Low-Temperature-Induced Interfacial Transformation of the Aluminum Anode in Alkaline Electrolyte

The severe polarization of aluminum (Al) anodes in alkaline electrolytes at low temperatures remains a critical barrier to the commercialization of aqueous Al batteries, yet the interfacial origin of this impedance surge is not fully understood. Herein, we employ in situ dynamic electrochemical impedance spectroscopy (EIS) coupled with distribution of relaxation times (DRT) analysis to identify a characteristic inflection point in the behavior of a pure Al anode in 4 m NaOH within the 5°C-0°C range. Below this threshold, a new relaxation process emerges at short time constants in the DRT spectrum, and its polarization contribution intensifies significantly with further cooling. We attribute this process to the low-temperature-induced formation of an interfacial highly disordered Al₂O₃-rich layer, as confirmed by spectroscopic and computational analyses. We therefore propose an 'impedance induced by interfacial restructuring at low temperatures' model, wherein performance degradation arises primarily from interfacial structural and compositional evolution rather than from the conventionally assumed decrease in electrolyte conductivity. These findings provide a mechanistic basis for engineering low-temperature-adaptable Al anodes via interfacial design.