Bimetallic Metal–Organic Frameworks as Efficient Cathode Catalysts for Li–O2 Batteries

Abstract

Metal–organic frameworks (MOFs) have the potential to improve the electrochemical performance of Li–O2 batteries with high O2 accessibility and catalytic activity of the open metal sites. Here, we explored bimetallic MnCo-MOF-74 as a cathode catalyst in Li–O2 batteries. MnCo-MOF-74 was synthesized with the Mn to Co ratio of 1:4 by a simple hydrothermal reaction. Compared to monometallic Mn-MOF-74 and Co-MOF-74 with only single catalytic activity for LiOH formation or oxygen evolution reactions, bimetallic MnCo-MOF-74 demonstrated a capability to facilitate improved reversibility and efficiency during both discharge and charge cycles. Benefitting from the porous structure of the MOF as well as the complementary contribution from both Mn- and Co-metal clusters, MnCo-MOF-74 outperformed Mn-MOF-74 and Co-MOF-74. A high full discharge capacity of 11 150 mAh g–1 at 200 mA g–1 was achieved in MnCo-MOF-74. During the cycling test, MnCo-MOF-74 stably delivered a limited discharge capacity of 1000 mAh g–1 for 44 cycles at 200 mA g–1, which is remarkably longer than those of carbon black, Mn-MOF-74, and Co-MOF-74 with cycle lives of 8, 22, and 18 cycles, respectively.