Two-Dimensional Transition Metal Chalcogenides for Alkali Metal Ions Storage

Addressing Irreversibility and Structural Distortion in WS2 Inorganic Fullerene-Like Nanoparticles: Effects of Voltage Cutoff Experiments in Beyond Li+-Ion Storage Applications

Large interlayer spacing beneficially allows Na+- and K+-ion storage in transition-metal dichalcogenide (TMD)-based electrodes, but side reactions and volume change, which pulverize the TMD crystalline structure, are persistent challenges for the utilization of these materials in next-generation devices. This study first determines whether irreversibility due to structural distortion, which results in poor cycling stability, is also apparent in the case of inorganic fullerene-like (IF) tungsten disulfide (WS2) nanocages (WS2IF). To address these problems, this study proposes upper and lower voltage cutoff experiments to limit specific reactions in Na+/WS2IF and K+/WS2IF half-cells. Three-dimensional (3D) differential capacity curves and derived surface plots highlight the continuation of reversible reactions when a high upper cutoff technique is applied, thereby indirectly suggesting restricted structural dissolution. This resulted in improved capacity retention with stable performance and a higher Coulombic efficiency, laying the ground for the use of TMD-based materials beyond Li+-ion storage devices.

Carbon-supported T-Nb2O5 nanospheres and MoS2 composites with a mosaic structure for insertion-conversion anode materials

Reasonably combining the strengths of insertion and conversion anode materials to create an advanced anode material remains a formidable challenge for rechargeable lithium-ion batteries (LIBs). In this work, bulk MoS2 embedded with T-Nb2O5 nanospheres was synthesized via a simple hydrothermal process and a polydopamine carbon source was introduced by heat treatment. The design strategy can effectively accelerate the charge transfer and reduce the volume expansion during electrochemical cycling, leading to an improvement in lithium storage performance. As a consequence, the coexistence of T-Nb2O5, MoS2 and C can achieve the best synergistic effect when the molar ratio of Nb and Mo sources was 1 : 1. Notably, the T-Nb2O5@MoS2@C-1-1 electrode not only delivered an excellent reversible capacity of 518 mA h g-1 at a current density of 0.1 A g-1 but also exhibited superb cycling stability. The specific capacity of this electrode maintained 187 mA h g-1 at 2 A g-1 after 1000 cycles with a negligible capacity fading rate of only 0.015% per cycle.

Design principles for 2D transition metal dichalcogenides toward lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are regarded as a promising candidate for next-generation energy storage systems owing to their remarkable energy density, resource availability, and environmental benignity. Nevertheless, severe shuttling effect, sluggish redox kinetics, large volumetric expansion, and uncontrollable dendrite growth hamper the practical applications. To address these intractable issues, two-dimensional (2D) transition metal dichalcogenides (TMDs) have emerged expeditiously as an essential material strategy. Herein, this review emphasizes the development and application of 2D TMDs in Li-S batteries. It starts with introducing the fundamentals of Li-S batteries and common synthetic routes of TMDs, followed by summarizing the employment of pristine, hybrid, and defective TMDs in the realm of expediting sulfur chemistry and stabilizing lithium anode. Finally, the development roadmap and possible research directions of TMDs are proposed to offer guidance for the future design of high-performance Li-S batteries.

Double-Walled NiTeSe-NiSe2 Nanotubes Anode for Stable and High-Rate Sodium-Ion Batteries

Electrodes made of composites with heterogeneous structure hold great potential for boosting ionic and charge transfer and accelerating electrochemical reaction kinetics. Herein, hierarchical and porous double-walled NiTeSe-NiSe₂ nanotubes are synthesized by a hydrothermal process assisted in situ selenization. Impressively, the nanotubes have abundant pores and multiple active sites, which shorten the ion diffusion length, decrease Na⁺ diffusion barriers, and increase the capacitance contribution ratio of the material at a high rate. Consequently, the anode shows a satisfactory initial capacity (582.5 mA h g^-1 at 0.5 A g^-1 ), a high-rate capability, and long cycling stability (1400 cycles, 398.6 mAh g^-1 at 10 A g^-1 , 90.5% capacity retention). Moreover, the sodiation process of NiTeSe-NiSe₂ double-walled nanotubes and underlying mechanism of the enhanced performance are revealed by in situ and ex situ transmission electron microscopy and theoretical calculations.

