Nanoconfined Carbon‐Coated Na3V2(PO4)3 Particles in Mesoporous Carbon Enabling Ultralong Cycle Life for Sodium‐Ion Batteries

Na₃V₂(PO₄)₃ (denoted as NVP) has been considered as a promising cathode material for room temperature sodium ion batteries. Nevertheless, NVP suffers from poor rate capability resulting from the low electronic conductivity. Here, the feasibility to approach high rate capability by designing carbon‐coated NVP nanoparticles confined into highly ordered mesoporous carbon CMK‐3 matrix (NVP@C@CMK‐3) is reported. The NVP@C@CMK‐3 is prepared by a simple nanocasting technique. The electrode exhibits superior rate capability and ultralong cyclability (78 mA h g^?1 at 5 C after 2000 cycles) compared to carbon‐coated NVP and pure NVP cathode. The improved electrochemical performance is attributed to double carbon coating design that combines a variety of advantages: very short diffusion length of Na⁺/e^? in NVP, easy access of electrolyte, and short transport path of Na⁺ through carbon toward the NVP nanoparticle, high conductivity transport of electrons through the 3D interconnected channels of carbon host. The optimum design of the core–shell nanostructures with double carbon coating permits fast kinetics for both transported Na⁺ ions and electrons, enabling high‐power performance.     

Flexible Nano‐felts of Carbide‐Derived Carbon with Ultra‐high Power Handling Capability

Nano‐fibrous felts (nano‐felts) of carbide‐derived carbon (CDC) have been developed from the precursor of electrospun titanium carbide (TiC) nano‐felts. Conformal transformation of TiC into CDC conserves main features of the precursor including the high interconnectivity and structural integrity; the developed TiC‐CDC nano‐felts are mechanically flexible/resilient, and can be used as electrode material for supercapacitor application without the addition of any binder. After synthesis through chlorination of the precursor at 600 °C, the TiC‐CDC nano‐fibers show an average pore size of ～1nm, a high specific surface area of 1390 m²/g; and the nano‐fibers have graphitic carbon ribbons embedded in a highly disordered carbon matrix. Graphitic carbon is preserved from the precursor nano‐fibers where a few graphene layers surround TiC nanocrystallites. Electrochemical measurements show a high gravimetric capacitance of 110 F/g in aqueous electrolyte (1 M H₂SO₄) and 65 F/g in organic electrolyte (1.5 M TEA‐BF₄ in acetonitrile). Because of the unique microstructure of TiC‐CDC nano‐felts, a fade of the capacitance of merely 50% at a high scan rate of 5 V/s is observed. A fade of just 15% is observed for nano‐felt film electrodes tested in 1 M H₂ SO₄ at 1 V/s, resulting in a high gravimetric capacitance of 94 F/g. Such a high rate performance is only known for graphene or carbon‐onion based supercapacitors, whereas binders have to be used for the fabrication of those supercapacitors.     

High Performance,Flexible, Solid‐State Supercapacitors Based on a Renewable and Biodegradable Mesoporous Cellulose Membrane

A flexible, transparent, and renewable mesoporous cellulose membrane (mCel‐membrane) featuring uniform mesopores of ≈24.7 nm and high porosity of 71.78% is prepared via a facile and scalable solution‐phase inversion process. KOH‐saturated mCel‐membrane as a polymer electrolyte demonstrates a high electrolyte retention of 451.2 wt%, a high ionic conductivity of 0.325 S cm^?1, and excellent mechanical flexibility and robustness. A solid‐state electric double layer capacitor (EDLC) using activated carbon as electrodes, the KOH‐saturated mCel‐membrane as a polymer electrolyte exhibits a high capacitance of 110 F g^?1 at 1.0 A g^?1, and long cycling life of 10 000 cycles with 84.7% capacitance retention. Moreover, a highly integrated planar‐type micro‐supercapacitor (MSC) can be facilely fabricated by directly depositing the electrode materials on the mCel‐membrane‐based polymer electrolyte without using complicated devices. The resulting MSC exhibits a high areal capacitance of 153.34 mF cm^?2 and volumetric capacitance of 191.66 F cm^?3 at 10 mV s^?1, representing one of the highest values among all carbon‐based MSC devices. These findings suggest that the developed renewable, flexible, mesoporous cellulose membrane holds great promise in the practical applications of flexible, solid‐state, portable energy storage devices that are not limited to supercapacitors.     

