Judgment method for the reason of lithium battery performance degradation

The invention provides a judgment method for the reason of lithium battery performance degradation, and relates to judgment of battery electrical performance. The steps are that a charge deltav-t curve of a lithium battery is acquired and a discharge deltav-t curve of the lithium battery is acquired; the value of area s included between the charge and discharge deltav-t curves is calculated; and the area s is calculated by using the form of voltage difference and time integration so that the coefficient ki acting as the degree of battery performance degradation is obtained. The reason of lithium battery performance degradation is judged through comparison of the charge deltav-t curves and the discharge deltav-t curves respectively corresponding to different cyclic number of times of charge and discharge of the lithium battery so that the defects in the prior art that the reason of lithium battery performance degradation cannot be judged in the daily use process of the lithium battery can be overcome.