Hollow lithium manganese oxide nanotubes using MnO2-carbon nanofiber composites as cathode materials for hybrid capacitors

To improve the electrochemical performance of hybrid capacitors, hollow lithium manganese oxide (LiMn2O4, LMO) nanotubes (NTs) as cathode materials were synthesized by a solid-state reaction, using MnO2 coated on a porous carbon nanofiber (PCNF) templates. To determine the optimum shell thickness of hollow LMO, the time of MnO2 coating on PCNF was adjusted to 10, 30, and 60 min. Among these, hollow LMO NTs, which were synthesized by 30-min coating with MnO2 on the PCNFs, have superior performance. They exhibited an excellent reversible capacity (∼72.8 mAh g−1) at 1 C, capacity retention of ∼98.4% after 100 cycles, and an excellent high-rate capability. This superior performance can be explained by the hollow structure giving a reduced diffusion distance for Li-ions, the networked structure of one-dimensional NTs allowing fast charge transfer, and the achievement of the optimal stoichiometric ratio of the LMO phase.