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Abstract The electrochemical performance and diffusion kinetics of a newly designed NASICON‐type Na 3.3 Mn 1.2 Ti 0.75 Mo 0.05 (PO 4 ) 3 /C composite material is reported as a cathode for cost‐effective sodium‐ion batteries. A novel strategy of small Mo doping successfully stabilizes the sample having high Mn content in single‐phase rhombohedral symmetry. The high‐resolution microscopy analysis reveals nanocrystallites of around ∼18 nm, uniformly embedded within the semi‐graphitic carbon matrix, which enhances the surface electronic conductivity and effectively shortens the sodium‐ion diffusion path. More importantly, a stable electrochemical behavior is demonstrated, with enhanced discharge capacity of 124 mAh/g at 0.1 C, having good reversibility and retaining 77% of its capacity after 300 cycles, and 70% even after 400 cycles at 2 C. The sodium‐ion diffusion coefficients, estimated using both galvanostatic intermittent titration technique (GITT) and cyclic voltammetry, are found to lie within the range of 10 −9 to 10 −11 cm 2 /s. Additionally, the bond‐valence site energy mapping predicted a sodium‐ion migration energy barrier of 0.76 eV. A detailed distribution of relaxation times (DRT) analysis is used to deconvolute the electrochemical impedance spectra into distinct processes based on their characteristic relaxation times. Notably, the solid‐state diffusion of sodium ions within the bulk electrode, with a relaxation time of ∼50 s, shows a consistent trend with the diffusion coefficients obtained from GITT and Warburg‐based evaluations across the state of charge.
Sharma et al. (Mon,) studied this question.