Electrochemical device having different kinds of separators

1. An electrochemical device, comprising:

a plurality of unit cells, each having a first separator and a cathode and an anode positioned at both sides of the first separator; and

a continuous single second separator interposed between adjacent unit cells in correspondence with each other in a laminated pattern and arranged to surround each unit cell,

wherein the first separator includes a heat-resisting porous substrate having a melt point of 200° C. or above and a first porous coating layer formed on at least one surface of the heat-resisting porous substrate and made of a mixture of a plurality of inorganic particles and a binder polymer, and

wherein the second separator includes a polyolefin porous substrate and a second porous coating layer formed on at least one surface of the polyolefin porous substrate and made of a mixture of a plurality of inorganic particles and a binder polymer.

2. The electrochemical device according to claim 1 ,

wherein the heat-resisting porous substrate is formed using any one material or a mixture of at least two materials selected from the group consisting of polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylenesulfidro, polyethylenenaphthalene and polyphenyleneoxide.

3. The electrochemical device according to claim 1 ,

wherein the heat-resisting porous substrate has a thickness ranging from 1 to 100 μm, a pore size ranging from 0.01 to 50 μm, and a porosity ranging from 5 to 95%.

4. The electrochemical device according to claim 1 ,

wherein the polyolefin porous substrate is formed using any material selected from the group consisting of polyethylene, polypropylene and their mixtures.

5. The electrochemical device according to claim 1 ,

wherein the polyolefin porous substrate has a melt point ranging from 130 to 160° C.

6. The electrochemical device according to claim 1 ,

wherein the polyolefin porous substrate has a thickness ranging from 1 to 100 μm, a pore size ranging from 0.1 to 50 μm and a porosity ranging from 10 to 95%.

7. The electrochemical device according to claim 1 ,

wherein the inorganic particles of the first and second porous coating layers have a diameter size ranging from 0.001 to 10 μm, independently.

8. The electrochemical device according to claim 1 ,

wherein the inorganic particles of the first and second porous coating layers are selected from the group consisting of inorganic particles having a dielectric constant of 5 or above, inorganic particles having lithium-ion transferring capability, or their mixtures.

9. The electrochemical device according to claim 8 ,

wherein the inorganic particle having a dielectric constant of 5 or above is an inorganic particle selected from the group consisting of BaTiO 3 , Pb(Zr,Ti)O 3 (PZT), Pb 1-x La x Zr 1-y Ti y O 3 (PLZT), PB(Mg 3 Nb 2/3 )O 3 —PbTiO 3 (PMN-PT), hafnia (HfO 2 ), SrTiO 3 , SnO 2 , CeO 2 , MgO, NiO, CaO, ZnO, ZrO 2 , SiO 2 , Y 2 O 3 , Al 2 O 3 , SiC and TiO 2 .

10. The electrochemical device according to claim 9 ,

wherein the inorganic particle having a dielectric constant of 5 or above is an piezoelectric inorganic particle selected from the group consisting of BaTiO 3 , Pb(Zr,Ti)O 3 (PZT), Pb 1-x La x Zr 1-y Ti y O 3 (PLZT), PB(Mg 3 Nb 2/3 )O 3 —PbTiO 3 (PMN-PT) and hafnia (HfO 2 ).

11. The electrochemical device according to claim 8 ,

wherein the inorganic particle having lithium ion conductivity is an inorganic particle selected from the group consisting of lithium phosphate (Li 3 PO 4 ), lithium titanium phosphate (Li x Ti y (PO 4 ) 3 , 0<x<2, 0<y<3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO 4 ) 3 , 0<x<2, 0<y<1, 0<z<3), (LiAlTiP) x O y type glass (0<x<4, 0<y<13), lithium lanthanum titanate (Li x La y TiO 3 , 0<x<2, 0<y<3), lithium germanium thiophosphate (Li x Ge y P z S w , 0<x<4, 0<y<1, 0<z<1, 0<w<5), lithium nitrides (Li x N y , 0<x<4, 0<y<2), SiS 2 type glass (Li x Si y S z , 0<x<3, 0<y<2, 0<z<4), and P 2 S 5 type glass (Li x P y S z , 0<x<3, 0<y<3, 0<z<7).

12. The electrochemical device according to claim 1 ,

wherein a weight ratio of the inorganic particles to the binder polymer in the first and second porous coating layers ranges from 50:50 to 99:1, independently.

13. The electrochemical device according to claim 1 ,

wherein the binder polymer of the first and second porous coating layers has a solubility parameter ranging from 15 to 45 Mpa 1/2 , independently.

14. The electrochemical device according to claim 13 ,

wherein the binder polymer is any one material or a mixture of at least two materials selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan and carboxyl methyl cellulose.

15. The electrochemical device according to claim 1 ,

wherein the first and second porous coating layers have a thickness ranging from 0.01 to 20 μm, independently.

16. The electrochemical device according to claim 1 ,

wherein the electrochemical device is a lithium secondary battery.