Author
Atsuo Yamada
Other affiliations: Kyoto University, Toyota, Tokyo Institute of Technology ...read more
Bio: Atsuo Yamada is an academic researcher from University of Tokyo. The author has contributed to research in topics: Electrolyte & Lithium. The author has an hindex of 78, co-authored 444 publications receiving 23989 citations. Previous affiliations of Atsuo Yamada include Kyoto University & Toyota.
Topics: Electrolyte, Lithium, Battery (electricity), Electrode, Thin film
Papers published on a yearly basis
Papers
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TL;DR: LiFePO 4 powders were synthesized under various conditions and the performance of the cathodes was evaluated using coin cells, the samples were characterized by X-ray diffraction, scanning electron microscope observations, Brunauer, Emmett, and Teller surface area measurements, particle-size distribution measurements, and Mossbauer spectroscopy.
Abstract: LiFePO 4 powders were synthesized under various conditions and the performance of the cathodes was evaluated using coin cells, The samples were characterized by X-ray diffraction, scanning electron microscope observations, Brunauer, Emmett, and Teller surface area measurements, particle-size distribution measurements, and Mossbauer spectroscopy. Ab initio calculation was used to confirm the experimental redox potentials and Mossbauer parameters. The choice of a moderate sintering temperature (500°C 95% of the 170 mAh/g theoretical capacity at room temperature. There are two main obstacles to achieving optimum charge/discharge performance of LiFePO 4 : (i) undesirable particle growth at T > 600°C and (ii) the presence of a noncrystalline residual Fe 3+ phase at T < 500°C.
1,698 citations
TL;DR: Enhanced reductive stability of a superconcentrated AN solution is reported and, for the first time, reversible lithium intercalation into a graphite electrode in a reduction-vulnerable AN solvent is demonstrated.
Abstract: The development of a stable, functional electrolyte is urgently required for fast-charging and high-voltage lithium-ion batteries as well as next-generation advanced batteries (e.g., Li–O2 systems). Acetonitrile (AN) solutions are one of the most promising electrolytes with remarkably high chemical and oxidative stability as well as high ionic conductivity, but its low stability against reduction is a critical problem that hinders its extensive applications. Herein, we report enhanced reductive stability of a superconcentrated AN solution (>4 mol dm–3). Applying it to a battery electrolyte, we demonstrate, for the first time, reversible lithium intercalation into a graphite electrode in a reduction-vulnerable AN solvent. Moreover, the reaction kinetics is much faster than in a currently used commercial electrolyte. First-principle calculations combined with spectroscopic analyses reveal that the peculiar reductive stability arises from modified frontier orbital characters unique to such superconcentrated ...
931 citations
TL;DR: The present work demonstrates that the pseudocapacitance of the nanosheet compound MXene Ti2C achieves a higher specific capacity relative to double-layer capacitor electrodes and a higher rate capability relative to ion intercalation electrodes.
Abstract: High-power Na-ion batteries have tremendous potential in various large-scale applications. However, conventional charge storage through ion intercalation or double-layer formation cannot satisfy the requirements of such applications owing to the slow kinetics of ion intercalation and the small capacitance of the double layer. The present work demonstrates that the pseudocapacitance of the nanosheet compound MXene Ti2C achieves a higher specific capacity relative to double-layer capacitor electrodes and a higher rate capability relative to ion intercalation electrodes. By utilizing the pseudocapacitance as a negative electrode, the prototype Na-ion full cell consisting of an alluaudite Na2Fe2(SO4)3 positive electrode and an MXene Ti2C negative electrode operates at a relatively high voltage of 2.4 V and delivers 90 and 40 mAh g(-1) at 1.0 and 5.0 A g(-1) (based on the weight of the negative electrode), respectively, which are not attainable by conventional electrochemical energy storage systems.
882 citations
TL;DR: The progress made and the road ahead for salt-concentrated electrolytes, an emerging and promising electrolyte candidate are reviewed, including a multi-angle analysis of their advantages and disadvantages together with future perspectives.
Abstract: With a worldwide trend towards the efficient use of renewable energies and the rapid expansion of the electric vehicle market, the importance of rechargeable battery technologies, particularly lithium-ion batteries, has steadily increased. In the past few years, a major breakthrough in electrolyte materials was achieved by simply increasing the salt concentration in suitable salt–solvent combinations, offering technical superiority in numerous figures of merit over alternative materials. This long-awaited, extremely simple yet effective strategy can overcome most of the remaining hurdles limiting the present lithium-ion batteries without sacrificing manufacturing efficiency, and hence its impact is now widely felt in the scientific community, with serious potential for industrial development. This Review aims to provide timely and objective information that will be valuable for designing better realistic batteries, including a multi-angle analysis of their advantages and disadvantages together with future perspectives. Emphasis is placed on the pathways to address the remaining technical and scientific issues rather than re-highlighting the many technical advantages. New electrolyte materials can offer breakthroughs in the development of next-generation batteries. Here Atsuo Yamada and colleagues review the progress made and the road ahead for salt-concentrated electrolytes, an emerging and promising electrolyte candidate.
829 citations
TL;DR: Long-awaited experimental evidence for a curved one-dimensional chain for lithium motion is provided by combining high-temperature powder neutron diffraction and the maximum entropy method, lithium distribution along the [010] direction was clearly visualized.
