Battery separator with improved oxidation stability

Abstract

The invention relates to a thermoplastic polymer-based battery separator, which contains a compound of formula R(OR 1 ) n (COOM x+ 1/x ) m . In said formula, R represents a non-aromatic hydrocarbon group comprising between 10 and 4,200 carbon atoms, which can be interrupted by oxygen atoms, R 1 represents H, —(CH 2 ) k COOM x+ 1/x or —(CH 2 ) k —SO 3 M x+ 1/x , whereby k stands for 1 or 2, M represents an alkali or earth alkaline metal ion, H + or NH 4 + , whereby not all variables of M are defined simultaneously as H + , n stands for 0 or 1, m stands for 0 or a whole number from 10 to 1,400 and x stands for 1 or 2. The ratio of oxygen atoms to carbon atoms in the compound according to the aforementioned formula ranges between 1:1.5 and 1:30 and n and m cannot simultaneously represent zero.

1 . Battery separator based on thermoplastic, ultra-high molecular-weight polyolefin with an average molecular weight by weight of at least 300,000, comprising, relative to the sum of the weights of filler and polyolefin, 10 to 100 wt.-% polyolefin and 0 to 90 wt.-% filler, and, relative to the weight of the separator, 5 to 35 wt.-% oil and 0.5 to 5.0 wt.-% of a compound according to the Formula (I) 
         R(OR 1 ) n (COOM X+   1/x ) m   (I) 
       in which 
 R is a non-aromatic hydrocarbon radical with 10 to 4200 hydrocarbon atoms, which can be interrupted by oxygen atoms,  
 R 1  is H, —(CH 2 ) k COOM X+   1/x  or —(CH 2 ) k —SO 3 M X+   1/x , where k is 1 or 2,  
 M is an alkali metal or alkaline-earth metal ion, H +  or NH 4   + , where not all the M variables simultaneously have the meaning H + ,  
 n is 0 or 1,  
 m is 0 or an integer from 10 to 1400 and  
 x is 1 or 2,  
 the ratio of oxygen atoms to carbon atoms in the compound according to Formula (I) lying in the range between 1:1.5 to 1:30 and m and n not being able to simultaneously be 0.  
 
     
     
         2 . Battery separator according to  claim 1 , wherein 
 R is a hydrocarbon radical with 10 to 180 carbon atoms, which can be interrupted by 1 to 60 oxygen atoms,    n is 1,    m is 0 and    x is 1 or 2.    
     
     
         3 . Battery separator according to  claim 2 , wherein R is a hydrocarbon radical of the formula R 2 —[(OC 2 H 4 ) p  (OC 3 H 6 ) q ]—, in which 
 R 2  is an alkyl radical with 10 to 30 carbon atoms,    p is an integer from 0 to 30 and/or    q is an integer from 0 to 30.    
     
     
         4 . Battery separator according to  claim 3 , wherein 
 p is an integer from 0 to 10 and    q is an integer from 0 to 10.    
     
     
         5 . Battery separator according to  claim 3 , wherein the sum of p and q is smaller than or equal to 10.  
     
     
         6 . Battery separator according to  claim 2 , wherein R 1  is H.  
     
     
         7 . Battery separator according to  claim 1 , wherein 
 R is an alkane radical with 20 to 4200 carbon atoms,    M is an alkali metal or alkaline-earth metal ion, H +  or NH 4   + , where not all the variables M simultaneously have the meaning H + ,    n is 0,    m is an integer from 10 to 1400 and    x is 1 or 2.    
     
     
         8 . Battery separator according to  claim 7 , wherein R is an alkane radical with 50 to 750 carbon atoms.  
     
     
         9 . Battery separator according to  claim 7 , wherein the compound according to Formula (I) is a poly(meth)acrylic acid, whose acid groups are at least partly neutralized.  
     
     
         10 . Battery separator according to  claim 9 , wherein at least 40% of the acid groups of the poly(meth)acrylic acid are neutralized.  
     
     
         11 . Battery separator according to  claim 7 , wherein M is Li + , Na +  or K + .  
     
     
         12 . Battery separator according to  claim 7 , wherein the poly(meth)acrylic acid has an average molar mass M w  of 1,000 to 100,000 g/mol.  
     
     
         13 . Battery separator based on thermoplastic, ultra-high molecular-weight polyolefin with an average molecular weight by weight of at least 300,000, comprising a component which, when the separator is used for the intended purpose, can form a compound of the Formula (I): 
         R(OR 1 ) n (COOM X+   1/x ) m   (I) 
       in which 
 R is a non-aromatic hydrocarbon radical with 10 to 4200 hydrocarbon atoms, which can be interrupted by oxygen atoms,  
 R 1  is H, —(CH 2 ) k COOM X+   1/x  or —(CH 2 ) k —SO 3 M X+   1/x , k being 1 or 2,  
 M is an alkali metal or alkaline-earth metal ion, H +  or NH 4   + , where not all the M variables simultaneously have the meaning H + ,  
 n is 0 or 1,  
 m is 0 or an integer from 10 to 1400 and  
 x is 1 or 2,  
 the ratio of oxygen atoms to carbon atoms in the compound according to Formula (I) lying in the range between 1:1.5 to 1:30 and m and n not being able to simultaneously be 0.  
 
     
     
         14 . Lead-sulphuric acid accumulator with at least two oppositely-charged electrode plates, comprising at least one battery separator according to  claim 1 .  
     
     
         15 . Process for the preparation of a battery separator according to  claim 1 , wherein a compound with the Formula (I) or a solution of a compound with the Formula (I) is applied to a battery separator and the separator is then optionally dried.  
     
     
         16 . Process for the preparation of a battery separator according to  claim 1 , wherein a homogenous mixture of ultra-high molecular-weight thermoplastic polyolefin, at least one compound with the Formula (I) and optionally filler and further additives are prepared, formed into a web-shaped material and then one or more of the further additives are optionally removed.  
     
     
         17 . Method for the preparation of battery separators comprising the addition of a compound with the Formula (I) to a separator.  
     
     
         18 . Method for the improvement of the oxidation resistance of battery separators comprising the addition of a compound with the Formula (I) to a separator.  
     
     
         19 . Battery separator according to  claim 4 , wherein the sum of p and q is smaller than or equal to 10.  
     
     
         20 . Battery separator according to  claim 8 , wherein the compound according to Formula (I) is a poly(meth)acrylic acid, whose acid groups are at least partly neutralized.  
     
     
         21 . Battery separator according to  claim 20 , wherein at least 40% of the acid groups of the poly(meth)acrylic acid are neutralized.