Strip-like Co-based metal–organic framework as electrode material for supercapacitors

Abstract

The cobalt-based metal–organic framework (Co-MOF) as an electrode material with satisfied electrochemical performances has received much attention in energy storage field. Herein, a strip-like Co-MOF was fabricated by a simple one-step solvothermal strategy. In which, the strips are of distinct lengths and thicknesses, and haphazardly lap together to form a stable structure similar to a bird's nest that could provide more moderation space for the volume expansion of the Co-MOF as electrode material in charge and discharge process. The unique structure shows the characteristics of hierarchical pores, which could effectively improve the specific surface area of the Co-MOF material, thereby enhancing the storage of electrochemical energy. The strip-like Co-MOF is endowed with large specific surface area of 643.5 m²/g, high specific capacity of 135.1 C/g at a current density of 0.5 A/g, and good capacitance retention of 91.7% after 2000 cycles at 5 A/g. Moreover, the asymmetric supercapacitor device assembled by using the strip-like Co-MOF as cathode and commercial activated carbon (AC) as anode exhibits a specific capacitance of 58.3 F/g at the current density of 0.5 A/g in a voltage window of 1.55 V, and the maximum energy density is 19.5 Wh/kg at a power density of 389 W/kg. The novel strategy to construct unique microstructure MOF with good properties could be applied to prepare other MOF-based functional materials for various applications.