Nonaqueous electrolyte secondary battery, and method for producing a nonaqueous electrolyte secondary battery

Abstract

The present invention provides a technology that allows supplying stably a nonaqueous electrolyte secondary battery having a high capacity retention rate and being excellent in resistance to deterioration. The nonaqueous electrolyte secondary battery disclosed herein is provided with a wound electrode body resulting from winding a stack 10 having a stacking of a positive electrode 50 and a negative electrode 60 across separators 70 . The positive electrode 50 has a foil-shaped positive electrode collector 52 and a positive electrode mix layer 54 . Each separator 70 has a resin substrate layer 72 and a heat resistance layer 74 . In the nonaqueous electrolyte secondary battery disclosed herein, the peel strength of a boundary between the resin substrate layer and the heat resistance layer is 16 N/m or more and 155 N/m or less, and the density of the positive electrode mix layer is 2.3 g/cc or more and 2.6 g/cc or less. In this the nonaqueous electrolyte secondary battery, sufficient flexibility of the stack 10 as a whole can be secured even when using high-peel strength separators 70 in order to increase resistance to deterioration. Drops in production efficiency can be suitably suppressed as a result.

1 . A nonaqueous electrolyte secondary battery provided with a wound electrode body resulting from winding a stack having a stacking of a positive electrode and a negative electrode across a separator,
 wherein the positive electrode has a foil-shaped positive electrode collector, and a positive electrode mix layer provided on a surface of the positive electrode collector;   the separator has a resin substrate layer containing an insulating resin, and a heat resistance layer formed on one face of the resin substrate layer; and   the peel strength of a boundary between the resin substrate layer and the heat resistance layer is 16 N/m or more and 155 N/m or less, and the density of the positive electrode mix layer is 2.3 g/cc or more and 2.6 g/cc or less.   
     
     
         2 . The nonaqueous electrolyte secondary battery according to  claim 1 , wherein the heat resistance layer is formed on a surface of the resin substrate layer so as to oppose the positive electrode mix layer. 
     
     
         3 . The nonaqueous electrolyte secondary battery according to  claim 1 , wherein the peel strength of the boundary between the resin substrate layer and the heat resistance layer is 21 N/m or more and 102 N/m or less. 
     
     
         4 . The nonaqueous electrolyte secondary battery according to  claim 1 , wherein a ratio of the thickness of the heat resistance layer to the thickness of the separator is 0.1 to 0.4. 
     
     
         5 . The nonaqueous electrolyte secondary battery according to  claim 1 , wherein the heat resistance layer contains a filler made of an inorganic material, and a binder, and a weight ratio of the filler and the binder is 90:10 to 92:8. 
     
     
         6 . A method for producing a nonaqueous electrolyte secondary battery in which a wound electrode body and a nonaqueous electrolyte solution are accommodated in a case, the method comprising:
 a winding step of producing a wound electrode body by stacking a positive electrode and a negative electrode across a separator to produce a stack, followed by winding the stack; and   a sealing step of accommodating the wound electrode body and the nonaqueous electrolyte solution in the case, followed by sealing the case,   wherein the positive electrode has a foil-shaped positive electrode collector, and a positive electrode mix layer provided on a surface of the positive electrode collector; and   the separator has a resin substrate layer containing an insulating resin, and a heat resistance layer formed on one face of the resin substrate layer; and   the peel strength of a boundary between the resin substrate layer and the heat resistance layer is set to 16 N/m or more and 155 N/m or less and the density of the positive electrode mix layer is set to 2.3 g/cc or more and 2.6 g/cc or less.   
     
     
         7 . The method for producing a nonaqueous electrolyte secondary battery according to  claim 6 , wherein the tension in the positive electrode and the negative electrode during winding of the stack is set to be higher than the tension in the separator. 
     
     
         8 . The method for producing a nonaqueous electrolyte secondary battery according to  claim 7 , wherein the tension in the positive electrode and the negative electrode is adjusted to be in a range of 2.5 N to 12.0 N, and the tension in the separator is adjusted to be in a range of 1.0 N to 6.0 N.