Title: Designing Solid Polymer Electrolytes for Lithium, Beyond Lithium, and a Sustainable Future

Abstract

As the demand for high-performance, sustainable energy storage systems intensifies, lithium-based battery technologies remain at the forefront due to their high energy density and technological maturity. However, to meet future challenges in safety, cost, and resource availability, there is a growing imperative to develop solid-state electrolytes that are not only optimized for lithium but also compatible with post-lithium chemistries. In particular, systems based on sodium offer long-term sustainability by relying on more earth-abundant and geopolitically stable raw materials. Equally important is the transition toward greener materials in battery components; in this context, bio-derived polymers such as peptides are emerging as promising building blocks for environmentally benign, tunable solid polymer electrolytes. In this colloquium, we present a macromolecular engineering approach to address a central challenge in solid polymer electrolytes (SPEs): the intrinsic trade-off between ionic conductivity and mechanical strength, as well as the critical role of cation chemistry and sustainable materials in governing electrolyte performance. We conclude presenting recent results on peptide-based electrolytes, whose structures offer unique opportunities for molecular-level control over ion transport and mechanical properties.