Research On Electrochemical Properties Of Li₂Sn₂（bdc）₃（H₂O）_x Based Quasi Solid-state Electrolyte And Electrolyte Additive

Great progresses have made in lithium-ion batteries in the past decades,which occupy a dominant position in the field of energy storage.However,in recent years,their energy density has been unable to meet the endurance requirements of new energy vehicles and portable electronic devices.Lithium metal battery is a significant developing direction of the next generation rechargeable batteries.However,the existing electrolyte system can not inhibit the growth of lithium dendrites in the operation.The separator may be penetrated by lithium dendrites,resulting in short circuit or safety issues.At present,the scientific researches for inhibiting the growth of lithium dendrites include the interface designing of lithium anode,separator modification,solid-state electrolyte,high concentration electrolyte and functional electrolyte additives,etc.The main research contents are as follows:（1）By adjusting the reaction conditions,uniform polyhedral Li₂Sn₂（bdc）₃（H₂O）_x particles of about 2μm were successfully prepared.The Li₂Sn₂（bdc）₃（H₂O）_x based electrolyte membranes were prepared by mechanical rolling.After soaking with electrolyte,as prepared quasi solid-state electrolyte delivered high ionic conductivity of 4.8×10^-5 S cm^-1,desired Li⁺transference number of 0.61 and excellent electrochemical stability.The energy barrier for lithium ion passing through the Li₂Sn₂（bdc）₃（H₂O）_x lattice channel was determined to be 0.20e V by density functional theory.A stable galvanostatically charging and discharging operation of 900 h could be achieved in a Li|Li symmetric cell at current density of 0.2 m A cm^–2 and capacity of 0.2 m Ah cm^–2.The quasi solid-state electrolyte membrane displayed a significant effect on inhibiting the growth of lithium dendrites according to SEM characterization.After 100 cycles at 0.5 C,the quasi solid-state lithium metal cell with Li Fe O₄ cathode could retain a specific capacity of 158m Ah g^-1,and the average coulombic efficiency was 98.9%.（2）Li₂Sn₂（bdc）₃（H₂O）_x was prepared by the same synthesis method and employed as electrolyte additive.It was found that Li⁺transference number was significantly increased,as well as Li⁺ionic conductivity.A stable lithium plating/stripping process up to 2000 h could be achieved in a Li|Li symmetric battery when the additive amount was 60 mg m L^–1.When the additive amount was 60 mg m L^–1 and 120 mg m L^–1,a specific capacity over 142 m Ah g^–1 could be maintained in Li Fe PO₄|Li cells after300 cycles at 1 C.CV tests proved that the addition of Li₂Sn₂（bdc）₃（H₂O）_xinduced no side reaction.EIS tests also presented that Li₂Sn₂（bdc）₃（H₂O）_xplayed an important role in maintaining the interface stability of lithium metal batteries.The number of figures,tables and references are 37,2,and 87,respectively.