Method for manufacturing secondary battery and secondary battery

A method for manufacturing a secondary battery including an electrode group in which a positive electrode and a negative electrode are arranged with a porous insulating layer interposed therebetween, the method comprising:

• (a) preparing the electrode group in which the positive electrode and the negative electrode are arranged with the porous insulator interposed therebetween, with an end of at least one of the positive electrode and the negative electrode protruding from the porous insulating layer;
• (b) preparing a current collector on a first principal surface of which a plurality of protrusions having vertexes are formed;
• (c) bringing the end of the at least one of the positive electrode and the negative electrode protruding from the porous insulating layer into contact with a second principal surface of the current collector;
• and
• (d) generating an electric arc toward the vertexes of the protrusions to melt the protrusions, thereby welding the end of the at least one of the positive electrode and the negative electrode to the current collector by a molten material of the protrusions.