Research progress on sodium-ion batteries based on iron-based sulfate cathode materials

In recent years, lithium resources’ scarcity and uneven distribution have become increasingly prominent, leading to a growing interest in sodium-ion batteries due to their abundant raw materials and low cost. In the sodium-ion battery system, the performance of the positive electrode material plays a significant role in determining the battery’s energy density and manufacturing cost. Therefore, developing positive electrode materials with high energy density, high safety, and low cost is particularly important. Iron-based sulfate anode materials have attracted considerable attention due to their abundant resources, low cost, and high operating voltage. This article provided a comprehensive summary of the characteristics and research progress of iron-based sulfate cathode materials, with a specific focus on the alluaudite-type Na_2+2xFe_2-x(SO₄)₃, which possesses a stable framework structure and an operating voltage of approximately 3.8 V, making it regarded as a particularly promising high-performance positive electrode material. Furthermore, the article compared the physicochemical properties and electrochemical performance of samples synthesized using different methods, aiming to elucidate the key factors influencing material performance by summarizing and analyzing these relationships. Finally, the article discussed the main challenges faced by iron-based sulfate anodes and summarizes performance optimization strategies.