Mechano-electrochemical modeling of lithium dendrite penetration in a solid-state electrolyte: Mechanism and suppression

The mechanism of lithium dendrite penetration in solid-state electrolyte (SE) and its suppression strategies are studied based on a new phase field (PF) model involving fracture mechanics, electrodeposition processes, and mechano-electrochemical coupling (MEC) effects. Numerical results reveal the high stress-intensity factor is caused by high hydrostatic pressure in lithium, and the high stiffness of SE does not inhibit dendrite penetration. It is because the increase in Young's module of SE, E_SE, makes the stress-intensity factor even more significant. That is why a stiff SE is “pierced” by the much softer lithium dendrites. Considering MEC, the increase in E_SE has a competing effect on dendrite penetration causing a nonmonotonic change in dendrite length, which provides a window to mitigate dendrite penetration. Dendrite suppression by toughening SE is quantitatively evaluated. A critical fracture surface energy density of SE (γ = 3.5 J m⁻²) is determined. When γ > 3.5 J m⁻², facture toughness becomes larger than stress-intensity factor and dendrite penetration is suppressed with E_SE. However, toughening is difficult. Engineering compressive traction, F_a, in SE surfaces is a more realistic strategy, that cause a significantly inhibition in dendrite penetration with F_a from 0 to 100 MPa.