Hiroaki Hatori

Bio: Hiroaki Hatori is an academic researcher from National Institute of Advanced Industrial Science and Technology. The author has contributed to research in topics: Carbon & Carbon nanotube. The author has an hindex of 32, co-authored 114 publications receiving 6660 citations. Previous affiliations of Hiroaki Hatori include University of Fukui & University of Tokyo.

Shape-engineerable and highly densely packed single-walled carbon nanotubes and their application as super-capacitor electrodes

Abstract: Shape-engineerable and highly densely packed single-walled carbon nanotubes and their application as super-capacitor electrodes

Nitrogen-enriched nonporous carbon electrodes with extraordinary supercapacitance

Abstract: Nitrogen-enriched nonporous carbon materials derived from melamine-mica composites are subjected to ammonia treatment to further increase the nitrogen content. For samples preoxidized prior to the ammonia treatment, the nitrogen content is doubled and is mainly incorporated in pyrol-like groups. The materials are tested as electrodes for supercapacitors, and in acidic or basic electrolytes, the gravimetric capacitance of treat samples is three times higher than that of untreated samples. This represents a tenfold increase of the capacitance per surface area (3300 mu F cm(-2)) in basic electrolyte. Due to the small volume of the carbon materials, high volumetric capacitances are achieved in various electrolytic systems: 280 F cm(-3) in KOH, 152 F CM(-3) in H(2)SO(4), and 92 F cm(-3) in tetraethylammonium tetrafluoroborate/propylene carbonate.

Extracting the full potential of single-walled carbon nanotubes as durable supercapacitor electrodes operable at 4 V with high power and energy density.

Abstract: Supercapacitors are electrochemical energy storage systems that store energy directly and physically as charge, whereas batteries, for example Li-ion cells, store energy in chemical reactants capable of generating charge. [ 1 ] Accordingly, the energy density of supercapacitors ( < 10 Wh kg − 1 ) is lower than batteries ( > 100 Wh kg − 1 ). However, their power is signifi cantly higher and their lifetime longer. As such, supercapacitors are expected to play a crucial role where superior power performance is required. The importance of supercapacitors is highlighted by a report from the US Department of Energy assigning equal importance to batteries and supercapacitors. [ 2 ] Examples of envisioned largescale applications of supercapacitors are load-leveling in solar, wind, and other energy sources and energy recovery from regenerative braking in automobiles. [ 2 , 3 ] To emerge as an important energy storage technology in the future, advanced supercapacitors must be developed with higher operating voltage and higher energy and power delivery, while maintaining high cyclability. Hitherto, activated carbon (AC) has been the electrode material of choice due to its high surface area (1000–2000 m 2

Supercapacitors Prepared from Melamine-Based Carbon

Abstract: The electrochemical performance of supercapacitors made of a carbon material with a moderate amount of nitrogen atoms embedded in a carbon matrix is reported. Melamine was polymerized in the interlayer spaces of mica and afterward carbonized at various temperatures between 650 and 1000 °C. Elemental analysis and an XPS study showed that the nitrogen content of samples stabilized at 250 °C for 4 h prior to carbonization was generally higher if compared to their nonstabilized counterparts and that the nitrogen species were located preferably at the edges of graphene sheets. To understand the relationship between the capacitive performance and the porosity of stabilized and nonstabilized samples, the nitrogen adsorption/desorption method was also employed. Supercapacitors with the electrodes manufactured from these carbon materials showed a very good capacitive performance in 1 M sulfuric acid. The maximum gravimetric specific capacitance of 204.8 F g-1 was obtained from a sample carbonized at 750 °C. Specif...

