Abstract
Porous carbon-based nanomaterials and composites are attractive electrode active materials for energy storage devices such as lithium ion batteries (LIBs) and high power density electrochemical double layer capacitors (EDLCs). However, the electrochemical performance of porous carbon materials is highly dependent on the electrolyte/accessible surface area and the power capability capacity is limited by the electrode kinetic constrains such as inner-pore ion transport. The hierarchically ordered porous carbon (HOPC) materials exhibit uniformly distributed mesopores inside the spheres and the existence of macropores between the spheres, which could serve as a buffer for volume change and provide available channels for electrolyte. In this presentation, the fabrication and characterization of metal- and metal oxide-based HOPC composites for high-rate LIB and EDLC applications will be introduced. The HOPC-based nanocomposites were fabricated by using dual templates and evaporation induced self-assembly process. The hierarchical structures generate the highly ordered porous carbons with high specific surface area of higher than 1000 m2 g-1. The specific capacitance of HOPC electrodes can be up to 300 F g-1, and retain over 70% capacitance at a high scan rate of 1000 mV s-1. Addition of MnO2 and CoO significantly enhances electrochemical performance. In addition, the embedment of Sn nanoparticles or TiO2 also improves the stability of HOPC and retains high capacity because of the interaction of mesopores and macropores to serves as an effective buffer to prevent the volume expansion during the insertion and removal of Li ions. An extremely high coulomb efficiency of 99% with the stable specific capacity at around 300-600 mAh g-1 after 80 cycles was obtained, clearly showing the excellent of HOPC composites for next generation of energy storage devices.