Scanning Electrochemical Microscopy for Chemical Imaging and Understanding Redox Activities of Battery Materials

Improving the charge storage capacity and lifetime and charging/discharging efficiency of battery systems is essential for large-scale applications such as long-term grid storage and long-range automobiles. While there have been substantial improvements over the past decades, further fundamental research would help provide insights into improving the cost effectiveness of such systems. For example, it is critical to understand the redox activities of cathode and anode electrode materials and stability and the formation mechanism and roles of the solid-electrolyte interface (SEI) that forms at the electrode surface upon an external potential bias. The SEI plays a critical role in preventing electrolyte decay while still allowing charges to flow through the system while serving as a charge transfer barrier. While surface analytical techniques such as X-ray photoelectron (XPS), X-ray diffraction (XRD), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and atomic force microscopy (AFM) provide invaluable information on anode chemical composition, crystalline structure, and morphology, they are often performed ex situ, which can induce changes to the SEI layer after it is removed from the electrolyte. While there have been efforts to combine these techniques using pseudo-in situ approaches via vacuum-compatible devices and inert atmosphere chambers connected to glove boxes, there is still a need for true in situ techniques to obtain results with improved accuracy and precision. Scanning electrochemical microscopy (SECM) is an in situ scanning probe technique that can be combined with optical spectroscopy techniques such as Raman and photoluminescence spectroscopy methods to gain insights into the electronic changes of a material as a function of applied bias. This Review will highlight the potential of SECM and recent reports on combining spectroscopic measurements with SECM to gain insights into the SEI layer formation and redox activities of other battery electrode materials. These insights provide invaluable information for improving the performance of charge storage devices.

Metal-Organic Assembly Strategy for the Synthesis of Layered Metal Chalcogenide Anodes for Na+ /K+ -Ion Batteries

Layered transition metal chalcogenides (MX, M=Mo, W, Sn, V; X=S, Se, Te) have large ion transport channels and high specific capacity, making them promising for large-sized Na⁺ /K⁺ energy-storage technologies. Nevertheless, slow reaction kinetics and huge volume expansion will induce an undesirable electrochemical performance. Numerous efforts have been devoted to designing MX anodes and enhancing their electrochemical performance. Based on the metal-organic assembly strategy, nanostructural engineering, combination with carbon materials, and component regulation can be easily realized, which effectively boost the performance of MX anodes. In this Review, we present a comprehensive overview on the synthesis of MX nanostructure using the metal-organic assembly strategy, which can realize the design of MX nanostructures, based on self-sacrificial templates, host@guest tailored templates, post-modified layer and derivative templates. The preparation routes and structure evolution are mainly discussed. Then, Mo-, W-, Sn-, V-based chalcogenides used for Na⁺ /K⁺ energy storage are reviewed, and the relationship between the structure and the electrochemical performance, as well as the energy storage mechanism are emphasized. In addition, existing challenges and future perspectives are also presented.

Transition metal chalcogenides for next-generation energy storage

Transition-metal chalcogenide nanostructures provide a unique material platform to engineer next-generation energy storage devices such as lithium-ion, sodium-ion, and potassium-ion batteries and flexible supercapacitors. The transition-metal chalcogenide nanocrystals and thin films have enhanced electroactive sites for redox reactions and hierarchical flexibility of structure and electronic properties in the multinary compositions. They also consist of more earth-abundant elements. These properties make them attractive and more viable new electrode materials for energy storage devices compared to the traditional materials. This review highlights the recent advances in chalcogenide-based electrodes for batteries and flexible supercapacitors. The viability and structure-property relation of these materials are explored. The use of various chalcogenide nanocrystals supported on carbonaceous substrates, two-dimensional transition metal chalcogenides, and novel MXene-based chalcogenide heterostructures as electrode materials to improve the electrochemical performance of lithium-ion batteries is discussed. The sodium-ion and potassium-ion batteries offer a more viable alternative to lithium-ion technology as they consist of readily available source materials. Application of various transition metal chalcogenides such as MoS2, MoSe2, VS2, and SnSx, composite materials, and heterojunction bimetallic nanosheets composed of multi-metals as electrodes to enhance the long-term cycling stability, rate capability, and structural strength to counteract the large volume expansion during the ion intercalation/deintercalation processes is highlighted. The promising performances of layered chalcogenides and various chalcogenide nanowire compositions as electrodes for flexible supercapacitors are also discussed in detail. The review also details the progress made in new chalcogenide nanostructures and layered mesostructures for energy storage applications.

