Pseudocapacitance-Dominated MnNb2O6-C Nanofiber Anode for Li-Ion Batteries

MnNb2O6 anode has attracted much attention owing to its unique properties for holding Li ions. Unluckily, its application as a Li-ion battery anode is restricted by low capacity because of the inferior electronic conductivity and limited electron transfer. Previous studies suggest that structure and component optimization could improve its reversible capacity. This improvement is always companied by capacity increments, however, the reasons have rarely been identified. Herein, MnNb2O6-C nanofibers (NFs) with MnNb2O6 nanoparticles (similar to 15 nm) confined in carbon NFs, and the counterpart MnNb2O6 NFs consisting of larger nanoparticles (40-100 nm) are prepared by electrospinning for clarifying this phenomenon. The electrochemical evaluations indicate that the capacity achieved by the MnNb2O6 NF electrode presents an activation process and a degradation in subsequence. Meanwhile, the MnNb2O6-C NF electrode delivers high reversible capacity and ultra-stable cycling performance. Further analysis based on electrochemical behaviors and microstructure changes reveals that the partial structure rearrangement should be in charge of the capacity increment, mainly including pseudocapacitance increment. This work suggests that diminishing the dimensions of MnNb2O6 nanoparticles and further confining them in a matrix could increase the pseudocapacitance-dominated capacity, providing a novel way to improve the reversible capacity of MnNb2O6 and other intercalation reaction anodes.