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In this work, silicon (Si) particles were successfully transformed to core–shell structured Si@SiOx (0 < x ≤ 2) particles via wet oxidation under high-pressure conditions. In order to obtain Si particles with different oxygen content, the SiOx-shell was generated in a sealed Teflon-lined autoclave at 150 °C for different time. As a result, the Si@SiOx particles sample with oxygen mass fraction of 2.37% (Si@SiOx-2.37%) presents the best cycling stability. The discharge specific capacity of the Si@SiOx-2.37% sample is up to 1701 mAh g−1 after 100 cycles at 0.1 C (1 C = 4.2 A g−1), which is 1068 mAh g−1 higher than that of the original Si particles sample with natural oxygen mass fraction of 0.98% (Si@SiOx-0.98%). Besides, the Si@SiOx-2.37% sample presents slightly better rate performance than others. The discharge specific capacity of the Si@SiOx-2.37% sample is 713 mAh g−1 at 2 C, but that of the Si@SiOx-0.98% sample is close to 0. As the rate is restored to 0.1 C, the Si@SiOx-2.37% sample exhibits faster recovery of capacity than others. Furthermore, when the oxygen content continues to rise, the rate and cycle performance gradually deteriorate. [ABSTRACT FROM AUTHOR]