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Xiaogang Zhang - One of the best experts on this subject based on the ideXlab platform.

  • Pseudocapacitive materials for Electrochemical Capacitors: From rational synthesis to capacitance optimization
    National Science Review, 2017
    Co-Authors: Jie Wang, Shengyang Dong, Xiaodong Hao, Hui Dou, Bing Ding, Ya Wang, Yongyao Xia, Xiaogang Zhang
    Abstract:

    Among various energy-storage devices, Electrochemical Capacitors (ECs) are prominent power provision but show relatively low energy density. One way to increase the energy density of ECs is to move from carbon-based electric double-layer Capacitors to pseudoCapacitors, which manifest much higher capacitance. However, compared with carbon materials, the pseudocapacitive electrodes suffer from high resistance for electron and/or ion transfer, significantly restricting their capacity, rate capability and cyclability. Rational design of electrode materials offers opportunities to optimize their Electrochemical performance, leading to devices with high energy density while maintaining high power density. This paper reviews the different approaches of electrodes striving to advance the energy and power density of ECs.

  • template engaged synthesis of uniform mesoporous hollow nico2o4 sub microspheres towards high performance Electrochemical Capacitors
    RSC Advances, 2013
    Co-Authors: Changzhou Yuan, Linrui Hou, Jingdong Lin, Gang Pang, Longhai Zhang, Lin Lian, Xiaogang Zhang
    Abstract:

    An efficient template-engaged synthetic strategy, where silica spheres were applied as hard templates, was developed to synthesize hierarchical mesoporous hollow NiCo2O4 sub-microspheres assembled entirely from ultrathin nanosheets with a thickness of a few nanometers. The as-prepared mesoporous hollow NiCo2O4 sub-microspheres are very uniform in size, mesoporous in textual property, and structurally robust benefiting from the in situ template removal. The morphologies of the hollow sub-microspherical architecture can be tuned easily by varying the concentrations of Ni2+, Co2+, and the precipitant. When evaluated as an appealing electroactive material for Electrochemical Capacitors (ECs), the as-fabricated hierarchical hollow NiCo2O4 sub-microspheres delivered a specific capacitance (SC) of 678 F g−1 at a current density of 1 A g−1, and even kept it as high as 540 F g−1 at 10 A g−1. Additionally, a desirable cycling stability of 13% SC degradation over 3500 continuous cycles at a current density of 10 A g−1 is observed, suggesting their promising application in advanced ECs.

  • flexible films derived from electrospun carbon nanofibers incorporated with co3o4 hollow nanoparticles as self supported electrodes for Electrochemical Capacitors
    Advanced Functional Materials, 2013
    Co-Authors: Fang Zhang, Xiaogang Zhang, Jie Wang, Changzhou Yuan, Jiajia Zhu, Xiong Wen David Lou
    Abstract:

    Flexible porous films are prepared from electrospun carbon nanofibers (CNFs) embedded with Co3O4 hollow nanoparticles (NPs) and are directly applied as self-supported electrodes for high-performance Electrochemical Capacitors. Uniform Co3O4 hollow NPs are well dispersed and/or embedded into each CNF with desirable electrical conductivity. These Co3O4-CNFs intercross each other and form 3D hierarchical porous hybrid films. Benefiting from intriguing structural features, the unique binder-free Co3O4 hollow NPs/CNF hybrid film electrodes exhibit high specific capacitance (SC), excellent rate capability and cycling stability. As an example, the flexible hybrid film with loading of 35.9 wt% Co3O4 delivers a SC of 556 F g−1 at a current density of 1 A g−1, and 403 F g−1 even at a very high current density of 12 A g−1. Remarkably, almost no decay in SC is found after continuous charge/discharge cycling for 2000 cycles at 4 A g−1. This exceptional Electrochemical performance makes such novel self-supported Co3O4-CNFs hybrid films attractive for high-performance Electrochemical Capacitors.

