Positive electrode for nonaqueous secondary battery, method for forming the same, nonaqueous secondary battery, and electrical device

Abstract

A positive electrode for a nonaqueous secondary battery including an active material layer which has sufficient electron conductivity with a low ratio of a conductive additive is provided. A positive electrode for a nonaqueous secondary battery including an active material layer which is highly filled with an active material, id est, including the active material and a low ratio of a conductive additive. The active material layer includes a plurality of particles of an active material with a layered rock salt structure, graphene that is in surface contact with the plurality of particles of the active material, and a binder.

1 . (canceled) 
     
     
         2 . A positive electrode comprising:
 a current collector; and   an active material layer over the current collector, the active material layer comprising:
 first particles of an active material having a layered rock salt structure; and 
 a piece of graphene, 
   wherein the first particles has an average primary particle diameter of less than or equal to 3.0 μm.   
     
     
         3 . The positive electrode according to  claim 2 , wherein the active material comprises lithium and a metal selected from nickel, manganese and cobalt. 
     
     
         4 . The positive electrode according to  claim 2 , wherein the active material is selected from LiCoO 2 , LiNiO 2 , LiMnO 2 , Li 2 MnO 3 , LiNi x Co 1-x O 2  (0<x<1), LiNi x Mn 1-x O 2  (0<x<1), and LiNi x Mn y Co 1-x-y O 2  (x>0, y>0, x+y<1). 
     
     
         5 . The positive electrode according to  claim 2 ,
 wherein the active material layer comprises second particles of the active material having a layered rock salt structure, and   wherein the second particles has a different average primary particle diameter from the first particles.   
     
     
         6 . The positive electrode according to  claim 2 , wherein a length of one side of the piece of graphene is greater than or equal to 50 nm and less than or equal to 100 μm. 
     
     
         7 . The positive electrode according to  claim 2 , wherein the piece of graphene is a single layer or a multilayer including more than or equal to 2 layers and less than or equal to 100 layers. 
     
     
         8 . The positive electrode according to  claim 2 , wherein a weight ratio of the piece of graphene to the active material layer is less than 5.3 wt %. 
     
     
         9 . The positive electrode according to  claim 2 , wherein the piece of graphene covers surfaces of at least two of the first particles. 
     
     
         10 . The positive electrode according to  claim 2 , wherein the active material is selected from lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, and a complex of any of the lithium cobalt oxide, the lithium manganese oxide, and the lithium nickel oxide. 
     
     
         11 . A nonaqueous secondary battery comprising the positive electrode according to  claim 2 . 
     
     
         12 . An electrical device comprising the nonaqueous secondary battery according to  claim 11 ,
 wherein the electrical device is one of display devices, lighting devices, computers, word processors, image reproduction devices, music reproduction devices, radio receivers, recording reproduction devices, stereos, remote controls, clocks, cordless phone handsets, transceivers, mobilephones, earphones, game machines, pedometers, calculators, portable information terminals, e-book readers, electronic translators, audio input devices, cameras, toys, electric shavers, electric toothbrushes, high-frequency heating appliances, electric rice cookers, electric washing machines, electric vacuum cleaners, water heaters, electric fans, hair dryers, air-conditioning systems, dehumidifiers, and air conditioners, dishwashers, dish dryers, clothes dryers, futon dryers, electric refrigerators, freezers, flashlights, electric power tools, smoke detectors, a health equipment, a medical equipment, industrial equipment, and moving objects.   
     
     
         13 . An electrode material comprising:
 a plurality of particles of an active material having a layered rock salt structure; and   a piece of graphene,   wherein the plurality of particles has an average primary particle diameter of less than or equal to 3.0 μm.   
     
     
         14 . The electrode material according to  claim 13 , wherein the active material is selected from lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, and a complex of any of the lithium cobalt oxide, the lithium manganese oxide, and the lithium nickel oxide. 
     
     
         15 . The electrode material according to  claim 13 , wherein the active material comprises lithium, cobalt and oxygen. 
     
     
         16 . The electrode material according to  claim 13 , wherein the active material comprises lithium, nickel, cobalt, manganese and oxygen. 
     
     
         17 . The electrode material according to  claim 13 , wherein the piece of graphene is a single layer or a multilayer including more than or equal to 2 layers and less than or equal to 100 layers. 
     
     
         18 . The electrode material according to  claim 13 , wherein the piece of graphene covers surfaces of at least two of the plurality of particles. 
     
     
         19 . The electrode material according to  claim 13 , wherein the graphene comprises oxygen. 
     
     
         20 . The electrode material according to  claim 13 , wherein the average primary particle diameter of the plurality of particles is greater than or equal to 0.2 μm.