Methods of preparing separators for electrochemical cells

Abstract

Provided are methods of preparing a separator for an electrochemical cell comprising the steps of (a) coating onto a substrate a liquid mixture comprising an inorganic oxide, an organic polymer, a divinyl ether of an ethylene glycol, and/or an organic carbonate; (b) drying the coating; and (c) delaminating the coating from the substrate to form the separator comprising an inorganic oxide and the organic polymer, wherein the inorganic oxide of step (c) comprises a reaction product of the divinyl ether and/or the organic carbonate with the inorganic oxide of step (a). Preferably, the inorganic oxide of step (c) comprises a hydrated aluminum oxide of the formula Al2O3.H2O, wherein x is less than 1.0, and wherein the hydrated aluminum oxide comprises a reaction product of the divinyl ether and/or organic carbonate with the inorganic oxide of step (a), such as pseudo-boehmite.

Description

Claims

1. A method for preparing a separator for an electrochemical cell, wherein said method comprises the steps of: (a) coating onto a substrate a liquid mixture comprising an inorganic oxide, an organic polymer, and a divinyl ether of an ethylene glycol;(b) drying the coating formed in step (a) to yield a microporous layer; and(c) delaminating said microporous layer from said substrate to form said separator, wherein said separator comprises said microporous layer comprising an inorganic oxide and said organic polymer, wherein said inorganic oxide of step (c) comprises a reaction product of said divinyl ether with said inorganic oxide of step (a).

2. The method of claim 1, wherein said inorganic oxide of step (c) comprises a hydrated aluminum oxide of the formula Al2O3.xH2O, wherein x is less than 1.0 and wherein said hydrated aluminum oxide comprises a reaction product of said divinyl ether with said inorganic oxide of step (a).

3. The method of claim 2, wherein x is less than 0.8.

4. The method of claim 2, wherein x is less than 0.6.

5. The method of claim 1, wherein said inorganic oxide of step (a) is selected from the group consisting of pseudo-boehmites, aluminum oxides, silicon oxides, tin oxides, titanium oxides, and zirconium oxides.

6. The method of claim 1, wherein said separator formed in step (c) is a free-standing porous membrane.

7. The method of claim 1, wherein said microporous layer of step (b) is laminated to an electrode for an electrochemical cell prior to step (c) and said delamination of step (c) forms said separator laminated to said electrode.

8. The method of claim 1, wherein said drying of step (b) comprises drying at a temperature greater than 150° C.

9. The method of claim 8, wherein said drying at a temperature greater than 150° C. increases the tensile strength of said separator at 2 percent elongation and increases the percent elongation of said separator at break compared to drying for the same period of time at a temperature of 140° C. or less.

10. The method of claim 1, wherein said method further comprises a step (d) of drying at a temperature greater than 150° C.

11. The method of claim 1, wherein said substrate is a silicone release substrate.

12. The method of claim 1, wherein the liquid mixture of step (a) further comprises an organic carbonate.

13. The method of claim 1, wherein the liquid mixture of step (a) further comprises ethylene carbonate.

14. A method for preparing a separator for an electrochemical cell, wherein said method comprises the steps of: (a) coating onto a substrate a liquid mixture comprising an inorganic oxide, an organic polymer, and an organic carbonate;(b) drying the coating formed in step (a) to yield a microporous layer; and(c) delaminating said microporous layer from said substrate to form said separator, wherein said separator comprises said microporous layer comprising an inorganic oxide and said organic polymer, wherein said inorganic oxide of step (c) comprises a reaction product of said organic carbonate with said inorganic oxide of step (a).

15. The method of claim 14, wherein said inorganic oxide of step (c) comprises a hydrated aluminum oxide of the formula Al2O3.xH2O, wherein x is less than 1.0 and wherein said hydrated aluminum oxide comprises a reaction product of said organic carbonate with said inorganic oxide of step (a).

16. The method of claim 15, wherein x is less than 0.8.

17. The method of claim 15, wherein x is less than 0.6.

18. The method of claim 14, wherein said inorganic oxide of step (a) is selected from the group consisting of pseudo-boehmites, aluminum oxides, silicon oxides, tin oxides, titanium oxides, and zirconium oxides.

19. A method for preparing a separator for an electrochemical cell, wherein said method comprises the steps of: (a) coating onto a substrate a liquid mixture comprising an inorganic oxide, an organic polymer, a divinyl ether of an ethylene glycol, and an organic carbonate;(b) drying the coating formed in step (a) to yield a microporous layer; and(c) delaminating said microporous layer from said substrate to form said separator, wherein said separator comprises said microporous layer comprising an inorganic oxide and said organic polymer, wherein said inorganic oxide of step (c) comprises a reaction product of said divinyl ether and/or said organic carbonate with said inorganic oxide of step (a).

20. The method of claim 19, wherein said inorganic oxide of step (c) comprises a hydrated aluminum oxide of the formula Al2O3.xH2O, wherein x is less than 1.0 and wherein said hydrated aluminum oxide comprises a reaction product of said organic carbonate with said inorganic oxide of step (a).

21. The method of claim 20, wherein x is less than 0.8.

22. The method of claim 20, wherein x is less than 0.6.

23. The method of claim 19, wherein said inorganic oxide of step (a) is selected from the group consisting of pseudo-boehmites, aluminum oxides, silicon oxides, tin oxides, titanium oxides, and zirconium oxides.

24. The method of claim 19, wherein said separator formed in step (c) is a free-standing porous membrane.

25. The method of claim 19, wherein said microporous layer of step (b) is laminated to an electrode for an electrochemical cell prior to step (c) and said delamination of step (c) forms said separator laminated to said electrode.