Nano-Hierarchical Hollow Manganese Oxide Anode Material with High Performance for Lithium-Ion Battery

Lithium-ion batteries (LIBs) are expected to continue playing important roles in energy storage for mobile communication and electric vehicle (EV) and renewable energy applications in the foreseeable future. Graphite as a commercial anode material for LIB possesses the advantages of high coulombic efficiency and good cycle stability.  However, its theoretical capacity is only 372mAh/g, and this limits the total capacity of the full battery. The demand for higher energy capacity of the energy storage cell has been driving the development of alternative anode materials with higher capacities. Certain nanocrystalline metal oxides have been shown to be able to work as a reversible anode through heterogeneous conversion reaction.

The high theoretical capacity and density give metal oxides the edge over graphite as high energy density anodes for LIB. Nevertheless, due to the high kinetic barrier of the conversion reaction at room temperature, metal oxide anodes typically exhibits large potential hysteresis between lithiation and de-lithiation cycles. The hysteresis reduces the operating voltage window as well as the energy efficiency of the LIB cell. Furthermore, the poor conductivity and large volume expansion arising from lithiation of the metal oxide particles are major shortcomings that may cause poor cycling stability. Compared with other conversion–type metal oxide anodes, manganese oxide (MnO_x) shows smaller potential hysteresis and lower operation potential. In addition, MnO_xhave the advantages of being environment friendly and abundant.

In this work, we have prepared hierarchical hollow MnO₂ by utilizing a SiO₂-templating hydrothermal process. The results revealed that the novel hollow nanostructure MnO₂ electrode had a specific charge capacity as large as 1364 mAh/g at 0.1 C-rate, and it unprecedentedly demonstrates high rate performance, retaining 878 mAh/g at 2 C-rate and good cycle stability.