Synthesis of homogeneous honeycomb MoS2 as the anode material for lithium-ion batteries using chemical vapor deposition and a template method

A honeycomb molybdenum disulfide (MoS2) nanomaterial with a special morphology for use in anodes of lithium-ion batteries was synthesized using a template method and chemical vapor deposition.

A Review on the Application of Cobalt-Based Nanomaterials in Supercapacitors

Among many electrode materials, cobalt-based nanomaterials are widely used in supercapacitors because of their high natural abundance, good electrical conductivity, and high specific capacitance. However, there are still some difficulties to overcome, including poor structural stability and low power density. This paper summarizes the research progress of cobalt-based nanomaterials (cobalt oxide, cobalt hydroxide, cobalt-containing ternary metal oxides, etc.) as electrode materials for supercapacitors in recent years and discusses the preparation methods and properties of the materials. Notably, the focus of this paper is on the strategies to improve the electrochemical properties of these materials. We show that the performance of cobalt-based nanomaterials can be improved by designing their morphologies and, among the many morphologies, the mesoporous structure plays a major role. This is because mesoporous structures can mitigate volume changes and improve the performance of pseudo capacitance. This review is dedicated to the study of several cobalt-based nanomaterials in supercapacitors, and we hope that future scholars will make new breakthroughs in morphology design.

Facile Synthesis of Biocarbon-Based MoS2 Composite for High-Performance Supercapacitor Application

Nanocomposites are gaining high demand for the development of next-generation energy storage devices because of their eco-friendly and cost-effective natures. However, their short-term energy retainability and marginal stability are regarded as hindrances to overcome. In this work, we demonstrate a high-performance supercapacitor fabricated by biocarbon-based MoS₂ (Bio-C/MoS₂) nanoparticles synthesized by a facile hydrothermal approach using date fruits. Here, we report the high specific capacitance for a carbon-based nanocomposite employing the pyrolysis technique of converting agricultural biowaste into a highly affordable energy resource. The biocompatible Bio-C/MoS₂ nanospheres exhibited a high capacitance of 945 F g^-1 at a current density of 0.5 A g^-1 and an excellent reproducing stability of 92% after 10000 charge/discharge cycles. In addition, the Bio-C/MoS₂ NS showed an exceptional power density of 3800-8000 W kg^-1 and an energy density of 74.9-157 Wh kg^-1. The results would pave a new strategy for design of eco-friendly materials toward the high-performance energy storage technology.

Aminated Multiwalled Carbon Nanotube-Doped Magnetic Flower-like WSe2 Nanosheets for Efficient Adsorption in Acidic Wastewater

The water body environment is related to ecological and human health. Adsorption is an effective means to remove pollutants from water bodies. Currently, the common adsorbents suffer from disadvantages such as structural instability and poor adsorption performance under acidic conditions, which not only affect the adsorption efficiency but also cause secondary pollution of water bodies. In this study, a novel aminated multiwalled carbon nanotube-doped flower-like nanocomposite was designed, where the anionic or neutral groups were protonated under acidic conditions, and it displayed a higher adsorption capacity for dyes by ion exchange, represented by methylene blue (MB) and rhodamine B (RB). WSe₂ in the composite increases its adsorption sites. The adsorption efficiency of pollutants in acidic wastewater was enhanced while avoiding secondary contamination. The synthesized composites showed maximum adsorptions of 27.55 and 27.47 mg/g for MB and RB, respectively. The current work offers a novel approach to treating acidic wastewater.

