Mushroom-like cobalt nickle metaphosphate@nickel diselenide core-shell nanorods for asymmetric supercapacitors

Although transition metal metaphosphates (TMPOs) display special physical/chemical features and high theoretical capacities, their applications for supercapacitors (SCs) are still restricted by their low energy densities and inferior cycling stability. Herein, a novel strategy has been proposed to address these issues through in situ construction of cobalt nickle metaphosphate (Co0.2Ni0.8(PO3)2)@nickel diselenide (NiSe2) core-shell heterostructure on carbon paper (CP) as a self-supporting flexible electrode for SCs. Particularly, this unique mushroom-like porous nanoarchitecture assembled by one-dimensional (1D) Co0.2Ni0.8(PO3)2 nanorods and zero-dimensional (0D) NiSe2 nanospheres can expose abundant active sites and afford multi-dimensional channels, which favors rapid electron ions/electron transfer, accelerates the reaction kinetics, and alleviates volume changes during charging/discharging processes. Profiting from its well-aligned 1D/0D nanostructure and strong synergistic effect between Co0.2Ni0.8(PO3)2 and NiSe2, the Co0.2Ni0.8(PO3)2@NiSe2/CP electrode delivers a specific capacity of 219.4 mAh/g/0.414 mAh cm-2 at 1 A/g and good cycling stability with capacity retention of 90.7% after 5000 cycles, outperforming many previously reported TMPO-based electrodes in literature. Impressively, an asymmetric supercapacitor (ASC) device assembled with Co0.2Ni0.8(PO3)2@NiSe2 as cathode and porous carbon as anode achieves an energy density of 69.2 Wh kg-1 at 736.0 W kg-1 and maintains a capacity retention of 97.6% after 20,000 charge-discharge cycles. This work provides an efficient approach to design multi-dimensional hybrid nanomaterials for high-performance SCs. (c) 2023 Elsevier Inc. All rights reserved.

Automated summary

A novel strategy is proposed to improve the energy density and cycling stability of transition metal metaphosphates (TMPOs) for supercapacitors. A core-shell heterostructure of cobalt nickel metaphosphate (Co0.2Ni0.8(PO3)2)@nickel diselenide (NiSe2) is constructed on carbon paper as a flexible electrode. The electrode exhibits a specific capacity of 219.4 mAh/g/0.414 mAh cm-2 at 1 A/g and good cycling stability with capacity retention of 90.7% after 5000 cycles, surpassing previously reported TMPO-based electrodes. An asymmetric supercapacitor (ASC) device assembled with this electrode achieves an energy density of 69.2 Wh kg-1 at 736.0 W kg-1 and maintains a capacity retention of 97.6% after 20,000 charge-discharge cycles.