Effects of Reaction Temperature on Microstructure and Advanced Pseudocapacitor Properties of NiO Prepared via Simple Precipitation Method

Morphology-controlled synthesis and large-scale self-assembly of nanoscale building blocks into complex nanoarchitectures is still a great challenge in nanoscience. In this work, various porous NiO nanostructures are obtained by a simple ammonia precipitation method and we find that the reaction temperature has a significant impact on their microstructures. Nanoflowers and nanoflakes have been obtained at 0 and50, while, weakly self-assembly nanoflowers with nanoflakes are formed at 20. In order to understand the process-structure-property relationship in nanomaterial synthesis and application, the as-prepared NiO is used as supercapacitor electrode materials, and evaluated by electrochemical measurement. The experimental results indicate that the material obtained at lower temperature has higher pseudocapacitance, the specific capacitance of 944, 889 and 410 F/g are reached for the materials prepared at 0, 20 and 50 and further calcined at 300, respectively. While the material obtained at higher temperature has excellent rate capacity. This offers us an opportunity searching for exciting new properties of NiO, and be useful for fabricating functional nanodevices.

Enabling Extraordinary Rate Performance for Poorly Conductive Oxide Pseudocapacitors

Pseudocapacitive transition metal oxides(PTMOs)have the advantages of high areal capacitance and material density suitable for high-energy supercapacitor devices,but they are typically marred by insufficient rate performance,which in turn deteriorates cyclic stability at high current levels.Using the example of spinel manganese oxide,herein we demonstrate that a pseudocapacitive oxide electrode of remarkable rate performance and cyclic stability may be realized by adopting oxide nanocrystallites,which are derived based on a novel solution chemistry,and carbon additive(CA)nanoparticles with highly uniform of size distributions.Precisely controlling the particle morphology and size distribution of the active material and conductive additive(CA)in the nanometer range can maximize the density of active material-CA-electrolyte three-phase contact points,thus facilitating synchronized electron and cation flow for the completion of surface faradaic reactions.The resultant Mn3O4 pseudocapacitive electrode exhibits rate capability and cycle stability,including 60%capacity retention at 60 A g-1 and no capacity fade over 100000 cycles under dynamic current densities,far superior to the state-of-the-art PTMO electrodes.The electrode design strategy is in general applicable to pseudocapacitors containing poorly conductive active materials.

Defect engineered nickel hydroxide nanosheets for advanced pseudocapacitor electrodes

While the past years have witnessed great achievement in pseudocapacitors,the inauguration of electrode materials of high-performance still remains a formidable challenge.Moreover,the capacity and rate capability of the electrode depends largely on its electrical conductivity,which ensures fast charge transfer kinetics in both the grain bulk and grain boundaries.Here,nickel hydroxides with oxygen vacancies are facilely fabricated via a hydrothermal method.The active materials exhibit a high specific capacitance of 3250 F·g^(−1)and a high areal of capacitance of 14.98 F·cm^(−2)at 4.6 mA·cm^(−2).The asymmetric supercapacitor device based on our material delivers a high energy density of~71.6 Wh·kg^(−1)and a power density of~17,300 W·kg^(−1)and could retain~95%of their initial capacitance even after 30,000 cycles.In addition,the defect-rich hydroxides demonstrate higher electrical conductivity as well as dielectric constant,which is responsible for the superior pseudocapacitive performance.Our new scientific strategy in terms of taking the advantages of oxygen vacancies might open up new opportunities for qualified pseudocapacitive materials of overall high performances not only for nickel hydroxides but also for other metal hydroxides/oxides.

