Construction of hierarchical three-dimensional interspersed flower-like nickel hydroxide for asymmetric supercapacitors

Low-cost and easily obtainable electrode materials are crucial for the application of supercapacitors.Nickel hydroxides have recently attracted intensive attention owning to their high theoretical specific capacitance,high redox activity,low cost,and eco-friendliness.In this study,novel three-dimensional (3D) interspersed flower-like nickel hydroxide was assembled under mild conditions.When ammonia was used as the precipitant and inhibitor and CTAB was used as an exfoliation agent,the obtained exfoliated ultrathin Ni(OH)2 nanosheets were assembled into 3D interspersed flower-like nickel hydroxide.In this novel 3D structure,the ultrathin Ni(OH)2 nanosheets not only provided a large contact area with the electrolyte,reducing the polarization of the electrochemical reaction and providing more active sites,but also reduced the concentration polarization in the electrode solution interface.Consequently,the utilization efficiency of the active material was improved,yielding a high capacitance.The electrochemical performance was improved via promoting the electrical conductivity by mixing the as-synthesized Ni(OH)2 with carbon tubes (N-4-CNT electrode),yielding excellent specific capacitances of 2,225.1 F·g-1 at 0.5 A·g-1 in a three-electrode system and 722.0 F·g-1 at 0.2 A·g-1 in a two-electrode system.The N-4-CNT//active carbon (AC) device exhibited long-term cycling performance (capacitance-retention ratio of 111.4％ after 10,000 cycles at 5 A·g-1) and a high specific capacitance of 180.5 F·g-1 with a high energy density of 33.5 W·h·kg-1 and a power density of 2,251.6 W·kg-1.     

Freestanding hierarchical porous carbon film derived from hybrid nanocellulose for high-power supercapacitors

Nanocellulose is a sustainable and eco-friendly nanomaterial derived from renewable biomass.In this study,we utilized the structural advantages of two types of nanocellulose and fabricated freestanding carbonized hybrid nanocellulose films as electrode materials for supercapacitors.The long cellulose nanofibrils (CNFs) formed a macroporous framework,and the short cellulose nanocrystals were assembled around the CNF framework and generated micro/mesopores.This two-level hierarchical porous structure was successfully preserved during carbonization because of a thin atomic layer deposited (ALD) Al2O3 conformal coating,which effectively prevented the aggregation of nanocellulose.These carbonized,partially graphitized nanocellulose fibers were interconnected,forming an integrated and highly conductive network with a large specific surface area of 1,244 m2·g-1.The two-level hierarchical porous structure facilitated fast ion transport in the film.When tested as an electrode material with a high mass loading of 4 mg·cm-2 for supercapacitors,the hierarchical porous carbon film derived from hybrid nanocellulose exhibited a specific capacitance of 170 F.g-1and extraordinary performance at high current densities.Even at a very high current of 50 A·g-1,it retained 65％ of its original specific capacitance,which makes it a promising electrode material for high-power applications.     

NiS2/三维多孔石墨烯复合材料作为超级电容器电极材料的电化学性能

选用合适的软模板,通过简便的一步溶剂热法成功制备了NiS₂/三维多孔石墨烯（3D rGO）复合材料。利用FESEM、TEM、XPS和电化学工作站对样品的表面形貌、元素价态和电化学性能进行表征。结果表明:制备的NiS₂/3D rGO复合材料存在石墨烯三维堆叠的孔道结构,且具备较大的比表面积,为57.51 m2g-1。电化学测试表明,在1 Ag-1的电流密度下NiS₂/3D rGO复合材料的比电容高达1 116.7 Fg-1,而且当电流密度增加到5 Ag-1时NiS₂/3D rGO复合材料的比电容为832.2 Fg-1,比电容保持率为1 Ag-1时的74.5%。在4 Ag-1电流密度下,经过1 000次循环后,NiS₂/3D rGO复合材料的比电容仍能保持91.2%。因此,NiS₂/3D rGO复合材料可作为一种理想的超级电容器电极材料。      

