Effect of Ethylene Sulfate Additive on the Stability and High‐Temperature Performance of Sodium‐Ion Batteries

Sodium‐ion batteries (SIBs) with P2‐type layered oxide cathodes and hard carbon anodes are attractive for electrochemical energy storage, due to the high theoretical capacity and cost‐effective synthesis. However, the practical application is hindered by rapid capacity decay during cycling, especially at elevated temperatures. Essentially, the cyclic performance mainly depends on the stability of electrode/electrolyte interfaces, which are closely related to the electrolyte additives. Therefore, in this study, ethylene sulfate (1,3,2‐dioxathiolane 2,2‐dioxide, DTD) is introduced as an electrolyte additive, and the P2‐type Na 0.64 Zn 0.05 Ni 0.29 Mn 0.56 Ti 0.11 O 2 ||hard carbon pouch cells with DTD‐containing electrolyte show excellent cycling stability at both 25°C (90.8% capacity retention after 1000 cycles at 1 C) and 45°C (95.4% retention after 100 cycles at 0.5 C). Meanwhile, the cells show enhanced capacity recovery after storage at 60°C. Density functional theory calculations combined with scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X‐ray photoelectron spectroscopy (XPS) characterizations demonstrate that DTD facilitates the formation of sulfur‐rich cathode electrolyte interphase and solid electrolyte interphase. This work demonstrates that the DTD additive is a promising strategy for simultaneously enhancing the thermal stability and cycling performance of SIBs.