In situ/operando characterization techniques for rechargeable lithium–sulfur batteries: a review

Abstract

Rechargeable lithium-sulfur (Li-S) batteries have recently attracted global research interest due to their high theoretical specific capacity and energy density. To improve the performance and cycling stability of Li-S batteries, a clear understanding of the electrochemical reaction process and the degradation mechanisms of the sulfur redox chemistry are extremely important. In the past few decades, various advanced in situ/operando characterization tools have emerged, which have facilitated the understanding of the degradation mechanisms and the further development of high-performance Li-S batteries. In this review, we have summarized recent significant advances in in situ/operando characterization techniques for Li-S batteries. In particular, because of the existence of the soluble polysulfide species during the charge/discharge process, many creative ideas have been introduced into in situ/operando characterization of the electrochemical process in Li-S batteries.

Novel 2D Sb2S3 Nanosheet/CNT Coupling Layer for Exceptional Polysulfide Recycling Performance

“…The battery with an SSNS/CNT coupling layer displayed markedly better performance at high rates than those with both the CNT modified and neat PP separators. Clearly, both the high plateau capacity (with a theoretical capacity C H-th of 419 mA h g −1 for the reaction S 8 →Li 2 S 4 ) and the low plateau capacity (with a theoretical capacity of C L-th of 1256 mA h g −1 for the reaction Li 2 S 4 →L 2 S) [58] of the LSB with an SSNS/CNT coupling layer were much higher than the corresponding values of the LSBs with the other separators for all rates studied. To be more specific, the individual contributions from the high and low plateau capacities at different current densities are plotted in Figure 4d.…”

“…The plateaus in the charge curves signify the conversion from Li 2 S 2 /Li 2 S to S 8 molecules, while those in the discharge curves represent the reduction of element S to highorder polysulfides (Li 2 S x , x = 4-8) at ≈2.3-2.4 V (i.e., at high plateau) and eventually to Li 2 S 2 /Li 2 S at ≈2.1 V (i.e., at low plateau). [58] It is evident that the high plateau capacity of the LSB with an SSNS/CNT coupling layer was much higher than those of the other two systems, a reflection in that the dissolution of polysulfides was inhibited and the soluble polysulfides were confined within the cathode zone in the former battery. [59] The beneficial effect of the coupling layer made from SSNS/ CNT composite was particularly significant on the low plateau at ≈2.1 V, indicating that the SSNS/CNT modified separator effectively inhibited the diffusion of polysulfides to the other side and recovered the activities of Li 2 S x species.…”

“…To be more specific, the individual contributions from the high and low plateau capacities at different current densities are plotted in Figure 4d. Clearly, both the high plateau capacity (with a theoretical capacity C H-th of 419 mA h g −1 for the reaction S 8 →Li 2 S 4 ) and the low plateau capacity (with a theoretical capacity of C L-th of 1256 mA h g −1 for the reaction Li 2 S 4 →L 2 S) [58] of the LSB with an SSNS/CNT coupling layer were much higher than the corresponding values of the LSBs with the other separators for all rates studied. After introducing the SSNS/CNT coupling layer onto the separator, the initial utilization of the high plateau capacity (C H-th = 419 mAh g −1 ) at 0.1 C increased from 60% to 84%, indicative of successful suppression of polysulfide diffusion and effective electrochemical conversion reaction.…”

In Situ Techniques for Developing Robust Li–S Batteries

“…Among them, various in situ characterization techniques have been intensively utilized and reviewed in LIB research . In comparison, although many LSB in situ studies have been undertaken, this work has rarely been critically reviewed . Here, we aim to provide an understanding of how in situ characterization tools are being developed and can be used to guide novel material development for LSBs.…”

“…[8][9][10][11] In comparison, although many LSB in situ studies have been undertaken, this work has rarely been critically reviewed. [12] Here, we aim to provide an understanding of how in situ characterization tools are being developed and can be used to guide novel material development for LSBs. We focus on laboratory X-ray powder diffraction (XRD), small-angle X-ray scattering (SAXS), synchrotron radiation, Raman, neutron diffraction (ND), transmission electron microscopy (TEM), and nuclear magnetic resonance (NMR).…”