2-Dimensional layered molybdenum disulfide nanosheets and CTAB-assisted molybdenum disulfide nanoflower for high performance supercapacitor application

In this study, the supercapacitor performance of the hydrothermal synthesized molybdenum disulfide (MoS₂) nanosheets and the cetyltrimethylammonium bromide (CTAB)-assisted MoS₂ nanoflower morphology have been investigated. The as-synthesized MoS₂ nanoflower and nanosheet morphology structures were investigated via field emission scanning electron microscopy (FESEM), and the internal microstructure was examined via high resolution-transmission electron microscopy (HR-TEM) technique. The Fourier transform infrared (FT-IR) spectra were obtained to identify the chemical interaction and the functional groups present in the material. The shifting of the binding energy, oxidation states, and elemental identification were conducted by X-ray photon spectroscopy (XPS). The MoS₂ nanoflower possesses surface defects, which produce numerous active sites. The MoS₂ nanoflower and nanosheet electrodes demonstrate the high specific capacitance (C _sp) values of 516 F g^-1 and 438 F g^-1, respectively, at a current density of 1 A g^-1. However, the MoS₂ nanoflower shows high C _sp due to the large surface area with active edges, making them store more energy in the electrode.

Recent progress of hierarchical MoS2 nanostructures for electrochemical energy storage

Hierarchical MoS2 nanostructures are of increasing importance in energy storage via batteries or supercapacitors. Herein, the various hierarchical MoS2 materials as electrochemical electrode are reviewed in detail by classifying the...

Embellishing hierarchical 3D core-shell nanosheet arrays of ZnFe2O4@NiMoO4 onto rGO-Ni foam as a binder-free electrode for asymmetric supercapacitors with excellent electrochemical performance

Tailoring hierarchical hybrid core-shell electrodes with impartial microstructural features and excellent electroactive constituents is crucial for the design of high-performance supercapacitors (SCs). Herein, for the first time, we fabricate uniformly aligned porous ZnFe₂O₄ (ZFO) nanosheet arrays onto reduced graphene oxide-garnished conductive Ni foam (rGO-NF) substrates and subsequently embellish the first layer of ZFO nanosheets with morphology-controlled secondary NiMoO₄ nanosheets to achieve a hierarchical 3D core-shell structure of ZnFe₂O₄@NiMoO₄ nanosheet arrays (NSAs) onto rGO-NF for SC applications. Improving the synergistic effect of the core-shell nanoarchitecture with a conductive rGO-NF substrate, the hierarchical 3D ZFO@NMO NSAs tend to have superb electronic conductivity, tailoribility, effective nanoporous channels, and appropriate roadways for rapid ion/electron transfer, which are required for rapid reversible redox reactions, thus reflecting the excellent electrochemical features, including the excellent specific capacitance, good rate performance, and prolonged cyclic performance of the three electrode assemblies for SCs. An asymmetric supercapacitor (ASC) device composed of ZFO@NMO NSAs@rGO-NF as the cathode and MOF-derived hollow porous carbon (MDHPC) as the anode exhibits a high energy density of 58.6 Wh kg^-1 at a power density of 799 W kg^-1 with prolonged cyclic durability (89.6 % after 7000 cycles), thus indicating its potential applicability towards advanced hybrid SCs.

Fe doped MoS2/polypyrrole microtubes towards efficient peroxidase mimicking and colorimetric sensing application

Molybdenum disulfide (MoS2) nanosheets have been found to exhibit intrinsic peroxidase-like activity that could be applied in colorimetric sensing platforms. However, their poor conductivity and few exposed edge sites often lead to poor catalytic activity, impeding the application of MoS2 nanosheets in enzyme-like catalysis. Here, a novel strategy was developed to selectively deposit Fe-doped MoS2 nanosheets on polypyrrole microtubes to obtain Fe-MoS2@PPy microtubes to address these issues. In the synthesized Fe-MoS2@PPy microtubes, PPy microtubes can not only be used as a conductive support to promote the electron transfer, but also greatly alleviate the aggregations of MoS2 nanosheets, and thus improve the enzyme-like activity. Meanwhile, additional active sites, formed by Fe doping, also endow the catalyst with excellent activity in enzyme-like catalysis. Notably, in the process of sulfidation, the dissolution, redistribution and diffusion result in the disappearance of MoO3@FeOOH cores and the formation of Fe doped MoS2 nanosheets, which significantly facilitate the deposition of Fe-doped MoS2 nanosheets on PPy microtubes. On the basis of the high peroxidase-like catalytic efficiency of the Fe-MoS2@PPy microtubes, a simple and convenient colorimetric strategy for the rapid and sensitive detection of L-cysteine has been developed. This strategy introduces both the PPy layer and Fe doping to increase the conductivity and the density of active sites of MoS2 nanosheets, thus enhancing the catalytic activity and stability. More importantly, Fe-MoS2@PPy microtubes could be used as a good support for loading other materials such as Au and Ag nanoparticles (NPs), forming ternary Fe-MoS2/Ag, Au@PPy nanotubes. This work offers an opportunity to develop low-cost and highly active MoS2-based nanocomposites for promising potential applications in electrochemical energy conversion and medical diagnostics.

