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

Didier Blanchard,Mark Slagter

doi:10.1088/2515-7655/ac0b37

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.

Highlights

During the past decade, the quest for promising generation electricity storage systems has led significant attention to secondary batteries with high specific energy such as lithium–sulfur batteries (LSBs) (3861 mAh g−1 lithium and 1675 mAh g−1 sulfur at 2.15 V), [1,2,3,4,5,6] of three to five times higher energy densities than commercial state-of-art Li-ion batteries, e.g. LiNixMnyCozO2 (NMC) and LiNi1−y−zCoyAlzO2 (NCA), 170 mAh g−1 of active cathode material at 4.5 V and 4.1 V, respectively [7]
Cathode preparation In this work, the preparation of carbon–sulfur cathode containing either carrageenan as a bio-binder or polyvinylidene fluoride (PVDF) as conventional binder, consisted of two main steps: synthesis of the carbon–sulfur powder and incorporation of binder. λ-carrageenan was used for having the highest density of sulfate groups among all the different carrageenan types
In the present work we have confirmed that carrageenan can be used as binder for the cathode of LSB and would help to reduce the capacity fading during charge–discharge cycling

Summary

Introduction

The quest for promising generation electricity storage systems has led significant attention to secondary batteries with high specific energy such as lithium–sulfur batteries (LSBs) (3861 mAh g−1 lithium and 1675 mAh g−1 sulfur at 2.15 V), [1,2,3,4,5,6] of three to five times higher energy densities than commercial state-of-art Li-ion batteries, e.g. LiNixMnyCozO2 (NMC) and LiNi1−y−zCoyAlzO2 (NCA), 170 mAh g−1 of active cathode material at 4.5 V and 4.1 V, respectively [7]. To investigate physical changes to the electrode materials, x-ray diffraction [13, 14, 22, 23], x-ray transmission microscopy [23, 24], and x-ray tomography [25,26,27,28,29,30,31,32] are applied. Most of these technics can be performed in operando, i.e. while the battery cell is in operation to collect real time insights into the complex chemistry and the mechanisms at play

Methods

Results

Conclusion