Biphasic and Triphasic Oxide Cathode Materials for Advanced Na-Ion Batteries

Low-cost Na-ion batteries (NIBs) hold significant potential for grid energy storage. Na x TMO 2 oxides are considered one of the cathode candidates for NIBs. However, the phase transitions and Jahn–Teller distortion lead to their structural decay and performance decline. The synergistic effects arising from the combination of O-type, P-type, tunnel, and spinel structures can enhance their electrochemical properties. Recent studies in biphasic and triphasic intergrowth present considerable potential for addressing the aforementioned challenges. In this Review, we first comprehensively discuss the main strategies for synthesizing biphasic and triphasic oxides. Then, recent advancements in multiphase oxide cathodes for NIBs are further summarized, with a focus on their electrochemical behaviors and reaction mechanisms. Finally, the persistent challenges and future opportunities for the multiphase oxide cathodes are outlined. This Review aims to provide a profoundly significant guiding framework for the rational design of multiphase oxide cathodes for advanced NIBs.