One object is to provide a power storage device including an electrolyte using a room-temperature ionic liquid which includes a univalent anion and a cyclic quaternary ammonium cation having excellent reduction resistance. Another object is to provide a high-performance power storage device. A room-temperature ionic liquid which includes a cyclic quaternary ammonium cation represented by a general formula (G1) below is used for an electrolyte of a power storage device. In the general formula (G1), one or two of R
1
to R
5
are any of an alkyl group having 1 to 20 carbon atoms, a methoxy group, a methoxymethyl group, and a methoxyethyl group. The other three or four of R
1
to R
5
are hydrogen atoms. A
−
is a univalent imide anion, a univalent methide anion, a perfluoroalkyl sulfonic acid anion, tetrafluoroborate (BF
4
−
), or hexafluorophosphate (PF
6
−
).
一个目标是提供一种使用室温
离子液体的电解质的电力储存装置,该
离子液体包括具有优异还原抗性的单价阴离子和环状季
铵阳离子。另一个目标是提供一种高性能的电力储存装置。使用包括以下一般式(G1)所表示的环状季
铵阳离子的室温
离子液体作为电力储存装置的电解质。在一般式(G1)中,R1到R5中的一到两个是具有1至20个碳原子的烷基,甲氧基基团,甲氧甲基基团和甲氧乙基基团中的任意一种。其余的三到四个R1到R5是氢原子。A-是单价的
亚胺阴离子,单价的甲基阴离子,
全氟烷基
磺酸根离子,四
氟硼酸根离子(
BF4-)或
六氟磷酸根离子(PF6-)。