Uniform Incorporation of Flocculent Molybdenum Disulfide Nanostructure into Three-Dimensional Porous Graphene as an Anode for High-Performance Lithium Ion Batteries and Hybrid Supercapacitors

Molybdenum Sulfide Nanoflowers as Electrodes for Efficient and Scalable Lithium-Ion Capacitors

Hybrid supercapacitors (HSCs) bridge the unique advantages of batteries and capacitors and are considered promising energy storage devices for hybrid vehicles and other electronic gadgets. Lithium-ion capacitors (LICs) have attained particular interest due to their higher energy and power density than traditional supercapacitor devices. The limited voltage window and the deterioration of anode materials upsurged the demand for efficient and stable electrode materials. Two-dimensional (2D) molybdenum sulfide (MoS2) is a promising candidate for developing efficient and durable LICs due to its wide lithiation potential and unique layer structure, enhancing charge storage efficiency. Modifying the extrinsic features, such as the dimensions and shape at the nanoscale, serves as a potential path to overcome the sluggish kinetics observed in the LICs. Herein, the MoS2 nanoflowers have been synthesized through a hydrothermal route. The developed LIC exhibited a specific capacitance of 202.4 F g-1 at 0.25 A g-1 and capacitance retention of >90 % over 5,000 cycles. Using an ether electrolyte improved the voltage window (2.0 V) and enhanced the stability performance. The ex-situ material characterization after the stability test reveals that the storage mechanism in MoS2-LICs is not diffusion-controlled. Instead, the fast surface redox reactions, especially intercalation/deintercalation of ions, are more prominent for charge storage.

2D Hybrid Nanocomposite Materials (h-BN/G/MoS2) as a High-Performance Supercapacitor Electrode

The nanocomposites of hexagonal boron nitride, molybdenum disulfide, and graphene (h-BN/G/MoS2) are promising energy storage materials. The originality of the current work is the first-ever synthesis of 2D-layered ternary nanocomposites of boron nitrate, graphene, and molybdenum disulfide (h-BN/G/MoS2) using ball milling and the sonication method and the investigation of their applicability for supercapacitor applications. The morphological investigation confirms the well-dispersed composite material production, and the ternary composite appears to be made of h-BN and MoS2 wrapping graphene. The electrochemical characterization of the prepared samples is evaluated by cyclic voltammetry and galvanostatic charge/discharge tests. With a high specific capacitance of 392 F g-1 at a current density of 1 A g-1 and an outstanding cycling stability with around 96.4% capacitance retention after 10,000 cycles, the ideal 5% BN_G@MoS2_90@10 composite demonstrates exceptional capabilities. Furthermore, a symmetric supercapacitor (5% BN_G@MoS2_90@10 composite) exhibits a 94.1% capacitance retention rate even after 10,000 cycles, an energy density of 16.4 W h kg-1, and a power density of 501 W kg-1. The findings show that the preparation procedure is safe for the environment, manageable, and suitable for mass production, which is crucial for advancing the electrode materials used in supercapacitors.

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.

Flexible and Freestanding MoS2/Graphene Composite for High-Performance Supercapacitors

Two-dimensional atomically thick materials such as graphene and layered molybdenum disulfide (MoS2) have been studied as potential energy storage materials because of their high specific surface area, potential redox activity, and mechanical flexibility. However, because of the layered structure restacking and poor electrical conductivity, these materials are unable to attain their full potential. Composite electrodes made of a mixture of graphene and MoS2 have been shown to partially resolve these issues in the past, although their performance is still limited by inadequate mixing at the nanoscale. Herein, we report three composites via a simple ball-milling method and analyze supercapacitor electrodes. Compared with pristine graphene and MoS2, the composites showed high capacitance. The as-obtained MoS2@Graphene composite (1:9) possesses a high surface area and uniform dispersion of MoS2 on the graphene sheet. The MoS2@Graphene (1:9) composite electrode has a high specific capacitance of 248 F g-1 at 5 A g-1 in an electrochemical supercapacitor compared with the other two composites. Simultaneously, the flexible symmetric supercapacitor device prepared demonstrated superior flexibility and a long lifespan (93% capacitance retention after 8000 cycles) with no obvious changes in performance under different angles. In portable and wearable energy storage devices, the current experimental results will result in scalable, freestanding hybrid electrodes with improved, flexible, supercapacitive performance.

