Microporous Polypyrrole‐Coated Graphene Foam for High‐Performance Multifunctional Sensors and Flexible Supercapacitors

This study reports on the fabrication of pressure/temperature/strain sensors and all‐solid‐state flexible supercapacitors using only polydimethylsiloxane coated microporous polypyrrole/graphene foam composite (PDMS/PPy/GF) as a common material. A dual‐mode sensor is designed with PDMS/PPy/GF, which measures pressure and temperature with the changes of current and voltage, respectively, without interference to each other. The fabricated dual‐mode sensor shows high sensitivity, fast response/recovery, and high durability during 10 000 cycles of pressure loading. The pressure is estimated using the thermoelectric voltage induced by simultaneous increase in temperature caused by a finger touch on the sensor. Additionally, a resistor‐type strain sensor fabricated using the same PDMS/PPy/GF could detect the strain up to 50%. Flexible, high performance supercapacitor used as a power supply is fabricated with electrodes of PPy/GF for its high surface area and pseudocapacitance. Furthermore, an integrated system of such fabricated multifunctional sensors and a supercapacitor on a skin‐attachable flexible substrate using liquid–metal interconnections operates well, whereas sensors are driven by the power of the supercapacitor. This study clearly demonstrates that the appropriate choice of a single functional material enables fabrication of active multifunctional sensors for pressure, temperature, and strain, as well as the supercapacitor, that could be used in wirelessly powered wearable devices.     

Facile Synthesis of Blocky SiOx/C with Graphite‐Like Structure for High‐Performance Lithium‐Ion Battery Anodes

SiO_x‐containing graphite composites have aroused great interests as the most promising alternatives for practical application in high‐performance lithium‐ion batteries. However, limited loading amount of SiO_x on the surface of graphite and some inherent disadvantages of SiO_x such as huge volume variation and poor electronic conductivity result in unsatisfactory electrochemical performance. Herein, a novel and facile fabrication approach is developed to synthesize high‐performance SiO_x/C composites with graphite‐like structure in which SiO_x particles are dispersed and anchored in the carbon materials by restoring original structure of artificial graphite. The multicomponent carbon materials are favorable for addressing the disadvantages of SiO_x‐based anodes, especially for the formation of stable solid electrolyte interphase, maintaining structural integrity of electrode materials and improving electrical conductivity of electrode. The resultant SiO_x/C anodes demonstrate high reversible capacities (645 mA h g^?1), excellent cycling stability (≈90% capacity retention for 500 cycles), and superior rate capabilities. Even at high pressing density (1.3 g cm^?3), SiO_x/C anodes still present superior cycling performance due to the high tap density and structural integrity of electrode materials. The proposed synthetic method can also be developed to address other anode materials with inferior electronic conductivity and huge volume variation.     

Hybrid Paper–Plastic Microchip for Flexible and High‐Performance Point‐of‐Care Diagnostics

A low‐cost and easy‐to‐fabricate microchip remains a key challenge for the development of true point‐of‐care (POC) diagnostics. Cellulose paper and plastic are thin, light, flexible, and abundant raw materials, which make them excellent substrates for mass production of POC devices. Herein, a hybrid paper–plastic microchip (PPMC) is developed, which can be used for both single and multiplexed detection of different targets, providing flexibility in the design and fabrication of the microchip. The developed PPMC with printed electronics is evaluated for sensitive and reliable detection of a broad range of targets, such as liver and colon cancer protein biomarkers, intact Zika virus, and human papillomavirus nucleic acid amplicons. The presented approach allows a highly specific detection of the tested targets with detection limits as low as 10² ng mL^?1 for protein biomarkers, 10³ particle per milliliter for virus particles, and 10² copies per microliter for a target nucleic acid. This approach can potentially be considered for the development of inexpensive and stable POC microchip diagnostics and is suitable for the detection of a wide range of microbial infections and cancer biomarkers.     

