Role of Mg(NO3)2 as Defective Agent in Ameliorating the Electrical Conductivity, Structural and Electrochemical Properties of Agarose–Based Polymer Electrolytes

Abstract

Polymer electrolytes based on agarose dissolved in DMSO solvent complexed with different weight percentages of Mg(NO3)2 ranging from 0 to 35 wt% were prepared using a solution casting method. Electrochemical impedance spectroscopy (EIS) was applied to study the electrical properties of this polymer electrolyte, such as ionic conductivity at room and different temperatures, dielectric and modulus properties. The highest conducting film has been obtained at 1.48 × 10−5 S·cm−1 by doping 30 wt% of Mg(NO3)2 into the polymer matrix at room temperature. This high ionic conductivity value is achieved due to the increase in the amorphous nature of the polymer electrolyte, as proven by X-ray diffractometry (XRD), where broadening of the amorphous peak can be observed. The intermolecular interactions between agarose and Mg(NO3)2 are studied by Fourier transform infrared (FTIR) spectroscopy by observing the presence of –OH, –CH, N–H, CH3, C–O–C, C–OH, C–C and 3,6-anhydrogalactose bridges in the FTIR spectra. The electrochemical properties for the highest conducting agarose–Mg(NO3)2 polymer electrolyte are stable up to 3.57 V, which is determined by using linear sweep voltammetry (LSV) and supported by cyclic voltammetry (CV) that proves the presence of Mg2+ conduction.

The High-Performance Polymer Electrolytes Based on Agarose–Mg(ClO4)2 for Application in Electrochemical Energy Storage Devices

“…This proves that agarose-based polymer electrolytes possess mechanical strength and conductivity that is liquid-like [7]. These elucidations were confirmed as Ali et al, [8] recorded an exhibition of 1.48 × 10 -5 S•cm -1 value in ionic conductivity in their study, where agarose was used as a polymer matrix. Another research related to agarose-based biopolymer electrolytes was done by Singh and the team (2017), which reported the production of a high ionic conductivity value of about 7.41 × 10 -3 S•cm -1 with the addition of 1-ethyl-3-methylimidazolium dicyanamide (EMImDCA) in the composition.…”

“…Incorporating Mg(ClO4)2 into the agarose matrix exhibits a wide potential window and higher electrochemical stability up to 3.48 V and 3.65 V, respectively. These values were marked a reasonable range (>3V) for electrochemical applications in magnesium batteries [8,22,41].…”

“…Therefore, the value of activation energy recorded for the highest conducting sample (30-Mg(ClO4)2) is the lowest, about 0.105 eV, as displayed in Table 2, which reveals the small energy required for the charge carrier to participate in the conduction process. The samples that have low ionic conductivity, such as 25-Mg(ClO4)2 and 35-Mg(ClO4)2, exhibit much higher activation energy (0.123 eV and 0.158 eV, respectively) explained that high energy needed for the free ion to hopping to another coordinating site in agarose-Mg(ClO4)2 polymer electrolyte [8].…”

“…Moreover, the speciality of Mg 2+ salt consists of divalent ions that can exhibit a promising ionic conductivity as it is strongly attracted by the lone pair of oxygen atoms, which promotes salt dissociation and contributes to the transportation of ions [11,17]. The primary reason for the incorporation of magnesium salt polymer matrix is due to the ability of magnesium salt to form a stable ionic bond, which has a small cation size and high lattice energy that results from the strong ion-dipole interaction between the polymer [8,18]. Therefore, magnesium perchlorate (Mg(ClO4)2) has been chosen as a dopant to be infused in an agarose-based polymer electrolyte.…”

Recent Research Progress on All-Solid-State Mg Batteries

“…Natural polymers are also used as host polymers for Mg 2+ ion conductive SPEs [89][90][91][92][93][94][95][96][97][98][99][100][101][102][103][104]. Natural polymers are attractive in terms of environmental friendliness and resource abundance.…”