Construction of thickness-controllable bimetallic sulfides/reduced graphene oxide as a binder-free positive electrode for hybrid supercapacitors

Devices for electrochemical energy storage with exceptional capacitance and rate performance, outstanding energy density, simple fabrication, long-term stability, and remarkable reversibility have always been in high demand. Herein, a high-performance binder-free electrode (3D NiCuS/rGO) was fabricated as a supercapacitor by a simple electrodeposition process on a Ni foam (NF) surface. The thickness of the deposited materials on the NF surface was adjusted by applying a low cycle number of cyclic voltammetry (5 cycles) which produced a thin layer and thus enabled the easier penetration of electrolytes to promote electron and charge transfer. The NiCuS was anchored by graphene layers producing nicely integrated materials leading to a higher electroconductivity and a larger surface area electrode. The as-fabricated electrode displayed a high specific capacitance (2211.029 F g-1 at 5 mV s-1). The NiCuS/rGO/NF//active carbon device can achieve a stable voltage window of 1.5 V with a highly specific capacitance of 84.3 F g-1 at a current density of 1 A g-1. At a power density of 749 W kg-1, a satisfactory energy density of 26.3 W h kg-1 was achieved, with outstanding coulombic efficiency of 100% and an admirable life span of 96.2% after 10 000 GCD cycles suggesting the significant potential of the as-prepared materials for practical supercapacitors.

Strategies for Advanced Supercapacitors Based on 2D Transition Metal Dichalcogenides: From Material Design to Device Setup

Recently, the development of new materials and devices has become the main research focus in the field of energy. Supercapacitors (SCs) have attracted significant attention due to their high power density, fast charge/discharge rate, and excellent cycling stability. With a lamellar structure, 2D transition metal dichalcogenides (2D TMDs) emerge as electrode materials for SCs. Although many 2D TMDs with excellent energy storage capability have been reported, further optimization of electrode materials and devices is still needed for competitive electrochemical performance. Previous reviews have focused on the performance of 2D TMDs as electrode materials in SCs, especially on their modification. Herein, the effects of element doping, morphology, structure and phase, composite, hybrid configuration, and electrolyte are emphatically discussed on the overall performance of 2D TMDs-based SCs from the perspective of device optimization. Finally, the opportunities and challenges of 2D TMDs-based SCs in the field are highlighted, and personal perspectives on methods and ideas for high-performance energy storage devices are provided.

Recent Advancements in Chalcogenides for Electrochemical Energy Storage Applications

Energy storage has become increasingly important as a study area in recent decades. A growing number of academics are focusing their attention on developing and researching innovative materials for use in energy storage systems to promote sustainable development goals. This is due to the finite supply of traditional energy sources, such as oil, coal, and natural gas, and escalating regional tensions. Because of these issues, sustainable renewable energy sources have been touted as an alternative to nonrenewable fuels. Deployment of renewable energy sources requires efficient and reliable energy storage devices due to their intermittent nature. High-performance electrochemical energy storage technologies with high power and energy densities are heralded to be the next-generation storage devices. Transition metal chalcogenides (TMCs) have sparked interest among electrode materials because of their intriguing electrochemical properties. Researchers have revealed a variety of modifications to improve their electrochemical performance in energy storage. However, a stronger link between the type of change and the resulting electrochemical performance is still desired. This review examines the synthesis of chalcogenides for electrochemical energy storage devices, their limitations, and the importance of the modification method, followed by a detailed discussion of several modification procedures and how they have helped to improve their electrochemical performance. We also discussed chalcogenides and their composites in batteries and supercapacitors applications. Furthermore, this review discusses the subject’s current challenges as well as potential future opportunities.

