Modification Design Of Manganese Based MOFs Derived Electrode Materials For Zinc Storage Properties

With the development of society,the demand for electronic products is increasing,which promotes the progress of energy storage system.Compared with lithium ion battery,zinc ion battery has the advantages of safety and environmental protection.Moreover,the abundant zinc resources and the assembly in the air greatly reduce the manufacturing cost of the battery,which is expected to become a large-scale application of energy storage system.The selection of cathode material for zinc ion battery greatly affects the mechanism and performance of the battery.At present,manganese based cathode has higher working voltage and more oxidation states,so it becomes a very attractive cathode material.However,the semiconductor properties of manganese-based compounds lead to poor conductivity,and the loss of active material due to the dissolution of Mn²⁺during cycling,making the actual specific capacity much lower than the theoretical capacity.Therefore,the rational design of manganese-based compounds to realize their energy storage potential still requires a lot of research.Therefore,the rational design of manganese based compounds to exploit their energy storage potential still needs a lot of research.In this thesis,the modification design of manganese-based cathode materials and the study of energy storage mechanism are studied.Using the manganese foundation metal-organic framework as the precursor,combined with design strategies such as defect engineering,ion doping and structural recombination,the research results are as follows:1.Mn₂O₃ and MnO with oxygen defects are obtained by thermal oxidation of Mn-BTC in different atmospheres.By means of SEM,XRD,EPR and electrochemical testing,the influence of calcination atmosphere on morphology,crystal structure and oxygen defect content on energy storage performance was analyzed.The results show that MnO has obvious carbon coating structure and more oxygen defects（23.4%）,which makes it have more outstanding zinc storage performance.The specific capacity can reach 74.5 m Ah g^-1 at the current density of 1.5 A g^-1.At the same time,PVA/Zn（CF₃SO₃）₂ gel electrolyte was prepared and assembled into quasi-solid state batteries,which still showed good magnification performance and stability.2.ZnCoMn-BTC precursor is calcined in argon to obtain ZnCoco-doped MnO/C.The influence of doping on the content of Mn²⁺/Mn³⁺was investigated by XRD,XPS,etc.The effects of the type and content of doping ions on the properties were investigated by electrochemical testing.The results show that ZnCoco-doped can effectively improve the low initial capacity of MnO and the poor stability caused by the John-Taylor effect,and the specific capacity can reach 62.6 m Ah g^-1 at the current density of 3.0 A g^-1.In addition,the energy storage mechanism was studied by XRD and XPS.At the same time,to further improve the performance,we used the fused salt etched Ti₃C₂ spinning coated Zn foil（Zn@Ti₃C₂）as the negative electrode and assembled the full battery for performance test,which greatly improved the rate performance and stability.At the current density of 3.0 A g^-1,the specific capacity can reach 81.8 m Ah g^-1.3.The precursor of Mn-BTC/Ti₃C₂ is treated with sulfur and selenization in nitrogen at high temperature to obtain Se-MnS/Ti₃C₂ containing sulfur defects.The electrochemical test shows that the S defect induced by Se doping can improve the conductivity of the materials.At the same time,the introduction of Ti₃C₂substrate is beneficial to expose more sulfur defects and improve the utilization rate of defects.The energy storage mechanism was studied by XRD and XPS.MnS converted into S/Se co-doped Mn₃O₄ in the first charging process,which endowed it with higher zinc storage performance.At the current density of 5.0 A g^-1,the specific capacity can reach 74.7 m Ah g^-1.At the same time,we prepared Zn-Ti₃C₂ membrane electrode as negative electrode by vacuum filtration method,and assembled it into rocking chair battery,showing good magnification performance.