Quantitative Design of Scalable Silicon Anodes with Balanced Strain and Specific Capacity

Silicon is a promising anode material for next-generation lithium-ion batteries owing to its high theoretical capacity and natural abundance. However, its practical application is limited by the challenge of simultaneously achieving high specific capacity, low mechanical strain, and low cost. In this work, a composition-guided quantitative design strategy is proposed, in which the mass ratio of silicon to carbon nanofibres (Si/CNFs) is treated as a practical control parameter to balance capacity and volumetric expansion under realistic cost constraints. By systematically correlating component ratio, pore architecture, and electrode-level volumetric evolution, a practical CNFs content window of 14.3%–42.8% is identified, with compositions near 28.6% providing an optimal balance between active-material loading and strain buffering. A stepwise validation strategy is employed, in which nano-sized silicon is first used to elucidate the underlying mechanism, demonstrating that the optimized CNFs framework maintains structural integrity during cycling. This design concept is subsequently extended to micron-sized silicon, where the porous buffering reservoir effectively accommodates the severe volume changes of larger particles. As a demonstration of scalability, a composite electrode containing >70% micron-sized silicon delivers a reversible capacity of 1188 mAh g −1 with 83% retention after 200 cycles, while limiting irreversible volumetric strain to below 10%.