Performance deterioration detecting apparatus and performance deterioration detecting method for energy storage device, and energy storage system

1. A performance deterioration detecting apparatus configured to detect a performance deterioration start state of an energy storage device, wherein the performance deterioration start state is an initial state of deterioration in performance of the energy storage device, the apparatus comprising:

a first acquiring unit configured to acquire a first maximum variation amount regarding a capacity-voltage property of the energy storage device, the first maximum variation amount is a maximum value of a capacity variation amount at a first time point;

a second acquiring unit configured to acquire a second maximum variation amount regarding the capacity-voltage property, the second maximum variation amount is a maximum value of the capacity variation amount at a second time point; and

a performance deterioration determiner configured to determine at the second time point that the energy storage device is in the performance deterioration start state, the second time point occurs after the first time point,

wherein the energy storage device is in the performance deterioration start state if a variation amount ratio exceeds a predetermined value, the variation amount ratio is a ratio of the second maximum variation amount to the first maximum variation amount, and

wherein a relation between the capacity variation amount and a voltage of the energy storage device is the capacity-voltage property, a degree of variation in a current carrying capacity of the energy storage device relative to a variation in voltage of the energy storage device is the capacity variation amount.

2. The performance deterioration detecting apparatus according to claim 1 , wherein

the performance deterioration determiner is configured to determine that the energy storage device is in the performance deterioration start state by determining at the second time point that the energy storage device is in an initial state of sudden deterioration in chargeable or dischargeable capacity of the energy storage device or in an initial state of sudden deterioration in input-output performance indicated by an input-output property of the energy storage device if the variation amount ratio exceeds the predetermined value.

3. The performance deterioration detecting apparatus according to claim 1 , wherein

the performance deterioration determiner is configured to determine that the energy storage device is in the performance deterioration start state at the second time point if the variation amount ratio exceeds the predetermined value set to a range from 0.7 to 0.8.

4. The performance deterioration detecting apparatus according to claim 1 , wherein

the first acquiring unit is configured to acquire the first maximum variation amount when the energy storage device is in the initial state.

5. The performance deterioration detecting apparatus according to claim 1 , wherein the second acquiring unit is configured to:

charge or discharge the energy storage device at the second time point to acquire a relation between the voltage and the current carrying capacity of the energy storage device,

calculate the capacity variation amount by differentiating the current carrying capacity with respect to the voltage in accordance with the relation between the voltage and the current carrying capacity of the energy storage device, and

acquire the capacity-voltage property indicating the relation between the capacity variation amount and the voltage to acquire the second maximum variation amount.

6. The performance deterioration detecting apparatus according to claim 1 , wherein

the performance deterioration determiner is configured to limit an upper limit charging voltage of the energy storage device if the performance deterioration determiner determines that the energy storage device is in the performance deterioration start state at the second time point.

7. The performance deterioration detecting apparatus according to claim 1 , wherein

the performance deterioration determiner is configured to limit a maximum flowing current to the energy storage device if the performance deterioration determiner determines that the energy storage device is in the performance deterioration start state at the second time point.

8. The performance deterioration detecting apparatus according to claim 1 , wherein

the energy storage device is a lithium-ion secondary battery that includes layered lithium transition metal oxide as a positive active material,

the first acquiring unit is configured to acquire the first maximum variation amount of the lithium-ion secondary battery, and

the second acquiring unit is configured to acquire the second maximum variation amount of the lithium-ion secondary battery.

9. An energy storage system comprising:

the performance deterioration detecting apparatus according to claim 1 ; and

the energy storage device.

10. A performance deterioration detecting method of detecting a performance deterioration start state of an energy storage device, wherein the performance deterioration start state is an initial state of deterioration in performance of the energy storage device, the method comprising:

electronically acquiring, by a first acquiring unit, a first maximum variation amount regarding a capacity-voltage property of the energy storage device, the first maximum variation amount is a maximum value of a capacity variation amount at a first time point;

electronically acquiring, by a second acquiring unit, a second maximum variation amount regarding the capacity-voltage property of the energy storage device, the second maximum variation amount is a maximum value of the capacity variation amount at a time point later than the first time point; and

electronically determining, by a performance deterioration determiner, whether or not a ratio of the second maximum variation amount to the first maximum variation amount exceeds a predetermined value, the energy storage device is in the performance deterioration start state if the ratio exceeds the predetermined value,

wherein a relation between the capacity variation amount and a voltage of the energy storage device is the capacity-voltage property, a degree of variation in a current carrying capacity of the energy storage device relative to a variation in voltage of the energy storage device is the capacity variation amount.

11. An integrated circuit configured to detect a performance deterioration start state of an energy storage device, wherein the performance deterioration start state is an initial state of deterioration in performance of the energy storage device, the integrated circuit comprising:

a first acquiring unit configured to acquire a first maximum variation amount regarding a capacity-voltage property of the energy storage device, the first maximum variation amount is a maximum value of a capacity variation amount at a first time point;

a second acquiring unit configured to acquire a second maximum variation amount regarding the capacity-voltage property, the second maximum variation amount is a maximum value of the capacity variation amount at a second time point; and

a performance deterioration determiner configured to determine at the second time point that the energy storage device is in the performance deterioration start state, the second time point occurs after the first time point,

wherein the energy storage device is in the performance deterioration start state if a variation amount ratio exceeds a predetermined value, the variation amount ratio is a ratio of the second maximum variation amount to the first maximum variation amount, and

wherein a relation between the capacity variation amount and a voltage of the energy storage device is the capacity-voltage property, a degree of variation in a current carrying capacity of the energy storage device relative to a variation in voltage of the energy storage device is the capacity variation amount.