Lithium selenometallates of triel elements, Li5MSe4 (M = Al and Ga), aliovalent doping and their ionic conductivity. Issue 46 (9th November 2022)

• Record Type: Journal Article
• Authors: Sundaramoorthy, Santhoshkumar; Chernatynskiy, Aleksandr V.; Gerasimchuk, Nikolay; Choudhury, Amitava
• Is Part Of: Dalton transactions. Volume 51:Issue 46(2022)
• Page Start: 17772
• Page End: 17779
• Publication Date: 2022-11-09
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/d2dt02843c
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : Lithium selenometallates of Al and Ga have been synthesized. The Li-ion conductivity increases by almost five times upon Sn doping. Abstract : Ternary selenometallates, Li5 MSe4 (M = Al(I ) and Ga(II )), have been synthesized for the first time through high temperature solid-state reactions combining elements and Li2 Se in stoichiometric compositions. Li5 MSe4 crystallizes in the P 21 / m space group, forming a pseudo-2D layer type structure with edge sharing LiSe4 and MSe4 tetrahedra along the a -axis. These layers are interleaved by octahedrally coordinated Li ions located in the interlayer space. AC impedance spectroscopy measurements yield room temperature ionic conductivities of 0.60 × 10 −7 and 0.58 × 10 −7 S cm −1 with calculated activation energies of 0.51 and 0.48 eV for I and II, respectively. An aliovalent substitution of Sn 4+ in Li5 MSe4 yields compositions of Li4.66 Al0.82 Sn0.22 Se4 (III ) and Li4.37 Ga0.89 Sn0.24 Se4 (IV ), which crystallize in the P 21 / m and P 3̄ m 1 space groups, respectively. Sn-doped samples show an ∼5-fold increase in ionic conductivity, 3.37 × 10 −7 S cm −1 and 2.4 × 10 −7 S cm −1 with activation energies of 0.54 and 0.28 eV, respectively, for III and IV . The optical band gap values of the compounds are 3.65 and 3.2 eV for I and II, respectively, as measured by diffuse reflectance spectroscopy. Density functional theory (DFT) calculations predicted a major contribution from the Se 4p-states in forming the top of the valence band and strongly hybridized the Se 4p and n s orbitals of Al and Ga in forming the bottom of the conduction band with almost no contribution from the Li s-states near the Fermi level indicating their ionic interactions with the ligand.