Nitrogen‐Doped Carbon Networks for High Energy Density Supercapacitors Derived from Polyaniline Coated Bacterial Cellulose

Bacterial cellulose (BC) is used as both template and precursor for the synthesis of nitrogen‐doped carbon networks through the carbonization of polyaniline (PANI) coated BC. The as‐obtained carbon networks can act not only as support for obtaining high capacitance electrode materials such as activated carbon (AC) and carbon/MnO₂ hybrid material, but also as conductive networks to integrate active electrode materials. As a result, the as‐assembled AC//carbon‐MnO₂ asymmetric supercapacitor exhibits a considerably high energy density of 63 Wh kg^?1 in 1.0 m Na₂SO₄ aqueous solution, higher than most reported AC//MnO₂ asymmetric supercapacitors. More importantly, this asymmetric supercapacitor also exhibits an excellent cycling performance with 92% specific capacitance retention after 5000 cycles. Those results offer a low‐cost, eco‐friendly design of electrode materials for high‐performance supercapacitors.     

A Low‐Cost,Self‐Standing NiCo2O4@CNT/CNT Multilayer Electrode for Flexible Asymmetric Solid‐State Supercapacitors

The demand for a new generation of flexible, portable, and high‐capacity power sources increases rapidly with the development of advanced wearable electronic devices. Here we report a simple process for large‐scale fabrication of self‐standing composite film electrodes composed of NiCo₂O₄@carbon nanotube (CNT) for supercapacitors. Among all composite electrodes prepared, the one fired in air displays the best electrochemical behavior, achieving a specific capacitance of 1,590 F g^?1 at 0.5 A g^?1 while maintaining excellent stability. The NiCo₂O₄@CNT/CNT film electrodes are fabricated via stacking NiCo₂O₄@CNT and CNT alternately through vacuum filtration. Lightweight, flexible, and self‐standing film electrodes (≈24.3 µm thick) exhibit high volumetric capacitance of 873 F cm^?3 (with an areal mass of 2.5 mg cm^?2) at 0.5 A g^?1. An all‐solid‐state asymmetric supercapacitor consists of a composite film electrode and a treated carbon cloth electrode has not only high energy density (≈27.6 Wh kg^?1) at 0.55 kW kg^?1 (including the weight of the two electrodes) but also excellent cycling stability (retaining ≈95% of the initial capacitance after 5000 cycles), demonstrating the potential for practical application in wearable devices.     

Facile Preparation of High‐Content N‐Doped CNT Microspheres for High‐Performance Lithium Storage

Herein, high‐content N‐doped carbon nanotube (CNT) microspheres (HNCMs) are successfully synthesized through simple spray drying and one‐step pyrolysis. HNCM possesses a hierarchically porous architecture and high‐content N‐doping. In particular, HNCM800 (HNCM pyrolyzed at 800 °C) shows high nitrogen content of 12.43 at%. The porous structure derived from well‐interconnected CNTs not only offers a highly conductive network and blocks diffusion of soluble lithium polysulfides (LiPSs) in physical adsorption, but also allows sufficient sulfur infiltration. The incorporation of N‐rich CNTs provides strong chemical immobilization for LiPSs. As a sulfur host for lithium–sulfur batteries, good rate capability and high cycling stability is achieved for HNCM/S cathodes. Particularly, the HNCM800/S cathode delivers a high capacity of 804 mA h g^?1 at 0.5 C after 1000 cycles corresponding to low fading rate (FR) of only 0.011% per cycle. Remarkably, the cathode with high sulfur loading of 6 mg cm^?2 still maintains high cyclic stability (capacity of 555 mA h g^?1 after 1000 cycles, FR 0.038%). Additionally, CNT/Co₃O₄ microspheres are obtained by the oxidation of CNTs/Co in the air. The as‐prepared CNT/Co₃O₄ microspheres are employed as an anode for lithium‐ion batteries and present excellent cycling performance.     

