2D/2D SnS2/MoS2 layered heterojunction for enhanced supercapacitor performance

Two-dimensional (2D) SnS₂/MoS₂ heterojunction with a 2D/2D novel structure was used as electrode material for enhanced supercapacitor performance. Compared with the sole SnS₂, the as-prepared 2D/2D SnS₂/MoS₂ layered heterojunction has exhibited great improvement in supercapacitor properties. This novel structure can effectively prevent agglomeration and stacking in electrochemical process, and 2D/2D structure is beneficial to intercalation and desorption of ions in electrochemical processes. The experiment result shows that MoSn₅ (samples with 5% MoSn5 mole ratios) display a specific capacitance of 466.6 F/g at the current density of 1 A/g in 0.5 mol/L potassium hydroxide solution, an impressive cycling stability with 88.2% capacitance retention at current density of 4 A/g. In addition, the as-fabricated symmetric supercapacitor exhibited high energy density of 115 Wh kg⁻¹ at the power density of 2230 Wh kg⁻¹. This work provides a fundamental investigation of 2D/2D layered material synergistic effect on the electrochemical process.     

Enhancing the performance and stability of NiCo2O4 nanoneedle coated on Ni foam electrodes with Ni seed layer for supercapacitor applications

We introduce a facile way to improve the performance of NiCo₂O₄ electrode by including a Ni seed layer. The seed layer deposited on Ni foam electrode (NiCo₂O₄/Ni@NF) shows the superior specific capacity of 1142 C g⁻¹ at 1 A g⁻¹ with the excellent cycle stability of ∼96% even after 5000 cycles at a higher current density of 5 A g⁻¹. These values are about 3.7 times higher than that of the electrode (NiCo₂O₄@NF) without a seed layer, which shows the specific capacity of 305 C g⁻¹@1 A g⁻¹ with cycle stability of 84% even at a lower current density of 1 A g⁻¹. The enhanced performance of the NiCo₂O₄/Ni@NF electrode may be attributed to lower interface resistance, fast redox reversible reaction, and improved surface active sites. Further, the asymmetric solid-state supercapacitor device is fabricated by using the NiCo₂O₄/Ni@NF electrode as a positive and reduced graphene oxide (rGO)-Fe₂O₃ nanograin as a negative electrode with PVA-KOH gel electrolyte, and the NiCo₂O₄/Ni20@NF//rGO-Fe₂O₃@NF asymmetric solid state device delivers an areal capacitance of 446 mF cm⁻² with a low capacitance loss of 18% even after 10000 cycles. Further, the fabricated asymmetric solid state device shows a maximum energy density of 124.3 Wh cm⁻² (at 3.58 kW cm⁻²) and power density of 14.88 kW cm⁻² (at 31.41 Wh cm⁻²).     

Synthesis of 3D nanoflower-like mesoporous NiCo2O4 N-doped CNTs nanocomposite for solid-state hybrid supercapacitor; efficient material for the positive electrode

In this research work, we report a novel method for developing ternary NiCo₂O₄ compounds using deep eutectic solvents (DESs) and a strategy for improving their pseudocapacitive performance. NiCo₂O₄ composites with N-doped carbon nanotubes (NCNTs) were fabricated on Ni foam using a hydrothermal method. The electrochemical performance of the NiCo₂O₄ was altered with the change in the reaction temperature. The composite of NiCo₂O₄ and NCNTs demonstrated a maximum value of specific capacity of 303 mAh g⁻¹ at a scan rate of 5 mV s⁻¹. The specific capacity for the composite compound was 1.3-fold greater than that of the pristine NiCo₂O₄ sample. For practical applications, we constructed a flexible solid-state hybrid supercapacitor comprised of NiCo₂O₄/NCNTs//activated carbon (AC) cells with an excellent energy density of 12.31 Wh kg⁻¹, outstanding power density of 8.96 kW kg⁻¹, and tremendous electrode stability. The three-dimensional mesoporous nanoflowers and nanotubes-like nanostructures of NiCo₂O₄ are well-suited for use in hybrid devices as well as convenient for flexible electronic devices.     

