Separators for electrochemical cells

Abstract

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.

What is claimed is: 
     
         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.