The purpose of the present invention is to provide: an enhanced electrolyte for power storage devices in which electrical resistance is reduced and it is possible to maintain high capacity even afterrepeated charging and discharging; and a power storage device. Provided is an electrolyte for power storage devices that is characterized by containing a lithium-containing complex compound represented by formula (1), formula (2), formula (3), formula (4), or formula (5) indicated below. Formula (1): (Li)m(A)n(UFx)y. Formula (2): (Li)m(Si)n(O)q(UFx)y (in formulas (1) and (2), A is O, S, P, or N, Uis a boron atom or a phosphorus atom, m and n each independently represent a number between 1 and 6 inclusive, q is a number between 1 and 12 inclusive, x is 3 or 5, and y is a number between 1 and 6inclusive). Formula (3): (Li)m(O)n(B)p(OWFq)x (in the formula, W is a boron atom or a phosphorus atom, m, p, and x each independently represent a number between 1 and 15 inclusive, n is a number between 0 and 15 inclusive, and q is 3 or 5). Formula (4): (Li)m(B)p(O)n(OR)y(OWFq)x (in the formula, W is a boron atom or a phosphorus atom, n is a number between 0 and 15 inclusive, p, m, x, and y eachindependently represent a number between 1 and 12 inclusive, q is 3 or 5, R is hydrogen, an alkyl group, an alkenyl group, an aryl group, a carbonyl group, a sulfonyl group, or a silyl group, and these groups may have a fluorine atom, an oxygen atom, and other substituent groups). Formula (5): (Li)m(O)n(B)p(OOC-(A)z-COO)y(OWFq)x (in the formula, W is a boron atom or a phosphorus atom, A is a grouphaving six carbon atoms and may be an alkylene group, an alkenylene group, an alkynylene group, a phenylene group, or an alkylene group having an oxygen atom or a sulfur atom in the main chain thereof, m, p, x, and y each independently represent a number between 1 and 20 inclusive, n is a number between 0 and 20 inclusive, n is a number between 0 and 15 inclusive, z is 0 or 1, and q is 3 or 5).