We first computed the 𝑅 p of a rechargeable Li-metal battery with a LiFePO 4 cathode and a composite polymer electrolyte . The potentiometric EIS data was obtained in the frequency range from 1 Hz to 0.9 MHz using a voltage amplitude of 10 mV. In addition to the GP analysis illustrated in Section 3.1, we regressed the EIS spectrum with an ECM consisting of three ZARCs whose parameters values are given in Table .