A Comprehensive Review of Graphene-Based Anode Materials for Lithium-ion Capacitors

Lithium-ion capacitors (LICs) are considered to be one of the most promising energy storage devices which have the potential of integrating high energy of lithium-ion batteries and high power and long cycling life of supercapacitors into one system. However, the current LICs could only provide high power density at the cost of low energy density due to the sluggish Li+ diffusion and/or low electrical conductivity of the anode materials. Moreover, the serious capacity and kinetics imbalances between anode and cathode result in not only inferior rate performance but also unsatisfactory cycling stability. Therefore, designing high-power and structure stable anode materials is of great significance for practical LICs. Under this circumstance, graphene-based materials have been intensively explored as anodes in LICs due to their unique structure and outstanding electrochemical properties and attractive achievements have been made. In this review, the recent progresses of graphene-based anode materials for LICs are systematically summarized. Their synthesis procedure, structure and electrochemical performance are discussed with a special focus on the role of graphene. Finally, the outlook and remaining challenges are presented with some constructive guidelines for future research.

Rational Design of Embedded CoTe2 Nanoparticles in Freestanding N-Doped Multichannel Carbon Fibers for Sodium-Ion Batteries with Ultralong Cycle Lifespan

Although sodium-ion batteries (SIBs) have high potential for applications in large-scale energy storage, their limited cycle life and unsatisfactory energy density hinder their commercial applications. Here, a superior stable CoTe₂/carbon anode, in which CoTe₂ nanoparticles are embedded in freestanding N-doped multichannel carbon fiber (CoTe₂@NMCNFs), with ultralong cycle life for SIBs, is reported. Specifically, CoTe₂ nanoparticles are uniformly dispersed in the carbon matrix to inhibit its volume expansion and agglomeration during the desodiation/sodiation process, enabling a high-capacity and stable energy storage (retains 204.3 mAh g^-1/612.9 mAh cm^-3 at 1 A g^-1 after 2000 cycles with an ultralow capacity decay of 0.016% per cycle). Moreover, a CoTe₂@NMCNFs electrode exhibits a pseudocapacitive-dominated behavior, enabling the high-rate performance (152.4 mAh g^-1/457.2 mAh cm^-3 at 10 A g^-1). The battery-capacitive dual-model reaction mechanism and outstanding reversibility of the CoTe₂@NMCNFs composite are systematically investigated by ex situ XRD/SEM/TEM and a galvanostatic intermittent titration technique test, as well as surface capacitance calculations. More importantly, the fabricated sodium-ion CoTe₂@NMCNFs//P2-NaNMMT-4 full cell delivers a stable reversible capacity of 445 Wh kg^-1_anode at 0.2 A g^-1 and an excellent rate performance. The facile synthetic approach together with unique nanostructural design, provides a meaningful reference for the rational design of next-generation ultralong cycle-life SIBs anodes.

Application of multi-active center organic quinone molecular functionalized graphene in fully pseudocapacitive asymmetric supercapacitors

5, 7, 12, 14-pentacenetetrone (PT), polycyclic quinone derivatives, are rich in carbonyl, which were investigated as a novel organic electrode material for supercapacitors. PT with aπconjugated system, is a flat molecule, generating strongπ-πinteractions between molecules. PT molecules were uniformly fixed on conductive reduced graphene oxide (rGO) throughπ-πinteraction by one-step solvothermal method, forming a three-dimensional cross-linked PT@rGO hydrogel. This composite structure was conducive to reducing the charge transfer resistance and promoting the Faraday reaction of electrode, which achieved the superposition of electric double-layer capacitance and pseudocapacitance. Appropriate organic molecular loading can effectively improve electrochemical performance. The optimal PT@rGO electrode material displayed the specific capacitance of 433.2 F g^-1at 5 mV s^-1with an excellent rate capability in 1 mol l^-1H₂SO₄electrolyte. Finally, the fully pseudocapacitive asymmetric supercapacitor has been assembled by using PT@rGO as positive electrode and benz[a]anthracene-7,12-quinone (BAQ) modified rGO(BAQ/rGO)as negative electrode, which exhibited the good energy storage performance in a cell voltage of 1.8 V.

