Nonaqueous electrolyte secondary battery and battery module

A battery module comprising:

• a power supply configured to be electrically connected to an external device;
• and
• a control unit configured to control charging and discharging of the power supply, wherein
• the power supply includes a nonaqueous electrolyte secondary battery,
• the nonaqueous electrolyte secondary battery includes:
• an electrode body in which a positive electrode, a negative electrode, and a separator are overlaid on each other;
• and
• a nonaqueous electrolyte solution that infiltrates into the electrode body, wherein
• the positive electrode is formed by coating a surface of a band-shaped positive-electrode current collecting foil with a positive-electrode composite material layer that contains a positive electrode active material,
• the negative electrode is formed by coating a surface of a band-shaped negative-electrode current collecting foil with a negative-electrode composite material layer that contains a negative electrode active material,
• the electrode body includes an electrolyte solution passage that is a flow passage through which the nonaqueous electrolyte solution flows between the inside and the outside of the electrode body, and
• a region of the negative-electrode composite material layer that is in contact with the electrolyte solution passage is a damming portion, and a region of the negative electrode composite material layer that is located on a center side relative to the damming portion is a liquid retaining portion,
• the damming portion contains a negative electrode active material of which an electrical potential relative to the positive electrode active material is high and a ratio of expansion or contraction due to an increase or decrease in SOC is high, when compared to a negative electrode active material contained in the liquid retaining portion,
• the control unit includes:
• a degradation detection unit that detects high-rate degradation of the power supply;
• an SOC measurement unit that measures SOC of the power supply;
• and
• an SOC adjustment unit that adjusts the SOC by controlling charging and discharging of the power supply,
• during a period for which it is determined that the high-rate degradation is not occurring based on a result of detection performed by the degradation detection unit, the SOC adjustment unit maintains SOC of the power supply so that the damming portion is thicker than the liquid retaining portion, and
• upon determining that the high-rate degradation has occurred based on a result of detection performed by the degradation detection unit, the SOC adjustment unit reduces SOC of the power supply so that the damming portion becomes thinner than the liquid retaining portion.