Research On Manganese,Vanadium Based MOF And Composites Materials As Cathode For Aqueous Zinc Ion Batteries

Aqueous Zinc-ion Batteries（AZIBs）have received increasing attention due to the high theoretical capacity(820 m Ah g^-1),low cost,and environmentally friendly nature of zinc metal.Currently,the difficulty in the development of AZIBs is finding a suitable cathode material.Metal-Organic Frameworks（MOFs）with their large specific surface area,abundant metal sites,high porosity and tunable structure are gaining more and more attention in the field of electrochemistry.Graphene has high electronic conductivity and good cyclic stability due to its unique two-dimensional structure,so the composite of the two is expected to yield high-performance electrode materials.The main research contents are as follows:（1）Mn-MOF nanomaterials were obtained by hydrothermal method using manganese chloride tetrahydrate and 1,4-benzenedicarboxylic acid as raw materials,and were used as anode materials for aqueous Zn-ion batteries to investigate the effects of different molar ratios（5:1,5:2 and 5:3）of raw materials on the electrochemical properties of Mn-MOF nanomaterials and AZIBs.The Mn-MOF nanomaterials were composed of irregular blocks with nanoflower-like surfaces.The electrochemical properties were better when the raw material ratio was 5:3.The initial specific capacity reached 63.69 m Ah g^-1at a current density of 100 m A g^-1and the discharge specific capacity was only 0.09 m Ah g^-1for 1500 cycles at a current density of 100 m A g^-1.（2）Hydrothermal synthesis of V-MOF from vanadium oxide sulfate hydrate and 1,4-benzenedicarboxylic acid and the effects of hydrothermal time and active material loading on the performance of V-MOF nanomaterials and AZIBs were investigated.The results showed that at a hydrothermal time of 36 h,the resulting V-MOF materials were hollow nanorods,which were conducive to rapid ion transport,and the best electrochemical performance was obtained by using them as the positive electrode for AZIBs,providing a specific capacity of 144.5 m Ah g^-1at a current density of 0.1 A g^-1.At a current density of 1 A g^-1,its Coulomb efficiency remained at 100%after 4000charge/discharge cycles.The maximum specific capacity of 145 m Ah g^-1was achieved at a load of 2 mg cm^-2.（3）The V-MOF/GH composites were prepared by hydrothermal in-situ compounding.The effects of hydrothermal time（12 h,24 h,36 h and 48 h）and graphene addition（10 mg,20 mg and 30 mg）on the performance of V-MOF//r Go composites and AZIBs were investigated respectively.The results show that the V-MOF//GH//Zn cell has a higher specific capacity of 218 m Ah g^-1for a hydrothermal time of 12 h.The initial specific capacitance is 84 m Ah g^-1at a current density of 1000 m A g^-1,and after 4000cycles,its discharge specific capacity is 115 m Ah g^-1with a Coulomb efficiency of 100%.This indicates that it has excellent cycling stability.The electrochemical performance of the prepared V-MOF/GH composites was even better when the graphene addition was 20mg.The first discharge specific capacity was 263 m Ah g^-1at a current density of 100 m A g^-1.The Coulomb efficiency was 100%after 4000 cycles at a current density of 1000 m A g-1.