Effect of B2O3 on the structure, morphology, and electrochemical properties of hierarchical multilayer carbon nanofiber/MnO2/carbon nanofiber composites

•Multilayer MnO2/B-containing CNF was prepared by sequential electrospinning.•B-related functional groups and MnO2 exist independently in different nanosheets.•Each component acts independently to maximize the electrochemical properties.•B-related functional groups and MnO2 optimize the pseudocapacitance.•The large number of mesopores leads to a high rate response and stable cycle life.