Ultrafast Joule-Heating Disproportionation for Engineering Sub-2 nm Si Nanodomains toward Stable, High-Performance...

Silicon monoxide (SiO) is a promising anode material for lithium-ion batteries but suffers from significant volume expansion and poor cycling stability. We demonstrate that SiO undergoes electrochemical disproportionation during cycling, forming Si nanodomains that stabilize the structure. Traditional thermal disproportionation methods struggle with controllability and are energy-intensive. Here, we introduce flash joule heating (FJH) for prestabilization, achieving disproportionation in 0.3 s with significantly improved energy efficiency. The ultrafast heating enables better control over size, density, and crystallinity of Si nanodomains while preventing SiO₂ crystallization. The resulting ∼1.5 nm Si nanodomains, embedded in an amorphous SiO₂ matrix, enhance electrochemical performance and reduce volume expansion. The optimized anodes deliver a specific capacity of 1419 mAh g^-1 with 96.6% retention after 150 cycles and 88.6% retention after 300 cycles in NCM811 full cells. This work establishes FJH as an efficient method for pre-engineering SiO, offering a promising route to durable, high-performance anodes.