Recycling-Regenerating Salt Enables the Economic Viability of Aqueous High-concentration Electrolytes

Abstract

The aqueous high-salt-concentrated electrolytes expand the electrochemical stability window (ESW), providing aqueous batteries with high output voltage and energy density. However, the increased salt concentration also raises costs, negatively affecting the economic feasibility for electric energy storage. Herein, we demonstrate that the aqueous highly concentrated lithium trifluoromethyl sulfonamide (LiTFSI) electrolytes are easy to recycle through salt extraction methods. Furthermore, to circumvent energy-intensive dehydration processes induced by LiTFSI hygroscopicity, we propose a direct regeneration protocol based on concentration-density correlation. The recycled/regenerated electrolytes maintain similar physical and chemical properties comparable to pristine electrolytes, exhibiting a wide ESW of 3 V. Pouch cells (0.5 Ah) assembled with the recycled and regenerated electrolyte exhibit equivalent performance to the pristine electrolyte, maintaining a capacity of over 87% after 300 cycles. Techno-economic analysis indicates that recycling salt reduces costs by 69.3% and regeneration electrolyte by 71.2%, both of which require wastewater treatment amounting to merely 5.6% of salt production. Remarkably, regeneration achieves substantial reductions in energy consumption (93.9%) and CO₂ emissions (94.8%) by eliminating energy-intensive drying processes, surpassing salt recycling's 85.4% and 87.9% reductions. Our work aims to provide a cost-effective and sustainable solution for using high-concentration electrolytes, enabling the practical implementation of aqueous lithium-ion batteries.