Controlled 2H/1T phase transition in MoS2 monolayers by a strong interface with M2C MXenes: a computational study

Due to the high conductivity and abundant active sites, the metallic 1T phase of a two-dimensional molybdenum sulfide monolayer (1T-MoS₂) has witnessed a broad range of potential applications in catalysis, and spintronic and phase-switching devices, which, however, are greatly hampered by its poor stability. Thus, the development of particular strategies to realize the phase transition from the stable 2H phase to the metastable 1T phase for MoS₂ nanosheets is highly desirable. Herein, by means of density functional theory (DFT) computations, we systematically explored the potential of the interfacial interaction of 2H- and 1T-MoS₂ monolayers with a series of M₂C MXenes (M = Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W) for achieving the 2H/1T phase transformation. Our results revealed that the 2H → 1T transition for MoS₂ monolayers can occur thermodynamically by anchoring on Ti₂C, Zr₂C, or Hf₂C substrates with the extremely strong metal-S interaction, which can be well rationalized by the analysis of the charge transfer, work function, and density of states. Specially, these obtained stable 1T-MoS₂/M₂C hybrid materials exhibit excellent metallic features, outstanding magnetism, and enhanced mechanical properties. Our findings provide a new avenue to tune the phase transformation for MoS₂ monolayers by strong interfacial interactions, which helps to further widen the potential applications of MoS₂ monolayers.

Flexible nickel disulfide nanoparticles-anchored carbon nanofiber hybrid mat as a flexible binder-free cathode for solid-state asymmetric supercapacitors

Nickel disulfide nanoparticles (NiS₂NPs)-anchored carbon nanofibers (NiS₂NPs@CNF) hybrid mats were fabricated via the sequential process of stabilization and carbonization of electrospun polyacrylonitrile-based fibers followed by hydrothermal growth of NiS₂NPs on the porous surface of CNFs. The vertical growth of NiS₂NPs on entire surfaces of porous CNFs appeared in the SEM images of hybrid mat. The hierarchical NiS₂NPs@CNF core-shell hybrid nanofibers with 3D interconnected network architecture can endow continuous channels for easy and rapid ionic diffusion to access the electroactive NiS₂NPs. The conductive and interconnected CNF core could facilitate electron transfer to the NiS₂shell. Moreover, the porous CNF as a buffering matrix can resist volumetric deformation during the long-term charge-discharge process. The NiS₂NPs@CNF electrode can yield high specific capacitance (916.3 F g^-1at 0.5 A g^-1) and reveal excellent cycling performances. The solid-state asymmetric supercapacitor (ASC) was fabricated with NiS₂NPs@CNF mat as a binder-free positive electrode and activated carbon cloth as a negative electrode. As-assembled ASC not only produce high specific capacitance (364.8 F g^-1at 0.5 A g^-1) but also exhibit excellent cycling stability (∼92.8% after 5000 cycles). The ASC delivered a remarkably high energy density of 129.7 Wh kg^-1at a power density of 610 W kg^-1. These encouraging results could make this NiS₂NPs@CNF hybrid mat a good choice of cathode material for the fabrication of flexible solid-state ASC for various flexible/wearable electronics.

