High-Performance Cathode Materials for Lithium–Sulfur Batteries Based on Sulfurated Poly(norbornadiene) and Sulfurated Poly(dicyclopentadiene)

Abstract

Lithium–sulfur (Li–S) batteries are among the most promising candidates for next-generation high-energy-density batteries; however, the polysulfide shuttle represents a major drawback in their application. Here, we report on sulfurized poly­(norbornadiene) (S/pNBD) and its analogue, sulfurized poly­(dicyclopentadiene) (S/pDCPD), two polysulfide shuttle-free and cheap cathode materials with good performance in Li–S battery technology. Both S/pNBD and S/pDCPD can be prepared in a straightforward two-step procedure. Time-of-flight secondary ion mass spectrometry, X-ray photoelectron spectroscopy measurements, and cyclic voltammetry indicate that all sulfur in S/pNBD and S/pDCPD is covalently bound to the polymer matrix in the form of C–S x –C units. Li–S cells based on an S/pNBD cathode exhibit a high discharge capacity up to 1050 mA h/g sulfur at 1 C with a good capacity retention of 62 % after 1900 cycles. The structurally similar analogue S/pDCPD shows comparable electrochemical performance, again with excellent capacity retention. The high reversibility and ultra-long cycle life of both, S/pNBD and S/pDCPD, are attributed to the covalent binding of sulfur to the polymer backbone.

Energy Storage System Based on Recycled Polypropylene and Its Use in Lithium–Sulfur and Lithium-Ion Batteries

“…The black line represents the discharge capacity, while the red line represents the Coulombic efficiency. During the first 20 cycles, the discharge capacity first increased and then decreased, which we tentatively attribute to the rearrangement of the sulfur chains in the C–S x –C moieties . Considering that no elemental sulfur was detected neither in UV–Vis nor in PXRD, small parts of sulfur may become “inactive” while remaining covalently bound to the polymer matrix, however, not participating in the redox process .…”

“…Presumably, changes in the average length of the sulfur bridges in the C−S x −C moieties can be made accountable for that. 25,32 The discharge profile of S/PP-waste is shown in Figure 3b. No plateau corresponding to the formation of the long-chain polysulfides (∼2.0 to 2.3 V) was observed.…”

“…During the first 20 cycles, the discharge capacity first increased and then decreased, which we tentatively attribute to the rearrangement of the sulfur chains in the C−S x −C moieties. 25 Considering that no elemental sulfur was detected neither in UV−Vis nor in PXRD, small parts of sulfur may become "inactive" while remaining covalently bound to the polymer matrix, however, not participating in the redox process. 25 After the initial drop in capacity, a discharge capacity of S/PP-waste up to ∼500 mAh/ g sulfur was observed.…”

“…Another facile and effective strategy entails the use of organosulfur compounds as cathode materials that only experience solid phase transitions, thereby avoiding the polysulfide shuttle and guaranteeing excellent electrochemical performance . Representative compounds include sulfurized poly­(acrylonitrile) (SPAN), , sulfurated poly­(norbornadiene) (S/pNBD), sulfurated poly­(dicyclopentadiene) (S/pDCPD), and sulfurized carbyne . It is worth mentioning that not all organosulfur compounds are polysulfide-shuttle-free as is true for, e.g., sulfurated diisopropenylbenzene (DIB), sulfurated limonene, sulfurated tetra­(allyloxy)-1,4-benzoquinone (TABQ), sulfurated polypyrrole, and covalent triazine frameworks (CTFs) .…”

“…25 Considering that no elemental sulfur was detected neither in UV−Vis nor in PXRD, small parts of sulfur may become "inactive" while remaining covalently bound to the polymer matrix, however, not participating in the redox process. 25 After the initial drop in capacity, a discharge capacity of S/PP-waste up to ∼500 mAh/ g sulfur was observed. S/PP-waste-based cathodes show excellent cycle stability.…”