石墨烯负载花球状二氧化锰复合材料制备及其电容性能研究

利用高锰酸钾与乙醇之间的氧化还原反应,在多孔石墨烯表面沉积纳米二氧化锰花球,获得了一种新型的复合电极材料。通过XRD,TG,SEM,TEM等分析手段确定了材料的晶体结构、化学成分、微观形貌特征。电化学性能测试表明:纳米二氧化锰花球具有优异的比电容,但是倍率性能和循环性能不足。通过在石墨烯表面负载纳米二氧化锰花球,能够显著增加石墨烯的比电容,同时改善纳米二氧化锰花球的倍率性能和循环性能。采用0.5mol/L K_2SO_4电解液,进行三电极循环伏安测试,复合电极材料在2mV·s^-1扫速下的比电容高达295F·g^-1,在1000mV·s^-1扫速下,比电容仍然可达102F·g^-1,同时100mV·s^-1,1000次循环后,电容循环保持率可达96.3%。这表明石墨烯负载花球状二氧化锰材料是一种极具潜力的超级电容器电极材料。     

模板法中孔炭及其双电层电容性能(英文)

以乙酸镁和柠檬酸镁热解得到的MgO为模板,热塑性沥青为碳前驱体,采用程序升温一步炭化法(950℃,N2)制备了高比表面积中孔炭材料。尽管未进行活化,两种模板前驱体与沥青混合所制中孔炭材料均可获得非常高的比表面积。以这两种中孔炭作为双电层电容器的电极材料,在质量分数为30%的KOH电解液中测试其电化学性能。结果表明:这两种中孔炭电极均可得到较高的比电容量和理想的功率特性,尤其是柠檬酸镁作前驱体时,MgO与沥青质量比为4时得到的炭材料(MCP8/2)在20mA.g-1的电流密度下得到284F.g-1的比电容量,且在1000mA.g-1时仍能得到236F.g-1的比电容。交流阻抗测试表明:组装的双电层电容器的内部阻抗均小于3.5Ω。     

Wire-Shaped 3D-Hybrid Supercapacitors as Substitutes for Batteries

We report a wire-shaped three-dimensional(3D)-hybrid supercapacitor with high volumetric capacitance and high energy density due to an interconnected 3D-configuration of the electrode allowing for large number of electrochemical active sites,easy access of electrolyte ions,and facile charge transport for flexible wearable applications.The interconnected and compact electrode delivers a high volumetric capacitance(gravimetric capacitance)of 73 F cm−3(2446 F g−1),excellent rate capability,and cycle stability.The 3D-nickel cobalt-layered double hydroxide onto 3D-nickel wire(NiCo LDH/3D-Ni)//the 3D-manganese oxide onto 3D-nickel wire(Mn3O4/3D-Ni)hybrid supercapacitor exhibits energy density of 153.3 Wh kg−1 and power density of 8810 W kg−1.The red lightemitting diode powered by the as-prepared hybrid supercapacitor can operate for 80 min after being charged for tens of seconds and exhibit excellent electrochemical stability under various deformation conditions.The results verify that such wire-shaped 3D-hybrid supercapacitors are promising alternatives for batteries with long charge–discharge times,for smart wearable and implantable devices.     

Biowaste derived porous carbon sponge for high performance supercapacitors

Here,an agricultural waste (the stem pith of helianthus annuus,SPHA) is firstly used as the precursor for preparing three-dimensional (3D) porous carbon sponge (PCS).The as-prepared 3D PCS (SPHA-700) pos-sesses unique sponge-like structure,large specific surface area (SSA) and high nitrogen doping level (4.52 at.％),which benefit the enhancement of conductivity (5.8 S cm-1) and wettability.As a binder-free elec-trode for solid-state symmetric supercapacitor,SPHA-700 delivers a relatively high specific capacitance of 137.1 F g-1 at 0.5 A g-1.Moreover,activated SPHA-700 (SPHA-ac-700-2) displays an even higher specific capacitance (403.6 F g-1 at 0.5 A g-1) in 6.0 M KOH electrolyte.The SPHA-ac-700-2-based symmetrical supercapacitor can offer high specific capacitance (271 F g-1 at 1 A g-1) and good rate capability (82.1％of capacitance retention at 1-80 A g-1) in 6.0 M KOH electrolyte,together with high energy density(23.3 Wh kg-1 at 450 W kg-1) in 1.0 M Na2SO4 electrolyte.Such excellent performance of SPHA-ac-700-2 is believed to have originated from the crushed sponge-like structure,O/N-co-doping (10.6 at.％ O and 3.3 at.％ N),high SSA,large total pore volume,and hierarchical pore structure.     

