A novel Li-ion capacitor based on an activated carbon cathode and a well-dispersed ultrafine TiO2 nanoparticles embedded in mesoporous carbon nanofibers (TiO2@PCNFs) anode was reported. A series of TiO2@PCNFs anode materials were prepared via a scalable electrospinning method followed by carbonization and a postetching method. The size of TiO2 nanoparticles and the mesoporous structure of the TiO2@PCNFs were tuned by varying amounts of tetraethyl orthosilicate (TEOS) to increase the energy density and power density of the LIC significantly. Such a subtle designed LIC displayed a high energy density of 67.4 Wh kg-1 at a power density of 75 W kg-1. Meanwhile, even when the power density was increased to 5 kW kg-1, the energy density can still maintain 27.5 Wh kg-1. Moreover, the LIC displayed a high capacitance retention of 80.5% after 10000 cycles at 10 A g-1. The outstanding electrochemical performance can be contributed to the synergistic effect of the well-dispersed ultrafine TiO2 nanoparticles, the abundant mesoporous structure, and the conductive carbon networks.
Keywords: Li-ion capacitor; TiO2 nanoparticles; carbon nanofibers; electrospinning; mesoporous structure.