Electrochemical performance of a self-assembled two-dimensional heterostructure of rGO/MoS2/h-BN

We report the preparation and electrochemical performance evaluation of a two-dimensional (2D) self-assembled heterostructure of graphene oxide (rGO), molybdenum disulphide (MoS₂), and hexagonal boron nitride (h-BN). In the present study, the rGO-MoS₂-h-BN (GMH) multi-layered GMH heterostructure is fabricated via an in situ chemical route. Based on material analysis, the composite consists of bond conformations of C-B-C, Mo-S, C-N, B-N, and Mo-C, indicating the layered stacks of rGO/h-BN/MoS₂. In electrochemical analysis, the composite showed superior performance in the aqueous medium of cobalt sulphate (CoSO₄) over other samples. CV measurements, performed over the range 10 to 100 mV s^-1, showed a change in specific capacitance (C _sp) from 800 to 100 F g^-1. GMH showed almost no degradation up to 20 000 cycles @ 100 mV s^-1. The calculated C _sp, energy density (E _D), and power density (P _D) are discussed in light of Nyquist, Bode, and Ragone analysis. An equivalent circuit is simulated for the cell and its discrete electronic components are discussed. Due to its larger effective electron diffusion length > 1000 μm, broadly, the composite showed battery-like characteristics, as supported by radical paramagnetic resonance and transport response studies. The symmetric electrodes prepared in one step are facile to fabricate, easy to integrate and involve no pre or post-treatment. They possess superior flat cell character, are cost effective, and are favourable towards practicality at an industrial scale, as demonstrated on the laboratory bench. The details are presented.

Hierarchically Nanoporous Pyropolymers Derived from Waste Pinecone as a Pseudocapacitive Electrode for Lithium Ion Hybrid Capacitors

The non-aqueous asymmetric lithium ion hybrid capacitor (LIHC) is a tactical energy storage device composed of a faradic and non-faradic electrode pair, which aims to achieve both high energy and great power densities. On the other hand, the different types of electrode combinations cause severe imbalances in energy and power capabilities, leading to poor electrochemical performance. Herein, waste pinecone-derived hierarchically porous pyropolymers (WP-HPPs) were fabricated as a surface-driven pseudocapacitive electrode, which has the advantages of both faradic and non-faradic electrodes. The unique materials properties of WP-HPPs possessing high effective surface areas and hierarchically open nanopores led to high specific capacities of ~412 mA h g⁻¹ and considerable rate/cycling performance as a cathode for LIHCs. In particular, nanometer-scale pores, approximately 3 nm in size, plays a key role in the pseudocapacitive charge storage behaviors because open nanopores can transport solvated Li-ions easily into the inside of complex carbon structures and a large specific surface area can be provided by the effective active surface for charge storage. In addition, WP-HPP-based asymmetric LIHCs assembled with a pseudocapacitive counterpart demonstrated feasible electrochemical performance, such as maximum specific energy and specific power of ~340 Wh kg⁻¹ and ~11,000 W kg⁻¹, respectively, with significant cycling stability.

Two-Dimensional Transition Metal Chalcogenides for Alkali Metal Ions Storage

On the heels of exacerbating environmental concerns and ever-growing global energy demand, development of high-performance renewable energy-storage and -conversion devices has aroused great interest. The electrode materials, which are the critical components in electrochemical energy storage (EES) devices, largely determine the energy-storage properties, and the development of suitable active electrode materials is crucial to achieve efficient and environmentally friendly EES technologies albeit the challenges. Two-dimensional transition-metal chalcogenides (2D TMDs) are promising electrode materials in alkali metal ion batteries and supercapacitors because of ample interlayer space, large specific surface areas, fast ion-transfer kinetics, and large theoretical capacities achieved through intercalation and conversion reactions. However, they generally suffer from low electronic conductivities as well as substantial volume change and irreversible side reactions during the charge/discharge process, which result in poor cycling stability, poor rate performance, and low round-trip efficiency. In this Review, recent advances of 2D TMDs-based electrode materials for alkali metal-ion energy-storage devices with the focus on lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), potassium-ion batteries (PIBs), high-energy lithium-sulfur (Li-S), and lithium-air (Li-O₂ ) batteries are described. The challenges and future directions of 2D TMDs-based electrode materials for high-performance LIBs, SIBs, PIBs, Li-S, and Li-O₂ batteries as well as emerging alkali metal-ion capacitors are also discussed.

