Composite electrolyte membrane with continuous Na+ transport for high-performance quasi-solid-state sodium batteries

Composite polymer electrolytes (CPEs) have attracted wide attention because of their enormous potential to address the limitations of traditional liquid electrolytes. However, the inevitable aggregate and precipitate of inorganic filler in polymer electrolytes could lead low ionic conductivity , poor interfacial compatibility and mechanical property, which limited the application of CPEs for high energy density solid-sate batteries. Herein, a novel composite electrolyte membrane (Z-CPE@ZIF60) was achieved by impregnating ZIF-67 particles into a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and polyacrylonitrile (PAN) hybrid nanofibers membrane with continuous and interconnected 3D network via electrospinning and in situ photopolymerization strategy. Using this electrolyte membrane for quasi-solid-state sodium batteries, a high ionic conductivity of 1.42 × 10 −3  S cm −1 and outstanding Na + transference number of 0.58, and excellent mechanical properties was obtained at room temperature owing to continuous Na + conduction pathways in the interconnected 3D network with PVDF-HFP/PAN hybrid nanofibers, the Lewis acid-base interaction between anions and ZIF-67. In addition, the solid electrolyte interface film formed by the contact of PVDF-HFP and Na anode effectively suppressed the growth of sodium dendrites. As a result, symmetric Na cells exhibit a stable polarization for 600 h under 0.1 mA cm −2 , indicating outstanding Na stripping/plating reversibility. Furthermore, the quasi-solid-state sodium batteries Na 0.67 Ni 0.33 Mn 0.37 Ti 0.3 O 1.9 F 0.1 (NaNMTi 0.3 OF)/Z-CPE@ZIF60/Na displayed impressive rate and cycling performance.