Unexpected\nEffect of Electrode Architecture on High-Performance\nLithium–Sulfur Batteries

Abstract

In\nthe past years, considerable efforts have been devoted to the\ndeliberate synthesis of nanosulfur in various hosts with sophisticated\nstructures to improve the performance of lithium–sulfur batteries\n(LSBs) and reveal the structure–property relationship. It is\ntaken for granted that these elaborate sulfur nanostructures are well\nmaintained in the ultimate electrode after the traditional mixing\nand coating method. Herein, we, for the first time, reveal the unexpected\nsulfur structure deterioration in nanosulfur/graphene composites during\nthe electrode preparation using the traditional method because of\nthe long-term neglected dissolution–recrystallization effect\nof sulfur in solvents. Consequently, compared with binder-free three-dimensional\ngraphene/sulfur electrodes, the milled graphene/sulfur electrodes\nexhibit much worse electrochemical performance. On the basis of this,\nwe further propose a facile and universal graphene oxide-assisted\nassembly method to avoid the dissolution–recrystallization\nof sulfur, by which binder-free three-dimensional ethylenediamine-functionalized\ngraphene/sulfur (3DEFGS) electrodes have been successfully prepared.\nThe 3DEFGS electrodes with a high areal sulfur loading of ∼6\nmg cm^–2 exhibit an ultrahigh initial capacity of\n1394 mA h g^–1 at 0.1 C, an excellent rate performance\nwith a capacity of 796 mA h g^–1 at 4 C, and superior\nlong-term cycling stability (885 mA h g^–1 after\n500 cycles at 1 C), which are among the best performances achieved\nby all reported LSB cathodes with high areal sulfur loadings.