Locally Concentrated Ionic Liquid Electrolyte with Partially Solvating Diluent for Lithium/Sulfurized Polyacrylonitrile Batteries

• Published in: Advanced materials (Weinheim) 2022-12, Vol.34 (49), p.e2207155-n/a
• Main Authors: Liu, Xu, Diemant, Thomas, Mariani, Alessandro, Dong, Xu, Di Pietro, Maria Enrica, Mele, Andrea, Passerini, Stefano
• Format: Article
• Language: English
• Subjects: Cathodes; Cathodic dissolution; Cathodic protection; Dissolution; Electrodes; Electrolytes; Electrolytic cells; Flammability; Inorganic compounds; Ionic liquids; Ions; Lithium; lithium‐metal anodes; locally concentrated electrolytes; Materials science; Polyacrylonitrile; Solid electrolytes; sulfurized polyacrylonitrile
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.202207155

The development of Li/sulfurized polyacrylonitrile (SPAN) batteries requires electrolytes that can form stable electrolyte/electrode interphases simultaneously on lithium‐metal anodes (LMAs) and SPAN cathodes. Herein, a low‐flammability locally concentrated ionic liquid electrolyte (LCILE) employing monofluorobenzene (mFBn) as the diluent is proposed for Li/SPAN cells. Unlike non‐solvating diluents in other LCILEs, mFBn partially solvates Li+, decreasing the coordination between Li+ and bis(fluorosulfonyl)imide (FSI−). In turn, this triggers a more substantial decomposition of FSI− and consequently results in the formation of a solid electrolyte interphase (SEI) rich in inorganic compounds, which enables a remarkable Coulombic efficiency (99.72%) of LMAs. Meanwhile, a protective cathode electrolyte interphase (CEI), derived mainly from FSI− and organic cations, is generated on the SPAN cathodes, preventing the dissolution of polysulfides. Benefiting from the robust interphases simultaneously formed on both the electrodes, a highly stable cycling of Li/SPAN cells for 250 cycles with a capacity retention of 71% is achieved employing the LCILE and only 80% lithium‐metal excess. A low‐flammability locally concentrated ionic liquid electrolyte employing partially solvating monofluorobenzene as the diluent is developed for Li/sulfurized polyacrylonitrile (SPAN) batteries. Benefiting from the stable interphases simultaneously formed on both the anode and cathode, dendrite‐free cycling of lithium‐metal anodes with high Coulombic efficiency and highly stable cycling of Li/SPAN cells with low lithium‐metal excess have been achieved.