Preparation, electrical properties, ab initio calculations and sodium motion in NaNi2As3O10 crystal structure

Benefiting from their structural diversity, high structural and thermal stability, and significant ionic conductivity, polyanionic framework materials are suitable for energy storage applications. This study details the synthesis and characterization of the arsenate compound NaNi 2 As 3 O 10 . The material was synthesized as polycrystalline powder by the citrate-nitrate combustion method and the crystal structure was determined using Rietveld analysis and confirmed by means of ab initio calculations. This phase crystallizes in the triclinic system with space group P 1 ̅ [a=6.69172 (5) Å; b=7.74930 (6) Å; c = 8.71357 (7) Å; α =108.6343 (6)°, β = 108.5190 (6)° and γ= 99.2169 (6)°]. Its crystal structure, which is isotypic to NaCo 2 As 3 O 10 , presents an open 3D framework that provides wide tunnels for Na + hopping. Electrochemical Impedance Spectroscopy (EIS) and the bond valence site energy (BVSE) were used to investigate the electrical properties and the Na + migration respectively. The overall conductivity of the sample reaches 4.58 ×10 −5 S.cm −1 at 575 °C. The crystal structure enables 1D migration pathways of sodium ions within the NaNi 2 As 3 O 10 network with a computed energy barrier of 1.11 eV. Compared to Na-ion conducting arsenates and other extensively studied polyanionic materials, NaNi 2 As 3 O 10 presents an intermediate ionic conductivity. Impedance Nyquist plot and calculated electronic localization function (ELF) isosurfaces (set at 0.65) of NaNi 2 As 3 O 10 . • Crystal structure of new NaNi2As3O10 determined by Rietveld method and validated by ab initio calculations. • The electrical properties of NaNi2As3O10 were investigated by Impedance Spectroscopy (EIS). • A study reveals a 1D migration channel of Na+ within the crystal structure.