Method for manufacturing separators, separators manufactured by the method and electrochemical devices including the separators
View Patent ↗A method for manufacturing separators includes (S 1 ) treating at least one of the laminating surfaces of two porous substrates by corona discharge and laminating the porous substrates, (S 2 ) preparing a slurry containing inorganic particles dispersed therein and a solution of a binder polymer in a solvent, and coating the slurry on both surfaces of the laminate of the porous substrates, and (S 3 ) delaminating the coated laminate of the porous substrates. According to the method, two separators can be simultaneously manufactured with enhanced productivity. In addition, corona discharge can reduce damage to the surfaces of the porous substrates during lamination while maintaining the porosities of the porous substrates. Therefore, excellent performance of electrochemical devices using the separators can be ensured.
1. A method for manufacturing separators comprising:
(S1) treating at least one of the laminating surfaces of two porous substrates by corona discharge and laminating the porous substrates,
(S2) preparing a slurry containing inorganic particles dispersed therein and a solution of a binder polymer in a solvent, and coating the slurry on both surfaces of the laminate of the porous substrates, and
(S3) delaminating the coated laminate of the porous substrates.
2. The method according to claim 1 , wherein each of the porous substrates is made of a polyolefin.
3. The method according to claim 2 , wherein the polyolefin is selected from the group consisting of polyethylene, polypropylene, polybutylene and polypentene.
4. The method according to claim 1 , wherein each of the porous substrates has a thickness of 5 to 50 μm, a pore size of 0.01 to 50 μm and a porosity of 10 to 95%.
5. The method according to claim 1 , wherein the slurry is coated on the porous substrates by dip coating.
6. The method according to claim 1 , wherein the inorganic particles have an average particle diameter of 0.001 to 10 μm.
7. The method according to claim 1 , wherein the inorganic particles are selected from the group consisting of inorganic particles having a dielectric constant of 5 or above, inorganic particles having the ability to transport lithium ions, and mixtures thereof.
8. The method according to claim 7 , wherein the inorganic particles having a dielectric constant of 5 or above are selected from the group consisting of BaTiO 3 , Pb(Zr x ,Ti 1-x )O 3 (PZT, 0<x<1), Pb 1 ,La x Zr 1-y Ti y O 3 (PLZT, 0<x<1, 0<y<1), (1-x)Pb(Mg 1/3 Nb 2/3 ) O 3 -xPbTiO 3 (PMN-PT, 0<x<1), hafnia (HfO 2 ), SrTiO 3 , SnO 2 , CeO 2 , MgO, NiO, CaO, ZnO, ZrO 2 , SiO 2 , Y 2 O 3 ,Al 2 O 2 , SiC, TiO 2 particles, and mixtures thereof.
9. The method according to claim 7 , wherein the inorganic particles having the ability to transport lithium ions are 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 nitride (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), P 2 S 5 type glass (Li x P y S z , 0<x<3, 0<y<3, 0<z<7) particles, and mixtures thereof.
10. The method according to claim 1 , wherein the inorganic particles and the binder polymer are used in a weight ratio of 50:50 to 99:1.
11. The method according to claim 1 , wherein the binder polymer is selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethyl methacrylate, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, and mixtures thereof.
12. A separator comprising a porous substrate wherein the porous substrate has an uncoated first surface and a second surface covered with an organic/inorganic composite layer containing inorganic particles and a binder polymer, and the areas of characteristic peaks of the binder polymer and the porous substrate at the first and second surfaces, as measured using an attenuated total reflection Fourier transform infrared (ATR-FTIR) spectrometer, satisfy the mathematical FIG. 1 :
0
≤
[
(
Area
of
characteristic
peaks
of
the
first
binder
polymer
at
the
first
surface
Area
of
characteristic
peaks
of
the
porous
substrate
at
the
first
surface
)
(
Area
of
characteristic
peaks
of
the
first
binder
polymer
at
the
second
surface
Area
of
characteristic
peaks
of
the
porous
substrate
at
the
second
surface
)
]
<
0.5
.
Mathematical
Figure
1
13. An electrochemical device comprising a cathode, an anode and the separator according to claim 12 interposed between the cathode and the anode.
14. The electrochemical device according to claim 13 , wherein the electrochemical device is a lithium secondary battery.