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 Li+-storage 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).