Effect of Chemical Segregation and Surface Defect Formation on the Mechanism of the Aluminum Dendrite Growth.

Rechargeable aluminum batteries (RABs) are one of the most promising beyond lithium-ion battery chemistries. However, nonuniform dendrite growth during the cycling process remains an obstacle for practical application. In this work, we investigated different stages of the Al dendrite growth mechanism in an Al rechargeable battery system. The first stage of Al dendrite growth is a tip growing stage, where the chemical segregation behavior occurs at the center of the dendrite, with further strain concentration identified inside the chemically inhomogeneous regions; these chemical and strain inhomogeneities are attributed to the metal-corrosive electrolyte interaction. Furthermore, in the large dendrite growth stage, chemical segregation is not pronounced, while surface defect structures such as coherent and incoherent twin boundaries start to appear; these boundaries are connected through multiple stacking faults and migrate along the dendrite growing surface, which is believed to be one of the growth mechanisms for the large dendrite surface. This investigation provides an in-depth analysis of the microstructure evolution and changes occurring in Al dendrites during electrochemical disposition. This perspective creates opportunities for a more-tailed approach in designing future electrolytes and modifying anode surface to promote uniform ion deposition and lessen the safety concerns of Al dendrites in Al rechargeable batteries.