Unipolar Excitation Signal with Two Phases for Impedance Spectroscopy of Li-ion battery cells

Impedance spectroscopy is essential for diagnosing electrochemical systems such as Li-ion batteries, often requiring sinking-sourcing hardware. However, such hardware often generates high power consumption and heat loss, posing safety problems. Moreover, applying impedance spectroscopy to split hardware, i.e., sinking (discharging) and source (charging) dedicated hardware, results in less heat generation but an unstable measurement. This paper defines a binary excitation sequence and double phase impedance measurement that allow the measurement of a Li-ion battery's stable zero-charge impedance spectrum based on a split-hardware. The zero-charge stable impedance measurements can be extracted by designing an excitation binary signal with a slight bias current that allows impedance spectroscopy during charge and discharge, which is then averaged. The conditions for the signal design are detailed in this paper. Furthermore, the proposed method has been applied to a Li-ion battery cell and has returned a maximum impedance measurement deviation of ± 0.3% ∠± 12%.