Superior Na-Storage Performance of Low-Temperature-Synthesized Na₃(VO_1-xPO₄)₂F_1+2x (0≤x≤1) Nanoparticles for Na-Ion Batteries

Na-ion batteries are becoming comparable to Li-ion batteries because of their similar chemical characteristics and abundant sources of sodium. However, the materials production should be cost-effective in order to meet the demand for large-scale application. Here, a series of nanosized high-performance cathode materials, Na₃(VO_1-xPO₄)₂F_1+2x (0≤x≤1), has been synthesized by a solvothermal low-temperature (60-120 °C) strategy without the use of organic ligands or surfactants. The as-synthesized Na₃(VOPO₄)₂F nanoparticles show the best Na-storage performance reported so far in terms of both high rate capability (up to 10 C rate) and long cycle stability over 1200 cycles. To the best of our knowledge, the current developed synthetic strategy for Na₃(VO_1-xPO₄)₂F_1+2x is by far one of the least expensive and energy-consuming methods, much superior to the conventional high-temperature solid-state method.