酚醛基活性炭布的制备及电化学性能研究

以实验室自制的酚醛基纤维布为原料,以二氧化碳为活化剂制备了系列酚醛基活性炭布(Activated Carbon Cloths,ACCs),利用低温N2(77K)吸附法测定了所制活性炭布的孔结构,并将所制得活性炭布用做超级电容器电极材料,采用恒流充放电法和交流阻抗技术考察了所制模拟电容器的电化学性能(电解液:1 M(CH...     

High‐Stacking‐Density,Superior‐Roughness LDH Bridged with Vertically Aligned Graphene for High‐Performance Asymmetric Supercapacitors

The high‐performance electrode materials with tuned surface and interface structure and functionalities are highly demanded for advanced supercapacitors. A novel strategy is presented to conFigure high‐stacking‐density, superior‐roughness nickel manganese layered double hydroxide (LDH) bridged by vertically aligned graphene (VG) with nickel foam (NF) as the conductive collector, yielding the LDH‐NF@VG hybrids for asymmetric supercapacitors. The VG nanosheets provide numerous electron transfer channels for quick redox reactions, and well‐developed open structure for fast mass transport. Moreover, the high‐stacking‐density LDH grown and assembled on VG nanosheets result in a superior hydrophilicity derived from the tuned nano/microstructures, especially microroughness. Such a high stacking density with abundant active sites and superior wettability can be easily accessed by aqueous electrolytes. Benefitting from the above features, the LDH‐NF@VG can deliver a high capacitance of 2920 F g^?1 at a current density of 2 A g^?1, and the asymmetric supercapacitor with the LDH‐NF@VG as positive electrode and activated carbon as negative electrode can deliver a high energy density of 56.8 Wh kg^?1 at a power density of 260 W kg^?1, with a high specific capacitance retention rate of 87% even after 10 000 cycles.     

组氨酸功能化碳点/石墨烯气凝胶的制备及超级电容器性能

通过一步水热法制备组氨酸功能化碳点/石墨烯气凝胶(His-CDs/GA)。该材料具有独特的三维多孔结构、丰富的含氮和含氧官能团, 有利于电解液离子的快速扩散和提供更多的活性位点。当GO与His-CDs的质量比为2 : 1时, His-CDs/GA-2在1 A·g ^-1电流密度下比电容达到304 F·g ^{- 1}, 比GA(172 F·g ^-1)提高了76.7%; 当电流密度从1 A·g ^-1增加到50 A·g ^-1, 其比电容保持率为71.4%; 在电流密度10 A·g ^-1下, 循环充放电30000次后, 比电容仍保留93.5%。由His-CDs/GA组装的对称超级电容器展现出高能量密度(在功率密度为250 W/kg时, 能量密度达到10.14 Wh/kg)和良好的循环性能(在5 A·g ^-1下循环充放电20000次后, 比电容保持率为88.4%)。结果表明, His-CDs/GA是一种应用前景广阔的超级电容器电极材料。     

Extremely high-rate aqueous supercapacitor fabricated using doped carbon nanoflakes with large surface area and mesopores at near-commercial mass loading

