Morphological stability of electrodeposition through a viscoelastic coating*

Lithium metal anodes, the key component of several emerging lightweight, energy-dense battery chemistries, continue to suffer from serious safety and cycle life concerns due to dendritic lithium growths. A promising approach toward dendrite suppression is to insert a viscoelastic polymeric interphase between the anode and the separator. Good coating layers have been empirically found to exhibit instantaneous elastic response and adaptability to volume change, but no mechanistic understanding was established. We develop a continuum model to study the effects of a polymer coating on the morphological dendritic instability by explicitly incorporating the viscoelastic response and the dielectric permittivity of the polymer. The effects of charging current density and overpotential during cycling are explored, and the coating properties and battery operation conditions for stable, uniform lithium growth and long cycle life are discussed.