Layered Transition Metal Dichalcogenide-Based Nanomaterials for Electrochemical Energy Storage

The rapid development of electrochemical energy storage (EES) systems requires novel electrode materials with high performance. A typical 2D nanomaterial, layered transition metal dichalcogenides (TMDs) are regarded as promising materials used for EES systems due to their large specific surface areas and layer structures benefiting fast ion transport. The typical methods for the preparation of TMDs and TMD-based nanohybrids are first summarized. Then, in order to improve the electrochemical performance of various kinds of rechargeable batteries, such as lithium-ion batteries, lithium-sulfur batteries, sodium-ion batteries, and other types of emerging batteries, the strategies for the design and fabrication of layered TMD-based electrode materials are discussed. Furthermore, the applications of layered TMD-based nanomaterials in supercapacitors, especially in untraditional supercapacitors, are presented. Finally, the existing challenges and promising future research directions in this field are proposed.

Encapsulation of MoSe2 in carbon fibers as anodes for potassium ion batteries and nonaqueous battery-supercapacitor hybrid devices

Potassium ion batteries (PIBs) are considered as promising alternatives to sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs), which can be ascribed to the rich abundance of potassium resources, low cost and high safety. Currently, the development of anode materials for PIBs is still confronted with many serious problems, such as low capacity and poor cycling performance. In this work, sheet-like MoSe₂ implanted on the surfaces of carbon nanofibers is successfully synthesized through a simple electrospinning and selenization route. MoSe₂/C-700 (selenization at 700 °C) maintains high structural stability and facilitates the intercalation/deintercalation of K⁺, which benefits from one-dimensional nanofibers with good structural stability and MoSe₂ with an expanded interlayer spacing. As a whole, MoSe₂/C-700 as an anode for PIBs shows a high reversible capacity of 316 mA h g^-1 at 100 mA g^-1 over 100 cycles. It also displays a specific capacity of 81 mA h g^-1 at 100 mA g^-1 over 100 cycles when it first serves as an electrode material for nonaqueous potassium-based battery-supercapacitor hybrid (BSH) devices.

Ultra-Thin ReS2 Nanosheets Grown on Carbon Black for Advanced Lithium-Ion Battery Anodes

ReS2 nanosheets are grown on the surface of carbon black (CB) via an efficient hydrothermal method. We confirmed the ultra-thin ReS2 nanosheets with ≈1-4 layers on the surface of the CB (ReS2@CB) by using analytical techniques of field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM). The ReS2@CB nanocomposite showed high specific capacities of 760, 667, 600, 525, and 473 mAh/g at the current densities of 0.1 (0.23 C), 0.2 (0.46 C), 0.3 (0.7 C), 0.5 (1.15 C) and 1.0 A/g (2.3 C), respectively, in conjunction with its excellent cycling performance (432 mAh/g at 2.3 C; 91.4% capacity retention) after 100 cycles. Such LIB performance is greatly higher than pure CB and ReS2 powder samples. These results could be due to the following reasons: (1) the low-cost CB serves as a supporter enabling the formation of ≈1-4 layered nanosheets of ReS2, thus avoiding its agglomeration; (2) the CB enhances the electrical conductivity of the ReS2@CB nanocomposite; (3) the ultra-thin (1-4 layers) ReS2 nanosheets with imperfect structure can function as increasing the number of active sites for reaction of Li+ ions with electrolytes. The outstanding performance and unique structural characteristics of the ReS2@CB anodes make them promising candidates for the ever-increasing development of advanced LIBs.

ZnFe2O4@Carbon Core-Shell Nanoparticles Encapsulated in Reduced Graphene Oxide for High-Performance Li-Ion Hybrid Supercapacitors

Li-ion hybrid supercapacitors (Li-HSCs) are attracting extensive attention because of their high energy/power densities. However, the performance of most Li-HSCs suffers from the limitation of the sluggish kinetics of battery-type anodes. Herein, we demonstrate that with dual protection of carbon and graphene, a three-dimensional, strongly coupled ZnFe₂O₄@C/reduced graphene oxide (RGO) composite anode provides an effective solution to this issue. The covalent C-O-M linkage between ZnFe₂O₄ nanoparticles and C/RGO promotes charge transfer and enhances structural stability. Two kinds of carbon-based buffering layers are able to well accommodate the volume change during charging/discharging, endowing the composite anode with high rate performance (692 mA h g^-1 at 5 A g^-1) and outstanding cycle life (98.3% of capacity retention after 700 cycles at 1 A g^-1). The resulting ZnFe₂O₄@C/RGO//activated carbon Li-HSC shows an ultrahigh energy density of 174 W h kg^-1, excellent power density of 51.4 kW kg^-1 (at 109 W h kg^-1), and superior cycle life (80.5% of retention capacity after 10 000 cycles at 5 A g^-1).

