Nucleation processes at interfaces with both substrate and electrolyte control lithium growth.

Understanding the lithium nucleation and growth process is crucial for improving lithium metal battery performance. Here we investigate the roles of the lithium-electrolyte and lithium-substrate interfaces during the lithium nucleation process. Using a physics-based model, we identify which of the two interfaces controls lithium nucleation for different electrolytes and substrates. Sluggish lithium transport through the solid-electrolyte interphases (SEIs) and slow charge-transfer kinetics make the nucleation process SEI controlled and substrate independent, while substrate properties control lithium nucleation in a system having fast SEI transport and charge-transfer reactions. For substrate-controlled nucleation, we derive a model that elucidates the need for fast lithium adatom velocity along the substrate that outpaces the critical nuclei formation. We also reveal that lithium nucleation modes have a strong impact on lithium plating/stripping reversibility. Simultaneous fast transport through the SEIs and fast lithium adatom movement on the substrate are essential for achieving dense lithium deposition and long-cycle-life lithium metal batteries.