Synthesis, Crystal Structures, and Thermal Analyses of Two New Antimony Tellurite Sulfates: [Sb2(TeO4)](SO4) and [Sb2(TeO3)2](SO4)

Two new antimony (III) tellurite sulfates [Sb 2 (TeO 4 )](SO 4 ) ( 1 ) and [Sb 2 (TeO 3 ) 2 ](SO 4 ) ( 2 ) were successfully synthesized through a conventional hydrothermal method and their crystal structures were determined by X-ray single crystal analysis. [Sb 2 (TeO 4 )](SO 4 ) crystallizes in the triclinic space group P ī (No. 2) with lattice parameters a=5.572(2), b=7.247(2), c=9.540(3) Å, V=358.5(2) Å 3 , and Z=2, while [Sb 2 (TeO 3 ) 2 ](SO 4 ) crystallizes in the orthorhombic space group Pbca (No. 61) with lattice parameters a=7.368(2), b=14.571(3), c=16.521(3) Å, V=1773.7(6) Å 3 , and Z=8. The structure of [Sb 2 (TeO 4 )](SO 4 ) features a three-dimensional framework, composed of [SbO 4 ] trigonal bipyramids and [TeO 4 ] polyhedra to form a cationic 2 ∞[Sb 2 (TeO 4 )] 2+ corrugated cationic layers along [100], linked by SO 4 2− anions. [Sb 2 (TeO 3 ) 2 ](SO 4 ) forms a three-dimensional framework consisting of two dimensional wrinkled layers of 2 ∞[Sb 2 (TeO 3 ) 2 ] 2+ that are linked by SO 4 2− anions. The band gaps of 4.16 eV and 3.72 eV for [Sb 2 (TeO 4 )](SO 4 ) and [Sb 2 (TeO 3 ) 2 ](SO 4 ) respectively are estimated from the solid state UV-vis-NIR diffuse reflectance spectra. Thermal analysis indicated that both compounds are thermally stable up to about 500 °C. The electrochemical specific capacity of [Sb 2 (TeO 4 )](SO 4 ) was determined to 245 mA h g −1 on the first cycle in a Li-ion half-cell, the capacity remains at about 106 mA h g −1 after 500 cycles.