Synthesis and characterization of iota-carrageenan biopolymer electrolyte with lithium perchlorate and succinonitrile (plasticizer)

A non-toxic and bio-active natural polymer electrolyte iota-carrageenan (i-carrageenan) with LiClO₄ has been prepared by conventional solution casting technique. Succinonitrile (SN) plastic crystal has been used as an additive to optimize the conductivity of i-carrageenan biopolymer electrolytes. The obtained biopolymer electrolytes are characterized by X-ray diffraction, Fourier-transform infrared, differential scanning calorimetry and AC impedance studies. The highest ionic conductivity at room temperature is 3.57 × 10⁻⁴ S cm⁻¹ for the film composition of 1.0 g i-carrageenan/0.5 wt% LiClO₄. The inclusion of 0.3 wt% of SN into this polymeric system has improved the value of ionic conductivity to 3.33 × 10⁻³ S cm⁻¹ at ambient temperature, and the activation energy is found to be very low for this concentration. Transference number analysis also reveals that the cause of conductivity is primarily due to ions with the highest ionic transference number of 0.92 (Wagner's method) and cationic transference number of 0.58 (Bruce and Vincent method) for the highest conducting plasticized sample. Transport parameters of diffusion coefficients and mobility of cations and anions are also in tune with the conductivity results. Linear sweep voltammetry shows that the highest conducting sample is electrochemically stable up to 2.36 V without SN, and it is 3.1 V with SN addition. These results recommend the suitability of the fabricated polymer electrolyte for lithium ion battery system.