Unraveling the rate-dependent stability of metal anodes and its implication in designing cycling protocol

Abstract

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 (τ) and deteriorative cyclic stability, while the commonly overlooked latter provides larger extra energy that accelerates nucleation rate (νn). Using Zn metal anode as a model system, the νn and τ 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.