Enhanced Kinetics of Lithium-Ion Charge Storage on Si Anode through Ultrasmall Magnesium Nitride Nanoparticles toward Fast and Durable All-Solid-State Lithium-Ion Batteries

Silicon, known for its high Li+ storage capacity, low redox potential, abundant reserves, and low cost, is regarded as a promising anode material for all-solid-state lithium-ion batteries (ASSLBs). Nevertheless, its practical application is hindered by severe volume expansion and sluggish reaction kinetics. Herein, Si@Mg3N2 composites are synthesized via a vacuum evaporation method, wherein ultrasmall Mg3N2 nanoparticles with an average size of 9 nm are uniformly coated onto the surface of commercial silicon microsheets. During the initial lithiation process, these Mg3N2 nanoparticles undergo an in situ phase transformation, forming a Li–Mg–Si alloy, Li–Mg alloy, and Li3N irreversibly. The resulting Li-rich substances with the mixed ionic/electronic conductive function effectively mitigate the substantial volume expansion associated with the Li–Si alloying reaction (reducing it from 210% to 38.6%), thereby enhancing electrode kinetics and mechanical stability. As a result, the Si@Mg3N2 composite anode delivers a reversible capacity of 2619 mAh g–1 at 0.1 A g–1 and maintains a discharge capacity of 1460 mAh g–1 even at a high rate of 5 A g–1 in half-cell configurations. Furthermore, ASSLBs incorporating the Si@Mg3N2 anode exhibit excellent rate capability (50.8 mAh g–1 at 40 C) and robust cycling stability (61.6% capacity retention after 1000 cycles).