Single ion conductor-containing composite polymer electrolyte for lithium secondary battery and method of manufacturing the same

1. A composite polymer electrolyte for a lithium secondary battery, which comprises:

a first polymer matrix made of a first porous polymer with a first pore size, wherein the first porous polymer is polyethylene, polypropylene, polyimide, polysulfone, polyurethane, polyvinyichioride, cellulose, nylon, polyacrylonitrile, polyvinylidene fluoride, polytetrafluoroethylene, a copolymer or blend thereof, and wherein the first polymer matrix does not comprise a polymer type single ion conductor;

a second polymer matrix coated on the first polymer matrix and made of a single ion conductor consisting essentially of polymer, an inorganic material, and a second porous polymer with a second pore size smaller than the first pore size, wherein the second porous polymer is a vinylidene fluoride based polymer, an acrylate based polymer, a copolymer or a blend thereof, and wherein the second polymer matrix has an ionic conductivity equal to or higher than the ionic conductivity of the first polymer matrix; and

an electrolyte solution impregnated into the first polymer matrix and the second polymer matrix.

2. The composite polymer electrolyte of claim 1 , wherein the single ion conductor is perfluorinated ionomer, methylmethacrylate/alkaline metal methacrylate copolymer ionomer, methylmethacrylate/alkaline itaconate copolymer ionomer, methylmethacrylate/alkaline maleate copolymer ionomer, polystyrene ionomer, or a blend thereof.

3. The composite polymer electrolyte of claim 1 , wherein the second porous polymer is a copolymer of vinylidene fluoride and hexafluoropropylene, a copolymer of vinylidene fluoride and trifluoroethylene, a copolymer of vinylidene fluoride and tetrafluoroethylene, polymethylacrylate, polyethylacrylate, polymethylmethacrylate, polyethylmethacrylate, polybutylacrylate, polybutylmethacrylate, polyvinylacetate, polyethylene oxide, polypropylene oxide, a copolymer or blend thereof.

4. The composite polymer electrolyte of claim 1 , wherein the inorganic material is selected from the group consisting of silica, talc, alumina (Al 2 O 3 ), γLiAlO 2 , TiO 2 , zeolite, molybdenum phosphate hydrate, and tungsten phosphate hydrate.

5. The composite polymer electrolyte of claim 1 , wherein the inorganic material is added in an amount of 1 to 100% by weight, based on the total weight of the polymer of the second porous matrix.

6. The composite polymer electrolyte of claim 1 , wherein the first polymer matrix has a thickness of 10 to 25 μm and the second polymer matrix has a thickness of 0.5 to 10 μm.

7. The composite polymer electrolyte of claim 1 , wherein the electrolyte solution is made of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, tetrahydrofuran, 2-methyltetrahydrofuran, dimethoxyethane, methyl formate, ethyl formate, gamma-butyrolactone, or a mixture thereof.

8. The composite polymer electrolyte of claim 1 , wherein the electrolyte solution is impregnated into the first polymer matrix and the second polymer matrix in an amount of 1 to 1,000% by weight, based on the total weight of the polymer of the first polymer matrix and the second polymer matrix.

9. The composite polymer electrolyte of claim 1 , wherein the electrolyte solution comprises at least one lithium salt selected from the group consisting of lithium perchlorate (LiClO 4 ), lithium triflate (LiCF 3 SO 3 ), lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), and lithium trifluoromethanesulfonylimide (LiN(CF 3 SO 2 ) 2 ).

10. The composite polymer electrolyte of claim 9 , wherein the lithium salt is dissolved in the electrolyte solution in an amount of 1 to 200% by weight, based on the total weight of the polymer of the first polymer matrix and the second polymer matrix.

11. A method of manufacturing a composite polymer electrolyte for a lithium secondary battery, the method comprising:

preparing a first polymer matrix made of a first porous polymer with a first pore size, wherein the first porous polymer is polyethylene, polypropylene, polyimide, polysulfone, polyurethane, polyvinylchloride, cellulose, nylon, polyacrylonitrile, polyvinylidene fluoride, polytetrafluoroethylene, a copolymer, or a blend thereof, and wherein the first polymer matrix does not comprise a polymer single ion conductor;

uniformly dissolving a single ion conductor consisting essentially of polymer, an inorganic material, and a second porous polymer with a second pore size smaller than the first pore size in a co-solvent in a predetermined ratio to produce a solution, wherein the second porous polymer is a vinylidene fluoride based polymer, an acrylate based polymer, a copolymer, or a blend thereof;

coating the first polymer matrix with the solution to form a second polymer matrix on the first polymer matrix, wherein the second polymer matrix has an ionic conductivity equal to or higher than the ionic conductivity of the first polymer matrix; and

impregnating the first polymer matrix and the second polymer matrix with an electrolyte solution.

12. The method of claim 11 , wherein the co-solvent is selected from the group consisting of ethanol, methanol, isopropyl alcohol, acetone, dimethylformamide, dimethylsulfoxide, N-methylpyrrolidone, and a mixture thereof.