Secondary battery and electrode member thereof capable of being decreased bending deformation after rolling

A secondary battery, comprising an electrode assembly, the electrode assembly comprising an electrode member;

• the electrode member comprising an insulating substrate, a conducting layer and an active material layer;
• the electrode member having a symmetric structure with the insulating substrate at a center of the symmetric structure;
• the conducting layer being provided on a surface of the insulating substrate, and the conducting layer comprising a main portion and a protruding portion extending from the main portion, the main portion being coated with the active material layer, the protruding portion being not coated with the active material layer;
• and
• the active material layer being composed of a first portion and a second portion, each of the first portion and the second portion having a constant thickness, the first portion being positioned at an end of the active material layer away from the protruding portion, the second portion being positioned at a side of the first portion close to the protruding portion and connected with the first portion, and a thickness of the first portion being less than a thickness of the second portion.