Key experiments and challenging thermodynamic modeling of the Li-Si-C system

Abstract The phase equilibria and thermodynamic properties of the ternary Li-Si-C system are crucial for developing new anode materials containing Si and/or C for Li-ion batteries. We carried out the long time annealing experiments and confirmed the key three-phase equilibrium of βLi 2 C 2 +SiC + Li 7 Si 3 at 630 °C–650 °C. A consistent thermodynamic description of the Li-Si-C ternary system has been constructed based on the recently published Li-Si system, and the Li-C and Si-C binary systems that we revised in this work. The revision requires a more negative Gibbs energy for the αLi 2 C 2 and βLi 2 C 2 phases in the Li-C system, and a more positive Gibbs energy for the SiC phase in the Si-C system. The more negative Gibbs energy of the βLi 2 C 2 phase requires an associate solution model to be introduced for the liquid phase. Calculated partial pressures from the revised thermodynamic description of the Li-C binary system show better agreement with the experimental data. The calculated phase diagram sections of the Li-Si-C ternary system are not only in good agreement with the key annealing experiment results, but also with differential scanning calorimetry results.