Electrode group, battery, and battery pack

An electrode group comprising:

• a positive electrode including a positive electrode active material-containing layer;
• and
• a negative electrode including a negative electrode active material-containing layer containing at least one titanium-containing composite oxide selected from the group consisting of a monoclinic niobium titanium composite oxide and an orthorhombic titanium-containing composite oxide, wherein
• at least a part of the negative electrode active material-containing layer faces at least a part of the positive electrode active material-containing layer, and
• the electrode group satisfies the following formula:
• 6500≤A/B≤18500,
• where A is an area [cm2] of a portion of the negative electrode active material-containing layer that faces the positive electrode active material-containing layer, and B is a thickness [cm] of the electrode group.