Battery system and method for evaluating lithium-ion battery degradation

Abstract

ECU evaluates high-rate degradation of a lithium-ion battery, using a score and an in-plane score. The score is an index for evaluating unevenness in salt concentration of an electrode body in a lamination direction of the electrode body. The in-plane score is an index for evaluating unevenness in salt concentration of the electrode body in an in-plane direction of the electrode body. For each computing cycle, ECU calculates a current score, and calculates a current in-plane score based on an SOC (State Of Charge) of the lithium-ion battery. When the absolute value of an in-plane integrated score is beyond a reference value, ECU evaluates the high-rate degradation based on the current score, the current in-plane score, and a degradation score which is obtained by integrating previous scores beyond a deadband. When the absolute value is below the reference value, ECU evaluates the high-rate degradation, based on the degradation score.