Comprehensively Understanding the Role of Anion Vacancies on K-Ion Storage: A Case Study of Se-Vacancy-Engineered VSe2

Anion vacancy engineering (AVE) is widely used to improve the Li-ion and Na-ion storage of conversion-type anode materials. However, AVE is still an emerging strategy in K-ion batteries, which are promising for large-scale energy storage. In addition, the role of anion vacancies on ion storage is far from clear, despite several proposed explanations. Herein, by employing VSe₂ as a model conversion-type anode material, Se vacancies are intentionally introduced (labeled as P-VSe_2-x ) to investigate their effect on K⁺ storage. The P-VSe_2-x shows excellent cyclability in half cells (143 mA h g^-1 at 3.0 A g^-1 after 1000 cycles) and high energy density in coin-type full cells (206.8 Wh kg^-1 ). By applying various electrochemical techniques, the effects of Se vacancies on the redox potentials of K-ion insertion/extraction and the K-ion diffusion in electrodes upon cycling are uncovered. In addition, the structural evolution of Se vacancies during potassiation/de-potassiation using various operando and ex characterizations is revealed. Moreover, it is demonstrated that Se vacancies can facilitate the breaking of VSe bonds upon the P-VSe_2-x conversion using theoretical calculations. This work comprehensively explains the role of anion vacancies in ion storage for developing high-performance conversion-type anode materials.

Fundamental Properties of Hydrogen-Functionalized GaSe Monolayer

Functionalization reveals potential opportunities for modifying essential properties and designing materials due to the strong interaction between functionalized atoms and the surface. Among them, hydrogenation possesses such a way to control electronic and optical characteristics. In this paper, the stability and transformed electronic, optical properties of H-functionalized GaSe in two cases (single and double sites) were reported that exhibit the effects of hydrogen functionalization via first-principles calculations. Formation energies suggest that H-functionalized GaSe systems are stable for construction. H-GaSe and 2H-GaSe display distinct properties based on the functionalized way (single- or double-site functionalization). Accordingly, H-GaSe is metallic, while 2H-GaSe belongs to a semiconductor. The magnetic configuration with ferro- and anti-ferromagnetic could be found in H- and 2H-functionalized cases through spin distribution, respectively. Especially, the chemical hybridized bonds of Se-H, Ga-Se, and Ga-Ga corresponding to s-sp³ and sp³-sp³ bondings, respectively, are clearly verified in the orbital-projected density of states and charge density. The optical properties of 2H-GaSe could provide the main characteristics of a semiconductor, which is the limited range of transparency by electronic absorption at short and long wavelengths. Moreover, increasing the number of GaSe segments (L) could change the band gap leading to application in the band gap engineering of the 2H-GaSe systems. Thus, hydrogen functionalization could provide the possible manner for adjusting and controlling features of GaSe, promising for the development of electronic devices and applications.

Insight on Cathodes Chemistry for Aqueous Zinc-Ion Batteries: From Reaction Mechanisms, Structural Engineering, and Modification Strategies

By virtue of low cost, eco-friendliness, competitive gravimetric energy density, and intrinsic safety, more and more attention has increasingly focused on aqueous zinc ion batteries (AZIBs) as a promising alternative for scalable energy storage. However, plagued by a complex interfacial process, sluggish dynamics, lability of electrodes and electrolytes, insufficient energy density, and poor cycle life heavily restrict practical applications of AZIBs, indicating that profound understandings on cathode storage chemistry are necessarily needed. Hence, this paper comprehensively summarizes recent advance in cathodes with critical insight on the energy storage mechanism. Furthermore, the issues and challenges for high-performance cathodes are meticulously explored, presenting inspiring structural engineering and modification strategies. Finally, rational evaluations on representative cathodes are rendered, suggesting the potential development direction of AZIBs.

