We first studied the EIS spectrum from a battery with a composite polymer electrolyte, a Li-metal anode, and a LiFePO 4 cathode . The EIS frequencies were taken between 1 Hz and 7 MHz with five points per decade, and the ECM parameters are presented in Table . Each row of Figure show the impedance (left panel) and DRT (right panel) recovered using the optimal and hyper-opt, GCV and hyper-GCV, and mGCV and hyper-GCV methods. We observed that the hyper-𝜆 approaches recovered the DRT more accurately compared to the corresponding parameter regularization method (panels (b), (d), and (f) of Figure and Table