Na2zrcl6 Enabling Highly Stable 3 V All-Solid-State Na-Ion Batteries

Halide solid electrolytes (SEs) are emerging as an alternative to sulfide and/or oxide SEs for applications in all-solid-state batteries owing to the advantage fulfilling high (electro)chemical stability and mechanical sinterability at the same time. Thus far, the developments in halide SEs have focused on Li+ superionic conductors. Herein, the development of a new Na+-conducting halide SE, mechanochemically prepared Na2ZrCl6 (1.8 x 10(-5) S cm(-1) at 30 degrees C) with excellent oxidative electrochemical stability, is described. A trigonal crystal structure with the P3m1 symmetry is successfully identified by the Rietveld refinement of X-ray diffraction. Additionally, the bond valence sum energy level calculations disclose one-dimensional preferable Na+-diffusion channels in Na2ZrCl6. It is to be noted that despite the rather low Na+ conductivity of Na2ZrCl6, NaCrO2 electrodes that uses Na2ZrCl6 in NaCrO2/Na-Sn all-solid-state Na-ion batteries demonstrate an exceptionally high initial Coulombic efficiency of 93.1% and a high reversible capacity of 111 mA h g(-1) at 0.1C and 30 degrees C (98.4% and 123 mA h g-1 at 60 degrees C), highlighting the excellent electrochemical stability of Na2ZrCl6.