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Study on NH4I composition effect in agar–agar-based biopolymer electrolyte


Solid polymer electrolytes (SPE) are regarded as key components in electrochemical devices since the ionic conduction has a strong influence on the devices’ performance. Proton-conducting SPEs have been recognized for their suitability in the application of electrochemical devices. Solid polymer electrolytes synthesized with natural polymers have been used as polymer host due to their variant structure, richness in nature, and they are economical and biodegradable. Agar–agar, a biopolymer, extracted from red algae, is used as gelling, stabilizing and encapsulating agent in pharmaceutical and biotechnological industries. It is a mixture of polysaccharides—85% of agarose, a neutral polymer, and 15% of agaropectin, a charged sulphated polymer. It has good film-forming tendency. In the present study, proton-conducting biopolymer electrolytes containing agar and ammonium iodide (NH4I) were prepared by solution casting technique. Fourier-transformed infrared (FTIR) spectroscopy results revealed that the complexation between agar and NH4I has occurred. X-ray diffraction (XRD) studies demonstrate the amorphous nature of salted biopolymer electrolytes. It has been found that the film of composition 50 mol% agar:50 mol% NH4I is more amorphous than other samples. The ionic conductivity of the prepared polymer electrolytes is found by AC impedance spectroscopy analysis. The maximum ionic conductivity is 1.17 × 10−4 S cm−1 at ambient temperature for the film of composition 50 mol% agar: 50 mol% NH4I. All electrolytes exhibit Arrhenius behaviour. The frequency dependence of dielectric and electric modulus of agar–ammonium iodide (NH4I) polymer electrolyte is investigated.

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Correspondence to T. Mathavan.

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Selvalakshmi, S., Mathavan, T., Selvasekarapandian, S. et al. Study on NH4I composition effect in agar–agar-based biopolymer electrolyte. Ionics 23, 2791–2797 (2017).

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  • Biodegradable polymer
  • Proton conducting
  • Dielectric