Nonaqueous electrolyte secondary battery and battery module
According to the present disclosure, it is possible to appropriately prevent a shortage of a nonaqueous electrolyte solution in an electrode body and keep battery performance of a nonaqueous electrolyte secondary battery at a favorable state. A nonaqueous electrolyte secondary battery disclosed herein includes an electrode body and a nonaqueous electrolyte solution. 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. When a region of a negative-electrode composite material layer that is in contact with the electrolyte solution passage is referred to as a damming portion and a region that is located on the center side relative to the damming portion is referred to as a liquid retaining portion, the damming portion contains a negative electrode active material of which an electrical potential relative to a 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. With this configuration, the electrolyte solution passage can be closed by the damming portion in a charge state where the damming portion expands, and therefore leakage of the nonaqueous electrolyte solution can be suppressed.
1. 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.
2. The battery module according to claim 1 , wherein
the SOC measurement unit measures SOC of the power supply by integrating current values during charging and discharging of the power supply.
3. The battery module according to claim 1 , wherein
the degradation detection unit calculates an evaluation value D that is a numerical value expressing high-rate degradation of the power supply,
during a period for which an integrated value ΣD of the evaluation value D is smaller than a degradation determination reference value T D1 , the SOC adjustment unit adjusts SOC of the power supply so that the damming portion is thicker than the liquid retaining portion, and
when the integrated value ΣD of the evaluation value D exceeds the degradation determination reference value T D1 , the SOC adjustment unit reduces SOC of the power supply so that the damming portion becomes thinner than the liquid retaining portion.