Lithium secondary battery

Abstract

There is provided a lithium secondary battery with a negative electrode which comprises a negative electrode active material layer comprising alloy particles comprising silicon and tin and having an average particle diameter of 0.05 to 2 μm as an active material, and a negative electrode current collector, wherein the negative electrode active material layer has a storage capacity of 1,000 to 2,200 mAh/g and a density of 0.9 to 1.5 g/cm 3 and which thereby has a high capacity and a good cycle-characteristic. Thus, a lithium secondary battery having a high capacity and a long life and so designed as to exhibit these characteristics at the same time is provided.

What is claimed is:  
     
         1 . A lithium secondary battery with a negative electrode comprising a negative electrode active material layer comprising alloy particles comprising silicon and tin and having an average particle diameter of 0.05 to 2 μm as an active material, and a current collector, wherein the negative electrode active material layer has a storage capacity of 1,000 to 2,200 mAh/g and a density of 0.9 to 1.5 g/cm 3 .  
     
     
         2 . The lithium secondary battery according to  claim 1 , wherein the negative electrode active material layer has a thickness of 10 to 50 μm.  
     
     
         3 . The lithium secondary battery according to  claim 1 , wherein the negative electrode active material layer comprises an active material, a binder and a conductive auxiliary material.  
     
     
         4 . The lithium secondary battery according to  claim 3 , wherein at least polyvinyl alcohol is used as the binder of the negative electrode active material layer.  
     
     
         5 . A lithium secondary battery comprising a negative electrode comprising a negative electrode active material layer comprising alloy particles as an active material comprising silicon as a major component and a negative electrode current collector, and a positive electrode comprising a positive electrode active material layer and a positive electrode current collector, wherein the positive electrode active material layer and the negative electrode active material layer satisfy the following relationships: 
       ( C   N   ×D   N )/( C   P   ×D   P )≦8 C   N   ×D   N =1,200 to 2,500 mAh/cm 3 C N =1,000 to 2,200 mAh/gD N =0.9 to 1.5 g/cm 3   
       wherein, 
 C N  represents a capacity per unit weight of the negative electrode active material layer;  
 D N  represents the density of the negative electrode active material layer;  
 C P  represents a capacity per unit weight of the positive electrode active material layer; and  
 D P  represents the density of the positive electrode active material layer.  
 
     
     
         6 . The lithium secondary battery according to  claim 5 , wherein the alloy particles comprising silicon as a main component have an average particle diameter of 0.05 to 2 μm.  
     
     
         7 . The lithium secondary battery according to  claim 5 , wherein the alloy particles comprising silicon as a main component are alloy particles comprising silicon and tin.  
     
     
         8 . The lithium secondary battery according to  claim 5 , wherein the negative electrode active material layer has a thickness of 10 to 50 μm.  
     
     
         9 . The lithium secondary battery according to  claim 5 , wherein the positive electrode active material layer has a thickness of 50 to 150 μm.  
     
     
         10 . The lithium secondary battery according to  claim 5 , wherein the negative electrode current collector has a thickness of 6 to 30 μm.  
     
     
         11 . The lithium secondary battery according to  claim 5 , wherein the positive electrode current collector has a thickness of 6 to 30 μm.  
     
     
         12 . The lithium secondary battery according to  claim 5 , wherein the negative electrode active material layer comprises an active material, a binder and a conductive auxiliary material.  
     
     
         13 . The lithium secondary battery according to  claim 12 , wherein at least polyvinyl alcohol is used as the binder of the negative electrode active material layer.