  • uniform urchin like nickel cobaltite microspherical superstructures constructed by one dimension nanowires and their application for Electrochemical Capacitors
    Electrochimica Acta, 2012
    Co-Authors: Linrui Hou, Changzhou Yuan, Long Yang, Xiaogang Zhang
    Abstract:

    Abstract A novel two-step synthetic strategy was proposed to synthesize urchin-like nickel cobaltite (NiCo2O4) microspherical hierarchical superstructures constructed by one-dimension nanowires: hydrothermal precipitating (Ni, Co) carbonate hydroxide followed by calcinating process. Electrochemical data reveals that the as-synthesized urchin-like NiCo2O4 superstructures can deliver a specific capacitance (SC) of 296 F/g at 1 A/g, and keep it as high as 215 F/g at 5 A/g in 6 M KOH aqueous solution. Such unique urchin-like hierarchical superstructures make each electroactive NiCo2O4 nanowire building block contacted easily by electrolyte ions and electrons at high rates, ensuring that sufficient Faradaic reactions take place at large current densities for energy storage. Moreover, no obvious SC degradation after 1000 continuous charge–discharge cycles at 2 A/g demonstrates good Electrochemical stability of the urchin-like microspherical superstructures, promising their great potential application in Electrochemical Capacitors.

  • facile template free synthesis of ultralayered mesoporous nickel cobaltite nanowires towards high performance Electrochemical Capacitors
    Journal of Materials Chemistry, 2012
    Co-Authors: Changzhou Yuan, Linrui Hou, Long Yang, Laifa Shen, Xiaogang Zhang
    Abstract:

    In this work, we proposed a facile and scalable template-free strategy to synthesize one-dimensional (1D) ultralayered mesoporous nickel cobaltite (NiCo2O4) nanowires (NWs), which are constructed from lots of quasi-single-crystalline NiCo2O4 nanosheet building blocks. The unique ultralayered mesoporous nanowire electrode exhibited high specific capacitance (401 F g−1 at 1 A g−1), good rate capability (75% capacity retention at 8 A g−1) and excellent cycling stability (only ca. 10% loss after 5000 cycles), exhibiting its great potential application in high-performance Electrochemical Capacitors as an advanced electrode material. The desirable capacitive performance is mainly attributed to its binary electroactive sites of Co and Ni species, and its intriguing ultralayered mesoporous NWs features.

Changzhou Yuan - One of the best experts on this subject based on the ideXlab platform.

  • template engaged synthesis of uniform mesoporous hollow nico2o4 sub microspheres towards high performance Electrochemical Capacitors
    RSC Advances, 2013
    Co-Authors: Changzhou Yuan, Linrui Hou, Jingdong Lin, Gang Pang, Longhai Zhang, Lin Lian, Xiaogang Zhang
    Abstract:

    An efficient template-engaged synthetic strategy, where silica spheres were applied as hard templates, was developed to synthesize hierarchical mesoporous hollow NiCo2O4 sub-microspheres assembled entirely from ultrathin nanosheets with a thickness of a few nanometers. The as-prepared mesoporous hollow NiCo2O4 sub-microspheres are very uniform in size, mesoporous in textual property, and structurally robust benefiting from the in situ template removal. The morphologies of the hollow sub-microspherical architecture can be tuned easily by varying the concentrations of Ni2+, Co2+, and the precipitant. When evaluated as an appealing electroactive material for Electrochemical Capacitors (ECs), the as-fabricated hierarchical hollow NiCo2O4 sub-microspheres delivered a specific capacitance (SC) of 678 F g−1 at a current density of 1 A g−1, and even kept it as high as 540 F g−1 at 10 A g−1. Additionally, a desirable cycling stability of 13% SC degradation over 3500 continuous cycles at a current density of 10 A g−1 is observed, suggesting their promising application in advanced ECs.

  • flexible films derived from electrospun carbon nanofibers incorporated with co3o4 hollow nanoparticles as self supported electrodes for Electrochemical Capacitors
    Advanced Functional Materials, 2013
    Co-Authors: Fang Zhang, Xiaogang Zhang, Jie Wang, Changzhou Yuan, Jiajia Zhu, Xiong Wen David Lou
    Abstract:

