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.