Biomolecular-derived conformal carbon coating engineering ultrastable silicon oxide anodes for lithium-ion batteries

Silicon oxide (SiO) possesses a high theoretical capacity (2680 mAh g −1 ) yet suffers low conductivity (≈6.7 × 10 −4  S·cm −1 ) and pronounced volume expansion (≈200%). Herein, we report a biomolecular-derived carbon coating strategy that simultaneously addresses the intrinsic limitations of SiO anodes. The abundant carboxyl ( COOH) and phenolic-OH groups in humic acid (HA) form strong covalent bonds with SiO particles, constructing a conductive carbonaceous network that dual-functionally suppresses volume expansion through mechanical confinement and enhances electron transport pathways. The HA-derived carbon shell expedites the formation of LiF-rich SEI film via in-situ reduction, reducing interfacial side reactions. Consequently, the SiO@HAC composite demonstrates a high initial coulombic efficiency (ICE) of 83%, exceptional cycling stability (860 mAh g −1 capacity retention after 600 cycles at 500 mA g −1 ), and superior rate performance. When paired with NCM811 cathode, the full battery achieves a reversible capacity of 141 mAh g −1 at 100 mA g −1 , with a capacity retention of 82% after 200 cycles. These findings highlight the strategic advantages of HA-derived carbon shells in advancing high-loading silicon-based anodes toward practical applications in lithium-ion batteries (LIBs).