Hierarchical Carbide‐Derived Carbon Foams with Advanced Mesostructure as a Versatile Electrochemical Energy‐Storage Material

Highly porous carbide‐derived carbon (CDC) mesofoams (DUT‐70) are prepared by nanocasting of mesocellular silica foams with a polycarbosilane precursor. Ceramic conversion followed by silica removal and high‐temperature chlorine treatment yields CDCs with a hierarchical micro‐mesopore arrangement. This new type of polymer‐based CDC is characterized by specific surface areas as high as 2700 m² g^?1, coupled with ultrahigh micro‐ and mesopore volumes up to 2.6 cm³ g^?1. The relationship between synthesis conditions and the properties of the resulting carbon materials is described in detail, allowing precise control of the properties of DUT‐70. Since the hierarchical pore system ensures both efficient mass transfer and high capacities, the novel CDC shows outstanding performance as an electrode material in electrochemical double‐layer capacitors (EDLCs) with specific capacities above 240 F g^?1 when measured in a symmetrical two‐electrode configuration. Remarkable capacities of 175 F g^?1 can be retained even at high current densities of 20 A g^?1 as a result of the enhanced ion‐transport pathways provided by the cellular mesostructure. Moreover, DUT‐70 can be infiltrated with sulfur and host the active material in lithium–sulfur battery cathodes. Reversible capacities of 790 mAh g^?1 are achieved at a current rate of C/10 after 100 cycles, which renders DUT‐70 an ideal support material for electrochemical energy‐storage applications.     

New Binder‐Free Metal Phosphide–Carbon Felt Composite Anodes for Sodium‐Ion Battery

Metal phosphides are promising anode candidates for sodium‐ion batteries (SIBs) due to their high specific capacity and low operating potential but suffer from poor cycling stability caused by huge volume expansion and poor solid‐state ion transfer rate. Herein, a new strategy to grow a new class of mesoporous metal phosphide nanoarrays on carbon felt (CF) as binder‐free anodes for SIBs is reported. The resultant integrated electrodes demonstrate excellent cycling life up to 1000 times (>90% retention rate) and high rate capability of 535 mAh g^?1 at a current density of 4 A g^?1. Detailed characterization reveals that the synergistic effect of unique mesoporous structure for accommodating huge volume expansion during sodiation/desodiation process, ultrasmall primary particle size (≈10 nm) for providing larger electrode/electrolyte contact area and shorter ion diffusion distance, and 3D conductive networks for facilitating the electrochemical reaction, leads to the extraordinary battery performance. Remarkably, a full SIB using the new CoP₄/CF anode and a Na₃V₂(PO₄)₂F₃ cathode delivers an average operating voltage of ≈3.0 V, a reversible capacity of 553 mAh g^?1, and very high energy density of ≈280 Wh kg^?1 for SIBs. A flexible SIB with outstanding mechanical strength based on this binder‐free new anode is also demonstrated.     

