Self‐Assembling Synthesis of Free‐standing Nanoporous Graphene–Transition‐Metal Oxide Flexible Electrodes for High‐Performance Lithium‐Ion Batteries and Supercapacitors

Abstract

The synthesis of nanoporous graphene by a convenient carbon nanofiber assisted self-assembly approach is reported. Porous structures with large pore volumes, high surface areas, and well-controlled pore sizes were achieved by employing spherical silica as hard templates with different diameters. Through a general wet-immersion method, transition-metal oxide (Fe₃O₄, Co₃O₄, NiO) nanocrystals can be easily loaded into nanoporous graphene papers to form three-dimensional flexible nanoarchitectures. When directly applied as electrodes in lithium-ion batteries and supercapacitors, the materials exhibited superior electrochemical performances, including an ultra-high specific capacity, an extended long cycle life, and a high rate capability. In particular, nanoporous Fe₃O₄–graphene composites can deliver a reversible specific capacity of 1427.5 mAh g⁻¹ at a high current density of 1000 mA g⁻¹ as anode materials in lithium-ion batteries. Furthermore, nanoporous Co₃O₄–graphene composites achieved a high supercapacitance of 424.2 F g⁻¹. This work demonstrated that the as-developed freestanding nanoporous graphene papers could have significant potential for energy storage and conversion applications.