Toward high energy density cathode materials for sodium-ion batteries: investigating the beneficial effect of aluminum doping on the P2-type structure

Aluminum doping of the P2-type layered structure results in a Na-ion cathode material (Na0.6Ni0.22Al0.11Mn0.66O2) with excellent performance. The material, in fact, exhibits outstanding specific capacities, 250 mA h g-1 and 150 mA h g-1 at 0.1 and 5C rate, respectively, which have never been reported before. Herein, a deep investigation of both the electrochemical behavior and the structural and morphological properties upon cycling reveals the beneficial effect of aluminum and the importance of a suitable metal intermixing selection for the obtainment of high performance cathode materials.