Sulfurized-Polyacrylonitrile Cathode with Polyacrylic Acid Binder and Fluoroethylene Carbonate Additive for Improved Performances of Lithium-Sulfur Batteries

Abstract

Sulfurized carbonized polyacrylonitrile (S-CPAN) is a promising cathode material for Li−S batteries owing to the absence of polysulfide dissolution phenomena in the electrolyte solutions and thus the lack of a detrimental shuttle mechanism.1,2 However, challenges remain in achieving high performance at practical loading because of large volume expansion of S-CPAN electrodes and lithium anode degradation at high current densities. To take advantage of the unique charge-discharge mechanisms of S-CPAN electrodes at high sulfur loadings, we introduce a novel cell design through the application of polyacrylic acid (PAA) binder to S-CPAN electrodes using alkyl carbonate based electrolyte solutions with fluoroethylene carbonate (FEC) as an additive. PAA based binders were found to be superior over PVdF in a previous work, in terms of excellent adhesion and cohesion properties of composite electrodes. FEC is considered a ‘magic’ additive/co-solvent in Li salt electrolyte solutions, working with Li metal or Li-Si anodes and high voltage Li insertion cathodes or S-C composite cathodes as its surface reactions lead to polymerization and formation of effectively passivating surface films. We found that Li-S cells comprising S-CPAN cathodes with PAA binder resolve the inherent problems of cathode structure fragmentation through hydrogen bonding of S-CPAN-PAA and S-CPAN-PAA-Al2O3, which strengthen the cathode structure.3 A major advantage of using FEC-containing solutions is the stabilization of the lithium metal anodes by formation of passivating surface films.4 The combination of these three components — S-CPAN, PAA, and FEC — resulted in outstanding electrochemical performance of practically loaded sulfur cathodes with stable cycle life. We demonstrated pouch cells,5 which contained 100 mAh S-CPAN cathodes with a specific capacity around 3 mAh cm-2, which exhibited very stable. References J. Wang, J. Yang, J. Xie, and N. Xu, Adv. Mater., 2002, 14, 963B. Scrosati, J. Hassoun, Y.-K. Sun, Energy Environ. Sci. 2011, 4, 3287 J.-Y. Hwang, H. M. Kim, S. K. Lee, J. H. Lee, A. Abouimrane, M. A. Khaleel, I. Belharouak, A. Manthiram, Y.-K. Sun, Adv. Energy Mater. 2016, 6, 1501480E. Markevich, G. Salitra, A. Rosenman, Y. Talyosef, F. Chesneau and D. Aurbach, Electrochem. Commun., 2015, 60, 42H.-S. Kang, E. Park, J.-Y. Hwang, H. Kim, D. Aurbach, A. Rosenman, Y.-K. Sun, Adv. Mater. Technol. 2016, 1600052