High‐Performance Ferroelectric–Dielectric Multilayered Thin Films for Energy Storage Capacitors

Herein, the effect of the insertion of a thin dielectric HfO₂:Al₂O₃ (HAO) layer at different positions in the Pt/0.5Ba(Zr_0.2Ti_0.8)O₃–0.5(Ba_0.7Ca_0.3)TiO₃ (BCZT)/Au structure on the energy storage performance of the capacitors is investigated. A high storage performance is achieved through the insertion of a HAO layer between BCZT and Au layers. The insertion of the dielectric layer causes a depolarization field which results in a high linearity hysteresis loop with low energy dissipation. The Pt/BCZT/HAO/Au capacitors show an impressive energy storage density of 99.8 J cm^?3 and efficiency of 71.0%, at an applied electric field of 750 kV cm^?1. Further, no significant change in the energy storage properties is observed after passing 10⁸ switching cycles through the capacitor. The presence of resistive switching (RS) in leakage current characteristics confirms the strong charge coupling between ferroelectric and insulator layers. The same trend of the RS ratio and the energy storage performance with the variation of the architecture of the devices suggests that the energy storage properties can be improved through the charge coupling between the layers. By combining ferroelectrics and dielectrics into one single structure, the proposed strategy provides an efficient way for developing highly efficient energy storage capacitors.     

Fe2O3 Nanoneedles on Ultrafine Nickel Nanotube Arrays as Efficient Anode for High‐Performance Asymmetric Supercapacitors

High performance of electrochemical energy storage devices depends on the smart structure engineering of electrodes, including the tailored nanoarchitectures of current collectors and subtle hybridization of active materials. To improve the anode supercapacitive performance of Fe₂O₃ for high‐voltage asymmetric supercapacitors, here, a hybrid core‐branch nanoarchitecture is proposed by integrating Fe₂O₃ nanoneedles on ultrafine Ni nanotube arrays (NiNTAs@Fe₂O₃ nanoneedles). The fabrication process employs a bottom‐up strategy via a modified template‐assisted method starting from ultrafine ZnO nanorod arrays, ensuring the formation of ultrafine Ni nanotube arrays with ultrathin tube walls. The novel developed NiNTAs@Fe₂O₃ nanoneedle electrode is demonstrated to be a highly capacitive anode (418.7 F g^?1 at 10 mV s^?1), matching well with the similarly built NiNTAs@MnO₂ nanosheet cathode. Contributed by the efficient electron collection paths and short ion diffusion paths in the uniquely designed anode and cathode, the asymmetric supercapacitors exhibit an excellent maximum energy density of 34.1 Wh kg^?1 at the power density of 3197.7 W kg^?1 in aqueous electrolyte and 32.2 Wh kg^?1 at the power density of 3199.5 W kg^?1 in quasi‐solid‐state gel electrolyte.     

High Electroactive Material Loading on a Carbon Nanotube@3D Graphene Aerogel for High‐Performance Flexible All‐Solid‐State Asymmetric Supercapacitors

Freestanding carbon‐based hybrids, specifically carbon nanotube@3D graphene (CNTs@3DG) hybrid, are of great interest in electrochemical energy storage. However, the large holes (about 400 µm) in the commonly used 3D graphene foams (3DGF) constitute as high as 90% of the electrode volume, resulting in a very low loading of electroactive materials that is electrically connected to the carbon, which makes it difficult for flexible supercapacitors to achieve high gravimetric and volumetric energy density. Here, a hierarchically porous carbon hybrid is fabricated by growing 1D CNTs on 3D graphene aerogel (CNTs@3DGA) using a facile one‐step chemical vapor deposition process. In this architecture, the 3DGA with ample interconnected micrometer‐sized pores (about 5 µm) dramatically enhances mass loading of electroactive materials comparing with 3DGF. An optimized all‐solid‐state asymmetric supercapacitor (AASC) based on MnO₂@CNTs@3DGA and Ppy@CNTs@3DGA electrodes exhibits high volumetric energy density of 3.85 mW h cm^?3 and superior long‐term cycle stability with 84.6% retention after 20 000 cycles, which are among the best reported for AASCs with both electrodes made of pseudocapacitive electroactive materials.     

