In Situ TEM Observations of Discharging/Charging of Solid‐State Lithium‐Sulfur Batteries at High Temperatures
Zaifa Wang, Yongfu Tang, Liqiang Zhang, Meng Li, Zhiwei Shan, Jianyu Huang
Abstract
Abstract Understanding the structural evolution of Li 2 S upon operation of lithium‐sulfur (Li‐S) batteries is inadequate and a complete decomposition of Li 2 S during charge is difficult. Whether it is the low electronic conductivity or the low ionic conductivity of Li 2 S that inhibits its decomposition is under debate. Furthermore, the decomposition pathway of Li 2 S is also unclear. Herein, an in situ transmission electron microscopy (TEM) technique implemented with a microelectromechanical systems (MEMS) heating device is used to study the precipitation and decomposition of Li 2 S at high temperatures. It is revealed that Li 2 S transformed from an amorphous/nanocrystalline to polycrystalline state with proceeding of the electrochemical lithiation at room temperature (RT), and the precipitation of Li 2 S is more complete at elevated temperatures than at RT. Moreover, the decomposition of Li 2 S that is difficult to achieve at RT becomes facile with increased Li + ion conduction at high temperatures. These results indicate that Li + ion diffusion in Li 2 S dominates its reversibility in the solid‐state Li‐S batteries. This work not only demonstrates the powerful capabilities of combining in situ TEM with a MEMS heating device to explore the basic science in energy storage materials at high temperatures but also introduces the factor of temperature to boost battery performance.