Effect of pre-lithiation amounts on the performance of LiNi0.8Co0.1Mn0.1O2||SiOx/Graphite pouch cell

Abstract

Pre-lithiation technology is essential to improve the initial coulombic efficiency (ICE) and cycling stability of high SiOx content cells. Different amounts of pre-lithiation significantly affect the electrochemical performance of cells. In this study, three groups of LiNi0.8Co0.1Mn0.1O2 || SiOx/Graphite pouch cells (SiOx, 45 wt%) with different pre-lithiation amounts are fabricated using an electrochemical pre-lithium method. The effects of pre-lithiation amounts on the capacity and cycling stability are comprehensively investigated by non-destructive tests and post-mortem analysis. The results show that increasing the amounts of pre-lithiation can substantially improve the capacity of the cells, but may also accelerate their aging. Further studies reveal that the cycling stability of SiOx/Graphite anode is strongly affected by the amounts of pre-lithiation, whereas the effect on the cathode is negligible. Moreover, titration gas chromatography (TGC) experiments are used to quantify the lithium loss in SiOx/Graphite anode. The accelerated formation of SEI and trapped lithiated active materials as well as lithium dendrites caused by over-lithiation at SiOx/Graphite anode are responsible for the rapid degradation of pouch cells with high pre-lithiation amounts. This work demonstrates the complex relationship between pre-lithiation amounts and electrochemical performance, which needs to be carefully measured in SiOx-based cells.