Ultrathin Two-Dimensional Metal–Organic Framework Nanosheets with the Inherent Open Active Sites as Electrocatalysts in Aprotic Li–O₂ Batteries

Abstract

Ultrathin two-dimensional metal−organic frameworks (2D MOFs) have the potential to improve the performance of Li−O 2 batteries with high O 2 accessibility, open catalytic active sites, and large surface areas. To obtain highly efficient cathode catalysts for aprotic Li−O 2 batteries, a facile ultrasonicated method has been developed to synthesize three kinds of 2D MOFs (2D Co-MOF, Ni-MOF, and Mn-MOF). Contributing from the inherent open active sites of the Mn−O framework, the discharge specific capacity of 9464 mAh g −1 is achieved with the 2D Mn-MOF cathode, higher than those of the 2D Co-MOF and Ni-MOF cathodes.During the cycling test, the 2D Mn-MOF cathode stably operates more than 200 cycles at 100 mA g −1 with a curtailed discharge capacity of 1000 mAh g −1 , quite longer than those of others. According to further electrochemical analysis, we observe that the 2D Mn-MOF outperforms 2D Ni-MOF and Co-MOF due to a superior oxygen reduction reactions and oxygen evolution reactions activity, in particular, the efficient oxidation of both LiOH and Li 2 O 2 . The present study provides new insights that the 2D MOF nanosheets can be well applied as the Li−O 2 cells with high energy density and long cycling life.

2D framework materials for energy applications

“…Due to the very simple exfoliation methods, the convenient availability and the easy handling, 2D MOFs, based on the H 2 bdc linker, are also widely utilized in various battery applications. 183,185,194 Especially the manganese compound could demonstrate better results than their cobalt and nickel derivatives both as anode material for LIBs 183 and as cathode material in aprotic Li-O 2 batteries. 185 In addition, Li et al 194 designed a separator based on ultrathin (1.2 nm) Co 2 (bdc) 2 nanosheets which enhances the safety and lifetime of lithium-sulphur batteries by simultaneously suppressing Li dendrite growth and alleviating polysulde shuttling.…”

Two‐Dimensional MOF and COF Nanosheets: Synthesis and Applications in Electrochemistry

“…The ultrathin 2D MOF nanosheets not only inherits the characteristics of massive MOFs, but also has a higher proportion of metal atoms exposed on the surface. It has more coordination unsaturated metal sites with suspended bonds, which is of great significance for electrocatalysis . Recently, under the action of surfactant PVP, Xu et al.…”

Porous Materials Applied in Nonaqueous Li–O2 Batteries: Status and Perspectives

“…Aside from 3D structures, 2D/1D electrodes also play important roles in the construction of porous structures. A series of 2D MOFs were prepared as cathode electrocatalysts for Li-O 2 batteries by Yuan et al [51] The ultrathin 2D MOFs with the nanometer thickness not only ensured fast electron transfer and rapid mass transport, but also afforded enough space for Li 2 O 2 accommodation. Furthermore, Huang et al assembled RuO 2 nanosheets in situ that possessed lateral micrometer size and nanometer-scale pores with CNT interlayers.…”

“…A series of 2D MOFs were prepared as cathode electrocatalysts for Li–O 2 batteries by Yuan et al. [ 51 ] The ultrathin 2D MOFs with the nanometer thickness not only ensured fast electron transfer and rapid mass transport, but also afforded enough space for Li 2 O 2 accommodation. Furthermore, Huang et al.…”