    Flexible porous films are prepared from electrospun carbon nanofibers (CNFs) embedded with Co3O4 hollow nanoparticles (NPs) and are directly applied as self-supported electrodes for high-performance Electrochemical Capacitors. Uniform Co3O4 hollow NPs are well dispersed and/or embedded into each CNF with desirable electrical conductivity. These Co3O4-CNFs intercross each other and form 3D hierarchical porous hybrid films. Benefiting from intriguing structural features, the unique binder-free Co3O4 hollow NPs/CNF hybrid film electrodes exhibit high specific capacitance (SC), excellent rate capability and cycling stability. As an example, the flexible hybrid film with loading of 35.9 wt% Co3O4 delivers a SC of 556 F g−1 at a current density of 1 A g−1, and 403 F g−1 even at a very high current density of 12 A g−1. Remarkably, almost no decay in SC is found after continuous charge/discharge cycling for 2000 cycles at 4 A g−1. This exceptional Electrochemical performance makes such novel self-supported Co3O4-CNFs hybrid films attractive for high-performance Electrochemical Capacitors.

  • uniform urchin like nickel cobaltite microspherical superstructures constructed by one dimension nanowires and their application for Electrochemical Capacitors
    Electrochimica Acta, 2012
    Co-Authors: Linrui Hou, Changzhou Yuan, Long Yang, Xiaogang Zhang
    Abstract:

    Abstract A novel two-step synthetic strategy was proposed to synthesize urchin-like nickel cobaltite (NiCo2O4) microspherical hierarchical superstructures constructed by one-dimension nanowires: hydrothermal precipitating (Ni, Co) carbonate hydroxide followed by calcinating process. Electrochemical data reveals that the as-synthesized urchin-like NiCo2O4 superstructures can deliver a specific capacitance (SC) of 296 F/g at 1 A/g, and keep it as high as 215 F/g at 5 A/g in 6 M KOH aqueous solution. Such unique urchin-like hierarchical superstructures make each electroactive NiCo2O4 nanowire building block contacted easily by electrolyte ions and electrons at high rates, ensuring that sufficient Faradaic reactions take place at large current densities for energy storage. Moreover, no obvious SC degradation after 1000 continuous charge–discharge cycles at 2 A/g demonstrates good Electrochemical stability of the urchin-like microspherical superstructures, promising their great potential application in Electrochemical Capacitors.

  • facile template free synthesis of ultralayered mesoporous nickel cobaltite nanowires towards high performance Electrochemical Capacitors
    Journal of Materials Chemistry, 2012
    Co-Authors: Changzhou Yuan, Linrui Hou, Long Yang, Laifa Shen, Xiaogang Zhang
    Abstract:

    In this work, we proposed a facile and scalable template-free strategy to synthesize one-dimensional (1D) ultralayered mesoporous nickel cobaltite (NiCo2O4) nanowires (NWs), which are constructed from lots of quasi-single-crystalline NiCo2O4 nanosheet building blocks. The unique ultralayered mesoporous nanowire electrode exhibited high specific capacitance (401 F g−1 at 1 A g−1), good rate capability (75% capacity retention at 8 A g−1) and excellent cycling stability (only ca. 10% loss after 5000 cycles), exhibiting its great potential application in high-performance Electrochemical Capacitors as an advanced electrode material. The desirable capacitive performance is mainly attributed to its binary electroactive sites of Co and Ni species, and its intriguing ultralayered mesoporous NWs features.

  • flexible hybrid paper made of monolayer co3o4 microsphere arrays on rgo cnts and their application in Electrochemical Capacitors
    Advanced Functional Materials, 2012
    Co-Authors: Xiaogang Zhang, Changzhou Yuan, Long Yang, Laifa Shen, Jiaoyang Li, Xiangjun Lu, Shenglin Xiong
    Abstract:

    A facile one-step hydrothermal method is developed for large-scale production of well-designed flexible and free-standing Co3O4/reduced graphene oxide (rGO)/carbon nanotubes (CNTs) hybrid paper as an electrode for Electrochemical Capacitors. Densely packed unique Co3O4 monolayer microsphere arrays uniformly cover the surface of the rGO/CNTs film. The alkaline hydrothermal treatment leads to not only the deposition of Co3O4 microspheres array, but also the reduction of the GO sheets at the same time. The unique hybrid paper is evaluated as an electrode for Electrochemical Capacitors without any ancillary materials. It is found that the obtained hybrid flexible paper, composed of Co3O4 microsphere array anchored to the underling conductive rGO/CNTs substrate with robust adhesion, is able to deliver high specific capacitance with excellent Electrochemical stability even at high current densities, suggesting its promising application as an efficient electrode material for Electrochemical Capacitors.

