High-voltage pulsed-DC driven low-pressure hollow-cathode plasma CVD synthesis of carbon-coated silicon for lithium-ion batteries

Silicon-based anodes are promising for high-energy-density lithium-ion batteries (LIB) but suffer from severe volume changes. Silicon-carbon (Si-C) composites mitigate these issues and chemical vapor deposition (CVD) enhances carbon adhesion though conventional CVD has low efficiency. Plasma-enhanced CVD (PECVD) improves this yet fundamental plasma-silicon interactions remain underexplored. To address this, a high-voltage pulse-DC plasma CVD system integrated with ultrasonic dispersion is developed, enabling Si powder transport into the plasma zone. Plasma simulations uncover temporal-spatial discharge evolution and cathode sheath electron heating while optical emission spectroscopy (OES) validates Ar-facilitated C₂H₂ dissociation. These findings reveal regulated energy transfer to Si surfaces and clarify interactions between plasma and silicon powders during carbon film formation. Material characterizations confirm amorphous carbon coverage, robust Si-C bonding, silicon-carbon crystallization and a promoted graphite phase with reduced disorders. According to the plasma properties, the characterization results are reasonably interpreted such as sputtering-induced crystallization and energy transfer/heating-driven graphite promotion. Electrochemical measurements show the carbon film initially fail to form a stable solid electrolyte interphase (SEI) layer due to silicon expansion and internal voids generated by plasma effects, however, the SEI layer stabilizes with lithiation/delithiation cycling and acceptable performance is achieved. This work fills the knowledge gap in plasma-silicon interactions, providing a low-temperature viable route for fabricating Si-C LIB anodes.