MnCuNi Prussian Blue Analogue-Derived Polymetallic Layered Oxides as SIBs Cathode Materials

Layered transition-metal oxides (LTMOs) hold great promise as high-energy cathodes for sodium-ion batteries but suffer from poor structural stability and sluggish kinetics. Herein, a ternary MnCuNi-PBA precursor was converted into a high-performance LTMO via a tailored NaOH oxidation-calcination process. The optimal MnCuNi-LTMO-0.9 sample exhibits a well-ordered layered structure with mixed-valence metal states. Electrochemical tests show a high specific capacity of 180 mAh·g–1 at 25 mA·g–1, excellent rate capability (83.4% capacity recovery), and good cycling stability (61.7% capacity retention after 150 cycles). Operando XPS analysis confirms that the Mn and Cu redox couples synergistically contribute to the high capacity, while Ni stabilizes the framework. This work provides a feasible multimetal doping strategy to develop advanced LTMO cathodes for sodium-ion batteries.