MOLTEN SALT BATTERY, CHARGE/DISCHARGE METHOD, AND CHARGE/DISCHARGE SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide a molten salt battery (sodium ion secondary battery) which enables the achievement of both of a superior cycle life and a high capacity in a wide temperature region.SOLUTION: A molten salt battery comprises: a positive electrode including a positive electrode active material capable of reversibly occluding and releasing sodium; a negative electrode including a negative electrode active material capable of reversibly occluding and releasing sodium; a separator interposed between the positive and negative electrodes; and a molten salt electrolyte. The molten salt electrolyte includes 90 mass% or more of an ionic liquid. The ionic liquid includes a first salt and a second salt. The first salt has a sodium ion and a first anion. The second salt has an organic cation and a second anion. The positive electrode active material includes a complex oxide having a lamellar O3 type crystalline structure and including Na, Fe and Co. Of the total quantity of Fe and Co included in the complex oxide, Co accounts for 40-60 atom%.