Isothermal Calorimetry Evaluation of Metallurgical Silicon as a Negative Electrode Material for Li-Ion Batteries

Abstract

The structural evolution of Si during lithiation and delithiation is uniquely dependent on the cycling conditions and can show either reversible or path dependent behavior. In this paper, metallurgical Si (large crystalline particles of pure Si) is cycled to exhibit both reversible and path dependent cycling while in-operando calorimetry is performed with a high precision isothermal calorimeter. The enthalpy potential and waste heat are studied in both the reversible and path dependent regimes. The enthalpy of crystallization of Li15Si4 is quantified to be 21 kJ molSi −1. The parasitics (heat of side reactions) of pure Si are studied, showing a stronger current than time dependence. The voltage dependence of the parasitic power is quantified, showing increasing parasitics below 170 mV. The results of this in depth calorimetric study of metallurgical Si provides valuable insights into the heat production and energy efficiency of Si as a negative electrode material in Li-ion batteries.