In this paper, we report the effect of doping sodium iodide (NaI) salt into a polymer blend matrix of sodium carboxymethyl cellulose (NaCMC) and poly(vinyl alcohol) (PVA). Solution casting approach was used to prepare solid polymer electrolyte (SPE) films. The films were characterized by Fourier-transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD), electrical impedance spectroscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). XRD showed that NaI incorporation decreased the crystallinity of NaCMC/PVA-based SPE. FTIR technique confirmed the complexation of salt with polymer matrix due to the formation of the coordination bond between Na⁺ and –OH group and hydrogen bond between I⁻ and –CH group. The sample with 30 wt% NaI showed the highest conductivity of 2.52 × 10^–3 S cm⁻¹, strongly influenced by the highest charge concentration $$(n)$$( n ) , not its mobility (μ). DSC analysis revealed an increase in glass transition temperature $$({T}_{g})$$( T g ) with increasing salt content. TGA studies showed a decrease in thermal stability with salt inclusion. The transference number was found to be 0.99 for the highest conducting sample showing the primary charge carriers are ions. The highest conducting sample exhibited a mechanical strength of 15.42 MPa at room temperature, and it has been used to fabricate a battery to evaluate its suitability in energy storage devices. Graphical abstract Graphical abstract created with https://biorender.com.

Na⁺ ion-conducting solid polymer electrolyte (SPE) of sodium salt of carboxymethyl cellulose (NaCMC) doped with sodium nitrate (NaNO₃) was developed by solution casting method. FTIR technique confirmed the formation of hydrogen bonding between $$ {NO}_3^{-} $$NO 3 − anion and functional groups of NaCMC. XRD study revealed the low degree of crystallinity that reduced upon doping. Impedance spectroscopy was adapted in order to analyze the conductivity and dielectric relaxation phenomena of the polymer-salt complex. FTIR deconvolution technique was employed to understand the factor that influences the ionic conductivity in SPE; concentration of mobile ions and ionic mobility both play a vital role. Ion transference number has been found out to be > 0.97 for all samples indicating that the conducting species are primarily ions. The highest ionic conductivity of ̴ 3 × 10⁻³ Scm⁻¹ with the mechanical strength of 30.12 MPa was achieved for a host containing 30 wt.% NaNO₃ at ambient temperature.

Biodegradable ion conducting solid polymer electrolyte films of carboxymethyl cellulose (CMC) doped with sodium bromide (NaBr) with various weight percentages were prepared by a solution casting technique. Their structural, optical and electrical properties were studied by various experimental techniques in order to understand the impact of the sodium metal salt on the biopolymer CMC’s properties. The optical parameters namely the optical bandgap energy and the refractive index, showed a significant variable variation with the metal salt concentration. The maximum dc conductivity was found to be ∼5.15 × 10⁻⁴ S cm⁻¹ at room temperature for the sample with 20 wt% of NaBr content in the CMC matrix. The ionic conductivity and dielectric constant in general, increased with increase in metal salt content, affirming the increase in ion concentration. The calculated transference number showed that the conductivity was mainly due to ions. The increase in conductivity was due to an increase in degree of amorphousness of the polymer upon doping, as analyzed by their XRD spectra.

In this study, different weight percentages of Mg(NO₃)₂were added to a polymer blend composed of chitosan (CS) and methylcellulose (MC). The solution casting method was adopted to prepare the polymer electrolyte films. As the host matrix, the polymer blend consists of 70 wt.% of CS and 30 wt.% of MC. The interactions between the blend and the Mg(NO₃)₂salt were revealed by FTIR analysis. The deconvolution of XRD peaks followed by the calculation of crystallinity indicates that the electrolyte samples were amorphous. The bulk resistance decreased with increasing salt content, according to the results of electrical impedance spectroscopy (EIS), and this was caused by the influence of carrier concentration. The sample containing 30 wt.% of Mg(NO₃)₂was determined to have a maximum value of DC conductivity of 2.12 × 10^–5Scm⁻¹at room temperature by EIS analysis. The highest conducting film’s potential stability was found to be 3.65 V. It was found that the ion transference number was 0.86. The performance of the magnesium ion battery was then evaluated after it was built using the highest conducting polymer electrolyte. Considering this, the current work proposes an eco-friendly, practical, and affordable electrolyte appropriate for making electrochemical devices.Graphical abstract (made with biorender.com)