Synthesis, crystal structure and magnetic properties of a new lithium cobalt metaphosphate, LiCo(PO3)3

A new lithium cobalt metaphosphate, LiCo(PO3)3, is reported for the first time, which was discovered during the exploratory synthesis in Li-Co-P-O system by solid state reaction. The structure has been refined by powder X-ray Rietveld refinement method (P212121, a = 8.5398(2) Å, b = 8.6326(2) Å and c = 8.3520(2) Å, Z = 4, Rp = 13.6%, Rwp = 19.4%, Rexp = 17.7%, S = 1.11, χ2 = 1.23). It is isostructural with LiM(PO3)3 (M = Fe, Cu). It contains (PO3)1− chains with the Co atoms localized in the octahedral sites, bridging four neighboring chains. The magnetic susceptibility measurement showed a typical paramagnetic behavior of high spin of Co2+, following the Curie-Weiss law in the temperature range of 5-300 K. Unlike the olivine type lithium cobalt phosphate, LiCoPO4, cyclic voltammetry of LiCo(PO3)3 assembled in the coin-type cell showed no electrochemical activity in the voltage region of 1-5 V versus Li/Li+.