Rational design of hierarchical nanoporous yolk-shell Co9S8@ZnGa2S4 heterostructured cages as novel electrode for energy storage systems

Abstract

State-of-the-art nanomaterials with multi-components and complex topologies demonstrate tremendous potential in fabricating electrode materials with high performance which are used in green energy storage systems. Thereby, we report for the first time on the synthesis of hierarchical yolk-shell Co9S8@ZnGa2S4 heterostructured cages (HYC-CS@ZGS) by a facile metal−organic framework (MOF)-assisted approach as a new electrode material for enhanced hybrid supercapacitors (HSCs). Starting with a solid zeolitic imidazolate framework (ZIFs; termed ZIF-67) as the template, ZIF-67@ZIF-8 core-shell polyhedrons (CSPs) are obtained through an epitaxial growth process. Afterward, ZIF-67@ZIF-8 CSPs are controllably transformed into HYC-CS@ZGS via a reflux procedure. Taking advantage of the synergistic effects between the constituent metals and the hierarchical hollow geometry, the organized HYC-CS@ZGS cages exhibit superb electrochemical performance for supercapacitors (SCs). As a result, the electrode demonstrates an ultrahigh specific capacity of 1018C g−1 at 5 mA cm−2 with a 61 % capacity retention at an ultrahigh current density of 187.5 mA cm−2. Consequently, the assembled HYC-CS@ZGS//AC device renders the highest specific energy of 61.9 W h kg−1 at a specific power density of 64 kW kg−1 with excellent cycle life (just 8.7 % loss after 10,000 cycles).