J P Zheng - One of the best experts on this subject based on the ideXlab platform.

  • theoretical energy density for Electrochemical Capacitors with intercalation electrodes
    Journal of The Electrochemical Society, 2005
    Co-Authors: J P Zheng
    Abstract:

    Theoretical energy density for Electrochemical Capacitors with intercalation electrodes is applied to carbon electrodes having the ability for Electrochemical intercalation of ions. Energy density theory was applied to these Capacitors and demonstrated that energy densities are 70-114 Wh/kg based on electrode material only, 14-30 Wh/kg based on electrode material and electrolyte, 8-20 Wh/kg based on electrode material, electrolyte, and separator paper, and 7-15 Wh/kg for a packed capacitor. The volumetric energy densities are also estimated. The influences of capacitor operational voltage, electrode material specific capacitance, and electrolyte ion concentration were discussed.

  • The Limitations of Energy Density for Electrochemical Capacitors
    Journal of The Electrochemical Society, 1997
    Co-Authors: J P Zheng
    Abstract:

    Electrochemical Capacitors can be divided into two types depending on whether the salt concentration in the electrolyte changes during charging and discharging. In the first type of capacitor, such as double-layer Capacitors, the salt concentration in the electrolyte reduces during the charging of the capacitor. The maximum energy density of this type of capacitor will depend not only on the specific capacitance and the operating voltage, but also on the salt concentration of the electrolyte. In this paper, a formula describing the dependence of energy density on specific capacitance, operating voltage, and salt concentration is given based on the optimized weight (or volune) ratio of the electrode material and the electrolyte. It shows that for Electrochemical Capacitors using nonaqueous electrolytes, the maximum energy density of the capacitor will be limited mainly by the low salt concentrations of the electrolyte. The relationship between the energy density and the mass density of the electrode is also given. The optimum mass density of the electrode can be obtained based on the value of the theoretical energy density for Capacitors with different electrolytes. In the second type of capacitor, such as pseudoCapacitors with metal oxide electrodes, the salt concentration in the electrolyte remains constant during charging and discharging. The maximum energy denisty of this type of capacitor will be limited mainly by specific capacitance and operating voltage.

  • high energy and high power density Electrochemical Capacitors
    Journal of Power Sources, 1996
    Co-Authors: J P Zheng, T R Jow
    Abstract:

    Abstract High energy density Electrochemical Capacitors were built with a newly discovered electrode material (amorphous RuO 2 · x H 2 O). Energy densities as high as 96 J/g (26 Wh/kg) were obtained based on the RuO 2 · x H 2 O electrode material alone. However, the power density of the capacitor is low. By mixing RuO 2 · x H 2 O powders with about 20% weight of carbon black, power densities greater than 10 kW/kg could be achieved at a delivered energy density of about 72 J/g (20 Wh/kg). Capacitance as a function of cycle life was studied for up to 60 000 cycles. The temperature dependence of capacitance and resistance of the capacitor are also reported in this paper.

  • a new charge storage mechanism for Electrochemical Capacitors
    Journal of The Electrochemical Society, 1995
    Co-Authors: J P Zheng
    Abstract:

    The hydrous form of ruthenium oxide (RuO[sub 2][center dot]xH[sub 2]O) has been demonstrated to be an excellent electrode material for Electrochemical Capacitors. This material, as prepared by a sol-gel process at low temperatures, is amorphous and electrically conductive. The specific capacitance is over 720 F/g. This value is at least two times higher than the highest value ever reported for such materials. The charge storage mechanism is believed to involve bulk Electrochemical protonation of the oxide. This discovery opens a new avenue of research in the field of high energy density Electrochemical Capacitors.

Yury Gogotsi - One of the best experts on this subject based on the ideXlab platform.

