Approaching the Lithiation Limit of MoS2 While Maintaining Its Layered Crystalline Structure to Improve Lithium Storage

Reconstructable Carbon Monolayer-MoS2 Intercalated Heterostructure Enabled by Atomic Layers-Confined Topotactic Transformation for Ultrafast Lithium Storage

The intercalation structure of two-dimensional materials with expanded interlayer distance can facilitate mass transport, which is promising in fast-charging lithium-ion batteries (LIBs). However, the designed intercalation structures will be pulverized and destroyed under tough working conditions, causing overall performance deterioration of the batteries. Here, we present that an intercalated heterostructure made of the typical layered material of MoS2 intercalated by N-doped graphene-like carbon monolayer (MoS2/g-CM) through a polymer intercalation strategy exhibits a unique behavior of reversible reconstructability as an LIB anode during cycling. A mechanism of "carbon monolayers-confined topotactic transformation" is proposed, which is evidenced by substantial in/ex situ characterizations. The intercalated heterostructure of MoS2/g-CM featuring a reconstructable property and efficient interlayer electron/ion transport exhibits an unprecedented rate capability up to 50 A g-1 and outstanding long cyclability. Moreover, the proposed strategy based on g-CM intercalation has been extended to the MoSe2 system, also realizing reconstructability of the intercalated heterostructure and improved LIB performance, demonstrating its versatility and great potential in applications.

Hygroscopic Solutes Enable Non-van der Waals Electrolytes for Fire-Tolerant Dual-Air Batteries

Thermal safety issues of batteries have hindered their large-scale applications. Nonflammable electrolytes improved safety but solvent evaporation above 100 °C limited thermal tolerance, lacking reliability. Herein, fire-tolerant metal-air batteries were realized by introducing solute-in-air electrolytes whose hygroscopic solutes could spontaneously reabsorb the evaporated water solvent. Using Zn/CaCl2 -in-air/carbon batteries as a proof-of-concept, they failed upon burning at 631.8 °C but self-recovered then by reabsorbing water from the air at room temperature. Different from conventional aqueous electrolytes whose irreversible thermal transformation is determined by the boiling points of solvents, solute-in-air electrolytes make this transformation determined by the much higher decomposition temperature of solutes. It was found that stronger intramolecular bonds instead of intermolecular (van der Waals) interactions were strongly correlated to ultra-high tolerance temperatures of our solute-in-air electrolytes, inspiring a concept of non-van der Waals electrolytes. Our study would improve the understanding of the thermal properties of electrolytes, guide the design of solute-in-air electrolytes, and enhance battery safety.

Molybdenum disulfide (MoS2) along with graphene nanoplatelets (GNPs) utilized to enhance the capacitance of conducting polymers (PANI and PPy)

Hybrid composites of molybdenum disulfide (MoS2), graphene nanoplatelets (GNPs) and polyaniline (PANI)/polypyrrole (PPy) have been synthesized as cost-effective electrode materials for supercapacitors. We have produced MoS2 from molybdenum dithiocarbamate by a melt method in an inert environment and then used a liquid exfoliation method to form its composite with graphene nanoplatelets (GNPs) and polymers (PANI and PPy). The MoS2 melt/GNP ratio in the resultant composites was 1 : 3 and the polymer was 10% by wt. of the original composite. XRD (X-ray diffraction analysis) confirmed the formation of MoS2 and SEM (scanning electron microscopy) revealed the morphology of the synthesized materials. The electrochemical charge storage performance of the synthesized composite materials was assessed by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge (GCCD) measurements. Resultant composites showed enhanced electrochemical performances (specific capacitance = 236.23 F g-1, energy density = 64.31 W h kg-1 and power density = 3858.42 W kg-1 for MoS2 melt 5 mPP at a current density of 0.57 A g-1 and had 91.87% capacitance retention after 10 000 charge-discharge cycles) as compared to the produced MoS2; thus, they can be utilized as electrode materials for supercapacitors.