An asymmetric supercapacitor using RuO2/TiO2 nanotube composite and activated carbon electrodes

We reported an asymmetric supercapacitor technology where RuO₂/TiO₂ nanotube composite was used as positive electrode and the activated carbon as negative electrode in 1 mol/L KOH electrolyte solution. The electrochemical capacitance performance of the asymmetric supercapacitor was tested by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge-discharge tests. The results show that the asymmetric supercapacitor has electrochemical capacitance performance within potential range 0–1.4 V. A power density 1207 W/kg was obtained with an energy density of 5.7 W h/kg at a charge–discharge current density of 120 mA/cm². The supercapacitor also exhibits a good cycling performance and keep 90% of initial capacity over 1000 cycles.     

氧化镍/碳纳米管构筑准固态不对称超级电容器及电化学性能

以Ni(NO₃)₂为原料、NaOH为沉淀剂和羟基化碳纳米管（CNT）为基质首先制备了Ni(OH)₂/CNT复合材料, 然后将其于一定温度下煅烧,使其转变为NiO/CNT复合材料。用X射线粉末衍射仪（XRD）、场发射电子显微镜（FESEM）和透射电子显微镜（TEM）表征了样品的晶相与形貌,结果表明NiO纳米粒子紧密锚附在碳纳米管表面。复合材料可能的形成机理被提出。采用循环伏安法（CV）、单电极充放电和电化学阻抗研究了反应条件对其电化学性能的影响,确定最佳制备条件。将复合材料正极、活性炭负极和PVA-KOH电解质膜组装成准固态不对称超级电容器,电化学性能测试结果表明,在充放电电流密度11.2mA/cm²下,其比电容达到868.0F/g并保持稳定循环3700圈。7500次循环后,其比电容值仍有564.2F/g,显示出高的比电容和长的循环稳定性。     

High performance of a solid-state flexible asymmetric supercapacitor based on graphene films

Solid-state flexible energy storage devices hold the key to realizing portable and flexible electronic devices. Achieving fully flexible energy storage devices requires that all of the essential components (i.e., electrodes, separator, and electrolyte) with specific electrochemical and interfacial properties are integrated into a single solid-state and mechanically flexible unit. In this study, we describe the fabrication of solid-state flexible asymmetric supercapacitors based on an ionic liquid functionalized-chemically modified graphene (IL-CMG) film (as the negative electrode) and a hydrous RuO(2)-IL-CMG composite film (as the positive electrode), separated with polyvinyl alcohol-H(2)SO(4) electrolyte. The highly ordered macroscopic layer structures of these films arising through direct flow self-assembly make them simultaneously excellent electrical conductors and mechanical supports, allowing them to serve as flexible electrodes and current collectors in supercapacitor devices. Our asymmetric supercapacitors have been optimized with a maximum cell voltage up to 1.8 V and deliver a high energy density (19.7 W h kg(-1)) and power density (6.8 kW g(-1)), higher than those of symmetric supercapacitors based on IL-CMG films. They can operate even under an extremely high rate of 10 A g(-1) with 79.4% retention of specific capacitance. Their superior flexibility and cycling stability are evident in their good performance stability over 2000 cycles under harsh mechanical conditions including twisted and bent states. These solid-state flexible asymmetric supercapacitors with their simple cell configuration could offer new design and fabrication opportunities for flexible energy storage devices that can combine high energy and power densities, high rate capability, and long-term cycling stability.     

