Self -templated construction of hollow trimetallic MnNiCoP yolk-shell spheres assembled with nanosheets as a satisfactory positive electrode material for hybrid supercapacitors.

Abstract

Transition metal phosphides (TMPs) demonstrate excellent potential for supercapacitor electrode materials owing to their good theoretical capacity and great electrical conductivity. The electrochemical features of the electrode materials based on monometallic or bimetallic phosphides are not desirable or satisfactory due to their low rate performance, unfavorable energy density, and short durability. One practical solution to overcome the above problems is to bring in heteroatoms to the structure of the bimetallic materials to create trimetallic phosphides. In this work, brand-new MnNiCoP yolk-shell spheres assembled with nanosheets are synthesized in a facile self-templated way using greatly uniform co-glycerate spheres as sacrificial templates, followed by a phosphorization process. Because of the existence of plenty of oxidation-reduction active sites, great surface area (SA) with mesoporous pathways, high electrical conductivity, and synergistic effect of Mn, Ni, and Co atoms, the fabricated MnNiCoP@NiF electrode demonstrates a considerably increased electrochemical efficiency compared with the bimetallic phosphide MnCoP@NiF electrode. Noticeably, the MnNiCoP@NiF electrode exhibits a great specific capacity of 291.24 mA h g-1 at an applied current density of 1 Ag-1, 80% capacity retention at an applied current density of 20 Ag-1, and 91.3% capacity retention after 14 000 cycles. In addition, a hybrid supercapacitor device with a brand-new positive electrode (MnNiCoP@NiF) and an appropriate negative electrode (AC@NiF) demonstrates an energy density of 57.03 W h kg-1 with a power density of 799.98 W kg-1, plus superb cyclability with 88.41% of the primary capacitance after 14 000 cycles.