Cactus‐Like NiCoP/NiCo‐OH 3D Architecture with Tunable Composition for High‐Performance Electrochemical Capacitors

To effectively enhance the energy density and overall performance of electrochemical capacitors (ECs), a new strategy is demonstrated to increase both the intrinsic activity of the reaction sites and their density. Herein, nickel cobalt phosphides (NiCoP) with high activity and nickel cobalt hydroxides (NiCo‐OH) with good stability are purposely combined in a hierarchical cactus‐like structure. The hierarchical electrode integrates the advantages of 1D nanospines for effective charge transport, 2D nanoflakes for mechanical stability, and 3D carbon cloth substrate for flexibility. The NiCoP/NiCo‐OH 3D electrode delivers a high specific capacitance of ≈1100 F g^?1, which is around seven times higher than that of bare NiCo‐OH. It also possesses ≈90% capacitance retention after 1000 charge–discharge cycles. An asymmetric supercapacitor composed of NiCoP/NiCo‐OH cathode and metal–organic framework‐derived porous carbon anode achieves a specific capacitance of ≈100 F g^?1, high energy density of ≈34 Wh kg^?1, and excellent cycling stability. The cactus‐like NiCoP/NiCo‐OH 3D electrode presents a great potential for ECs and is promising for other functional applications such as catalysts and batteries.     

Mesoporous NiCo2O4 Nanowire Arrays Grown on Carbon Textiles as Binder‐Free Flexible Electrodes for Energy Storage

Binary metal oxides has been regarded as a promising class of electrode materials for high‐performance energy storage devices since it offers higher electrochemical activity and higher capacity than mono‐metal oxide. Besides, rational design of electrode architectures is an effective solution to further enhance electrochemical performance of energy storage devices. Here, the advanced electrode architectures consisting of carbon textiles uniformally covered by mesoporous NiCo₂O₄ nanowire arrays (NWAs) are successfully fabricated by a simple surfactant‐assisted hydrothermal method combined with a short post annealing treatment, which can be directly applied as self‐supported electrodes for energy storage devices, such as Li‐ion batteries, supercapacitors. The as‐prepared mesoporous NiCo₂O₄ nanowires consist of numerous highly crystalline nanoparticles, leaving a large number of mesopores to alleviate the volume change during the charge/discharge process. Electrode architectures presented here promise fast electron transport by direct connection to the growth substrate and facile ion diffusion path provided by both the abundant mesoporous structure in nanowires and large open spaces between neighboring nanowires, which ensures every nanowire participates in the ultrafast electrochemical reaction. Benefiting from the intrinsic materials and architectures features, the unique binder‐free NiCo₂O₄/carbon textiles exhibit high specific capacity/capacitance, excellent rate capability, and cycling stability.     

Fabrication of Highly Flexible,Scalable, and High‐Performance Supercapacitors Using Polyaniline/Reduced Graphene Oxide Film with Enhanced Electrical Conductivity and Crystallinity

With developments in technology, tremendous effort has been devoted to produce flexible, scalable, and high‐performance supercapacitor electrode materials. This report presents a novel fabrication method of highly flexible and scalable electrode material for high‐performance supercapacitors using solution‐processed polyaniline (PANI)/reduced graphene oxide (RGO) hybrid film. SEM, TEM, Raman, and XPS analyses show that the PANI/RGO film is successfully synthesized. The percentages of the PANI component in the film are controlled (88, 76, and 60%), and the maximum electrical conductivity (906 S cm^?1) is observed at the PANI percentage of 76%. Notably, electrical conductivity of the PANI/RGO film (906 S cm^?1) is larger than both PANI (580 S cm^?1) and RGO (46.5 S cm^?1) components. XRD analysis demonstrates that the strong π–π interaction between the RGO and the PANI cause more compact packing of the PANI chains by inducing more fully expanded conformation of the PANI chains in the solution, leading to increase in the electrical conductivity and crystallinity of the film. The PANI/RGO film also displays diverse advantages as a scalable and flexible electrode material (e.g., controllable size and great flexibility). During the electrochemical tests, the film exhibits high capacitance of 431 F g^?1 with enhanced cycling stability.     

