A04-0580 - Na3Zr2Si2PO12-Polymer Hybrid Composites for Solid-State Supercapacitor Applications

Abstract

Various Na+ ions conducting composite polymer electrolytes have been developed in last three decades, but their application is limited due to poor ionic conductivity near room temperature. Recently, we have demonstrated high ionic conductivity of ∼ 10-4 Ω-1cm-1 in NASICON-polymer hybrids and found these systems useful in energy storage applications. A high ionic mobility of ~ 10-1 cm2/V-s was also reported. Present work shows a possible application of these hybrids as electrolyte/separator in all-solid-state supercapacitor.

In this work, Na+ NASICON, viz. Na3Zr2Si2PO12 (NZSP) have been prepared by conventional solid state reaction route. Subsequently, their nanoparticles of size ~ 30 nm were obtained via mechanical ball milling. The nanoparticles were mixed with polymer in a ball mill until a homogeneous viscous slurry formation. Further the slurry was dried, hot pressed at ~ 80°C to obtain films of uniform thickness ~ 250µm. This way, composite films with composition (wt%) 10NaI-90(PEO1-xNZSPx), where 0 ≤ x ≤ 0.4, were obtained. Surface morphology, structural and thermal analysis were characterized using FESEM, XRD and DSC. A maximum ionic conductivity of ~ 4 x 10-5 Ω-1cm-1 at room temperature has been achieved for composite with x = 0.4. Impedance spectroscopy was used to understand mechanism of ionic transport. Further, to understand the role of ceramic fillers in enhancing the ionic conductivity, local structure of the composites was studied using x-ray absorption near edge structure spectroscopy (XANES) at Indus II Beamline 01, RRCAT, Indore. These results suggest a significant role of NASICON in providing pathways for Na+ ion transport.

The ionic conductivity at room temperature for composite with x = 0.4 were further modified with EMITf and EC+PC as plasticizer. A maximum ionic conductivity of ~ 2 x 10-4 Ω-1cm-1 at room temperature has been achieved with addition of 2 wt% of EMITf in the composite. To elucidate the capacity of these electrolyte as a membrane for all solid-state ionic devices, solid state super capacitors (configuration C|CPE|C) were fabricated. These composites have been found to be competitive candidates for energy storage. A maximum specific capacitance of ~ 26 F-g-1 is obtained for composite with 2 wt% EMITf at room temperature.