Mechanism of Negative Electrode Materials for Sodium (Potassium) Storage Alloy

Yan Yu is the professor and doctoral supervisor of the the Department of Materials Science and Engineering, University of Science and Technology of China. She is the winner of national fund for Distinguished Young Scholars, a member of Royal Society of chemistry and the deputy editor in chief of Journal of power sources. At present, she has published more than 200 papers in science, nature energy and other internationally famous journals, including 27 adv. mater, 6 Angel. Chem. Int. ed., 7 nano lett. Her essays has been cited by others from SCI for more than 10000 times and H factor has reached 58. She has been selected into the list of high-cited scholars in the material category of Clarivate Analytics and Elsevier. She has won the Sofia Award of the Humboldt Foundation of Germany, the Youth Science and Technology Award of China Silicate Association, and the Hou Debang Science and Technology Youth Award of the Chemical Industry of China.

In recent years, sodium and potassium ion batteries have become the research hotspot of electrochemical energy storage technology, and are expected to become a new generation of high energy density and low-cost electrochemical energy storage system. However, the application of large ion radius and slow reaction kinetics is still facing great challenges. At present, the reports of high-performance sodium (potassium) ion battery anode materials are mainly focused on carbon based materials. However, the specific capacity of these carbon based anode materials based on the mechanism of deblocking reaction is generally lower than 300 MAH/g, which is difficult to meet the actual needs. The development of alloy anode materials with high specific capacity, long cycle life and high rate performance has broad application prospects. Therefore, in order to solve the problems of large volume change effect and poor conductivity of alloy anode materials in the process of Na+, K+, etc., our research group recently carried out relevant research in alloy anode materials (tin, red phosphorus, antimony, bismuth). First of all, aiming at sb as an alloy anode material, we developed the nano limited area electric couple replacement method, and successfully prepared a kind of hollow yolk shell structure Sb@C material. The test shows that the carbon shell can effectively alleviate the volume change of sb during the charging and discharging process, promote the stability of SEI, and maintain the integrity of the electrode structure and the stability of the electrochemical performance. In recent research, the applicant has developed a simple liquid-phase method to synthesize Bi@C composite with core-shell structure, which shows excellent performance of sodium and potassium storage. At the same time, the in-situ transmission electron microscope reveals that the core-shell structure can effectively alleviate the volume expansion during the charging and discharging process and ensure the stability of the electrode structure. Next, for red phosphorus, a kind of high specific capacity alloy anode material, we designed a red phosphorus inlaid nitrogen doped hollow porous carbon nanofiber self-supporting anode material, which effectively inhibited the volume expansion of red phosphorus, and obtained the long cycle life and high specific capacity sodium (potassium) storage performance. At the same time, in-situ Raman and not in-situ XRD analysis confirmed the potassium storage mechanism of red phosphorus.