Advancing sodium-ion batteries toward commercialization: A review on phosphate and sulfate-based polyanionic cathodes

Abstract

Sodium-ion batteries (SIBs) are considered as a promising supplement to lithium-ion batteries for large-scale energy storage applications due to the abundance and cost-effectiveness of sodium resources. Among various cathode materials, polyanionic compounds, particularly phosphate and sulfate-based ones, have garnered significant attention for their good structural stability, high redox potentials, and favorable Na⁺x002B diffusion channels. However, challenges such as low electronic conductivity, limited capacity, and complex synthesis procedures hinder their widespread application. This review starts with the key characteristics of polyanionic materials, followed by a thorough summary of recent advancements in phosphate and sulfate-based cathodes, emphasizing their crystal structures, electrochemical properties, and sodium storage mechanisms. Then, the preparation methods and advanced modification strategies, including surface coating, particle size engineering, morphology and interface design, and element doping, are reviewed in detail. By systematically comparing phosphates and sulfates, this review integrates their commercialization progress and application scenarios from an industry-oriented perspective. This highlights the importance of industry-academia collaboration in accelerating the transition of polyanionic cathode materials from laboratory research to practical applications. Finally, future research directions and innovative approaches are proposed to overcome existing challenges, paving the way for the practical deployment of these materials in next-generation sustainable energy storage systems.