MnCo2O4 decorated Magnéli phase titanium oxide as a carbon-free cathode for Li–O2 batteries

Abstract

Advanced cathode catalysts are crucial to the promotion of aprotic Li–O₂ batteries for practical applications. Carbon is usually used as a cathode catalyst, but it reacts with the discharge products (Li₂O₂, LiO₂) to form an insulating layer of lithium carbonate and prevents further reaction. To resolve this issue, the development of non-carbon cathode catalysts is of great demand. Herein, for the first time, we designed and fabricated a MnCo₂O₄ (MCO) spinel oxide decorated Magnéli phase Ti₄O₇ as a carbon-free cathode for Li–O₂ batteries. The sub-stoichiometric Ti₄O₇ oxide serves as an electronic conductive network. The MCO spinel oxide along with the synergistic effect between Ti₄O₇ and MCO facilitate the kinetics of both oxygen reduction and decomposition of Li₂O₂. Furthermore, uniform anchoring of MCO nanoparticles on Ti₄O₇ surface provides a stable lithium peroxide–cathode interface during the discharge/charge process. The resulting Ti₄O₇/MCO hybrid proves to be a highly effective cathode catalyst. The discharge/charge voltage gap of the Ti₄O₇/MCO hybrid is about 0.75 V, which is significantly lower than that of pure carbon, C + MCO and pristine Ti₄O₇ cathode. A high specific capacity (5400 mA h g⁻¹ at 100 mA g⁻¹) and excellent cycling performance (100 cycles at a capacity of 500 mA h g⁻¹ under 200 mA g⁻¹) were obtained for this hybrid. The high catalytic activity and durability renders the Ti₄O₇/MCO hybrid a highly promising carbon-free cathode for Li–O₂ batteries.