Bismuth particles encapsulated in plate-like carbon shells as high-performance anodes for sodium storage

Bismuth (Bi), as an alloying anode material for sodium-ion batteries (SIBs), has attracted significant attention due to its high theoretical capacity (386 mAh/g) and volumetric energy density (3800 mAh/cm³). However, Bi undergoes substantial volume expansion (352 %) during the sodiation/desodiation phase transitions, leading to electrode structure fragmentation. To address this challenge, constructing a carbon-encapsulated composite structure has proven to be an effective strategy. Herein, Bi particles encapsulated in plate-like carbon shells (Bi@C) are synthesized via hydrothermal, high-temperature carbonization and in-situ reduction processes. The introduction of plate-like carbon shells accelerates charge transfer and ion transport process while mitigating the impact of volume changes. The electrochemical behavior of Bi@C has been investigated, revealing a charge transfer resistance as low as 0.16 Ω, which confirms its rapid kinetic processes. Benefiting from this structure, Bi@C achieves an excellent rate performance with a reversible capacity of 373.2 mAh/g at 0.2 A/g and 366.6 mAh/g at 20 A/g, as well as a stable cycling performance, retaining 358.7 mAh/g after 1000 cycles at 1 A/g and 364.7 mAh/g after 3300 cycles at 5 A/g. This study provides a new approach for the development of novel alloy anodes and the enhancement of sodium storage performance. We encapsulate bismuth particles in plate-like carbon shells to enhance structural stability and improve ion transport rates, ultimately achieving a high-performance sodium storage anode with nearly no capacity decay during charge-discharge cycles. • A novel plate-like carbon shell structure. • Excellent dispersion of Bi particles with an average spacing of 305.82 nm. • Plate-like carbon shells exhibit a certain degree of graphitization. • Bi@C exhibits an extremely low R ct of 0.16 Ω after 1000 cycles. • Bi@C shows almost no capacity decay at different current densities.