A Comprehensive Review on Iron-Based Sulfate Cathodes for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) are advantageous for large-scale energy storage due to the plentiful and ubiquitous nature of sodium resources, coupled with their lower cost relative to alternative technologies. To expedite the market adoption of SIBs, enhancing the energy density of SIBs is essential. Raising the operational voltage of the SIBs cathode is regarded as an effective strategy for achieving this goal, but it requires stable high-voltage cathode materials. Sodium iron sulfate (NFSO) is considered to be a promising cathode material due to its stable framework, adjustable structure, operational safety, and the high electronegativity of SO⁴⁻. This paper reviews the research progress of NFSO, discusses its structure and sodium storage mechanism on this basis, and summarizes the advantages and disadvantages of NFSO cathode materials. This study also evaluates the advancements in enhancing the electrochemical characteristics and structural reliability of SIBs, drawing on both domestic and international research. The findings of this paper offer valuable insights into the engineering and innovation of robust and viable SIB cathodes based on NFSO at ambient temperatures, contributing to their commercial viability.