超级电容器Mn-Pb纳米复合电极材料的电化学性能研究

利用低温固相反应法制备了Mn-Pb复合氧化物超级电容器电极材料.采用XRD、TEM、循环伏安和恒流充放电法对电极材料的形貌和结构特点以及电化学性能进行了测试分析.结果表明,复合氧化物的粒径均为纳米尺寸,呈无定型结构.复合氧化物在1mol/L Na2SO4中,电位窗口为-0.2～0.9(V vs.SCE)范围内具有典型的电容特征.纳米氧化物电极比容量随放电电流的增大而减小.当放电电流为2mA时,Mn-Pb复合氧化物电极的比容量为180.5F/g.     

A nanostructured electrode of IrOx foil on the carbon nanotubes for supercapacitors

IrO(x) nanofoils (IrO(x)NF) of high surface area are sputtered on multi-wall carbon nanotubes (CNT) in the preparation of a structured electrode on a stainless steel (SUS) substrate for supercapacitor applications. This IrO(x)/CNT/SUS electrode is featured with intriguing IrO(x) curved foils of 2-3 nm in thickness and 400-500 nm in height, grown on top of the vertically aligned CNT film with a tube diameter of ～ 40 nm. These nanofoils are moderately oxidized during reactive sputtering and appeared translucent under the electron microscope. Detailed structural analysis shows that they are comprised of contiguous grains of iridium metal, iridium dioxide, and glassy iridium oxide. Considerable Raman line broadening is also evidenced for the attributed nanosized iridium oxides. Two capacitive properties of the electrode are significantly enhanced with addition of the curved IrO(x) foils. First, IrO(x)NF reduces the electrode Ohmic resistance, which was measured at 3.5 Ω cm(2) for the CNT/SUS and 2.5 Ω cm(2) for IrO(x)NF/CNT/SUS using impedance spectroscopy. Second, IrO(x)NF raises the electrode capacitance from 17.7 F g(-1) (CNT/SUS) to 317 F g(-1) (IrO(x)/CNT/SUS), measured with cyclic voltammetry. This notable increase is further confirmed by the galvanostatic charge/discharge experiment, measuring 370 F g(-1) after 2000 uninterrupted cycles between - 1.0 and 0.0 V (versus Ag/AgCl).     

Nanosized Ni-Mn Oxides Prepared by the Citrate Gel Process and Performances for Electrochemical Capacitors

Nanosized Ni-Mn oxide powders have been successfully citrate gel precursors. The powder materials derived from prepared by thermal decomposition of the Ni-Mn calcination of the gel precursors with various molar ratios of nickel and manganese at different temperatures and time were characterized using thermal analysis （TG-DSC）, scanning electron microscopy （SEM）, X-ray diffraction （XRD） and Brunauer-Emmet-Teller （BET）. The optimized processing conditions of calcination at 400℃ for 1 h with Ni/Mn molar ratio 6 were proved to produce the nanosized Ni-Mn oxide powders with a high specific surface area of 109.62 m^2/g and nanometer particle sizes of 15-30 nm. The capacitance characteristics of the nanosized Ni-Mn oxide electrode in various concentrations of KOH solutions were studied by the cyclic voltammetry （CV） and exhibited both a doublelayer capacitance and a Faradaic capacitance which could be attributed to the electrode consisting of Ni-Mn oxides and residual carbons from the organic gel thermal decomposition. A specific capacitance of 194.8 F/g was obtained for the electrode at the sweep rate of 10 mV/s in 4 mol/L KOH electrolyte and the capacitor showed quite high cyclic stability and is promising for advanced electrochemical capacitors.     

PVA-assisted hydrated vanadium pentoxide/reduced graphene oxide films for excellent Li+and Zn2+storage properties

