Dynamic Locking of Interfacial Side Reaction Sites Promotes Aluminum-Air Batteries Close to Theoretical Capacity

Aluminum metal has been regarded as a promising anode material for aqueous metal-air batteries. However, the stable cycling of Al anodes is challenging due to the severe parasitic corrosion of Al metal in alkaline electrolytes. Here, a novel additive, n-octylphosphonic acid (OPA), is introduced into the typical NaOH electrolyte system to improve the interfacial stability of Al anodes and thus promote high-performance Al-air batteries (AABs). Combining several experimental characterizations and theoretical calculation, it is proved that OPA molecules in an NaOH aqueous environment can modify the Al anode/electrolyte interface and alter the stacking of the discharge product. The electrolyte engineering is capable of anchoring dynamically to restrain side reactions through hydrogen bonds (H center dot center dot center dot O), homogenizing the dissolution of Al metal and avoiding precipitation agglomeration. As a proof of concept, AABs full cells with an electrolyte containing OPA achieve higher potential plateau and discharge capacity than those with a pure NaOH electrolyte. It paves a way to develop highly-efficient and eco-friendly electrolyte additive strategies for high-performance AABs devices arid advance the current understanding of organic additive mechanisms in AABs.

Automated summary

A novel additive, n-octylphosphonic acid (OPA), is introduced to improve the performance of aluminum-air batteries by modifying the aluminum anode/electrolyte interface and stabilizing the discharge product. Experimental and theoretical evidence shows that OPA can restrain side reactions, homogenize aluminum dissolution, and enhance the overall performance of the batteries.