In Situ Preparation And Performance Characterizationo Of Polymer Electrolytes For Lithium Battreies

Nowadays,it is extremely urgent to seek high performance polymer electrolytes with a simple synthetic chemistry and facile preparation technique;However,most researches were focused on aspects of synthesizing novel polymer hosts with suitable ambient temperature conductivity and electrochemical compatibility with high voltage cathodes as well as Li metal anode.Few attention has ever been paid to integrating both synthetic chemistry and processing method into account.Most of polymer electrolytes suffered from a complicated and tedious preparation process.Some were prepared by an ex-situ solution casting technique,which consumed a large amount of organic solvents for polymer and lithium salt dissolution,film casting and solvent evaporation making this process expensive and unfriendly to environment,and increased the fabrication procedures and cost as well.Herein,a facile and reliable in-situ polymerization strategy to prepare polymer electrolytes was presented.The main contents are listed as follows:(1)Polycyanoacrylate is a very promising matrix for polymer electrolyte,which possesses advantages of strong binding and high electrochemical stability owing to the functional nitrile groups.Herein,a facile and reliable in-situ polymerization strategy of poly(ethyl cyanoacrylate)(PECA)based gel polymer electrolytes(GPE)via a high efficient anionic polymerization was introduced consisting of PECA and 4 M LiClO4 in carbonate solvents.The in-situ polymerized PECA gel polymer electrolyte achieved an excellent ionic conductivity(2.7×10-3 S cm-1)at room temperature,and exhibited a considerable electrochemical stability window up to 4.8 V vs.Li+/Li.The LiFePO4/PECA-GPE/Li and LiNi1.5Mn0.5O4/PECA-GPE/Li batteries using this in-situ polymerized GPE delivered stable charge/discharge profiles,considerable rate capability and excellent cycling performance.These results demonstrated this reliable in-situpolymerization process is a very promising strategy to prepare high performance polymer electrolytes for flexible thin-film batteries,micro-power lithium batteries,and deformable lithium batteries for special purpose.(2)The poly(ethylene glycol)diglycidyl ether have high activities due to the two epoxy groups in its structures and could be employed for cross-linking reactions via a cationic polymerization reaction.The lithium salts are based on complex anions that are composed of a simple anion core stabilized by a Lewis acid agent,which could initiate the epoxy ring opening reaction.Herein,a self-catalyzed strategy of Li-ion conducting SPEs composed of cross-linked PEO segments was presented,this in situ synthesis method greatly simplified the assembly process of the all-solid state LIBs.It is manifested that poly(ethylene glycol)diglycidyl based solid polymer electrolyte possess a superior electrochemical stability window up to 4.5 V vs.Li+/Li and considerable ionic conductivity of 8.9×10-5 S cm-1 at ambient temperature.Moreover,The LiFePO4/c-PEGDE-SPEs/Li batteries using this in-situ cross-linked polymerized SPEs delivered stable charge/discharge profiles,considerable rate capability.It is believed that cross-linked poly(ethylene glycol)diglycidyl based electrolyte can be a very promising solid polymer electrolyte candidate for high energy density lithium batteries.