Low-cost,high safety and environment-friendly aqueous energy storage systems(ESSs)are huge poten-tial for grid-level energy storage,but the(de)intercalation of metal ions in the electrode materials(e.g.vanadium oxides)to obtain superior long-term cycling stability is a significant challenge.Herein,we demonstrate that polyvinyl alcohol(PVA)-assisted hydrated vanadium pentoxide/reduced graphene oxide(V2O5·nH2O/rGO/PVA,denoted as the VGP)films enable long cycle stability and high capacity for the Li+and Zn2+storages in both the VGP//LiCl(aq)//VGP and the VGP//ZnSO4(aq)//Zn cells.The binder-free VGP films are synthesized by a one-step hydrothermal method combination with the filtration.The extensive hydrogen bonds are formed among PVA,GO and H2O,and they act as structural pillars and connect the adjacent layers as glue,which contributes to the ultrahigh specific capacitance and ultralong cyclic performance of Li+and Zn2+storage properties.As for Li+storage,the binder-free VGP4 film(4 mg PVA)electrode achieves the highest specific capacitance up to 1381 F g-1 at 1.0 A g-1 in the three-electrode system and 962 F g-1 at 1.0 A g-1 in the symmetric two-electrode system.It also behaves the outstanding cyclic performance with the capacitance retention of 96.5％after 15000 cycles in the three-electrode system and 99.7％after 25000 cycles in the symmetric two-electrode system.As for Zn2+storage,the binder-free VGP4 film electrode exhibits the high specific capacity of 184 mA h g-1 at 0.5 A g-1 in the VGP4//ZnSO4(aq)//Zn cell and the superb cycle performance of 98.5％after 25000 cycles.This work not only provides a new strategy for the construction of vanadium oxides composites and demonstrates the potential application of PVA-assisted binder-free film with excellent electrochemical properties,but also extends to construct other potential electrode materials for metal ion storage cells.     

One-step strategy to graphene/Ni(OH)2 composite hydrogels as advanced three-dimensional supercapacitor electrode materials

Graphene-based three-dimensional (3D) macroscopic materials have recently attracted increasing interest by virtue of their exciting potential in electrochemical energy conversion and storage. Here we report a facile one-step strategy to prepare mechanically strong and electrically conductive graphene/Ni(OH)₂ composite hydrogels with an interconnected porous network. The composite hydrogels were directly used as 3D supercapacitor electrode materials without adding any other binder or conductive additives. An optimized composite hydrogel containing ～82 wt.% Ni(OH)₂ exhibited a specific capacitance of ～1,247 F/g at a scan rate of 5 mV/s and ～785 F/g at 40 mV/s (～63% capacitance retention) with excellent cycling stability. The capacity of the 3D hydrogels greatly surpasses that of a physical mixture of graphene sheets and Ni(OH)₂ nanoplates (～309 F/g at 40 mV/s). The same strategy was also applied to fabricate graphene-carbon nanotube/Ni(OH)₂ ternary composite hydrogels with further improved specific capacitances (～1,352 F/g at 5 mV/s) and rate capability (～66% capacitance retention at 40 mV/s). Both composite hydrogels obtained here can deliver high energy densities (～43 and ～47 Wh/kg, respectively) and power densities (～8 and ～9 kW/kg, respectively), making them attractive electrode materials for supercapacitor applications. This study opens a new pathway to the design and fabrication of functional 3D graphene composite materials, and can significantly impact broad areas including energy storage and beyond.      

Substrate dependent self-organization of mesoporous cobalt oxide nanowires with remarkable pseudocapacitance

A scheme of current collector dependent self-organization of mesoporous cobalt oxide nanowires has been used to create unique supercapacitor electrodes, with each nanowire making direct contact with the current collector. The fabricated electrodes offer the desired properties of macroporosity to allow facile electrolyte flow, thereby reducing device resistance and nanoporosity with large surface area to allow faster reaction kinetics. Co(3)O(4) nanowires grown on carbon fiber paper collectors self-organize into a brush-like morphology with the nanowires completely surrounding the carbon microfiber cores. In comparison, Co(3)O(4) nanowires grown on planar graphitized carbon paper collectors self-organize into a flower-like morphology. In three electrode configuration, brush-like and flower-like morphologies exhibited specific capacitance values of 1525 and 1199 F/g, respectively, at a constant current density of 1 A/g. In two electrode configuration, the brush-like nanowire morphology resulted in a superior supercapacitor performance with high specific capacitances of 911 F/g at 0.25 A/g and 784 F/g at 40 A/g. In comparison, the flower-like morphology exhibited lower specific capacitance values of 620 F/g at 0.25 A/g and 423 F/g at 40 A/g. The Co(3)O(4) nanowires with brush-like morphology exhibited high values of specific power (71 kW/kg) and specific energy (81 Wh/kg). Maximum energy and power densities calculated for Co(3)O(4) nanowires with flower-like morphology were 55 Wh/kg and 37 kW/kg respectively. Both electrode designs exhibited excellent cycling stability by retaining ～91-94% of their maximum capacitance after 5000 cycles of continuous charge-discharge.     

Binder-free manganese oxide/carbon nanomaterials thin film electrode for supercapacitors

A ternary thin film electrode was created by coating manganese oxide onto a network composed of single-walled carbon nanotubes and single-walled carbon nanohorns. The electrode exhibited a porous structure, which is a promising architecture for supercapacitors applications. The maximum specific capacitances of 357 F/g for total electrode at 1 A/g were achieved in 0.1 M Na(2)SO(4) aqueous solution.     

