Kouji Maeda

We found that an AAA-type battery (min. 750 mAh) pressurized with Ar or N₂ at pressures of up to 5 MPa exhibited a significant durability enhancement even under high-current conditions.

<title>Abstract</title> A nickel-metal hydride (Ni–MH) prototype battery completely immersed in an aqueous electrolyte solution of KOH under high pressure was fabricated to examine the effects of high pressure on the quality of Ni–MH batteries. The small battery cell comprised positive and negative electrode materials, as used in electric vehicles, and an Ag/AgO reference electrode. The electric capacity of the Ni–MH battery was measured at different temperatures and pressures with small currents and charge/discharge voltages of 1.6 – 1.0 V. High pressures were found to clearly and effectively enhance the electric capacity of the Ni–MH battery at larger currents. The considerable effect of high pressure on the Ni–MH battery was elucidated by the change in internal resistance during the charge/discharge cycle life experiment, indicating that the voltage of the positive electrode did not appreciably change at a high pressure compared to that of the negative electrode. Moreover, the use of large currents in rapid charge/discharge cycle tests at high pressures of up to 30 MPa resulted in charge/discharge cycles that were five times faster and a quick recovery of capacity was achieved in the 0.5 – 2.1 V range.

The major marine resources are electrolytes, and they are mainly dissolved as ions. More than 70 wt% of electrolytes are sodium chloride, but other electrolytes are also dissolved in seawater. To develop a separation or recovery of electrolytes in seawater, we discussed the electrolyte solution model applied to several electrolytes in seawater. The electrolyte NRTL (Non-Random Two Liquid model) for activity coefficient can be applied to multicomponent systems. Twelve solubility data of two-component systems (water + one electrolyte) are correlated by the solubility product function with the electrolyte NRTL model, and we determined the parameters of solubility products. Some solubility data of three-component systems (water + two electrolytes) were compared to the predicted solubility by electrolyte NRTL model.