Abstract: A reference electrode insert (14) for an electrochemical test cell (10), in particular for testing lithium ion cells, comprising a reference electrode (46) and a sleeve (15) for holding the reference electrode (46), characterized in that the sleeve (15) and the annular reference electrode (46) form a structural unit, the reference electrode (46) being secured firmly and captively in the sleeve in an encapsulated manner.

Abstract: A power storage device using an organic solvent as a nonaqueous solvent for a nonaqueous electrolyte, in which a CV charging period in CCCV charging can be prevented from being extended and which has high performance, can be provided. The power storage device includes a positive electrode, a negative electrode, and a nonaqueous electrolyte. The nonaqueous electrolyte includes an ionic liquid including an alicyclic quaternary ammonium cation having one or more substituents and a counter anion to the alicyclic quaternary ammonium cation, a cyclic ester, and an alkali metal salt. In particular, in the power storage device, the ionic liquid content is greater than or equal to 70 wt % and less than 100 wt % per unit weight of the ionic liquid and the cyclic ester in the nonaqueous electrolyte, or greater than or equal to 50 wt % and less than 80 wt % per unit weight of the nonaqueous electrolyte.