In this study, we report the synthesis of sodium iron silicate (Na₂FeSiO₄) as a cathode material for Na-ion batteries for the first time using fast and highly scalable urea combustion technique. In the present work, different combustion reactions using various fuels are carried out. The fuel of urea provides enough energy/flame temperature to the reaction to achieve orthorhombic phase of Na₂FeSiO₄ (NFS) with C222₁ space group. Further, the amounts of sodium precursors and urea are optimized by performing the different combustion reactions at a fixed stoichiometric ratio (Sr) of 0.23. The structure, microstructural and elemental analysis are studied by XRD, FESEM, XPS, FTIR and BET characterizations. The electrochemical performance of NFS is studied in the different voltage windows, where NFS cathode exhibits high irreversible capacity loss during initial cycle in the voltage window of 1.5–4.5 V. Results show that growth of the SEI layer is upper cut-off voltage dependent. For instance, nano-NFS cathode shows almost negligible capacity loss during first cycle as the upper cut-off voltage decreases to 4.3 V. EIS studies show the continuous increase of interfacial resistance during first charge/discharge process probably due to concentration polarisation at solid/liquid interface suggesting the sluggish kinetics of Na⁺ ions at the electrode/electrolyte interface. Furthermore, ex-situ XRD and FTIR techniques are used to understand the interfacial resistance growth mechanism. The Na-ion diffusion coefficient calculation also compliments the impedance data and indicate the sluggish Na-ion movement in pristine NFS. The results do indicate that pure NFS, due to poor kinetics of Na-ion despite its nanophase and mesoporous nature, is not found suitable as high performing cathode material.

在这项研究中，我们首次报道了使用快速且高度可扩展的尿素燃烧技术合成硅酸铁钠 (Na ₂ FeSiO ₄ ) 作为钠离子电池的阴极材料。在目前的工作中，使用各种燃料进行不同的燃烧反应。尿素燃料为反应提供足够的能量/火焰温度以实现 Na ₂ FeSiO ₄ (NFS) 与 C222 _{1 的}正交相空间群。此外，通过以 0.23 的固定化学计量比 (Sr) 进行不同的燃烧反应来优化钠前体和尿素的量。通过 XRD、FESEM、XPS、FTIR 和 BET 表征研究了结构、微观结构和元素分析。在不同的电压窗口中研究了 NFS 的电化学性能，其中 NFS 阴极在 1.5-4.5 V 的电压窗口内在初始循环期间表现出高的不可逆容量损失。结果表明 SEI 层的生长取决于上限截止电压。例如，当上限截止电压降至 4.3 V 时，纳米 NFS 阴极在第一次循环期间的容量损失几乎可以忽略不计。⁺离子在电极/电解质界面。此外，异位 XRD 和 FTIR 技术用于了解界面电阻增长机制。钠离子扩散系数计算还补充了阻抗数据，并表明原始 NFS 中钠离子运动缓慢。结果确实表明，尽管钠离子具有纳米相和介孔性质，但由于钠离子的动力学较差，因此发现纯 NFS 不适合作为高性能阴极材料。