Graphene-Supported Atomically Dispersed Metals as Bifunctional Catalysts for Next-Generation Batteries Based on Conversion Reactions

Next-generation batteries based on conversion reactions, including aqueous metal-air batteries, nonaqueous alkali metal-O₂ and -CO₂ batteries, alkali metal-chalcogen batteries, and alkali metal-ion batteries have attracted great interest. However, their use is restricted by inefficient reversible conversion of active agents. Developing bifunctional catalysts to accelerate the conversion reaction kinetics in both discharge and charge processes is urgently needed. Graphene-, or graphene-like carbon-supported atomically dispersed metal catalysts (G-ADMCs) have been demonstrated to show excellent activity in various electrocatalytic reactions, making them promising candidates. Different from G-ADMCs for catalysis, which only require high activity in one direction, G-ADMCs for rechargeable batteries should provide high activity in both discharging and charging. This review provides guidance for the design and fabrication of bifunctional G-ADMCs for next-generation rechargeable batteries based on conversion reactions. The key challenges that prevent their reversible conversion, the origin of the activity of bifunctional G-ADMCs, and the current design principles of bifunctional G-ADMCs for highly reversible conversion, have been analyzed and highlighted for each conversion-type battery. Finally, a summary and outlook on the development of bifunctional G-ADMC materials for next-generation batteries with a high energy density and excellent energy efficiency are given.

Anionic Redox Regulated via Metal-Ligand Combinations in Layered Sulfides

The increasing demand for energy storage is calling for improvements in cathode performance. In traditional layered cathodes, the higher energy of the metal 3d over the O 2p orbital results in one-band cationic redox; capacity solely from cations cannot meet the needs for higher energy density. Emerging anionic redox chemistry is promising to access higher capacity. In recent studies, the low-lying O nonbonding 2p orbital was designed to activate one-band oxygen redox, but they are still accompanied by reversibility problems like oxygen loss, irreversible cation migration, and voltage decay. Herein, by regulating the metal-ligand energy level, both extra capacities provided by anionic redox and highly reversible anionic redox process are realized in NaCr_{1- y} V_y S₂ system. The simultaneous cationic and anionic redox of Cr/V and S is observed by in situ X-ray absorption near edge structure (XANES). Under high d-p hybridization, the strong covalent interaction stabilizes the holes on the anions, prevents irreversible dimerization and cation migration, and restrains voltage hysteresis and voltage decay. The work provides a fundamental understanding of highly reversible anionic redox in layered compounds, and demonstrates the feasibility of anionic redox chemistry based on hybridized bands with d-p covalence.

Growth Mechanism of Micro/Nano Metal Dendrites and Cumulative Strategies for Countering Its Impacts in Metal Ion Batteries: A Review

Metal-ion batteries are capable of delivering high energy density with a longer lifespan. However, they are subject to several issues limiting their utilization. One critical impediment is the budding and extension of solid protuberances on the anodic surface, which hinders the cell functionalities. These protuberances expand continuously during the cyclic processes, extending through the separator sheath and leading to electrical shorting. The progression of a protrusion relies on a number of in situ and ex situ factors that can be evaluated theoretically through modeling or via laboratory experimentation. However, it is essential to identify the dynamics and mechanism of protrusion outgrowth. This review article explores recent advances in alleviating metal dendrites in battery systems, specifically alkali metals. In detail, we address the challenges associated with battery breakdown, including the underlying mechanism of dendrite generation and swelling. We discuss the feasible solutions to mitigate the dendrites, as well as their pros and cons, highlighting future research directions. It is of great importance to analyze dendrite suppression within a pragmatic framework with synergy in order to discover a unique solution to ensure the viability of present (Li) and future-generation batteries (Na and K) for commercial use.