Luminescent MoS2 Quantum Dots with Tunable Operating Potential for Energy-Enhanced Aqueous Supercapacitors

Wide band gap luminescent MoS₂ quantum dots (QDs) and MoS₂ nanocrystals (NCs) have been synthesized by using laser-assisted chemical vapour deposition and used as an electrode material in supercapacitors. Size-dependent properties of the MoS₂ QDs and NCs were examined by UV-vis absorption, photoluminescence, and Raman spectroscopy. The morphological evolution of the NCs and QDs were characterized by using field emission scanning electron microscopy, high-resolution transmission electron microscopy, and atomic force microscopy. The as-synthesized uniform QDs with a size of ∼2 nm exhibited an extended electrochemical potential window of 0.9 V with a specific capacitance value of 255 F/g, while the NCs values were 205 F/g and 0.8 V and the pristine MoS₂ with values of 105 F/g and 0.6 V at a scan rate of 1 mV s^-1. A shorter conductive pathway and 3D quantum confinement of MoS₂ QDs that exhibited a higher number of active sites ensure that the efficient charge storage kinetics along with the intercalation processes at the available edge sites enable significant widening of operating potential window and enhance the capacitance. The symmetric device constructed with the QDs showed a remarkable device capacitance of 50 F/g at a scan rate of 1 mV s^-1 with an energy density of ∼5.7 W h kg^-1 and achieved an excellent cycle stability of 10,000 consecutive cycles with ∼95% capacitance retention.

Topochemically synthesized MoS2 nanosheets: A high performance electrode for wide-temperature tolerant aqueous supercapacitors

This work describes the formation of two-dimensional molybdenum di-sulfide (MoS₂) nanosheets via topochemical sulfurization of MoO₃ microplates and its applications towards wide-temperature tolerant supercapacitors. Physico-chemical characterizations such as XRD, FE-SEM, HR-TEM, XPS and elemental mapping analysis revealed the formation of MoS₂ nanosheets with lateral size in the range of 200 nm. The electrochemical properties of the MoS₂ electrode using three-electrode configuration tests revealed the presence of pseudocapacitive mechanism of charge-storage with a high capacitance (119.38 F g^-1) from cyclic voltammetry profiles and superior cyclic stability of 95.1% over 2000 cycles. The symmetric supercapacitor (SSC) fabricated using MoS₂ electrodes delivered a high-energy density (6.56 Wh kg^-1) and high-power density (2500 W kg^-1) with long cycle life. The electrochemical performance of the MoS₂ SSC exhibited ~121% improvement at 80 °C compared to that achieved at 20 °C and the mechanism of improved properties were examined with the use of electrochemical impedance spectroscopy. These experimental results indicate usefulness of topochemically synthesized MoS₂ for construction of wide-temperature tolerant supercapacitors that can be useful in a variety of industrial sectors.

Molybdenum disulfide-based materials with enzyme-like characteristics for biological applications

Nanozyme, a kind of nanomaterials with enzymatic activity, has been developing vigorously over the past years owing to its advantages such as low-cost, easy storage, ease of use in harsh environments and so on, compared with natural enzymes. At present, as a typical two-dimensional nanomaterial, molybdenum disulfide (MoS₂) and their hybrids with unexpected enzyme-like activities have caused wide attention. In this review, we mainly investigated the enzyme-like activities of MoS₂ based nanomaterials, including peroxidase-like activity, catalase-like activity and superoxide dismutase-like activity. Furthermore, we systematically introduce recent research progress of MoS₂ based nanomaterials in the fields of biological applications such as radiation protection, cancer therapy, antibacterial, and wound healing. Finally, the current challenges and perspectives of MoS₂ based nanomaterials in the future are also discussed and proposed. We expect this review may be significant to understand the properties of MoS₂ based nanomaterials and the development of two-dimensional nanomaterials with enzyme mimicking activities.

MoS2/cellulose paper coupled with SnS2 quantum dots as 2D/0D electrode for high-performance flexible supercapacitor

The effective incorporation of novel and highly conductive hybrid functional nanomaterials onto flexible and porous substrates is extremely desirable to develop flexible supercapacitors.

Fabrication of ternary composites with polymeric carbon nitride/MoS2/reduced graphene oxide ternary hybrid aerogel as high-performance electrode materials for supercapacitors

Presenting a remarkable ternary hybrid aerogel, as an excellent electrode material with a specific capacitance of 467 Fg−1 and capacitance retention upto 80.4% even after 2000 cycles, demonstrating good stability and improved cyclic performance.

