Conjugated cobalt-based metal complex nanosheet for fabricating high-performance supercapacitor electrode

In order to cope with the increasingly serious problem of energy shortage, supercapacitors have been developed as a clean and renewable energy source, and the supercapacitors with excellent energy density and long cycle life are imperative. Here, by employing a facile liquid–liquid (L-L) interfacial method at room temperature (RT), a set of two-dimensional (2D) metal complex nanosheets N1-N3 have been synthesized by the facile coordination between Co²⁺ ion and 2,3,6,7,10,11-hexaiminotriphenylene (HITP). Given the layered superstructure with well-ordered nanopores, the N1-N3 electrodes displayed excellent capacities of 4751.9, 5770.9 and 6075.2 F g⁻¹ at 1 A g⁻¹, and a good cyclic stability with 92.1% capacity retention after 1000 cycles for the N3 electrode. The asymmetric supercapacitor device with N3 as the positive electrode delivers a maximum energy density of 238.2 Wh kg⁻¹ at a power density of 1610.1 W kg⁻¹ and an excellent cycling stability with a capacitance retention of 109.1% after 5000 cycles. This is the best electroactive bottom-up metal complex nanosheet reported so far for use in supercapacitor, which greatly expands the applicability of this 2D nanomaterial in energy device applications.