MXene and MoS3- x Coated 3D-Printed Hybrid Electrode for Solid-State Asymmetric Supercapacitor

Recently, 2D nanomaterials such as transition metal carbides or nitrides (MXenes) and transition metal dichalcogenides (TMDs) have attracted ample attention in the field of energy storage devices specifically in supercapacitors (SCs) because of their high metallic conductivity, wide interlayer spacing, large surface area, and 2D layered structures. However, the low potential window (ΔV ≈ 0.6 V) of MXene e.g., Ti₃ C₂ T_x limits the energy density of the SCs. Herein, asymmetric supercapacitors (ASCs) are fabricated by assembling the exfoliated Ti₃ C₂ T_x (Ex-Ti₃ C₂ T_x ) as the negative electrode and transition metal chalcogenide (MoS_{3- x} ) coated 3D-printed nanocarbon framework (MoS_{3- x} @3DnCF) as the positive electrode utilizing polyvinyl alcohol (PVA)/H₂ SO₄ gel electrolyte, which provides a wide ΔV of 1.6 V. The Ex-Ti₃ C₂ T_x possesses wrinkled sheets which prevent the restacking of Ti₃ C₂ T_x 2D layers. The MoS_{3- x} @3DnCF holds a porous structure and offers diffusion-controlled intercalated pseudocapacitance that enhances the overall capacitance. The 3D printing allows a facile fabrication of customized shaped MoS_{3- x} @3DnCF electrodes. Employing the advantages of the 3D-printing facilities, two different ASCs, such as sandwich- and interdigitated-configurations are fabricated. The customized ASCs provide excellent capacitive performance. Such ASCs combining the MXene and electroactive 3D-printed nanocarbon framework can be used as potential energy storage devices in modern electronics.

A Partial Sulfuration Strategy Derived Multi-Yolk-Shell Structure for Ultra-Stable K/Na/Li-ion Storage

Metal sulfides are attractive anodes for alkali metal ion batteries due to the high theoretical capacity, while their practical implementation is hampered by the inherent poor conductivity and vast volume variation during cycles. Approaching rational designed microstructures with good stability and fast charge transfer is of great importance in response to these issues. Herein, a partial sulfuration strategy for the rational construction of multi-yolk-shell (m-Y-S) structures, from which multiple Fe_{1- x} S nanoparticles are confined within hollow carbon nanosheet with tunable interior void space is reported. As anode materials, the m-Y-S Fe_{1- x} S@C composite can display high capacity and excellent rate capability (134, 365, and 447 mA h g^-1 for K⁺ , Na⁺ , and Li⁺ storage at 20 A g^-1 ). Remarkably, it exhibits ultra-stable potassium storage up to 1200, 6000, and 20 000 cycles under current densities of 0.1, 0.5, and 1 A g^-1 , which is much superior to previous yolk-shell structures and metal-sulfide anodes. Based on comprehensive experimental analysis and theoretical calculations, the exceptional performance of m-Y-S structure can be ascribed to the optimized interior void space for good structure stability, as well as the multiple connection points and conductive carbon layer for superior electron/ion transportation.

Designing Nanostructured Metal Chalcogenides as Cathode Materials for Rechargeable Magnesium Batteries

Rechargeable magnesium batteries (RMBs) are regarded as promising candidates for beyond-lithium-ion batteries owing to their high energy density. Moreover, as Mg metal is earth-abundant and has low propensity for dendritic growth, RMBs have the advantages of being more affordable and safer than the currently used lithium-ion batteries. However, the commercial viability of RMBs has been negatively impacted by slow diffusion kinetics in most cathode materials due to the high charge density and strongly polarizing nature of the Mg²⁺ ion. Nanostructuring of potential cathode materials such as metal chalcogenides offers an effective means of addressing these challenges by providing larger surface area and shorter migration routes. In this article, a review of recent research on the design of metal chalcogenide nanostructures for RMBs' cathode materials is provided. The different types and structures of metal chalcogenide cathodes are discussed, and the synthetic strategies through which nanostructuring of these materials can be achieved are described. An organized summary of their electrochemical performance is also presented, along with an analysis of the current challenges and future directions. Although particular focus is placed on RMBs, many of the nanostructuring concepts that are discussed here can be carried forward to other next-generation energy storage systems.

