Exploring the Enhanced Electrochemical Performance of a P2/P3 Biphasic Composite as a Positive Electrode Material for Sodium‐ion Batteries

ABSTRACT Recently, research on structurally integrated layered transition metal oxides as positive electrode materials for sodium‐ion batteries has increased exponentially due to their improved electrochemical performance. In this work, we synthesized a P2/P3 biphasic composite, Na _2/3 Mn _2/3 Co _1/6 Ni _1/6 O ₂ , using the sol‐gel method with stepwise annealing, along with its P2 and P3 counterparts of the same composition. The composite demonstrated enhanced electrochemical performance through the combined contribution of the P2 and P3 phases. The biphasic material delivered an initial discharge capacity of 146 mAh g ⁻¹ with a capacity retention of 80% after 50 cycles. The biphasic material delivered a capacity of 67 mAh g ⁻¹ at a C‐rate of 5C, implying the superior rate performance of the composite structure. Further, the in operando differential electrochemical mass spectrometry (DEMS) was also employed to confirm the stability of the composite material at higher voltages. DFT calculations confirmed the thermodynamic stability and higher electronic activity of the P2/P3‐NMNC interface, consistent with its enhanced electrochemical behavior.