Excellent Structural Stability-Driven Cyclability in P2-Type Ti-Based Cathode for Na-Ion Batteries

In the current study, we have synthesized Ti-based P2-type Na0.7Ni0.2Cu0.1Ti0.65O2 (NNCT) through the sol–gel route and characterized it for its structural, electrical, and electrochemical properties. The analysis of X-ray diffraction (XRD) data confirmed the existence of a single P2 phase for the sample calcined at 950 °C with suppressed Na-ion vacancy ordering. Impedance studies and chronoamperometric data revealed that NNCT exhibited a poor conductivity of ∼1.37 × 10–7 S cm–1 at room temperature, with the electronic conductivity contribution to the total electrical conduction being only 0.4%. The sample exhibited specific capacities of 83, 54, and 42 mA h g–1 at discharge rates of 0.1C, 0.5C, and 1C, respectively, with remarkable cyclic stability of 96% capacity retention after 700 cycles at 0.5C which makes NNCT an attractive cathode for Na-ion batteries in stationary storage applications. The ex situ XRD analysis confirmed that NNCT maintains a single P2 phase during cycling between 2.0 and 4.2 V. NNCT also exhibited moisture stability, thus enabling the use of a cost-effective water-based slurry for cathode layer fabrication.