Microporous layers, an article comprising a microporous layer, and a method of manufacture thereof

1. A microporous layer comprising a microporous xerogel comprising pores that are substantially continuously interconnected from a first outermost surface of the microporous xerogel through to a second outermost surface of the microporous xerogel; and

a crosslinked polymer binder comprising a polymer and a crosslinking agent, the crosslinked polymer binder having a glass transition temperature of about 50° C. or higher, wherein the polymer binder is water soluble prior to crosslinking;

wherein the crosslinking agent comprises an aldehyde or thermosetting polymer and wherein the crosslinking agent in the polymer is present in an amount of about 40 to about 80 mole percent;

wherein the crosslinked polymer binder is present in an amount of 5 to 70 wt. % by weight of the sol in the xerogel-forming composition and wherein the xerogel-forming composition comprises about 10 to 30 percent solids;

wherein the microporous xerogel comprises a pseudo-boehmite, zirconium oxide, titanium oxide, barium oxide, silicon oxide, aluminum oxide, tin oxide, or a combination comprising at least one of the foregoing oxides;

wherein the polymer is a polyvinyl alcohol, a copolymer of a polyvinyl acetate and a polyvinyl pyrrolidone, a copolymer of polyvinyl alcohol and a polyvinyl pyrrolidone, or a combinations comprising at least one of the foregoing polymers;

wherein the glass transition temperature of the polymer changes by less than about 25% after exposure to water; and

wherein the microporous xerogel has a porosity of 40 to 80%.

2. The microporous layer of claim 1 , wherein the glass transition temperature of the polymer changes by less than about 25% after exposure to an organic electrolyte.

3. The microporous layer of claim 1 , wherein the polymer that, after crosslinking, has a glass transition temperature of about 50° C. or higher is a polyvinyl alcohol crosslinked with melamine formaldehyde or urea formaldehyde.

4. The microporous layer of claim 1 , further comprising an additive selected from the group consisting of pigments, catalysts for non-radiation curing, sensitizers for radiation curing, plasticizers, surfactants, dispersants, and combinations of at least one of the foregoing additives.

5. The microporous layer of claim 1 further comprising a non-microporous coating layer, wherein the non-microporous coating layer comprises a surface that is in contact with a surface of the microporous layer.

6. An article comprising the microporous layer of claim 1 .

7. The microporous layer of claim 1 , wherein the microporous xerogel has an average pore size of 1 to 300 nanometers.

8. The microporous layer of claim 1 , wherein the microporous xerogel has a porosity of 50% to 80%.

9. The microporous layer of claim 1 , wherein said transition glass temperature is 75 to 150° C.

10. The microporous layer of claim 1 , wherein the xerogel-forming composition comprises 14 to 20 percent solids.

11. A microporous layer comprising a microporous xerogel comprising pores that are substantially continuously interconnected from a first outermost surface of the microporous xerogel through to a second outermost surface of the microporous xerogel; and

a crosslinked polymer binder comprising a polymer and a crosslinking agent, the crosslinked polymer binder having a glass transition temperature of about 50° C. or higher, wherein the polymer binder is water soluble prior to crosslinking;

wherein the crosslinking agent comprises melamine formaldehyde or urea formaldehyde and wherein the crosslinking agent in the polymer is present in an amount of about 40 to about 60 mole percent;

wherein the crosslinked polymer binder is present in an amount of 5 to 70 wt. % by weight of the sol in the xerogel-forming composition and wherein the xerogel-forming composition comprises about 10 to 30 percent solids;

wherein the microporous xerogel comprises 5 to 10 wt. % of a pseudo-boehmite;

wherein the polymer is a polyvinyl alcohol, a copolymer of a polyvinyl acetate and a polyvinyl pyrrolidone, a copolymer of polyvinyl alcohol and a polyvinyl pyrrolidone, or a combination comprising at least one of the foregoing polymers;

wherein the glass transition temperature of the polymer changes by less than about 10% after exposure to water; and

wherein the microporous xerogel has a porosity of 40 to 80%.

