Lithium-oxygen (Li-O2) battery is one of the most promising batteries due to its high theoretical energy density. However, the poor catalytic performance of its air-cathode impeded its commercialization.
Recently, a joint research group led by Prof. BAO Xinhe and Prof. WU Zhong-Shuai from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) has fabricated two-dimensional (2D) Mn3O4 nanosheets with dominant crystal planes on graphene (Mn3O4 NS/G) as efficient oxygen catalysts Li-O2 batteries, achieving ultrahigh capacity and long-term stability.
This study was published in ACS Catalysis on Oct. 7.
Schematic diagram of structure, cycling performance and working mechanism of 2D Mn3O4 NS/G (Image by LI Yuejiao)
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 indicated 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 proved 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. WU.
The above work was supported by the National Natural Science Foundation of China, and Dalian National Laboratory for Clean Energy of CAS. (Text by LI Yuejiao)