  • mxene polymer hybrid materials for flexible ac filtering Electrochemical Capacitors
    Joule, 2019
    Co-Authors: Girish S Gund, Yury Gogotsi, Jeong Hee Park, Rana Harpalsinh, Manikantan Kota, Joo Hwan Shin, Taeil Kim, Ho Seok Park
    Abstract:

    Summary Energy storage devices are limited by the trade-off between the transport properties and charge storage ability of materials. Electrolytic Capacitors are kinetically fast, operating at kilohertz frequency, but limited by low capacitance. Electrochemical Capacitors (ECs) provide high capacitance, yet their sluggish kinetics limit frequency response to a few hertz. Here, we devise strongly interacting, porous MXene/conducting polymer hybrids for large-scale flexible alternating current filtering symmetric ECs with high areal and volumetric capacitances of 0.56 mF cm−2 and 24.2 F cm−3 at 120 Hz, respectively. The high capacitance was maintained up to 1,000 V s−1 and originates from synergy of MXene/polymer hybrids. The operation of tandem ECs that filter a pulsating voltage from 60 to 10,000 Hz is demonstrated with device flexibility and durability over 30,000 cycles. These MXene hybrid-based ECs are expected to bridge the performance gap between high capacitance and the high-frequency response toward the form-factor-free miniature and scalable devices.

  • high density freestanding graphene carbide derived carbon film electrodes for Electrochemical Capacitors
    Carbon, 2017
    Co-Authors: Mohamed Alhabeb, Majid Beidaghi, Katherine L Van Aken, Boris Dyatkin, Yury Gogotsi
    Abstract:

    Abstract Freestanding films of reduced graphene oxide (rGO) have attracted much attention as electrodes for Electrochemical Capacitors, especially for flexible device applications. Here, for the first time, we report binder-free supercapacitor electrodes made of highly porous carbide-derived carbon (CDC) nanoparticles as spacers between thermally reduced graphene oxide (rGO) sheets. The addition of CDC between the rGO layers increases the wettability and accessibility of active material to the electrolyte ions, which improves Electrochemical performance. The resulting electrodes exhibit high capacitance of over 210 F/g, high power densities at 100 mV/s and 10 A/g charge/discharge rates, and long stability of over 10,000 cycles in an aqueous electrolyte. Moreover, hybrid rGO/CDC electrodes, in contrast to solely rGO-based counterparts, maintained high gravimetric capacitance as the electrode thickness increased from 5 μm to ∼50 μm. This hybrid electrode material design is greatly viable in high-power energy storage devices.

  • highly porous carbon spheres for Electrochemical Capacitors and capacitive flowable suspension electrodes
    Carbon, 2014
    Co-Authors: Majid Beidaghi, Boris Dyatkin, Chuanfang Zhang, Kelsey B Hatzell, Muhammad Boota, Donghui Long, Wenming Qiao, E C Kumbur, Yury Gogotsi
    Abstract:

    Abstract In flowable and conventional Electrochemical Capacitors, the energy capacity is largely determined by the electrode material. Spherical active material, with high specific surface area (SSA) represents a promising material candidate for film and flow Capacitors. In this study, we synthesized highly porous carbon spheres (CSs) of submicrometer size to investigate their performance in film and suspension electrodes. In particular, we studied the effects of carbonization and activation temperatures on the Electrochemical performance of the CSs. The CSs activated at optimum conditions demonstrated narrow pore size distribution (

  • materials for Electrochemical Capacitors
    Nature Materials, 2008
    Co-Authors: Patrice Simon, Yury Gogotsi
    Abstract:

    The aim of this chapter is threefold. First of all, we will attempt to briefly highlight the differences between batteries and Electrochemical Capacitors (ECs), describe the general types of ECs (symmetric and asymmetric configurations), and present the Electrochemical tools that are available to characterize these systems. Second, an EC is a complex device with many components (current collector, separator, active materials, external management electronics) and design features that ultimately determine the device characteristics. However, the advances in performance for future ECs that will be required for their broader implementation as an energy-storage technology will largely depend on new developments in electrode materials and electrolytes, which will be the focus of this chapter. Thus, this chapter will attempt to present a critical assessment of the materials that are currently being used and developed for hybrid ECs. Third, some current applications of ECs will be described in details and will clearly demonstrate that hybrid ECs are no longer a scientific curiosity and that they have found their place as energy-storage systems due to their unique characteristics. Finally, this chapter will be concluded by a section that presents the major role ECs will be playing in the field of energy storage and conservation.

