Abstract
Growing concerns regarding the safety, flammability and hazards posed by Li-ion systems have led to research on alternative rechargeable metal-ion electrochemical storage technologies. Among the most notable of these are Na-ion supercapacitors and batteries, motivated, in part, by the similar electrochemistry of Li and Na ions. However, sodium ion batteries (SIBs) come with their own set of issues, especially the large size of the Na+ ion, its relatively sluggish kinetics and low energy densities. This makes the development of novel materials and appropriate electrode architecture of absolute significance. Transition metal dichalcogenides (TMDs) have attracted a lot of attention in this regard due to their relative ease of exfoliation, diverse morphologies and architectures with superior electronic properties. Here, we study the electrochemical performance of Mo-based two-dimensional (2D) layered TMDs (e.g. MoS2, MoSe2 and MoTe2), exfoliated in a superacid, for battery and supercapacitor applications. The exfoliated TMD flakes were interfaced with reduced graphene oxide (rGO) to be used as composite electrodes. Electron microscopy, elemental mapping and Raman spectra were used to analyse the exfoliated material and confirm the formation of 2D TMD/rGO layer morphology. For supercapacitor applications in aqueous electrolyte, the sulfide-based TMD (MoS2) exhibited the best performance, providing an areal capacitance of 60.25 mF cm−2. For SIB applications, TMD electrodes exhibited significantly higher charge capacities than the neat rGO electrode. The initial desodiation capacities for the composite electrodes are 468.84 mAh g−1 (1687.82 C g−1), 399.10 mAh g−1 (1436.76 C g−1) and 387.36 mAh g−1 (1394.49 C g−1) for MoS2, MoSe2 and MoTe2, respectively. Also, the MoS2 and MoSe2 composite electrodes provided a coulombic efficiency of near 100 % after a few initial cycles.
Highlights
Batteries and supercapacitors are being considered for powering an increasingly diverse range of applications from stationary solar/wind energy farms, to electronic devices like wearable electronics and microchips [1]
The images indicate the formation of a stacked, few-layered morphology and the absence of single-layered flakes can be attributed to the volume/morphology of the bulk Transition metal dichalcogenides (TMDs) precursor, the type and strength of acid used, and the power used during the sonication process [27]
This is a feature of exfoliated TMDs and a similar appearance has been reported in the literature [28,29]
Summary
Batteries and supercapacitors are being considered for powering an increasingly diverse range of applications from stationary solar/wind energy farms, to electronic devices like wearable electronics and microchips [1]. The high cost of Li especially hinders applications where large quantities are needed, i.e. in medium- and large-scale grid storage applications [8] These drawbacks have encouraged an ongoing search for non-Li-ion-based rechargeable energy storage devices, among which Na, Mg, Al and K-ion systems are at the forefront [9,10,11]. Transition metal dichalcogenides (TMDs) have drawn significant research attention lately because of their unique properties [19,20,21] This class of materials can offer two-dimensional (2D) layered morphologies that exhibit large surface areas, and enhanced electrochemical kinetics coupled with low volume changes upon ionic intercalation. This manuscript, aims to study the effect of exfoliating these materials in a novel way, as well as to study their viability as energy storage materials and to probe into their electrochemical phenomena under both aqueous and organic electrolyte environments
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