Hierarchical WSe2 nanoflower as a cathode material for rechargeable Mg-ion batteries

Transition metal dichalcogenides (TMDs) have emerged as a promising material in the energy field due to their unique structural arrangement. In this work, ordered flower-like WSe₂ nanosheet was synthesized through simple one-step hydrothermal method, and its cathode application for rechargeable Mg-ion batteries was assessed. The WSe₂ cathode exhibits a high reversible capacity above 265 mAh g^-1 at 50 mA g^-1, excellent cycling life of 90% initial capacitance that can be ceaselessly harvested for 100 cycles at 50 mA g^-1, and superior rate capability of 70% initial capacitance maintained even at the current density of 500 mA g^-1. This work paves the way for the application of WSe₂ cathode in Mg-ion and other rechargeable batteries.

Self-standing heterostructured NiC x -NiFe-NC/biochar as a highly efficient cathode for lithium-oxygen batteries

Lithium-oxygen batteries have attracted research attention due to their low cost and high theoretical capacity. Developing inexpensive and highly efficient cathode materials without using noble metal-based catalysts is highly desirable for practical applications in lithium-oxygen batteries. Herein, a heterostructure of NiFe and NiC x inside of N-doped carbon (NiC x -NiFe-NC) derived from bimetallic Prussian blue supported on biochar was developed as a novel self-standing cathode for lithium-oxygen batteries. The specific discharge capacity of the best sample was 27.14 mAh·cm-2 at a stable discharge voltage of 2.75 V. The hybridization between the d-orbital of Ni and s and p-orbitals of carbon in NiC x , formed at 900 °C, enhanced the electrocatalytic performance due to the synergistic effect between these components. The structure of NiC x -NiFe-NC efficiently improved the electron and ion transfer between the cathode and the electrolyte during the electrochemical processes, resulting in superior electrocatalytic properties in lithium-oxygen batteries. This study indicates that nickel carbide supported on N-doped carbon is a promising cathode material for lithium-oxygen batteries.

Orientated VSe2 nanoparticles anchored on N-doped hollow carbon sphere for high-stable aqueous energy application

Transition metal dichalcogenides (TMDs) have been considered as the promising energy storage materials due to their unique crystalline structure. In this work, the VSe₂ nanoparticles are vertically anchored on N-doping carbon (NC) hollow nanosphere (VSe₂@NC) for aqueous energy application. The electrochemical measurements indicate that the VSe₂@NC electrode exhibits outstanding electrochemical properties with high specific capacitance and excellent cycling life. Moreover, the asymmetric supercapacitor was assembled by using VSe₂@NC cathode and activated carbon anode. It shows high energy density of 85.41 Wh Kg^-1 at a power density of 701.99 W Kg^-1, and high-stable cycling performance of 90% retention after 2000 cycles. The superior properties are attributed to the particular hollow structure design, which accommodates both the high specific capacity of VSe₂ and the desired electrical conductivity of N-doping carbon sphere template.

Antimonene nanosheets with enhanced electrochemical performance for energy storage applications

Antimonene is an exfoliated 2D nanomaterial obtained from bulk antimony. It is a novel class of 2D material for energy storage applications. In the present work, antimonene was synthesized using a high-energy ball milling-sonochemical method. The structural, morphological, thermal, and electrochemical properties of antimonene were comparatively analyzed against bulk antimony. X-ray diffractometry (XRD) analysis confirms the crystal structure and 2D structure of antimonene, as a peak shift was observed. The Raman spectra show the peak shift for the E_g and A_1g modes of vibration of antimony, which confirms the formation of antimonene. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) images depict the exfoliation of antimonene from bulk antimony. Thermal analysis unveiled the thermal stability of antimonene up to 400 °C with only 3% weight loss. X-ray photoelectron spectroscopy (XPS) analysis reveals the formation of antimonene, which is free from contamination. The electrochemical properties of antimony and antimonene were investigated using cyclic voltammetry (CV) and chronopotentiometric (CP) analysis, using 2 M KOH as an electrolyte. Antimonene exhibited a relatively high specific capacitance of 597 F g^-1 compared to ball-milled antimony (101 F g^-1) at a scan rate of 10 mV s^-1. Moreover, electrochemical impedance spectroscopy (EIS) analysis revealed that antimonene has a relatively low equivalence series resistance (RESR) and low charge transfer resistance (RCT) compared to bulk antimony, which favors high electrochemical performance. The cyclic stability of antimonene was studied for 3000 cycles, and the results show high cyclic stability. The electrochemical results demonstrated that antimonene is a promising material for energy storage applications.

