K+ Reduces Lithium Dendrite Growth by Forming a Thin, Less-Resistive Solid Electrolyte Interphase

Adding 10 mM KPF6 to the 1 M LiPF6 in ethylene carbonate/dimethyl carbonate electrolyte of symmetrical Li | Li cells eliminated the growth of dendrites at 0.5 mA cm–2 current density and massively reduced, but did not eliminate, the growth of dendrites at 2.5 mA cm–2. The added KPF6 increased the fraction of inorganic salts in the solid electrolyte interface, making it thinner and more Li+ conductive. It overcame the growth of dendrites resulting from inadequate nucleation density but not dendrite growth into the depletion layer, which scales with the layer’s thickness, i.e., the current density.