Crystal structure, phase relations and electrochemical properties of monoclinic Li2MnSiO4

Phase relations in the MnO–SiO2–Li4SiO4 subsystem have been investigated by X-ray diffraction after solid-state reactions in hydrogen at 950–1150 °C. Both cation-deficient and cation-excess solid solutions Li2+2xMn1−xSiO4 (−0.2⩽x⩽0.2) based on Li2MnSiO4 have been found. According to Rietveld analysis, Li2MnSiO4 (monoclinic, P21/n, a=6.3368(1), b=10.9146(2), c=5.0730(1) Å, β=90.987(1)°) is isostructural with γII-Li2ZnSiO4 and low-temperature Li2MgSiO4. All components are in tetrahedral environment, (MnSiO4)2− framework is built of four-, six- and eight-member rings of tetrahedra. Testing Li2MnSiO4 in an electrochemical cell showed that only 4% Li could be extracted between 3.5 and 5 V against Li metal. These results are discussed in comparison with those for recently reported orthorhombic layered Li2MnSiO4 and other tetrahedral Li2MXO4 phases.

Arrangement of Mn (large white balls) and Si (small grey balls) atoms in Li2MnSiO4 structure. Bold lines connect atoms linked via common oxygen (not shown).Figure optionsDownload as PowerPoint slide