The hydrothermal synthesis, crystal structure and electrochemical properties of MnSb2O4

Abstract

Phase pure polycrystalline MnSb₂O₄ was synthesised under hydrothermal conditions. Impurities formed outside a narrow range of pH and metal stoichiometric ratios. The structure and its temperature dependence was studied based on multi-temperature conventional single crystal X-ray diffraction (SC-XRD) and high resolution synchrotron powder X-ray diffraction (PXRD). At low temperature (100–300 K) the lattice parameters expanded linearly with thermal expansion coefficients of α_{a,300 K} = 8(1) × 10⁻⁶ K⁻¹ and α_{c,300 K} = 7.2(2) × 10⁻⁶ K⁻¹. At high temperature an irreversible annealing effect was observed. Modelling the atomic displacement parameters based on the single crystal X-ray diffraction data gives a Debye temperature of 267(3) K for MnSb₂O₄. When heated in an oxygen-rich atmosphere MnSb₂O₄ oxidises above 800 K and it decomposes at 975 K under inert conditions. Electrochemical measurements displayed similar behaviour to the isostructural CoSb₂O₄, with reversible alloying–dealloying of Li_xSb after the first cycle with a reversible capacity of 337 mAh g⁻¹ at the 2^nd cycle, which degraded to c. 100 mAh g⁻¹ after 30 cycles.