69756 20190709135618.0 doi 10.1039/c7ra04043a sideral 104788 ART-2017-104788 eng Ludwig, J. Direct synthesis and characterization of mixed-valent Li0.5-dCoPO4, a Li-deficient derivative of the Cmcm polymorph of LiCoPO4 2017 Access copy available to the general public Unrestricted While the majority of research activities on LiCoPO4 is focussed on the thermodynamically stable olivine-type Pnma polymorph, the metastable Pna21 and Cmcm modifications have recently attracted considerable attention due to their interesting material properties. In this study, we present the first Li-deficient structural derivative of the Cmcm modification with the nominal composition Li0.5-dCoPO4. As opposed to the substoichiometric olivine (Pnma) phases LixCoPO4 (x = 0; 2/3), which are exclusively accessible by electrochemical or chemical Li extraction techniques, this is also the first time that a direct soft-chemical synthesis route towards a LixCoPO4-type material is accomplished. X-ray and neutron diffraction studies indicate that Cmcm-type Li0.5-dCoPO4 shows vacancies on both the Li and Co sites, whereas X-ray absorption spectra demonstrate that the structure features heterovalent Co ions (+2/+3) to compensate for the Li deficit. Magnetic measurements reveal a long-range antiferromagnetic order below 10.5 K. A thorough investigation of the thermal stability using thermogravimetric analysis, differential scanning calorimetry, and temperature-dependent in situ X-ray powder diffraction demonstrates that Li0.5-dCoPO4 is metastable and exhibits a complex, multi-step thermal decomposition mechanism. In the first step at 394 °C, it decomposes to a-Co2P2O7 (P21/c) and LiCoPO4 (Cmcm) upon O2 release. The LiCoPO4 (Cmcm) intermediate is then irreversibly transformed to olivine-type LiCoPO4 (Pnma) at 686 °C. The material properties of Li0.5-dCoPO4 are further compared to the fully lithiated, isostructural LiCoPO4 (Cmcm) phase, for which an improved structure solution as well as Co L2, 3-edge X-ray absorption spectra are reported for the first time. info:eu-repo/semantics/openAccess by-nc http://creativecommons.org/licenses/by-nc/3.0/es/ 2.936 2017 CHEMISTRY, MULTIDISCIPLINARY 71 / 171 = 0.415 2017 Q2 T2 0.863 2017 Chemistry (miscellaneous) 2017 Q1 Chemical Engineering (miscellaneous) 2017 Q1 info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion Alarcón-Suesca, C. Geprägs, S. Nordlund, D. Doeff, M.M. (orcid)0000-0001-8224-329X Puente Orench, I. Nilges, T. 7, 45 (2017), 28069-28081 RSC ADVANCES RSC Advances 2046-2069 495281 http://zaguan.unizar.es/record/69756/files/texto_completo.pdf Versión publicada 107722 http://zaguan.unizar.es/record/69756/files/texto_completo.jpg?subformat=icon icon Versión publicada oai:zaguan.unizar.es:69756 articulos driver 2019-07-09-12:26:26 ARTICLE