ORR/OER to improve the performance of Li-O2 batteries. However, the catalytic activities of the catalysts are still insufficient and the nanopores are easily clogged by the insoluble discharge products. Herein, highly porous and hollow TiO2–x nanoboxes (TiO2–x NBs) with large surface areas, increased oxygen vacancies, and high grain boundary density have been developed as an electrocatalyst for Li-O2 batteries via a cation-assisted synthetic approach. The Li-O2 batteries with TiO2–x NBs as the electrocatalyst exhibit a high specific capacity of 8569 mA h g–1, excellent rate capability, and long cycle life up to 200 cycles when the capacity is limited to 1000 mA h g–1. Moreover, this cation-assisted approach for fine-tuning the nanostructure could be an innovative strategy to design efficient electrocatalysts for high-performance Li-O2 batteries.