Controlled Synthesis of Sulfur-Rich Polymeric Selenium Sulfides as Promising Electrode Materials for Long-Life, High-Rate Lithium Metal Batteries

Abstract

High-energy lithium/sulfur (Li/S) batteries still suffer from unsatisfactory cycle life and poor rate capability caused by the polysulfides shuttle and insulating nature of S cathodes. Here, we report our findings in the controlled synthesis of selenium (Se)-containing S-rich co-polymers of various compositions as novel cathode materials through a facile inverse vulcanization of S with selenium disulfide (SeS) and 1,3-diisopropenylbenzene (DIB) as co-monomers. Nuclear magnetic resonance and X-ray photoelectron spectroscopy results show that divinyl functional groups of DIB were chemically cross-linked with S/SeS chain radicals through a ring-opening polymerization. The newly formed bonds of C-S, C-Se, and S-Se in novel S-SeS-DIB co-polymers effectively alleviate the shuttle effects of polysulfides/polyselenides. Furthermore, various electrochemical techniques confirm the positive roles of Se-containing co-polymers in enhancing the electrode reaction kinetics and the formation of stable solid electrolyte interphase layer with low charge-transfer resistance, leading to improved high-rate performances. The as-synthesized co-polymer was then infiltrated into well-interconnected, porous nanocarbon networks (Ketjenblack EC600JD, KB600) to provide effective paths for the fast electron transport. Due to the synergistic combination of chemical and physical confinement of the reaction intermediates during cycling, good reversibility for 500 cycles with a low decay rate of 0.0549% per cycle was achieved at 1000 mA g. These encouraging results suggest that the combination of chemical incorporation of SeS into S-rich co-polymer and the physical confinement of carbon networks is a promising strategy for advancing Li/S batteries and their viability for practical applications.

An Organic–Inorganic Hybrid Cathode Based on S–Se Dynamic Covalent Bonds

“…As shown in the Supporting Information, Figure S7, the Se 3d 5/2 and 3d 3/2 peaks of the fresh Se‐CNTs electrode are found at 55.31 and 56.17 eV . The charged DPTS‐Se electrode displays two major peaks at 55.02 and 55.85 eV, corresponding to Se 3d 5/2 and Se 3d 3/2 , respectively, as shown in Figure E. Furthermore, a new doublet at a higher binding energy of 55.39/56.28 eV in the Se 3d spectrum is assigned to Se bonded to S (heteropolar Se−S bond) . Meanwhile, there is a major doublet at 160.40/167.60 eV corresponding to Se bonded to Se (homopolar Se−Se bonds), as shown in Figure F. While the two new doublets at 161.81/168.85 eV are assigned to Se bonded to S (S−Se bonds) .…”

An Organic–Inorganic Hybrid Cathode Based on S–Se Dynamic Covalent Bonds

“…Furthermore,anew doublet at ah igher binding energy of 55.39/56.28 eV in the Se 3d spectrum is assigned to Se bonded to S(heteropolar SeÀSbond). [19] Meanwhile,there is amajor doublet at 160.40/167.60 eV corresponding to Se bonded to Se (homopolar SeÀSe bonds), as shown in Figure 2F.W hile the two new doublets at 161.81/168.85 eV are assigned to Se bonded to S( S À Se bonds). [8] According to the XPS analysis, the predominant peaks of Se 3d exist.…”

Multiple Covalent Triazine Frameworks with Strong Polysulfide Chemisorption for Enhanced Lithium‐Sulfur Batteries

“…In recent years, polymeric covalent sulfur has been explored as electroactive materials for energy storage systems ,. Through this method, the cycle performance of Li−S battery has been improved.…”

“…[31] In recent years, polymeric covalent sulfur has been explored as electroactive materials for energy storage systems. [32,33] Through this method, the cycle performance of LiÀ S battery has been improved. One main reason was that the polymeric sulfur can distribute in the cathode materials uniformly.…”