Synthesis, electrical and dielectrical properties of (LixNa1–x)6Mg(SO4)4 vanthoffite ceramics as new attractive electrode materials for Li- and Na-ion batteries

Highlights: • (Li_xNa_1−x)₆Mg(SO₄)₄ vanthoffite powders ceramics were obtained at high temperature by the solid state method. • Characterization techniques confirmed a good crystallinity of the obtained phases. • The materials crystallized in the simple monoclinic system with space group P2₁/c. • The obtained materials present a semi ionic conductor in the [553–733 K] temperature range temperature. • Conduction within these materials is 1D and made by migration of cations mobile in the lattice system. - Abstract: (Li_xNa_1−x)₆Mg(SO₄)₄ ceramics denoted as LNMSx (x = 0.1, 0.3, 0.5, 0.7 and 1 mol%) were obtained via the solid state reaction method. The refinement of the structural parameters using the Fullprof software by the Rietveld method confirmed that the Li⁺ dopant can replace the sodium in this structure with a slight increase in the lattice parameters. The spectroscopic studies revealed the vibrational mode of the sulfate groups. Electrical conductivity, activation energies, modulus and dielectric properties were studied by impedance spectroscopy in the [553–733 K] temperature range. Results show that the materials present a semiconductor ionic character with 1D conduction by means of migration of cation mobile in the system. Conductivity decreases when the Li⁺ dopant content x increases. The electrochemical studies show that LNMSx (x = 0.5) has the highest electrical conductivity that can be proposed as a good electrolyte material for lithium or sodium batteries applications.