Toward Rapid-Charging Sodium-Ion Batteries using Hybrid-Phase Molybdenum Sulfide Selenide-Based Anodes

To attain both high energy density and power density in sodium-ion (Na⁺ ) batteries, the reaction kinetics and structural stability of anodes should be improved by materials optimization. In this work, few-layered molybdenum sulfide selenide (MoSSe) consisting of a mixture of 1T and 2H phases is designed to provide high ionic/electrical conductivities, low Na⁺ diffusion barrier, and stable Na⁺ storage. Reduced graphene oxide (rGO) is used as a conductive matrix to form 3D electron transfer paths. The resulting MoSSe@rGO anode exhibits high capacity and rate performance in both organic and solid-state electrolytes. The ultrafast Na⁺ storage kinetics of the MoSSe@rGO anode is attributed to the surface-dominant reaction process and broad Na⁺ channels. In situ and ex situ measurements are conducted to reveal the Na⁺ storage process in MoSSe@rGO. It is found that the MoS and MoSe bonds effectively limit the dissolution of the active materials. The favorable Na⁺ storage kinetics of the MoSSe@rGO electrode are ascribed to its low adsorption energy of -1.997 eV and low diffusion barrier of 0.087 eV. These results reveal that anion doping of metal sulfides is a feasible strategy to develop sodium-ion batteries with high energy and power densities and long life-span.

Freestanding 1T-Mnx Mo1- x S2- y Sey and MoFe2 S4- z Sez Ultrathin Nanosheet-Structured Electrodes for Highly Efficient Flexible Solid-State Asymmetric Supercapacitors

Fabrication of hierarchical nanosheet arrays of 1T phase of transition-metal dichalcogenides is indeed a critical task, but it holds immense potential for energy storage. A single-step strategy is employed for the fabrication of stable 1T-Mn_x Mo_{1- x} S_{2- y} Se_y and MoFe₂ S_{4- z} Se_z hierarchical nanosheet arrays on carbon cloth as positive and negative electrodes, respectively. The flexible asymmetric supercapacitor constructed with these two electrodes exhibits an excellent electrochemical performance (energy density of ≈69 Wh kg^-1  at a power density of 0.985 kW kg^-1 ) with ultralong cyclic stability of ≈83.5% capacity retention, after 10 000 consecutive cycles. Co-doping of the metal and nonmetal boosts the charge storage ability of the transition-metal chalcogenides following enrichment in the metallic 1T phase, improvement in the surface area, and expansion in the interlayer spacing in tandem, which is the key focus of the present study. This study explicitly demonstrates the exponential enhancement of specific capacity of MoS₂ following intercalation and doping of Mn and Se, and Fe₂ S₃ following doping of Mo and Se could be an ideal direction for the fabrication of novel energy-storage materials with high-energy storage ability.

Three-Dimensional MoS2 Nanodot-Impregnated Nickel Foam Electrodes for High-Performance Supercapacitor Applications

An economical and binder-free electrode was fabricated by impregnation of sub-5 nm MoS₂ nanodots (MoS₂ NDs) onto a three-dimensional (3D) nickel substrate using the facile dip-coating method. The MoS₂ NDs were successfully synthesized by controlled bath sonication of highly crystalline MoS₂ nanosheets. The as-fabricated high-surface area electrode demonstrated promising electrochemical properties. It was observed that the as-synthesized NDs outperformed the layered MoS₂ peers as the electrode for supercapacitors. MoS₂ NDs exhibited an excellent specific capacitance (C _sp) of 395 F/g at a current load of 1.5 A/g in a three-electrode configuration. In addition, the fabricated symmetric supercapacitor demonstrated a C _sp value of 122 F/g at 1 A/g and a cyclic performance of 86% over 1000 cycles with a gravimetric power and energy density of 10,000 W/kg and 22 W h/kg, respectively. Owing to its simple and efficient fabrication and high surface area, such 3D electrodes show high promise for various energy storage devices.

