SEPARATORS FOR ELECTROCHEMICAL CELLS
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, wherein said separator comprises a microporous layer comprising (a) at least 50% by weight of an aluminum oxide and (b) an organic polymer, wherein said aluminum oxide is surface modified by treatment with an organic acid to form a modified aluminum oxide, and wherein said treatment provides dispersibility of said aluminum oxide in aprotic solvents, and said organic polymer comprises a first fluorinated organic monomer and a second organic monomer or said organic polymer comprises a polyvinylidene fluoride polymer.
2 . The separator of claim 1 , wherein said organic acid is a sulfonic acid.
3 . The separator of claim 2 , wherein said sulfonic acid is an aryl sulfonic acid, preferably a toluenesulfonic acid.
4 . The separator of claim 1 , wherein said organic acid is a carboxylic acid.
5 . The separator of claim 1 , wherein said aluminum oxide comprises a hydrated aluminum oxide of the formula Al 2 O 3 ·xH 2 O, wherein x is in the range of 1.0 to 1.5, and wherein said hydrated aluminum oxide is surface modified by treatment with an organic acid to form a modified hydrated aluminum oxide.
6 . The separator of claim 5 , wherein said separator comprises 60 to 90% by weight of said modified aluminum oxide.
7 . The separator of claim 5 , wherein said microporous layer has an average pore diameter from 2 nm to 70 nm.
8 . The separator of claim 1 , wherein said electric current producing cell is a secondary lithium ion cell, a primary lithium cell, or a capacitor.
9 . The separator of claim 1 , wherein said microporous layer is coated on one or both sides of at least one microporous polyolefin layer.
10 . An electrochemical cell comprising an anode, a cathode, an organic electrolyte comprising a lithium salt, and a separator interposed between said anode and said cathode, wherein said separator comprises a microporous layer comprising (a) at least 50% by weight of an aluminum oxide and (b) an organic polymer, wherein said aluminum oxide is surface modified by treatment with an organic acid to form a modified aluminum oxide, and wherein said treatment provides dispersibility of said aluminum oxide in aprotic solvents, and said organic polymer comprises a first fluorinated organic monomer and a second organic monomer or said organic polymer comprises a polyvinylidene fluoride polymer.
11 . The cell of claim 10 , wherein said organic acid is a sulfonic acid.
12 . The cell of claim 11 , wherein said sulfonic acid is an aryl sulfonic acid, preferably a toluenesulfonic acid.
13 . The cell of claim 10 , wherein said organic acid is a carboxylic acid.
14 . The cell of claim 10 , wherein said aluminum oxide comprises a hydrated aluminum oxide of the formula Al 2 O 3 xH 2 O, wherein x is in the range of 1.0 to 1.5, and wherein said hydrated aluminum oxide is surface modified by treatment with an organic acid to form a modified hydrated aluminum oxide.
15 . The cell of claim 10 , wherein said microporous layer has an average pore diameter from 2 nm to 70 nm.
16 . The cell of claim 10 , wherein said microporous layer is coated on one or both sides of at least one microporous polyolefin layer.
17 . The cell of claim 10 , wherein the anode active material of said anode is lithium.
18 . A capacitor comprising two electrodes, an organic electrolyte comprising a tetraalkyl ammonium salt, and a separator interposed between said two electrodes, wherein said separator comprises a microporous layer comprising (a) at least 50% by weight of an aluminum oxide and (b) an organic polymer, wherein said aluminum oxide is surface modified by treatment with an organic acid to form a modified aluminum oxide, and wherein said treatment provides dispersibility of said aluminum oxide in aprotic solvents, and said organic polymer comprises a first fluorinated organic monomer and a second organic monomer or said organic polymer comprises a polyvinylidene fluoride polymer.
19 . The capacitor of claim 18 , wherein said organic acid is a sulfonic acid.
20 . The capacitor of claim 18 , wherein said inorganic oxide comprises a hydrated aluminum oxide of the formula Al 2 O 3 ·xH 2 O, wherein x is in the range of 1.0 to 1.5, and wherein said aluminum oxide is surface modified by treatment with an organic acid to form a modified aluminum oxide.