Amelioration of ionic conductivity (303 K) with the supplement of MnO2 filler in the chitosan biopolymer electrolyte for magnesium batteries

Abstract

In the present work, the significance of adding MnO2 filler towards the development of biopolymer electrolyte and chitosan with enhanced ionic conductivity has been reported. The complexation that has been taken place with the inclusion of MgNO3.6H2O salt and MnO2 filler in the chitosan matrix has been investigated through the Fourier transform infrared (FTIR) spectra analysis. Further, the transport parameter values such as number of charge carrier densities (n), mobility (μ) and diffusion coefficient (D) have been calculated from the deconvoluted FTIR spectra. X-Ray diffraction (XRD) and differential scanning calorimetric (DSC) examination revealed that the inclusion of filler significantly reduced the degree of crystallinity and the glass transition Tg values, respectively. These findings show that the inclusion of filler increases the segmental mobility of the polymer chains, allowing for faster ion transport. The conduction properties of the prepared electrolytes have been determined using alternating current (AC) impedance analysis, with the electrolyte containing 60 wt% magnesium salt (2.6 ± 0.08) × 10−4 S cm−1 achieving the maximum ionic conductivity value at room temperature (303 K). This value is further increased by one order of magnitude with the addition of MnO2 filler into the polymer matrix (1.25 ± 0.09) × 10−3 S cm−1. To elucidate the individual contributions of ions and electrons in the conduction process, the direct current (DC) polarization method has been used to determine the transference number (tion) of the produced electrolytes. The filler-added chitosan polymer exhibits an extended electrochemical stability window, 1.7 V, as determined by linear sweep voltammetry (LSV).