Ultrafine antimony (Sb) nanoparticles encapsulated into a carbon microfiber framework as an excellent LIB anode with a superlong life of more than 5000 cycles

Antimony (Sb) anode has attracted increasing attention given its high theoretical capacity and suitable working potential. Nonetheless, its practical application is largely hindered by huge volume changes during the cyclic process, resulting in unsatisfactory long-term cycled stabilities at high current density. In this work, large-scale ultrafine Sb nanoparticles are functionally designed to encapsulate into a 3D carbon microfiber framework (CMF) via a scalable electrospinning approach followed by a thermal treatment process. This fabrication strategy effectively avoids the change in the volume of the Sb anode and provides a fast conductive network to serve as an efficient 3D e/Li⁺ transport pathway. Benefiting from this novel structural design, an ultrafine Sb nanoparticles@carbon microfiber framework (U-Sb-NPs@CMF) composite anode used for lithium-ion batteries (LIBs) delivers a high reversible capacity of 622 mAh g^-1 after 200 cycles at 0.5 A g^-1 and 507 mAh g^-1 after 2000 cycles at 2 Ag^-1 and a high-capacity retention of 350 mAh g^-1 even after 5000 long-term cycles. These outstanding charge-discharge performances suggest that the U-Sb-NPs@CMF composite is a promising candidate for an anode material in the application of LIBs.

Thermodynamic analysis and kinetic optimization of high-energy batteries based on multi-electron reactions

Multi-electron reaction can be regarded as an effective way of building high-energy systems (>500 W h kg⁻¹). However, some confusions hinder the development of multi-electron mechanisms, such as clear concept, complex reaction, material design and electrolyte optimization and full-cell fabrication. Therefore, this review discusses the basic theories and application bottlenecks of multi-electron mechanisms from the view of thermodynamic and dynamic principles. In future, high-energy batteries, metal anodes and multi-electron cathodes are promising electrode materials with high theoretical capacity and high output voltage. While the primary issue for the multi-electron transfer process is sluggish kinetics, which may be caused by multiple ionic migration, large ionic radius, high reaction energy barrier, low electron conductivity, poor structural stability, etc., it is urgent that feasible and versatile modification methods are summarized and new inspiration proposed in order to break through kinetic constraints. Finally, the remaining challenges and future research directions are revealed in detail, involving the search for high-energy systems, compatibility of full cells, cost control, etc.

Fabrication of noble metal nanoparticles decorated on one dimensional hierarchical polypyrrole@MoS2 microtubes

Herein, we present a facile strategy to fabricate noble metal (Ag, Au, Pd) decorated on PPy@MoS₂ microtubes. As a proof of application, the ternary PPy@MoS₂@Au hybrids reveal excellent enzyme-like catalytic performance.

Fe3O4 nanoparticle decorated three-dimensional porous carbon/MoS2 composites as anodes for high performance lithium-ion batteries

Molybdenum disulfide (MoS2) is a promising anode material for lithium-ion batteries owing to its high theoretical capacity and low cost. However, it exhibits low electrical conductivity and volume expansion, resulting in poor electrochemical performance. In this work, three-dimensional porous carbon/MoS2 composites with Fe3O4 nanoparticles (C-MF) are synthesized via a mix-bake-wash method. The few-layered MoS2 in the porous carbon matrix provides improved electrical conductivity and facilitates lithium ion diffusion, so the composites exhibit a high specific capacity of 939.6 mA h g-1 on average at 0.1 A g-1 and a high rate capability (515.9 mA h g-1 at 5 A g-1). Moreover, the Fe3O4 nanoparticles in C-MF, which are anchored on the composites, improve the specific capacity and effectively mitigate diffusion of lithium polysulfides during cycling, resulting in remarkable cycling stability (590.1 mA h g-1 after 500 cycles at 2 A g-1). This work suggests that not only C-MF but also C@MoS2 with other metal oxides synthesized using this facile strategy have potential for energy-related applications.

