with Rlive1 and Rlive2 represenFng the transport of acFve (Li ion) and non-acFve ions, respecFvely, inside the pores of live Li dendrites (i.e. dendrites that sFll contain electronically connected metallic lithium). RSEI denotes the transport resistance through the thin SEI film covering the live dendrites . CPE1 can be considered as an approximaFon of the capaciFve properFes of the interface between electrolyte and live dendrites. The physical meaning of R3 can be roughly described with the following equaFon: To find an appropriate combinaFon of input parameters to further boost the Coulombic efficiency arer formaFon, XGBoost regression was used, considering the charge and discharge rate and the on-and off-Fme as input features and the Coulombic efficiency as output parameter. For this purpose, 47 coin cells were formed by pulsed charging and discharging at charging rates ranging from 1C to C/8, discharging rates ranging from 1C to C/16, on-Fmes ranging from 0.25 s to 4 s, and off-Fme ranging from 0.75 s to 8 s with test-train split 80-20. The low R 2 score of 0.45 (<0.5) means that the fit is weak and that the model should not be used for predicFons. The reason for this result is poor reproducibility of the output parameter if charge and discharge rate and on-Fme and off-Fme are used as input features. Namely, it has been observed experimentally that different pulsed protocols oren produce the same or very similar Coulombic efficiencies, although on average certain pulsed protocols produce an improvement. In an aaempt to find input parameters that could beaer explain the process and could therefore be used to predict Coulombic efficiency, the voltage curve was taken into consideraFon. More specifically, the voltage value at the end of current on-Fme and voltage value at the end of current off-Fme that encompasses the IR-drop and off-Fme, which we refer to as the pseudo-voltage(IR)-drop (Fig. . a). The reason for choosing these parFcular points is to find a suitable off-Fme so not to keep the charging for too long to further reduce the Fme necessary for formaFon, but to keep it long enough for the replenishment of metal ions to occur to in order to boost Coulombic efficiency. MulFple values of pseudo-IR-drop were taken as input parameters along charge and discharge curves, mainly at the points on the curves where the values change the most. In this case, the XGBoost regression model resulted in R 2 value of 0.82 (Fig 6 . b), indicaFng that the fit is strong (R 2 >0.7) and that the model predicts the dependent variable well, demonstraFng the potenFal applicability of pseudo-IR-drop as a control parameter to achieve the desired Coulombic efficiency. It is likely that the high IR-drop corresponds to the formaFon of a rough metallic Li surface, since rough films possess higher resistances than smooth films, and could potenFally be used to apply a reverse pulse to discharge dendrites. In this way, we hope that the pseudo-IR-drop could serve as a feedback loop to adjust the pulse magnitude/duraFon during charging to enable beaer control over Li electroplaFng and obtain smooth films. In this way, each cell could be treated individually with an appropriate procedure to boost capacity retenFon and reproducibility.