V2O5 nanosheets assembled on 3D carbon fiber felt as a free-standing electrode for flexible asymmetric supercapacitor with remarkable energy density

As an emerging energy storage device, supercapacitor is widely investigated owing to its excellent capability, quick charge-discharge and tremendous cycle life. The operation potential window, energy density and mass loading of supercapacitor must be taken into deep consideration for its practical application. In this work, an outstanding electrode based on CFF@V₂O₅ nanosheets was prepared. Then a free-standing asymmetric supercapacitor with CFF@V₂O₅ composite as positive electrode and CFF@AC as negative electrode was assembled. Owing to the functional groups produced on CFF after the activation, V₂O₅ nanosheets was immobilized. The composite exhibits remarkable specific capabilities of 1465 mF cm^?2 (492 F g^?1). The energy density of the assembled free-standing asymmetric supercapacitor achieves 0.928 mWh cm^?3 when the power density is 17.5 mW cm^?3. After 6000 charging-discharging cycles as under normal, bended and anti-bended conditions for respective 2000 cycles, the device retains 89.7% of the initial capacitance, exhibiting fascinating cycle stabilization. Finally, two devices linked series can lighten a LED of 1.8 V for 2 min after charging for 2.5 min, which is inspiring for the practical application and production of self-supporting asymmetric supercapacitors.     

High performance fiber-shaped flexible asymmetric supercapacitor based on MnO2 nanostructure composited with CuO nanowires and carbon nanotubes

The demand for wearable electronics has greatly promoted the development of flexible supercapacitors. Herein, we develop a series of approaches to fabricate a fiber-shaped supercapacitor with flexibility. In the device, CuO@MnO₂, carbon nanotube (CNT)@MnO₂ and PVA-KOH are respectively used as inner electrode, outer electrode and gel electrolyte. The approaches including in-situ growth of CNTs, in-situ etching removal of SiO₂ template and in-situ filling of gel electrolyte via hydrothermal process are explored to protect the device from structure damage caused by external forces and to maximize effective contact areas between active electrode materials and gel electrolyte. The optimized supercapacitor of copper wire@CuO@MnO₂//PVA-KOH//CNT@MnO₂ demonstrates a good capacitive performance (5.97 F cm^?3) and exhibits a high energy density (0.38 mWh cm^?3) at a power density of 25.5 mW cm^?3. In addition, it has perfect cycling stability (77% after 2000 cycles) with excellent flexibility. Therefore, this work will provide desirable processes to construct fiber-shaped supercapacitors as flexible and wearable energy storage devices.     

超级电容器用二维Ti3C2Tx过渡金属碳/氮化物材料的研究进展

近年来二维过渡金属碳/氮化物(MXene)材料由于其独特的物理/化学性能,在储能领域引起广泛的关注。其中以二维Ti3C2Tx材料的研究最为普遍。MAX相是一类三元氮化物和/或碳化物,其化学式为Mn+1AXn (n=1~3),M代表过渡金属元素(如Sc, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo等),X是碳和/或氮,A主要是IIIA或IVA族元素。根据n不同,MAX相的晶体结构包括3种类型。MAX相中,M?X和M?A键强度都很高。无法通过剪切或其它机械方法分层剥离。由于M?A键比M?X键具有更高的化学活性,可以通过化学刻蚀M?A键并辅助剥离方法获得单层/少层的MXenes材料。表面基团随机分布,对电化学性能有重要的影响。调控表面基团的种类和数量是当前研究的重要内容。本工作介绍了MXene相的基本结构,分析了相结构与性能的关系。总结了通过离子插入、热处理、表面改性、电极设计和元素掺杂等手段改善MXene相材料电化学性能的研究进展,简要介绍了MXenes与碳材料、氧化物、聚合物复合在超级电容器领域中的应用进展。对MXene相材料的结构、制备及电化学性能等方面进行了综述,指出了MXene相材料用于超级电容器领域存在的主要问题及未来的发展方向。     

One-pot hydrothermal synthesis of Mn3O4 nanorods grown on Ni foam for high performance supercapacitor applications

Mn₃O₄/Ni foam composites were synthesized by a one-step hydrothermal method in an aqueous solution containing only Mn(NO₃)₂ and C₆H₁₂N₄. It was found that Mn₃O₄ nanorods with lengths of 2 to 3 μm and diameters of 100 nm distributed on Ni foam homogeneously. Detailed reaction time-dependent morphological and component evolution was studied to understand the growth process of Mn₃O₄ nanorods. As cathode material for supercapacitors, Mn₃O₄ nanorods/composite exhibited superior supercapacitor performances with high specific capacitance (263 F · g^-1 at 1A · g^-1), which was more than 10 times higher than that of the Mn₃O₄/Ni plate. The enhanced supercapacitor performance was due to the porous architecture of the Ni foam which provides fast ion and electron transfer, large reaction surface area, and good conductivity.     

