Nonaqueous electrolyte secondary battery

Abstract

A nonaqueous electrolyte secondary battery includes an electrode assembly having a high-density positive electrode in which a positive electrode active material layer is formed on at least one surface of a positive electrode current collector, a high-density negative electrode in which a negative electrode active material layer is formed on at least one surface of a negative electrode current collector, and a separator interposed between the positive and negative electrodes, and has a structure in which the electrode assembly is impregnated with a nonaqueous electrolyte, wherein the specific surface area per unit area of the positive electrode active material layer of the positive electrode is 0.5 to 1.0 times the specific surface area per unit area of the negative electrode active material layer of the negative electrode which opposes the positive electrode with the separator sandwiched between them.

1 - 9 . (canceled)  
     
     
         10 . A nonaqueous electrolyte secondary battery comprising: 
 an electrode assembly having a high-density positive electrode in which a positive electrode active material layer is formed on at least one surface of a positive electrode current collector, a high-density negative electrode in which a negative electrode active material layer is formed on at least one surface of a negative electrode current collector, and a separator interposed between the positive and negative electrodes, and having a structure in which the electrode assembly is impregnated with a nonaqueous electrolyte,    wherein a plurality of grooves are formed in a formation surface of the positive electrode active material layer of the positive electrode, such that end portions of the grooves open at edges of the positive electrode active material layer, and    the grooves are formed at a frequency of 1 to 10 grooves per mm as a length of the positive electrode active material layer, and a sectional area of the grooves, as viewed in a length direction of the grooves, account for a ratio of 1 to 20% of a sectional area of the positive electrode active material layer as viewed in the length direction of the grooves.    
     
     
         11 . A nonaqueous electrolyte secondary battery according to  claim 10 , wherein the high-density positive electrode has a density of not less than 3.0 g/cm 3 , and the high-density negative electrode has a density of not less than 1.3 g/cm 3 .  
     
     
         12 . A nonaqueous electrolyte secondary battery according to  claim 10 , wherein said plurality of grooves are formed by passing the positive electrode having the positive electrode active material layer through a pair of rolls at least one of which is an emboss roll.  
     
     
         13 . A nonaqueous electrolyte secondary battery according to  claim 10 , wherein said plurality of grooves have an inverted trapezoidal sectional shape.  
     
     
         14 . A nonaqueous electrolyte secondary battery according to  claim 10 , wherein said plurality of grooves are formed in the formation surface of the positive electrode active material layer of the positive electrode to make an angle of 45 to 75° with a longitudinal direction of the positive electrode.  
     
     
         15 . A nonaqueous electrolyte secondary battery according to  claim 10 , wherein said plurality of grooves are formed in formation surfaces of positive electrode active material layers on upper and lower surfaces of the positive electrode to make an angle of 45 to 75° with a longitudinal direction of the positive electrode, and the grooves in the upper and lower surfaces cross each other when seen through one surface of the positive electrode.  
     
     
         16 . A nonaqueous electrolyte secondary battery according to  claim 10 , wherein each groove is formed as a curved line in the formation surface of the positive electrode active material layer of the positive electrode.