ORAL

SESSION: BatteryTueAM-R4	4th Intl. Symp. on Sustainable Secondary Battery Manufacturing and Recycling
Tue Oct, 24 2017	Room: Peninsula 4
Session Chairs: Tetsuya Yamada; Katsuya Teshima; Session Monitor: TBA

11:00: [BatteryTueAM01] Invited
Flux growth of submicron, polyhedron LiCoO2 single crystals and their Li+ transportation nature at high electrochemical load
Tetsuya Yamada¹ ; Nobuyuki Zettsu¹ ; Katsuya Teshima¹ ; ¹Center for Energy & Environmental Science, Shinshu University, Nagano, Japan;
Paper Id: 340 [Abstract]

Development of high-power density battery is one of important issues for managing high-performance energetic applications including electric vehicles, rescue robots, elevating machines, and so on. Lithium cobalt oxide, LiCoO2, is one of the most popular active materials in lithium ion secondary batteries because of exhibiting good conductivities with reasonable capacity. Toward the application of LiCoO2 as high-output uses, there are still some issues to be solved. Usually, LiCoO2 was prepared by solid-state reaction, which provided a few micron-size polycrystals with inhomogeneous distribution in shapes. Under high loading rate, it is presumed that the usual LiCoO2 particles undergo local overcurrent and volume changes during lithiation / delithiation caused by aggregation and inhomogeneous natures of them. Since these electrochemical overloads would lead serious degradation in the cycle abilities, improvements of LiCoO2 are inevitable. There are two kinds of approaches for the improvement. The first one is modification of chemical compositions, including doping with other elements, coating with inactive materials, and the second one is control of crystallographic characteristics, such as crystal habits, particle dispersibility, and sizes. Combining them, synergetic improvement of LiCoO2 toward high-output battery would be possible. Recently, we have grown LiCoO2 single crystals by using flux method, which is one of liquid-phase crystal growth techniques. Exhibiting submicron-size, dispersed, low-aspect ratio with rich a, b faces, and high crystalline natures, which commonly provide efficient electron and Li+ transportations, it is expected that the flux grown LiCoO2 crystals inhibit the unfavorable electrochemical degradations at high electrochemical load. In this report, we applied the flux grown LiCoO2 crystals to the active materials for high-output batteries. The effects of crystallographic characteristics of the LiCoO2 to the battery performances were examined at 10C rate, coupled with their degradation manners in terms of morphologies and chemical phases.

SESSION: BatteryTueAM-R4	4th Intl. Symp. on Sustainable Secondary Battery Manufacturing and Recycling
Tue Oct, 24 2017	Room: Peninsula 4
Session Chairs: Tetsuya Yamada; Katsuya Teshima; Session Monitor: TBA

12:00: [BatteryTueAM03] Invited
Flux growth concept as new approaches to highly crystalline materials: A challenge for next-generation energy devises
Katsuya Teshima¹ ; ¹Center for Energy & Environmental Science, Shinshu University, Nagano, Japan;
Paper Id: 339 [Abstract]

Lithium ion secondary batteries (LIBs) have been extensively studied because of their potential use as power sources in mobile electronics, hybrid-electric vehicles and next-generation electric mobilities. Recently, we are especially focusing on all-crystal (solid)-state LIBs. They have attracted significant attention due to their high energy densities, that is, originating from the device miniaturization, and high safety caused by their non-flammability. However, there is extremely large innovation gap between general LIBs and all-solid-state LIBs because of difficulties in smooth lithium ion transfer, i.e., diffusion of lithium ions and electrons are interfered at interfaces of different solid materials. Therefore, we have tried to control and design their interfaces between active materials and solid electrolytes and fabricate materials for all-solid-state LIBs on the basis of crystal science and engineering. Water-splitting by photocatalysts have been investigated because of expectation to supply clean and recyclable hydrogen energy. In general, photocatalysts, as represented by TiO2, are activated by only ultraviolet light illumination due to their wide band gap. Although these UV-light-driven photocatalysts can split water in a proper condition, the solar energy conversion efficiency is rather low because UV light energy is just several percent in total energy of sun light on the earth, and visible light accounts for almost half of the solar energy. From the viewpoint of increase the efficiency and industrial application of solar hydrogen production, visible-light-driven photocatalysts have intensively attracted research interests. In particular, oxynitride and nitride semiconductor photocatalysts are one of promising materials for construction of photocatalytic water splitting system. Our group has researched a classic flux method for preparing active materials and solid electrolytes for all-solid-state LIBs, and visible-light-driven photocatalysts for solar hydrogen production, and developed flux coating method for fabricating highly crystalline layers on metal collectors. The flux method is a nature-mimetic liquid phase crystal growth technique, and has several advantages over other methods like solid state reaction. It is a relatively low-temperature process that requires very simple equipment, and high-quality crystals with well-developed facets can be grown. The details of materials preparation and interfaces design by use of our flux crystal growth concepts will be presented in the SIPS2017 conference.