Ex Situ Characterization of 1T/2H MoS2 and Their Carbon Composites for Energy Applications, a Review

The growing interest in the development of next-generation net zero energy systems has led to the expansion of molybdenum disulfide (MoS₂) research in this area. This activity has resulted in a wide range of manufacturing/synthesis methods, controllable morphologies, diverse carbonaceous composite structures, a multitude of applicable characterization techniques, and multiple energy applications for MoS₂. To assess the literature trends, 37,347 MoS₂ research articles from Web of Science were text scanned to classify articles according to energy application research and characterization techniques employed. Within the review, characterization techniques are grouped under the following categories: morphology, crystal structure, composition, and chemistry. The most common characterization techniques identified through text scanning are recommended as the base fingerprint for MoS₂ samples. These include: scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Similarly, XPS and Raman spectroscopy are suggested for 2H or 1T MoS₂ phase confirmation. We provide guidance on the collection and presentation of MoS₂ characterization data. This includes how to effectively combine multiple characterization techniques, considering the sample area probed by each technique and their statistical significance, and the benefit of using reference samples. For ease of access for future experimental comparison, key numeric MoS₂ characterization values are tabulated and major literature discrepancies or currently debated characterization disputes are highlighted.

An interlayer spacing design approach for efficient sodium ion storage in N-doped MoS2

MoS₂ in a graphene-like structure that possesses a large interlayer spacing is a promising anode material for sodium ion batteries (SIBs). However, its poor cycling stability and bad rate performance limit its wide application. In this work, we synthesized an N-doped rGO/MoS₂ (ISE, interlayer spacing enlarged) composite based on an innovative strategy to serve as an anode material for SIBs. By inserting NH₄⁺ into the interlayer of MoS₂, the interlayer spacing of MoS₂ was successfully expanded to 0.98 nm. Further use of N plasma treatment achieved the doping of N element. The results show that N-rGO/MoS₂(ISE) exhibits a high specific capacity of 542 mA h g^-1 after 300 cycles at 200 mA g^-1. It is worth mentioning that the capacity retention rate reaches an ultra-large percentage of 97.13%, and the average decline percentage per cycle is close to 0.01%. Moreover, it also presents an excellent rate performance (477, 432, 377, 334 mA h g^-1 at 200, 500, 1000, 2000 m A g^-1 respectively). This work reveals a unique approach to fabricating promising anode materials and the electrochemical reaction mechanism for SIBs.

Spreading the Landscape of Dual Ion Batteries: from Electrode to Electrolyte

The working mechanism of a dual-ion battery (DIB) differs from that of a lithium-ion battery (LIB) in that the anions in the electrolyte of the former can be intercalated as well. Researchers have been paying close attention to this device because of its high voltage, low price, and environmental friendliness. However, DIBs are still in their early research stages, and numerous issues need to be addressed and investigated further. Initially, this Review explains how DIBs work in principle and discusses the progress of electrode materials for cathode and anode. Furthermore, since the electrolytes used as the active material, as well as anion, solvent, and additives, have a significant impact on the DIB's capacity and voltage, the current status is also presented in terms of electrolytes, followed by an outlook on confronting the challenges. A comprehensive summary from electrode to electrolyte will guide the development of next-generation DIBs.

Tunable 0D/2D/2D Nanocomposite Based on Green Zn-Doped CuInS2 Quantum Dots and MoS2/rGO as Photoelectrodes for Solar Hydrogen Production

Charge separation, transmission, and light absorption properties are critical to determining the performance of photoelectrochemical (PEC) devices. An important strategy to control such properties is based on using heterostructured materials. Herein, a tunable zero-dimensional (0D)/two-dimensional (2D) heterostructure is designed based on quantum dots (QDs) and 2D nanosheets (NSs). Specifically, eco-friendly Zn-doped CuInS₂ QDs prepared by hot injection were anchored on hierarchical (2D/2D) MoS₂/rGO (MG) NSs through a facile sonication-assisted method to develop a 0D/2D/2D heterojunction-based photoelectrode for solar hydrogen production. The interfacial structure and band alignment between the proposed 0D QDs and 2D/2D MG NSs were engineered by modulating the Zn molar ratio during the QD synthesis. As proof of concept, the optimized 0D/2D/2D photoanode exhibits almost five times higher PEC activity than MG/CuInS₂ and MoS₂/Zn-CuInS₂ NSs due to the enhanced light absorption, efficient charge separation, and transmission. Zn doping and the presence of graphene are essential in enhancing performance in the proposed heterostructure, reducing recombination of charge carriers, and improving sunlight absorption. This work shows how optimal band alignment control and carbon addition can facilitate charge transfer, enabling the development of highly efficient PEC devices based on 0D/2D/2D heterostructure nanocomposites.

