Hollow and Hierarchical Cobalt–Metal Organic Framework@CoCr 2 O 4 Microplate Array as a Battery‐Type Electrode for High‐Performance Hybrid Supercapacitors

Hollow metal-organic frameworks (MOFs) and their derived materials have shown fascinating structural complexity, such as diverse morphology, tunable porosity and hierarchical structure, which largely extends their intrinsic applications, especially in electrochemical energy storage and conversion. Herein, a hollow and hierarchical Co–MOF@CoCr2O4 microplate array on nickel foam was successfully prepared through a simple one-step in situ conversion strategy, in which Co–MOF served both as self-supporting etching template and as a self-sacrificing ion-exchange template. When used as a battery-type electrode for advanced hybrid supercapacitors, the Co–MOF@CoCr2O4 composite expressed a high specific capacity of 596.8 C g−1 at 0.4 A g−1, excellent rate properties (72.6 % retention rate at 10 A g−1 compared with the initial capacitance at 0.4 A g−1) and good cycling stability (85.1 % retention over 5000 cycles). Furthermore, a fabricated hybrid supercapacitor device reached a high energy density of 0.4 mWh cm−2 (34.36 Wh kg−1) at a power density of 2.34 mW cm−2 (201.03 W kg−1), and superior cycle stability (96.2 % retention over 5000 cycles). These enhanced electrochemical behaviors indicated that this advanced approach can be extended to design various hollow and hierarchical structural MOF/bimetallic-oxide-based composite arrays for high-performance hybrid supercapacitors.