Battery system and capacity recovery method for lithium ion secondary battery
An ECU controls a PCU to perform capacity recovery control of recovering a capacity of an assembled battery. The capacity recovery control includes a discharge mode and a capacity recovery mode. In the discharge mode, the ECU discharges the assembled battery to a predetermined overdischarge region. In the capacity recovery mode, the ECU repeatedly performs, in the overdischarge region, a voltage increase of increasing a voltage across a lithium ion secondary battery due to a stop of the discharging and a pulse discharge of discharging the lithium ion secondary battery while oscillating a discharge current.
1. A battery system comprising:
a lithium ion secondary battery including a positive-electrode active material layer and a negative-electrode active material layer disposed with a separator therebetween;
a charging and discharging device configured to charge and discharge the lithium ion secondary battery; and
a controller configured to control the charging and discharging device to perform capacity recovery control of recovering a capacity of the lithium ion secondary battery,
the negative-electrode active material layer including
a facing portion that faces the positive-electrode active material layer, and
a non-facing portion that does not face the positive-electrode active material layer,
the capacity recovery control including
first control of discharging the lithium ion secondary battery to a predetermined overdischarge region, and
second control of repeatedly performing, in the predetermined overdischarge region,
a voltage increase of increasing a voltage across the lithium ion secondary battery due to a stop of the discharging, and
a pulse discharge of discharging the lithium ion secondary battery while oscillating a discharge current.
2. The battery system according to claim 1 , wherein the second control is performed in a range in which the voltage across the lithium ion secondary battery does not fall below a predetermined lower-limit voltage.
3. The battery system according to claim 1 , wherein an oscillation frequency of the discharging current in the pulse discharge is 3 kHz to 20 kHz.
4. The battery system according to claim 1 , wherein the capacity recovery control is performed under a condition that a temperature of the lithium ion secondary battery is 40° C. to 80° C.
5. The battery system according to claim 1 , wherein the predetermined overdischarge region is a region in which a state of charge (SOC) of the lithium ion secondary battery is 0% or less.
6. A capacity recovery method for a lithium ion secondary battery,
the lithium ion secondary battery including a positive-electrode active material layer and a negative-electrode active material layer disposed with a separator therebetween,
the negative-electrode active material layer including
a facing portion that faces the positive-electrode active material layer, and
a non-facing portion that does not face the positive-electrode active material layer,
the capacity recovery method comprising:
discharging the lithium ion secondary battery to a predetermined overdischarge region; and
repeatedly performing, in the predetermined overdischarge region,
a voltage increase of increasing a voltage across the lithium ion secondary battery due to a stop of the discharging, and
a pulse discharge of discharging the lithium ion secondary battery while oscillating a discharge current.