Effect of current rate on the formation of the solid electrolyte interphase layer at the graphite anode in lithium-ion batteries

The solid electrolyte interphase (SEI) layer plays a crucial role in ensuring the safety and stability of batteries. The SEI layer is highly complex and it comprises organic and inorganic components due to the electrolyte decomposition and electrode dissolution. In this study, SEI layers were formed at various current rates using a full cell, and their chemical and electrochemical properties were investigated. SEIs formed at various current rates consisted of similar constituents; however, the composition of the constituents differed according to the current rate, indicating the effect of current rate on the SEI formation kinetics. The differential scanning calorimetry (DSC) thermograms showed that the SEI formed at a low current rate included a larger portion of components that decomposed at ∼100 °C than those formed at high current rates. In addition, in-depth X-ray photoelectron spectroscopy (XPS) also revealed this difference in composition according to the varying current rate. The anode cycled at a low current rate displayed a low charge transfer resistance. This study suggests that the physicochemical and electrochemical properties of SEIs differ depending on the formation conditions.