A Stress Self-Adaptive Bimetallic Stellar Nanosphere for High-Energy Sodium-Ion Batteries

Bimetallic composites exhibit great potential as anode materials in advanced energy storage systems owing to their inherent tunability, cost-effectiveness, and simultaneous achievement of high specific capacity and low reaction potential. However, simple biphase mixing often fails to achieve satisfactory performance. Herein, an innovative stress self-adaptive bimetallic stellar nanosphere (50-200 nm) wherein bismuth (Bi) is fabricated, as a core, is seamlessly encapsulated by a tin (Sn) sneath (Sn-Bi@C). This well-integrated stellar configuration with bimetallic nature embodies the synergy between Bi and Sn, offering fortified conductivity and heightened sodium ion diffusion kinetics. Moreover, through meticulous utilization of finite element analysis simulations, a homogeneous stress distribution within the Sn-enveloped Bi, efficiently mitigating the structural strain raised from the insertion of Na+ ions, is uncovered. The corresponding electrode demonstrates remarkable cyclic stability, as it exhibits no capacity decay after 100 cycles at 0.1 A g-1. Furthermore, it achieves an impressive 86.9% capacity retention even after an extensive 2000 cycles. When employed in a Na3V2(PO4)3 || Sn-Bi@C full cell configuration, it demonstrates exceptional capacity retention of 97.06% after 300 cycles at 1 A g-1, along with a high energy density of 251.2 W h kg-1. A bimetallic stellar nanosphere with bismuth (Bi) core seamlessly encapsulated by tin (Sn) sheath is developed. The synergistic interaction between Bi and Sn accelerates sodium ion diffusion kinetics and mitigates structural strain caused by sodium ions insertion. The resulting electrode maintains capacity after 100 cycles and retains 86.9% capacity after 2000 cycles.image