This research aims to explore the impact of varying content of silicon oxide (SiOx) on the performance and aging process of lithium-ion cells. Extensive investigations were conducted, including the analysis of charge and discharge curves, changes in thickness, degradation of the electrolyte, gas evolution, and chemical analysis of cells with different proportions of silicon oxide in the anode and their corresponding cathodes.

The results of the study indicate that a higher silicon oxide content in the anode leads to an increased voltage hysteresis between the charge and discharge processes. Furthermore, it was observed that the first-cycle efficiencies decrease as the silicon oxide content increases. This decrease can be attributed to the irreversible formation of LixSiy and the subsequent loss of active lithium from the cathode during the formation process. The anodes also experience greater thickness changes with higher silicon oxide content, and specific peaks in the differential voltage curves can be linked to certain active materials in the anode and their corresponding thickness changes. Gas analysis revealed the presence of conductive salt, electrolyte intermediates, and silicon-containing gaseous fragments, indicating continuous decomposition of the electrolyte and aging of the silicon oxide. Chemical analysis further confirmed the presence of increased silicon-derived products and degradation of the electrolyte on the electrode surfaces.

These findings highlight the significance of conducting a comprehensive investigation into the aging process and provide valuable insights into the complex chemical changes occurring in electrode materials. This knowledge can contribute to the design of more efficient and durable lithium-ion cells.

Parts of the presented work were funded by the joint project OsabanPlus (03XP0469C) within the German–Japanese cooperation program of BMBF (Federal Ministry for Education and Research) and NEDO (New Energy and Industrial Technology Development Organization).