Development of sodium-conducting polymer electrolytes: comparison between film-casting and films obtained via green processes

Abstract

Sodium-conducting solvent-free polymer electrolytes based on commercially available and inexpensive materials poly(oxyethylene), POE, and three different sodium salts (NaI, NaCF 3 SO 3 and NaClO 4 ) were prepared and exhaustively characterized. In order to minimize the environmental impact related to conventional film processing based on casting, a combination of lyophilization and hot-pressing was successfully applied. Contrary to film-casting, this new approach led to very homogeneous and pore-free films. This study suggests the obtained polymer electrolyte films as a promising route to enhance not only ionic conductivity but also mechanical properties. Furthermore, a preliminary work on salt blends hosted by POE shows that they strongly decrease melting point and crystallinity of the polymer electrolytes and paves the way for enhanced sodium-conducting materials.

Thermal Properties of Composite Polymer Electrolytes Poly(Ethylene Oxide)/Sodium Trifluoroacetate/Aluminum Oxide (PEO)10CF3COONa + x wt.% Al2O3

“…The DSC thermogram corresponding to the CF 3 COONa salt is shown in Figure 1b; on it, an endothermic anomaly about 480 K can be observed, due to salt melting. Figure 1c shows DSC results for the solid polymer electrolyte (PEO) 10 CF 3 COONa; this thermogram shows two endothermic anomalies: One about 334 K, usual in this type of membrane and that corresponds to the PEO crystalline phase melting [15,16,17]. The other endothermic anomaly is observed about 387 K and corresponds to the melting point of a new crystalline phase of a complex formed by the combination of polymer and salt [18].…”

A Sodium‐Ion Battery with a Low‐Cost Cross‐Linked Gel‐Polymer Electrolyte

“…The hard and brittle ceramic or glass electrolytes have been proposed to address the safety issues, but the solid–solid electrode–electrolyte interfaces may not sustain a long cycle life . The solid‐polymer electrolytes, typically based on poly(ethylene oxide) (PEO), have also been extensively explored, but they exhibit too low an ionic conductivity at room temperature (≈10 −5 S cm −1 ) and poor resistance to oxidation at relatively high voltage . On the other hand, the gel‐polymer electrolytes, taking advantages of the polymer flexibility and the high ionic conductivity of the liquid electrolytes, employ a variety of polymers as the scaffold to immobilize the liquid electrolytes, such as poly(vinylidene fluoride) (PVDF), poly(vinylidene fluoride‐hexafluoropropylene) (PVDF‐HFP), poly(acrylonitrile) (PAN), PEO, and PMMA .…”

“…[ 18,19 ] The solid-polymer electrolytes, typically based on poly(ethylene oxide) (PEO), have also been extensively explored, but they exhibit too low an ionic conductivity at room temperature (≈10 −5 S cm −1 ) and poor resistance to oxidation at relatively high voltage. [20][21][22][23] On the other hand, the gel-polymer electrolytes, taking advantages of the polymer fl exibility and the high ionic conductivity of the liquid electrolytes,The design of a sodium-ion rechargeable battery with an antimony anode, a Na 3 V 2 (PO 4 ) 3 cathode, and a low-cost composite gel-polymer electrolyte based on cross-linked poly(methyl methacrylate) is reported. The application of an antimony anode, on replacement of the sodium metal that is commonly used in sodium-ion half-cells, reduces signifi cantly the interfacial resistance and charge transfer resistance of a sodium-ion battery, which enables a smaller polarization for a sodium-ion full-cell Sb/Na 3 V 2 (PO 4 ) 3 running at relatively high charge and discharge rates.…”

“…[ 18,19 ] The solid-polymer electrolytes, typically based on poly(ethylene oxide) (PEO), have also been extensively explored, but they exhibit too low an ionic conductivity at room temperature (≈10 −5 S cm −1 ) and poor resistance to oxidation at relatively high voltage. [20][21][22][23] On the other hand, the gel-polymer electrolytes, taking advantages of the polymer fl exibility and the high ionic conductivity of the liquid electrolytes,…”

Fluorine-free electrolytes for all-solid sodium-ion batteries based on percyano-substituted organic salts

“…Nonetheless, continued interest in such technologies stems from their processing ability and flexibility, higher safety due to the absence of flammable organic solvents and high dimensional stability45678910111213. Despite not being fluid in a wide temperature range, polyethers were first shown to dissolve inorganic salts and conduct resulting ions at room temperature in the 1970s14.…”