Positive electrode for secondary battery, secondary battery, and method for fabricating positive electrode for secondary battery

Abstract

A positive electrode for a secondary battery which enables both good battery characteristics and electrode strength at a predetermined level, a secondary battery, and a method for fabricating the positive electrode for a secondary battery are provided. The positive electrode for a secondary battery includes a current collector and an active material layer over the current collector. The active material layer includes an active material, graphene, and a binder. A carbon layer is on a surface of the active material. The proportion of the graphene in the active material layer is greater than or equal to 0.1 wt % and less than or equal to 1.0 wt %.

1 . (canceled) 
     
     
         2 . A secondary battery comprising:
 an exterior body comprising:
 a film comprising a material selected from the group consisting of polyethylene, polypropylene, polycarbonate, ionomer and polyamide; 
 a flexible metal thin film; and 
 an insulating synthetic resin film; 
   an electrolyte solution, the exterior body filled with the electrolyte solution; and   a positive electrode comprising:
 a current collector; 
 an active material layer over the current collector, 
   wherein the active material layer comprises an active material, graphene, and a binder, wherein a surface of the active material is partially covered with a carbon layer,   a proportion of the graphene in the active material layer is greater than or equal to 0.1 wt % and less than or equal to 1.0 wt %   
     
     
         3 . The secondary battery according to  claim 2 , wherein the graphene is in direct contact with the active material. 
     
     
         4 . The secondary battery according to  claim 2 , wherein the carbon layer is in direct contact with the current collector. 
     
     
         5 . The secondary battery according to  claim 2 , wherein the flexible metal thin film comprises a material selected from the group consisting of aluminum, stainless steel, copper, and nickel. 
     
     
         6 . The secondary battery according to  claim 2 , wherein the carbon layer is amorphous. 
     
     
         7 . The secondary battery according to  claim 2 , wherein a thickness of the carbon layer is in a range of 5 nm or more and 10 nm or less. 
     
     
         8 . The secondary battery according to  claim 2 , wherein the active material contains lithium. 
     
     
         9 . The secondary battery according to  claim 2 ,
 wherein the active material is represented by general formula LiMPO4, and   wherein M represents at least one of Fe, Mn, Co, and Ni.   
     
     
         10 . The secondary battery according to  claim 2 , wherein the active material is selected from LiCoO2, LiNiO2, LiMnO2, Li2MnO3, LiNixCo1-xO2 (0<x<1), LiNixMn1-xO2 (0<x<1), and LiNixMnyCo1-x-yO2 (x>0, y>0, x+y<1). 
     
     
         11 . The secondary battery according to  claim 2 , wherein a maximum value of discharge capacity (mAh/g) of the positive electrode is more than or equal to 140 mAh/g at a discharging rate of 1 C. 
     
     
         12 . A secondary battery comprising:
 an exterior body comprising:
 a film comprising a material selected from the group consisting of polyethylene, polypropylene, polycarbonate, ionomer and polyamide; 
 a flexible metal thin film; and 
 an insulating synthetic resin film; 
   an electrolyte solution, the exterior body filled with the electrolyte solution; and   a positive electrode comprising:
 a current collector; 
 an active material layer over the current collector, 
   wherein the active material layer comprises an active material, graphene, and a binder,   wherein a surface of the active material is partially covered with a carbon layer,   the graphene contains oxygen at a proportion greater than or equal to 2 atomic % and less than or equal to 20 atomic %, and   a proportion of the graphene in the active material layer is greater than or equal to 0.1 wt % and less than or equal to 1.0 wt %.   
     
     
         13 . The secondary battery according to  claim 12 , wherein the graphene is in direct contact with the active material. 
     
     
         14 . The secondary battery according to  claim 12 , wherein the carbon layer is in direct contact with the current collector. 
     
     
         15 . The secondary battery according to  claim 12 , wherein the flexible metal thin film comprises a material selected from the group consisting of aluminum, stainless steel, copper, and nickel. 
     
     
         16 . The secondary battery according to  claim 12 , wherein the carbon layer is amorphous. 
     
     
         17 . The secondary battery according to  claim 12 , wherein a thickness of the carbon layer is in a range of 5 nm or more and 10 nm or less. 
     
     
         18 . The secondary battery according to  claim 12 , wherein the active material contains lithium. 
     
     
         19 . The secondary battery according to  claim 12 ,
 wherein the active material is represented by general formula LiMPO4, and   wherein M represents at least one of Fe, Mn, Co, and Ni.   
     
     
         20 . The secondary battery according to  claim 12 , wherein a maximum value of discharge capacity (mAh/g) of the positive electrode is more than or equal to 140 mAh/g at a discharging rate of 1 C. 
     
     
         21 . An electric vehicle comprising:
 a control circuit;   a driving device; and   a battery comprising:
 an exterior body comprising:
 a film comprising a material selected from the group consisting of polyethylene, polypropylene, polycarbonate, ionomer and polyamide; 
 a flexible metal thin film; and 
 an insulating synthetic resin film; 
 
 an electrolyte solution, the exterior body filled with the electrolyte solution; and 
 a positive electrode comprising: 
 a current collector; and 
 an active material layer over the current collector, 
   wherein output of power of the battery is adjusted by the control circuit,   wherein the power is supplied to the driving device,   wherein the driving device includes a DC motor or an AC motor,   wherein the active material layer comprises an active material, graphene, and a binder,   wherein a surface of the active material is partially covered with a carbon layer, and   wherein a proportion of the graphene in the active material layer is greater than or equal to 0.1 wt % and less than or equal to 1.0 wt %.