12. An article made by a method of manufacture comprising:

disposing onto a substrate a xerogel-forming composition comprising a sol, a crosslinked polymer binder and a liquid medium; the crosslinked polymer binder having a glass transition temperature that is greater than or equal to about 50° C., the crosslinked polymer binder comprising a polymer and a crosslinking agent, wherein the polymer binder is water soluble prior to crosslinking;

removing the liquid medium from the xerogel-forming composition to form a microporous xerogel comprising pores that are substantially continuously interconnected from a first outermost surface of the microporous xerogel through to a second outermost surface of the microporous xerogel;

contacting a surface of the microporous xerogel with an organic electrolyte; and infusing the organic electrolyte into pores of the microporous layer;

wherein the crosslinking agent comprises an aldehyde or thermosetting polymer and wherein the crosslinking agent in the polymer is present in an amount of about 40 to about 80 mole percent;

wherein the crosslinked polymer binder is present in an amount of 5 to 70 wt. % by weight of the sol in the xerogel-forming composition;

wherein the microporous xerogel comprises a pseudo-boehmite, zirconium oxide, titanium oxide, barium oxide, silicon oxide, aluminum oxide, tin oxide, or a combination comprising at least one of the foregoing oxides;

wherein the polymer is a polyvinyl alcohol, a copolymer of a polyvinyl acetate and a polyvinyl pyrrolidone, a copolymer of polyvinyl alcohol and a polyvinyl pyrrolidone, or a combination comprising at least one of the foregoing polymers;

wherein the glass transition temperature of the polymer changes by less than about 25% after exposure to water and after exposure to an organic electrolyte; and

wherein the microporous xerogel has a porosity of 40 to 80%.

13. The microporous layer of claim 12 , wherein the organic electrolyte comprises an ionic electrolyte salt, to improve the ionic conductivity and other electrochemical properties of an electrolyte element, selected from the group consisting of a lithium polysulfide, a lithium salt of an organic ionic polysulfide, MClO 4 , MAsF 6 , MSO 3 CF 3 , MSO 3 CH 3 , MBF 4 , MB(Ph) 4 , MPF 6 , MSCN, MIMBr,

and combinations comprising at least one of the foregoing ionic electrolyte salts, where M is Li or Na.

14. A separator layer for an electrochemical cell made by a method of manufacture comprising:

disposing onto a substrate a xerogel-forming composition comprising a sol, a crosslinked polymer binder and a liquid medium; the crosslinked polymer binder having a glass transition temperature that is greater than or equal to about 50° C., the crosslinked polymer binder comprising a polymer and a crosslinking agent, wherein the polymer binder is water soluble prior to crosslinking;

removing the liquid medium from the xerogel-forming composition to form a microporous xerogel comprising pores that are substantially continuously interconnected from a first outermost surface of the microporous xerogel through to a second outermost surface of the microporous xerogel;

contacting a surface of the microporous xerogel with an organic electrolyte; and infusing the organic electrolyte into pores of the microporous layer;

wherein the crosslinking agent comprises an aldehyde or thermosetting polymer and wherein the crosslinking agent in the polymer is present in an amount of about 40 to about 80 mole percent;

wherein the crosslinked polymer binder is present in an amount of 5 to 70 wt. % by weight of the sol in the xerogel-forming composition;

wherein the microporous xerogel comprises a pseudo-boehmite, zirconium oxide, titanium oxide, barium oxide, silicon oxide, aluminum oxide, tin oxide, or a combination comprising at least one of the foregoing oxides;

wherein the polymer is a polyvinyl alcohol, a copolymer of a polyvinyl acetate and a polyvinyl pyrrolidone, a copolymer of polyvinyl alcohol and a polyvinyl pyrrolidone, or a combination comprising at least one of the foregoing polymers;

wherein the glass transition temperature of the polymer changes by less than about 25% after exposure to water and after exposure to an organic electrolyte; and

wherein the microporous xerogel has a porosity of 40 to 80%.