Battery Impedance Measurement by Laplace Transformation of Charge or Discharge Current/Voltage

Impedance spectroscopy of Z(ω) is often used in the electrochemical field to analyze electrode reactions and to calculate transient responses. Our previous study measured the overpotential resistance for our thermal behavior model to calculate the temperature rise of Nickel/metal-hydride battery or Lithium-ion battery during charge and discharge cycles. However, the Z(ω) measured by AC impedance meter did not agreed with the ones induced by charge/discharge characteristics. Therefore, we focus on the impedance measurement method by Takano et al, who obtained Z(ω) for Lithium-ion battery at wide frequency region by the Laplace transformation of both signals of the voltage-step input and its current response. We have extended this method to the Laplace transformation of current-step or current-pulse input signal and its voltage response signal to get Z(ω) for any charge/discharge current of Nickel/metal-hydride battery or Lithium-ion battery. We can get almost the same Z(ω) by the three different methods, and the measured Z(ω) does not depend on both charge/discharge current and the state of charge or the charge input. Moreover, Z(ω) including Warlbulg impedance at low frequencies gets near the overpotential resistance that can estimate well the battery temperature rise in our battery thermal behavior model.