Sulfur‐Embedded Activated Multichannel Carbon Nanofiber Composites for Long‐Life,High‐Rate Lithium–Sulfur Batteries

Despite the 3–5 fold higher energy density than the conventional Li‐ion cells at a lower cost, commercialization of Li–S batteries is hindered by the insulating nature of sulfur and the dissolution of intermediate polysulfides (Li₂S _X , 4 < X ≤ 8) into the electrolyte. The authors demonstrate here multichannel carbon nanofibers that are composed of parallel mesoporous channels connected with micropores as sulfur containment. In addition, hydroxyl functional groups are formed on the carbon surface through a chemical activation to enhance the interaction between sulfur and carbon. In the sulfur embedded composite, the mesoporous multichannel enhances the active material utilization and sulfur loading, while the micropores act as a reaction chamber for sulfur component and trap site for polysulfide with the assistance of the functional groups. This sulfur–carbon composite electrode with 2.2 mg cm^?2 sulfur displays excellent performance with high rate capability (initial capacity of 1351 mA h g^?1 at C/5 rate and 847 mA h g^?1 at 5C rate), maintaining 920 mA h g^?1 even after 300 cycles (a decay of 0.07% per cycle). Furthermore, a stable reversible capacity of as high as ≈1100 mA h g^?1 is realized with a higher sulfur loading of 4.6 mg cm^?2.     

A Flexible Porous Carbon Nanofibers‐Selenium Cathode with Superior Electrochemical Performance for Both Li‐Se and Na‐Se Batteries

A flexible and free‐standing porous carbon nanofibers/selenium composite electrode (Se@PCNFs) is prepared by infiltrating Se into mesoporous carbon nanofibers (PCNFs). The porous carbon with optimized mesopores for accommodating Se can synergistically suppress the active material dissolution and provide mechanical stability needed for the film. The Se@PCNFs electrode exhibits exceptional electrochemical performance for both Li‐ion and Na‐ion storage. In the case of Li‐ion storage, it delivers a reversible capacity of 516 mAh g^?1 after 900 cycles without any capacity loss at 0.5 A g^?1. Se@PCNFs still delivers a reversible capacity of 306 mAh g^?1 at 4 A g^?1. While being used in Na‐Se batteries, the composite electrode maintains a reversible capacity of 520 mAh g^?1 after 80 cycles at 0.05 A g^?1 and a rate capability of 230 mAh g^?1 at 1 A g^?1. The high capacity, good cyclability, and rate capability are attributed to synergistic effects of the uniform distribution of Se in PCNFs and the 3D interconnected PCNFs framework, which could alleviate the shuttle reaction of polyselenides intermediates during cycling and maintain the perfect electrical conductivity throughout the electrode. By rational and delicate design, this type of self‐supported electrodes may hold great promise for the development of Li‐Se and Na‐Se batteries with high power and energy densities.     

Tailored Plum Pudding‐Like Co2P/Sn Encapsulated with Carbon Nanobox Shell as Superior Anode Materials for High‐Performance Sodium‐Ion Capacitors

Sodium‐ion capacitors (SICs) are emerging energy storage devices with high energy, high power, and durable life. Sn is a promising anode material for lithium storage, but the poor conductivity of the a‐NaSn phase upon sodaition hinders its implementation in SICs. Herein, a superior Sn‐based anode material consisting of plum pudding‐like Co₂P/Sn yolk encapsulated with nitrogen‐doped carbon nanobox (Co₂P/Sn@NC) for high‐performance SICs is reported. The 8–10 nm metallic nanoparticles produced in situ are uniformly dispersed in the amorphous Sn matrix serving as conductive fillers to facilitate electron transfer in spite of the formation of electrically resistive a‐NaSn phase during cycling. Meanwhile, the carbon shell buffers the large expansion of active Sn and provides a stable electrode–electrolyte interface. Owing to these merits, the yolk–shell Co₂P/Sn@NC demonstrates a large capacity of 394 mA h g^?1 at 100 mA g^?1, high rate capability of 168 mA h g^?1 at 5000 mA g^?1, and excellent cyclability with 87% capacity retention after 10 000 cycles. By integrating the Co₂P/Sn@NC anode with a peanut shell‐derived carbon cathode in the SIC, high energy densities of 112.3 and 43.7 Wh kg^?1 at power densities of 100 and 10 000 W kg^?1 are achieved.     