Abstract: Chemical energy storage using batteries will become increasingly important for future environmentally friendly ('green') societies. The lithium-ion battery is the most advanced energy storage system, but its application has been limited to portable electronics devices owing to cost and safety issues. State-of-the-art LiFePO4 technology as a new cathode material with surprisingly high charge-discharge rate capability has opened the door for large-scale application of lithium-ion batteries such as in plug-in hybrid vehicles. The scientific community has raised the important question of why a facile redox reaction is possible in the insulating material. Geometric information on lithium diffusion is essential to understand the facile electrode reaction of LixFePO4 (0
661 citations
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TL;DR: The battery systems reviewed here include sodium-sulfur batteries that are commercially available for grid applications, redox-flow batteries that offer low cost, and lithium-ion batteries whose development for commercial electronics and electric vehicles is being applied to grid storage.
Abstract: The increasing interest in energy storage for the grid can be attributed to multiple factors, including the capital costs of managing peak demands, the investments needed for grid reliability, and the integration of renewable energy sources. Although existing energy storage is dominated by pumped hydroelectric, there is the recognition that battery systems can offer a number of high-value opportunities, provided that lower costs can be obtained. The battery systems reviewed here include sodium-sulfur batteries that are commercially available for grid applications, redox-flow batteries that offer low cost, and lithium-ion batteries whose development for commercial electronics and electric vehicles is being applied to grid storage.
11,144 citations
TL;DR: The semiconductor ZnO has gained substantial interest in the research community in part because of its large exciton binding energy (60meV) which could lead to lasing action based on exciton recombination even above room temperature.
Abstract: The semiconductor ZnO has gained substantial interest in the research community in part because of its large exciton binding energy (60meV) which could lead to lasing action based on exciton recombination even above room temperature. Even though research focusing on ZnO goes back many decades, the renewed interest is fueled by availability of high-quality substrates and reports of p-type conduction and ferromagnetic behavior when doped with transitions metals, both of which remain controversial. It is this renewed interest in ZnO which forms the basis of this review. As mentioned already, ZnO is not new to the semiconductor field, with studies of its lattice parameter dating back to 1935 by Bunn [Proc. Phys. Soc. London 47, 836 (1935)], studies of its vibrational properties with Raman scattering in 1966 by Damen et al. [Phys. Rev. 142, 570 (1966)], detailed optical studies in 1954 by Mollwo [Z. Angew. Phys. 6, 257 (1954)], and its growth by chemical-vapor transport in 1970 by Galli and Coker [Appl. Phys. ...
10,260 citations
TL;DR: This paper will describe lithium batteries in more detail, building an overall foundation for the papers that follow which describe specific components in some depth and usually with an emphasis on the materials behavior.
Abstract: In the previous paper Ralph Brodd and Martin Winter described the different kinds of batteries and fuel cells. In this paper I will describe lithium batteries in more detail, building an overall foundation for the papers that follow which describe specific components in some depth and usually with an emphasis on the materials behavior. The lithium battery industry is undergoing rapid expansion, now representing the largest segment of the portable battery industry and dominating the computer, cell phone, and camera power source industry. However, the present secondary batteries use expensive components, which are not in sufficient supply to allow the industry to grow at the same rate in the next decade. Moreover, the safety of the system is questionable for the large-scale batteries needed for hybrid electric vehicles (HEV). Another battery need is for a high-power system that can be used for power tools, where only the environmentally hazardous Ni/ Cd battery presently meets the requirements. A battery is a transducer that converts chemical energy into electrical energy and vice versa. It contains an anode, a cathode, and an electrolyte. The anode, in the case of a lithium battery, is the source of lithium ions. The cathode is the sink for the lithium ions and is chosen to optimize a number of parameters, discussed below. The electrolyte provides for the separation of ionic transport and electronic transport, and in a perfect battery the lithium ion transport number will be unity in the electrolyte. The cell potential is determined by the difference between the chemical potential of the lithium in the anode and cathode, ∆G ) -EF. As noted above, the lithium ions flow through the electrolyte whereas the electrons generated from the reaction, Li ) Li+ + e-, go through the external circuit to do work. Thus, the electrode system must allow for the flow of both lithium ions and electrons. That is, it must be both a good ionic conductor and an electronic conductor. As discussed below, many electrochemically active materials are not good electronic conductors, so it is necessary to add an electronically conductive material such as carbon * To whom correspondence should be addressed. Phone and fax: (607) 777-4623. E-mail: stanwhit@binghamton.edu. 4271 Chem. Rev. 2004, 104, 4271−4301
5,475 citations
TL;DR: In this paper, the authors report the feasibility to approach such capacities by creating highly ordered interwoven composites, where conductive mesoporous carbon framework precisely constrains sulphur nanofiller growth within its channels and generates essential electrical contact to the insulating sulphur.
Abstract: The Li-S battery has been under intense scrutiny for over two decades, as it offers the possibility of high gravimetric capacities and theoretical energy densities ranging up to a factor of five beyond conventional Li-ion systems. Herein, we report the feasibility to approach such capacities by creating highly ordered interwoven composites. The conductive mesoporous carbon framework precisely constrains sulphur nanofiller growth within its channels and generates essential electrical contact to the insulating sulphur. The structure provides access to Li+ ingress/egress for reactivity with the sulphur, and we speculate that the kinetic inhibition to diffusion within the framework and the sorption properties of the carbon aid in trapping the polysulphides formed during redox. Polymer modification of the carbon surface further provides a chemical gradient that retards diffusion of these large anions out of the electrode, thus facilitating more complete reaction. Reversible capacities up to 1,320 mA h g(-1) are attained. The assembly process is simple and broadly applicable, conceptually providing new opportunities for materials scientists for tailored design that can be extended to many different electrode materials.
5,151 citations
TL;DR: In this article, a review of the key technological developments and scientific challenges for a broad range of Li-ion battery electrodes is presented, and the potential/capacity plots are used to compare many families of suitable materials.
5,057 citations