Electrospun ultralong hierarchical vanadium oxide nanowires with high performance for lithium ion batteries

Ultralong hierarchical vanadium oxide nanowires with diameter of 100-200 nm and length up to several millimeters were synthesized using the low-cost starting materials by electrospinning combined with annealing. The hierarchical nanowires were constructed from attached vanadium oxide nanorods of diameter around 50 nm and length of 100 nm. The initial and 50th discharge capacities of the ultralong hierarchical vanadium oxide nanowire cathodes are up to 390 and 201 mAh/g when the lithium ion battery cycled between 1.75 and 4.0 V. When the battery was cycled between 2.0 and 4.0 V, the initial and 50th discharge capacities of the nanowire cathodes are 275 and 187 mAh/g. Compared with self-aggregated short nanorods synthesized by hydrothermal method, the ultralong hierarchical vanadium oxide nanowires exhibit much higher capacity. This is due to the fact that self-aggregation of the unique nanorod-in-nanowire structures have been greatly reduced because of the attachment of nanorods in the ultralong nanowires, which can keep the effective contact areas of active materials, conductive additives, and electrolyte large and fully realize the advantage of nanomaterial-based cathodes. This demonstrates that ultralong hierarchical vanadium oxide nanowire is one of the most favorable nanostructures as cathodes for improving cycling performance of lithium ion batteries.     

外贴Fe3O4/CNTs杂化碳纳米纸的碳纳米管复合材料吸波性能

通过对Fe₃O₄纳米粒子接枝碳纳米管的单分散水溶液真空吸滤制备出一种新型的杂化碳纳米纸, 它与树脂浸润良好, 可以与复合材料一体成型。分别借助FE-SEM、EDS、BJH法和振动样品磁强计表征杂化碳纳米纸及其复合材料的微观形貌、元素组成、平均孔径分布和磁性能。在8.2~18 GHz频段内利用波导法测量碳纳米管共混复合材料和外贴杂化碳纳米纸/碳纳米管共混复合材料的电磁参数和吸波反射率。研究结果表明: 外贴一层杂化碳纳米纸(厚0.1 mm)后, 碳纳米管共混复合材料的磁损耗明显增加, 在8.2~18 GHz微波频段内吸波反射率基本上全部小于-10 dB(频宽大于9.7 GHz), 在15.42 GHz位置, 反射损耗峰达-43.18 dB, 远优于碳纳米管共混复合材料。     

A nanostructured electrochromic supercapacitor

We report the first successful application of an ordered bicontinuous double-gyroid vanadium pentoxide network in an electrochromic supercapacitor. The freestanding vanadia network was fabricated by electrodeposition into a voided block copolymer template that had self-assembled into the double-gyroid morphology. The highly ordered structure with 11.0 nm wide struts and a high specific surface to bulk volume ratio of 161.4 μm(-1) is ideal for fast and efficient lithium ion intercalation/extraction and faradaic surface reactions, which are essential for high energy and high power density electrochemical energy storage devices. Supercapacitors made from such gyroid-structured vanadia electrodes exhibit a high specific capacitance of 155 F g(-1) and show a strong electrochromic color change from green/gray to yellow, indicating the capacitor's charge condition. The nanostructuring approach and utilizing an electrode material that has intrinsic electrochemical color-change properties are concepts that can be readily extended to other electrochromic intercalation compounds.     

Amorphous Mixed‐Valence Vanadium Oxide/Exfoliated Carbon Cloth Structure Shows a Record High Cycling Stability

Previous studies show that vanadium oxides suffer from severe capacity loss during cycling in the liquid electrolyte, which has hindered their applications in electrochemical energy storage. The electrochemical instability is mainly due to chemical dissolution and structural pulverization of vanadium oxides during charge/discharge cyclings. In this study the authors demonstrate that amorphous mixed‐valence vanadium oxide deposited on exfoliated carbon cloth (CC) can address these two limitations simultaneously. The results suggest that tuning the V⁴⁺/V⁵⁺ ratio of vanadium oxide can efficiently suppress the dissolution of the active materials. The oxygen‐functionalized carbon shell on exfoliated CC can bind strongly with VO _x via the formation of C? O? V bonding, which retains the electrode integrity and suppresses the structural degradation of the oxide during charging/discharging. The uptake of structural water during charging and discharging processes also plays an important role in activating the electrode material. The amorphous mixed‐valence vanadium oxide without any protective coating exhibits record‐high cycling stability in the aqueous electrolyte with no capacitive decay in 100 000 cycles. This work provides new insights on stabilizing vanadium oxide, which is critical for the development of vanadium oxide based energy storage devices.     

