Constructing three-dimensional ordered porous MoS2/C hierarchies for excellent high-rate long-life pseudocapacitive sodium storage

Abstract

Pseudocapacitive energy storage offers short charging time, long-term cycling stability and high-rate capability, but developing nanostructured electrodes with high pseudocapacitance is still challenging. Herein, we present a facile template-assisted nanocasting method to fabricate three-dimensional (3D) ordered porous MoS2/C hierarchical nanostructures through simultaneous thermal decomposition of the (NH4)2MoS4/(C6H9NO)n/SiO2 mixture by annealing and subsequent template removal. The interplanar spacing along (0 0 2) plane of MoS2 is greatly expanded owing to the incorporation of the PVP-derived carbon species, which also effectively enhance the structural stability of the overall hierarchies composing of interconnected hollow MoS2/C spheres with ultrathin shells and vast macro/mesoporous structure. These novel structure characteristics endow the as-prepared MoS2/C hierarchies with many advantages for sodium storage, ex., lower Na+ intercalation barrier, higher penetration of electrolyte and larger surface active sites. When applied as anode materials for sodium ion batteries (SIBs), the as-prepared MoS2/C exhibits outstanding electrochemical properties, delivering a high reversible capacity of 412 mAh/g after 500 cycles at 2 A/g, and remarkably excellent rate capacities of 156/128/76 mAh/g at 10/20/50 A/g after 5000 cycles, respectively. The excellent cycle stability and rate capability are attributed to the unique 3D ordered porous nanostructure, in which the conductive carbon matrices and the enlarged van der Waals gaps in the layered MoS2 synergistically result in the ultrahigh pseudocapacitance contribution in sodium storage.