The effects of adding potassium ion (K+) to lithium oxalyldifluroborate (LiODFB)/ethylene carbonate (EC)+dimethyl carbonate (DMC) (1:1 vol.%) electrolyte on the cycle behaviors of lithium deposition–stripping on a Li22Sn5 substrate electrode are investigated. The functions and mechanism of K+ addition to the electrolyte are evaluated through scanning electron microscopy (SEM), inductively coupled plasma-atomic emission spectrometry (ICP–AES), element mapping, energy dispersive spectrometer (EDS), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) analyses. The addition of K+ to the electrolyte significantly improves the morphology of the lithium deposits and the cycleability of lithium deposition–stripping. K+ is not reduced nor incorporated on the substrate during lithium deposition. Based on the reported “self-healing electrostatic shield” (SHES) mechanism, this study proposes the SHES–kinetics mechanism, which considers both kinetic and thermodynamic factors.