3D Free‐Standing NiCo₂O₄@graphene Foam for High‐Performance Supercapacitors

Abstract

Abstract Free‐standing NiCo 2 O 4 @graphene 3D foams were prepared by using a controllable freeze‐casting method (CFC). In this designed method, the amount of water governs the size and shape of the ice upon introducing the material into a freeze‐drying system. By this means, controllable pore size and aligned nanostructures can be achieved. In the free‐standing foam, the reduced graphene oxide (RGO) sheets form a highly conductive skeleton with high surface area to support the uniform distribution of NiCo 2 O 4 nanoparticles on graphene sheets. When applied as electrode materials for supercapacitors, this dense NiCo 2 O 4 @graphene foam material exhibited a high capacitance of 562 F g −1 at a current density of 2 A g −1 , and an excellent cycling performance at a high current density of 10 A g −1 . Compression testing revealed that the 3D NiCo 2 O 4 @graphene foam possesses strong mechanical properties, and is able to support 20,000 times of its own weight. The novel synthesis method can be extended to prepare other 3D porous foam materials for diverse applications.