New technologies have been investigated to replace the use of lithium and cobalt ions, raw materials of the cathode active material of lithium-ion batteries. Among the emerging technologies stands out one that uses sodium (Na⁺) and iron ions. Sodium iron oxide (NaFeO₂) has polymorphism, with only the α phase being active for the reversible deintercalation of sodium ions, so this phase has potential application as an electroactive material in green sodium-ion batteries. The novel synthesis of α-sodium iron oxide through the sol–gel route, which provides a material with small particles and high crystallinity, is described in this work. Through X-ray diffraction and Rietveld refinement, it was found that the initial chelating agent/metals ratio affects the concentration of the α and β phases at the end of the synthetic route. The α-sodium iron oxide, obtained with an appropriate chelating agent/metals ratio, showed high purity and crystallinity. A discharge capacity of approximately 110 mAh/g was achieved when the α-sodium iron oxide electrode, obtained through the sol–gel route, was cycled from 1.00 to 4.00 V against sodium ions/sodium (Na), corresponding to the intercalation of approximately 0.5 sodium ions of the Na_1−x FeO₂ formula. The success of the synthesis of the α-sodium iron oxide phase can lower the cost and ensure the economic viability of green sodium-ion batteries.

中文翻译：

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绿色钠离子电池α-NaFeO2合成新路线

人们正在研究新技术来替代锂离子电池正极活性材料原材料锂和钴离子的使用。在新兴技术中，最引人注目的是使用钠 (Na ⁺ ) 和铁离子的技术。氧化铁钠（NaFeO ₂）具有多晶型，只有α相对钠离子的可逆脱嵌具有活性，因此该相具有作为绿色钠离子电池中电活性材料的潜在应用。这项工作描述了通过溶胶-凝胶途径合成α-钠铁氧化物的新方法，该方法提供了一种小颗粒和高结晶度的材料。通过X射线衍射和Rietveld精修，发现初始螯合剂/金属比影响合成路线末端α相和β相的浓度。采用适当的螯合剂/金属比例获得的α-氧化铁钠表现出高纯度和结晶度。当通过溶胶-凝胶途径获得的α-钠铁氧化物电极从1.00循环到4时，放电容量达到约110mAh/g。_{1− x} FeO ₂公式。α-钠铁氧化物相的成功合成可以降低成本并确保绿色钠离子电池的经济可行性。