Secondary battery

A secondary battery comprising:

• a battery body having a plurality of stacked power generation elements;
• and
• a restraint restraining the battery body in a stacking direction of the power generation elements;
• the power generation elements having a positive electrode having a positive electrode collector in which a positive electrode active material layer is disposed, an electrolyte layer containing an electrolyte, and a negative electrode having a negative electrode collector which includes a negative electrode active material layer containing silicon;
• the positive electrode active material layer and the negative electrode active material layer facing each other, and being interposed by the electrolyte layer;
• the restraint having a first contact section and a second contact section that contact a surface of one of outermost layers of the battery body in the stacking direction and that apply a restraining force;
• the negative electrode being positioned in one the outermost layer, and a surface of the negative electrode having a contact region in contact with the first contact section and a non-contact region which is not in contact with the first contact section;
• the first contact section being configured so that a stress occurring at a boundary of the contact region and the non-contact region is less than a breaking strength of the negative electrode collector;
• and
• the stress being based on the restraining force of the first contact section, and expansion and contraction of the negative electrode due to a change in volume of the negative electrode active material layer caused by charging and discharging.