Interconnected Frameworks with a Sandwiched Porous Carbon Layer/Graphene Hybrids for Supercapacitors with High Gravimetric and Volumetric Performances

A facile approach to synthesize porous disordered carbon layers as energy storage units coating on graphene sheets to form interconnected frameworks by one‐step pyrolysis of the mixture of graphene oxide/polyaniline and KOH is presented. As effective energy storage units, these porous carbon layers play an important role in enhancing the electrochemical performances. The obtained porous carbon material exhibits a high specific surface area (2927 m² g^?1), hierarchical interconnected pores, moderate pore volume (1.78 cm³ g^?1), short ion diffusion paths, and a high nitrogen level (6 at%). It displays both unparalleled gravimetric (481 F g^?1) and outstanding volumetric capacitance (212 F cm^?3) in an aqueous electrolyte. More importantly, the assembled symmetrical supercapacitor delivers not only high gravimetric (25.7 Wh kg^?1 based on total mass of electroactive materials) but also high volumetric energy densities (11.3 Wh L^?1) in an aqueous electrolyte. Furthermore, the assembled asymmetric supercapacitor yields a maximum energy density up to 88 Wh kg^?1, which is, to the best of our knowledge, the highest value so far reported for carbon//MnO₂ asymmetric supercapacitors in aqueous electrolytes. Therefore, this novel carbon material holds great promise for potential applications in energy‐related technological fields.     

Pore Structure Controlling the Activity of Mesoporous Crystalline CsTaWO6 for Photocatalytic Hydrogen Generation

The quaternary oxide CsTaWO₆ exhibits a very high activity for photocatalytic hydrogen generation and water splitting. To improve its properties with regard to photocatalytic applications, it is prepared with mesoporous morphology for the first time, utilizing a template‐based evaporation‐induced self‐assembly process. The resulting material exhibits a median mesopore size of 10 nm, a surface area of 60 m² g^?1, and high crystallinity after preparation at 550 °C with phase‐pure defect‐pyrochlore structure. To further improve the textural properties of mesoporous CsTaWO₆, the addition of additives to the synthesis procedure is also investigated. By using H₂SO₄/HCl and a carbonization/oxidation procedure, the surface area of the resulting mesoporous CsTaWO₆ is increased to 78 m² g^?1, which is a 20‐fold increase compared to a nonporous reference via sol‐gel preparation, also leading to improved photocatalytic activity. By investigating the ability for photocatalytic hydrogen generation, the importance of high surface area and pore diameter of the resulting materials in comparison to nonporous materials is presented. Interestingly, the photocatalytic activity does not increase linearly with surface area, due to a strong influence of the pore diameter on the photocatalytic activity.     

Stabilization of Insoluble Discharge Products by Facile Aniline Modification for High Performance Li‐S Batteries

Continuous efforts have been made to attain high performance Li‐S batteries by preventing loss of soluble polysulfides, whereas issues related to insoluble discharge products, Li₂S₂ and Li₂S, have been underestimated. A facile and mild method, diazotization, that enables uniform functionalization on the surface of ordered mesoporous carbon (CMK‐3) with aniline functional groups while not deteriorating the original CMK‐3 microstructure is demonstrated. The aniline groups possess favorable interactions with insoluble discharge products. Thus, they homogeneously distribute the insoluble discharge products during cycling. The proposed materials exhibit outstanding electrochemical properties with regard to stability (920 mAh g^?1 at 0.2 C after 100 cycles) and rate capability (814 mAh g^?1 at 1 C) when evaluated as a cathode material for Li‐S batteries.     

