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We fabricated prismatic lithium-ion cells with a LiFePO 4 -based cathode material and examined the long-term cyclability and high thermal stability of the LiFePO 4 in the cells to support the application of this material in large cells. The cells exhibited excellent long-term cyclability. In a high rate charge-discharge test, more than 6000 cycles were completed without any serious reduction in capacity. A cathode electrode sheet incorporating LiFePO 4 -based material taken from the cell after a test consisting of more than 8000 cycles exhibited little deterioration compared with an electrode sheet obtained from an unused cell. The thermal stability of the LiFePO 4 in the cells was examined with a heating test at 180°C, a nail penetration test, and a crush test. Although the cell case swelled slightly in the heating test, the cells did not smoke or catch fire in any of the safety tests. The cathode electrode taken from the prismatic cell used in the 180°C heating test had a similar capacity and discharge profile to a cathode taken from an untested cell.

Photorechargeable air batteries, which discharge by reducing oxygen in the air and which can be charged by light irradiation, are new types of secondary batteries. We have investigated recharging this type of battery via the photoelectrochemical reaction that occurs at its metal hydride-semiconductor/electrolyte interface. This paper discusses the photorecharging capability of an air battery using a metal hydride anode, namely, a SrTiO 3 -LaNi 3.76 Al 1.24 H n ͉KOH͉O 2 cell. We have confirmed that our new negative electrode not only prevents self-discharge but is also capable of semiconductor band bending, which is the most important requirement for photorecharging. We have demonstrated that this battery can be photorecharged and discharged by using a metal hydride electrode and oxygen from air.

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