Achieving a satisfactory energy-power combination in a supercapacitor that is based on all-carbon electrodes and operates in benign aqueous media instead of conventional organic electrolytes is a major challenge.For this purpose,we fabricated carbon nanoflakes (20-100 nm in thickness,5-μm in width) containing an unparalleled combination of a large surface area (3,000 m2·g-1 range) and mesoporosity (up to 72％).These huge-surface area functionalized carbons (HSAFCs) also had a substantial oxygen and nitrogen content (～10 wt.％ combined),with a significant fraction of redox-active carboxyl/phenol groups in an optimized specimen.Their unique structure and chemistry resulted from a tailored single-step carbonization-activation approach employing (2-benzimidazolyl) acetonitrile combined with potassium hydroxide (KOH).The HSAFCs exhibited specific capacitances of 474 F·g-1 at 0.5 A·g-1 and 285 F·g-1 at 100 A·g-1 (charging time ＜ 3 s) in an aqueous 2 M KOH solution.These values are among the highest reported,especially at high currents.When tested with a stable 1.8-V window in a 1 M Na2SO4 electrolyte,a symmetric supercapacitor device using the fabricated nanoflakes as electrodes yielded a normalized active mass of 24.4 Wh·kg-1 at 223 W·kg-1 and 7.3 Wh·kg-1 at 9,360 W·kg-1.The latter value corresponds to a charge time of ＜3 s.The cyclability of the devices was excellent,with 93％ capacitance retention after 10,000 cycles.All the electrochemical results were achieved by employing electrodes with near-commercial mass loadings of 8 mg·cm-2.     

Metal-organic framework derived hierarchical NiCo2O4 triangle nanosheet arrays@SiC nanowires network/carbon cloth for flexible hybrid supercapacitors

To overcome the disadvantages of traditional powder electrodes,such as the insufficient performance,the aggregation of active materials,and the complex fabrication process,rationally constructing free-standing electrode materials with hierarchical architecture is an effective and promising method,which could further improve the electrochemical properties.Herein,using metal-organic framework nanoar-rays (MOFNAs) as self-sacrificial templates and SiC nanowires (SiCNWs) network as nanoscale conductive skeletons,we successfully fabricated the hierarchical core-shell SiCNws@NiCo2O4NAs on carbon cloth (CC)substrate.Taking advantages of structural merits,such as hierarchical porous triangle-like NiCo2O4NAs,the interwoven SiCNWs network and conductive CC substrate,when evaluated as a binder-free superca-pacitor electrode,the CC/SiCNWs@NiCo2O4NAs shows a high specific capacitance of 1604.7 F g-1 (specific capacity of 222.9 mA h g-1) at 0.5 A g 1,good rate performance,and excellent cycling stability.Signifi-cantly,the hybrid supercapacitor assembled with CC/SiCNWs@NiCo2O4NAs as the cathode and MOF derived CC/SiCNWs@CNAs as the anode,could deliver a high specific density of 49.9 W h kg-1 at a specific power of 800 W kg-1,stable cycling performance,and good flexibility.Impressively,this feasible strategy for fabricating hierarchical structure displays great potential in the field of energy storage.     

高比容纳米Ni（OH）2的制备及其电化学电容性能

以草酸和乙酸镍为原料,通过低温固相法合成前驱体(NiC2O4.2H2O)粉末。用此前驱体粉末与固态NaOH混合并充分研磨制得纳米Ni(OH)2粉末。经SEM、XRD测试表明,制得的纳米Ni(OH)2粉末是平均粒径约为12nm的β-Ni(OH)2。用循环伏安法、恒流充放电测试和交流阻抗谱研究Ni(OH)2电极的电化学电容特性。结果表明在电流密度为1A.g-1时,其比电容高达2271F.g-1,且经多次循环后表现出较好的循环稳定性能。     

Efficient Supercapacitor Energy Storage Using Conjugated Microporous Polymer Networks Synthesized from Buchwald–Hartwig Coupling

