Gel Polymer Electrolyte Membranes Boosted with Sodium-Conductive β-Alumina Nanoparticles: Application for Na-Ion Batteries

Electrolytes, the crucial and indispensable component of a battery system, dominate the interfacial chemistry and the overall performances of the battery. In this work, a poly(vinylidene fluoride-co-hexafluoropropylene)/poly(methyl methacrylate)-based gel polymer electrolyte (GPE) membrane containing sodium-conductive β-alumina nanoparticles is synthesized. The resultant electrolyte membrane's performances can be boosted remarkably by the presence of β-alumina nanoparticles through decreasing the degree of crystallinity and improving Na-ion transference number, eventually enhancing the ionic conductivity. The GPE membrane embedded with a suitable amount of β-alumina nanoparticles delivers a high ionic conductivity of 2.39 × 10–3 S cm–1 and a wide electrochemical stability window at 5.04 V. The assembled Na3V2(PO4)3/GPE/Na cell has promising electrochemical performances with an initial discharge capacity of 94.1 mA h·g–1 and a capacity retention of 85% after 300 cycles at 0.5 C. This work proves that the addition of sodium conductors, similar to the presented β-alumina, could enhance the performances of GPE membranes, promoting the rapid development of rechargeable sodium-ion batteries.