where t is the thickness of the PAM hydrogel electrolyte, is the resistivity of the PAM 𝑅 𝑠 hydrogel electrolyte, and A is the contact area of the coin cell spacer and the PAM hydrogel electrolyte. The resistivity is obtained from the x-axis intersection in the potential electrochemical impedance spectroscopy (PEIS) with perturbation of 10 mV and frequency from 1 Hz to 1 MHz. The measured thickness of the PAM hydrogel electrolyte was 0.18 cm, the contact area was 1.603 cm 2 , and the resistivity was 2.642 , so the ionic conductivity of Ω PAM/LiCl hydrogel electrolyte obtained is: