The recovery of valuable elements such as Li, Co, and Ni from spent lithiumion batteries is essential for environmental protection and energy conservation. However, the inadequate recovery efficiency of lithium by traditional methods hinders the development of this industry. Thus, a sustainable and efficient approach for the selective extraction of lithium from spent batteries by a carboxyl-functionalized ionic liquid (carboxymethyl trimethylammonium bis(trifluoromethyl)sulfonimide) to increase the recovery efficiency of lithium was designed and developed in this work. By appropriately adjusting and controlling the parameters including the pH value, extractant concentration, and phase ratio, the selective extraction of lithium was optimized with excellent selectivity and recovery efficiency. After optimization, the lithium extraction efficiency reached 96.8%. The slope method combined with FTIR spectroscopy was utilized to characterize the variations in the functional groups during extraction to reveal possible extraction mechanisms. The extraction of lithium ions from organic phases and the recycling of ionic liquids were subsequently investigated. This work proposes the concept of a green, recyclable extractant for selectively separating and recovering lithium from spent LIBs.

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A solid-state electrolyte has attracted great interest on energy storage and conversion, especially for lithium metal batteries (LMBs). However, its practical application is limited by poor ionic conductivity at room temperature and dendrite formation. Herein, a polymerized ionic liquid (PIL)-based solid electrolyte with the structure of a semi-interpenetrating polymer network is designed to enhance the ionic conductivity for LMBs. A one-step in situ cross-link [Vmim1O2][TFSI] is introduced in the poly-(vinylidene fluoride)−hexafluoropropylene matrix to fabricate the electrolyte. The obtained solid electrolyte exhibits a high ionic conductivity (1.06 × 10 −3 S cm −1 at 25 °C) and a wide electrochemical window (5.50 V vs Li/Li + ). The assembled lithium symmetrical cell can maintain a stable voltage range over 1000 h, and the mechanism is confirmed by density functional theory calculations. The employed MD simulations indicate a coordination of the TFSI − anion with both Li + and the polycation in different systems and demonstrate the feasibility of the Li + transport improvement based on the PIL. Li/LiFePO 4 batteries also show good cycle performance whose reversible capacity is about 153.7 mA h g −1 with 96.53% Coulombic efficiency at 0.1 C and 25 °C. This research shows that this PIL-based solid electrolyte possessed broad application for next-generation LMBs.

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