MXene-enhanced PEGDA crosslinked quasi-solid electrolytes: a flame-retardant 3D network for high-performance sodium-ion batteries

Abstract

Semi-solid polymer electrolytes (SPEs) play a pivotal role in the development of high-performance sodium-ion batteries (SIBs) by providing benefits such as enhanced safety, flexibility, and high ionic conductivity. However, traditional SPEs face challenges including poor mechanical strength, limited ionic conductivity, and insufficient electrochemical stability. Furthermore, safety concerns arising from flammability and dendrite growth significantly limit their practical applications. In this study, a novel quasi-solid electrolyte (QSE) is developed by incorporating MXene nanosheets into a polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) matrix through UV-initiated in situ polymerization of poly(ethylene glycol) diacrylate (PEGDA) monomers, forming a 3D interconnected MXene–P(PEGDA)–PVDF–HFP composite structure. The integration of MXene enhances both ionic conductivity and Na⁺ mobility, while simultaneously improving the electrolyte's flame retardancy and thermal stability. The QSE-1.5M (with 1.5 wt% MXene) demonstrates an ionic conductivity of 1.01 × 10⁻³ S cm⁻¹ at 30 °C, and the NVP‖QSE-1.5M‖Na half-cell exhibits a high initial discharge capacity of 105.5 mAh g⁻¹ at 2C, with 90.1% capacity retention after 2500 cycles and an average coulombic efficiency exceeding 99%. The full cell configuration, NVP‖QSE-1.5M‖HC, delivers stable cycling performance for over 3000 cycles at 3C, maintaining a capacity retention of 84.5%, with a reversible capacity of approximately 100 mAh g⁻¹ at 10C. Moreover, QSE-1.5M exhibits superior thermal stability with a high decomposition temperature and a reduced heat release rate. The combustion test further highlights its self-extinguishing capability within 0.01 s, confirming excellent flame retardancy. These improvements, coupled with effective dendrite suppression, position QSE-1.5M as a promising candidate for high-safety, long-cycle-life SIBs. This work demonstrates the potential of MXene-enhanced PEGDA-based QSEs in advancing both the performance and safety of SIBs, paving the way for more efficient and secure energy storage systems.