In Situ Powder Diffraction Studies of Electrode Materials in Rechargeable Batteries.

The ability to directly track the charge carrier in a battery as it inserts/extracts from an electrode during charge/discharge provides unparalleled insight for researchers into the working mechanism of the device. This crystallographic-electrochemical information can be used to design new materials or modify electrochemical conditions to improve battery performance characteristics, such as lifetime. Critical to collecting operando data used to obtain such information in situ while a battery functions are X-ray and neutron diffractometers with sufficient spatial and temporal resolution to capture complex and subtle structural changes. The number of operando battery experiments has dramatically increased in recent years, particularly those involving neutron powder diffraction. Herein, the importance of structure-property relationships to understanding battery function, why in situ experimentation is critical to this, and the types of experiments and electrochemical cells required to obtain such information are described. For each battery type, selected research that showcases the power of in situ and operando diffraction experiments to understand battery function is highlighted and future opportunities for such experiments are discussed. The intention is to encourage researchers to use in situ and operando techniques and to provide a concise overview of this area of research.