Charging toward sustainability: MgCl2 doped chitosan–dextran polyblend electrolytes for energy storage device applications

Abstract

In this study, chitosan (CS), dextran (DN), and magnesium chloride (MgCl₂) salt-based soild blend polymer electrolyte (SBPE) membranes that conduct Mg²⁺ ions have been developed. XRD revealed changes in the microstructure by incorporating MgCl₂ salt into the polymer host due to polyblend–ion interaction, verified by Fourier transform infrared spectroscopy. At room temperature, the electrolyte membrane containing 30 wt% MgCl₂ reached an ionic conductivity of 1.79 × 10⁻⁵ S cm⁻¹. An ion transference number (t_ion) of about 0.73 was achieved for 30 wt% of magnesium salt, suggesting the dominance of ion conduction in the SBPE sample. The SBPE membrane with the highest ion conductivity demonstrated an electrochemical stability window (ESW) of 2.66 V. Thermal degradation of the SBPE is influenced by the amount of salt incorporated in the poly-blend matrix as per TGA analysis. The discharge behaviour patterns of magnesium ion cells using the Mg|(CS + DN + MgCl₂)|cathode setup were investigated with two distinct cathode materials. Moreover, the fabricated electrochemical double-layer capacitor (EDLC) showed non-faradaic behaviour in cyclic voltammetry (CV) studies with the specific capacitance of 36 F g⁻¹ at 5 mV s⁻¹. An environmentally friendly, biodegradable, and economically viable electrolyte that can effectively serve as a separator and electrolyte in devices such as magnesium-ion batteries and EDLCs has been investigated in this work.