Synthesis Of The Polymeric Ionic Liquid And Its Electrochemical Property

Lithium ion batteries?LIBs?have been widely applied to electric vehicles and energy storage system as promising energy sources for their high energy density,high operating voltage,long cycle life,low self-discharge,excellent rate capability and no memory effect.With the increasingly wider usage range,the safety of LIBs has been paid more attention for their explosion risk arising from carbonic ester type electrolyte.So researchers focus more on the exploitation of safe electrolyte.Solid state electrolyte is a kind of new type safe electrolyte,which has no flammability,and it is the key technology for thorough solution of LIBs safety.Polymeric ionic liquid?PIL?,who combines the good mechanical property of polymer and the high ionic conductivity of ionic liquid,has achieved much more attention.But people's learning towards the conductive mechanism of PIL are still incomplete.PILs of different structures usually present different ionic conductivity,and we synthesized three structure-comparable PILs to explore the structure influence on ionic conductivity.We study the ionic conductivity of them and the outcomes could be the design gist for further study.The polymeric ionic liquids we synthesized this paper are:P1,whose charge center is close to main chain,P2,whose charge center is far away from main chain,and P4,whose charge center is far away from main chain while there is an oxygen-containing spacer between main chain and charge center.The ionic liquids we synthesized this paper are:M1 and M2,whose charge center are close to or far away from the unsaturated group respectively;M3 and M4,whose charge center are close to or far away from the unsaturated group respectively while they have an oxygen-containing spacer.In our work,we get the aim products through the quaterisation,ionic exchange and radical polymerization,and we creatively conduct the ionic-liquid-making reaction with methacrylate in the synthesis procedure of M3 and M4.In this paper,the structure and composition of synthesized materials were characterized by ¹H-NMR,fourier transform ion cyclotron resonance mass spectrometer,thermogravimetry-diffenential thermal analysis?TG-DTA?and Differential Scanning Calorimeter ?DSC?.The electrochemical property of PILs were characterized by electrochemical impedance spectroscopy?EIS?and linear sweep voltammetry?LSC?.In our work,we finally got three kinds of PILs named P1,P2 and P4,and their ionic conductivity at 30?are 1.1×10^-6S/cm,2.2×10^-4S/cm and 4.22×10^-4S/cm respectively.The electrochemical stability of P2 are exceed 7V?VS.Li/Li⁺?.The5%weight-loss temperature of P1 and P2 are 369.05?and 233.63?respectively.We also studied the influence of lithium-salt concentration on ionic conductivity of PIL and tried to explain the phenomenon from the point of molecular structure.Above all,we got three structure-comparable PILs and structural features of long length alky chain and long distance between main chain and charge center are good for ionic conductivity improvement.The oxygen-doping is beneficial for lithium-salt's dissociation.