The invention discloses a nondestructive defect detection method of a
lithium ion battery. The nondestructive defect detection method comprises the following steps that: (1) a
signal transmitting end transmits ultrasonic signals to the
lithium ion battery to be detected, wherein the
signal intensity is I0; (2) the
signal receiving end receives ultrasonic signals in the ultrasonic signals, which pass through the
lithium ion battery to be detected, wherein the
signal intensity I1 of the ultrasonic
waves is a group of
signal intensity data corresponding to various scanning points of the
lithium ion battery to be detected; and (3) comparing the I1 with the I0 to generate a group of transmissivity t1 corresponding to various scanning points of the
lithium ion battery to be detected, and then outputting t1. The nondestructive defect detection method is used for carrying out nondestructive detection on the internal state of the
lithium ion battery by adopting the ultrasonic
waves, so that the waste on the time caused by repeated charging and discharging detection is avoided; and higher detection speed and precision can be acquired by using air as a
coupling medium and analyzing the transmissivity of different areas, and the position in which the defect is located can be accurately acquired, which cannot be achieved by repeated charging and discharging either.