Carbon-coated Na3V2(PO4)2F3 nanoparticles embedded in a mesoporous carbon matrix as a potential cathode material for sodium-ion batteries with superior rate capability and long-term cycle life

Abstract

A carbon-coated Na₃V₂(PO₄)₂F₃ nanocomposite (NVPF@C) is successfully realized by a facile sol–gel method. Carbon-coated NVPF nanoparticles are dispersed inside the mesoporous carbon matrix, which can not only improve the electron/ion transfer among different nanoparticles, but also benefit the electrolyte wetting during cycling. As a result, the NVPF@C cathode demonstrates remarkable Na⁺ storage performance: a high reversible capacity of nearly 130 mA h g⁻¹ over 50 cycles between 4.3 and 2.0 V; superior rate capability with specific capacities of nearly 74 and 57 mA h g⁻¹ at high current densities of 15C (1.92 A g⁻¹) and 30C (3.84 A g⁻¹), respectively; long-term cycle life with capacity retentions of 70% and 50% over 1000 and 3000 cycles at 10C and 30C rates. Thanks to the manifested high energy and power densities, the NVPF@C nanocomposite is suggested as a promising cathode material for grid energy storage.