Redox-active conjugated microporous polymers as electron-accepting organic pseudocapacitor electrode materials for flexible energy storage

Efficient energy storage devices,i.e.pseudocapacitors,are being intensively pursued to address the environmental and energy crises.Most high-performance pseudocapacitors are based on inorganic materials,while organic materials with broader synthetic tunability have attracted increasing interest.Despite recent progress,electron-deficient(n-type)organic pseudocapacitive materials for flexible energy storage are highly demanded yet remain largely unexplored.Here a novel set of n-type perylene diimide(PDI)based conjugated microporous polymers(CMPs),namely,CMP-1,CMP-2 and CMP-3,have been created to integrate excellent desirable characteristics as organic pseudocapacitor electrode materials for flexible energy storage.In light of electron-accepting redox-active sites,hierarchically porous structures,as well as amide-linked networks,the PDI-CMPs electrodes displayed n-type pseudocapacitive behaviors with high capacity(139-205 F g^(-1)at 0.5 A g^(-1)),wide and negative biases(-1.0 to 0 V vs.Ag/AgCl),and long cycling stability.CMP-3 consisting of tetraphenylmethane three-dimensional(3D)building block and PDI units demonstrates not only higher capacitance but also better performance stability because of the higher specific surface area and faster diffusion kinetics as compared to its counterpart CMP-1.Asymmetric supercapacitors(SCs)based on CMP-3 and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)(PEDOT/PSS)exhibited wider potential window(1.8 V)and higher capacitance(17.4 m F cm^(-2))compared with symmetric SCs based on PEDOT/PSS electrodes.Notably,CMP-3 also demonstrates attractive potentials as the anode for rechargeable Li-ion batteries.The study sheds light on the fundamental understanding of the key structural parameters that determine their electrochemical and transport properties,thus opening a new door for the rational design of efficient and stable n-type organic electrode materials for flexible energy storage applications.

An aqueous 2.1 V pseudocapacitor with MXene and V-MnO_(2) electrodes

MXenes have shown record-breaking redox capacitance in aqueous electrolytes,but in a limited voltage window due to oxidation under anodic potential and hydrogen evolution under high cathodic potential.Coupling Ti3C2Tx Xene negative electrode with RuO_(2) or carbon-based positive electrodes expanded the voltage window in sulfuric acid electrolyte to about 1.5 V.Here,we present an asymmetric pseudocapacitor using abundant and eco-friendly vanadium doped MnO_(2) as the positive and Ti_(3)C_(2)Tx MXene as the negative electrode in a neutral 1M Li2SO4 electrolyte.This all-pseudocapacitive asymmetric device not only uses a safer electrolyte and is a much less expensive counter-electrode than RuO_(2),but also can operate within a 2.1 V voltage window,leading to a maximum energy density of 46 Wh/kg.This study also demonstrates the possibility of using MXene electrodes to expand the working voltage window of traditional redox-capable materials.

Amorphous Cobalt Boron Alloy@Graphene Oxide Nanocomposites for Pseudocapacitor Applications

Amorphous Co-B alloy nanoparticles grown on graphene sheets were synthesized via a chemical reduc- tion approach and successfully used for an application as a pseudocapacitor. This study aims to improve the capacity and cycling stability of amorphous Co-B alloy nanoparticles grown on conductive graphene sheets. The products were characterized by X-ray powder diffraction, scanning electron microscopy, and transmission electron microscopy. As electrode materials for pseudocapacitors, the amorphous Co-B alloy grown on graphene oxide （Co-B@GO） exhibits a high specific capacitance of 460 F g-1, which is nearly 1.5 times greater than that of bare Co-B nanoparticles at 1 A g-l, The specific capacitance preserved 84% of the initial capacitance even after 1000 cycles at a scan rate of 10 m V-1, suggesting its promising po- tential as pseudocapacitor materials.

A survey of hybrid energy devices based on supercapacitors

Developing multifunctional energy storage systems with high specific energy, high specific power and long cycling life has been the one of the most important research directions. Compared to batteries and traditional capacitors, supercapacitors possess more balanced performance with both high specific power and long cycle-life. Nevertheless, regular supercapacitors can only achieve energy storage without harvesting energy and the energy density is still not very high compared to batteries. Therefore, combining high specific energy and high specific power,long cycle-life and even fast self-charging into one cell has been a promising direction for future energy storage devices. The multifunctional hybrid supercapacitors like asymmetric supercapacitors, batteries/supercapacitors hybrid devices and self-charging hybrid supercapacitors have been widely studied recently. Carbon based electrodes are common materials used in all kinds of energy storage devices due to their fabulous electrical and mechanical properties. In this survey, the research progress of all kinds of hybrid supercapacitors using multiple effects and their working mechanisms are briefly reviewed. And their advantages and disadvantages are discussed. The hybrid supercapacitors have great application potential for portable electronics, wearable devices and implantable devices in the future.

