Strain-adaptive aluminum fluoride armor engineering for durable silicon-carbon anodes with suppressed swelling

Silicon-carbon (Si-C) composite anodes promise high energy density but suffer from severe volume fluctuations during cycling, which continuously disrupt the solid-electrolyte interphase (SEI) and accelerate capacity degradation. Herein, we present a scalable interfacial engineering strategy to construct a strain-tolerant aluminum fluoride (AlF₃) armor on porous Si-C architectures, which effectively isolates the active material from parasitic electrolyte reactions and mechanically confines interfacial deformation. Quantitative nanomechanical atomic force microscopy reveals a striking increase in Young’s modulus from 0–3 GPa for the pristine Si-C to 60–180 GPa for the armored composite. Consequently, electrode swelling after 100 cycles is dramatically suppressed from 49.6% to 15.2%. Benefiting from enhanced mechanical integrity and the in situ formation of fast Li-ion transport pathways, the AlF₃-armored Si-C anode delivers a high initial Coulombic efficiency of 93.3% and retains 82.3% capacity after 100 cycles in half-cells. In practical full-cell configurations paired with NCM811 cathodes, it achieves an impressive 84% capacity retention over 500 cycles. Bridging the gap between laboratory research and commercialization, we demonstrate the successful industrial scale-up of this process. The 200 kg batch synthesis exhibits excellent repeatability and a 77.7% reduction in coating cost, establishing a highly viable and cost-effective pathway for next-generation, high-energy-density lithium-ion batteries.