Lithium ion secondary battery

Abstract

The present application relates to a lithium ion secondary battery comprising a cathode, an anode, a separator and an electrolyte; wherein the cathode comprises a positive current collector and a positive material layer, wherein the positive material layer comprises a positive active material with a formula Li x Ni a Co b M c O 2 , M is at least one selected from Mn and Al, 0.95 x 1.2, 0<a<1,0<b<1,0<c<1 and a+b+c=1; wherein the anode comprises a negative current collector and a negative material layer, wherein the negative material layer comprises graphite having a graphitization degree of 92% to 98% and an average particle size D50 of 6 μm to 18 μm as negative active material. The lithium ion secondary battery has long cycle life and high energy density.

1 . A lithium ion secondary battery comprising a cathode, an anode, a separator and an electrolyte, the cathode comprises a positive current collector and a positive material layer, wherein the positive material layer comprises a positive active material with formula Li x Ni a Co b M c O 2 , M is at least one selected from the group consisting of Mn and Al, 0.95 x 1.2,0<a<1,0<b<1,0<c<1 and a+b+c=1;
 wherein the anode comprises a negative current collector and a negative material layer, wherein the negative material layer comprises graphite having a graphitization degree of 92% to 98% and an average particle size D50 of 6 μm to 18 μm as negative active material.   
     
     
         2 . The lithium ion secondary battery according to  claim 1 , wherein the positive active material is at least one selected from the group consisting of LiNi 0.33 Co 0.33 Mn 0.33 O 2 , LiNi 0.5 Co 0.2 Mn 0.3 O 2 , LiNi 0.5 Co 0.25 Mn 0.25 O 2 , LiNi 0.8 Co 0.1 Mn 0.1 O 2 , LiNi 0.85 Co 0.1 Mn 0.05 O 2  and LiNi 0.8 Co 0.15 Al 0.05 O 2 . 
     
     
         3 . The lithium ion secondary battery according to  claim 1 , wherein the positive active material has dopant element at least one selected from the group consisting of Al, Zr, Ti, B, Mg, V, Cr, and F. 
     
     
         4 . The lithium ion secondary battery according to  claim 1 , wherein the positive active material has coating layer and the coating layer contains at least one of the elements selected from Al, Zr, Ti, and B. 
     
     
         5 . The lithium ion secondary battery according to  claim 1 , wherein the average particle diameter D50 of the negative active material is 6 μm to 12 μm. 
     
     
         6 . The lithium ion secondary battery according to  claim 1 , wherein the graphitization degree of the negative active material is 92% to 96%. 
     
     
         7 . The lithium ion secondary battery according to  claim 1 , wherein the negative active material has a coating layer and the coating layer comprises amorphous carbon. 
     
     
         8 . The lithium ion secondary battery according to  claim 7 , wherein the amorphous carbon is obtained by the carbonization of at least one material selected from the group consisting of polyvinyl butyral, bitumen, furfural resin, epoxy resin or phenolic resin. 
     
     
         9 . The lithium ion secondary battery according to  claim 7 , wherein the content of the amorphous carbon is 2% to 13%, based on the total weight of the negative active material. 
     
     
         10 . The lithium ion secondary battery according to  claim 7 , wherein the content of the amorphous carbon is 5% to 10%, based on the total weight of the negative active material. 
     
     
         11 . The lithium ion secondary battery according to  claim 1 , wherein the content of the positive active material is 92% to 98%, based on the total weight of the positive material layer; and the content of the negative active material is 92% to 98%, based on the total weight of the negative material layer.