Solid polymer electrolyte membranes of trimethylsulfonium bis(trifluoromethylsulfonyl)imide/NaClO4/PEO for Na-ion batteries

Ionic liquid trimethylsulfonium bis(trifluoromethylsulfonyl)imide (M3STFSI) was synthesized to obtain solid polymer electrolyte (SPE) membranes by mixing it with polyethylene oxide and sodium perchlorate (NaClO4). Nine membranes were prepared with varying concentrations of high, medium, and low polymer content. X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, Fourier transform infrared spectroscopy and Raman spectroscopy techniques were used to characterize both the products and the raw materials. Ionic conductivity was determined using electrochemical impedance spectroscopy (EIS), and redox phenomena were studied by cyclic voltammetry. To calculate the total ion transference number and Na+ ion transference number, chronoamperometry (CA) with EIS was employed. Additionally, the electrochemical stability in SPE (M1) was measured through linear sweep voltammetry (LSV). The NaFe(SO4)(2) compound, known as Eldfellite, was utilized as a cathode in Na-ion battery tests. A Na||M1||NaFe(SO4)(2) cell was prepared to determine the battery performance via galvanostatic charge/discharge profiles. Thus, the theoretical specific capacity of Eldfellite for Na+ insertion is 99 mAh g(-1), and after 70 cycles at a C/10 rate vs. Na-0 metallic as an anode, the specific discharge capacity was 75 mAh g(-1), with a coulombic efficiency above 99%.

Automated summary

Ionic liquid trimethylsulfonium bis(trifluoromethylsulfonyl)imide was synthesized and combined with polyethylene oxide and sodium perchlorate to produce solid polymer electrolyte membranes. Various techniques were used to characterize the materials and products, and electrochemical tests were conducted to determine the ionic conductivity and battery performance. These membranes showed promising results in terms of specific capacity and coulombic efficiency for Na-ion battery applications.