Strategies Toward the Production of Nanoporous SiOx/C Anodes from the Sustainable Diatom‐SiO2 for Li‐Ion Batteries: A Comparative Study of Different Carbon Amounts

Abstract Nanostructured SiO x /C composites are promising candidates for high energy density anodes with extended lifespan in next‐generation Li‐ion batteries (LIBs). However, integrating sustainable precursors for the synthesis of high performance SiO x /C negative electrodesremains a key challenge. In this study, nanoporous SiO 2 derived from the shells of industrially cultured diatom microalgae is successfully used as a template for synthesizing SiO x via the magnesiothermic reduction reaction (MgTR), while the effectiveness of different carbon coating (CC) strategies to produce diatom‐ SiO x /C from glucose as carbon precursor is thoroughly analyzed. Notably, the original nanostructure of the diatom‐ SiO 2 frustule is preserved throughout the synthesis process, and it is demonstrated that increasing the heating ramp during MgTR enhances the Si yield, leading to a significant increase in specific capacity of the anodes from 1064 mAh.g −1 (2 °C/min −1 ) to 1846 mAh.g −1 (20 °C/min −1 ). A comparative analysis of three synthesis pathways for producing diatom‐ SiO x /C composites: 1) MgTR of diatom‐ SiO 2 followed by CC, 2) CC of diatom‐ SiO 2 followed by MgTR, and 3) simultaneous reduction of diatom‐ SiO 2 and glucose precursor, revealed that pathway (1) is most effective for producing highcapacity diatom‐ SiO x /C anodes. These findings provide key enablers for developing sustainable SiO x /C anodes of superior electrochemical performance.