Synthesis and Electrochemical Study of New P3 Type Layered Na0.6Ni0.25Mn0.5Co0.25O2 for Sodium‐Ion Batteries

Abstract The room temperature stable P3 type Na 0.6 Ni 0.25 Mn 0.5 Co 0.25 O 2 phase was studied as an interaction material for Na ion batteries. The phase was synthesized by mixed hydroxide co‐precipitation method followed by heating at 750 °C in air. The phase purity was analyzed by means of Rietveld refinement using GSAS software. X‐ray photoelectron spectroscopy (XPS) analysis showed that Co, and Mn are in oxidation states of 3+ and 4+, respectively, and Ni is in 2+ and 3+ oxidation states. The electrochemical properties of this layered material as a cathode delivered the reversible discharge capacity of 105 and 130 mAh/g at C/10 rate in the voltage window of 1.5‐3.6 and 1.5‐4.0 V vs. Na + /Na, respectively. The good capacity retention and nearly 99 % of coloumbic efficiency was observed. The Na insertion and de‐insertion was occurred by reversible phase transitions as evidenced by ex‐situ powder X‐ray diffration. With increasing cutoff voltage to 4.4 V, the ex‐situ powder X‐ray diffration pattern indicated that the existence of P3 phase at high Na de‐insertion.