Supercapacitors have received increasing interest as energy storage devices due to their rapid charge–discharge rates, high power densities, and high durability. In this work, novel conjugated microporous polymer (CMP) networks are presented for supercapacitor energy storage, namely 3D polyaminoanthraquinone (PAQ) networks synthesized via Buchwald–Hartwig coupling between 2,6‐diaminoanthraquinone and aryl bromides. PAQs exhibit surface areas up to 600 m² g^?1, good dispersibility in polar solvents, and can be processed to flexible electrodes. The PAQs exhibit a three‐electrode specific capacitance of 576 F g^?1 in 0.5 m H₂SO₄ at a current of 1 A g^?1 retaining 80–85% capacitances and nearly 100% Coulombic efficiencies (95–98%) upon 6000 cycles at a current density of 2 A g^?1. Asymmetric two‐electrode supercapacitors assembled by PAQs show a capacitance of 168 F g^?1 of total electrode materials, an energy density of 60 Wh kg^?1 at a power density of 1300 W kg^?1, and a wide working potential window (0–1.6 V). The asymmetric supercapacitors show Coulombic efficiencies up to 97% and can retain 95.5% of initial capacitance undergo 2000 cycles. This work thus presents novel promising CMP networks for charge energy storage.     

ZIF-67/rGO/NiPc composite electrode material for high-performance asymmetric supercapacitors

In this reported study, novel multiple dimensional ZIF-67/rGO/NiPc composite materials were prepared for supercapacitors. The electrochemical test showed that the ZIF-67/rGO/NiPc electrode achieved a remarkable specific capacitance of 860 F g^?1 at a current density of 1 A g^?1, which was superior to that of the rGO/NiPc and ZIF-67/rGO electrodes. An asymmetric supercapacitor based on ZIF-67/rGO/NiPc//activated carbon exhibited a high specific capacitance of 200.67 F g^?1 and an extraordinary energy density of 62.7 Wh kg^?1 at a corresponding power density of 750 W kg^?1. In addition, the device demonstrated 94.6% capacitance retention after 5000 cycles. The assembled asymmetric supercapacitors could easily powered a green light-emitting diode. This work revealed a promising research route for the rational construction of multiple dimensioned high-performance electrodes materials for use in new energy storage devices.

     

Hierarchical 3D All‐Carbon Composite Structure Modified with N‐Doped Graphene Quantum Dots for High‐Performance Flexible Supercapacitors

Flexible supercapacitors have shown enormous potential for portable electronic devices. Herein, hierarchical 3D all‐carbon electrode materials are prepared by assembling N‐doped graphene quantum dots (N‐GQDs) on carbonized MOF materials (cZIF‐8) interweaved with carbon nanotubes (CNTs) for flexible all‐solid‐state supercapacitors. In this ternary electrode, cZIF‐8 provides a large accessible surface area, CNTs act as the electrical conductive network, and N‐GQDs serve as highly pseudocapactive materials. Due to the synergistic effect and hierarchical assembly of these components, N‐GQD@cZIF‐8/CNT electrodes exhibit a high specific capacitance of 540 F g^?1 at 0.5 A g^?1 in a 1 m H₂SO₄ electrolyte and excellent cycle stability with 90.9% capacity retention over 8000 cycles. The assembled supercapacitor possesses an energy density of 18.75 Wh kg^?1 with a power density of 108.7 W kg^?1. Meanwhile, three supercapacitors connected in series can power light‐emitting diodes for 20 min. All‐solid‐state N‐GQD@cZIF‐8/CNT flexible supercapacitor exhibits an energy density of 14 Wh kg^?1 with a power density of 89.3 W kg^?1, while the capacitance retention after 5000 cycles reaches 82%. This work provides an effective way to construct novel electrode materials with high energy storage density as well as good cycling performance and power density for high‐performance energy storage devices via the rational design.     

