Secondary battery and method for manufacturing same

Abstract

An object of the present invention is to provide a high-quality secondary battery having high electric characteristics and high reliability, the secondary battery preventing a shortcut between a positive electrode and a negative electrode by means of an insulating material and preventing or reducing an increase in volume and deformation of a battery electrode assembly, and a method for manufacturing the same. Secondary battery 100 according to the present invention includes a battery electrode assembly including positive electrode 1 and negative electrode 6 alternately stacked via separator 20. Positive electrode 1 and negative electrode 2 each includes current collector 3 or 8 and active material 2 or 7 applied to current collector 3 or 8. Active material 2A positioned on one surface of positive electrode 1 of current collector 3 includes flat portion 2A1 and small-thickness portion (thin-layer portion) 2A3 positioned on the end portion side relative to flat portion 2A1, the small-thickness portion 2A3 having a thickness that is smaller than that of flat portion 2A1. A portion of active material 2B positioned on another surface of current collector 3 of positive electrode 1, the portion facing thin-layer portion 2A3 of active material 2A positioned on the one surface via current collector 3 is a flat portion having a constant thickness.

1 . A secondary battery manufacturing method comprising:
 forming a positive electrode by applying a positive-electrode active material to each of opposite surfaces of a positive-electrode current collector;   forming a negative electrode by applying a negative-electrode active material to each of opposite surfaces of a negative-electrode current collector; and   alternately stacking the positive electrode and the negative electrode via a separator, wherein   the forming of the positive electrode includes applying a positive-electrode active material layer to a surface of the positive-electrode current collector to form a positive-electrode active material layer consisting essentially of a flat portion, and then   applying a positive-electrode active material layer to a surface on an opposite side of the surface with the positive-electrode active material consisting essentially of a flat portion formed thereon to form a positive-electrode active material layer including a large-thickness portion and a small-thickness portion having a thickness that is smaller than that of the large-thickness portion.   
     
     
         2 . The secondary battery manufacturing method according to  claim 1 ,
 further comprising disposing an insulating material to cover a boundary portion between a coated portion to which the positive-electrode active material has been applied and a non-coated portion to which the positive-electrode active material has not been applied in the positive electrode.