Bi2O3 induced tremella-like Bi2WO6 with visible light catalytic performance

The development of single phase photocatalyst is expected to realize clean energy and pollution treatment. Herein, we reported a novel Tremella-like Bi₂WO₆ catalyst which was obtained by facile hydrothermal technique. The formation of Tremella-like Bi₂WO₆ strongly depended on introduction of Bi₂O₃. Based on the Kirkendall effect, Bi₂O₃ induced Bi(NO₃)₃·5H₂O to form biscuit-like Bi₆O₆(OH)₃(NO₃)₃·3H₂O particles which provided templates and reacted simultaneously with WO₄^2? to synthesize Tremella-like Bi₂WO₆. The Tremella-like Bi₂WO₆ exhibited remarkable visible-light catalytic performance. The degradation rate of RhB dye reached 100% with 10 min, the reduction rate of CO₂ was 5.5 times higher than pure Bi₂WO₆. Moreover, the Tremella-like Bi₂WO₆ catalyst displayed excellent stability during the recycle experiments. The high catalytic activity makes single phase Bi₂WO₆ catalyst great potential in environmental protection field.     

High power aqueous hybrid asymmetric supercapacitor based on zero-dimensional ZnS nanoparticles with two-dimensional nanoflakes CuSe2 nanostructures

Energy storage materials, particularly chalcogenides, are fascinating electrode materials for supercapacitors (SCs) because of their high capacitance, remarkable electrical conductivity, and multiple oxidation states contributed by numerous metal cations. Herein, a novel nanocomposite based on zinc sulfide and copper diselenide, denoted as (ZnS–CuSe₂), was prepared via a sonochemical-assisted method. The structural analysis revealed the cubic structure for pure ZnS, orthorhombic for CuSe_2, and co-existing cubic and orthorhombic phases for ZnS–CuSe₂ nanocomposites with high purity and crystallinity. The ZnS–CuSe₂ nanocomposite offered exceptional electrochemical performance with redox peaks from the CV analysis, and coupled with plateaus in the charge/discharge profile, confirming the faradaic energy storage properties with functional reversibility. Similarly, a high conductive feature of the ZnS–CuSe₂ composite was revealed by impedance study, with a minor charge transfer resistance than their bulk materials. A hybrid asymmetric supercapacitor (HASCs) composed of ZnS–CuSe₂//AC was constructed, which manifested an enlarged voltage window up to 1.7 V with capacitance of 95 F g⁻¹ and a maximum specific energy of 38 Wh kg⁻¹. Also, high power delivery was attained at 3927 Wkg^-1 when specific energy goes down to 12 Wh kg⁻ at 5 A g⁻¹. Interestingly, only 81.8% retention was left beneath when cycled to 8000 cycles, specifying decent stability of the ZnS–CuSe₂//AC HASCs.     

Ti3C2Tx aerogel with 1D unidirectional channels for high mass loading supercapacitor electrodes

As one of the typical MXenes materials, 2D Ti₃C₂T_x has attracted extensive attention in the field of energy storage. However, due to the restacking problem of Ti₃C₂T_x nanosheets, the electrochemical performance of Ti₃C₂T_x is unsatisfactory. In this paper, a scheme is proposed to obtain 3D aerogel with 1D channels by directional freeze drying of Ti₃C₂T_x. With the help of the unidirectional channels, the 3D Ti₃C₂T_x/Sodium alginate (SA) aerogel can effectively solve the stacking problem of Ti₃C₂T_x nanosheets, and it also accelerates the diffusion of ions. The Ti₃C₂T_x/SA-5 electrode can still reach the mass capacitance of 284.5 F g^?1 and the areal capacitance of 4030.4 mF cm^?2 at 2 mV s^?1 when the loading is 14.2 mg cm^?2 in 1 M H₂SO₄ electrolyte. In addition, the electrode showed good cycling performance without capacitor degradation after 20,000 cycles at 50 mV s^?1. These results suggest that by using the strategy of building special 3D structure of 2D MXene with 1D unidirectional channels, high performance supercapacitor electrodes with high mass loading can be realized.     

