Applied Research Of Polysulfide-scission Reagents In Lithium-sulfur Batteries

Lithium-sulfur (Li-S) batteries have become an appealing candidate for next-generation energy-storage technologies due to their low cost and high theoretical energy density. Despite these considerable advantages,practical applications of rechargeable Li-S batteries are hindered by two main technical challenges. First, Li-S batteries suffer from low sulfur utilization and short cycle life, which originate from poor conductivity of sulfur and discharged products. Second, the dissolution of intermediate lithium polysulfide products (LiPSs, Li2Sn, 4 ? n: ? 8) leads to notorious shuttle effects, thereafter resulting in high self-discharge, low Coulombic efficiency, and active material loss. To facilitate the development of the Li-S batteries, it is therefore crucial to improve the conductivity of the sulfur cathode and restrain the shuttle effects via reusing the soluble LiPSs. In this paper, we introduced a new concept involving the graphene coupled with small biological molecules as interlayers assisted scission of polysulfides into Lithium-sulfur system. The main contents are as follows:(1) A conventional sulfur cathode with a PCNTs host material was prepared via a facile coating method, subsequently followed by overlaying the Gra/DTT interlayer onto the sulfur cathode. Our designed porous carbon nanotube/S cathode coupling with a lightweight graphene/DTT interlayer (PCNTs-S@Gra/DTT) exhibited ultrahigh cycle-ability even at 5 C over 1100 cycles., with a capacity degradation rate of 0.036% per cycle. Additionally, the PCNTs-S@Gra/DTT electrode with a 3.51 mg cm-2 sulfur mass loading maintained the reversible areal capacity of 3.45 mAh cm-2 (984mAh g-1) over 200 cycles at high current density of 1.17 mA cm-2, which represents a very high Capacity retention rate of 78.5%.(2) We present an insertion of graphene coupled with glutathione(Gra/G-SH) as an interlayer between the separator and cathode disk to improve the electrochemical performance of the Li-S batteries. The as-abtained CNTs-S@Gra/G-SH batteries exhibited excellent electrochemical performance: the CNTs-S@Gra/G-SH cathode delivered a much higher initial discharge capacity of 1362 mAh g-1 at a current rate of 0.2 C and a reversible specific capacity of 620 mAh g-1 over 400 cycles was achieved at the current rate of 2 C, corresponding to an ultralow-capacity degradation rate of 0.063% per cycle. Remarkably, the CNTs-S@Gra/DTT electrode with 3.37 mg cm-2 sulfur mass loading delieved a high initial reversible areal capacity of 3.11 mAh cm-2 (923 mAh g-1) at high current density of 1.13 mA cm-2, exhibiting a very high Capacity retention rate of 73.1%.