PNNL

Abstract

The role of iron sulfide (FeS) in initial cell activation and degradation in the Na-NiCl2 battery was investigated in this work. The research focused on identifying the effects of the FeS level on the electrochemical performance and morphological changes in the cathode. The x-ray photoelectron spectroscopy study along with battery tests revealed that FeS plays a critical role in initial battery activation by removing passivation layers on Ni particles. It was also found that the optimum level of FeS in the cathode resulted in minimum Ni particle growth and improved battery cycling performance. The results of electrochemical characterization indicated that sulfur species generated in situ during initial charging, such as polysulfide and sulfur, are responsible for removing the passivation layer. Consequently, the cells containing elemental sulfur in the cathode exhibited similar electrochemical behavior during initial charging compared to that of the cells containing FeS.