| In recent years, metal organic frameworks(MOFs), as a new type of electrode materials for lithium-ion secondary battery MOFs have attracted muche attention. However, the relationship among the synthesis conditions, the spatial structure and the electrochemical properties of this kind of materials needs further research. In this paper, five kinds of MOFs electrode materials based on three series of organic ligand benzene dicarboxylic acid, naphthalene diacid, and pyridine dicarboxylic acid were synthesized, respectively. This paper discussed the synthesis methods, the electrochemical performance and the relationship between structure and performance of all kinds of materials and system, the specific work as follows:(1) Heat reflux method and solvothermal method were used to synthesize the Co2(OH)2BDC(BDC = 1,4-benzenedicarboxylate) electrode materials, it was synthesized for the first time by a through the reaction of Co2+ with a bio-inspired renewable organic ligand 1,4-benzenedicarboxylic acid. We discussed the synthesis method of Co2(OH)2BDC electrode material in solvent composition on its electrochemical properties. The samples were characterized by FTIR, XRD, SEM, constant current charge-discharge experiment and cyclic voltammetric curves(CV). The experimental results showed that the sample synthesized by solvent has higher purity and crystallinity. As an anode material for lithium ion batteries, this material exhibited a large reversible capacity of ca. 650 mAh g-1 at a current density of 50 m A g-1 after 100 cycles within the voltage range of 0.02-3 V. When the mole ratio of water/ethanol/DMF is 1:1:1 in the solvothermal route, the resulted Co2(OH)2BDC sample exhibits higher specific capacity and better cycle performance.(2) In order to study the effects of the expansion of the aromatic ring in conjugate system on the properties of electrode materials, using the polycyclic aromatic diacid 2,6-naphthalene acid as a ligand. The crystalline 2,6-naphthalene acid lithium(Li2NDC) samples were synthesized by the solvothermal and solution routes, respectively. The results showed that the materials by the solventermal and the solution method have the same chemical composition and spatial structure, but the size(50 μm) of the Li2 NDC particles by the solventermal method is larger than that(3 μm) by the solution method. The charge-discharge performance tests showed that compared to the materials prepared by the solventermal method, the materials prepared by the solution method have the better specific capacity and cycle stability, under the same test conditions.(3) Choosing 2 pyridine three homologue of formic acid as as ligands which react with lithium hydroxide, we try to prepare corresponding organic lithium salts, and study the charging/discharging performance of the products as an anode for lithium ion battery. The preliminary data shows that 2,5-pyridine carboxylic acid lithium, charge and discharge specific capacities of 195.0 mAh g-1 and 201.2 mAh g-1, respectively, after 60 cycles. Compared with 3,4-pyridine carboxylic acid lithium and 3,5-pyridine carboxylic acid lithium, it exhibits a better electrochemical cycle performance, which may be attributed to formation of stable conjugate structure during the process of charging lithiated process, which promotes the transfer of electrons in para acid salt. |
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