| Popis: |
Aluminum is an attractive candidate for replacing graphite anodes in lithium-ion batteries because it has high specific capacity (990 mAh g-1), and directly using aluminum foil as the anode structure eliminates the need for slurry-coating processes. However, achieving highly reversible lithiation and delithiation of aluminum is challenging due to volume changes during transformation, sluggish lithium-ion transport through the surface oxide layer, and poor initial Coulombic efficiency which all lead to degradation during cycling. Previous studies have focused on understanding the fundamental electrochemical reaction and material transformation behaviors of aluminum, yet there has not been a focus on how different aluminum alloy compositions behave and degrade under electrochemical cycling conditions. In this work, we carry out comprehensive electrochemical testing to benchmark the performance of three different aluminum alloy foils under different cycling conditions. We found that for foils of constant thickness, all foil compositions exhibit a power-law dependence of cycle life on the areal capacity lithiated per cycle, revealing that degradation is significantly accelerated when high areal capacities are used each cycle. Furthermore, the composition of the aluminum alloy was found to strongly affect the Coulombic efficiency over the first 10 cycles, with higher purity foils exhibiting higher Coulombic efficiency. Finally, ex situ scanning electron microscopy and operando optical microscopy revealed different reaction mechanisms and mechanical degradation behavior amongst the different alloys. Based on understanding these various parameters, we showed how full cells with aluminum anodes can be cycled for hundreds of cycles at relatively low areal capacities. The improved understanding of the behavior of aluminum foil anodes herein paves the way for future work intended to engineer aluminum-based foils with enhanced stability. |
