Lithium secondary battery

Abstract

A lithium secondary battery including: an electrode group, a non-aqueous electrolyte and a battery case housing the electrode group and the non-aqueous electrolyte, the electrode group including a positive electrode, a negative electrode and a separator layer interposed between the positive electrode and the negative electrode, wherein an end-of-charge voltage and an end-of-discharge voltage are set in such a manner that the electrode group has an energy density of not less than 700 Wh/L, the separator layer includes a porous heat-resistant layer, and a short circuit area A produced when an internal short circuit has occurred between the positive electrode and the negative electrode, and a reduced area B of the porous heat-resistant layer that is produced by heat generation satisfy 1≦(A+B)/A≧10.

1 . A lithium secondary battery comprising: an electrode group, a non-aqueous electrolyte and a battery case housing said electrode group and said non-aqueous electrolyte, said electrode group including a positive electrode, a negative electrode and a separator layer interposed between said positive electrode and said negative electrode, 
 wherein an end-of-charge voltage and an end-of-discharge voltage are set in such a manner that said electrode group has an energy density of not less than 700 Wh/L,    said separator layer includes a porous resin membrane and a porous heat-resistant layer, said porous heat-resistant layer being provided on a surface of said porous resin membrane,    said separator layer has a thickness of not more than 24 μm, and    a short circuit area A produced when an internal short circuit has occurred between said positive electrode and said negative electrode, and a reduced area B of said porous heat-resistant layer that is produced by heat generation satisfy 1≦(A+B)/A≦10.    
   
   
       2 . The lithium secondary battery in accordance with  claim 1 , wherein said separator layer has a thickness of not less than 12.5 μm.  
   
   
       3 . The lithium secondary battery in accordance with  claim 1 , 
 wherein said porous heat-resistant layer has a thickness of not less than 1 μm and not more than 10 μm.    
   
   
       4 . The lithium secondary battery in accordance with  claim 1 , 
 wherein said porous heat-resistant layer includes a heat-resistant resin.    
   
   
       5 . The lithium secondary battery in accordance with  claim 1 , 
 wherein said porous heat-resistant layer is located at said positive electrode side of said porous resin membrane.    
   
   
       6 . The lithium secondary battery in accordance with  claim 1 , 
 wherein said porous heat-resistant layer has an area larger than that of an active material layer of said negative electrode.    
   
   
       7 . The lithium secondary battery in accordance with  claim 1 , 
 wherein said negative electrode includes at least one selected from the group consisting of a lithium metal and a substance comprising an element capable of being alloyed with lithium.    
   
   
       8 . The lithium secondary battery in accordance with  claim 1 , 
 wherein said positive electrode includes a lithium-containing composite oxide including Ni element.    
   
   
       9 . The lithium secondary battery in accordance with  claim 1 , 
 wherein said end-of-charge voltage is set to a voltage higher than 4.2 V.    
   
   
       10 . The lithium secondary battery in accordance with  claim 1 , 
 wherein a ratio of a thickness A of said porous resin membrane to a thickness B of said porous heat-resistant layer, A/B, satisfies 2.4≦A/B≦8.    
   
   
       11 . A lithium secondary battery comprising: an electrode group, a non-aqueous electrolyte and a battery case housing said electrode group and said non-aqueous electrolyte, said electrode group including a positive electrode, a negative electrode and a separator layer interposed between said positive electrode and said negative electrode, 
 wherein an end-of-charge voltage and an end-of-discharge voltage are set in such a manner that said electrode group has an energy density of not less than 700 Wh/L,    said separator layer includes a porous resin membrane and a porous heat-resistant layer, and said porous heat-resistant layer including an insulating filler and a binder,    said separator layer has a thickness of not more than 24 μm, and    a short circuit area A produced when an internal short circuit has occurred between said positive electrode and said negative electrode, and a reduced area B of said porous heat-resistant layer that is produced by heat generation satisfy 1≦(A+B)/A≦10.    
   
   
       12 . The lithium secondary battery in accordance with  claim 11 , 
 wherein said separator layer has a thickness of not less than 12.5 μm.    
   
   
       13 . The lithium secondary battery in accordance with  claim 11 , 
 said porous heat-resistant layer has a thickness of not less than 1 μm and not more than 10 μm.    
   
   
       14 . The lithium secondary battery in accordance with  claim 11 , 
 wherein said porous heat-resistant layer is provided on a surface of said positive electrode.    
   
   
       15 . The lithium secondary battery in accordance with  claim 11 , 
 wherein said negative electrode includes at least one selected from the group consisting of a lithium metal and a substance comprising an element capable of being alloyed with lithium.    
   
   
       16 . The lithium secondary battery in accordance with  claim 11 , 
 wherein said positive electrode includes a lithium-containing composite oxide containing Ni element.    
   
   
       17 . The lithium secondary battery in accordance with  claim 11 , 
 wherein said end-of-charge voltage is set to a voltage higher than 4.2 V.