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

One major challenge in capacitor development is achieving high capacitance and large energy density with rapid charge and discharge rates of minutes to seconds. This paper reports boron-containing trilayer structured MnO2/ carbon nanofiber composites(PPMnB) as promising supercapacitor electrodes with high electrochemical properties under rapid charge and discharge conditions. Multilayer carbon nanofiber(CNF) composites are designed to maximize the advantages of CNF, MnO2, and boron functional groups when applying functionalized porous CNF containing transition metal composites to supercapacitor electrodes. The PPMnB electrode exhibits a high specific capacitance (215 Fg- 1 at 1 mAcm- 2), good rate capability (83 % capacity retention at 20 mAcm- 2), high energy density (23.5 Whkg- 1 at 400 Wkg- 1), and good cycling stability (only 6.0 % loss after 10,000 cycles at 1 mAcm- 2). In addition, the asymmetric capacitor of the PPMnB(25) and PPB(0) used as the positive and negative electrode shows excellent electrochemical performance, including an excellent energy density of 46.3 Whkg- 1 at a maximum voltage of 1.4 V. High electrochemical performance is achieved through the combined effects of the hierarchical porosity of CNF, high electrochemical activity of MnO2, and increased electrical conductivity by boron functional groups in each layer.