Sodium resources have the advantages of wide distribution, abundant reserves and low cost, so that sodium ion batteries are expected to become the key technology to promote the next generation of energy revolution. V-VI-based metal compounds (Sb2Te3, Bi2O3, Bi2Se3) have the advantages of high capacity, rich raw materials, low cost and easy preparation, and are the most promising sodium ion battery negative materials. However, the low electron conductivity and ion diffusion rate make its electrochemical activity poor in the process of charging and discharging, which leads to the decay of battery capacity and cycle life, which seriously hinders the application of V-VI compounds in sodium ion batteries.
In response to the above problems, Professor Zhu Ming-Qiang of the Energy Photoelectronics Function Laboratory of Wuhan National Laboratory for Optoelectronics of Huazhong University of Science and Technology combined the characteristics of one-dimensional nanowire directional transmission electrons and two-dimensional nanochip electron regulation, and greatly improved the electron conduction and ion diffusion performance of Sb2Te3-Te (STNH) electrodes by constructing Sb2Te3 nanochips and Te nanowire heterogeneous junctions. Theoretical calculations show that a single Sb2Te3 and Te have a large band width and exhibit the characteristics of semiconductors, while the electrons of the compounded STNH heterogeneous junction occupy the peak near the Fermi energy level, indicating that the STNH heterogeneous junction has better electron conductive properties, as shown in Figure 1. In addition, the electrochemical impedance spectrum further verifies the excellent ion diffusion properties of stNH heterogeneous junctions. Electrochemical performance tests show that after a current density of 1.5 A g-1 and a cycle of 1000 turns, there is still a ratio capacity of 365 mAh g-1, and a ratio capacity of 226 mAh g-1 at a high current density of 15 A g-1, demonstrating excellent cycle and multiplier performance. This study illustrates the transmission mechanism of electrons and ions in nano-heterogeneous junctions in sodium ion batteries, which is of great guiding significance to the design of sodium storage materials.
On January 8, 2020, the work was published in the internationally renowned energy journal Nano Energy (2020) 10468 under the title "Boosted charge transfer and Na-ion diffusion in cooling-fins-like Sb2Te3-nano-heterostructure for long-cycle life and high-rate capability anode." https://doi.org/10.1016/j.nanoen.2020.104468.
Dr. Hong Yin is the first author of the paper, and Professor Ming-Qiang Zhu and Chong Li are the corresponding authors. The work has been funded by the National Natural Science Foundation of China, the postdoctoral foundation and other projects.
Figure 1 (a) SEM diagram of STNH material; (b) XRD diagram of STNH material; (c) Te, Sb2Te3, Sb2Te3-Te orbital density map; (d) long-life cycle diagram of STNH material.
