Influence of Co-MOF morphological modulation on its electrochemical performance

Abstract

The direct use of the original metal-organic framework (MOF) as an electrode material can reduce energy consumption and save costs during the commercialization of MOF-based energy storage materials. In this work, three kinds of ammonium solutions with different anions are introduced in the synthesis process and three forms of Co-based MOFs with different appearances are obtained: Co-BTC block, where BTC is trimesic acid; Co-BTC block microspheres; and Co-BTC nanoblock microspheres (CTNBMs). The CTNBMs have the highest specific capacitance among the three, which reveals that the nanonization of MOFs can effectively improve their energy storage performance. The CTNBMs exhibit a specific capacitance of 427.8 F g−1 at 0.5 A g−1 with a capacitance retention of 73.5% at 10 A g−1. The energy storage mechanism shows that CTNBMs are affected mainly by diffusion control during the electrochemical process. Cyclic stability measurements demonstrate that the capacitance retention of CTNBMs after 3000 cycles at 8 A g−1 is 85.9%, which is the best of the three as-prepared materials. In addition, the assembled CTNBM//activated carbon asymmetric supercapacitor device has a maximum energy density of 30.6 W h kg−1 at a power density of 349.7 W kg−1.