Designing Na₂Zn₂TeO₆-Embedded 3D-Nanofibrous Poly(vinylidenefluoride)-co-hexafluoropropylene-Based Nanohybrid Electrolyte via Electrospinning for Durable Sodium-Ion Capacitors

A novel solid-state electrospun nanohybrid polymer membrane electrolyte (esHPME) for sodium-ion capacitors to improve the ionic conductivity and energy density is demonstrated. A Na2Zn2TeO6 (NZTO)-embedded 3D-nanofibrous poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanohybrid electrolyte has been reported as a high-sodium-ion conducting electrolyte for sodium-ion capacitor applications. PVDF-HFP based esHPMEs with different loadings (0, 5, 10, and 15 wt %) of NZTO nanoparticles are prepared by electrospinning and further activated by soaking them in a liquid electrolyte (1M of NaPF6 in EC/DMC, 1:1 v/v) to employ as the electrolyte-separator. Among the prepared esHPMEs, the 10 wt % NZTO-embedded esHPME exhibits the maximum ionic conductivity and electrochemical window of 2.5 V. The influence of hybridization between inorganic nanoparticles (NZTO) and the organic polymer (PVDF-HFP) is investigated by physical characterization and their electrochemical performance. A coin cell-type Na-ion supercapacitor is fabricated using battery-type Na0.67Co0.7Al0.3O2 as the anode and activated carbon as the cathode. The fabricated Na-ion supercapacitor [Na0.67Co0.7Al0.3O2/esHPME (10 wt % NZTO)/AC] delivered an energy density of 99.375 F g–1 at 1 A g–1 current density and exhibits 84% of capacity retention up to 1000 cycles of charge discharging. The Na-ion capacitor showed a maximum energy density and power density of 35.33 W h kg–1 and 1.6 kW kg–1, respectively. Thus, the present work demonstrates the great potential of the electrospun PVDF-HFP/NZTO-based nanohybrid membrane electrolyte for durable Na-ion capacitors.