Unraveling the Impact of Ether and Carbonate Electrolytes on the Solid-Electrolyte Interface and the Electrochemical Performances of ZnSe@C Core-Shell Composites as Anodes of Lithium-Ion Batteries

The recognition of the solid electrolyte interface (SEI) between the electrode materials and electrolyte is limiting the selection of electrode materials, electrolytes, and further the electrochemical performance of batteries. Herein, we report ZnSe@C core-shell nanocomposites derived from ZIF-8 as anode materials of lithium-ion batteries, the electrochemical performances, and SEI films formed on ZnSe@C in both ether and carbonate electrolytes. It is found that ZnSe@C delivers a reversible capacity of 617.1 mA h·g^-1 after 800 cycles at 1 A·g^-1 in the ether electrolyte, much higher than that in the carbonate electrolyte. Both ex situ X-ray diffraction and X-ray photoelectron spectroscopies reveal that stable SEI films are formed on ZnSe@C in the ether electrolyte while selenium is involved in the formation of SEI films and further dissolved into the carbonate electrolyte because of the concurrent decomposition of electrolytes and insertion of Li⁺ into ZnSe, which differentiates between the cycling performances of ZnSe@C composites in ether and carbonate electrolytes.

Building Next-Generation Li-ion Capacitors with High Energy: An Approach beyond Intercalation

Hybridization of two prominent electrochemical energy storage systems, such as high-energy Li-ion batteries and high-power supercapacitors into a single system, tends to deliver high-energy and high-power capabilities; such systems are often called Li-ion capacitors (LICs). The utilization of battery-type electrodes, which undergo a traditional intercalation process, in LICs provides the necessary energy; however, their limited reversible capacities and higher redox potentials (except graphite and hard carbon) hinder achieving high values. Using materials that can undergo either alloying or conversion or both together with Li, rather than intercalation, is an attractive approach to achieve high energy without compromising both power capability and cyclability. This Perspective discusses the possibility of using high-capacity, exhibiting relatively lower redox potential than transition metal-based intercalation hosts, low-cost materials in conversion and alloying reactions with Li, along with prelithiation strategies (Aravindan, V.; Lee, Y.-S.; Madhavi, S. Best Practices for Mitigating Irreversible Capacity Loss of Negative Electrodes in Li-Ion Batteries. Adv. Energy Mater. 2017, 7, 1602607). Future prospects on working with alloying and conversion-type materials are discussed in detail.

Synthesis and Supercapacitor Performance of Polyaniline/Nitrogen-Doped Ordered Mesoporous Carbon Composites

The electrochemical property of ordered mesoporous carbon (OMC) can be changed significantly due to the incorporating of electron-donating heteroatoms into OMC. Here, we demonstrate the successful fabrication of nitrogen-doped ordered mesoporous carbon (NOMC) materials to be used as carbon substrates for loading polyaniline (PANI) by in situ polymerization. Compared with NOMC, the PANI/NOMC prepared with a different mass ratio of PANI and NOMC exhibits remarkably higher electrochemical specific capacitance. In a typical three-electrode configuration, the hybrid has a specific capacitance about 276.1 F/g at 0.2 A/g with a specific energy density about 38.4 Wh/kg. What is more, the energy density decreases very slowly with power density increasing, which is a different phenomenon from other reports. PANI/NOMC materials exhibit good rate performance and long cycle stability in alkaline electrolyte (~ 80% after 5000 cycles). The fabrication of PANI/NOMC with enhanced electrochemical properties provides a feasible route for promoting its applications in supercapacitors.

