Tailored nonwoven supported non-flammable quasi-solid electrolyte enables an ultra-stable sodium metal battery

An easily scalable approach to developing nonwoven-supported PVDF-HFP polymer-based quasi-solid-state flexible non-flammable electrolyte shows a conductivity of 1.16×10-4 S/cm at RT with a transfer number of 0.68. The Na3V2(PO4)3 (NVP)...


Electrolyte Preparation
Quasi-solid-state electrolytes are developed by following a simple solution cast procedure.polymer electrolytes.
First, by continuously stirring P(VDF-HFP) in acetone using a magnetic stirrer and heating at 60℃, 15 wt% P(VDF-HFP)/acetone was prepared.After P(VDF-HFP) was completely dissolved, the viscous solution was poured onto a nonwoven (NW) sheet (Oripol Industries, INDIA) and kept in a vacuum oven at 70 °C for 24 h to form a nonwoven textile-supported solid polymer mat (NW-SPM).The flexible dried mat is soaked/swallowed to form a gel within a particular liquid electrolyte to prepare a nonwoven-supported quasi-solid polymer electrolyte (NW-QSSE).The prepared compositions are the following.NW-SPM: A nonwoven fabric with a 15% w/w coating of PVDF-HFP polymers.The fabric is rolled to reduce the thickness of 112 μm.

A. Sample Characterization
A Bruker diffractometer (USA) with Cu Kα radiation (λ = 1.5Å) was used to record The X-ray diffraction (XRD) patterns of the developed electrolytes.The thermal stability of the QSSE was investigated by TGA (PerkinElmer, Pyris Diamant, SDT 1606, USA) at a scanning rate of 10°C/ min from RT to 650°C in an inert atmosphere (nitrogen).The DSC was carried out with a heating rate of 10 °C/ min to measure melting temperature and melting enthalpies.The surface morphology of the asprepared films was determined by field emission scanning electron microscopy (FESEM) (MERLIN, Germany).A PHI 5000 Versa Probe II system with monochromatic Al Kα (1486.6 eV) radiation at 100 W power was used for X-ray photoelectron spectroscopy (XPS).For binding energy calibration, the C 1s (284.8 eV) spectrum was fixed as the baseline spectrum.

B. Electrochemical characterization
An LCR meter (biological instrument) was used for the conductivity experiment.Electrolyte films were held between a pair of stainless-steel blocking electrodes (diameter ~ 16 mm) for electrical measurements.
A cell as Na|| NaQSSE C ||SS was constructed to measure cyclic voltammetry, where SS ∼ stainless steel Na ∼ sodium metal.Cells (CR2032 type button cells) were fabricated in an Ar-filled glove box (model Mbraun, Labstar) where O 2 Electronic Supplementary Material (ESI) for Energy Advances.This journal is © The Royal Society of Chemistry 2024 and H 2 O were kept at ppm.Electrochemical voltage stability was measured using the LSV technique at a scan rate of 5 mV/s.A VMP3 (Bio-Logic) electrochemical analyzer was used.The transfer number (T Na+ ) of the QSSE is measured using a symmetrical Na||NaQSSE C ||Na cell.The electrolytes are sandwiched between two 14 mm diameter Na metal electrodes.
The Na metal acts as the counter and working electrode.The Na-ion transfer number was measured using electrochemical impedance spectroscopy and chronoamperometry with an external DC potential step of V = 20 mV in an electrochemical analyzer (Bio-Logic, model VMP3).All the electrochemical experiments were carried out at room temperature.
To prepare the cathode, carbon-coated Na3V2(PO4)3, acetylene black, and sodium carboxymethyl cellulose (NaCMC) as an aqueous-based binder were mixed in a weight ratio of 70:20:10 in deionized water.A tabletop coating machine was then used to cast the smooth slurry onto an aluminum foil sheet (0.20 mm).These electrodes, as prepared, were dried in a vacuum oven at a temperature of 80 °C for 24 hours to get a loading of 1-1.5 mg/cm 2 (0.117-0.175 mAh/cm 2 ) of NVP.A cycle tester (Arbin BT200; accuracy up to 0.02% for low power and 0.05% for high power applications) was used to charge/discharge Na||NVP cells at different current densities.

Table S1 :
Z fit parameters of Nyquist of Na||NaQSSE C ||NVP cell before and after cycling.