General Method for Large‐Area Films of Carbon Nanomaterials and Application of a Self‐Assembled Carbon Nanotube Film as a High‐Performance Electrode Material for an All‐Solid‐State Supercapacitor

Rational assembly of carbon nanostructures into large‐area films is a key step to realize their applications in ubiquitous electronics and energy devices. Here, a self‐assembly methodology is devised to organize diverse carbon nanostructures (nanotubes, dots, microspheres, etc.) into homogeneous films with potentially infinite lateral dimensions. On the basis of studies of the redox reactions in the systems and the structures of films, the spontaneous deposition of carbon nanostructures onto the surface of the copper substrate is found to be driven by the electrical double layer between copper and solution. As a notable example, the as‐assembled multiwalled carbon nanotube (MWCNT) films display exceptional properties. They are a promising material for flexible electronics with superior electrical and mechanical compliance characteristics. Finally, two kinds of all‐solid‐state supercapacitors based on the self‐assembled MWCNT films are fabricated. The supercapacitor using carbon cloth as the current collector delivers an energy density of 3.5 Wh kg^?1 and a power density of 28.1 kW kg^?1, which are comparable with the state‐of‐the‐art supercapacitors fabricated by the costly single‐walled carbon nanotubes and arrays. The supercapacitor free of foreign current collector is ultrathin and shows impressive volumetric energy density (0.58 mWh cm^?3) and power density (0.39 W cm^?3) too.     

Radially Aligned Porous Carbon Nanotube Arrays on Carbon Fibers: A Hierarchical 3D Carbon Nanostructure for High‐Performance Capacitive Energy Storage

A novel and scalable synthesis approach to produce hierarchically aligned porous carbon nanotube arrays (PCNTAs) on flexible carbon fibers (CFs) is developed. The PCNTAs are obtained by catalytic conversion of ethanol on ZnO nanorod arrays and then reduction‐evaporation of ZnO nanorods, resulting in uniform and controllable wall thicknesses of the final PCNTAs. The 3D arrangement, the diameters, and the lengths of the PCNTAs can be tuned by adjusting the synthesis protocols of the ZnO nanorod arrays. The PCNTAs@CFs exhibit a high specific capacitance of 182 F g^?1 at 40 A g^?1 (188 F g^?1 at 20 A g^?1) in 6 m KOH. The symmetric supercapacitor shows an excellent cycling stability with only 0.0016% loss per cycle after 10 000 continuous cycles at the current density of 12 A g^?1. These excellent electrochemical performances are ascribed to the unique structural design of hierarchical PCNTAs, which provide not only appropriate channels for enhanced electronic and ionic transport but also increased surface area for accessing more electrolyte ions. The structural design and the synthesis approach are general and can be extended to synthesizing a broad range of materials systems.     

Design of Hierarchical NiCo@NiCo Layered Double Hydroxide Core–Shell Structured Nanotube Array for High‐Performance Flexible All‐Solid‐State Battery‐Type Supercapacitors

