Closed Pores as Internal Stress-Regulation Units for Practical Silicon-Carbon Anodes

Silicon-carbon anodes are among the most promising candidates for high-energy lithium-ion batteries, yet their practical implementation remains constrained by lithiation-induced outward deformation, electrode cracking, and persistent interphase degradation. Here, closed pores are introduced as internal stress-regulation units to address the coupled mechanical and electrochemical instability of silicon-carbon anodes. Heteroatom-doped carbon hosts are engineered to contain abundant closed nanopores, which redirect expansion-induced stress toward the particle interior and suppress macroscopic electrode swelling. Meanwhile, heteroatom doping enlarges the carbon interlayer spacing and enhances electronic conductivity, enabling accelerated and more balanced Li⁺ insertion/extraction kinetics. As a representative material, the nitrogen-doped silicon-carbon composite delivers a reversible capacity of 1756.5 mAh g^{- 1}, an initial Coulombic efficiency of 90.2%, and 868.4 mAh g^-1 at 3 C, while reducing electrode thickness expansion from 38.4% to 13.1% after 50 cycles. The material is further produced in 6 kg batches and enables 2 Ah LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) pouch cells with 80.0% capacity retention after 1200 cycles and only 8.4% thickness growth after 900 cycles. Machine-learning-guided phosphorus doping further validates the transferability of the closed-pore design. This work establishes closed-pore stress regulation as a scalable structural strategy for practical low-expansion silicon-carbon anodes.