  • Materials for Electrochemical Capacitors
    Nature Materials, 2008
    Co-Authors: Patrice Simon, Yury Gogotsi
    Abstract:

    Electrochemical Capacitors, also called superCapacitors, store energy using either ion adsorption (Electrochemical double layer Capacitors) or fast surface redox reactions (pseudo-Capacitors). They can complement or replace batteries in electrical energy storage and harvesting applications, when high power delivery or uptake is needed. A notable improvement in performance has been achieved through recent advances in understanding charge storage mechanisms and the development of advanced nanostructured materials. The discovery that ion desolvation occurs in pores smaller than the solvated ions has led to higher capacitance for Electrochemical double layer Capacitors using carbon electrodes with subnanometre pores, and opened the door to designing high-energy density devices using a variety of electrolytes. Combination of pseudo-capacitive nanomaterials, including oxides, nitrides and polymers, with the latest generation of nanostructured lithium electrodes has brought the energy density of Electrochemical Capacitors closer to that of batteries. The use of carbon nanotubes has further advanced micro-Electrochemical Capacitors, enabling flexible and adaptable devices to be made. Mathematical modelling and simulation will be the key to success in designing tomorrow's high-energy and high-power devices.

Patrice Simon - One of the best experts on this subject based on the ideXlab platform.

  • materials for Electrochemical Capacitors
    Nature Materials, 2008
    Co-Authors: Patrice Simon, Yury Gogotsi
    Abstract:

    The aim of this chapter is threefold. First of all, we will attempt to briefly highlight the differences between batteries and Electrochemical Capacitors (ECs), describe the general types of ECs (symmetric and asymmetric configurations), and present the Electrochemical tools that are available to characterize these systems. Second, an EC is a complex device with many components (current collector, separator, active materials, external management electronics) and design features that ultimately determine the device characteristics. However, the advances in performance for future ECs that will be required for their broader implementation as an energy-storage technology will largely depend on new developments in electrode materials and electrolytes, which will be the focus of this chapter. Thus, this chapter will attempt to present a critical assessment of the materials that are currently being used and developed for hybrid ECs. Third, some current applications of ECs will be described in details and will clearly demonstrate that hybrid ECs are no longer a scientific curiosity and that they have found their place as energy-storage systems due to their unique characteristics. Finally, this chapter will be concluded by a section that presents the major role ECs will be playing in the field of energy storage and conservation.

  • Electrochemical Capacitors for energy management
    Science, 2008
    Co-Authors: John R Miller, Patrice Simon
    Abstract:

    Rapid storage and efficient delivery of electrical energy in heavy-duty applications are being enabled by Electrochemical Capacitors.

  • new materials and new configurations for advanced Electrochemical Capacitors
    The Electrochemical Society interface, 2008
    Co-Authors: Katsuhiko Naoi, Patrice Simon
    Abstract:

    Today, Electrochemical Capacitors (ECs) have the potential to emerge as a promising energy storage technology. The weakness of EC systems is certainly the limited energy density, which restricts applications to power delivery over only few seconds. As a consequence, many research efforts are focused on designing new materials to improve energy and power densities. These are reviewed below.

  • Materials for Electrochemical Capacitors
    Nature Materials, 2008
    Co-Authors: Patrice Simon, Yury Gogotsi
    Abstract:

    Electrochemical Capacitors, also called superCapacitors, store energy using either ion adsorption (Electrochemical double layer Capacitors) or fast surface redox reactions (pseudo-Capacitors). They can complement or replace batteries in electrical energy storage and harvesting applications, when high power delivery or uptake is needed. A notable improvement in performance has been achieved through recent advances in understanding charge storage mechanisms and the development of advanced nanostructured materials. The discovery that ion desolvation occurs in pores smaller than the solvated ions has led to higher capacitance for Electrochemical double layer Capacitors using carbon electrodes with subnanometre pores, and opened the door to designing high-energy density devices using a variety of electrolytes. Combination of pseudo-capacitive nanomaterials, including oxides, nitrides and polymers, with the latest generation of nanostructured lithium electrodes has brought the energy density of Electrochemical Capacitors closer to that of batteries. The use of carbon nanotubes has further advanced micro-Electrochemical Capacitors, enabling flexible and adaptable devices to be made. Mathematical modelling and simulation will be the key to success in designing tomorrow's high-energy and high-power devices.