Research On Cathode And Anode Materials Of Lithium-Ion Batteries Based On Metal-Organic Frameworks

The rapid development of lithium-ion batteries places higher demands on the specific capacity of the cathode and anode,Metal-Organic Frameworks?MOFs,also referred as coordination polymers,CPs?are rich in composition and adjustable in structure,and have been more prominent in the electrochemistry.Therefore,this paper utilizes MOFs as the cathodes and anodes of lithium-ion batteries,and explores its electrochemical performance and reaction mechanism.The details are as follows:For the first time,terephthalonitrile as reactant,nanowire-structured coordination polymer Co-BDCN-24h with terephthalamide?referred as BDCN?as the organic ligand was synthesized by solvothermal method?liquid magnetic resonance and solid state magnetic resonance were applied to characterize the coordination of Co and BDCN?,which was applied to the anode of lithium battery.A reversible capacity of 1132 mAh g^-11 was retained after 100 cycles at a current density of 100 mA g^-1,higher than most other lithium-ion battery anode materials based on MOFs/CPs.The results of the characterization indicated that the excellent electrochemical performance performances were mainly attributed to the synergistic effect of the organic ligand and the Co²⁺center and the excellent stability of the nanowire structure.In addition,we also tried to synthesize a series of CPs as the anode by hydrothermal method with 1,2,4,5-benzenetetracarboxylic acid?abbreviated as BTEC?as the organic ligand.The specific capacity of{K₂[(Zn_0.5Ni_0.5)₃?BTEC?₂?H₂O?₄]}remained 593.8 mAh g^-1 after 100 cycles at 100 mA g^-1,which is much better than other materials in the same series;NiCl₂-TDC was synthesized with 2,5-thiophene dicarboxylic acid?abbreviated as TDC?as the organic ligand.It was found that the NiCl₂-TDC sample synthesized by microwave in the mixture of absolute ethanol and deionized water?V:V=1:1?had the best crystal form and the best electrochemical performance.The specific discharge capacity was still 411.1 mAh g^-11 after 500 cycles at 2000 mA g^-1.Finally,preliminary exploration of CPs/MOFs material as lithium-ion cathode material was carried out.[Cu₂I_2??DPNDI]_n with N,N'-di-?4-pyridyl?-1,4,5,8-naphthalene diimide?DPNDI?as the organic ligand was synthesized,which was applied to the cathode of the lithium-ion battery.At a 30 mA g^-1 current density,the specific capacity increased to a maximum of 77.6 mAh g^-1 at the 3rd cycle,and then decayed to 20.9 mAh g^-1 at the 100th cycle.We tried to optimize the electrode,by the means of adding HDI?isocyanate?to the electrolyte and increasing the proportion of the conductive agent,cycling stability improved to some extent.