Abstract: Alloying-type anodes have attracted widespread attention owing to their high energy density and suitable redox potential. However, However, its practical application is impeded by substantial volume expansion during repeated charge/discharge cycling, which inevitably induces severe structural degradation and leads to rapid capacity decay. To address this issue, herein, N-doped carbon-encapsulated Bi_0.6Sb_0.4@C composite sheets were synthesized via a polyvinylpyrrolidone (PVP)-assisted Sol-Gel method followed by carbothermal reduction. The Bi_0.6Sb_0.4@C architecture consists of Bi-Sb alloy nanoparticles uniformly anchored in the nitrogen-doped carbon framework. This hierarchical structure effectively shortens Na⁺ diffusion pathways, enhances electronic conductivity, and mitigates volumetric strain during alloying/dealloying reactions. Bi_0.6Sb_0.4@C anode achieved outstanding Na⁺-storage performance delivering a reversible capacity of 269.46 mAh·g^-1 after 1500 cycles at 0.5 A·g^-1, and retaining a high discharge capacity of 347.29 mAh·g^-1 even at a high current density of 2 A·g^-1. The superior electrochemical behavior is attributed to the synergistic interaction between the Bi-Sb alloy and the nitrogen-doped carbon framework. The Bi-Sb alloy endows the electrode with accelerated reaction kinetics and enhanced structural stability, while the N-doped carbon nanosheet framework constructs a continuous conductive network and efficiently buffers the volume variation during cycling. This work offers a feasible design strategy for high-performance alloying-type anodes toward advanced sodium-ion batteries.

Key words: sodium-ion battery, Bi_0.6Sb_0.4@C, anode material, carbon framework