Application Of Metal-organic Complexes And Its Derived Materials In Li-ion Battery

Coordination compounds are a kind of organic/inorganic hybrid material,in which the metal nodes and the ligand are linked through the coordination driven self-assembly.Compared with the traditional electrode materials,Coordination compounds have the characteristics of structural diversity,orderliness,designability,tailability,porosity and high specific surface area,etc..Here,we aimed to design and synthesize the novel coordination compounds,in which more redox centers such as Mⁿ⁺/M^m+,N/N^m+,carboxyl groups were introduced.Furthermore,the electrical performance can be switched by adjusting the crystalline state,structure and porosity of the materials.So these coordination compounds are expected to become a kind of novel electrical materials with high capacity and good recycle performance.The main content of this research is as follows:1.A new ligand[2,2':6',2"-terpyridine]-4,4',4"-tricarboxylic acid has been synthesized through Kr?hnke cyclization using ethyl 2-acetylisonicotinate and furfural as the starting materials.With this ligand,a novel Fe?II?complex with lithium-rich based on terpyridine has been synthesized through coordination driven self-assembly.The structure and morphology of the ligand and the complex was characterized by ¹HNMR,2D COSY,FTIR,TGA and SEM,etc..Here,we introduced many redox centers such as Fe?II??pyridine N and carboxyl groups.The data from electric performance test displayed that this Fe?II?complex is an excellent anode materials for Li-ion battery.The measured specific capacity was 290 mAh/g after 100cycles at 0.3 C current rate.In order to further improve electrochemical performance of this Fe?II?complex,we prepared the Fe?II?complex/graphite composites using mechanical mixing combined with ultrasonic dispersion.The relevant electrical performance test results show that the charge transfer resistance of the battery becomes smaller,and the actual specific capacity of the material improved.2.A new ligand[2,2':6',2"-terpyridine]-4,4',4"-tricarboxylic acid has been synthesized through Kr?hnke cyclization using pyridine 4-carboxylate and benzaldehyde as the raw materials.With this ligand,a novel Fe?II?complex based on terpyridine has been synthesized through coordination driven self-assembly.Then,the complex was carbonized by a calcination at high temperature to form a carbon-based iron-nitrogen composite material.The structure and morphology of complex and Fe/N composites in carbon matrix materials were characterized by ¹HNMR,SEM,EDX,XRD,XPS,TGA and BET.The results show that the composite is nanoscale mesoporous material,and the pore size distribution is concentrated,which is conducive to the migration of lithium ions.We use this material as a electrode material test its electrochemical behaviors.The data from electric performance test displayed that the composite is an excellent anode materials for Li-ion battery.The measured specific capacity was 390 mAh/g after 100 cycles at 0.3 C current rate.