Lithium ion batteries have the issue of internal short circuiting by the electrodeposition of metal at the negative electrode. This deposition follows the dissolution of contaminated metal particles incorporated into the positive electrode in manufacturing process. Thus, we have investigated the dissolution­/deposition behavior of metals such as copper, nickel, iron, and stainless steel so far1. We also proposed a diagnosis method for the incorporation of the metal particles by electrochemical impedance spectroscopy, taking advantage of characteristic changes of the impedance spectra (phase angle) between 10-­1 Hz1. In the present study, we investigate the time variation of the impedance spectra associated with the growth of the metal deposits at the negative electrode. Test cells were assembled with positive electrodes of metal plates of iron, nickel and stainless steel, electrolyte solution of ethylene carbonate (EC)/diethylcarbonate (DEC) (1:1 vol.) containing 1 M LiPF6, and negative electrodes of graphite mixed with PVDF binder. Potential between the metal plates and the negative electrode was maintained at 4.2 V by a potentio/galvanostat to electrochemically dissolve the metal plate at the positive electrode and deposit the metals at the negative electrode, while the negative electrode was maintained at 0.3 V against a lithium wire in the test cell by an auxiliary potentio/galvanostat to reproduce the potentials in a lithium ion battery. We observe the metal deposits at the negative electrodes from the iron, nickel and stainless steel plates by FE-SEM and EDX. Time variations of the phase angle in the impedance spectra between 10­-1 Hz for the above metal deposits are correlated with the metal growth, taking into account the impedance of the SEI layer at the metal surface. 1. Hironori Nakajima, and Tatsumi Kitahara, Diagnosis Method to Detect the Incorporation of Metallic Particles in a Lithium Ion Battery, ECS Trans., Vol. 68, 2, 59-74 (2015).