Unveiling the redox electrochemistry of 1D,urchin-like vanadium sulfide electrodes for high-performance hybrid supercapacitors

Exploring novel versatile electrode materials with outstanding electrochemical performance is the key to the development of advanced energy conversion and storage devices.In this work,we aim to construct new-fangled one-dimensional(1D)quasi-layered patronite vanadium tetrasulfide(VS_(4))nanostructures by using different sulfur sources,namely thiourea,thioacetamide,and L-cysteine through an ethyleneaminetetraacetic-acid(EDTA)-mediated solvothermal process.The as-prepared VS4exhibits several unique morphologies such as urchin,fluffy nanoflower,and polyhedron with appropriate surface areas.Among the prepared nanostructures,the VS_(4)-1@NF nanostructure exhibited excellent electrochemical properties in 6 M KOH solution,and we explored its redox electrochemistry in detail.The asprepared VS_(4)-1@NF electrode exhibited battery-type redox characteristics with the highest capacity of280 C g^(-1)in a three-electrode assembly.Moreover,it offered a capacity of 123 F g^(-1)in a hybrid twoelectrode set-up at 1 A g^(-1)with the highest specific energy and specific power of 38.5 W h kg^(-1)and750 W kg^(-1),respectively.Furthermore,to ensure the practical applicability and real-world performance of the prepared hybrid AC@NF//VS_(4)-1@NF cell,we performed a cycling stability test with more than 5,000galvanostatic charge–discharge cycles at 2 A g^(-1),and the cell retained around 84.7%of its capacitance even after 5,000 cycles with a CE of 96.1%.

Exploring the experimental study and density functional theory calculations of symmetric and asymmetric chalcogen atoms interacted molybdenum dichalcogenides for lithium-ion batteries

Two-dimensional asymmetric chalcogen atoms attached to Janus nanoparticles have fascinated research attention owing to their distinctive properties and characteristics for various applications.This paper proposed a facile synthesis to produce efficient molybdenum-based symmetric and asymmetric chalcogens bounded by X Mo X and TeMo X nanostructures.Subsequently,the fabricated X Mo X and TeMo X nanostruc-tures were employed as anodes for lithiumion batteries(LIBs).Assembled LIBs using TeMoS and TeMoSe Janus anodes achieved 2610 and 2073 mAh g^(-1)reversible capacity at 0.1 A g^(-1),respectively for the halfcell configuration,which is outstanding performance compared with previous reports.Superior rate capability performances at 0.1-20 A g^(-1)and exceptional cycling solidity confirmed high charge and discharge capacities for TeMo X Janus lithium-ion battery anodes.In addition,the full cell device with TeMoS//LiCoO_(2)configuration explored the discharge capacity of 1605 mAh g^(-1)at 0.1 A g^(-1)which suggests their excellent electrochemical characteristics.The density functional theory approximations established the significance of assembled symmetric and asymmetric chalcogen atoms interacted with X Mo X and TeMo X anode materials for LIBs.Thus,the present investigation supports a new approach to creating two-dimensional materials based on asymmetric chalcogen atoms with core metal to effectively increase desirable energy storage characteristics.

Thickness-dependent monochalcogenide GeSe-based CBRAM for memory and artificial electronic synapses

Investigating the promising chalcogenide materials for the development of memory and advanced neuromorphic computing applications is a critical step in realizing electronic memory and synaptic devices that can efficiently emulate biological synaptic functions.However,the assessment of monochalcogenide materials for the fabrication of highly scalable memory and electronic synaptic devices that can accurately mimic synaptic functions remain limited.In the present study,we investigated the thickness-dependent resistive switching(RS)behavior of conductive bridge random access memory(CBRAM)based on a monochalcogenide GeSe switching medium for its possible application in high-performance memory and electronic synapses.GeSe thin films of different thicknesses(6,13,24,35,47,and 56 nm)were deposited via sputtering to fabricate CBRAM devices with a stacking sequence of Ag/GeSe/Pt/Ti/SiO_(2).The devices exhibited compliance current(CC)-free and electroforming-free RS with highly stable endurance and retention characteristics with no major degradation.All devices with a thickness of 6 nm had a low-resistance state(LRS),which required an initial reset to ensure reliable switching cycles.The devices with a thickness of 47 nm and above exhibited the co-existence of unipolar resistive switching(U-RS)and bipolar resistive switching(B-RS)with the CC-controlled transition between the two switching behaviors.Multilevel resistance states in the 24-nm device between a high-resistance state(HRS)and an LRS were achieved by controlling the set-CC(from 5 mA to CC-free)and the reset stop voltage(from–0.5 to–1.0 V)during the set and reset processes,respectively.The analog RS behavior of the device was further investigated with appropriate pulse measurements to emulate vital synaptic functions,including long-term potentiation(LTP),long-term depression(LTD),spike-rate-dependent plasticity(SRDP),spike-timing-dependent plasticity(STDP),paired-pulse facilitation(PPF),paired-pulse depression(PPD)and post-tetanic potentiation(PTP).Overall,the detailed investigation of thickness-dependent GeSe monochalcogenide material indicates that it is a highly suitable candidate for use in highly scalable memory devices and electronic synapses for neuromorphic computing applications.

A progressive route for tailoring electrical transport in MoS2

Typically, molybdenum disulfide （MoS2） synthesized by chemical vapor deposition （CVD） is polycrystalline; as a result, the scattering of charge carriers at grain boundaries can lead to performances lower than those observed in exfoliated single-crystal MoS2. Until now, the electrical properties of grain boundaries have been indirectly studied without accurate knowledge of their location. Here, we present a technique to measure the electrical behavior of individual grain boundaries in CVD-grown MoS2, imaged with the help of aligned liquid crystals. Unexpectedly, the electrical conductance decreased by three orders of magnitude for the grain boundaries with the lowest on/off ratio. Our study provides a useful technique to fabricate devices on a single-crystal area, using optimized growth conditions and device geometry. The photoresponse, studied within a MoS2 single grain, showed that the device responsivity was comparable with that of the exfoliated MoS2-based photodetectors.