Reduced Co3O4 nanowires with abundant oxygen vacancies as an efficient free-standing cathode for Li–O2 batteries

Abstract

The growth mechanism and reversible formation/decomposition of the discharge products in Li–O₂ batteries, which play a vital role in the performance of these batteries, are greatly affected by the construction of the cathode. In this work, a free-standing cathode with reduced Co₃O₄ nanowires (r-Co₃O₄@Ni) is prepared by a facile hydrothermal calcination process followed by reduction with aqueous NaBH₄. The cathode not only displays a high discharge capacity of 4448 mAh g⁻¹ but also performs stably for 162 cycles, which is nearly three times the number of cycles of an Li–O₂ battery with pristine Co₃O₄@Ni and even better than that with a RuO₂-modified electrode (RuO₂/Co₃O₄@Ni). The Li₂O₂ growth models of the three types of Co₃O₄ electrodes at different discharge stages are studied in detail to understand the catalytic processes occurring on the surface of the electrodes. As a conclusion, the superior properties of r-Co₃O₄@Ni are due to the enhanced surface growth of the discharge products, which is promoted by the abundant oxygen vacancies and conformally distributed active sites generated during NaBH₄ treatment.