Strongly Coupled MoS2 Nanocrystal/Ti3 C2 Nanosheet Hybrids Enable High-Capacity Lithium-Ion Storage

Smart integration of transition-metal sulfides/oxides/nitrides with the conductive MXene to form hybrid materials is very promising in the development of high-performance anodes for next-generation Li-ion batteries (LIBs) owing to their advantages of high specific capacity, favorable Li⁺ intercalation structure, and superior conductivity. Herein, a facile route was proposed to prepare strongly coupled MoS₂ nanocrystal/Ti₃ C₂ nanosheet hybrids through freeze-drying combined with a subsequent thermal process. The Ti₃ C₂ host could enhance the reaction kinetics and buffer the volume change of MoS₂ at a low content (8.87 wt %). Thus, the MoS₂ /Ti₃ C₂ hybrids could deliver high rate performance and excellent cycling durability. As such, high reversible capacities of 835.1 and 706.0 mAh g^-1 could be maintained after 110 cycles at 0.5 A g^-1 and 1390 cycles at 5 A g^-1 , respectively, as well as an outstanding rate capability with a capacity retention over 65.8 % at 5 A g^-1 . This synthetic strategy could be easily extended to synthesize other high-performance MXene-supported hybrid electrode materials.

How does Molybdenum Disulfide Store Charge: A Minireview

MoS₂ has attracted tremendous attention as a promising electrode material for rechargeable alkali metal ion (Li⁺ , Na⁺ , K⁺ ) batteries due to its high capacity and low cost. However, the practical application of MoS₂ for energy storage has not been achieved yet, which is restricted by its intrinsic charge-storage behavior. Debates still exist in this field although great efforts have been made to reveal alkali metal ion (Li⁺ , Na⁺ , K⁺ ) storage mechanism of MoS₂ . This Minireview aims to provide an analysis and summary of the related phase conversion, structure collapse, and loss of active material in a MoS₂ electrode during the intercalation/extraction process of alkali metal ions. Hence, the fundamental understanding about the charge storage in MoS₂ is of importance for the rational design of MoS₂ electrodes with excellent electrochemical performance.

Hierarchical Composite of Rose-Like VS2 @S/N-Doped Carbon with Expanded (001) Planes for Superior Li-Ion Storage

In the present work, a hierarchical composite of rose-like VS₂ @S/N-doped carbon (VS₂ @SNC) with expanded (001) planes is successfully fabricated through a facile synthetic route. Notably, the d-spacing of (001) planes is expanded to 0.92 nm, which is proved to dramatically reduce the energy barrier for Li⁺ diffusion in the composite of VS₂ @SNC by density functional theory calculation. On the other hand, the S/N-doped carbon in the composite greatly promotes the electrical conductivity and enhances the structural stability. In addition, the hierarchical structure of VS₂ @SNC facilitates rapid electrolyte diffusion and increases the contact area between the electrode and electrolyte simultaneously. Benefiting from the merits mentioned above, the VS₂ @SNC electrode exhibits excellent electrochemical properties, such as a large reversible capacity of 971.6 mA h g^-1 at 0.2 A g^-1 , an extremely high rate capability of 772.1 mA h g^-1 at 10 A g^-1 , and a remarkable cycling stability up to 600 cycles at 8 A g^-1 with a capacity of 684.5 mA h g^-1 , making it a promising candidate as an anode material for lithium-ion batteries.