HPO42- enhanced catalytic activity of N, S, B, and O-codoped carbon nanosphere-armored Co9S8 nanoparticles for organic pollutants degradation via peroxymonosulfate activation: critical roles of superoxide radical, singlet oxygen and electron transfer

In this study, we report a facile synthesis of a novel N, S, B, and O-codoped carbon nanosphere-armored Co9S8 nanoparticle composite (Co9S8@NSBOC) and its superior activation performance toward peroxymonosulfate (PMS) for methylene blue (MB) and ofloxacin degradation. The effects of various experimental parameters and the general applicability of the catalyst were investigated. Particularly, Co9S8@NSBOC exhibited high catalytic activity in a wide pH range of 3-12 and HPO42- exhibited a synergic catalytic effect with Co9S8@NSBOC in the degradation system. Radical quenching tests, EPR measurements and electrochemical analysis demonstrated that the degradation mechanism of pollutants in the Co9S8@NSBOC/PMS system included both radical and non-radical pathways, in which ˙O2-, 1O2 and electron transfer played dominant roles. Co2+, S2-, carbon defects, C[double bond, length as m-dash]O/C-O-C, pyridinic-N, graphitic-N, BC2O and C-S-C species on Co9S8@NSBOC, all contributed to PMS activation. The degradation pathways of MB and ofloxacin were proposed based on HPLC-MS/MS analysis of their degradation intermediates. This work not only presents a facile and practical synthetic method of cobalt sulfide-coupled multi-heteroatom-doped carbocatalysts, but also provides useful insights into their active sites and activation mechanisms toward PMS activation.

Unraveling MoS2 and Transition Metal Dichalcogenides as Functional Zinc-Ion Battery Cathode: A Perspective

The zinc-ion battery (ZIB) is considered as one of the most important alternative battery chemistries to date. However, one of the challenges in ZIB development is the limited selection of materials that can exhibit satisfactory Zn²⁺  storage. Transition metal dichalcogenides (TMDs) are widely investigated in energy-related applications due to their distinct physical and chemical properties. In particular, the wide interlayer spacings for these TMDs are particularly attractive as viable Zn²⁺  storage sites. Despite the suitability of TMDs in ZIB application, they are still not widely explored due to their limited report in this area. In this perspective review, the key challenge of TMDs, especially for MoS₂ , in their utilization as ZIB cathode are discussed. The various reports on MoS₂  and TMDs as ZIB cathodes are also summarized. In order to elicit reasonable Zn²⁺  storage ability in MoS₂  and TMDs, four key modification strategies are proposed: 1) interlayer engineering, 2) defect engineering, 3) hybridization, and 4) phase engineering. These proposed modification strategies may be able to address the challenge of inadequate Zn²⁺  storage in MoS₂  and TMDs. Finally, this review ends with a conclusion and outlook of MoS₂  and TMDs in the future development of ZIB cathodes.

Solvothermal synthesis of carbonate-type layered double hydroxide monolayer nanosheets: Solvent selection based on characteristic parameter matching criterion

Monolayer nanosheets of CO₃^2--type layered double hydroxides (LDHs) have many special applications, but their fabrication is challenging. Herein, Co₂Al-CO₃ and Co₂Fe-CO₃ LDH nanosheets were synthesized via a solvothermal method. 31 solvents with different characteristic parameters, including the surface free energy (γ) and solubility (δ) parameters were chosen, to explore the correlation between the formation of monolayer LDHs (ML-LDHs) and the characteristic parameters of solvents. The results reveal that when the solvents used have the characteristic parameters matching to those of the LDHs, CO₃^2--type ML-LDHs with a thickness of ca. 1 nm can be obtained. The mixed-solvent strategy can provide the effective solvents for the synthesis of ML-LDHs. The dispersions of CO₃^2--type ML-LDHs can be stable for at least six months without obvious precipitation. In addition, it is demonstrated that the δ parameters of LDHs can be calculated from the γ parameters via the molar volume-free γ-δ equations developed previously. Furthermore, a new parameter called "surface free energy distance" is introduced, which can be used for screening effective solvents for the synthesis of ML-LDHs. To the best of our knowledge, this is the first time to investigate the applicable of the characteristic parameter matching principle for the bottom-up synthesis of ML-LDHs. This work deepens the understanding on the feature of CO₃^2--type LDHs and provides a solvent selection strategy for the synthesis of CO₃^2--type ML-LDHs.

