Overcharge inhibitor, and nonaqueous electrolyte solution and secondary battery using the same
View Patent ↗An overcharge inhibitor is provided which increases an internal resistance of a battery, being electropolymerized by reaction with a positive electrode at a high potential in overcharging. The overcharge inhibitor is produced by using a polymer containing a polymerizable monomer as a repeating unit. The polymerizable monomer has a functional group that is electropolymerized at a potential of 4.3 to 5.5 V based on a lithium metal reference.
1. A nonaqueous electrolyte solution comprising:
a nonaqueous solvent;
an electrolyte salt; and
an overcharge inhibitor comprising a polymerizable monomer as a repeating unit, being represented by the following chemical formula (1):
X a Y b (1)
where X is one polymerizable monomer, and has a functional group that is electropolymerized at a potential of 4.3 to 5.5 V based on a lithium metal reference, the functional group having an aromatic group; Y is the other polymerizable monomer, has an ether bond or an ester bond, and may be the X; subscript “a” is an integer number of 1 or more; subscript “b” is 0 or an integer number of 1 or more; and a number average molecular weight of the overcharge inhibitor is in a range of 3000 to 1000000.
2. The nonaqueous electrolyte solution according to claim 1 , wherein each of the X and Y has a double bond between carbon atoms.
3. The nonaqueous electrolyte solution according to claim 2 , wherein each of the X and Y contains a vinyl group or a propenoate group.
4. The nonaqueous electrolyte solution according to claim 1 , wherein each of the X and Y is represented by the following chemical formula (2) or (3):
where each of R 1 and R 4 is a functional group having an aromatic ring represented by any one of the following chemical formulas (4) to (6); each of R 2 and R 5 is an alkyl group having the carbon number of 1 to 3 in which a hydrogen atom of the alkyl group may be substituted by a fluorine atom; R 3 is a group having an alkyl group having the carbon number of 1 to 6 or an aromatic group in which a hydrogen atom of the alkyl group or aromatic group may be substituted by a fluorine atom, alternatively, R 3 may be an alkyl group having the carbon number of 1 to 6 or aromatic group via an alkoxy group represented by the following chemical formula (7); R 6 is a functional group having an alkyl group having the carbon number of 1 to 6 or an aromatic ring in which a hydrogen atom of the functional group having the alkyl group or the aromatic group may be substituted by a fluorine atom; each of subscripts “c” and “e” is an integer number of 1 or more; and each of subscripts “d” and “f” is 0 or an integer number of 1 or more;
where R 7 is an alkyl group having the carbon number of 2 to 6 or a phenylene group in which a hydrogen atom of the alkyl group or phenylene group may be substituted by a fluorine atom; and subscript “g” is an integer number of 1 to 10.
5. The nonaqueous electrolyte solution according to claim 1 , wherein at least one of the X and Y is selected from the group consisting of the following chemical formulas (8) to (10):
where each of subscripts “x1 to x3” is an integer number of 1 to 10; each of subscripts “m1 to m3” is an integer number of 1 or more; each of subscripts “n1 to n3” is 0 or an integer number of 1 or more; and each of R 8 to R 10 is a functional group having an alkyl group having the carbon number of 1 to 6 or an aromatic ring in which a hydrogen atom of the functional group having the alkyl group or aromatic group may be substituted by a fluorine atom.
6. The nonaqueous electrolyte solution according to claim 1 , wherein at least one of the X and Y is selected from the group consisting of the following chemical formulas (11) to (13):
where each of subscripts “p1 to p3” is an integer number of 1 or more; each of subscripts “q1 to q3” is 0 or an integer number of 1 or more; and each of R 11 to R 13 is a functional group having an alkyl group having the carbon number of 1 to 6 or an aromatic ring in which a hydrogen atom of the functional group having the alkyl group or aromatic group may be substituted by a fluorine atom.
7. The nonaqueous electrolyte solution according to claim 1 , wherein the electrolyte salt contains a lithium salt.
8. The nonaqueous electrolyte solution according to claim 1 , wherein the nonaqueous solvent includes a cyclic carbonate or a chain carbonate.
9. A secondary battery comprising:
a positive electrode;
a negative electrode;
a separator; and
the nonaqueous electrolyte solution according to claim 1 .
10. The secondary battery according to claim 9 , wherein the positive electrode and the negative electrode can store and discharge a lithium element.
11. The nonaqueous electrolyte solution according to claim 1 ,
wherein the functional group has an aromatic ring represented by any one of the following chemical formulas (4) to (6):
12. The nonaqueous electrolyte solution according to claim 1 ,
wherein a molar ratio of X to Y is 0.1 to 10.
13. The nonaqueous electrolyte solution according to claim 5 ,
containing X of 20 to 30% by weight.