Unraveling the Rate-Dependent Stability of Metal Anodes and Its Implication in Designing Cycling Protocol

It is widely recognized that a high current rate (J) speeds up dendrite formation and thus shortens the cycle life of metal anodes. Here, an anomalous correlation is reported between elevated J and deposition/stripping stability (decrease-increase-decrease), leading to the relative maximum stability at a moderate J. Complementary theoretical and experimental analyses suggest that such a complex relationship lies in high J's dual and contradictory roles in kinetics and thermodynamics. The well-known former renders decreased Sand's time (tau) and deteriorative cyclic stability, while the commonly overlooked latter provides larger extra energy that accelerates nucleation rate (nu(n)). Using Zn metal anode as a model system, the nu(n) and tau controlled nucleation-growth process is unambiguously revealed, both of which are closely related to J. Based on these findings, an initial high J discharge strategy is developed to produce abundant nuclei for uniform metal growth at standard J in the subsequent process. The protocol increases the Zn deposition/stripping lifetime from 303 to 2500 h under a cycling capacity of 1 mAh cm(-2) without resorting to electrode/electrolyte modification. Furthermore, such a concept can be readily extended to Li/K metal anodes with significantly enhanced cycle life, demonstrating its universality for developing high-performance metal batteries.

Automated summary

A high current rate accelerates dendrite formation and reduces the cycle life of metal anodes, but a moderate current rate can actually increase deposition/stripping stability. This anomaly is due to the dual and contradictory roles of high current rates in kinetics and thermodynamics. By controlling the nucleation-growth process, the lifetime of metal deposition/stripping can be significantly increased.