Synthesis And Modification Of Metal Organic Frameworks (MOF) And Their Application For Lithium Sulfur Batteries

Abstract:Lithium-sulfur battery is a very promising high energy density battery system. High specific capacity and good cycle performance porous skeleton/sulfur composite electrode material attracted intensive attention. The porous framework with a good conductive network, high specific surface area, proper pore structure and size are suitable to improving electrochemical activity, sulfur adsorption property and structural stability of sulfur electrode, which has become more and more important for lithium-sulfur batteries.Metal organic framework was selected and used as the porous skeleton. Two types of porous metal organic framework Cr3F(H2O)2O (BDC)3·nH2O (MIL-101) and Zn4O(BDC)3(MOF-5) were synthesized with large specific surface area and suitable pore size, which were resulted by carbonized or modified in situ coating. There are three types of porous skeleton/sulfur composite electrodes,(MIL-101(Cr)@rGO/S, MWCNT@Meso-C/S and GO@Meso-C/S), were successfully synthesized and investigated. The main results are followed.The results are presented as follows, Mesoporous metal organic framework@reduced graphene oxide (MIL-101(Cr)@rGO) materials have been used as a host material to prepare the multi-composite sulfur cathode through a facile and effective two-step liquid phase method successfully, The successful reduced graphene oxide coating in the MIL-101(Cr)@rGO improve the electronic conductivity of meso-MOFs effectively. The discharge capacity and capacity retention rate of MIL-101(Cr)@rGO/S composite sulfur cathode are as high as650mAh g-1and66.7%at the50th cycle at the current density of335mA g-1.A hierarchical architecture of multi-walled carbon nanotubes@mesoporous carbon (MWCNT@Meso-C) using unique multi-walled carbon nanotubes@metal-organic framework (MWCNT@MOF-5) as both the template and precursor were synthesized and investigated. Active sulfur is encapsulated into the MWCNT@Meso-C matrix prepared via carbonize MWCNT@MOF-5polyhedrons for high performance lithium sulfur battery. The initial and50th cycle discharge capacity of MWCNT@Meso-C/S sulfur cathode are as high as1343mAh g-1and540mAh g-1at a high current rate of0.5C, indicating that the MWCNT@Meso-C is a promising host material for the sulfur cathode in the lithium sulfur battery applications.At the same time, a design and synthesis of a hierarchical architecture of graphene oxide@mesoporous carbon (GO@Meso-C) using graphene oxide@metal-organic framework hybrid materials (GO@MOF-5) as both the template and precursor was presented. Active sulfur is encapsulated into the GO@Meso-C matrix prepared via carbonize GO@MOF-5polyhedrons for high performance lithium sulfur battery. The initial and100th cycle discharge capacity of GO@Meso-C/S sulfur cathode are as high as1122mAh g-1and820mAh g-1at a current rate of0.2C.