Hierarchical porous ZnMnO yolk-shell microspheres with superior lithium storage properties enabled by a unique one-step conversion mechanism.

ZnMnO has attracted enormous attention as a novel anode material for rechargeable lithium-ion batteries due to its high theoretical capacity. However, it suffers from capacity fading because of the large volumetric change during cycling. Here, porous ZnMnO yolk-shell microspheres are developed through a facile and scalable synthesis approach. This ZnMnO can effectively accommodate the large volume change upon cycling, leading to an excellent cycling stability. When applying this ZnMnO as the anode in lithium-ion batteries, it shows a remarkable reversible capacity (400 mA h g at a current density of 400 mA g and 200 mA h g at 6400 mA g) and excellent cycling performance (540 mA h g after 300 cycles at 400 mA g) due to its unique structure. Furthermore, a novel conversion reaction mechanism of the ZnMnO is revealed: ZnMnO is first converted into intermediate phases of ZnO and MnO, after which MnO is further reduced to metallic Mn while ZnO remains stable, avoiding the serious pulverization of the electrode brought about by lithiation of ZnO.