Facile preparation of unique three-dimensional (3D) α-MnO₂/MWCNTs macroporous hybrid as the high-performance cathode of rechargeable Li-O₂ batteries

Undoubtedly, there remains an urgent prerequisite to achieve significant advances in both the specific capacity and cyclability of Li-O₂ batteries for their practical application. In this work, a series of unique three-dimensional (3D) α-MnO₂/MWCNTs hybrids are successfully prepared using a facile lyophilization method and investigated as the cathode of Li-O₂ batteries. Thereinto, cross-linked α-MnO₂/MWCNTs nanocomposites are first synthesized via a modified chemical route. Results demonstrate that MnO₂ nanorods in the nanocomposites have a length of 100–400 nm and a diameter ranging from 5 to 10 nm, and more attractively, the as-lyophilized 3D MnO₂/MWCNTs hybrids is uniquely constructed with large amounts of interconnected macroporous channels. The Li-O₂ battery with the 3D macroporous hybrid cathode that has a mass percentage of 50% of α-MnO₂ delivers a high discharge specific capacity of 8, 643 mAh·g⁻¹ at 100 mA·g⁻¹, and maintains over 90 cycles before the discharge voltage drops to 2.0 V under a controlled specific capacity of 1, 000 mAh·g⁻¹. It is observed that when being recharged, the product of toroidal Li₂O₂ particles disappears and electrode surfaces are well recovered, thus confirming a good reversibility. The excellent performance of Li-O₂ battery with the 3D α-MnO₂/MWCNTs macroporous hybrid cathode is ascribed to a synergistic combination between the unique macroporous architecture and highly efficient bi-functional α-MnO₂/MWCNTs electrocatalyst.