Composition for gel polymer electrolyte and lithium secondary battery including the same
View Patent ↗The present invention relates to a composition for a gel polymer electrolyte and a lithium secondary battery including the same, and more specifically, an objective of the present invention is to provide a secondary battery in which, since an isocyanate-containing monomer is introduced to a composition for a gel polymer electrolyte to induce a urethane reaction with LiOH on a surface of a lithium transition metal oxide to form a coating layer including a urethane bond-containing oligomer on the surface of the lithium transition metal oxide, and thereby side reactions caused by HF in the battery are minimized, capacity characteristics are improved, and adhesion between a positive electrode and a separator is enhanced to minimize the swelling phenomenon of the battery.
1. An electrolyte composition for a gel polymer electrolyte, comprising:
a solvent;
a lithium salt; and
a first monomer represented by the following Formula 1:
R—CH (3-n) N═C═O) n [Formula 1]
in Formula 1,
R is a C 1-5 alkyl group including an acrylate group or a methacrylate group or a C 1-20 aryl group including an acrylate group or a methacrylate group, and
n is an integer of 2 to 3, and
a second monomer, wherein the second monomer includes one or more functional groups selected from the group consisting of an acrylate group, a vinyl group, an epoxy group, an amino group, an amide group, an imide group, a hydroxyl group, a methylol group and a carboxyl group,
wherein a content of the first monomer is in a range of 0.2 to 5 wt % based on the electrolyte composition, and
wherein a content of the first monomer and the second monomer is in a range of 0.5 to 20 wt % based on the electrolyte composition.
2. The electrolyte composition according to claim 1 , wherein the first monomer is one or more selected from the group consisting of diisocyanate ethyl acrylate and diisocyanate ethyl methacrylate.
3. The electrolyte composition according to claim 1 , wherein the second monomer includes two to five acrylate groups.
4. The electrolyte composition according to claim 3 , wherein the second monomer is dipentaerythritol pentaacrylate or dipentaerythritol triacrylate.
5. The electrolyte composition according to claim 1 , further comprising a polymerization initiator.
6. The electrolyte composition according to claim 5 , wherein the polymerization initiator is one or more selected from the group consisting of benzoyl peroxide, acetyl peroxide, dilauryl peroxide, di-tert-butylperoxide, t-butyl peroxy-2-ethyl-hexanoate, cumyl hydroperoxide, hydrogen peroxide, 2,2-azobis(2-cyanobutane), 2,2-azobis(methylbutyronitrile), azobis(isobutyronitrile) (AIBN) and azobisdimethyl-valeronitrile (AMVN).
7. The electrolyte composition according to claim 5 , wherein a content of the polymerization initiator is in a range of 0.1 to 3 wt % based on a total content of the total monomers.
8. The electrolyte composition according to claim 1 , wherein the solvent is one or more selected from the group consisting of a cyclic carbonate, a linear carbonate, a lactone, an ether, an ester, a sulfoxide, an acetonitrile, a lactam, a ketone and a halogen derivative thereof.
9. The electrolyte composition according to claim 1 , wherein the lithium salt is one or more selected from the group consisting of LiPF 6 , LiAsF 6 , LiCF 3 SO 3 , LiN(CF 3 SO 2 ) 2 , LiBF 4 , LiSbF 6 , LiN(C 2 F 5 SO 2 ) 2 , LiAlO 4 , LiAlCl 4 , LiCo 0.2 Ni 0.56 Mn 0.27 O 2 , LiCoO 2 , LiSO 3 CF 3 and LiClO 4 .
10. A lithium secondary battery comprising a positive electrode, a negative electrode, a separator and the electrolyte composition for the gel polymer electrolyte of claim 1 .