Optimization effect of Ag-regulated manganese oxides on electrocatalytic performance for Li–O2 batteries

Abstract

Developing efficient and inexpensive electrocatalysts for sluggish reaction kinetics is important to help non-aqueous Li–O₂ batteries achieve an ultra-high theoretical specific energy density of ∼3500 W h kg⁻¹. Introducing Ag into MnO₂ to promote catalytic activity is efficient. However, the detailed roles of incorporated Ag and actual active sites of Ag-regulated manganese oxides need to be further investigated. Here, we unravel that Ag in manganese oxides mainly plays the key role in regulating bulk electronic structures and adsorption energy towards intermediator LiO₂, but it does not work as the real active sites during the electrochemical process. Experimental and density functional theory (DFT) calculation demonstrates that enhanced conductivity and electrocatalytic activity are dominantly attributed to the increment of oxygen vacancies and Mn³⁺ caused by Ag incorporation. According to the DFT result, LiO₂ is found to interact with the Mn ions and lattice oxygen, indicating that it acts as actual catalytic sites. This work provides an insight into elucidating the enhancement mechanism of electrocatalytic activity after incorporating Ag⁺ and actual catalytic sites of manganese oxides.