Lithium ion secondary battery

Abstract

This application relates to a lithium ion secondary battery comprising a battery core and an electrolyte, wherein the battery core comprises a lithium-manganese-based positive electrode active material; the electrolyte comprises a solvent, a lithium salt and an additive comprising vinylene carbonate; and wherein the weight percentage q of the electrolyte based on the total weight of the positive electrode active material layer in the battery core, the weight percentage r of vinylene carbonate present in the electrolyte, the compaction density s of the negative electrode active material layer in the battery core and the weight percentage p of manganese element present in the positive electrode active material satisfies 0.05≤q·r·s/p≤6, wherein the units of q, r, and p are wt %, and the unit of s is g/cm 3 . The lithium ion secondary battery in this application has relatively high safety performance, cycle performance and storage performance.

1 . A lithium ion secondary battery comprising a battery core and an electrolyte, wherein:
 the battery core comprises a lithium-manganese-based positive electrode active material;   the electrolyte comprises a solvent, a lithium salt and an additive, and the additive comprises vinylene carbonate; and   wherein the weight percentage q of the electrolyte based on the total weight of positive electrode active material layer in the battery core, the weight percentage r of vinylene carbonate present in the electrolyte, the compaction density s of negative electrode active material layer in the battery core and the weight percentage p of manganese element present in the positive electrode active material satisfies the formula (1):   
       
         
           
             
               
                 
                   
                     
                       0 
                       · 
                       05 
                     
                     ≤ 
                     
                       
                         q 
                         · 
                         r 
                         · 
                         s 
                       
                       p 
                     
                     ≤ 
                     6 
                   
                 
                 
                   
                     Formula 
                      
                     
                         
                     
                      
                     
                       ( 
                       1 
                       ) 
                     
                   
                 
               
             
           
         
         in the formula (1), the units of q, r, and p are wt %, and the unit of s is g/cm 3 . 
       
     
     
         2 . The lithium ion secondary battery according to  claim 1 , wherein the weight percentage q of the electrolyte based on the total weight of the positive electrode active material layer in the battery core, the weight percentage r of vinylene carbonate present in the electrolyte, the compaction density s of the negative electrode active material layer in the battery core and the weight percentage p of manganese element present in the positive electrode active material satisfies the formula (2): 
       
         
           
             
               
                 
                   
                     
                       0 
                       · 
                       25 
                     
                     ≤ 
                     
                       
                         q 
                         · 
                         r 
                         · 
                         s 
                       
                       p 
                     
                     ≤ 
                     5 
                   
                 
                 
                   
                     Formula 
                      
                     
                         
                     
                      
                     
                       ( 
                       2 
                       ) 
                     
                   
                 
               
             
           
         
       
       in the formula (2), the units of q, r, and p are wt %, and the unit of s is g/cm 3 . 
     
     
         3 . The lithium ion secondary battery according to  claim 1 , wherein in the lithium ion secondary battery, the ratio of the number of vinylene carbonate molecules to the number of manganese atoms is from 0.1:100 to 1.3:100. 
     
     
         4 . The lithium ion secondary battery according to  claim 1 , wherein the weight percentage q of the electrolyte based on the total weight of the positive electrode active material layer in the battery core is from 20 wt % to 70 wt %. 
     
     
         5 . The lithium ion secondary battery according to  claim 1 , wherein the weight percentage r of vinylene carbonate present in the electrolyte is from 0.01 wt % to 3.5 wt %. 
     
     
         6 . The lithium ion secondary battery according to  claim 1 , wherein:
 the negative electrode active material layer in the battery core has a compaction density s of 1.3 g/cm 3  to 1.65 g/cm 3 .   
     
     
         7 . The lithium ion secondary battery according to  claim 1 , wherein the weight percentage p of manganese element present in the positive electrode active material is from 5 wt % to 50 wt %. 
     
     
         8 . The lithium ion secondary battery according to  claim 1 , wherein the one-sided areal density Q of the negative electrode active material layer is from 70 g/m 2  to 140 g/m 2 . 
     
     
         9 . The lithium ion secondary battery according to  claim 1 , wherein the lithium-manganese-based positive electrode active material comprises one or more of first lithium-manganese-based positive electrode active material represented by chemical formula (1) and second lithium-manganese-based positive electrode active material represented by chemical formula (2),
   Li 1+x Mn a Ni b M 1-a-b O 2-y A y   Chemical formula (1)
   
       in the chemical formula (1), −0.1≤x≤0.2, 0<a<1, 0≤b<1, 0<a+b<1, 0≤y<0.2, and M is one or more of Co, Fe, Cr, Ti, Zn, V, Al, Zr and Ce; A comprises one or more of S, N, F, Cl, Br and I;
   Li 1+z Mn c N 2-c O 4-d B d   Chemical formula (2)
 
 
       in the chemical formula (2), −0.1≤z≤0.2, 0<c≤2, 0≤d<1, and N comprises one or more of Ni, Fe, Cr, Ti, Zn, V, Al, Mg, Zr and Ce, and B comprises one or more of S, N, F, Cl, Br and I. 
     
     
         10 . The lithium ion secondary battery according to  claim 1 , wherein:
 the weight ratio of the second solvent to the first solvent in the electrolyte is from 0 to 4; and   wherein the first solvent is selected from one or more of ethylene carbonate, propylene carbonate, and diethyl carbonate, and the second solvent is selected from one or more of dimethyl carbonate, ethyl methyl carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and methyl butyrate.   
     
     
         11 . The lithium ion secondary battery according to  claim 1 , wherein the positive electrode active material layer has a compaction density of from 3.0 g/cm 3  to 3.6 g/cm 3 . 
     
     
         12 . The lithium ion secondary battery according to  claim 1 , wherein the weight percentage p of manganese element present in the positive electrode active material is from 6 wt % to 35 wt %. 
     
     
         13 . The lithium ion secondary battery according to  claim 1 , wherein the lithium salt is selected from one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bisoxalate borate, lithium difluorooxalate borate, lithium bistrifluoromethanesulfonimide, and lithium bisfluorosulfonimide.