Pore and Heteroatom Engineered Carbon Foams for Supercapacitors

Carbonaceous materials are attractive supercapacitor electrode materials due to their high electronic conductivity, large specific surface area, and low cost. Here, a unique hierarchical porous N,O,S‐enriched carbon foam (KNOSC) with high level of structural complexity for supercapacitors is reported. It is fabricated via a combination of a soft‐template method, freeze‐drying, and chemical etching. The carbon foam is a macroporous structure containing a network of mesoporous channels filled with micropores. It has an extremely large specific surface area of 2685 m² g^?1. The pore engineered carbon structure is also uniformly doped with N, O, and S. The KNOSC electrode achieves an outstanding capacitance of 402.5 F g^?1 at 1 A g^?1 and superior rate capability of 308.5 F g^?1 at 100 A g^?1. The KNOSC exhibits a Bode frequency at the phase angle of ?45° of 18.5 Hz, which corresponds to a time constant of 0.054 s only. A symmetric supercapacitor device using KNOSC as electrodes can be charged/discharged within 1.52 s to deliver a specific energy density of 15.2 W h kg^?1 at a power density of 36 kW kg^?1. These results suggest that the pore and heteroatom engineered structures are promising electrode materials for ultrafast charging.     

Sulfur/Oxygen Codoped Porous Hard Carbon Microspheres for High‐Performance Potassium‐Ion Batteries

Potassium‐ion batteries (KIBs) are very promising alternatives to lithium‐ion batteries (LIBs) for large‐scale energy storage. However, traditional carbon anode materials usually show poor performance in KIBs due to the large size of K ions. Herein, a carbonization‐etching strategy is reported for making a class of sulfur (S) and oxygen (O) codoped porous hard carbon microspheres (PCMs) material as a novel anode for KIBs through pyrolysis of the polymer microspheres (PMs) composed of a liquid crystal/epoxy monomer/thiol hardener system. The as‐made PCMs possess a porous architecture with a large Brunauer–Emmett–Teller surface area (983.2 m² g^?1), an enlarged interlayer distance (0.393 nm), structural defects induced by the S/O codoping and also amorphous carbon nature. These new features are important for boosting potassium ion storage, allowing the PCMs to deliver a high potassiation capacity of 226.6 mA h g^?1 at 50 mA g^?1 over 100 cycles and be displaying high stability by showing a potassiation capacity of 108.4 mA h g^?1 over 2000 cycles at 1000 mA g^?1. The density functional theory calculations demonstrate that S/O codoping not only favors the adsorption of K to the PCMs electrode but also reduces its structural deformation during the potassiation/depotassiation. The present work highlights the important role of hierarchical porosity and S/O codoping in potassium storage.     

Heteroatom‐Doped Mesoporous Hollow Carbon Spheres for Fast Sodium Storage with an Ultralong Cycle Life

Carbon materials have attracted significant attention as anode materials for sodium ion batteries (SIBs). Developing a carbon anode with long‐term cycling stability under ultrahigh rate is essential for practical application of SIBs in energy storage systems. Herein, sulfur and nitrogen codoped mesoporous hollow carbon spheres are developed, exhibiting high rate performance of 144 mA h g^?1 at 20 A g^?1, and excellent cycling durability under ultrahigh current density. Interestingly, during 7000 cycles at a current density of 20 A g^?1, the capacity of the electrode gradually increases to 180 mA h g^?1. The mechanisms for the superior electrochemical performance and capacity improvement of the cells are studied by electrochemical tests, ex situ transmission electron microscopy, X‐ray diffraction, X‐ray photoelectron spectroscopy, and Raman analysis of fresh and cycled electrodes. The unique and robust structure of the material can enhance transport kinetics of electrons and sodium ions, and maintain fast sodium storage from the capacitive process under high rate. The self‐rearrangement of the carbon structure, induced by continuous discharge and charge, lead to the capacity improvement with cycles. These results demonstrate a new avenue to design advanced anode materials for SIBs.     