Electrochemical Performance of Nitrogen-Enriched Carbons in Aqueous and Non-Aqueous Supercapacitors

Abstract: Carbon materials with significant nitrogen contents were investigated as the electrode materials of supercapacitors. The preparation procedure involved the polymerization of melamine in the interlayer space of template fluorine mica and carbonization at 750, 850, and 1000 degrees C. Some samples were also stabilized prior to carbonization. We have shown previously that these carbons possess very interesting capacitive behavior in an acidic medium despite small surface areas. High capacitance values in H2SO4 were attributed to the pseudocapacitive interactions between the protons and nitrogen atoms. This paper further discusses the results obtained in a base and an aprotic electrolyte, KOH and TEABF(4)/PC, respectively. Electrochemical properties were evaluated with cycling voltammetry, a galvanostatic charge/discharge technique, and electrochemical impedance spectroscopy. High capacitance values were obtained in proton-free KOH, and the presence of pseudocapacitive interactions between the ions of the electrolyte and the nitrogen atoms of the carbon matrix is proposed. Compared to those in sulfuric acid, greater capacitances of nonstabilized samples were obtained in KOH, i.e., for the sample carbonized at 1000 degrees C, the capacitance was 84.61 F/g in KOH vs 47.92 F/g in H2SO4. On the other hand, less porous but more nitrogen-rich stabilized samples gave better performances in H2SO4, i.e., 62.24 F/g in H2SO4 compared to 49.86 F/g in KOH for the sample stabilized and carbonized at 1000 degrees C. The sample heat-treated at 750 degrees C with a surface area of ca. 400 m(2)/g performs similarly in both electrolytes, i.e., similar to 200 F/g. Significantly lower gravimetric capacitances were obtained in TEABF(4)/PC from the samples carbonized at 750 degrees C. On the other hand, the almost nonporous sample subjected to stabilization prior to carbonization at 1000 degrees C gave a capacitance of similar to 20 F/g. Hence, we suggest that the faradaic interactions between the carbon electrode material and the electrolyte, although much less significant than those in H2SO4 and KOH, play an important role in the nonaqueous electrolyte as well. Narrow micropores were detected by CO2 adsorption/desorption, and their importance to the interpretation of capacitive behavior is also discussed.

Materials for electrochemical capacitors

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.

A review of electrode materials for electrochemical supercapacitors

Abstract: In this critical review, metal oxides-based materials for electrochemical supercapacitor (ES) electrodes are reviewed in detail together with a brief review of carbon materials and conducting polymers. Their advantages, disadvantages, and performance in ES electrodes are discussed through extensive analysis of the literature, and new trends in material development are also reviewed. Two important future research directions are indicated and summarized, based on results published in the literature: the development of composite and nanostructured ES materials to overcome the major challenge posed by the low energy density of ES (476 references).

Carbon-based materials as supercapacitor electrodes

Abstract: This tutorial review provides a brief summary of recent research progress on carbon-based electrode materials for supercapacitors, as well as the importance of electrolytes in the development of supercapacitor technology. The basic principles of supercapacitors, the characteristics and performances of various nanostructured carbon-based electrode materials are discussed. Aqueous and non-aqueous electrolyte solutions used in supercapacitors are compared. The trend on future development of high-power and high-energy supercapacitors is analyzed.

Carbon-based Supercapacitors Produced by Activation of Graphene

Abstract: Supercapacitors, also called ultracapacitors or electrochemical capacitors, store electrical charge on high-surface-area conducting materials. Their widespread use is limited by their low energy storage density and relatively high effective series resistance. Using chemical activation of exfoliated graphite oxide, we synthesized a porous carbon with a Brunauer-Emmett-Teller surface area of up to 3100 square meters per gram, a high electrical conductivity, and a low oxygen and hydrogen content. This sp 2 -bonded carbon has a continuous three-dimensional network of highly curved, atom-thick walls that form primarily 0.6- to 5-nanometer-width pores. Two-electrode supercapacitor cells constructed with this carbon yielded high values of gravimetric capacitance and energy density with organic and ionic liquid electrolytes. The processes used to make this carbon are readily scalable to industrial levels.

Carbon Nanotubes: Present and Future Commercial Applications

Abstract: Worldwide commercial interest in carbon nanotubes (CNTs) is reflected in a production capacity that presently exceeds several thousand tons per year. Currently, bulk CNT powders are incorporated in diverse commercial products ranging from rechargeable batteries, automotive parts, and sporting goods to boat hulls and water filters. Advances in CNT synthesis, purification, and chemical modification are enabling integration of CNTs in thin-film electronics and large-area coatings. Although not yet providing compelling mechanical strength or electrical or thermal conductivities for many applications, CNT yarns and sheets already have promising performance for applications including supercapacitors, actuators, and lightweight electromagnetic shields.