Rational engineering of hierarchical mesoporous CuxFeySe battery-type electrodes for asymmetric hybrid supercapacitors

Abstract

Highly-ranked positive electrode materials with distinct electrochemical properties and appropriate designs of heterostructured porous architectures integrating mixed transition metal selenides are necessary to boost energy storage capability, which thus have been intensively investigated in the recent years. In this work, we develop a one-step chemical deposition method to grow 3D copper iron selenides (CuxFeySe) heterostructures on the surface of a nickel foam (NF) current collector. The macroporous skeleton of NF not only boosts the homogeneous growth of CuxFeySe architectures but also improves the electrical conductivity of resultant electrodes due to the robust mechanical strength at the junction. The effect of Cu2+/Fe2+ ions is also investigated and noticeably contributed to electrochemical performance. Benefitting from the synergetic effect of integrated Cu and Fe ions with different chemical states, improved electronic configuration, and effective electron/ion transport rate, the battery-type Cu7.5Fe7.5Se electrode delivers a high specific capacity of 186.1 mAh g−1 at a current density of 1 A g−1 with an enhanced capacity retention (63.7% at 50 A g−1). Moreover, the asymmetric supercapacitor (ASC) device fabricated with the self-standing Cu7.5Fe7.5Se electrode and benchmark activated carbon (AC) as the positive and negative electrodes, respectively realizes a large cell potential of 1.5 V and exhibits a high specific capacity of 70 mAh g−1 at 1 A g−1 and a good rate capability (61.6% at 25 A g−1). The assembled device reaches a maximum energy density of ~74.2 W h kg−1 at a power density of 1058.3 W kg−1 together with an appropriate lifespan (91.3% after 8000 cycles at 12 A g−1).