The lithium-ion battery is the most advanced energy storage system, which utilizes an electrode reaction involving reversible lithium intercalation into a solid matrix. The structural and transport properties of these battery materials have been extensively studied as a function of lithium content, and structural/electronic phase diagrams have been revealed for a wide variety of lithium intercalation compounds. Here, we focused on the electrochromic response upon lithium intercalation and discovered distinctive color changes of Li x FePO4, which is recognized as a promising cathode material for large-scale lithium-ion batteries. The emergence of a broad optical absorption band over the visible spectrum with coloring from pale gray to dark green was observed in accordance with the increase of the Fe3+/Fe2+ mixed-valence state and hence the solid–solution compositional domain in the phase diagram of Li x FePO4. The color changes were analyzed using ab initio computational methods and rationalized to the intervalence charge transfer (IVCT) transition and its kinetic activation energy based on Marcus–Hush theory.

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Modification of JT-60 as a full superconducting tokamak (JT-60SC) is planned. The objectives of the JT-60SC programme are to establish scientific and technological bases for steady-state operation of high performance plasmas and utilization of reduced-activation materials in an economically and environmentally attractive DEMO reactor. Advanced fusion technologies relevant to the DEMO reactor have been developed for the superconducting magnet technology and plasma facing components of the JT-60SC design. To achieve a high current density in a superconducting strand, Nb 3 Al strands with a high copper ratio of 4 have been newly developed for the toroidal field coils (TFCs) of JT-60SC. The R&D to demonstrate the applicability of the Nb 3 Al conductor to TFCs by a react-and-wind technique has been carried out using a full-size Nb 3 Al conductor. A full-size NbTi conductor with low ac loss using Ni-coated strands has been successfully developed. A forced cooling divertor component with high heat transfer using screw tubes has been developed for the first time. The heat removal performance of the carbon fibre composite target was successfully demonstrated on an electron beam irradiation stand.