Sulfur‐Impregnated,Sandwich‐Type,Hybrid Carbon Nanosheets with Hierarchical Porous Structure for High‐Performance Lithium‐Sulfur Batteries

Sandwich‐type hybrid carbon nanosheets (SCNMM) consisting of graphene and micro/mesoporous carbon layer are fabricated via a double template method using graphene oxide as the shape‐directing agent and SiO₂ nanoparticles as the mesoporous guide. The polypyrrole synthesized in situ on the graphene oxide sheets is used as a carbon precursor. The micro/mesoporous strcutures of the SCNMM are created by a carbonization process followed by HF solution etching and KOH treatment. Sulfur is impregnated into the hybrid carbon nanosheets to generate S@SCNMM composites for the cathode materials in Li‐S secondary batteries. The microstructures and electrochemical performance of the as‐prepared samples are investigated in detail. The hybrid carbon nanosheets, which have a thickness of about 10–25 nm, high surface area of 1588 m² g^?1, and broad pore size distribution of 0.8–6.0 nm, are highly interconnected to form a 3D hierarchical structure. The S@SCNMM sample with the sulfur content of 74 wt% exhibits excellent electrochemical performance, including large reversible capacity, good cycling stability and coulombic efficiency, and good rate capability, which is believed to be due to the structure of hybrid carbon materials with hierarchical porous structure, which have large specific surface area and pore volume.     

An Improved Li–SeS2 Battery with High Energy Density and Long Cycle Life

Selenium–sulfur solid solutions are a class of potential cathode materials for high energy batteries, since they have higher theoretical capacities than selenium and improved conductivity over sulfur. Here, a high‐performance cathode material by confining 70 wt% of SeS₂ in a highly ordered mesoporous carbon (CMK‐3) framework with a polydopamine (PDA) protection sheath for novel Li–Se/S batteries is reported. With a relatively high SeS₂ mass loading of 2.6–3 mg cm^?2, the CMK‐3/SeS₂@PDA cathode exhibits a high capacity of >1200 mA h g^?1 at 0.2 A g^?1, excellent C‐rate capability of 535 mA h g^?1 at 5 A g^?1, and prolonged life over 500 cycles. Benefitting from the unique advantages of SeS₂ and the rationally designed host framework, this new cathode material demonstrates a feasible strategy to overcome the bottlenecks of current Li–S systems for high energy density rechargeable batteries.     

Ligand‐Assisted Assembly Approach to Synthesize Large‐Pore Ordered Mesoporous Titania with Thermally Stable and Crystalline Framework

A novel ligand‐assisted assembly approach is demonstrated for the synthesis of thermally stable and large‐pore ordered mesoporous titanium dioxide with a highly crystalline framework by using diblock copolymer poly(ethylene oxide)‐b‐polystyrene (PEO‐b‐PS) as a template and titanium isopropoxide (TIPO) as a precursor. Small‐angle X‐ray scattering, X‐ray diffraction (XRD), transmission electron microscopy (TEM), high‐resolution scanning electron microscopy, and N₂‐sorption measurements indicate that the obtained TiO₂ materials possess an ordered primary cubic mesostructure with large, uniform pore diameters of about 16.0 nm, and high Brunauer–Emmett–Teller surface areas of ～112 m² g^?1, as well as high thermal stability (～700 °C). High resolution TEM and wide‐angle XRD measurements clearly illustrate the high crystallinity of the mesoporous titania with an anatase structure in the pore walls. It is worth mentioning that, in this process, in addition to tetrahydrofuran as a solvent, acetylacetone was employed as a coordination agent to avoid rapid hydrolysis of the titanium precursor. Additionally, stepped evaporation and heating processes were adopted to control the condensation rate and facilitate the assembly of the ordered mesostructure, and ensure the formation of fully polycrystalline anatase titania frameworks without collapse of the mesostructure. By employing the obtained mesoporous and crystallized TiO₂ as the photoanode in a dye‐sensitized solar cell, a high power‐conversion efficiency (5.45%) can be achieved in combination with the N719 dye, which shows that this mesoprous titania is a great potential candidate as a catalyst support for photonic‐conversion applications.     