A novel hierarchical nanotube array (NTA) with a massive layered top and discretely separated nanotubes in a core–shell structure, that is, nickel–cobalt metallic core and nickel–cobalt layered double hydroxide shell (Ni?Co@Ni?Co LDH), is grown on carbon fiber cloth (CFC) by template‐assisted electrodeposition for high‐performance supercapacitor application. The synthesized Ni?Co@Ni?Co LDH NTAs/CFC shows high capacitance of 2200 F g^?1 at a current density of 5 A g^?1, while 98.8% of its initial capacitance is retained after 5000 cycles. When the current density is increased from 1 to 20 A g^?1, the capacitance loss is less than 20%, demonstrating excellent rate capability. A highly flexible all‐solid‐state battery‐type supercapacitor is successfully fabricated with Ni?Co LDH NTAs/CFC as the positive electrode and electrospun carbon fibers/CFC as the negative electrode, showing a maximum specific capacitance of 319 F g^?1, a high energy density of 100 W h kg^?1 at 1.5 kW kg^?1, and good cycling stability (98.6% after 3000 cycles). These fascinating electrochemical properties are resulted from the novel structure of electrode materials and synergistic contributions from the two electrodes, showing great potential for energy storage applications.     

Integrated Thin Film Battery Design for Flexible Lithium Ion Storage: Optimizing the Compatibility of the Current Collector‐Free Electrodes

The design of flexible full‐cell configuration relies on the light‐weight arrangement, structural robustness, compositional compatibility, and shape conformability of the coherent components. In this article, a general and scalable spin‐coating approach is developed to integrate the flexible, current‐collector‐free cathode and anode in the thin film batteries with the layer‐stacked configuration. The design of the ternary composite anode involves the reduced graphene oxide encapsulation of the MoS₂/N‐doped carbon microrods composite (rGO‐MoS₂/NC) via the facile hydrothermal‐calcination process. In the similar structure design of the cathode, the ball‐milled nanocrystalline mixture of LiMn₂O₄ and LiVPO₄F is wrapped within the GO interfacial protection layer. Furthermore, the slurries of electroactive materials with the predetermined areal capacity ratio of negative to positive electrodes (N/P ratio) are cast onto both sides of the nano‐SiO₂ modified polyethylene (SiO₂‐MPE) separator via the facile spin‐coating process. The prototype full‐cell configuration delivers a high reversible capacity, satisfactory capacity retention at the high rate, as well as good cyclability under different mechanical loadings. This integrated thin film battery model showcases its potential use in the flexible electronic devices.     

Achieving of Flexible,Free‐Standing,Ultracompact Delaminated Titanium Carbide Films for High Volumetric Performance and Heat‐Resistant Symmetric Supercapacitors

The volumetric performance of supercapacitors (SCs), besides the gravimetric performance, is attracting an increasing attention due to the fast development of electric vehicles and smart devices. Here, a unique design of symmetric supercapacitor material is reported with a tight face‐to‐face architecture by applying a high pressure to the delaminated Ti₃C₂ (d‐Ti₃C₂) films. The high pressure makes the d‐Ti₃C₂ films achieve an increased density, high electron conductivity, good wettability, and abundant interconnected mesopore channels to promote ion transport efficiently, that is, more cations can intercalate/deintercalate in the charging–discharging process. As a result, with the increase of the applying pressure, the d‐Ti₃C₂ film pressured at 40 MPa in 1 m Li₂SO₄ exhibits an ultrahigh capacitance of over 633 F cm^?3, outstanding energy density, and cyclic stability. Especially, the corresponding SC in 1 m 1‐ethyl‐3‐methylimidazolium tetrafluoroborate/acetonitrile organic electrolyte shows a high volumetric energy density of 41 Wh L^?1, which is the highest value reported for the SCs based on MXene materials in organic electrolytes. The outstanding volumetric electrochemical performance and thermal stability of the SCs based on the ultracompact d‐Ti₃C₂ film demonstrate their promising potential as forceful power sources for small electronic devices.     

