Rechargeable lithium battery

Abstract

The present invention provides a lithium secondary battery having high-capacity as well as good cycle characteristics. The lithium secondary battery includes a positive electrode comprising a positive active material, a negative electrode comprising a negative active material and an electrolyte. The negative active material includes graphite particles combined to Si particulate. The electrolyte includes a solvent, a polyether modified silicone oil where a linear polyether chain is linked to a polysiloxane chain, and a solute comprising a lithium salt.

1 . A lithium secondary battery comprising: 
 a positive electrode comprising a positive active material;    a negative electrode comprising a negative active material where graphite particles and Si particulate are combined; and    an electrolyte, and wherein    the electrolyte comprises    a solvent,    a polyether modified silicone oil where a linear polyether chain is linked to a polysiloxane chain, and    a solute comprising a lithium salt.    
   
   
       2 . The lithium secondary battery of  claim 1 , wherein the polyether modified silicone oil is at least one selected from the group consisting of silicone oils of the following formulas 1 to 3:  
     
       
         
         
             
             
         
       
       wherein, in the above formulas 1 to 3, k ranges from 0 to 50, m ranges from 2 to 10, n ranges from 1 to 50, R is CH 3  or C 6 H 5 , and Z is CH 3  or C 2 H 5 .  
     
   
   
       3 . The lithium secondary battery of  claim 1 , wherein the polyether modified silicone oil is present in an amount of 0.2 wt % to 20 wt %.  
   
   
       4 . The lithium secondary battery of  claim 1 , wherein the lithium salt is at least one selected from the group consisting of LiPF 6 , Li(N(SO 2 C 2 F 5 ) 2 ), Li(N(SO 2 CF 3 ) 2 ), and LiBF 4 .  
   
   
       5 . The lithium secondary battery of  claim 1 , wherein the lithium salt is a mixture of Li(N(SO 2 CF 3 ) 2 ) and LiPF 6 .  
   
   
       6 . A lithium secondary battery comprising: 
 a positive electrode comprising a positive active material;    a negative electrode comprising a negative active material; and    an electrolyte, and    the electrolyte comprises a solvent, a polyether modified silicone oil where a linear polyether chain is linked to a polysiloxane chain, and a solute comprising a lithium salt,    the negative active material comprises a multi-phase alloy powder which comprises Si-phase and SiM-phase, and also comprises either one or both of X-phase or SiX-phase, and    an amount of Si-phase on a surface of the multi-phase alloy powder particle is less than that inside of the particle,    where M is at least one element selected from the group consisting of Ni, Co, As, B, Cr, Cu, Fe, Mg, Mn, and Y, X is at least one element selected from the group consisting of Ag, Cu, and Au, and M and X are not both Cu.    
   
   
       7 . The lithium secondary battery of  claim 6 , wherein the polyether modified silicone oil is at least one selected from the group consisting of silicone oils of the following formulas 1 to 3:  
     
       
         
         
             
             
         
       
       wherein, in the above formulas 1 to 3, k ranges from 0 to 50, m ranges from 2 to 10, n ranges from 1 to 50, R is CH 3  or C 6 H 5 , and Z is CH 3  or C 2 H 5 .  
     
   
   
       8 . The lithium secondary battery of  claim 6 , wherein the polyether modified silicone oil is present in an amount of 0.2 wt % to 20 wt %.  
   
   
       9 . The lithium secondary battery of  claim 6 , wherein the lithium salt is at least one selected from the group consisting of LiPF 6 , Li(N(SO 2 C 2 F 5 ) 2 ), Li(N(SO 2 CF 3 ) 2 ), and LiBF 4 .  
   
   
       10 . The lithium secondary battery of  claim 6 , wherein the lithium salt is a mixture of Li(N(SO 2 CF 3 ) 2 ) and LiPF 6 .  
   
   
       11 . A lithium secondary battery comprising: 
 a positive electrode comprising a positive active material;    a negative electrode comprising a negative active material where graphite particles and Si particulate are combined; and    an electrolyte, andn    the electrolyte comprises    a solvent, and    a solute comprising a lithium salt, and    an LiPF 6  content of the lithium salt ranges less than or equal to 50 mol %.    
   
   
       12 . The lithium secondary battery of  claim 11 , wherein the lithium salt comprises at least one selected from the group consisting of Li(N(SO 2 C 2 F 5 ) 2 ), Li(N(SO 2 CF 3 ) 2 ), and LiBF 4  as a main component.  
   
   
       13 . The lithium secondary battery of  claim 11 , wherein the lithium salt is a mixture of Li(N(SO 2 CF 3 ) 2 ) and LiPF 6 .