The simultaneous measurement of both the relative electrical resistance and the equilibrium hydrogen and deuterium pressure as a function of composition of Pd-H and Pd-D systems have been carried out at temperatures between 273 and 323 K at H 2 (D 2 ) pressures up to about 3.3 MPa. The relative resistance, R/R 0 , in the (α +β) two-phase region for the absorption processes shows a very small and almost linear increase with increasing H(D) content, especially for the Pd-H system, compared to the larger changes previously observed by the electrolysis method. The resistance behaviour is quite similar to the shape of p-c isotherm relationships. The relative resistance increments per unit change of H(D)/Pd content at 298 K, (R/R 0 )/ r, in the (α + β) two-phase region are about 1.5 and 2.1 times larger for the Pd-H and Pd-D systems, respectively, compared to the changes in the relative lattice parameters with H(D)/Pd content, (a/a 0 )/ r, within the two-phase region, where a 0 is the lattice parameter of H(D)-free Pd and r is the atom ratio. On the other hand, the resistance increment in the α single solid solution phase and β single phase, except for the higher-H(D)-content region, is significantly larger compared to the changes of the lattice expansion due to dissolved hydrogen and deuterium. Thus, the variation in resistance with hydrogen and deuterium content in the (α + β) twophase region may be mainly associated with an incoherent formation of β hydride within the α phase. The relative resistance for the subsequent desorption processes from the absorption up to about 3.3 MPa at 298 K in both Pd-H and Pd-D systems exhibits almost the same maximum as that of the absorption processes, i.e. (R/R 0 ) H,max 1.87 at about H/Pd = 0.76 and (R/R 0 ) D,max 2.07 at about D/Pd = 0.75, and then the R/R 0 values decrease gradually with decreasing H(D) content up to the β min phase boundary composition; on entering the (α+β) two-phase region, the R/R 0 values remain almost constant, i.e. (R/R 0 ) (α+β) 1.76 for the Pd-H system and (R/R 0 ) (α+β)1.89 for the Pd-D system. This large hysteresis of resistance can be attributed to the creation of 'lattice strain deformations' accompanied by dislocation formation from β hydride (deuteride) formation and by further highly dissolved hydrogen and deuterium in the β phase region.

The hysteresis behaviour of electrical resistance during the absorption - desorption processes in the -, - and -phase regions of the Pd - H system, respectively, have been investigated at 323 K by a gas-phase method. A small extent of hysteresis in relative electrical resistance over the cyclic absorption - desorption processes in the single-phase region has been observed, showing slightly larger -values for desorption processes than for absorption processes, where is the initial resistance of a hydrogen-free sample. In cyclic desorption - absorption scans commencing from the absorption branch of p - c isotherms in the two-phase plateau region, similar hysteresis loops to those of p - c isotherms have been observed for plots of versus [H]/[Pd]. On the other hand, for cyclic desorption - absorption scans starting from absorption pressures, corresponding to hydrogen concentrations near the -phase boundary composition, -values do not return to those of desorption plateau in the two-phase region. Values of relative resistance over subsequent desorptions from absorption pressures with MPa decrease gradually with decreasing H content down to -phase boundary compositions and exhibit almost the same values as those observed for the absorption processes and, on entering the two-phase region, the -values remain almost constant with decreasing [H]/[Pd], i.e. at at 323 K. The large hysteresis of resistance relationships can be attributed to creations of lattice strains accompanied by dislocation formation arising from -phase hydride transitions and by further highly dissolved hydrogen in the -phase region.

Multivalent-ion rechargeable batteries using calcium ions have an attracted attention as one of next generation batteries. Calcium-ion batteries using a metal negative electrode that does not form dendrites can contribute the twice number of electrons per cation compared with lithium ion, which increase the charge capacity for the specific insertion host. In recent years, the electrochemical stripping and plating of calcium metal has been a report for anode. [1] On the other hand, the calcium insertion hast for cathode active materials such as NiFe(CN)6 [2] and MnFe(CN)6 [3] have been reported. However, their capacity and potential are far from those of lithium-ion battery cathode materials, and there are not so many candidates for cathode active materials. This is because the diffusion of multivalent ions in the inorganic compound is disturbed by a large interaction with cations and anions in the host structure. It is still challenge to improve ionic conduction drastically by the conventional concept and novel material concept is needed. We focused on the fact that, among the calcium compounds using natural products, calcium is contained relatively in green vegetables. Since green vegetables such as Spinach, Malabar spinach, and Komatsuna contain a relatively large amount of calcium and a metal cation, electrochemical insertion / deinsertion of calcium would be realized. Then, new material guideline can be established by analyze the chemical structure for calcium insertion / deinsertion. In this study, we report the electrochemical behavior of Spinach, Malabar spinach, and Komatsuna as active materials. Spinach, Malabar spinach, and Komatsuna were vacuum dried at 75 ℃ and grind in a mortar. The vegetable powder was mixed with acetylene black and PTFE at weight ratio of 75:15:10. The pelletized electrode was pressed between two Ti meshes. The three-electrode cell using Ag / AgCl reference electrode and an activated carbon counter electrode was assembled with 2.5 M Ca(NO3) aqueous electrolyte.CV measurement was performed at the scan rate of 10 mV s-1 with the potential range of -0.8 V to 0.9 V. Figure 1 shows the CV of Spinach, Malabar spinach, and Komatsuna in aqueous Ca(NO3) electrolyte. All samples are swept to cathodic first and then anodic. No distinct reduction peaks were observed, whereas the anodic sweep confirmed the distinct peaks. The anodic peaks were observed around 0.3 V for spinach and malabar spinach, and around 0.5 V for komatsuna. Higher anodic current is observed, particularly in komatsuna which has different chemical species of calcium, and the peak position is shifted towards positive direction. Among the three vegetables, the calcium content is in the order of komatsuna, malabar spinach, spinach, which consists with the order in the peak currents. When this anodic current is assumed to be derived from electrochemical deinsertion of calcium ions, it is estimated that the approximately 30 to 50% of the calcium content is extracted in this reaction. Reference. [1] A. Ponrouch, C. Frontera, F. Bardé and M. R. Palacín, Nature. Mater., 15, 169-172 (2016). [2] T. Tojo et al, Electrochem. Acta., 207, 22-27, (2016) [3] A. L. Lipson et al., Chem. Mater., 27, 8442-47, (2015) Figure 1