On the Thermodynamic Origin of the Formation of Li-Dendrites in an Electrochemical Cell

Abstract

The direction of growth of neutral species in batteries and electrolyzers differs significantly. In a battery, dendrites can be formed during the charging process and are perpendicular to the interface between electrode and electrolyte. The aim of this manuscript is to address the origin of the growth orientation of the neutral metal and elucidate the factors that govern the dendrite growth by using the concept of chemical potential of neutral lithium and the electronic current in the electrolyte. With the consideration of the electronic conductivity in the ionic conductive phases, the chemical potential difference of lithium could be calculated across the cell, and predicts lithium deposition in the solid-electrolyte interphase (SEI) layer. The electronically conducting metal precipitate could work as a part of electrode and allow further growth along the current direction, resulting in the formation of dendrites. During growth, the ionic conductivity and the thickness distribution of the SEI layer determine the growth kinetics and the dendrite shape. A lower ionic conductivity and a nonuniform SEI layer lead to a sharp lithium dendrite. On the other hand, a low electronic conductivity and a high ionic conductivity of the electrode/electrolyte interface are in favor of suppressing the formation of a neutral species.