On the Use of Recycled PVB to Develop Sustainable Separators for Greener Li‐Ion Batteries

Abstract In this work, sustainable Li‐based battery separators are prepared starting from a waste material from the glass industry, viz. polyvinyl butyral (PVB) widely used as a sacrificial interlayer in high impact‐resistant windows. First, polymeric membranes are prepared via the phase‐inversion method using commercial PVB as the backbone and 4,4′‐methylenebis(cyclohexylisocyanate) as a crosslinking agent. They are characterized from a physicochemical viewpoint by thermomechanical analysis, infrared spectroscopy, and scanning electron microscopy, and are successfully tested as separators in Li‐metal cells with LP30 electrolyte. Electrical and electrochemical properties are evaluated by impedance spectroscopy and galvanostatic cycling, providing comparable results with commercial Celgard 25 µm monolayer microporous polypropylene separator. As a proof‐of‐concept, for the first time, recycled PVB‐based polymer membranes from wasted car glasses are prepared, adjusting the synthesis protocol to account for the presence of plasticizers and contaminants. They show a dense elastomeric appearance and proved to be compatible with Li metal and stable upon 600 h of Li plating/stripping. The electrochemical window is compatible with the LiFePO₄ cathode, as demonstrated by prolonged galvanostatic cycling (250 cycles) in laboratory‐scale cells. Preliminary results are highly encouraging and pave the way to developing novel separators for safe, low‐cost, and sustainable energy storage devices.