Alginate-based separators for sustainable energy storage devices

The separator is a crucial component of batteries, as it prevents electrical short circuits by acting as a physical barrier between anode and cathode. Nonetheless, it allows ion transport closing the circuit. Traditional polyolefin-based separators are widely used in lithium-ion technologies due to their affordability and chemical stability. However, their high stability results in high resistance to biodegradation. To address this issue, the adoption of biobased separators is necessary. In this work, three different alginate-based separators are proposed for application in both organic and aqueous systems. Sodium alginate and calcium alginate were selected as lowcost, biodegradable natural polymers with excellent thermal and chemical stability. A sustainable preparation route was designed based on the phase inversion technique, using water and ethanol as solvents. After assessing the materials thermal stability, physical insights were gained by evaluating the separators mechanical stability, morphology and affinity with both organic and aqueous electrolyte. Finally, electrochemical tests were performed in lithium metal cells, as well as in supercapacitor, to evaluate the performance of the alginate-based separators.