Sustainable recycling of polymer solid-state batteries – a mechanical-hydrometallurgical case study

Abstract

Polymer solid-state batteries (SSBs) are a promising next-generation energy storage technology critical to the energy transition and are already being used in the first electric vehicles. Unlike conventional lithium-ion batteries (LIBs) with liquid electrolytes, polymer SSBs contain different materials such as flexible polymers, metal anodes and composite cathodes, which influence the overall recyclability. However, the recycling of polymer SSBs remains underexplored, and current research is usually limited to individual components of the polymer SSB. Therefore, it remains unclear how polymer SSB full cells with higher material complexity affect the state-of-the-art recycling processes. Here, a novel mechanical-hydrometallurgical process flowsheet has been developed to recycle polymer SSBs. Unlike conventional LIBs, polymer SSBs do not yield a black mass fraction during mechanical recycling. However, optimized mechanical pre-treatment was essential for hydrometallurgical extraction of valuable components. An innovative salt leaching process using Cu(II) sulfate was developed for the safe aqueous recycling of Li metal anodes in polymer SSBs. Compared to conventional lixiviants, this salt-leaching approach based on cementation significantly decreased H₂ emissions by up to 91 %, thus improving operational safety by mitigating the risk of an explosive atmosphere. Additionally, Cu(II) sulfate leaching achieved high leaching efficiencies for Li, Fe, and P exceeding 96 %. After impurity removal by hydroxide precipitation, Li₃PO₄ recovery was demonstrated as a suitable candidate for LiFePO₄ resynthesis. Overall, a high cumulative Li recycling efficiency of 90 % was achieved. This novel process for recycling polymer SSBs anticipates robust, scalable, energy-efficient, and environmentally friendly processes, promoting a circular economy for the battery industry.