Method for forming negative electrode and method for manufacturing lithium secondary battery

Abstract

The number of steps is reduced in the formation process of an electrode. Deterioration of the electrode is suppressed. A highly reliable lithium secondary battery is provided by suppressing the deterioration of the electrode. A method for forming a negative electrode and a method for manufacturing a lithium secondary battery including the negative electrode are provided. In the method for forming the negative electrode, graphene oxide, a plurality of particulate negative electrode active materials, and a precursor of polyimide are mixed to form slurry; the slurry is applied over a negative electrode current collector; and the slurry applied over the negative electrode current collector is heated at a temperature higher than or equal to 200° C. and lower than or equal to 400° C. so that the precursor of the polyimide is imidized. The graphene oxide is reduced in heating the slurry to imidize the precursor of the polyimide.

1 . (canceled) 
     
     
         2 . A negative electrode comprising:
 a current collector; and   a negative electrode active material layer over and in contact with the current collector, the negative electrode active material layer comprising:
 an active material particle; 
 a binder comprising polyimide; and 
 a graphene and a graphene oxide covering the active material particle. 
   
     
     
         3 . The negative electrode according to  claim 2 ,
 wherein the active material comprises a silicon.   
     
     
         4 . The negative electrode according to  claim 2 ,
 wherein an average diameter of the active material particle is lower than 3 μm.   
     
     
         5 . The negative electrode according to  claim 2 ,
 wherein a proportion of oxygen atoms in a total number of carbon atoms, the oxygen atoms, and nitrogen atoms of the graphene oxide is greater than 15 at. %.   
     
     
         6 . The negative electrode according to  claim 2 ,
 wherein the current collector is titanium.   
     
     
         7 . A power storage device comprising:
 the negative electrode according to  claim 2 ;   a positive electrode; and   an electrolyte provided between the negative electrode and the positive electrode.   
     
     
         8 . A negative electrode comprising:
 a current collector; and   a negative electrode active material layer over and in contact with the current collector, the negative electrode active material layer comprising:
 a plurality of active material particles; 
 a binder comprising polyimide; and 
 a graphene and a graphene oxide covering the plurality of active material particles. 
   
     
     
         9 . The negative electrode according to  claim 8 ,
 wherein the active material comprises a silicon.   
     
     
         10 . The negative electrode according to  claim 8 ,
 wherein an average diameter of the plurality of active material particles is lower than 3 μm.   
     
     
         11 . The negative electrode according to  claim 8 ,
 wherein a proportion of oxygen atoms in a total number of carbon atoms, the oxygen atoms, and nitrogen atoms of the graphene oxide is greater than 15 at. %.   
     
     
         12 . The negative electrode according to  claim 8 ,
 wherein the current collector is titanium.   
     
     
         13 . A power storage device comprising:
 the negative electrode according to  claim 8 ;   a positive electrode; and   an electrolyte provided between the negative electrode and the positive electrode.   
     
     
         14 . A negative electrode comprising:
 a current collector; and   a negative electrode active material layer over and in contact with the current collector, the negative electrode active material layer comprising:
 a plurality of active material particles; 
 a binder; and 
 a graphene and a graphene oxide covering the plurality of active material particles, 
   wherein a decomposed temperature of the binder is higher than 200° C.   
     
     
         15 . The negative electrode according to  claim 14 ,
 wherein the binder comprises polyimide.   
     
     
         16 . The negative electrode according to  claim 14 ,
 wherein the active material comprises a silicon.   
     
     
         17 . The negative electrode according to  claim 8 ,
 wherein an average diameter of the plurality of active material particles is lower than 3 μm.   
     
     
         18 . The negative electrode according to  claim 8 ,
 wherein a proportion of oxygen atoms in a total number of carbon atoms, the oxygen atoms, and nitrogen atoms of the graphene oxide is greater than 15 at. %.   
     
     
         19 . The negative electrode according to  claim 8 ,
 wherein the current collector is titanium.   
     
     
         20 . A power storage device comprising:
 the negative electrode according to  claim 8 ;   a positive electrode; and   an electrolyte provided between the negative electrode and the positive electrode.