Experimental investigation and thermodynamic description of the Li-Si-Mn ternary system

The 150 °C isothermal section of Li-Si-Mn ternary system has been investigated experimentally and extrapolated using the optimized thermodynamic parameters from the constitutive binary systems. About 30 ternary alloys were examined by means of scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) and X-ray diffraction (XRD). Nine three-phase regions have been detected, i.e. Li12Si7+Mn11Si19+(Si), Li12Si7+MnSi+Mn11Si19, Li7Si3+Mn5Si3+MnSi, Li7Si3+Mn5Si3+Li13Si4, Li22Si5+Mn5Si3+Mn3Si, Li22Si5+Mn3Si+Mn9Si2, Li22Si5+Mn9Si2+Mn6Si, Li22Si5+Mn6Si+(Li) and (Li)+(αMn)+Mn6Si. No ternary compound has been observed for this ternary system. Furthermore, thermodynamic assessment of Li-Mn binary system has been carried out with the CALPHAD approach on the basis of the experimental data. And the thermodynamic parameters of the Si-Mn system from literature have been revised. The compounds MnSi1.75-x and MnSi were simply modeled by the sublattice models as (Mn)11(Si)19 and (Mn)1(Si)1 respectively to adapt to the multicomponent system. Thermodynamic extrapolation of the Li-Si-Mn ternary system showed good agreement with the experimental phase relationships.