Investigation of sulphate hydride anti-perovskite as solid electrolyte

International audienceOver the last decade, anti-perovskites have drawn significant attention as potential solid-electrolytes for solid-state batteries. Due to the increase in consumption of lithium, there has been a push towards next generation batteries, including sodium-ion batteries. The first representative of the material class of sulphate hydride anti-perovskites, Na3SO4H, was synthesized by solid-state methods as a possible electrolyte for sodium solid-state batteries. Structural characterization confirms the results reported in literature with P4/nmm space group Thermal measurements (DSC and TGA) reveal the stability of the material up to 633 K with H2 release beginning shortly after. Here were report the first electrochemical measurements of this new sulphate hydride anti-perovskite with room temperature conductivity of 4.0 × 10−7 S/cm. Similarly, the electronic conductivity was also measured by Direct Current (DC) experiments to understand a non-linear Arrhenius plot of the conductivity. From the EIS and DC measurements, it is suggested that the electronic and ionic conductivities of this material fall in the same range at room temperature. Upon heating, the material becomes a mainly ionic conductor, explaining the change in the activation energy values in the Arrhenius plot (0.83 eV at low T and 0.24 eV at high T). Solid-state NMR hints at defects in the structure that correspond to Na1 and Hb-c-d dynamics

Synthesis, structural, and transport properties of novel bihydrated fluorosulphates NaMSO4F 2H2O (M=Fe, Co, and Ni)

3d-metal fluorosulphates that have a tavorite-type structure (e.g., LiFeSO4F) were recently reported as attractive positive electrode candidates for future Li-ion batteries aimed at large volume markets. These new fluorosulphates had to be synthesized via ionothermal synthesis owing to both their thermal instability at temperatures greater than 300 °C and their water solubility. In an attempt to depart from ionothermal synthesis, low-temperature solid-state reactions and solvothermal processes were successfully tried.The latter technique,which is reported herein, proceedswithwater as the solvent and has led to a new family of fluorosulphatesNaMSO4F3 2H2Othat crystallize in amonoclinic unit cell (SG=P21/m) similar to the uklonskovite-type structure earlier proposed for NaMgSO4F3 2H2O. These new phases show no electrochemical activity with either Li or Na metal and have room temperature ionic conductivities on the order of 1 × 10-9 S cm-1. Additionally, we have discovered the feasibility, upon controlled dehydration of the NaMSO4F.2H2O phases, to prepare NaMSO4F phases adopting a derived tavoritetype structure and displaying ionic conductivities around 10-7 S cm-1. Finally, this finding opens the possibility to achieve Li-based fluorosulphates via two-step synthetic pathways. © 2010 American Chemical Society