Manganese dioxide nanosheets decorated on MXene (Ti3C2Tx) with enhanced performance for asymmetric supercapacitors

The incorporation of nanosized pseudocapacitive materials and structure design are general strategies to enhance the electrochemical performance of MXene-based materials. Herein, the decoration of manganese dioxide (MnO₂) nanosheets on MXene (Ti₃C₂T_x) surfaces was prepared by a facile liquid phase coprecipitation method. Ti₃C₂T_x is initially modified by polydopamine (PDA) coating to ensure the homogeneous distribution of MnO₂ nanosheets and tight and close connections between MnO₂ and the Ti₃C₂T_x backbone. Due to the obtained three-dimensional (3D) nanostructure, facilitating electron transport within the electrode and promoting electrolyte ion accessibility, the δ-MnO₂@Ti₃C₂T_x-0.06 electrode yields superior electrochemical performances, such as a rather large areal capacity of 1233.1 mF cm^?2 and high specific capacitance of 337.6 F g^?1 at 2 mV s^?1, as well as high cyclic stability for 10000 cycles. Furthermore, δ-MnO₂@Ti₃C₂T_x-0.06 composites are employed as positive electrodes, and activated carbon (AC) materials act as negative electrodes with an aqueous electrolyte of 1 M Na₂SO₄ to assemble asymmetric supercapacitors. The prototype device is reversible at cell voltages from 0 to 1.8 V, and manifests a maximum energy density of 31.4 Wh kg^?1 and a maximum power density of 2700 W kg^?1. These encouraging results show enormous possibilities for energy storage applications.     

Anode electrodeposition of 3D mesoporous Fe2O3 nanosheets on carbon fabric for flexible solid-state asymmetric supercapacitor

Novel nanostructured Fe₂O₃ with a network of 3D mesoporous nanosheets was synthesized by depositing on carbon fabric (Fe₂O₃@CF) for use as an anode using a potentially low-cost electrodeposition technique. The electrode with freestanding binder-free Fe₂O₃@CF of high surface area displayed an exceptional specific capacitance of 394.2?F?g^?1. Moreover, a flexible solid-state asymmetric supercapacitor (ASC) was fabricated with a negative electrode based on Fe₂O₃@CF and a positive electrode based on MnO₂@CF in the presence of PVA-LiCl as gel electrolyte. The above ASC exhibited a high operating potential up to 1.8?V, a favorable specific capacitance of 93.5?F?g^?1 (2.92?F?cm^?3), long-term stability (91.3% retention of initial value over 5000 cycles), and remarkable mechanical stability and flexibility, suggesting its potential application for wearable electronics.     

碳酸钾活化一步法制备高比表活性炭及其电容性能的研究

以废弃烟叶为碳源、碳酸钾为活化剂一步法制得烟草基多孔碳。采用扫描电子显微镜（SEM）、X射线衍射（XRD）、N₂吸附-脱附分析（BET）和拉曼光谱（Raman）等手段对多孔材料进行表征。结果表明,材料表面含有醚基、羧基等杂原子基团,具有丰富的孔道结构,比表面积高达2 058 m²/g。三电极体系中的电化学性能结果表明,当碳酸钾与废弃烟叶质量比为3∶1时具有最佳储电性能,其在1 A/g电流下比容量可达337 F/g;10 A/g时循环充放电2 000次,材料的容量保持率为97.3%,具有良好的倍率性能和循环稳定性。     

A green and high energy density asymmetric supercapacitor based on ultrathin MnO2 nanostructures and functional mesoporous carbon nanotube electrodes

