Enhanced activity of highly conformal and layered tin sulfide (SnSx) prepared by atomic layer deposition (ALD) on 3D metal scaffold towards high performance supercapacitor electrode
Title
Enhanced activity of highly conformal and layered tin sulfide (SnSx) prepared by atomic layer deposition (ALD) on 3D metal scaffold towards high performance supercapacitor electrode
Layered Sn-based chalcogenides and heterostructures are widely used in batteries and photocatalysis, but its utilizations in a supercapacitor is limited by its structural instability and low conductivity. Here, SnSx thin films are directly and conformally deposited on a three-dimensional (3D) Ni-foam (NF) substrate by atomic layer deposition (ALD), using tetrakis(dimethylamino) tin [TDMASn, ((CH3)(2)N)(4)Sn] and H2S that serves as an electrode for supercapacitor without any additional treatment. Two kinds of ALD-SnSx films grown at 160 degrees C and 180 degrees C are investigated systematically by X-ray diffractometry, Raman spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy (TEM). All of the characterization results indicate that the films deposited at 160 degrees C and 180 degrees C predominantly consist of hexagonal structured-SnS2 and orthorhombic-SnS phases, respectively. Moreover, the highresolution TEM analyses (HRTEM) reveals the (001) oriented polycrystalline hexagonal-SnS2 layered structure for the films grown at 160 degrees C. The double layer capacitance with the composite electrode of SnSx@ NF grown at 160 degrees C is higher than that of SnSx@ NF at 180 degrees C, while pseudocapacitive Faradaic reactions are evident for both SnSx@ NF electrodes. The superior performance as an electrode is directly linked to the layered structure of SnS2. Further, the optimal thickness of ALD-SnSx thin film is found to be 60 nm for the composite electrode of SnSx@ NF grown at 160 degrees C by controlling the number of ALD cycles. The optimized SnSx@ NF electrode delivers an areal capacitance of 805.5 mF/cm(2) at a current density of 0.5 mA/cm(2) and excellent cyclic stability over 5000 charge/discharge cycles.