Synthesis strategies and in situ characterization of layered transition metal oxide materials for sodium-ion batteries

Abstract Sodium-ion batteries (SIBs) have emerged as a promising complementary technology to lithium-ion batteries (LIBs), largely due to sodium’s abundance and affordability. Among the positive electrodes, layered transition metal oxides (LTMOs) are particularly promising for their tunable chemistry, high energy density, and compatibility with LIB manufacturing infrastructure. However, current sodium-ion LTMOs typically underperform their lithium-ion counterparts in terms of electrochemical performance. Achieving commercially viable SIBs requires precise control over LTMO synthesis to tailor and optimize their functionalities. This perspective explores the primary synthesis methods for Na-ion LTMOs, outlining their benefits and limitations. In particular, the role of synthesis on the morphology control of Na-ion LTMOs will be examined. Recent progress in in situ characterization that provide insights into structural, chemical, and morphological changes during synthesis will also be discussed. Together, these advances offer pathways toward optimizing LTMO materials for next-generation sodium-ion battery technologies. Graphical abstract