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All-solid-state batteries comprising Si anodes are promising materials for energy storage in electronic vehicles because their energy density is approximately 1.7 times higher than that of graphite anodes. However, Si undergoes severe volume changes during cycling, resulting in the loss of electronic and ionic conduction pathways and rapid capacity fading. To address this challenge, we developed composite anodes with a nanoporous Si fiber network structure in sulfide-based solid electrolytes (SEs) and conductive additives. Nanoporous Si fibers were fabricated by electrospinning, followed by magnesiothermic reduction. The total pore volume of the fibers allowed pore shrinkage to compensate for the volumetric expansion of Li12Si7, thereby suppressing outward expansion and preserving the Si-SE (or conductive additive) interface. The network structure of the lithiated Si fibers compensates for electronic and ionic conduction pathways even to the partially delaminated areas, leading to increased Si utilization. The anodes exhibited superior performance, achieving an initial Coulombic efficiency of 71%, a reversible capacity of 1474 mAh g−1, and capacity retention of 85% after 40 cycles with an industrially acceptable areal capacity of 1.3 mAh cm−2. The proposed approach can reduce the constraint pressure during charging/discharging and may have practical applications in large-area all-solid-state batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nanoporous Si particles are prepared from Mg 2 Si reduction of SiO 2 fumes. • Nanoporous Si is composited with Li 3 PS 4 to prepare anodes for all-solid-state lithium-ion batteries. • Electrical conductivity and charge capacity of Si composite anodes increase with conductive additive content. • There is an optimal amount of conductive additive to improve the discharge capacity and capacity retention of Si composite anodes. Si is the most promising anode active material for lithium-ion batteries owing to its high theoretical capacity and low operating potential. In this study, composite anodes consisting of nanoporous Si particles, Li 3 PS 4 solid electrolyte, and a conductive additive (CA) in weight ratios of 4:6: x (x = 1, 2, 3, and 4) are fabricated and tested. The electrical conductivities are 4.1 × 10-4 S cm−1 and 6.8 × 10-4 S cm−1 at × = 1 and 4, respectively. In addition, the charge capacity increases in proportion with CA content from 2700 mAh g−1 to 3015 mAh g−1. These results indicate that new conduction paths are created in the nanoporous Si composite anodes upon adding a CA. To the best of our knowledge, this is the first study to examine the effect of a CA on the electrochemical performance of all-solid-state lithium-ion batteries with Si-based anodes. Our findings provide valuable information that should be helpful in meeting the energy demands of next-generation applications. [ABSTRACT FROM AUTHOR]