Separators for electrochemical cells
View Patent ↗Provided are separators for use in batteries and capacitors comprising (a) at least 50% by weight of an aluminum oxide and (b) an organic polymer, wherein the aluminum oxide is surface modified by treatment with an organic acid to form a modified aluminum oxide, and wherein the treatment provides dispersibility of the aluminum oxide in aprotic solvents such as N-methyl pyrrolidone. Preferably, the organic acid is a sulfonic acid, such as p-toluenesulfonic acid. Also preferably, the organic polymer is a fluorinated polymer, such as polyvinylidene fluoride. Also provided are electrochemical cells and capacitors comprising such separators.
1. A separator for an electric current producing cell comprising a microporous layer, the microporous layer comprising:
(a) a modified hydrated aluminum oxide formed by surface treating hydrated aluminum oxide with a sulfonic acid to provide the modified hydrated aluminum oxide with dispersibility in aprotic solvents; and
(b) an organic polymer that is not soluble in water or alcohols.
2. The separator of claim 1 , wherein the microporous layer comprises a xerogel layer.
3. The separator of claim 2 , wherein the xerogel layer is a continuous xerogel layer and has a porosity of at least 30%.
4. The separator of claim 1 , wherein the organic polymer comprises a polyvinylidene fluoride polymer.
5. The separator of claim 1 , where the organic polymer comprises a first fluorinated organic monomer and a second organic monomer.
6. The separator of claim 1 , wherein the sulfonic acid is an aryl sulfonic acid.
7. The separator of claim 1 , wherein the hydrated aluminum oxide comprises a hydrated aluminum oxide of the formula Al 2 O 3 .xH 2 0, wherein x is in the range of 1.0 to 1.5.
8. The separator of claim 1 , wherein the separator comprises 50% to 85% by weight of the modified hydrated aluminum oxide.
9. The separator of claim 1 , wherein the microporous layer has an average pore diameter from 2 nm to 70 nm.
10. A separator for an electric current producing cell comprising a microporous layer, the microporous layer comprising:
(a) a modified hydrated aluminum oxide formed by surface treating hydrated aluminum oxide with a sulfonic acid to provide the modified hydrated aluminum oxide with dispersibility in aprotic solvents; and
(b) an organic polymer;
wherein the separator is flame retardant and does not melt at temperatures lower than 300° C.
11. The separator of claim 10 , wherein the organic polymer is not soluble in water or alcohols.
12. The separator of claim 10 , wherein the organic polymer is a fluorinated organic polymer.
13. An electrochemical cell comprising:
an anode,
a cathode,
an organic electrolyte comprising a lithium salt, and
a separator interposed between the anode and the cathode, wherein the separator comprises a microporous layer, the microporous layer comprising:
(a) a modified hydrated aluminum oxide formed by surface treating hydrated aluminum oxide with a sulfonic acid to provide the modified hydrated aluminum oxide with dispersibility in aprotic solvents; and
(b) an organic polymer that is not soluble in water or alcohols.
14. The electrochemical cells of claim 13 , wherein the anode active material of the anode is lithium.
15. The electrochemical cell of claim 13 , wherein the microporous layer is a xerogel layer.
16. The electrochemical cell of claim 15 , wherein the xerogel layer is a continuous xerogel layer and has a porosity of at least 30%.
17. The electrochemical cell of claim 13 , wherein the organic polymer comprises a polyvinylidene fluoride polymer.
18. The electrochemical cell of claim 13 , where the organic polymer comprises a first fluorinated organic monomer and a second organic monomer.
19. The electrochemical cell of claim 13 , wherein the sulfonic acid is an aryl sulfonic acid.
20. The electrochemical cell of claim 13 , wherein the hydrated aluminum oxide comprises a hydrated aluminum oxide of the formula Al 2 O 3 .xH 2 0, wherein x is in the range of 1.0 to 1.5.
21. The electrochemical cell of claim 13 , wherein the separator comprises 50% to 85% by weight of the modified hydrated aluminum oxide.
22. The electrochemical cell of claim 13 , wherein the microporous layer has an average pore diameter from 2 nm to 70 nm.
23. A method of making a battery separator for use in an electric current producing cell comprising the steps of:
(a) preparing a dispersion of modified aluminum oxide, wherein the modified hydrated aluminum oxide has been formed by treatment with a sulfonic acid to provide the modified hydrated aluminum oxide with dispersibility in aprotic solvents;
(b) preparing an organic polymer solution comprising an organic polymer that is not soluble in water or alcohols;
(c) mixing the dispersion of Step (a) and the solution of Step (b); and
(d) coating the mixture of Step (c) onto a substrate.
24. The method of claim 23 , wherein the substrate is a release substrate and the method further comprises the steps of: (e) drying the coating and (f) delaminating the dry coating from the release substrate.
25. The method of claim 23 , wherein the substrate is a porous separator material.
26. The method of claim 25 , wherein the porous separator material is a polyolefin separator material.
27. A method of making an electric current producing cell comprising the steps of:
(a) providing an anode;
(b) providing a cathode; and
(c) interposing a microporous separator between the anode and the cathode to form a separator/electrode cell, wherein the microporous separator comprises a microporous layer comprising: a modified hydrated aluminum oxide formed by surface treating hydrated aluminum oxide with a sulfonic acid to provide the modified hydrated aluminum oxide with dispersibility in aprotic solvents; and an organic polymer that is not soluble in water or alcohols.
28. The method of claim 27 , wherein there are further steps of:
(d) enclosing the separator/electrode cell in a casing;
(e) filling the casing with electrolyte; and
(f) sealing the casing.
29. The method of claim 27 , wherein the microporous layer comprises a xerogel layer.
30. The method of claim 27 , wherein the microporous layer comprises a continuous xerogel layer with a porosity of at least 30%.
31. The method of claim 27 , wherein the organic polymer comprises a polyvinylidene fluoride polymer.
32. The method of claim 27 , wherein the organic polymer comprises a first fluorinated organic monomer and a second organic monomer.
33. The method of claim 27 , wherein the sulfonic acid is an aryl sulfonic acid.
34. The method of claim 27 , wherein the hydrated aluminum oxide comprises a hydrated aluminum oxide of the formula Al 2 O 3 .xH 2 0, wherein x is in the range of 1.0 to 1.5.
35. The method of claim 27 , wherein the separator comprises 50% to 85% by weight of the modified hydrated aluminum oxide.
36. The method of claim 27 , wherein the microporous layer has an average pore diameter from 2 nm to 70 nm.