Emerging Potassium-ion Hybrid Capacitors

As a new type of capacitor-battery hybrid energy storage device, metal-ion capacitors have attracted widespread attention because of their high-power density while ensuring energy density and long lifespan. Potassium-ion capacitors (KICs) featuring the merits of abundant potassium resources, lower standard electrode potential, and low cost have been considered as potential alternatives to lithium-/sodium-ion capacitors. However, KICs still face issues including unsatisfactory reaction kinetics, low energy density, and poor lifetime owing to the large radius of the potassium ion. In this Review, the importance of emerging potassium-ion capacitor is addressed. The Review offers a brief discussion of the fundamental working principle of KICs, along with an overview of recent advances and achievements of a variety of electrode materials for dual carbon and non-dual carbon KICs. Furthermore, electrolyte chemistry, binders as well as electrode/electrolyte interface, are summarized. Finally, existing challenges and perspectives on further development of KICs are also presented.

Superior electrochemical performance of layered WTe2 as potassium-ion battery electrode

Potassium-ion batteries or KIBs are prominent candidates among research involving post lithium-ion batteries due to abundant availability, low-cost, and low standard reduction potential of potassium metal. Although some chemistry correlation with other monovalent alkali metal-ion batteries may exist, research on KIB chemistry is still in its infancy. A relevant research aspect of KIB is the development of a stable anode material that can efficiently cycle the large K⁺ ions in its crystal structure within the 0 to 3 V potential window range; providing reasonable charge capacity and high reversibility. To this end, transition metal dichalcogenides or TMDs are promising electrode materials because of their favorable electrochemical properties. In this work, we study electrochemical performance of tungsten ditelluride (WTe₂) TMD as working electrode in a KIB half-cell. Results show that WTe₂, a telluride-based TMD, has high first cycle specific charge capacity-with up to 3.3 K⁺ stored per WTe₂ molecule (at least 4 times that of WS₂ electrode)-stable capacity of 143 mAh g^-1 at 10th cycle number-outperforming WS₂ (66 mAh g^-1) and graphite (95 mAh g^-1)-good reversibility, reasonable cycling stability, and low charge transfer resistance.

Bottom-Up Synthesis of MoS2 /CNTs Hollow Polyhedron with 1T/2H Hybrid Phase for Superior Potassium-Ion Storage

Enslaved to the large-size K-ions, the construction of suitable anode materials with superior and stable potassium-ion storage properties is a major challenge. 1T phase MoS₂ possesses higher conductivity, bigger interlayer distance, and more electrochemically active sites than the 2H phase, which offers intriguing benefits for energy-related applications. In this work, the 1T/2H-phase hybrid MoS₂ nanosheets are successfully anchored in the N-doped carbon nanotube hollow polyhedron (1T/2H-MoS₂ /NCNHP) by a bottom-up solvothermal method. For the synthesized 1T/2H-MoS₂ /NCNHP, the fewer-layer 1T/2H-MoS₂ nanosheets are embedded in an N-doped carbon nanotube hollow polyhedron, with an enlarged interlayer spacing of 0.96 nm. When evaluated as anode material for potassium-ion batteries, the 1T/2H-MoS₂ /NCNHP hybrid presents outstanding potassium storage performance. It delivers a high-specific capacity of 519.2 mAh g^-1 at 50 mA g^-1 and maintains 281.2 mAh g^-1 at 1 A g^-1 over 500 cycles. The good potassium-ion electrochemical performance is attributed to the rational structural design and the synergistic effect of the components. Moreover, the 1T-MoS₂ nanosheet has excellent electrical conductivity and its enlarged interlayer spacing reduces the barrier for the embedding and stripping of K ions. Finally, the practical application of the 1T/2H-MoS₂ /NCNHP electrode material is also evaluated by assembled K-ion full cells.

Biosensors Based on Advanced Sulfur-Containing Nanomaterials

In recent years, sulfur-containing nanomaterials and their derivatives/composites have attracted much attention because of their important role in the field of biosensor, biolabeling, drug delivery and diagnostic imaging technology, which inspires us to compile this review. To focus on the relationships between advanced biomaterials and biosensors, this review describes the applications of various types of sulfur-containing nanomaterials in biosensors. We bring two types of sulfur-containing nanomaterials including metallic sulfide nanomaterials and sulfur-containing quantum dots, to discuss and summarize the possibility and application as biosensors based on the sulfur-containing nanomaterials. Finally, future perspective and challenges of biosensors based on sulfur-containing nanomaterials are briefly rendered.