Novel lean Mg-Ag anodes designed through surface voltage potential difference for high-performance Mg-air battery

Abstract

The primary limitations hindering the broad adoption of primary magnesium (Mg)-air battery are their low cell voltage and energy conversion rates. To overcome these challenges, we develop hetero-structured magnesium-silver (Mg-Ag) anodes with varying silver content. Our findings show that Mg-2Ag and Mg-0.25Ag anodes demonstrate a characteristic bimodal grain structure. Additionally, the distribution of local strain is heavily influenced by the arrangement of grain boundaries, leading to varying surface voltage potential differences. The uniform and extensive local strain distribution in Mg-0.25Ag anode facilitates discharge activity and suppresses occurrence of the chunk effects. Moreover, compact discharge film with a higher fraction of Ag₂O restrains wastage of Mg-0.25Ag anode. A Mg-air battery model utilizing this anode exhibits a remarkable synergy between cell voltage (1.449 V) and energy density (1631.194 mW h g⁻¹) at a current density of 5 mA cm⁻². Such an anode design approach promotes the efficiency of Mg-air battery, offering renewable and cost-effective energy solutions for electronics and vehicles.