RESUMEN
Zinc-ion batteries (ZIBs) have attracted tremendous interest from the scientific community in recent years due to their extreme safety, cost-effectiveness, environmental benignity and the unique properties of the Zn anode. However, more suitable cathode materials are needed to achieve their potential widespread applications. MoS2, a 2D layered material with fascinating properties, could also serve as a cathode in ZIBs but is rarely studied due to its limited interlayer spacing, poor ionic/electronic conductivity and hydrophobicity. In this work, we report a facile hydrothermal method for synthesizing crystal water-intercalated MoS2 nanosheets and their application in efficient Zn-ion storage. Morphological characterization reveals the average thickness of the nanosheets to be 15.2 nm. With a large interlayer spacing (0.79 nm), high 1T content (49.7%) and high defects, MoS2·nH2O achieves a high discharge capacity of 197 mA h g-1 at 0.1 A g-1 in an aqueous 2 M ZnSO4 electrolyte. Moreover, it exhibits modest cyclic stability with 55% capacity retention after 1000 charge/discharge cycles. Furthermore, we evaluated the charge storage kinetics of crystal water-intercalated MoS2 nanosheets and realized that the electrochemical reaction is diffusion dominated with a diffusion coefficient of 10-10 to 10-13 cm2 s-1 in a 0.3 to 1.3 V potential window. This simple and cost-effective strategy for improving the performance of ZIBs by crystal water intercalation in 2D cathode materials will pave the way for their commercial-level grid-scale applications.
RESUMEN
A novel one-step method for fabricating vanadium telluride nanobelt composites for high-performance supercapacitor applications is reported. The nanobelts are realized by direct tellurization of vanadium oxide in-situ formed via decomposition of ammonium metavanadate in argon atmosphere. Use of melamine as precursor helps in forming graphitic carbon layers during pyrolization on which the nanobelts are grafted. Morphological analysis suggests interconnected nanobelts of â¼23.0 nm width coming out of carbon structure. As pseudocapacitive electrode, vanadium telluride/carbon (C) composite exhibits interesting electrochemical performance within a potential window of 0-1.0 V in 1.0 M sodium sulfate electrolyte along with excellent capacitance retention during 5000 cycles. In-depth analysis suggests that the charge storage mechanism in the composite is governed by both diffusion-controlled and diffusion-independent processes with the former dominating at slower scan rates and later at faster scan rates. The asymmetric supercapacitor assembled using vanadium telluride/C and activated charcoal (AC) as respective positive and negative electrodes exhibited an energy/power combination of 19.3 Wh/kg and 1.8 kW/kg within a potential window of 0-1.8 V in aqueous electrolyte. This strategy to improve capacitance along with potential window in an aqueous electrolyte would facilitate development of high-performance energy storage devices with metal chalcogenides.