Emerging Robust Heterostructure of MoS2-rGO for High-Performance Supercapacitors

The intermittent nature of renewable energy resources has led to a continuous mismatch between energy demand and supply. A possible solution to overcome this persistent problem is to design appropriate energy-storage materials. Supercapacitors based on different nanoelectrode materials have emerged as one of the promising storage devices. In this work, we investigate the supercapacitor properties of a molybdenum disulfide-reduced graphene oxide (rGO) heterostructure-based binder-free electrode, which delivered a high specific capacitance (387.6 F g^-1 at 1.2 A g^-1) and impressive cycling stability (virtually no loss up to 1000 cycles). In addition, the possible role of rGO in the composite toward synergistically enhanced supercapacitance has been highlighted. Moreover, an attempt has been made to correlate the electrochemical impedance spectroscopy studies with the voltammetric analyses. The performance exceeds that of the reported state-of-the-art structures.

Carbon nanofibers (CNFs) supported cobalt- nickel sulfide (CoNi2S4) nanoparticles hybrid anode for high performance lithium ion capacitor

Lithium ion capacitors possess an ability to bridge the gap between lithium ion battery and supercapacitor. The main concern of fabricating lithium ion capacitors is poor rate capability and cyclic stability of the anode material which uses sluggish faradaic reactions to store an electric charge. Herein, we have fabricated high performance hybrid anode material based on carbon nanofibers (CNFs) and cobalt-nickel sulfide (CoNi₂S₄) nanoparticles via simple electrospinning and electrodeposition methods. Porous and high conducting CNF@CoNi₂S₄ electrode acts as an expressway network for electronic and ionic diffusion during charging-discharging processes. The effect of anode to cathode mass ratio on the performance has been studied by fabricating lithium ion capacitors with different mass ratios. The surface controlled contribution of CNF@CoNi₂S₄ electrode was 73% which demonstrates its excellent rate capability. Lithium ion capacitor fabricated with CNF@CoNi₂S₄ to AC mass ratio of 1:2.6 showed excellent energy density of 85.4 Wh kg⁻¹ with the power density of 150 W kg⁻¹. Also, even at the high power density of 15 kW kg⁻¹, the cell provided the energy density of 35 Wh kg⁻¹. This work offers a new strategy for designing high-performance hybrid anode with the combination of simple and cost effective approaches.

Hydrothermal-Assisted Sintering Strategy Towards Porous- and Hollow-Structured LiNb3O8 Anode Material

Porous- and hollow-structured LiNb₃O₈ anode material was prepared by a hydrothermal-assisted sintering strategy for the first time. The phase evolution was studied, and the formation mechanism of the porous and hollow structure was proposed. The formation of the unique structure can be attributed to the local existence of liquid phase because of the volatilization of Li element. As the anode material, the initial discharge capacity is 285.1 mAhg^-1 at 0.1 C, the largest discharge capacity reported so far for LiNb₃O₈. Even after 50 cycles, the reversible capacity can still maintain 77.6 mAhg^-1 at 0.1 C, about 2.5 times of that of LiNb₃O₈ samples prepared by traditional solid-state methods. The significant improvement of Li storage capacity can be attributed to the special porous and hollow structure, which provides a high density of active sites and short parallel channels for fast intercalation of Li⁺ ions through the surface.

Nanostructured Three-Dimensional (3D) Assembly of 2D MoS2 and Graphene Directly Build From Acidic Graphite Oxide

A 3D highly interconnected macroporous network of reduced GO having finely dispersed few-layered 2D MoS₂ nanosheets was constructed through direct use of acidic graphite oxide (GO) for the first time. This facile and technologically scalable process can afford efficient hydrodesulfurization electrocatalysts as potential anode materials at lower cost, and can circumvent the poor thermal stability and recyclability of the material. The strategy provided here can be the basis to design and develop practical processes to address the ultimate goal of large-scale manufacturing of hybrids composed of 2D materials for various energy and catalysis applications.

A Novel and Generalized Lithium-Ion-Battery Configuration utilizing Al Foil as Both Anode and Current Collector for Enhanced Energy Density

A novel battery configuration based on an aluminum foil anode and a conventional cathode is developed. The aluminum foil plays a dual role as both the active anode material and the current collector, which enhances the energy density of the packaged battery, and reduces the production cost. This generalized battery configuration has high potential for application in next-generation lithium-ion batteries.

