Electrolytic solution
Provided is an electrolytic solution exhibiting excellent withstand voltage and satisfactory characteristics even at low and high temperatures. The invention is an electrolytic solution that includes a cyclic carbonate (I-1) represented by formula (I-1): (in the formula, R is an alkyl group having two or more carbon atoms, a fluorine-containing alkyl group having two or more carbon atoms, an alkoxy group or a fluorine-containing alkoxy group, in which an oxygen atom may be inserted between carbon atoms); a cyclic carbonate (I-2) different from the cyclic carbonate (I-1); and an electrolyte salt (II)).
1. An electrolytic solution, comprising:
a cyclic carbonate (I-1) represented by formula (I-1):
(in the formula, R is a fluorine-containing ether group (Ia) having two or more carbon atoms, a fluorine-containing alkoxy group (Ib), or a fluorine-containing alkyl group (Ic) having two or more carbon atoms);
a cyclic carbonate (I-2) different from the cyclic carbonate (I-1)); and
an electrolyte salt (II),
wherein volume percent of the cyclic carbonate (I-1) ranges from 0.2 to 8.0,
wherein the fluorine-containing alkyl group (Ic) is —CH 2 CF(CF 3 ) 2 ,—CH 2 CF 2 H, —CH 2 CF 2 CF 3 , —CH 2 CF 2 CF 2 H, —CH 2 CF 2 CFH 2 , —CH 2 CF 2 CH 3 or —CH 2 CH(CF 3 )CF 3 ,
wherein the fluorine-containing ether group (Ia) is represented by formula (Ia-1):
(in the formula, R 1 is an alkyl group optionally having a fluorine atom; R 2 is an alkylene group optionally having a fluorine atom; n1 is an integer from 1 to 3; and at least one of R 1 and R 2 has a fluorine atom), and
wherein the fluorine-containing alkoxy group (Ib) is represented by formula (2):
X 2 3 C—(R 5 ) n4 —O— (2)
(the three X 2 are identical or dissimilar and each is H or F; R 5 is C1 to C5 alkylene group optionally having a fluorine atom: and n4 is 0 or 1, such that any one of the three X 2 comprises a fluorine atom).
2. The electrolytic solution according to claim 1 , comprising a linear carbonate (I-3).
3. The electrolytic solution according to claim 2 , wherein a volume ratio of cyclic carbonate (I-1) to cyclic carbonate (I-2) to linear carbonate (I-3) is 0.5-8.0: 10.0-92.0: 0-89.5.
4. The electrolytic solution according to claim 1 , wherein the fluorine content of R in formula (I-1) ranges from 10 to 76 mass %.
5. The electrolytic solution according to claim 1 , wherein the cyclic carbonate (I-2) is at least one cyclic carbonate selected from the group consisting of ethylene carbonate, propylene carbonate, fluoroethylene carbonate and vinylene carbonate.