Strain-buffered Si-C/oxidized CNT free-standing monolith enabling high-loading, high-performance silicon film anodes

초록

Silicon anodes offer exceptional theoretical capacity but are fundamentally limited in thick-film configurations, where mechanical fracture and electronic disconnection rapidly degrade performance. Overcoming this thickness constraint is essential for high-loading silicon electrodes. Here, a strain-buffered and electronically continuous silicon electrode architecture is introduced that decouples active-layer thickness from electrochemical degradation, enabling thick silicon films to perform comparably to conventional thin electrodes. The architecture is realized by uniformly sputtering an amorphous Si-C interphase onto an oxidized carbon nanotube buckypaper, forming a free-standing OAI-SiC/OCNT monolith. The three-dimensional OCNT scaffold provides bottom-up mechanical compliance and continuous electron transport, while an in situ amorphous carbon phase homogenizes internal stress. Strong covalent Si-O-C and C-O-C interfacial bonding anchors the silicon film, enabling crack-free coatings up to -1 mu m well beyond the thickness limits typically reported for silicon film anodes. With an optimized Si/C ratio, the OAI-SiC_50W electrode exhibits a highly homogeneous microstructure and the lowest interfacial impedance, delivering a gravimetric capacity of 2385 mAh g- 1 with an initial Coulombic efficiency of 83% and retaining 2341 mAh g- 1 after 300 cycles. The electrode also maintains over 98% capacity after 5000 bending cycles and achieves an areal capacity of -10 mAh cm- 2 and an electrode-level energy density of -36.6 mWh cm- 2 without binders or metal current collectors. These results establish architectural strain buffering combined with covalent interfacial bonding as a general design principle for mechanically robust, highloading silicon electrodes.

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