In situ preparation of composite gel electrolytes with high room-temperature ionic conductivity and homogeneous Na+ flux for sodium metal batteries

Abstract

Gel polymer electrolytes (GPEs) are conceived to be a good way to build safer lithium/sodium metal batteries by substituting traditional liquid electrolytes. However, it is still very difficult for GPEs to simultaneously achieve high room-temperature ionic conductivity, uniform Na⁺ flow, superior interfacial compatibility, and increased mechanical strength. Herein, a composite gel electrolyte (KNT-PTGPE) with high ionic conductivity of 4.06 mS cm⁻¹ is prepared through chemical crosslinking strategy and the introduction of inorganic nanoparticles. The hybrid gel polymer network is formed by in situ cross-linking modified TiO₂ (KNT), three-armed trimethylolpropane trimethacrylate and poly(ethylene glycol) diacrylate. The resulting 3D interpenetrating network facilitates the absorption of liquid electrolytes and improves the mechanical properties of electrolyte. Theoretical calculation and in situ measurements reveal that the homogeneous TiO₂ fillers with abundant Lewis acid site and polymer network are involved in the solvation process of Na⁺, thus constructing a fast Na⁺ transport channel. Consequently, a stable plating/stripping process lasting over 900 h is achieved due to the uniform distribution of Na⁺ flux and the good mechanical properties of the electrolyte, and the assembled cell exhibits an excellent long-term cycling stability. The approach offers more opportunities to design GPEs for high performance SMBs.