Effect of reduction temperature on the crystallinity and electrochemical behavior of sol-gel-derived SiO2 for lithium-ion battery applications

초록

Silicon suboxides (SiOx, 0 < x < 2) have emerged as promising anode materials for lithium-ion batteries (LIBs) due to their improved structural stability compared to pure silicon. In this study, spherical SiO2 powders were synthesized via a sol-gel method and subsequently reduced to SiOx through magnesiothermic reduction reaction (MRR) at various temperatures to achieve controlled crystallinity. Structural analyses revealed a gradual transformation from amorphous silica to partially crystalline silicon domains with increasing reduction temperature. These temperature-dependent changes in crystallinity significantly affected the electrochemical performance of the SiOx/graphite composites. Specifically, the initial discharge capacity increased from 336.1 to 567.3 mAh/g as the reduction temperature increased from 700 to 850 degrees C, owing to the formation of electrochemically active crystalline Si. However, the higher crystallinity also led to accelerated capacity fading due to structural degradation caused by repeated volume changes during cycling. This study systematically demonstrates that how MRR temperature-dependent reduction governs the structural crystallinity of Si-based anodes and modulates the trade-off between initial capacity and cycling stability, providing valuable insights for the developments of high -performance Si-based anode materials.

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