Method for manufacturing lithium ion secondary battery

Abstract

The method for manufacturing a lithium ion secondary battery includes a binder coating step ( 18 ), a mixture supplying step ( 20 ), a magnetic field applying step ( 22 ), and a convection generating step ( 24 ). The binder coating step ( 18 ) is a step of coating a slurry-form binder ( 18 a ) on a metal foil ( 12 a ) (collector). The mixture supplying step ( 20 ) is a step of supplying a negative electrode mixture containing graphite so as to be superposed on the slurry-form binder ( 18 a ) coated on the metal foil ( 12 a ) in the binder coating step ( 18 ). The magnetic field applying step ( 22 ) is a step of applying a magnetic field having magnetic lines of force pointing in the direction orthogonal to the metal foil ( 12 a ), to the negative electrode mixture ( 20 a ) coated on the metal foil ( 12 a ) in the mixture supplying step ( 20 ). Further, the convection generating step ( 24 ) is a step of generating convection in the negative electrode mixture ( 20 a ) by applying heat to the negative electrode mixture ( 20 a ) to which a magnetic field has been applied in the magnetic field applying step ( 22 ).

1 - 15 . (canceled) 
     
     
         16 . A lithium ion secondary battery, comprising:
 a collector; and   a negative electrode mixture layer adhering to the collector,   wherein the negative mixture layer contains graphite and a binding agent, and a weight ratio of the binding agent is smaller in a portion of the negative electrode mixture layer from a level at half a thickness of the negative electrode mixture layer to a surface of the negative electrode mixture layer than in a portion of the negative electrode mixture layer from a surface of the collector to the level at half the thickness of the negative electrode mixture layer, and   the graphite is oriented such that an interlayer plane of layers of hexagonal platelet-shaped crystal is orthogonal to the surface of the collector.   
     
     
         17 . The lithium ion secondary battery according to  claim 16 , wherein the graphite has a layered structure including hexagonal platelet-shaped crystals stacked one on another in such a manner as to form a plurality of layers. 
     
     
         18 . The lithium on secondary battery according to  claim 16 , wherein the graphite has a flat flake shape. 
     
     
         19 . The lithium ion secondary battery according to  claim 16 , wherein the binding agent is SBR.