Influence of Salt Anions on the Reactivity of Polymer Electrolytes in All-Solid-State Sodium Batteries

Abstract

Solid-state batteries have received renewed attention in recent years. The present study compares all-solid-state sodium batteries containing polyethylene oxide (PEO) polymer electrolyte (PE) with two salts, NaPF6 and NaClO4. Electrochemical properties were determined by means of both AC and DC measurements. Battery prototypes with PEO:NaClO4 have a better specific capacity; however, a composite electrolyte system containing TiO2 nanoparticles shows greater influence in PEO:NaPF6. This is probably due to the titania particles acting as a scavenger of HF, an inevitable contaminant in electrolyte systems containing PF6- anions.

A Novel Approach for Post-Mortem Analysis in All-Solid-State Batteries: Isolating Solid Polymer Electrolytes from Lithium Anodes

“…In this case, the initial point of intersection with the x-axis, the bulk resistance shows the same value before and after cycling, which indicates a constant resistance for the bulk SPE. 49 However, in the middle-high frequency range, the arc is not symmetric, which can be explained by a superposition of the resistance of a surface film (which forms at the Li-SPE interface) and the charge transfer process (i.e., Li → Li + + e − ). 15 Overall, the cell's interface resistance was seen to increase after cycling, most likely due to surface film formation.…”

The Effect of Titania Additives on the Performance of PEO-Based Solid Sodium Batteries: Bulk and Interfacial Aspects

“…These results are consistent with previous reports. 1 Figure 3b shows impedance spectra of Na//Na cells with a reference polymeric matrix (no additives) and with TiO 2 NTs, presented as Nyquist plots. The spectra include three important features: the value (resistance) of the intercept of the first high frequency semicircle with the z' axis (at the highest frequency, left) reflecting the bulk matrix resistance, the high frequency big semicircle reflecting the interfacial cell impedance (related to Na ion transport across the matrix/Na anode interface), and the medium-low frequency that can be assigned to charge transfer activity related to the Na + /Na redox couple.…”

“…Most interesting and studied solid polymer electrolytes (SPEs) for battery applications comprise polymeric matrices with mobile charge carriers such as lithium or sodium ions and anions such as PF 6 − , TFSI − and ClO 4 − . [1][2][3] These matrices may maintain simultaneously two conductive phases at room temperature-crystalline and amorphous. To reach a sustainable conductivity the temperature must be raised above T m of the polymer, usually >60 °C.…”

Wide-temperature-range sodium-metal batteries: from fundamentals and obstacles to optimization

“…276,277 Recently, some ingenious designs have been developed to solve these issues. 278,279 For example, a fluorinated polymer, poly(2,2,2-trifluoroethyl methacrylate), was induced into PEO-based electrolyte to improve the stability of the electrochemical window and migration number. 280 A fluorinerich macromolecule-containing all-solid-state polymer electrolyte (FMC-ASPE) was formed by supramolecular self-assembly between 21-b-CD-g-PTFEMA and PEO, which effectively minimizes the generation of side reactions and inhibits the growth of sodium dendrites.…”