A green asymmetric supercapacitor with high energy density has been developed using birnessite-type ultrathin porous MnO(2) nanoflowers (UBMNFs) as positive electrode and functional mesoporous carbon nanotubes (FMCNTs) as negative electrode in 1 M Na(2)SO(4) electrolyte. Both of the electrode materials possess excellent electrochemical performances, with high surface areas and narrow pore size distributions. More significantly, the assembled asymmetric supercapacitor with optimal mass ratio can be cycled reversibly in the high-potential range of 0-2.0 V and exhibits an excellent energy density as high as 47.4 W h kg(-1), which is much higher than those of symmetric supercapacitors based on UBMNFs//UBMNFs and FMCNTs//FMCNTs supercapacitors. Furthermore, our asymmetric supercapacitor (ASC) device also exhibits a superior cycling stability with 90% retention of the initial specific capacitance after 1000 cycles and stable Coulombic efficiency of ~98%. These intriguing results exhibit great potential in developing high energy density "green supercapacitors" for practical applications.     

A phase inversion based sponge-like polysulfonamide/SiO2 composite separator for high performance lithium-ion batteries

In this work,a sponge-like polysulfonamide(PSA)/SiO_2 composite membrane is unprecedentedly prepared by the phase inversion method,and successfully demonstrated as a novel separator of lithium-ion batteries(LIBs).Compared to the commercial polypropylene(PP) separator,the sponge-like PSA/SiO_2 composite possesses better physical and electrochemical properties,such as higher porosity,ionic conductivity,thermal stability and flame retarding ability.The LiCoO_2/Li half-cells using the sponge-like composite separator demonstrate superior rate capability and cyclability over those using the commercial PP separator.Moreover,the sponge-like composite separator can ensure the normal operation of LiCoO_2/Li half-cell at an extremely high temperature of 90 °C,while the commercial PP separator cannot.All these encouraging results suggest that this phase inversion based sponge-like PSA/SiO_2 composite separator is really a promising separator for high performance LIBs.     

High performance water-borne paints with high volume solids based on bimodal latexes

The performance of water-borne paints formulated with five different high solids content acrylic (MMA/BA/MAA) latexes was investigated. These latexes had different particle size distributions (unimodal at 61 wt% and bimodal with the large mode below or above 350 nm at 65 wt% solids), different types of surfactant and in one case the carboxylic monomer was omitted.     

Enhanced electrochemical performance of hybrid composite microstructure of CuCo2O4 microflowers-NiO nanosheets on 3D Ni foam as positive electrode for stable hybrid supercapacitors

Self-assembled composite porous structures comprising CuCo₂O₄ microflowers and NiO hexagonal nanosheets were synthesized on a conducting 3D Ni foam surface [CCO/NO] using a simple hydrothermal method. This unique composite assembly was further characterized and electrochemically evaluated as a binder-free positive electrode for hybrid supercapacitor application. The study showed that the CCO/NO exhibited a maximum areal capacitance of 1444 mF cm^?2, significantly higher than the parent CuCo₂O₄ and NiO electrodes, with remarkable stability of 88.5% for 10,000 galvanostatic charge-discharge cycles. Key features for the enhanced electrochemical performance of CCO/NO can be related to a lowered diffusion resistance because the hybrid nanocomposite porous assembly generates short diffusion paths for electrolyte ions and more active sites for reversible faradaic transition for charge storage. The hybrid supercapacitor was assembled using activated carbon as a negative electrode and CCO/NO as a positive electrode in alkaline electrolyte, performed at an improved potential of 1.6 V. Device showed a maximum areal capacitance of 122 mF cm^?2, a maximum areal energy density of 43 μWh cm^?2, and a maximum areal power density of 5.1 mW cm^?2. This hybrid supercapacitor showed remarkable cyclic stability up to 98% for 10,000 cycles. This study encourages the development of low-cost, high-performance, durable electrode designs using hybrid composite for next-generation energy storage systems.