Preparation And Characterization Of Polymer Electrolytes Based On Single Ion Conductor LiPSTFSI

At present,commercial liquid electrolytes used in lithium-ion batteries have exposed serious safety problems,such as flatulence and easy leakage during the charging/discharging process,which hinders the development of lithium-ion battery technology to a certain extent.While solid polymer electrolytes(SPEs)can fundamentally overcome the shortcomings of liquid electrolytes,they are safer and also have lighter weight and better processability.However,most of the traditional SPEs are double-ion conductors.This system has a low Li⁺transference number,and the concentration polarization caused by the migration of lithium salt anions will further reduce the voltage and capacity of the battery.Therefore,the design and preparation of single-ion conductors with a Li⁺transference number close to 1 has become one of the research hotspots in the field of polymer electrolytes.In this paper,Lithiumpoly(4-styrenesulfonyl(trifluoromethylsulfonyl)imide)(Li PSTFSI)was synthesized by polymerization of Lithium(4-styrenesulfonyl(trifluoromethylsulfonyl)imide)(Li STFSI).The anion of lithium salt is bound to the polymer backbone,and then blended with polyethylene oxide(PEO)to prepare a single-ion conductor polymer electrolyte with a Li⁺transference number close to 1.The experiment research contents and results are as follows:(1)A simple blending method was used to prepare solid-state single-ion conductor polymer electrolyte PEOn/Li PSTFSI with different EO/Li⁺by solution casting of PEO and Li PSTFSI,and the thermal behavior,membrane morphology,and ionic conductivity of the electrolyte membrane were systematically studied.,Li⁺transference number and electrochemical stability.(2)By comparing the ionic conductivity and lithium ion migration number of PEOn/Li STFSI SPEs with the same EO/Li⁺as PEOn/Li PSTFSI,the experimental results show that when the temperature reaches 60°C,PEO/Li PSTFSI(EO/Li⁺=16)SPEs The ionic conductivity reaches 1.94×10^-5S/cm,which is slightly higher than the ionic conductivity of PEO/Li STFSI(EO/Li⁺=16)SPEs,which is1.08×10^-5S/cm.At the same time,the Li⁺transference number of PEOn/Li PSTFSI polymer electrolyte is more than 0.88 at 60?,and its lithium ion transference number is significantly higher than that of PEOn/Li STFSI polymer electrolyte,indicating the single-ion conduction behavior of PEOn/Li PSTFSI polymer electrolyte.(3)The SPEs of PEO/Li PSTFSI(EO/Li⁺=16)were assembled into a symmetric battery Li|SPEs|Li at 60°C.The interfacial compatibility between electrolyte and metal lithium was investigated by monitoring the AC impedance test for 30 days.The experimental results showed that,the interfacial resistance of SPEs with EO/Li⁺of 16slowly increased at the beginning,and then began to decrease slowly after 120 h,indicating that the electrolyte began to have good contact with the lithium electrode after 120 h,and the interface between the electrolyte and the lithium electrode began to be compatible.(4)Cyclic voltammetry tests on Li|SPEs|Li Fe PO₄batteries confirmed that the SPEs of single-ion conductor PEO/Li PSTFSI(EO/Li⁺=16)have good reversibility in batteries and compatibility with Li Fe PO₄electrodes good.