The Energy Storage Performances And Mechanisms For High Capacity Metal-Organic Anode Material

With the exploration and ulilization of clean energy resources and the rapid growth of energy stroge requirements,Lithium ion batteries（LIBs）as a typical electrochemical energy storage technology have been widly used.But,limited by thium sources and the increasing prices,developing new systems,new technologyes,new materials should be an important solution for rechargeable batteries.Sodium-ion batteries（SIBs）are now actively developed as low cost and sustainable alternatives to Li-ion batteries（LIBs）for large-scale electric energy storage（EES）applications.Compared to inorganic electrode compounds,metal organic compounds are competitive for the abundance of their resources,environmental friendliness and controllable structures.They are proposed as promising electrode materials for the next-generation energy storage devices due to the increased demand for inexpensive and sustainable technologies.In this thesis,our strategy is to design the materials with multiple active sites for energy storage,which can improve the specific capacity of the material by the reversible electrochemical reaction of multiple electrons transfer.We will focus on the salts of perylenetetracarboxylates,based on the investigation of the electrochemical properties,the lithium/sodium storage mechanisms are discussed,and the design strategies of the high specific capacity electrode materials for rechargeable batteries are proposed.Solutions presented in this thesis can be summarized as follows:-We design a metal-organic compound zinc perylenetetracarboxylates（Zn-PTCA）with a stable 3D open framework structure,which is investigated as an anode material for sodium-ion batteries.Zn-PTCA delivers a high reversible specific capacity of 357.1 mAh g^-1 at a current density of 50mA g^-1 within the potential window of 0.01-2 V vervus Na/Na⁺,corresponding to an eight-electron transfer process.A combination of ex-situ X-ray photoelectron spectroscopy（XPS）,Fourier transform infrared（FT-IR）,and in-situ X-ray diffraction（XRD）,indicate that Zn-PTCA enables the aromatic rings activated as Na⁺-storage redox sites.It shows two active storage sites of C=O in carboxylate groups and aromatic rings.Meanwhile,the calculations also provide a stepwise mechanism of double bond reformation and p-πconjugation.We have developed two important factors,which are stable 3D framework structure and electron stabilization mechanism,essentially contribute to the activation of aromatic rings to realize more Na ions storage.-Zn-PTCA delivers a favorable cycle performance and excellent rate property in LIBs.Zn-PTCA shows a high revesible specific capacity of 627 mAh g^-1 when the coulombic efficiency becomes to 98%,corresponding to a fourteen-electron transfer process.With the ex-situ Raman and FT-IR tests,the lithium ion storage mechanism is obtained,which is similar to the sodium ion storage mechanism.As to the smaller radius and repulsive force of lithium ions,more sp²-hybridzed carbons in aromatic rings are involoved in the lithium insertion processes.-In this thesis,we found that metal organic coordination bonds play an important role to form stable 3D framework structure and improve the electrochemical performce.Unraveling the Li⁺/Na⁺insertion mechanism will open up new perspectives for designing novel metal-organic electrode materials with multi-electron redox processes.