Similarities in Lithium Growth at Vastly Different Rates

Lithium electrodeposition is important for lithium metal batteries and is presently a safety and reliability concern for the lithium-ion technology. In the literature, many models for the growth of dendrites can be found and a strong dependence on deposition rate is expected. To elucidate the process of the lithium deposition, operando light microscopy at the physical resolution limit of light was performed at rates varying by more than three orders of magnitude. The results show different growth regimes depending on the rate, and where needles, bushes, or accelerated bushes dominate the deposition. All these deposits are based on small crystalline needles and flakes. Little evidence for concentration gradient driven deposition was found. At the highest rate, the electrolyte ionically depletes, but the deposition continues by non-directional bush growth mainly from their insides. An important step at all rates is the insertion into defects in the crystalline lithium.