NaV(PO) cathode materials for advanced sodium-ion batteries: Modification strategies and density functional theory calculations.

With the rapid development of electric vehicles and smart grids, the demands for energy supply systems such as secondary batteries are increasing exponentially. Despite the world-renowned achievements in portable devices, lithium-ion batteries (LIBs) have struggled to meet the demands due to the constraints of total lithium resources. As the most promising alternative to LIBs, sodium-ion batteries (SIBs) are generating widespread research enthusiasm around the world. Among all components, the cathode material remains the primary obstacle to the practical application of SIBs due to its inability to match the performance of other components. NaV(PO) (NVP) stands out as a promising cathode material for SIBs, given its suitable theoretical specific capacity, appropriate operating voltage, robust structural stability, and excellent ionic conductivity. In this article, we first review recent modification strategies for NVP, including conductive substance coating, ion doping (single-, dual- and multi-site doping) and morphology modulation (from zero-dimensional (0D) to three-dimensional (3D)). Subsequently, we summarize five ways in which density functional theory (DFT) calculations can be applied in guiding NVP modification studies. Furthermore, a series of emerging studies combining DFT calculations are introduced. Finally, the remaining challenges and the prospects for optimization of NVP in SIBs are presented.