Powering the future: advances, challenges, and sustainability of polymer electrolytes in lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries offer a transformative theoretical energy density (∼2600 Wh kg^-1), positioning them as strong candidates for next-generation energy storage systems supporting the global shift toward renewable energy integration and electrified transportation. However, their commercial viability is hindered by challenges such as the polysulfide shuttle effect and safety concerns related to volatile liquid electrolytes. Polymer-based solid-state electrolytes present a compelling pathway to overcome these barriers, offering improved safety, processability, and design flexibility. This review critically examines recent advancements in polymer electrolytes for Li-S batteries, with a particular focus on nanoscale strategies to enhance ionic conductivity, electrochemical stability, and electrode-electrolyte interfacial compatibility. Special attention is paid to nanostructured polymer matrices, functional nanofillers, and interfacial engineering techniques. This review also explores emerging directions, including the development of adaptive "smart" electrolytes and the integration of machine learning for rational materials design. Finally, the environmental and sustainability profiles of polymer-based Li-S batteries are compared with those of conventional lithium-ion systems, considering life cycle aspects such as raw material sourcing, fabrication energy intensity, and global warming potential. This review aims to bridge the gap between nanoscale innovation and macroscopic energy challenges, highlighting the potential of polymer electrolytes to enable scalable, safe, and sustainable Li-S battery technologies.