Suppression of Dendrite Formation via Pulse Charging in Rechargeable Lithium Metal Batteries

We introduce a coarse-grained simulation model for the reductive deposition of lithium cations in secondary lithium metal batteries. The model accounts for the heterogeneous and nonequilibrium nature of the electrodeposition dynamics, and it enables simulation of the long timescales and lengthscales associated with metal dendrite formation. We investigate the effects of applied overpotential and material properties on early-stage dendrite formation, as well as the molecular mechanisms that govern this process. The model confirms that dendrite formation propensity increases with the applied electrode overpotential, and it demonstrates that application of the electrode overpotential in time-dependent pulses leads to dramatic suppression of dendrite formation while reducing the accumulated electrode on-time by as much as 96%. Moreover, the model predicts that time dependence of the applied electrode overpotential can lead to positive, negative, or zero correlation between cation diffusivity in the solid-electrolyte interphase (SEI) and dendrite formation propensity. Analysis of the simulation trajectories reveals that dendrite formation emerges from a competition between the timescales for cation diffusion and reduction at the anode/SEI interface, with lower applied overpotentials and shorter electrode pulse durations shifting this competition in favor of lower dendrite formation propensity. This work provides a molecular basis for understanding and designing pulsing waveforms that mitigate dendrite formation while minimally affecting battery charging times.