Structural insights into the dynamic and controlled multiphase evolution of layered-spinel heterostructured sodium oxide cathode

Summary: Concepts in sodium oxide cathode composite structures have captured widespread attention; however, the detailed monitoring and accurate control of composite structural evolution during charge and discharge process remain challenging, especially for complex triphases and other similar systems. Here, we report the accurate manipulation of multiphase structural evolution during high-voltage cycling with improved electrochemical performance and adjustable sodium ion intercalation/deintercalation electrochemical behavior via rational chemical element substitution using a series of Fd-3m spinel and layered P2/P3 heterostructures as proof-of-concept materials. Multiphase evolutions as a function of chemical substitution during high-voltage cycling are demonstrated. Meanwhile, we also monitor the dynamic formation process during calcination and observe the atomic arrangement of triphase heterostructure through various advanced characterization techniques. Overall, this study reveals controllable multiphase structural evolution in a model system and explores the related fundamental science required for future development of high-performance sodium-ion batteries