A Layer-Structured GeBi₄Te₇ Anode for Na-Ion Batteries

Sodium-ion batteries are considered one of the most promising energy storage systems for large-scale energy storage and low-speed electric vehicles. However, developing suitable anode materials with a high capacity and stable cycling performance for sodium-ion batteries remains a challenge. In this work, we report a layered ternary GeBi₄Te₇ anode material, which can be synthesized by a facile high-energy ball milling method. Its structure consists of GeBi₂Te₄ and Bi₂Te₃ layers stacked periodically along the c-axis, providing spacious two-dimensional channels for the rapid insertion and extraction of sodium ions. Electrochemical test results demonstrate that the prepared GeBi₄Te₇ anode exhibits a high reversible specific capacity of 449.4 mA h g^-1 at a current density of 1 A g^-1 and a high initial Coulombic efficiency of 96.4%. Moreover, the Na-reaction mechanism of GeBi₄Te₇ was investigated. The results indicate that GeBi₄Te₇ undergoes a multistep sodium ion storage process following the electrochemical sequence of its components. During the discharge, sodium ions inserted into the interlayer gaps of the layered structure first, and then Na₂Te, NaBi, Na₃Bi, and NaGe were generated sequentially. During the charging stage, GeBi₄Te₇ compounds can be regenerated after the sodium extraction. In addition, the GeBi₄Te₇ shows 90.8% capacity retention after 7400 cycles during the potential gap of 0-1.0 V. This research provides insights into exploring multimetal tellurides for applications in the field of energy storage.