Achieving the Stable Structure and Superior Performance of Na3V2(PO4)2O2F Cathodes via Na-Site Regulation

Na3V2(PO4)(2)O2F (NVPOF) is considered as a promising cathode material for sodium-ion batteries due to its high structural stability and high average operating voltage (3.8 V). However, its low electronic conductivity and slow sodium-ion diffusion kinetics hinder its practical application. Here, an approach of Na-site regulation is proposed to adjust the intrinsic Na+ diffusion efficiency and electronic conductivity, thus improving the electrochemical performance of NVPOF. Guided by density functional theory calculations, we demonstrate that Na-site regulation can be subtly realized by accurate Li substitution on the Na2 site in NVPOF. The as-prepared Na2.75Li0.25V2(PO4)(2)O2F (NLVPOF) shows an increase of 1.53 and 1.55 times in rate capability and capacity retention (500 cycles) than NVPOF, respectively. Such a simple and effective Na-site regulation provides a new avenue in constructing advanced Li/Na-ion cathode materials.