Researches Of Rechargeable Lithium-iodine Battery Based On Iodine/?-cyclodextrin Complex Cathode

In current secondary lithium iodine battery researches: the discharge current of lithium iodine batteries based on porous conductive carbon black fixed iodine is comparable to the super capacitor;The energy density of lithium iodine batteries based on aqueous cathode is almost twice the lithium ion battery.So secondary lithium iodine battery researches is popular in current.The key of secondary lithium iodine battery production is limitting iodine in cathode to act chemical reactions.The innovation point of this paper is introducing a new fixation technology of iodine with low cost for rechargeable lithium iodine batteries,then batteries based on new fixation technology achieved good cyclic performance.By simple solution synthesis,we prepared iodine/ ?-CD complex encapsulated KI₃.Thermogravimetric analysis showed that thermal stability of iodine is enhanced after encapsulated in ?-CD.XPS test shows that ?-CD molecules encapsulated iodine in the form of physical combination.Compared the stability of iodine/?-CD complex in esters electrolyte?1mol/L LiPF₆-EC/EMC/DMC?v:v:v=1:1:1??and ethers electrolyte?1mol/L LiTFSIDOL/DME?v:v=1:1?with 1 wt % LiNO₃ addition?found that the dissolution stability of iodine in the ethers electrolyte is better.Electrochemical performance characterization of iodine/?-CD cathode in ester electrolyte.In ester electrolyte the initial discharge specific capacity is 48 m Ah/g,but the voltage couldn't rise up in the process of charging and couldn't complete circulating charge and discharge test.After we added 0.1 M Li I into the esters electrolyte,the voltage could be charged to 3.5 V.so we conducted cycle charge and discharge processes with 0.1C current density and the discharge specific capacity is about 45mAh/g.the highest coulombic efficiency is 75%,less than 50% after 50 cycles.Electrochemical properties tests of cathode materials with different mass ratio in the ester electrolyte with LiI addition indicated that the best ratio of cathode materials?complex: acetylene black?is 7:3.Electrochemical performance characterization of iodine/ ?-CD cathode in ethers electrolyte.Cycle volt-ampere curve test show that I₃–/I – redox peaks appears in around 3V,the redox peaks of I₂/I₃-couple appears in higher potential around 3.5V.Volt-ampere curve with different scan rates indicated that the electrochemical reaction is diffusion controlled.0.1 C constant current charge and discharge test show that initial discharge specific capacity is 66 mAh/g,the capacity retention is 53 mAh/g after 300 cycles,coulombic efficiency mostly above 90%.Although iodine/ ?-CD cathode displayed good cycle performance in the ethers electrolyte,but the discharge specific capacity and rate performance is poor,and further researches should be done in the later work.