An optimized nanostructure design for high‐power, high‐energy lithium‐ion batteries and supercapacitors is realized by fabricating a nanocomposite with highly dispersed nanoparticles of active materials in a nanoporous carbon matrix. A nano‐LiFePO4/nanoporous carbon matrix nanocomposite forms a bridge between a supercapacitor and a battery electrode and offers a reasonable compromise between rate and capacity.

RuO 2 /CNT nanocomposites with well-dispersed RuO 2 nanoparticles (diameter <2 nm) on the carbon nanotubes' surface, synthesized through an easy and efficient solution-based method, have been investigated for potential application in electrochemical capacitors (ECs) as electrode materials. The electrochemical results demonstrate that the supporting material of CNT can significantly promote the supercapacitance performance of RuO 2 . The RuO 2 nanoparticles in the composite with a RuO 2 /CNT mass ratio of 6:7 could achieve a specific capacitance of as high as 953 F g -1 . The results also demonstrate that the resulted RuO 2 /CNT nanocomposites are superior electrode materials for ECs with a high specific capacitance and significantly enhanced highpower and high-energy capabilities as well as improved cycling performance compared with bare RuO 2 . At a power density of 5000 W kg -1 , the RuO 2 /CNT composite (RuO 2 /CNT ) 6:7 in wt %) can still deliver an energy density of 16.8 Wh kg -1 , which is about 5.8 times larger than that of bare RuO 2 (2.9 Wh kg -1 ). The much improved electrochemical performances could be attributed to the dispersive action and good electronic conductivity of CNTs as well as the pinning effect for nanosized RuO 2 particles on the CNTs' surfaces.

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