Small biomolecule sensors based on an innovative MoS2–rGO heterostructure modified electrode platform: a binder-free approach

Hydrothermally synthesized MoS₂–rGO nanoflowers can simultaneously sense ascorbic acid (AA), dopamine (DA) and uric acid (UA) with good separating peak-to-peak potentials.

Layer-structured nanohybrid MoS2@rGO on 3D nickel foam for high performance energy storage applications

MoS₂@reduced graphene oxide on 3D nickel foam was synthesized using an inexpensive room-temperature two-step method composed of the layer-by-layer method and solution-based successive ionic layer adsorption and reaction.

Dopamine-Induced Formation of Ultrasmall Few-Layer MoS2 Homogeneously Embedded in N-Doped Carbon Framework for Enhanced Lithium-Ion Storage

Molybdenum disulfide with a layered structure and high theoretical capacity is attracting extensive attention for high-performance lithium-ion batteries. In this study, a simple and scalable method by freeze-drying of (NH₄)₂MoS₄ and dopamine mixed solutions along with subsequent calcination is developed to realize the self-assembly of hierarchical MoS₂/carbon composite nanosheets via the effect of dopamine-induced morphology transformation, in which ultrasmall few-layer MoS₂ nanosheets were homogeneously embedded into a N-doped carbon framework (denoted as MoS₂@N-CF). The embedded ultrasmall MoS₂ nanosheets (∼5 nm in length) in the composites consist of less than five layers with an expanded interlayer spacing of the (002) plane. When tested as anode materials for rechargeable Li-ion batteries, the obtained MoS₂@N-CF nanosheets exhibit outstanding electrochemical performance in terms of high specific capacity (839.2 mAh g^-1 at 1 A g^-1), high initial Coulombic efficiency (85.2%), and superior rate performance (702.1 mAh g^-1 at 4 A g^-1). Such intriguing electrochemical performance was attributed to the synergistic effect of uniform dispersion of few-layer MoS₂ into the carbon framework, expanded interlayer spacing, and enhanced electronic conductivity in the unique hierarchical architecture. This work provides a simple and effective strategy for the uniform integration of MoS₂ with carbonaceous materials to significantly boost their electrochemical performance.

Carbon-Coated Porous Aluminum Foil Anode for High-Rate, Long-Term Cycling Stability, and High Energy Density Dual-Ion Batteries

A 3D porous Al foil coated with a uniform carbon layer (pAl/C) is prepared and used as the anode and current collector in a dual-ion battery (DIB). The pAl/C-graphite DIB demonstrates superior cycling stability and high rate performance, achieving a highly reversible capacity of 93 mAh g^-1 after 1000 cycles at 2 C over the voltage range of 3.0-4.95 V. In addition, the DIB could achieve an energy density of ≈204 Wh kg^-1 at a high power density of 3084 W kg^-1 .

Electrochemical and Capacitive Properties of Carbon Dots/Reduced Graphene Oxide Supercapacitors

There is much recent interest in graphene-based composite electrode materials because of their excellent mechanical strengths, high electron mobilities, and large specific surface areas. These materials are good candidates for applications in supercapacitors. In this work, a new graphene-based electrode material for supercapacitors was fabricated by anchoring carbon dots (CDs) on reduced graphene oxide (rGO). The capacitive properties of electrodes in aqueous electrolytes were systematically studied by galvanostatic charge-discharge measurements, cyclic voltammetry, and electrochemical impedance spectroscopy. The capacitance of rGO was improved when an appropriate amount of CDs were added to the material. The CD/rGO electrode exhibited a good reversibility, excellent rate capability, fast charge transfer, and high specific capacitance in 1 M H₂SO₄. Its capacitance was as high as 211.9 F/g at a current density of 0.5 A/g. This capacitance was 74.3% higher than that of a pristine rGO electrode (121.6 F/g), and the capacitance of the CD/rGO electrode retained 92.8% of its original value after 1000 cycles at a CDs-to-rGO ratio of 5:1.

2D materials for renewable energy storage devices: Outlook and challenges

We review cost-effective, clean and durable alternative energy devices based on 2D materials.

Hybrid two-dimensional materials in rechargeable battery applications and their microscopic mechanisms

Advances in two-dimensional (2D) hybrid nanomaterials in electrochemical energy storage and their microscopic mechanisms are summarized and reviewed.