Electrolyte additive strategies for prolonging the cycle life of sodium metal batteries

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Abstract Sodium metal batteries are considered promising next-generation energy storage systems due to their high theoretical capacity and low cost. However, the high reactivity between the sodium metal anode and the electrolyte, dendrite formation, and interfacial instability have severely hindered their practical applications. In this study, a ternary solvent system comprising ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1, supplemented with 5% fluoroethylene carbonate (FEC), was employed. Sodium perchlorate (NaClO4) was used as the conducting salt, and sodium fluorophosphate (FNa2O3P) was introduced as a functional additive to improve interfacial stability and battery performance. Electrochemical testing revealed that the incorporation of FNa2O3P significantly reduced the interfacial impedance at the anode, suppressed continuous electrolyte decomposition and sodium dendrite growth, and notably enhanced Coulombic efficiency and cycling stability. Compared with the control group without FNa2O3P, the proposed system exhibited a higher utilisation rate of sodium metal and superior long-term cycling performance. This work provides a novel approach for the development of high-performance and safe electrolytes for sodium metal batteries.

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