Electrochemical device

A electrochemical device, comprising:

• a negative electrode having a negative-electrode collector being a metal foil, and a negative-electrode active material layer formed on a principal face of the negative-electrode collector;
• a positive electrode having a positive-electrode collector being a metal foil, and a positive-electrode active material layer formed on a principal face of the positive-electrode collector;
• a negative-electrode terminal made of metal, and having a joining part which is a part joined to the principal face of the negative-electrode collector;
• a protective tape made of insulating material and attached to the negative electrode to cover the joining part;
• separators insulating the positive electrode and negative electrode;
• and
• electrolytic solution immersing the positive electrode, negative electrode, and separators;
• where the positive electrode, negative electrode, and separators are stacked and wound together in such a way that the separators separate the positive electrode and negative electrode;
• wherein,
• the negative electrode has a first width along a direction parallel with the axis of winding;
• the positive electrode has a second width, which is smaller than the first width, along the direction parallel with the axis of winding;
• and
• a length of the protective tape along the direction parallel with the axis of winding is equal to or greater than the second width.