High‐Performance Asymmetric Supercapacitors Based on Monodisperse CuO @C Polyhedron Nanocomposites

Herein, CuO nanocrystals spatially embedded inside carbon polyhedron (CuO@C) derived via morphology‐preserved transformation of metal–organic frameworks (MOFs) are utilized for high‐performance asymmetric supercapacitors (SCs). Using a conventional MOF (several micrometers in size), pore‐filling with polymer inside MOF (polymer@MOF) via vapor‐phase polymerization (VPP) process was achieved that amount of polymer used for VPP can be readily adjusted to control the carbon content of CuO@C after thermolysis and subsequent oxidation processes. When monodisperse and nano‐sized MOF is used for CuO@C (denoted as nCuO@C_1), it presents superior electrochemical performance because monodispersity and smaller size reduce interfacial resistance and promote mass‐transport property, respectively. Asymmetric SC of nCuO@C_1 with carbon sphere (CS) as a counter electrode presents excellent energy density of 55.47 Wh/kg and long‐term stability of 88.7% at 5000 cycles, comparable to the best MO‐based asymmetric SCs derived from MOFs.