MCARE Plenary Speakers
MONDAY, August 20 ¦ 8:30 a.m. ¦ Grand Ballroom A/B
Subhash C. Singhal, Battelle Fellow and Director, Pacific Northwest National Laboratory, USA
Title: High Temperature Solid Oxide Fuel Cells for Clean and Efficient Power Generation
Abstract: Solid oxide fuel cells (SOFCs), based on an oxide ion conducting ceramic electrolyte such as stabilized-zirconia, offer a clean, low-pollution technology to electrochemically generate electricity at high efficiencies. These cells operate between about 550 and 1000oC, and some hydrocarbon fuels such as natural gas can be reformed within the cell stack eliminating the need for an expensive, external reformer. SOFCs offer important advantages over other kinds of fuel cells, notably their ability to use CO or liquid hydrocarbons as fuel, which makes them ideally suited for commercial, residential, portable, and remote military applications. The most important need to commercialize SOFC technology is to significantly reduce the overall cost of SOFC-based power systems, while maintaining adequate performance and performance stability with time. Reduction of cell operation temperature enables use of low-cost metallic interconnects and a decrease in maintenance costs. However, at lower temperatures, greater ohmic loss due to reduced ionic conductivity of the electrolyte and reduced catalytic activity of the electrodes result in lower cell performance. To improve cell performance at lower temperatures, thin electrolyte, nanoscale materials and nano-architectures in the electrodes have recently been considered. However, a crucial question that remains to be answered is whether the beneficial effect of employing nanoscale materials will persist even after long term cell operation at high temperatures, even though the initial performance may have indicated substantial enhancement.
This overview focuses on the materials, processing, and performance of solid oxide fuel cells, with relative advantages/disadvantages of different geometries. Stacks and systems built with both tubular and planar geometries are described and their operating experience discussed. Applications of such cells in different market sectors are reviewed and challenges in reducing cell and system costs are summarized.
TUESDAY, August 21 ¦ 8:30 a.m. ¦ Grand Ballroom A/B
Tsutomu Miyasaka, Professor, Faculty of Biomedical Engineering, Toin University of Yokohama, Japan; Fellow, Research Center for Advanced Science and Technology, University of Tokyo, Japan
Title: Metal oxide-based high efficiency and durable perovskite solar cells: current progress and perspectives
Abstract: Achieving high level of solar power conversion efficiency (PCE >22%) that has exceeded the efficiencies of CIGS and CdTe, perovskite solar cell is required to ensure high durability for practical applications. Although thermal stability of lead halide perovskite materials is determined by their compositions (generally limited to temperature <150oC) and steadily improving, stability of device is highly affected by the kind of carrier transport materials and the quality of interfaces at the perovskite junctions. In perovskite solar cells, all active layers are coated by low cost solution-printing process. Metal oxide electron transport layers (ETLs) generally have advantage in higher thermal stability than organic ETLs. We have been working with TiO2 ETL-based multi-cation perovskite cells, which yielded efficiency over 21% by low cost ambient air solution processes.3 Intensity dependence of their Voc shows ideality factor low enough (<1.4) for the perovskite device to work as a high voltage power source even under weak light. Such merit enables applications of perovskite device not only for outdoor solar panels but also for indoor power device for currently evolving IoT industries. In such respect, lightweight and flexible thin film perovskite solar cells (fabricated on plastic film, see figure) are particularly promising in expanding applications of the device. Perovskite solar cell capable of high voltage output is also candidate for space satellite missions, which needs solar cells to work even under very weak sunlight. We have examined the durability of perovskite solar cells comprising thermally stable FA-based multi-cation perovskite absorber, TiO2 ETL, and P3HT as hole transport layer. On exposure of the cell to high energy electron and proton beams, we found high stability and tolerance of the perovskite cells in space environment, which are superior to those of Si and GaAs solar cells. Focusing on the advantage of lightweight and printable thin film device, future perspectives of perovskite photovoltaic devices will be presented.
WEDNESDAY, August 22 ¦ 8:30 a.m. ¦ Grand Ballroom A/B
Yang-Kook Sun, Professor, Energy Engineering, Hanyang University, Korea
Title: High-Energy Ni-Rich Li[NixCoyMnz]O2 Cathodes via Compositional Partitioning for Next-Generation Electric Vehicles
Abstract: The ability of Li-ion batteries (LIBs) to provide portable high-density energy sources with outstanding cycle life has led to their deployment in recent electric vehicles (EVs). For wider consumer acceptance of EVs, however, the current state-of-the-art LIBs face formidable technological challenges, including concerns related to the battery cost, durability, and driving range. Resolving these hurdles requires substantial improvements in energy density, cycle life, and safety of current LIBs. Compared to the most widely accepted anode, graphite, cathodes suffer from inferior capacity, poor cycle life, thermal characteristics, and high cost. As a result, high-energy cathodes enabling a long cycle life and reliable safety need to be developed. One of the most promising oxides is full concentration gradient (FCG) lithium nickel-cobalt-manganese oxide composed of a Mn-rich outer surface providing excellent safety and Ni-rich center achieving high capacity. We further report a new novel Li[NixCoyMnz]O2 cathode with two-sloped full concentration gradients (TSFCG) of Ni, Co, and Mn ions. The TSFCG delivers a high discharge capacity with excellent cycle life and thermal stability. Comparison of electrochemical and thermal properties of the TSFCG with those of NCA and conventional cathode Li[NixCoyMnz]O2 is presented.
THURSDAY, June 23 ¦ 8:30 a.m. ¦ Grand Ballroom A/B
Hideo Hosono, Professor, Laboratory for Materials and Structures, Institute of Innovative Research, Institute of Technology, JAPAN
Title: Creation of active functionality utilizing abundant elements
Abstract: It is a grand challenge in materials science to realize valuable active functionality using abundant elements. Electron and hydrogen are the simplest and most abundant species in space. Most of functionalities in oxides are obtained by tuning cations. In this talk I introduce our approach to electro-active functionality in oxide-based materials focusing on electron and hydrogen as anions.
Crystals in which electrons serve as anions are called electride, which may be regarded as the crystalline form of solvated electrons. The first electride was synthesized by J.Dye in 1983 using crown-ether. The fatal drawback was extreme sensitivity to temperature and air. It was thus a long standing issue to realize RT-stable electride since then. We reported RT stable electride C12A7:e- in 2003 using 12CaO∙7Al2O3(C12A7). Since then, unique electronic structure and physical properties have been elucidated; insulator-metal-superconductor transition and very low work function (but chemical inertness) are typical examples. In addition, metallic conduction at molten state is found. Recently, we reported two novel findings: Ru-loaded C12A7:e works as efficient ammonia synthesis at mild conditions and 2-dimensinal electride Ca2N and Y2C with exceptional properties.
Another focus is hydrogen anion H– in oxides. We reported the incorporation of H– ions in C12A7 in place of O2- ions and found the UV-induced insulator – electronic conductor conversion. If O2- ion sites are replaced by H– ion, H– would work as an electron donor. This approach has succeeded in heavy electron doping to iron-based superconductor LaFeAsO1-xHx and two Tc-dome structure has been found.