Heteroatom Modification of Heterostructured CuS/Mn3O4 with Rich Defects for Solid-State Supercapacitors

Abstract

Heterostructure construction and heteroatom modification are considered as effective approaches to modulate the electronic structure and boost the energy storage activity of electrode materials. Herein, oxygen-modified CuS/Mn3O4 (O-CuS/Mn3O4) heterogeneous nanoflakes with abundant defects are fabricated by solid-state grinding followed by NaBH4 treatment (NBHT) at room temperature using MnCu Prussian blue analogue (MnCu-PBA) as the precursor. During the NBHT, a portion of the sulfur atoms in CuS is removed, and the remaining sites in the lattice are occupied by oxygen in the water, resulting in an oxygen modification. Experimental results and theoretical calculations confirm that heterojunction, defect, and oxygen modification not only greatly facilitate the adsorption of OH– on the surface of the electrode material but also endow improved electrical conductivity, wettability, specific surface area, and active sites. Benefiting from these advantages, O-CuS/Mn3O4 exhibits an excellent specific capacitance of 1307 F g–1 at 1 A g–1. Moreover, the solid-state asymmetric supercapacitor with O-CuS/Mn3O4 and MnO2 (O-CuS/Mn3O4//MnO2) shows an outstanding energy density of 34.4 Wh kg–1 at 800.1 W·kg–1 and cyclic stability with 85.7% capacitance retention after 5000 cycles at 6 A g–1. Our work highlights the integration of heterojunction and oxygen modification to fabricate and optimize the energy storage electrode materials.