A new hexacyanoferrate nanosheet array converted from copper oxide as a high-performance binder-free energy storage electrode

Abstract Coordination Supramolecular Networks (CSNs) is attracting more and more attention in the energy storage field because of its numerous merits such as dynamic structural reversibility and porosity. In this work, a binder-free electrode of CSN (copper hexacyanoferrate, CuHCF) nanosheet array on carbon cloth (CC@CuHCF) has been fabricated by in-situ conversion strategy. The initial CuO nanosheets can be converted to CuHCF hierarchical structure by competitive coordination reactions between the [Fe(CN) 6 ] −3 and 1,3,5-Benzenetricarboxylic acid (H 3 BTC). Benefitting from the good dynamic structural reversibility of CSNs, large ionic channels in the CuHCF lattice and hierarchical structure of CC@CuHCF, the electrode delivers a high areal capacitance/capacity of 1441.4 mF cm −2 /1441.4 mC cm −2 , superior rate capability (∼75% of its initial capacitance/capacity when the current densities increased from 2 to 30 mA cm −2 ) and good cycling performance (∼87% retention after 2000 cycles at 30 mA cm −2 ). An asymmetric supercapacitor assembled with CC@CuHCF as positive electrode and activated carbon as negative electrode (CC@CuHCF//AC) exhibits a high energy density of 78.8 μW h cm −2 , further demonstrating its application potential. This nanosheet's strategy may provide a guideline for fabricating high active electrodes of energy storage from traditional bulk coordination supramolecular networks.