Secondary battery and life prediction apparatus thereof

1. A life prediction apparatus of a secondary battery that includes an electrode assembly, a positive electrode tab, a negative electrode tab, a case and a plurality of reference electrodes, the life prediction apparatus comprising:

an electrode selector including at least one switch;

a control unit configured to transmit an electrode selection signal designating at least two of the plurality of reference electrodes to the electrode selector;

the electrode selector configured to select each of the designated reference electrodes at least once at every predetermined cycle using the at least one switch, in response to the electrode selection signal; and

an impedance measurer configured to:

form a current path electrically connecting a reference tab, which is any one of the positive electrode tab and the negative electrode tab, to the selected reference electrode, and

measure an impedance associated with the selected reference electrode, based on an AC voltage between the reference tab and the selected reference electrode by applying an AC current of a predetermined frequency band to the reference tab, in a state where any one of the plurality of reference electrodes is selected by the electrode selector;

wherein the plurality of reference electrodes include:

a first reference electrode having one end disposed in the case and connected to a first reference location of the separator and the other end protruding out of the case; and

a second reference electrode having one end disposed in the case and connected to a second reference location of the separator, which is different from the first reference location, and the other end protruding out of the case,

wherein the impedance measurer is configured to:

measure a first impedance associated with the first reference electrode when the first reference electrode is selected by the electrode selector, and

measure a second impedance associated with the second reference electrode when the second reference electrode is selected by the electrode selector, and

wherein the control unit is further configured to, when the impedance of each of the designated reference electrodes is completely measured by the impedance measurer, predict a residual life of the secondary battery based on a ratio of the first impedance to the second impedance, wherein the ratio indicates a degree of irregular degradation between different regions of the secondary battery.

2. The life prediction apparatus of a secondary battery according to claim 1 , wherein a distance from a first connection location where the positive electrode tab contacts the positive electrode plate to the first reference location is shorter than a distance from the first connection location to the second reference location.

3. The life prediction apparatus of a secondary battery according to claim 2 , wherein the plurality of reference electrodes further include:

a third reference electrode having one end disposed in the case and connected to a third reference location of the separator and the other end protruding out of the case,

wherein a distance from the first connection location to the third reference location is longer than a distance from the first connection location to the first reference location and shorter than a distance from the first connection location to the second reference location, and

wherein the control unit is further configured to transmit an electrode selection signal designating a selection of the third reference electrode to the electrode selector when the ratio of the first impedance to the second impedance is equal to or greater than a reference value.

4. A battery pack, comprising a life prediction apparatus defined in claim 1 .