Easily Decomposed Discharge Products Induced by Cathode Construction for Highly Energy-Efficient Lithium-Oxygen Batteries.

The lithium-oxygen (Li-O2) battery is deemed as a promising candidate for the next-generation of energy storage system due to its ultrahigh theoretical energy density. However, low energy efficiency and inferior cycle stability induced by the sluggish kinetics of charge transfer in discharge products limit its further development in practical application. In this work, tin dioxide (SnO2) nanoparticles decorated carbon nanotubes (SnO2/CNTs) have been constructed as composite cathodes to manipulate the morphology and component of discharge products in Li-O2 batteries. Owing to the strong oxygen adsorption of SnO2, oxygen-reduction reactions tend to occur on composite cathode surfaces, resulting in the formation of flake-like discharge products of Li2- xO2 less than 10 nm in thickness rather than toroidal particles of several hundred nanometers. Such homogeneous nanosized discharge products with lithium vacancies markedly enhance the electrode kinetics and charge transfer in discharge products. Consequently, the Li-O2 batteries based on the SnO2/CNT cathodes show a small polarization voltage gap, which leads to superior energy efficiency (80%) compared with that based on pristine CNT cathodes. The results demonstrate that optimizing the discharge products with nanosized morphology and defective component by cathode construction is an effective strategy to realize the Li-O2 batteries with increased energy efficiency and improved cycle stability.