Ni2CoS4/还原氧化石墨烯/多孔还原氧化石墨烯的制备及其在超级电容器中的应用

采用水热法制备Ni_2CoS_4活性材料,通过物理过程和水热反应将其与氧化石墨烯(GO)、水热多孔氧化石墨烯(HHGO)复合得到Ni_2CoS_4/还原氧化石墨烯/多孔还原氧化石墨烯(Ni_2CoS_4/RGO/HRGO)复合电极材料。采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、循环伏安测试、恒流充放电测试和交流阻抗测试等,对复合材料的形貌结构、电化学性能进行了表征。研究结果表明:在1 A/g的电流密度下,其比电容为1 684 F/g,在5 A/g的电流密度下循环2 000次后,其比电容保持率为91.8%。Ni_2CoS_4/RGO/HRGO优良的电化学行为归因于这种复合结构使电解液对电极材料的润湿程度提高,进而提高了离子和电荷的传输速率,同时也缓解石墨烯、Ni_2CoS_4的团聚和循环过程中的体积变化。因此,Ni_2CoS_4/RGO/HRGO是一种有良好应用前景的高性能超级电容器电极材料。     

聚吡咯/氧化石墨烯复合电极的制备及性能研究

采用直流电电化学制备了聚吡咯和聚吡咯/石墨烯薄膜电极,研究发现聚吡咯/石墨烯复合电极表面产生了很多小孔和一些羊角状的结构,这可能是由于在聚合过程中,聚合围绕石墨烯吸附对甲基苯磺酸根离子形成的球状体所致。而这些小孔和羊角状的结构在电极的充放电过程中为内层聚吡咯提供了离子交换的通道。在循环伏安的测试中,当扫描速率达到1000mV/S时,聚吡咯/石墨烯复合电极的容量依然保持在229F/g,而纯的PPy电极的容量仅保持在112F/g。     

Ultrathin graphite foam: a three-dimensional conductive network for battery electrodes

We report the use of free-standing, lightweight, and highly conductive ultrathin graphite foam (UGF), loaded with lithium iron phosphate (LFP), as a cathode in a lithium ion battery. At a high charge/discharge current density of 1280 mA g(-1), the specific capacity of the LFP loaded on UGF was 70 mAh g(-1), while LFP loaded on Al foil failed. Accounting for the total mass of the electrode, the maximum specific capacity of the UGF/LFP cathode was 23% higher than that of the Al/LFP cathode and 170% higher than that of the Ni-foam/LFP cathode. Using UGF, both a higher rate capability and specific capacity can be achieved simultaneously, owing to its conductive (～1.3 × 10(5) S m(-1) at room temperature) and three-dimensional lightweight (～9.5 mg cm(-3)) graphitic structure. Meanwhile, UGF presents excellent electrochemical stability comparing to that of Al and Ni foils, which are generally used as conductive substrates in lithium ion batteries. Moreover, preparation of the UGF electrode was facile, cost-effective, and compatible with various electrochemically active materials.     

Encapsulated Vanadium‐Based Hybrids in Amorphous N‐Doped Carbon Matrix as Anode Materials for Lithium‐Ion Batteries

Recently, researchers have made significant advancement in employing transition metal compound hybrids as anode material for lithium‐ion batteries and developing simple preparation of these hybrids. To this end, this study reports a facile and scalable method for fabricating a vanadium oxide–nitride composite encapsulated in amorphous carbon matrix by simply mixing ammonium metavanadate and melamine as anode materials for lithium‐ion batteries. By tuning the annealing temperature of the mixture, different hybrids of vanadium oxide–nitride compounds are synthesized. The electrode material prepared at 700 °C, i.e., VM‐700, exhibits excellent cyclic stability retaining 92% of its reversible capacity after 200 cycles at a current density of 0.5 A g^?1 and attractive rate performance (220 mAh g^?1) under the current density of up to 2 A g^?1. The outstanding electrochemical properties can be attributed to the synergistic effect from heterojunction form by the vanadium compound hybrids, the improved ability of the excellent conductive carbon for electron transfer, and restraining the expansion and aggregation of vanadium oxide–nitride in cycling. These interesting findings will provide a reference for the preparation of transition metal oxide and nitride composites as well.     

