In operando Raman and optical study of lithium polysulfides dissolution in lithium–sulfur cells with carrageenan binder

Abstract

In operando Raman and optical studies have been performed on lithium–sulfur (Li–S) batteries containing carrageenan binder in the sulfur cathode for chemical trapping of the polysulfides (PSs). Three different types of cells were used: coin cells, EL-cell and capillary cells to examine the PS speciation. With the coin cell we confirm the stability and cyclability of the carrageenan based Li–S cells and the improved capacity retention when compared to conventional polyvinylidene fluoride based Li–S cells. With the EL-Cell, the PS speciation at the cathode is documented but only weak evidences of the nucleophilic trapping of the PS are found. The in operando Raman and optical studies on the capillary cell revealed the dissolution and diffusion of the PS in the whole electrolyte volume. We confirm the disproportionation of S4 − into S3 − in the electrolyte. Strong inhomogeneous PS concentration in the electrolyte are found to develop in the course of the cell charge–discharge cycling which must be detrimental to the performances of the battery.

Rough Endoplasmic Reticulum Inspired Polystyrene‐Brush‐Based Superhigh Sulfur Content Cathodes Enable Lithium–Sulfur Cells with High Mass and Capacity Loading

“…As shown in Figure 4h,i, the Raman signals related to S 8 are observed at 151, 217, and 472 cm −1 during the discharge from open‐circuit voltage to 2.3 V. Afterward, Li 2 S 6 (392 cm −1 ) and Li 2 S 4 (454 cm −1 ) appear coupled with the disappearance of S 8 when the voltage is below 2.2 V. The Raman peaks of Li 2 S 6 and Li 2 S 4 vanish completely at 1.7 V and are gradually regenerated in the subsequent charge process, indicating the reversibility of sulfur conversion. [ 30,49–51 ] These results indicate that vulcanized PS side‐chains could not only interact with polysulfides to restrain shuttle effect but also mediate polysulfide redox process, contributing to high‐efficiency sulfur utilization.…”

PRISMA: A robust and intuitive tool for high-throughput processing of chemical spectra

“…The dried material was scratched from the foil and cold-pressed into a pellet (7 mm in diameter and 152 μm in thickness) under 0.75 tons pressure and subsequently dried at 120 °C in a vacuum oven inside a glovebox overnight. A modified electrochemical-cell (ECC-OPTO) was assembled inside the glovebox using the pellet as cathode, a lithium foil with a diameter of 9 mm as anode and LP57 (E-lyte, 1M LiPF6 in 3:7 EC/EMC) as electrolyte for operando X-ray diffraction (XRD) measurements; further details about the cell and its assembly can be found in reference [30]. Diffraction data were recorded on a Rigaku Smartlab diffractometer in reflection geometry with a CuKα (λ1 = 1.54059, λ2 = 1.54441 Å; λ2/λ1 intensity ratio = 0.5) radiation source.…”

PRISMA: A robust and intuitive tool for high-throughput processing of chemical spectra

“…The dried material was scratched from the foil and cold-pressed into a pellet (7 mm in diameter and 152 μm in thickness) under 0.75 tons pressure and subsequently dried at 120 °C in a vacuum oven inside a glovebox overnight. A modified electrochemical-cell (ECC-OPTO) was assembled inside the glovebox using the pellet as cathode, a lithium foil with a diameter of 9 mm as anode and LP57 (E-lyte, 1M LiPF6 in 3:7 EC/EMC) as electrolyte for operando X-ray diffraction (XRD) measurements; further details about the cell and its assembly can be found in reference [29]. Diffraction data were recorded on a Rigaku Smartlab diffractometer in reflection geometry with a CuKα (λ1 = 1.54059, λ2 = 1.54441 Å; λ2/λ1 intensity ratio = 0.5) radiation source.…”