@PHDTHESIS{ 2025:2003785625,
 	title = {Understanding the lithium salts effects on PVA-based membranes from an experimental vision for solid-state electrolytes},
 	year = {2025},
 	url = "https://tede.ufam.edu.br/handle/tede/11203",
 	abstract = "The growing demand for safer, more stable, and efficient energy storage devices has driven the development of solid polymer electrolytes, which can enhance both the performance and safety of modern batteries. In this context, the present work aims to investigate the influence of different concentrations of ionic salts on poly(vinyl alcohol) (PVA)-based polymer membranes, aiming at their use in this application. PVA membranes with the addition of lithium hydroxide (LiOH) at concentrations 1, 3, 5, 7, and 9% and lithium perchlorate (LiClO4) at concentrations 1, 5, and 10% were prepared using the solvent casting method (SCM) and characterized with respect to their structural, morphological, thermal, mechanical, and ionic properties. Fourier transform infrared (FT-IR) spectroscopy indicated interactions between Li+ ions and the polymer matrix, as confirmed by density functional theory (DFT) calculations, which revealed a strong ionic coordination mechanism with formation energies of –1.27 eV and Li–O bond lengths ranging from 1.85 Å to 1.96 Å, depending on the increasing salt content. Complementarily, X-ray diffraction (XRD) revealed a monoclinic phase (space group P21/m) and crystallinities close to 30%, classifying the materials as semicrystalline. Thermal characterization by thermogravimetric analysis and differential scanning calorimetry (TGA/DSC) showed good correlation with the XRD data, in addition to increased transition temperatures, reaching Tg = 84.3 °C, Tm = 199.5 °C, and TD = 299 °C for up to 9% LiOH and 5% LiClO4, with a decrease observed only in the sample containing 10% perchlorate. Scanning electron microscopy (SEM) images revealed smooth surfaces and signs of internal stress at high salt concentrations, particularly with LiClO4, prompting the evaluation of mechanical performance by dynamic mechanical analysis (DMA) and tensile testing, which showed storage modulus values in the MPa range and elongation above 300%, indicating good flexibility and structural integrity.Additionally, ionic transport properties were investigated by complex impedance spectroscopy (CIS), with analysis based on equivalent circuit models, the Havriliak–Negami function, and Jonscher’s power law. Both systems exhibited improvements in ionic conductivity, with values on the order of 10−6 S/cm and 10−5 S/cm, and relaxation times of 10−5 s. These results demonstrate the potential of the membranes as promising candidates for solid electrolytes in advanced energy storage devices.",
 	publisher = {Universidade Federal do Amazonas},
 	scholl = {Programa de Pós-graduação em Física},
 	note = {Instituto de Ciências Exatas}
}