Tailoring Rod‐Like FeSe2 Coated with Nitrogen‐Doped Carbon for High‐Performance Sodium Storage

Designing potential anodes for sodium‐ion battery with both remarkable durability and high‐rate capability has captured enormous attention so far. The engineering of size and morphology is deemed as an effective manner to boost the electrochemical properties. Owing to the anisotropic self‐assembly of iron selenide, rod‐like FeSe₂ coates with nitrogen‐doped carbon is prepared through the thermal reaction of Prussian blue with selenium. Notably, the cyano groups are effectively transformed into N‐doped carbon with Fe? N? C bonds, which uniformly coats FeSe₂, prompting Na⁺ transportations. Interestingly, the particle size is tailored by heating rates, along with increased carbon content, leading to broadened energy levels for redox reaction. Bestowed by these advantages, the FeSe₂/N‐C as Na‐storage anode delivers impressive electrochemical properties. Even at a rather high rate of 10.0 A g^?1, a considerable capacity of 308 mAh g^?1 is yielded over 10 000 loops. Supported by the detailed analysis of kinetic features, reduced size of particles could bring about the enhanced contributions of pseudocapacitive and quickening rate of ions transferring. The phase evolutions are further investigated by in situ EIS and ex‐situ technologies. The work is expected to provide a new strategy to prepare metal‐selenide with controllable size and induce the faster kinetic of high‐rate materials.     

Monodisperse Metallic NiCoSe2 Hollow Sub‐Microspheres: Formation Process,Intrinsic Charge‐Storage Mechanism,and Appealing Pseudocapacitance as Highly Conductive Electrode for Electrochemical Supercapacitors

Highly conductive metal selenides are gaining prominence as promising electrode materials in electrochemical energy‐storage fields. However, phase‐pure bimetallic selenides are scarcely retrieved, and their underlying charge‐storage mechanisms are still far from clear. Here, first a solvothermal strategy is devised to purposefully fabricate monodisperse hollow NiCoSe₂ (H‐NiCoSe₂) sub‐microspheres. Inherent formation of metallic H‐NiCoSe₂ is tentatively put forward with comparative structure‐evolution investigations. Interestingly, the fresh H‐NiCoSe₂ does not demonstrate striking supercapacitive behaviors when evaluated for electrochemical supercapacitors (ESs). But it exhibits competitive pseudocapacitance of ≈750 F g^?1 at a rate of 3 A g^?1 with a high loading of 7 mg cm^?2 after ≈100 cyclic voltammetry (CV) cycles. With systematic physicochemical/electrochemical analyses, intrinsic energy‐storage mechanism of the H‐NiCoSe₂ is convincingly revealed that the electrooxidation‐generated biactive CoOOH/NiOOH phases in aqueous KOH over CV scanning, rather than the H‐NiCoSe₂ itself, account for the remarkable pesudocapacitance observed after cycling. An assembled H‐NiCoSe₂‐based asymmetric device has delivered an energy density of ≈25.5 Wh kg^?1 with a power rate of ≈3.75 kW kg^?1, and long‐span cycle life. More significantly, the electrode design and new perspectives here hold profound promise in enriching material synthesis methodologies and in‐depth understanding of the complex charge‐storage process of newly emerging pseudocapacitive materials for next‐generation ESs.     

MS2 (M = Co and Ni) Hollow Spheres with Tunable Interiors for High‐Performance Supercapacitors and Photovoltaics

We demonstrate in this paper facile synthesis of CoS₂ and NiS₂ hollow spheres with various interiors through a solution‐based route. The obtained CoS₂ microspheres constructed by nanosheets display a three‐dimensional architecture with solid, yolk‐shell, double‐shell, and hollow interiors respectively, with continuous changes in specific surface areas and pore‐size distributions. Especially, the CoS₂ hollow spheres demonstrate excellent supercapacitive performance including high specific capacitance, good charge/discharge stability and long‐term cycling life, owing to the greatly improved faradaic redox reaction and mass transfer. Furthermore, CoS₂ hollow spheres exhibit superior electrocatalytic activity for disulfide/thiolate (T₂/T^?) redox electrolyte in dye‐sensitized solar cells (DSCs). Therefore, this work provides a promising approach for the design and synthesis of structure tunable materials with largely enhanced supercapacitor behavior, which can be potentially applied in energy storage devices.