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 LiPF6 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 degrees 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/LiFePO4 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.