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The practical realization of rechargeable organic batteries is stalled by their low electron conductivity, which limits the organic-active material content in the electrode composite and results in a low net electrode energy density. Additionally, the dissolution of active materials into the electrolyte causes a short cycle life. In this study, a conductive polymer mixture, poly(3,4-ethylenedioxythiophene)/polystyrenesulfonate, containing a small amount of sugar alcohol was used as the binder and separator in a rechargeable organic battery. Consequently, the active material content was increased up to 80 wt%, and the cycle life was extended.
Novel Mg-Zr-A (A=Na, Li and K) hydrides have been synthesized by the gigapascal hydrogen pressure method. Their crystal structures were analyzed based on synchrotron X-ray diffraction (XRD) patterns. In the Mg-Zr-H system, the Mg-Zr hydride with FCC structure was formed under 8 GPa and 873 K. In the case of Mg-Zr-Li and Mg-Zr-K systems, the quaternary hydrides were formed and these retained the same crystal structure, FCC structure, up to x = 1.0 While in the Mg-Zr-Na system, the quaternary hydrides were formed and these retained the FCC structure, up to x = 0.3. With the addition of 0.5 NaH, a hydride with the Ca7Ge type structure was formed instead of the FCC structure. The Mg-Zr-(Li, Na, K) hydrides can reversibly absorb and desorb hydrogen. The hydrogen desorption temperatures of those hydrides decrease with the increasing ionic radius of the alkali metal.
Compound formation properties of very finely layered Mg/Al laminate composite (“super laminate composite”) were investigated. Almost uniform Mg17Al12 compound was obtained by heat treatment of the super laminate at 673K in less than 0.6ks(10 minutes). The rate control process of the compound formation is thought to be the diffusion of Mg in Al. Hydrogenation properties of thus obtained Mg17Al12 compound were also studied and its absorption capacity and dissociation pressure were almost the same as those previously reported material, which was prepared by a longer time heat treatment.
We have prepared Mg/Pd laminate composites with (Mg/Pd)=6, 3 and 2.5 atom ratios, by a super lamination technique. The homogeneous Mg-Pd intermetallic compounds, Mg6Pd, Mg3Pd and Mg5Pd2, are formed during the initial activation process. We investigated the hydrogen storage properties of these materials. The compounds can reversibly absorb and desorb a large amount of hydrogen, up to 1.46˜0.9 H/M, at 573 K. Except for the Mg5Pd2-hydrogen system, the pressure composition-isotherms show two plateaux. The mechanism of the phase transition during hydrogenation/dehydrogenation was analyzed by in-situ XRD measurements. These intermetallic compounds absorb and desorb hydrogen through reversible multistage disproportionation and recombination processes.
Microstructures and hydrogen storage properties of Mg/Cu super-laminates were compared to clarify the effect of initial activation. The initial activation change micro/nano-structures of Mg/Cu super-laminates into Mg2Cu with layered structure in fine grain size of about 1μm and pores highly dispersed between layers in sub-micrometer size. Large surface area, dense defects and short diffusion distance for the reaction enable Mg/Cu super-laminates to absorb hydrogen very quickly.
Super-laminates have been attracting attention since co-authors Ueda et al. reported that Mg/Cu super-laminates showed reversible hydrogenation and dehydrogenation at 473K. The Mg/Cu super-laminates were prepared by a repetitive fold and roll method. Initial activation at 573 K led the super-laminates to absorb hydrogen at 473K. TEM observations of micro/nano-structures in the super-laminates were performed in order to clarify the process of hydrogenation and dehydrogenation at 473K, The as-rolled Mg/Cu super-laminates have laminated structures in size of sub-micrometer thickness composed of Mg and Cu layers with dense lattice defects. The super-laminates after initial activation keep laminated structure and have uniformly distributed pores with a sub-micrometer diameter. It is considered that these micro/nano-structures of Mg/Cu super-laminates lead to lower dehydrogenation temperature and better kinetics, which would contribute to achieve high performance hydrogen storage materials.
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