高压对高功率脉冲磁控放电等离子体注入与沉积氧化钒薄膜的影响

利用高功率脉冲磁控放电等离子体注入与沉积技术制备了氧化钒薄膜,分别采用X射线衍射仪、原子力显微镜、扫描电子显微镜和电化学分析仪研究了不同高压幅值对氧化钒薄膜的相结构、表面形貌、截面形貌以及耐腐蚀性能的影响。结果表明制备的氧化钒薄膜以VO2(-211)相为主,还含有少量的VO2(111)、VO(220)、VO(222)相。不同高压下氧化钒薄膜表面致密、平整,其表面粗糙度仅为几个纳米,显示出良好的表面质量。氧化钒薄膜表现出典型致密的柱状晶生长形貌,且随着高压增加,氧化钒薄膜膜层厚度有所下降。氧化钒薄膜耐腐蚀性能较纯铝基体有较大提高,腐蚀电位提高0.093V,腐蚀电流下降1～2个数量级;当高压为-15kV时,氧化钒薄膜腐蚀电位最高,腐蚀电流最低,表现出最佳的耐蚀性能。     

Growth of manganese oxide nanoflowers on vertically-aligned carbon nanotube arrays for high-rate electrochemical capacitive energy storage

Manganese oxide nanoflower/carbon nanotube array (CNTA) composite electrodes with hierarchical porous structure, large surface area, and superior conductivity was controllable prepared by combining electrodeposition technique and a vertically aligned CNTA framework. This binder-free manganese oxide/CNTA electrode presents excellent rate capability (50.8% capacity retention at 77 A/g), high capacitance (199 F/g and 305 F/cm (3)), and long cycle life (3% capacity loss after 20 000 charge/discharge cycles), with strong promise for high-rate electrochemical capacitive energy storage applications.     

Substrate dependent morphological and electrochemical properties of V<Subscript>2</Subscript>O<Subscript>5</Subscript> thin films prepared by spray pyrolysis

A scheme of substrate dependent self-organization of vanadium oxide has been used to create unique supercapacitor electrodes. In present work, thin films of V₂O₅ were prepared on different substrates by using well known spray pyrolysis technique.The sample depositions were carried out at 673 K, by spraying 0.05 M, 40 ml solution of ammonium metavanadate at the spray rate 10 ml/min. V₂O₅ thin films grown on aluminum (Al), copper (Cu) and stainless steel (SS) substrates shows porous valley and mountains, rough and dense morphology with overgrown agglomeration of nano grains. In electrochemical characterizations, by using standard electrode configurations, specific capacitance values were evaluated from cyclic voltammetry in 1 M KCl, these are 18.43, 1500.0, 439.60 and 250.58 F/g at 5 mV/s for the electrodes deposited on Al, Cu, SS substrates and two electrode cell respectively. Charge discharge behavior of the SS electrode and two electrode cell was observed using chronopotentiometry. This exhibits specific energy, specific power, and coulombic efficiency (η) 84.91 Wh/kg, 120.00 kW/kg and 89.51 % for SS electrode and 19.92 Wh/kg, 65.00 kW/kg and 99.90 % for two electrode cell respectively. Impedance study was carried out in the frequency range 1 mHz–1 MHz depicts less internal resistance of SS electrode ~2.69 Ω and two electrode cell ~3.04 Ω.     

盐酸掺杂聚苯胺的电容性能研究

低温下化学氧化合成了盐酸掺杂聚苯胺,采用扫描电子显微镜、恒流充放电、循环伏安和交流阻抗技术研究了聚苯胺的形貌和电化学电容性能.结果表明,低温下合成的聚合物呈颗粒状堆积,颗粒粒径约300～500nm;电化学测试结果表明,电流密度为8mA/cm2时聚苯胺在酸性电解液中的单电极比电容高达512F/g,100次循环后比电容为初始容量的94.1%,循环性能良好.     

POSS/粘土/多壁碳纳米管杂化碳纳米纸基复合材料防火性研究

多壁碳纳米管(MWCNTs)、粘土和多面齐聚半硅氧烷(POSS)组成的杂化碳纳米纸是通过碳纳米管巴基纸制备工艺制备而成, 碳纳米纸可做为表面防火层与聚合物基复合材料共固化成型。利用场发射扫描电镜(FESEM)和BJH法分别对碳纳米纸和杂化碳纳米纸微观结构和平均孔径分布进行表征。利用锥形量热仪在热辐射功率50 kW/m²条件下分析外贴碳纳米纸复合材料及复合材料对比样的防火特性。燃烧实验结果表明: 碳纳米纸和杂化碳纳米纸作为防火层的复合材料的峰值热释放速率(PHRR)与复合材料对比样相比分别下降20.2%和35%, 同时CO释放量和烟释放量也明显降低。通过FESEM研究表明燃烧实验后外贴杂化碳纳米纸复合材料的燃烧残余物表面形成了一层致密的积炭物结构, 防火阻燃性能明显提高。