Application Of In-Co/Ni-Li-BTC Multi-Component MOFs In Lithium Ion Batteries

With the increasing of energy demands and the development of energy storage technology,the traditional devices of electrochemical energy storage don’t satisfy the demand of electric vehicles,energy storage power stations and other fields.Therefore,the exploitation of secondary batteries with high specific energy and long life has become a research point in academic and industrial fields.As the significance of secondary batteries,traditional lithium-ion batteries have been industrialized due to a series of advantages.However,the practical capacity and rate performance of the batteries are greatly affected because of its low conductivity,ion diffusion coefficient and poor cycling performance,which limits its large-scale application.In the perspective of these shortcomings,several new metal-organic frameworks were designed and synthesized as cathode materials for lithium-ion batteries.The effects of various structures on the properties of batteries were studied,which provided a theoretical basis for subsequent design and synthesis about novel ion batteries.At the same time,it shows that the metal-organic frameworks（MOFs）have a wide viewpoint of applications in secondary batteries.This paper consists of three parts:（1）Binary MOF materials were successfully synthesized by a simple solvothermal method using H₃ BTC as the organic ligand and lithium as metal center.The MOF materials were directly used as cathode materials for lithium ion batteries without any other treatment.It is characterized by powder X-ray Diffraction,Thermogravimetric Analysis and Infrared Spectroscopy.The experimental results show that the first discharge capacity is 253.7 m Ah g^-1,and the discharge capacity decreases in subsequent cycles.After 100 cycles,the discharge specific capacity is 105.5 m Ah g^-1.And after 500 cycles,the discharge capacity is 101.7 m Ah g^-1,the Coulomb efficiency is 99.03%.It suggests that the MOF has good cycling performance.（2）The ternary cobalt/lithium coordination compounds SNNU-76 and SNNU-73 with two different structures were synthesized by BTC and Li⁺/Co²⁺ bimetallic Inspired by Li Co O2,a traditional material of lithium-ion battery.The SNNU-76 and SNNU-73 were applied in lithium-ion batteries for the first time.Co²⁺ and Li⁺ in two different structures are located at the different active site（SNNU-76）and same active sites（SNNU-73）.The results show that the square channel MOF material（SNNU-73）with helical chain structure constructed by two metals at the same active site possessed higher specific capacity,while the MOF of cage structure constructed by two metals at different active sites had better cycling performance.（3）A binary In-BTC（CPM-5）material was treated by ion-exchange in different solvents（organic and inorganic solutions containing lithium ions,respectively）,and the electrochemical properties of organic solvents and inorganic solvents were compared.Under the optimum conditions,ternary In-Co-BTC and In-Ni-BTC were also treated respectively.The results showed that the materials treated with organic solvents maintained the original framework and exhibited better electrochemical performance:At the current density of 100 m A g^-1,the specific discharge capacities are 96.5/96 m Ah g^-1 and 150/140 m Ah g^-1 after 50 and 500 cycles,respectively.And the Coulomb efficiency is above 99 %.It is also proved that the crystalline water in the pore of the material is not completely removed after treatment with inorganic solvents,and the existence of crystalline water has a certain impact on the cycling performance.The use of organic solvents can improve the conductivity,ion diffusion rate and electrochemical properties of materials.