The key challenges and future opportunities of electrochemical capacitors

Electrochemical capacitors(ECs)with unique merits of fast charge/discharge rate and long cyclability are one of the representative electrochemical energy storage systems,possessing wide applications in power electronics and automotive transportation,etc.[1,2].Furthermore.

氮掺杂石墨烯的制备及在超级电容器中的应用

以氧化石墨烯和三聚氰胺为原料制备氮/石墨烯复合材料。用XRD、SEM、X射线光电子能谱(XPS)和N2吸附等实验进行物理性能分析;用交流阻抗谱、恒流充放电(GCD)等实验进行电化学性能测试。元素分析与XPS分析表明,N元素已经掺杂到石墨烯中,当三聚氰胺掺杂量增加时,石墨烯中N元素的含量也增加。氮掺杂后制得的石墨烯材料表现出较好的双电层电容特性,其中,G-4(三聚氰胺与氧化石墨烯的质量比1∶4)呈现出相对最佳的电化学性能:在0.01~2.85 V循环,0.1 A/g电流下的比电容达206.4 F/g,循环2000次的电容保持率达82.13%;可在651.04 W/kg、10.5 kW/kg的比功率下分别提供33.62 W·h/kg、15.77 W·h/kg的比能量。

赝电容型超级电容器电极材料的研究进展

超级电容器相较于传统储能装置,具有使用寿命长、功率密度高、充放电速率快等优点。赝电容作为超级电容器的重要分支,是一种具有高比功率和能量密度的新型储能器件。综述了赝电容型超级电容器电极材料的储能机制及电化学特性,并对其未来的研究重点和发展方向进行展望。

具有高比电容的纳米Ni-MOF/GO的制备及赝电容特性研究

以不同温度和不同制备时间作为实验条件,采用溶剂热法制备了1#、2#、3#三类Ni-MOF材料。然后,将MOF材料中的3#和氧化石墨烯(GO)等多孔碳材料复合,测得其具有优异的电化学性能。3#在50mA/g时的比电容达700F/g,在500mA/g通过100次循环后仍有电容为222F/g,可保持3#器件初始电容的58.9%以上。3#/GO在500mA/g时表现出412F/g的高质量比电容,并且在100次循环后,保持其初始电容的72%以上。该器件的最大能量密度和最大功率密度分别为11.58Wh/kg和46.32W/kg。通过X射线衍射、X射线光电子能谱技术、比表面积和氮气吸脱附、红外光谱和扫描电子显微镜等测试,证实了GO能显著地改善MOF赝电容的电化学性能。

热处理温度及掺杂对氧化镍电极赝电容器特性的影响

应用电化学阴极沉积法在Ni基片上制得Ni(OH) 2 膜 ,经热处理得到NiO膜 .研究了热处理温度、钴掺杂对NiO膜电极赝电容性能的影响 .结果发现 :在 2 5 0～ 5 0 0℃ ,随着热处理温度的升高 ,NiO膜电极比电容量逐渐减小 ;钴掺杂使比电容量显著增大 .以掺钴的NiO膜为电极 ,以 1mol/L的KOH水溶液为电解质溶液 ,所得电容器的比电容量可达

过渡金属材料的电化学储能性能研究

超级电容器是一种电化学能量储存设备,具有功率密度高、充放电速率快、寿命长等优点.依照反应机理,电化学电容可以区分为双电层电容和赝电容.赝电容超级电容器的能量密度高于双电层电容器.过渡金属氧化物和氢氧化物是一类重要的赝电容器电极材料.为了提高赝电容器的性能,大量的研究工作集中在设计具有特殊结构和尺寸的过渡金属氧化物和氢氧化物电极材料方面.作者综述了电极材料的设计、制备以及性能等方面的研究进展,总结了过渡金属的氧化物和氢氧化物在超级电容器方面的研究与应用.

