Influence of Oxygen Content on the Structural Evolution of SiOx Thin-Film Electrodes with Subsequent Lithiation/Delithiation Cycles

SiOx negative electrodes for Li-ion batteries enable high energy density while providing better structural integrity compared to pure Si electrodes. The oxygen content has a critical impact on structural changes that occur during electrochemical cycling. In this study, the near-surface structural evolution in SiOx thin films with different compositions (0.3 <= x <= 2) was probed by various electrochemical techniques and X-ray photoelectron spectroscopy. These results show that all of the SiOx films undergo significant chemical changes during cycling. Even the films with high oxygen content (x = 2) undergo significant restructuring after sufficiently long cycling times. The changes that occur in all films indicate that the near-surface regions of SiOx materials react in ways that effectively make them part of the solid electrolyte interphase (SEI). This also implies that tuning the surface oxygen content of Si-based electrodes can be used to control SEI performance. Hence, the structural changes in SiOx observed in this study may provide useful guidelines for designing passivating layers for improved cycle efficiency.

Automated summary

SiOx negative electrodes for Li-ion batteries offer high energy density and better structural integrity compared to pure Si electrodes. This study investigates the near-surface structural evolution in SiOx thin films with different compositions and reveals that all the films undergo significant chemical changes during cycling, even those with high oxygen content. The results suggest that the near-surface regions of SiOx materials become part of the solid electrolyte interphase and tuning the surface oxygen content can be used to control its performance. The observed structural changes in SiOx may guide the design of passivating layers for improved cycle efficiency.