A variational method guided confining tip discharge for MOF-derived supercapacitors

Abstract

Nanosized electrode materials have received wide attention in electrochemistry since their large specific surface areas are the precondition for the excellent performance of electrochemistry, such as supercapacitors, Li-ion batteries, Na-ion batteries, electrocatalysis, photoelectrocatalysis, electrolysis and electrodeposition. However it also leads to the high value of curvature of nanomaterials, causing the unavoidable and non-ignorable leakage currents, and therefore the activity degradation. Here, guided by the variational method, we first theoretically predict that, with giving a certain value of curvature, the paraboloid structure possesses the maximal surface area to greatly reduce the tip-charge, thus guaranteeing the electrochemical performance. Consequently, with using supercapacitors as the model application, this unusual morphological structure was successfully constructed in the metal-organic frameworks (MOFs)-derived Zn-Ni-Co-P@CoP nanowire arrays (ZNCP@CoP NWRs), which largely ensures the ZNCP@CoP NWRs || AC device exhibits an ultralow leakage current of 10.28 μA. The low curvature structure of ZNCP@CoP NWRs also significantly improves the electrochemical performance of supercapacitors with a large specific capacitance of 1483 C g−1 at 1 A g−1 and a high cyclic stability of 80% capacity maintained over 5000 cycles at 5 A g−1. The finding in this work highlights the great potential of the reasonable material design approach for advanced energy applications.