Metallic 1T-MoS2 coupled with MXene towards ultra-high rate-capabilities for supercapacitors

Abstract

Metallic 1T-phase MoS₂ (1T-MoS₂) nanosheets with large interlayer spacing are considered to be a high-energy electrode material for use in supercapacitors; however, the electrochemical storage mechanism of 1T-MoS₂ involves ion intercalation, resulting in energy storage being limited at high current densities and showing poor rate capability. Here, a 1T-MoS₂/Ti₃C₂T_x heterostructure was assembled from metallic 1T-MoS₂ nanosheets coupled with a Ti₃C₂ MXene through one-pot hydrothermal synthesis, and the electrochemical storage mechanisms were investigated. The electrochemical advantages of 1T-MoS₂ and Ti₃C₂T_x can be united via synergistic interplay in the heterostructure. The high specific capacitance is attributed to the metallic properties and the large interlayer spacing of the 1T-MoS₂ component. More importantly, ultra-high rate capability is realized due to fast electron and ion transport originating from Ti₃C₂T_x. In addition, an all-solid-state flexible asymmetric aqueous supercapacitor (FASC) constructed with 1T-MoS₂/Ti₃C₂T_x as the negative electrode and δ-MnO₂ as the positive electrode shows a wide potential window of 1.8 V and a high areal energy density of 68.8 μW h cm⁻² at 4500 μW cm⁻². This work will provide a reference for studying electrochemical storage mechanisms in heterostructures, and it demonstrates the promise of the 1T-MoS₂/MXene heterostructure for supercapacitor use.