基于三维石墨烯衬底的纳米片状水合氧化钌：电化学沉积制备以及柔性超级电容器储能应用

可穿戴设备的快速发展刺激了对柔性高面容量储能设备的迫切需求。本工作采用一种简单的无粘结剂阴极电沉积方法将纳米片状RuO_x·nH₂O沉积固定在三维石墨烯骨架上, 以提高RuO_x·nH₂O的利用效率, 实现了更优良的电极导电性, 并缩短了质子和电子的扩散传输路径。在2 mV?s ^-1时, 它的面容量高达3.78 F?cm ^-2, 主要归因于材料的纳米层状结构有利于电解质进入活性物质RuO_x·nH₂O的内部。另外, 以这种电极材料制备得到的全固态柔性超级电容器, 在10 mA?cm ^-2的电流密度下, 能量密度达到0.1 mWh?cm ^-2, 功率密度达到2.4 mW?cm ^-2, 超过大部分文献报道。     

用作双电层电容器电极材料的三维层次孔结构多孔炭的合成

以葡萄糖为碳源,由金属框架有机物( MOF)高效地合成出一种具有三维层次孔结构的多孔炭.当葡萄糖渗入到方形MOF的表面或内部空隙之后,逐步进行聚合和炭化.在此过程中,MOF分解出ZnO,ZnO进一步被基体炭或CO还原成Zn;而Zn又在炭化过程中逸出,以致形成连续的基体炭组织.当所合成的多孔炭用作双电层电容器电极材料时,在1 mo1/L NEt4 BF4/碳酸丙烯酯电解液体系中,其初始比电容达175F·g-1(电流强度0.6A·g-1),并在12A·g-1大电流密度下电容保持率高达94.2％.     

A Flexible Ionic Liquid Gelled PVA‐Li2SO4 Polymer Electrolyte for Semi‐Solid‐State Supercapacitors

A novel high‐performance flexible gel polymer electrolyte (FGPE) for supercapacitors is prepared by a freeze‐drying method. In the presence of 1‐butyl‐3‐methylimidazolium chloride (BMIMCl) ionic liquid, Li₂SO₄ can easily be added into poly(vinyl alcohol) (PVA) aqueous solution over a large concentration range. The resultant FGPE demonstrates considerably high ionic conductivity (37 mS cm⁻¹) and a high fracture strain at 100% elongation at the optimal weight ratio of PVA:BMIMCl:Li₂SO₄ = 1:3:2.2. The supercapacitor fabricated with the resultant FGPE and activated carbon electrodes shows an electrode‐specific capacitance of 136 F g⁻¹ with a stable operating voltage of 1.5 V, a maximum energy density of 10.6 Wh kg⁻¹, and a power density of 3400 W kg⁻¹. Double supercapacitors in series can efficiently drive a light emitting diode (LED) bulb for over 5 min and the retention of the specific capacitance reaches 90% even after 3000 charge–discharge cycles. The ionic conductivity and charge–discharge behaviors of the resultant FGPE are not affected by bending up to 180°. The flexible supercapacitor device shows only a small capacitance loss of 18% after 1000 cycles of 135° bending.     

Conductive polypyrrole incorporated nanocellulose/MoS2 film for preparing flexible supercapacitor electrodes

Conductive films have emerged as appealing electrode materials in flexible supercapacitors owing to their conductivity and mechanical flexibility. However, the unsatisfactory electrode structure induced poor output performance and undesirable cycling stability limited their application. Herein, a well-designed film was manufactured by the vacuum filtration and in-situ polymerization method from cellulose nanofibrils (CNFs), molybdenum disulfide (MoS₂), and polypyrrole. The electrode presented an outstanding mechanical strength (21.3 MPa) and electrical conductivity (9.70 S·cm⁻¹). Meanwhile, the introduce of hydrophilic CNFs induced a desirable increase in diffusion path of electrons and ions, along with the synergistic effect among the three components, further endowed the electrode with excellent specific capacitance (0.734 F·cm⁻²) and good cycling stability (84.50% after 2000 charge/discharge cycles). More importantly, the flexible all-solid-state symmetric supercapacitor delivered a high specific capacitance (1.39 F·cm⁻² at 1 mA·cm⁻²) and a volumetric energy density (6.36 mW·h·cm⁻³ at the power density of 16.35 mW·cm⁻³). This work provided a method for preparing composite films with desired mechanical and electrochemical performance, which can broaden the high-value applications of nanocellulose.