电化学电容器的设计

电化学电容器是一种介于传统电容器和电池之间的新型元器件,它比传统电容器具有更高比电容量和比能量,比电池具有更高的比功率,具有广泛的应用前景。详细介绍了电化学电容器的分类及设计过程,讨论了电化学电容器设计过程中注意的几个重要问题:结构单元的设计,电极的设计和制备,电极厚度和材料性能,等效串联电阻,电解质,隔膜,电压平衡,装配和封装。

混合型水系超级电容器建模及其参数辨识

论文在深入分析混合型水系超级电容器工作机理的基础上,提出并建立一种可描述其充放电外特性的等效电路模型。首先对混合型水系超级电容器各组成元件进行单独建模;然后综合构成其整体等效电路模型;随后详细讨论了模型参数的辨识方法,推导了参数辨识的模型结构,并采用限定记忆递推最小二乘法辨识模型参数;最后利用实验数据对所建立的模型进行仿真分析和验证。实验和仿真结果证明了本文所建立模型的准确性。

石墨电极电化学活化工艺与准电容特性

通过多种电化学测试技术评价了石墨电极在2.3 mol/L H2SO4溶液中的电化学活化工艺及其准电容性能。结果表明,活化工艺宜采用恒电流阶跃技术,最佳工艺参数为:阳极电流密度为200 m A·cm-2,阴极电流密度为-120 m A·cm-2,对应活化时间分别为300 s和100 s,循环6次。改性后的石墨电极表面形成了多孔、粗糙的三维活性层,单位面积上具有较高的电容量(2.08 F·cm-2)和良好的倍率特性,可作为一种优异的准电容器材料。

电池型电容器─超大容量离子电容器

超大容量离子电容器又称电池型电容器，是一种介于静电电容器与二次电池之间的一种新型储能器件。它具有比静电电容器大得多的能量密度，又有比二次电池大得多的功率密度。适宜于短时大电流放电的情况下工作，可作为电动车辆的启动、制动电源，是解决电动车辆发展的瓶颈。笔者综述了超大容量离子电容器的储能原理、应用以及国内外的研究现状。

非对称型电化学超级电容器的研究进展

非对称型电化学超级电容器是一种介于超级电容器和二次电池之间的新型储能元件,它同时具备超级电容器和二次电池的特性,即高的比能量和比功率、良好的快速充放电能力和循环性能。综述了非对称型电化学超级电容器的工作原理和研究进展。

热处理气氛及掺钴对NiO电极赝电容器性能的影响

在讨论赝电容形成机理的基础上,应用电化学阴极沉积法在Ni基片上制得Ni(OH)2膜,经热处理得到NiO膜。研究发现,Ni(OH)2在空气中热处理所得NiO在KOH水溶液中能形成赝电容,但在N2气氛中热处理所得的NiO在KOH水溶液中未能形成赝电容;钴掺入NiO使比电容量显著增大。

高容量超级电容器电极材料的设计与制备

超级电容器寿命长,安全性高,并可以实现快速充放电,是化学电源研究的热点之一。然而,超级电容器的能量密度较低限制了其更多的应用。因此,超级电容器领域的研究关注点在如何提高超级电容器的能量密度。其中,提高比容量是提高能量密度的一种有效途径。本文通过对电极材料和电解液的优化来研究制备得到高容量超级电容器的方法。电极材料的比表面积、孔道结构和导电性对其电化学性能有着直接的影响。一方面,通过优化电极材料的孔道结构和比表面积可以增加活性位点并提高电解液离子传导率,从而得到高比电容。另一方面,电极材料导电性的提高有利于提升其电子传导率从而得到较高的比容量。本文分别对碳材料和金属氧化物/氢氧化物的优化达到了增加双电层电容和赝电容的目的。不仅如此,还可以通过在电解液中增加氧化还原电对从而得到高比电容。这一方法为高容量超级电容器的制备提供了新的思路。