Al-doped NaNi1/3Mn1/3Fe1/3O2 for high performance of sodium ion batteries

Herein, we report a series of O3-type Na(Ni1/3Mn1/3Fe1/3)1-xAlxO2 (x = 0, 0.03, 0.05, 0.07) oxides as sodium-ion battery cathode materials synthesized via spray pyrolysis method. The structure, morphology, and electrochemical performance of Na(Ni1/3Mn1/3Fe1/3)1-xAlxO2 (x = 0, 0.03, 0.05, 0.07) are characterized by XRD, SEM, CV, and galvanostatic charge and discharge tests, respectively. Na(Ni1/3Mn1/3Fe1/3)0.95Al0.05O2 delivers an initial discharge capacity of 145.4 mAh g−1 at 0.1 C and exhibits a favorable reversible capacity about 128.4 mAh g−1 after 80 cycles at 0.2 C, with the capacity retention of 77.5% at the voltage range of 2.0 to 4.2 V. XPS analysis reveals that Al-doping could alleviate the Jahn-Teller effect caused by Mn3+ and enhance the structural stability of layered oxides. The results confirm that a small quantity of (5 at. %) Al-doping improves the structural stability of the material, therefore leading to the excellent electrochemical performance.