Embedding CoO nanoparticles in three-dimensionally ordered macro-/mesoporous TiO for Li-ion hybrid capacitor.

Lithium-ion hybrid capacitors (LICs) have gained increasing focus owing to their high energy/power densities. The development of anodes with superior rate capability is an effective way to surmount the kinetic mismatch between anodes and cathodes, and thus, enhancing the energy/power densities. Herein, CoO nanoparticles embedded in three-dimensionally (3D) ordered macro-/mesoporous TiO (CoO@TiO) are synthesized through an in situ method from dual templates. Differing from the composite prepared by loading active nanoparticles on support, CoO nanoparticles are embedded in TiO framework, which can improve the stability of the electrode. Furthermore, the hierarchically porous structure of TiO is in favor of the rapid diffusion of ions and electrolyte. As a result, The CoO@TiO-2 composite with an optimized CoO content (~25 wt%) delivers a high capacity of 944.1 mAh g after 100 cycles at 0.1 A g and high-rate capability (405.7 mAh g after 1000 cycles at 5 A g). The LIC assembled with CoO@TiO-2 anode and activated carbon (AC) cathode delivers high energy/power densities (maximum, 87.9 Wh kg/10208.9 W kg) and great cycle stability (88.1%, 6000 cycles, 0.5 A g).