Secondary battery
The object of an exemplary embodiment of the invention is to provide a secondary battery which contains a positive electrode active material operating at a potential of 4.5 V or higher and which has good cycle property at a high temperature. An exemplary embodiment of the invention is a secondary battery, comprising a positive electrode that can absorb and desorb lithium and an electrolyte liquid; wherein the positive electrode comprises a positive electrode active material that operates at a potential of 4.5 V or higher with respect to lithium; and wherein the electrolyte liquid comprises a fluorinated ether represented by a prescribed formula and a cyclic-type sulfonate represented by a prescribed formula.
1. A secondary battery, comprising a positive electrode that can absorb and desorb lithium and an electrolyte liquid;
wherein the positive electrode comprises a positive electrode active material that operates at a potential of 4.5 V or higher with respect to the standard electrode potential of lithium; and
wherein the electrolyte liquid comprises a fluorinated ether represented by following formula (5) and a cyclic-type sulfonate represented by following formula (2):
X 1 —(CX 2 X 3 ) n —CH 2 O—CX 4 X 5 —CX 6 X 7 —X 8 (5)
wherein, in formula (5), n is 1 to 8 and X 1 to X 8 are each independently a fluorine atom or a hydrogen atom, in which at least one of X 1 to X 3 is a fluorine atom and at least one of X 4 to X 8 is a fluorine atom; and
wherein, in formula (2), A and B each independently denote an alkylene group or a fluorinated alkylene group, and X denotes single bond or —OSO 2 — group.
2. The secondary battery according to claim 1 , wherein the positive electrode active material is a lithium manganese complex oxide represented by following formula (3):
Li a (M x Mn 2-x-y Y y )(O 4-w Z w ) (3)
wherein, in formula (3), x, y, a and w satisfy 0.4≦x≦1.2, 0≦y, x+y<2, 0≦a≦1.2 and 0 ≦w ≦1, M comprises at least one selected from the group consisting of Co, Ni, Fe, Cr and Cu, Y is at least one selected from the group consisting of Li, B, Na, Mg, Al, Ti, Si, K and Ca, and Z is at least one selected from the group consisting of F and Cl.
3. The secondary battery according to claim 2 , wherein a content of the fluorinated ether is 5 to 60 mass % with respect to a total amount of solvent in the electrolyte liquid.
4. The secondary battery according to claim 2 , wherein the cyclic-type sulfonate is a cyclic-type monosulfonate represented by following formula (6):
wherein, in formula (6), R 101 and R 102 each independently denote a hydrogen atom, a fluorine atom or an alkyl group with a carbon number of 1 to 4, and n is 1, 2, 3 or 4.
5. The secondary battery according to claim 2 , wherein the cyclic-type sulfonate is a cyclic-type disulfonate represented by following formula (7):
wherein, in formula (7), R 201 to R 204 each independently denote a hydrogen atom, a fluorine atom or an alkyl group with a carbon number of 1 to 4, and n is 1, 2, 3 or 4.
6. The secondary battery according to claim 1 , wherein the positive electrode active material is a lithium manganese complex oxide represented by following formula (4):
LiNi x Mn 2-x-y A y O 4 (4)
wherein, in formula (4), x and y satisfy 0.4 <x <0.6 and 0 ≦y <0.3, and A is at least one selected from the group consisting of Li, B, Na, Mg, Al, Ti and Si.
7. The secondary battery according to claim 6 , wherein a content of the fluorinated ether in a solvent is 5 to 60 mass % with respect to a total amount of solvent in the electrolyte liquid.
8. The secondary battery according to claim 6 , wherein the cyclic-type sulfonate is a cyclic-type monosulfonate represented by following formula (6):
wherein, in formula (6), R 101 and R 102 each independently denote a hydrogen atom, a fluorine atom or an alkyl group with a carbon number of 1 to 4, and n is 1, 2, 3 or 4.
9. The secondary battery according to claim 6 , wherein the cyclic-type sulfonate is a cyclic-type disulfonate represented by following formula (7):
wherein, in formula (7), R 201 to R 204 each independently denote a hydrogen atom, a fluorine atom or an alkyl group with a carbon number of 1 to 4, and n is 1, 2, 3 or 4.
10. The secondary battery according to claim 1 , wherein, in formula (5), n is 1 to 4 and the atom ratio of fluorine atoms and hydrogen atoms ((total number of fluorine atoms)/(total number of hydrogen atoms)) is 1.8 to 3.0.
11. The secondary battery according to claim 1 , wherein a content of the fluorinated ether is 5 to 60 mass % with respect to a total amount of solvent in the electrolyte liquid.
12. The secondary battery according to claim 1 , wherein the cyclic-type sulfonate is a cyclic-type monosulfonate represented by following formula (6):
wherein, in formula (6), R 101 and R 102 each independently denote a hydrogen atom, a fluorine atom or an alkyl group with a carbon number of 1 to 4, and n is 1, 2, 3 or 4.
13. The secondary battery according to claim 1 , wherein the cyclic-type sulfonate is a cyclic-type disulfonate represented by following formula (7):
wherein, in formula (7), R 201 to R 204 each independently denote a hydrogen atom, a fluorine atom or an alkyl group with a carbon number of 1 to 4, and n is 1, 2, 3 or 4.
14. The secondary battery according to claim 1 , wherein a content of the cyclic-type sulfonate in the electrolyte liquid is 0.01 to 10 mass %.
15. The secondary battery according to claim 1 , wherein the electrolyte liquid further comprises a carbonate compound.