Binary Composite Solid Polymer Electrolyte with Enhanced Ionic Conductivity and Thermal Stability for Lithium-Sulfur Battery

In order to meet the energy demands of ongoing scientific and technological applications, it is imperative to advance the development of secondary battery systems that possess higher energy densities. The deployment of lithium-based technologies has been proposed as a means to address the present energy requirements due to the abundance, affordability, non-toxicity, and high energy density of their constituent materials. However, the energy density provided by conventional Li-ion batteries remains inadequate, which may lead to an inability to cope with future energy storage demands. The ideal temperature range for lithium-ion batteries to function is between -20°C and 60°C. Operating the battery outside the optimal temperature range leads to the deterioration of the electrolyte system and compromises the safety. Therefore, there is a need for an electrolyte system that exhibits enhanced ionic conductivity and can function at elevated temperatures. Llthium-sulfur (Li-S) batteries are considered a viable substitute for current Li-ion devices. This is due to their high theoretical specific capacity (1675 mAh.g^-1) and energy density (2600 Wh.kg^-1), and the cathode (S) is an earth-abundant, environmentally safe material [1]. Ether-based electrolytes are employed in the Li-ion battery system; despite the fact that these liquid electrolytes exhibit superior ionic conductivity, they are hindered by issues such as the polysulfide shuttle effect, inadequate mechanical and thermal stability, and flammability. Thus, safer electrolytes are needed and leading candidates are solid polymer electrolytes[2, 3]. In this work, a polymer electrolyte based on epoxidized natural rubber as host polymer and lithium bis(trifluoromethane) sulfonimide (LiTFSI) as electrolyte salt was developed and characterized. We report on Li-ion transport in composite polymer electrolytes (CPE) comprising High Entropy Oxide (HEO) particles incorporated into PEO/ENR:LiTFSI matrices in varying proportions. The HEO particles were synthesized throuh Sol-gel method. The system with 12% wt. load of HEO nanoparticles exhibited an ionic conductivity of 8.6 x 10^-4 S/cm at 30°C, which strongly increased at elevated temperatures. The electrolyte system remained stable at high temperatures (100°C) due to the presence of the ENR. This study suggests that the manipulation of polymer morphology through the use of filler particles holds great potential for advancing the development of composite polymer electrolytes[4]. The polymer blends employed enable operation at elevated temperatures on account of the high melting point and amorphous nature of the ENR constituent. The PEO-ENR-based polymer electrolyte systems provide a viable solution to address the drawbacks of traditional polymer electrolytes. This advancement opens up opportunities for the effective utilization of high-energy-density Li-S batteries in a wide range of applications, such as electric vehicles and stationary energy storage systems.<br/>References<br/>1. Choudhury, S., Saha, T., Naskar, K., Stamm, M., Heinrich, G., & Das, A. (2017). A highly stretchable gel-polymer electrolyte for lithium-sulfur batteries. <i>Polymer</i>, <i>112</i>, 447–456.<br/>2. Villa, A., Verduzco, J. C., Libera, J. A., & Marinero, E. E. (2021). Ionic conductivity optimization of composite polymer electrolytes through filler particle chemical modification. <i>Ionics</i>, <i>27</i>, 2483–2493.<br/>3. Schwanz, D. K., Villa, A., Balasubramanian, M., Helfrecht, B., & Marinero, E. E. (2020). Bi aliovalent substitution in Li7La3Zr2O12 garnets: Structural and ionic conductivity effects. <i>Aip Advances</i>, <i>10</i>(3).<br/>4. Praveen Balaji, T., & Choudhury, S. (2022). Separators for lithiumesulfur batteries. <i>Lithium-Sulfur Batteries: Materials, Challenges and Applications</i>, 121.