Opening of Bottleneck Pores for the Improvement of Nitrogen Doped Carbon Electrocatalysts

A facile synthesis strategy to control the porosity of ionothermal nitrogen doped carbons is demonstrated. Adenine is used as cheap and biomass based precursor and a mixture of NaCl/ZnCl₂ as combined solvent‐porogen. Variation of the ratio between the two salt influences the pore structure over a wide range. The eutectic mixture leads to micro‐ and mesoporous material with high total pore volume (TPV) of 3.0 cm³ g^?1 and very high surface area of 2900 m² g^?1 essentially rendering the product an “all‐surface‐area” nitrogen doped carbon. Increasing NaCl contents cause a continuous increase of the mesopore size and the formation of additional macropores resulting in a very high maximal TPV of 5.2 cm³ g^?1, showing 2540 m² g^?1 specific surface area using 60 mol% NaCl. Interestingly, the electrocatalytic activity of the samples toward oxygen reduction is strongly affected by the detailed pore structure. The different—however, chemically equivalent—catalysts vary up to 70 mV in their half wave potentials (E _1/2).The sample with optimized pore system shows a high selectivity toward the favored four electron process and an outstanding E _1/2 of ≈880 mV versus reversible hydrogen electrode (RHE), which is one of the best values reported for nitrogen doped carbons so far.     

Mesoporous MoS2 as a Transition Metal Dichalcogenide Exhibiting Pseudocapacitive Li and Na‐Ion Charge Storage

The ion insertion properties of MoS₂ continue to be of widespread interest for energy storage. While much of the current work on MoS₂ has been focused on the high capacity four‐electron reduction reaction, this process is prone to poor reversibility. Traditional ion intercalation reactions are highlighted and it is demonstrated that ordered mesoporous thin films of MoS₂ can be utilized as a pseudocapacitive energy storage material with a specific capacity of 173 mAh g^?1 for Li‐ions and 118 mAh g^?1 for Na‐ions at 1 mV s^?1. Utilizing synchrotron grazing incidence X‐ray diffraction techniques, fast electrochemical kinetics are correlated with the ordered porous structure and with an iso‐oriented crystal structure. When Li‐ions are utilized, the material can be charged and discharged in 20 seconds while still achieving a specific capacity of 140 mAh g^?1. Moreover, the nanoscale architecture of mesoporous MoS₂ retains this level of lithium capacity for 10 000 cycles. A detailed electrochemical kinetic analysis indicates that energy storage for both ions in MoS₂ is due to a pseudocapacitive mechanism.     

NiCo2S4 Nanosheets Grown on Nitrogen‐Doped Carbon Foams as an Advanced Electrode for Supercapacitors

To push the energy density limit of supercapacitors, a new class of electrode materials with favorable architectures is strongly needed. Binary metal sulfides hold great promise as an electrode material for high‐performance energy storage devices because they offer higher electrochemical activity and higher capacity than mono‐metal sulfides. Here, the rational design and fabrication of NiCo₂S₄ nanosheets supported on nitrogen‐doped carbon foams (NCF) is presented as a novel flexible electrode for supercapacitors. A facile two‐step method is developed for growth of NiCo₂S₄ nanosheets on NCF with robust adhesion, involving the growth of Ni‐Co precursor and subsequent conversion into NiCo₂S₄ nanosheets through sulfidation process. Benefiting from the compositional features and 3D electrode architectures, the NiCo₂S₄/NCF electrode exhibits greatly improved electrochemical performance with ultrahigh capacitance (877 F g^?1 at 20 A g^?1) and excellent cycling stability. Moreover, a binder‐free asymmetric supercapacitor device is also fabricated by using NiCo₂S₄/NCF as the positive electrode and ordered mesoporous carbon (OMC)/NCF as the negative electrode; this demonstrates high energy density (≈45.5 Wh kg^?1 at 512 W kg^?1).