Electronic structure and electrochemical performance of CoS2/MoS2 nanosheet composite: Simulation calculation and experimental investigation

Conductive CoS2 and cycling stable MoS2 are integrated to form the interconnected CoS2/MoS2 nanosheet composite with electroactive interface grown on Mo foil substrate to act as high-performance supercapacitor anode material with electrochemical and mechanical stability. The band gap and density of state of CoS2/MoS2 determined by density functional theory simulation calculation indicates its improved electrical conductivity. The interface binding energy and differential charge density reveal that strong crystal interface interaction between MoS2(002) and CoS2(111) enables effective charge transfer in interconnected CoS2/MoS2 nanosheet composite. CoS2/MoS2 exhibits higher specific capacitance of 605.77 mF cm(-2) than MoS2 of 218.1 mF cm(-2) at 1.0 mA cm(-2) in 0.5 M Na2SO4. The rate capacitance retention is improved from 57.8% of MoS2 to 82.8% of CoS2/MoS2 at 1-10 mA cm(-2). The high cycling stability is achieved for MoS2 (100.2%) and CoS2/MoS2 (104.05%) after 5000 cycles at 10 mA cm(-2) due to self-activation of multilayered MoS2. An asymmetric solid-state supercapacitor using CoS2/MoS2 anode and MnO2/carbon paper cathode achieves a capacitance of 4.32 F cm(-3) at 1.0 mA cm(-2) and an energy density of 1.944 mWh cm(-3) at a power density of 18 mW cm(-3), 97.8% after 5000 cycles at 5.0 mA cm(-2), presenting effective energy storage. (C) 2020 Elsevier Ltd. All rights reserved.