Preferential Alkali‐Ion Occupation in NASICON Cathodes Enables High‐Power Sodium‐Ion Batteries

Sodium-ion batteries (SIBs) are gaining attention as promising large-scale energy storage systems due to their cost-effectiveness and resource abundance. As a cathode material, NASICON-type Na$_3$V$_2$(PO$_4$)$_3$ (NVP) stands out for its high structural stability and energy density. However, its practical application is hindered by poor electronic conductivity and sluggish Na$^+$ diffusion kinetics. In this study, we systematically investigated the structural evolution and Na$^+$ storage behavior of NVP materials, particularly focusing on enhancing power capability through preferential substitution of Na$^+$ with other alkali metal ions (K$^+$ and Li$^+$). Results show that preferential K$^+$ occupation at (6b) Na1 sites can manipulate the crystal structure and regulate Na$^+$ migration behaviors, significantly influencing the energy efficiency, rate performance, and cycling stability. Consequently, the K$^+$-substituted material (NKVP) delivers, at room temperature, a discharge capacity of 80.6 mAh g$^{−1}$ at the ultrahigh rate of 100C but also retains 80.8% of its capacity over 10,000 cycles at 50C, along with superior high-temperature cycling stability over 3000 cycles at 10C and 60°C. ... mehrPractically, the NKVP//HC full cell exhibits superior power performance. This work provides critical insights into the rational design of high-performance NASICON materials, offering new pathways for the development of high-power SIBs.