Hierarchically designed MoWSe2/WO3/C anode for fast and efficient Na+ storage

Abstract

Exploring anode materials with high energy and power density is one of the critical milestones in developing sodium-ion batteries/capacitors (SIBs/SICs). Here, the Mo and W-based bimetallic organic framework (Mo-W-MOF) with core–shell structure is first formed by a facile strategy, followed by a selenization and carbonization strategy to finally prepare multileveled MoWSe2/WO3/C anode materials with core–shell petal like curled nanosheet structure. Between the petal (MoSe2)-core (WO3) structure, the formation of WSe2 flakes by partial selenization on the surface of WO3 serves as a heterogeneous connection between MoSe2 and WO3. The enlarged layer distance (0.677 nm) between MoSe2 and WSe2 can facilitate the rapid transfer of Na+ and electrons. The density functional theory (DFT) calculations verify that the MoWSe2/WO3/C heterostructure performs excellent metallic properties. Ex-situ X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) confirm the activation process from the initial insertion reaction to the later conversion reaction. Resultantly, when employed as the anode of SIBs, a remarkable capacity of 384.3 mA h g−1 after 950 cycles at 10 A g−1 is performed. Furthermore, the SICs assembled with commercial activated carbon (AC) as the cathode exhibits a remarkable energy density of 81.86 W h kg−1 (at 190 W kg−1) and 72.83 W h kg−1(at 3800 W kg−1). The unique structural design and the reaction investigation of the electrode process can provide a reference for the development of transition metal chalcogenides anodes.