Recent Progress on Irradiation-Induced Defect Engineering of Two-Dimensional 2H-MoS2 Few Layers

Atom-thick two-dimensional materials usually possess unique properties compared to their bulk counterparts. Their properties are significantly affected by defects, which could be uncontrollably introduced by irradiation. The effects of electromagnetic irradiation and particle irradiation on 2H MoS 2 two-dimensional nanolayers are reviewed in this paper, covering heavy ions, protons, electrons, gamma rays, X-rays, ultraviolet light, terahertz, and infrared irradiation. Various defects in MoS 2 layers were created by the defect engineering. Here we focus on their influence on the structural, electronic, catalytic, and magnetic performance of the 2D materials. Additionally, irradiation-induced doping is discussed and involved.

Density functional theory simulation of cobalt oxide aggregation and facile synthesis of a cobalt oxide, gold and multiwalled carbon nanotube based ternary composite for a high performance supercapattery

A novel ternary composite consisting of cobalt oxide (Co₃O₄) nanoparticles (NPs) grown on multiwalled carbon nanotubes (MWCNTs) and mixed with gold (Au) NPs is synthesized by a single step hydrothermal route.

Unveiling the Effect of the Structure of Carbon Material on the Charge Storage Mechanism in MoS2-Based Supercapacitors

MoS₂ is a 2D material that has been widely used in supercapacitor applications because of its layered structure that provides a large surface area and allows for high electric double-layer charge storage. To enhance the cycling stability and capacitance of MoS₂, it is usually mixed with carbon materials. However, the dependence of the charge storage mechanism on the structure of the carbon material is still unclear in literature. Herein, the effect of the structure of the carbon material on the charge storage mechanism in 2H flower-shaped MoS₂ is investigated in detail. Specifically, 2H MoS₂ was mixed with either 8 nm-diameter carbon nanotubes (CNTs) or graphene nanoflakes (GNFs) in different weight ratios. Also, a composite of MoS₂, CNTs, and GNFs (1:1:1) was also studied. The charge storage mechanism was found to depend on the structure and content of the carbon material. Insights into the possible storage mechanism(s) were discussed. The MoS₂/CNT/GNF composite showed a predominant pseudocapacitive charge storage mechanism where the diffusion current was ∼89%, with 88.31% of the resulted capacitance being due to faradic processes.

Hierarchical NiCo2S4@NiCoP core-shell nanocolumn arrays on nickel foam as a binder-free supercapacitor electrode with enhanced electrochemical performance

A novel hierarchical core-shell nanocolumn array, with NiCo₂S₄ hollow nanowire (NiCo₂S₄ H-NW) as the core and NiCoP nanosheet (NiCoP NS) as the shell, has been directly synthesized on nickel foam (NF) as self-supported, binder-free electrode for high-performance supercapacitors. The morphological characterizations reveal that the diameter of NiCo₂S₄ H-NW core is ∼100 nm and the diameter of single NiCo₂S₄@NiCoP core-shell nanocolumn is ∼250 nm. Through a series of electrochemical tests and the analysis of charge storage kinetics, hierarchical NiCo₂S₄@NiCoP/NF electrode presents high areal specific capacitance of 5.98 F/cm² at 1 mA/cm², outstanding rate capability (70.29% capacitance retention with the current density increased from 1 to 50 mA/cm²) and superior cycling stability (92.94% of original capacity is retained after 5000 cycles at 10 mA/cm²). The prominent performance of NiCo₂S₄@NiCoP/NF electrode could be resulted from their unique hierarchical core-shell nanocolumn structure, which could offer abundant active sites near the interface for fast electrochemical reaction, and validly avoid the collapse of internal structure for the stability of whole structure in the repeated electrochemical measurement. The novel NiCo₂S₄@NiCoP/NF electrode offers a new method for future electrochemical energy storage devices with high-stability.