Non-aqueous electrolyte secondary battery

A non-aqueous electrolyte secondary battery comprising:

• a positive electrode;
• a negative electrode;
• a separator;
• and
• an electrolyte solution, wherein
• at least part of the separator is interposed between the positive electrode and the negative electrode,
• the negative electrode includes a negative electrode substrate and a negative electrode active material layer,
• the negative electrode active material layer is placed on a surface of the negative electrode substrate,
• in a cross section parallel to the thickness direction of the negative electrode active material layer, the negative electrode active material layer is divided into two equal parts in the thickness direction, and thus the negative electrode active material layer is separated into a first region and a second region,
• the first region includes a surface of the negative electrode active material layer,
• the second region includes an interface between the negative electrode active material layer and the negative electrode substrate,
• the negative electrode active material layer includes a plurality of negative electrode active material particles,
• each of the negative electrode active material particles consists of a negative electrode active material,
• voids are formed in the first region of the negative electrode active material layer and in the second region of the negative electrode active material layer,
• an average circularity of the voids in the first region of the negative electrode active material layer is 0.26 or more, and an average circularity of the voids in the second region of the negative electrode active material layer is less than 0.26,
• each of the voids is surrounded by the plurality of negative electrode active material particles, and
• in a cross section parallel to a thickness direction of the negative electrode active material layer,
• the voids have:
• an average equivalent circle diameter from 9.6 μm to 35.8 μm;
• and
• an area percentage from 3.1% to 30.9%.