Contact Lithiation‐Assisted Alloying Enabling Fast‐Charging Silicon Anodes

Abstract Lithium (Li) dendrites form on anode surface during fast charging because of sluggish alloying kinetics, thereby compromising cycling stability and raising safety concerns in high‐energy silicon (Si)‐based lithium‐ion batteries (LIBs). Here, we introduce a contact lithiation‐assisted alloying mechanism designed to enhance the Si anode's reaction kinetics. By transforming Li deposits from a loose, dendritic morphology to a dense, adherent layer with improved diffusion, contact lithiation with Si is promoted. This not only increases the reaction rate and Li deposit utilization but also mitigates the formation of residual “dead Li” and Li compounds typically associated with dendritic Li plating. The experimental results demonstrate that decorating Si particles with ultra‐fine (∼10 nm), uniformly distributed Ag nanodomains facilitates the formation of a conformal Li plating layer and in situ contact lithiation reaction. Consequently, the Si@Ag electrode achieves a high average Coulombic efficiency of 99.2% at 3 C for 300 cycles, compared with 96.4% for unmodified Si. Moreover, an Ah‐level LiNi_0.6Co_0.2Mn_0.2O₂||Si@Ag cell delivers 86.8% of its capacity within 15 minutes of charging (4 C) and retains 81.2% capacity over 160 cycles. This strategy provides a promising route to advance fast‐charging LIBs with high energy density.