Researchers from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) and Henan Agricultural University have designed two-dimensional (2D) Mn3O4 nanosheets with dominant crystal planes on graphene (Mn3O4 NS/G) as efficient oxygen catalysts for Li-O2 batteries, achieving ultrahigh capacity and long-term stability.
The team explained that designing oxygen catalysts with well-defined shapes and high-activity crystal facets can effectively regulate the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at the three-phase interfaces, but it is still remains challenging. The researchers reported that the Mn3O4 NS/G with the (101) facets and enriched oxygen vacancies offered a lower charge overpotential of 0.86 V than that of Mn3O4 nanoparticles on graphene (1.15 V).
Moreover, Mn3O4 NS/G cathode exhibited long-term stability over 1,300 hours and ultrahigh specific capacity up to 35,583 mAh/g at 200 mA/g, outperforming most Mn-based oxides for Li-O2 batteries reported.
Both the experimental and theoretical results showed the lower adsorption energy of Mn3O4 (101) for the discharge product Li2O2 in comparison with Mn3O4 (211), manifesting the easier decomposition of Li2O2 during the charging process.
"This work may provide clues for engineering Mn-based materials with defined crystal facet for high-performance Li-O2 batteries," said Prof. Zhong-Shuai Wu from CAS.