High-temperature performance investigation of adiponitrile-based electrolytes for sodium-ion batteries

Abstract

Sodium-ion batteries (SIBs) are increasingly used in large-scale energy storage and electric vehicles due to abundant resources, low cost, high safety and good temperature adaptability. However, in high-temperature environments, electrolyte decomposition, interfacial side reactions and poor electrode–electrolyte compatibility cause serious deficiencies in battery performance and cycle life. Moreover, reports on high-temperature SIB electrolytes are extremely scarce, so developing high-temperature electrolytes with high thermal stability and excellent interfacial compatibility is vital for promoting SIBs' high-temperature applications. This study used adiponitrile (ADN) with high flash point and high boiling point as a co-solvent to design carbonate (ethylene carbonate(EC), propylene carbonate(PC))-based electrolytes. Among them, the EC : ADN binary hybrid system performs the best. At 60 °C, the Na₄Fe₃(PO₄)₂P₂O₇(NFPP)-based SIB coin half-cell achieved 100.1 mAh g⁻¹ discharge capacity at 0.1C (17.76% higher than at 25 °C), 85.4 mAh g⁻¹ at 5C, and 98.7% capacity retention after 100 cycles at 1C. ADN stabilizes Na⁺ solvation sheath via the formation of C–H⋯O/F non-classical hydrogen bonds and dipole–dipole interactions with FSI⁻, and preferentially decomposes to form a nitrogen-rich cathode electrolyte interface (CEI) film, inhibiting high-temperature side reactions. As a co-solvent, ADN enables the CEI film to gain appropriate Na₃N decomposition products, enhancing its mechanical stability and ionic conductivity. This study provides a new strategy and technical support for solving high-temperature SIB performance degradation.