Electrode assembly for secondary battery and method for fabricating the same

Abstract

A roll electrode assembly of a secondary battery includes a positive electrode rolled having a plurality of turns, a negative electrode rolled having a plurality of turns, and first and second separators each rolled to have a plurality of turns. Each turn of the first separator is disposed between each outer surface of the turns of the negative electrode and each inner surface of the turns of the positive electrode. Each turn of the second separator is disposed between each outer surface of the turns of the positive electrode and each inner surface of the turns of the negative electrode. The thickness of the second separator is thinner than that of the first separator.

What is claimed is: 
     
       1. A roll electrode assembly of a secondary battery, comprising:
 a positive electrode deposited with a positive active material; 
 a negative electrode deposited with a negative active material and adjacent to the positive electrode; and 
 successive turns of a separator disposed between the positive and negative electrodes, the successive turns having alternately different thicknesses, 
 wherein, the adjacent positive and negative electrodes have variable negative-to-positive active material ratio capacity ratios, and a thickness of the separator disposed between a portion of the adjacent positive and negative electrodes where the negative-to-positive active material capacity ratio is less than 1 is greater than that a thickness of the other another portion where the capacity ratio is higher than 1. 
 
     
     
       2. A roll electrode assembly of a secondary battery, comprising:
 a positive electrode rolled having a plurality of turns; 
 a negative electrode rolled having a plurality of turns, each turn of the negative electrode being adjacent to each turn of the positive electrode; and 
 first and second separators each rolled to have a plurality of turns, each turn of the first separator being disposed between each outer surface of the turns of the negative electrode and each inner surface of the turns of the positive electrode, and each turn of the second separator being disposed between each outer surface of the turns of the positive electrode and each inner surface of the turns of the negative electrode, 
 wherein the thickness of the first separator is greater than that of the second separator, and 
 wherein when the roll electrode assembly is for a battery having, in a cross section, a straight portion and a curved portion, with the thickness of the first and the second separators equal in the straight portion. 
 
     
     
       3. The roll electrode assembly of  claim 2  wherein the thickness of the first separator is 2-3 times that of the second separator. 
     
     
       4. The roll electrode assembly of  claim 2  wherein the thickness of the first separator is about 30-45 μm. 
     
     
       5. The roll electrode assembly of  claim 2  wherein the thickness of the second separator about 15-23 μm. 
     
     
       6. A roll electrode assembly of a secondary battery, comprising:
 a positive electrode deposited with a positive active material; 
 a negative electrode deposited with a negative active material and adjacent to the positive electrode; 
 a first separator disposed between the positive and negative electrodes; and 
 a second separator disposed between the positive and negative electrodes, wherein,;  
 the adjacent positive and negative electrodes have having variable negative-to-positive active material ratio capacity ratios, and the first and second separators having different thicknesses, with a thickness of the first separator disposed between a portion of the adjacent positive and negative electrodes where the negative-to-positive active material capacity ratio is less than 1 is being greater than that of a thickness of the second separator disposed between a portion of the adjacent positive and negative electrodes where the negative-to-positive active material capacity ratio is higher than 1. 
 
     
     
       7. The roll electrode assembly of  claim 6  wherein the thickness of the first separator is 2-3 times that of the second separator. 
     
     
       8. The roll electrode assembly of  claim 6  wherein the thickness of the first separator is about 30-45 μm. 
     
     
       9. The roll electrode assembly of  claim 6  wherein the thickness of the second separator is about 15-23 μm. 
     
     
       10. A roll electrode assembly of a secondary battery, comprising:
 a positive electrode rolled into a plurality of turns;   a negative electrode rolled into a plurality of turns, each turn of the negative electrode being adjacent to each turn of the positive electrode; and   first and second separators each rolled to have a plurality of turns, each turn of the first separator being disposed between a corresponding neighboring outer surface of the turns of the negative electrode and a corresponding neighboring inner surface of the turns of the positive electrode, and each turn of the second separator being disposed between a corresponding neighboring outer surface of the turns of the positive electrode and a corresponding neighboring inner surface of the turns of the negative electrode;   a thickness of the first separator being greater than a thickness of the second separator in a curved portion of a cross-section of the secondary battery, and the thicknesses of the first and the second separators being equal in a straight portion of the cross-section of the secondary battery.    
     
     
       11. A roll electrode assembly of a secondary battery, comprising:
 a positive electrode deposited with a positive active material;   a negative electrode deposited with a negative active material neighboring the positive electrode;   a first separator disposed between the positive and negative electrodes; and   a second separator disposed between the positive and negative electrodes;   adjacent positive and negative electrodes having variable negative-to-positive active material capacity ratios, and the first and the second separators having different thicknesses alternately positioned between the positive and negative electrodes, with a thickness of the first separator disposed between a portion of the adjacent positive and negative electrodes where the negative-to-positive active material capacity ratio is less than 1 being greater than a thickness of the second separator disposed between a portion of the adjacent positive and negative electrodes where the negative-to-positive active material capacity ratio is higher than 1; and   the thicknesses of the first and the second separators being equal in a straight portion of a cross-section of the secondary battery.