Separator comprising an organic-inorganic adhesion promoter
The invention relates to a process for producing a separator comprising the steps of: providing a sheetlike porous substrate, a solvent, ceramic particles and an adhesion promoter; preparing a slip by mixing the solvent, the adhesion promoter and the ceramic particles; coating the substrate with the slip and thermally drying the coated substrate to obtain the separator. The problem addressed is that of specifying a process useful for producing separators having a higher ceramic content. The problem is solved when the solvent used is a mixture of water and at least one organic component; the adhesion promoter used is a mixture of silanes and at least one thermally crosslinkable acrylic polymer; the slip is admixed with a carboxylic acid preparation and also with a defoamer component free from silicone oil.
1. A method for producing a separator, said method comprising:
a) preparing a slip, comprising:
a solvent comprising water and at least one organic compound;
a thermally crosslinkable acrylic polymer;
at least one silane selected from the group consisting of 3-aminopropyltriethoxysilane, 2-aminoethyl-3-aminopropyltrimethoxysilane, 3-glycidyloxy-trimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris(2-methoxyethoxy)silane, methyltriethoxysilane, and 3-glycidyloxypropyltriethoxysilane;
particles of a ceramic;
a carboxylic acid mixture having a melting point below 80° C. comprising carboxylic acids selected from the group consisting of a fatty carboxylic acid, an oily carboxylic acid and a polymeric carboxylic acid; and
a silicone oil free defoamer;
b) coating a sheetlike porous substrate with the slip; and
c) thermally drying the coated substrate to obtain the separator.
2. The method according to claim 1 ,
wherein
thermally drying the coated substrate to obtain the separator in c) cures the silanes, crosslinks the acrylic polymer, and is carried out at a temperature below the glass transition temperature T G of the acrylic polymer.
3. The method according to claim 1 ,
wherein
the acrylic polymer swells little or not at all in the solvent and is infusible after crosslinking in c).
4. The method according to claim 1 ,
wherein the slip further comprises a silicate.
5. The method according to claim 1 ,
wherein the silicone oil free defoamer component comprises an organic supporting medium and an organic solid.
6. The method according to claim 1 , wherein the organic component of the solvent is an alcohol.
7. The method according to claim 1 , wherein the porous substrate is a fibrous nonwoven web.
8. The method according to claim 1 , wherein
the porous substrate is a fibrous nonwoven web comprising organic fibres selected from the group consisting of polyacrylonitrile, polyester, polyimide, polyamide, polytetrafluoroethylene, polyethylene terephthalate and polyolefin.
9. The method according to claim 1 ,
wherein
the ceramic particles have a non-spherical structure, and
the ceramic is selected from the group consisting of oxides of the metals Al, Zr, Si, Ti and Y.
10. The method according to claim 1 ,
wherein the thermally crosslinkable acrylic polymer is in the form of a dispersion.
11. The method according to claim 10 ,
wherein preparing the slip comprises:
a) introducing the carboxylic acid mixture into the solvent;
b) dispersing the ceramic particles in the carboxylic acid mixture solvent composition from a) to obtain a dispersion;
c) introducing the silanes and the acrylic polymer into the solvent to obtain a sol;
d) mixing the dispersion and the sol;
e) admixing the silicone oil free defoamer component to the mixed dispersion and sol to obtain the slip.
12. The method according to claim 1 , wherein
a proportion of the silicone oil free defoamer component in the slip is less than 200 ppm.
13. The method according to claim 1 , wherein
a proportion of ceramic particles is in the range from 45 to 60 wt % in the slip and more than 90 wt % in the slip dried state.
14. The method according to claim 1 ,
wherein
a content of the silane is from 25 to 45 wt % based on the weight of the thermally crosslinkable acrylic polymer and the at least one silane.
15. A separator obtained by the process according to claim 1 .
16. The separator according to claim 15 , wherein a content of the ceramic in the dried cured coating is 80 wt % or less.
17. The separator according to claim 15 wherein a thickness of the separator is from 18 to 25 μm and/or a porosity of the separator is from 30% to 70%.
18. An electric energy store or of an electrochemical cell comprising the separator of claim 15 positioned to insulate an electrode in said energy store or cell.
19. A composition configured for use in producing a separator comprising: a solvent comprising water and an alcohol;
a thermally crosslinkable acrylic polymer;
at least one silane selected from the group consisting of 3-aminopropyltriethoxysilane, 2-aminoethyl-3-aminopropyltrimethoxysilane, 3-glycidyloxy-trimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris(2-methoxyethoxy)silane, methyltriethoxysilane, and 3-glycidyloxypropyltriethoxysilane;
particles of a ceramic;
a carboxylic acid mixture having a melting point below 80° C. comprising carboxylic acids selected from the group consisting of a fatty carboxylic acid, an oily carboxylic acid and a polymeric carboxylic acid; and a silicone oil free defoamer.