High-energy bimetallic substituted Na3V2(PO4)3 cathode for advanced sodium-ion batteries

NASICON-type cathodes have attracted great attention due to their open three-dimensional (3D) frame structure and excellent ion transport properties. Accordingly, how to improve the stability and energy density of materials is a hot topic of research. In this study, the significant effects of aluminum-zirconium bimetallic substitution on electrode kinetics and structural stability are reported. The designed Na2.9V1.8Al0.1Zr0.1(PO4)(3) cathode exhibits a highly reversible capacity of 107 mAh g(-1) at 1C and decent cyclic stability (75 mAh g(-1) capacity after 2000 cycles at 20C). These excellent electrochemical properties can be attributed to expanding the lattice structure and activating part of V-,(4+) which facilitates the migration of Na+ and increases the reversible capacity. The cyclic voltammetry, electrochemical impedance spectra and galvanostatic intermittent titration technique tests analyze the diffusion kinetics of sodium ions and confirm the desired sodium ion diffusion coefficients (DNa+). In situ X-ray diffraction reveals reversible structural changes during the electrochemical reaction, which confirms that the bimetallic doping strategy slows down material volume change. This work provides a new perspective for the construction of high-performance NASICON cathode materials.