Na3V2(PO4)2F3@V2O5-x复合材料的制备及储钠性能研究

当前制约钠离子电池发展的主要因素包括较低的能量/功率密度和较差的循环性能, 而在正极材料表面包覆含氧缺陷金属氧化物层, 可以有效提高材料的电子导电率, 保证高振实密度、能量密度和功率密度。本文通过温和的溶剂热反应制备Na₃V₂(PO₄)₂F₃纳米片前驱体并结合高温煅烧合成Na₃V₂(PO₄)₂F₃@V₂O_5-x复合材料。其结构通过XRD、TEM、SEM、XPS和TGA测试进行表征。作为钠离子电池的正极材料, 展现了优异的循环性能和倍率性能。在0.2C倍率下, 首圈放电比容量为123 mAh?g ^-1, 循环140圈后容量保持在109 mAh?g ^-1。当电流密度提高至1C, 首圈放电比容量达到72 mAh?g ^-1, 充放电循环500圈后, 容量保持率高达84%。优异的电化学性能归因于材料表面包覆的具有丰富结构缺陷的无定型层, 有效提高了离子的扩散和电子导电率。此方法将有助于钠离子电池的实际应用。

Synthesis of Na3V2(PO4)2F3@V2O5-x as Cathode Material for Sodium-ion Battery

Low energy/power density and inferior cycling stability are bottlenecks to restrict the applications of sodium-ion batteries. Recently, coating the surface of cathode material by metal oxides containing oxygen vacancies, was regarded as an effective strategy to improve electrical conductivity and power/energy density. In this study, Na₃V₂(PO₄)₂F₃@V₂O_5-x nanosheets were synthesized via hydrothermal strategy followed by heat treatment. X-ray diffraction, transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis were applied to investigate the structure of Na₃V₂(PO₄)₂F₃@V₂O_5-x. As a cathode of sodium- ion batteries, Na₃V₂(PO₄)₂F₃@V₂O_5-x delivers excellent cycling stability and rate capability. It exhibits an initial discharge capacity of 123 mAh?g ^-1 at 0.2C, and a discharge capacity of 109 mAh?g ^-1 after 140 cycles. At 1C, its initial reversible capacity is 72 mAh?g ^-1, which remains 84% after 500 cycles. The outstanding electrochemical property could be ascribed to its enhanced sodium-diffusion and improved electronic conductivity induced by disordered surface coating. Furthermore, it encourages more investigations into practical sodium-ion battery applications.