Single-Ion Conducting Electrolyte Based on Electrospun Nanofibers for High-Performance Lithium Batteries

Herein, a novel electrospun single-ion conducting polymer electrolyte (SIPE) composed of nanoscale mixed poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and lithium poly(4,4′-diaminodiphenylsulfone, bis(4-carbonyl benzene sulfonyl)imide) (LiPSI) is reported, which simultaneously overcomes the drawbacks of the polyolefin-based separator (low porosity and poor electrolyte wettability and thermal dimensional stability) and the LiPF 6 salt (poor thermal stability and moisture sensitivity). The electrospun nanofiber membrane (es-PVPSI) has high porosity and appropriate mechanical strength. The fully aromatic polyamide backbone enables high thermal dimensional stability of es-PVPSI membrane even at 300 °C, while the high polarity and high porosity ensures fast electrolyte wetting. Impregnation of the membrane with the ethylene carbonate (EC)/dimethyl carbonate (DMC) (v:v = 1:1) solvent mixture yields a SIPE offering wide electrochemical stability, good ionic conductivity, and high lithium-ion transference number. Based on the above-mentioned merits, Li/LiFePO 4 cells using such a SIPE exhibit excellent rate capacity and outstanding electrochemical stability for 1000 cycles at least, indicating that such an electrolyte can replace the conventional liquid electrolyte–polyolefin combination in lithium ion batteries (LIBs). In addition, the long-term stripping–plating cycling test coupled with scanning electron microscope (SEM) images of lithium foil clearly confirms that the es-PVPSI membrane is capable of suppressing lithium dendrite growth, which is fundamental for its use in high-energy Li metal batteries.