Encapsulating V2O3 Nanoparticles in Carbon Nanofibers with Internal Void Spaces for a Self-Supported Anode Material in Superior Lithium-Ion Capacitors

A lithium-ion capacitor (LIC) consisting of a lithium-ion battery (LIB)-type anode and a supercapacitor (SC)-type cathode gains wide attention on account of the integration with the merits of high-energy LIB and high-power SC. However, LIC usually shows low energy/power density at high charge/discharge rate due to the sluggish charge/discharge kinetics of the LIB-type anode. Herein, to address this issue, we develop a self-supported anode material for LIC (V2O3@CNFs) with good charge transfer kinetics by encapsulating V2O3 nanoparticles in carbon nanofibers with internal void spaces. The V2O3 nanoparticles not only provide abundant Litstorage sites but also shorten routes for Li+ diffusion and electron transport, which both improve the charge transfer kinetics. Besides, the 3D conductive carbon nanofiber network serves as a mechanical support for V2O3 nanoparticles and provides the reserved internal void spaces to buffer the volumetric expansion and subsequent aggregation during the charge-discharge process of V2O3. Consequently, the optimal V2O3@CNF anode delivers a high capacity (569.1 mA h g(-1) at 0.1 A g(-1)), surprising rate capability (238.5 mA h g(-1) at 10.0 A g(-1)) and long-term cyclic steadiness (91.0% retention after 1000 cycles at 1.0 A g(-1)) in half-cell tests. Furthermore, the LICs assembled with activated carbon cathode and V2O3@CNF anode exhibit a high energy density (97.6 W h kg(-1)), a high power density (12.1 kW kg(-1) with 20.2 W h kg(-1) retained), and impressive cyclic steadiness (73% retention after 5000 cycles at 1.0 A g(-1)) in a broad working voltage (0.005-4.0 V).