Nitrogen-containing carbon membrane-encapsulated MnO nanorods for ultrastable lithium-ion batteries

Among the transition metal oxides that have been studied for lithium-ion battery anodes, MnO is very attractive because it has good theoretical capacity, abundant raw materials, and low toxicity. Nevertheless, its practical performance is often limited by low electronic conductivity, the tendency of MnO particles to agglomerate, and substantial volume fluctuations during repeated lithiation/delithiation processes. These factors reduce reaction efficiency and gradually deteriorate cycling stability. To address the above problems, we put forward a simple two-step path: hydrothermal crystallisation and then polydopamine-assisted pyrolysis; it can be observed that MnO nanorods are formed, and these are then conformally covered with a nitrogen-rich carbon shell (N-C@MnO). A carbon shell can be used to provide mechanical flexibility and absorb the cyclic volume variation of the electrode, and at the same time, it has good electron conductivity. These synergistic structural features collectively contribute to the outstanding cycling stability and charge-storage properties delivered by the N-C@MnO electrode. The optimised N-C@MnO electrode delivers an initial discharge capacity of 1004.7 mA h g^-1 and a high reversible capacity of 912.9 mA h g^-1 subsequent to 100 cycles at 0.1 A g^-1; and after 1400 cycles at a high rate of 5 A g^-1, it is still 293.8 mA h g^-1, demonstrating excellent structural durability under demanding operating conditions. The above results have provided a general basis for the structure of engineering high-energy-density conversion-type anodes, and this strategy offers a practical solution to improve the performance of next-generation lithium-ion batteries.