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

The 150 °C isothermal section of Li-Si-Ni ternary system has been experimentally established. The investigation is based on X-ray powder diffraction and scanning electron microscopy techniques on about 80 ternary alloys, prepared by argon-arc melting of proper elemental ingots. The existence of six ternary compounds, i.e. τ1(LiNi2Si), τ2(Li13Ni40Si31), τ3(LiNi6Si6), τ4(Li13Ni9Si18), τ5(Li0.6Ni5.4Si6) and τ6 (Li75Ni20Si128) is conformed. Fourteen three-phase regions have been detected, i.e. Li13Si4+τ1+Li22Si5, Li13Si4+τ1+τ2, γ+τ1+τ2, Li7Si3+τ4+τ2, Li7Si3+τ4+Li12Si7, τ6+τ4+Li12Si7, γ+τ1 +β1, γ+δ+τ2, τ3+δ+τ5, ε+δ+τ5, NiSi2+(Si)+τ5, (Si)+τ5+τ4, τ2+τ3+τ4 and τ5+NiSi+NiSi2. Furthermore, thermodynamic description of the Li-Ni and Li-Si-Ni systems is carried out with the CALPHAD approach on the basis of the present experimental results and the first-principle calculation of the formation enthalpies for τ1 and τ3 ternary compounds. Reasonable agreement of the phase equilibria in the Li-Si-Ni ternary system between the experiment and thermodynamic calculation is achieved.