Evaluating Electrolyte-Anode Interface Stability in Sodium All-Solid-State Batteries.

All-solid-state batteries have recently gained considerable attention due to their potential improvements in safety, energy density, and cycle-life compared to conventional liquid electrolyte batteries. Sodium all-solid-state batteries also offer the potential to eliminate costly materials containing lithium, nickel, and cobalt, making them ideal for emerging grid energy storage applications. However, significant work is required to understand the persisting limitations and long-term cyclability of Na all-solid-state-based batteries.

Investigating the abnormal conductivity behaviour of divalent cations in low dielectric constant tetraglyme-based electrolytes.

Solutions made of tetraglyme (G4) containing Ca(TFSI) have been studied as models to understand the solvation structure and the conductivity properties of multivalent ions in low dielectric constant ethereal electrolytes. These solutions have been characterised using electrochemical impedance spectroscopy, rheological measurement, and Raman spectroscopy. The ionic conductivity of these electrolytes shows an intriguing non-monotonic behaviour with temperature which deviates from the semi-empirical Vogel-Tammann-Fulcher equation at a critical temperature.

Ionothermal Synthesis of Polyanionic Electrode Material NaV(PO)FO through a Topotactic Reaction.

Polyanionic NaV(PO)FO has been successfully prepared for the first time by ionothermal reaction in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM TFSI) ionic liquid. Its structure and elemental stoichiometry are confirmed by X-ray diffraction, NMR spectroscopy, and ICP-OES, respectively. Furthermore, the scanning electron microscopy reveals that the as-obtained material possesses an original platelet-like morphology.

Monitoring the Crystal Structure and the Electrochemical Properties of Na(VO)(PO)F through Fe Substitution.

We here present the synthesis of a new material, Na(VO)Fe(PO)F, by the sol-gel method. Its atomic and electronic structural descriptions are determined by a combination of several diffraction and spectroscopy techniques such as synchrotron X-ray powder diffraction and synchrotron X-ray absorption spectroscopy at V and Fe K edges, Fe Mössbauer, and P solid-state nuclear magnetic resonance spectroscopy. The crystal structure of this newly obtained phase is similar to that of Na(VO)(PO)F, with a random distribution of Fe ions over vanadium sites.

Aluminum substitution for vanadium in the NaV(PO)F and NaV(PO)FO type materials.

Among the positive electrode materials for Na-ion batteries, Na3V2(PO4)2F3 is considered as one of the most promising and generates high interest. Here, we study the influence of the sol-gel synthesis parameters on the structure and on the electrochemical signature of the partially substituted Na3V2-zAlz(PO4)2(F,O)3 materials. We demonstrate that the acidity of the starting solution influences the vanadium oxidation state of the final product.