Development of lithium sulphur battery and insights into its failure mechanism

Lithium–sulphur batteries are considered as a promising battery system due to its high theoretical capacity (1675 A h kg−1), high energy density (~2500 W h kg−1) and the natural abundance of sulphur. However, despite intensive research there are certain limitations to be overcome to bring Li/S to practical application; these limitations stem from the multiple reactions and phase changes in the sulphur cathode. Herein, for the first time to author’s knowledge, the effect of the cathode morphology as a function of charge cycles was studied by a multi-scale 3D in-situ X-ray tomography approach. The microstructural evolution within the same Li/S cell is studied without disrupting the contents and revealing significant changes to the electrode morphology. The uneven distribution of the sulphur phase fraction within the electrode thickness and sulphur agglomeration upon cycling were shown. The advantages of in-situ X-ray tomography are compelling, enabling a non-destructive imaging of battery. Furthermore, the strategies for Li/S optimisation were reflected. A comparative study of the effect of widely available conducting polymers: polyacrylonitrile and polyaniline; and metal oxide additives: Mg0.6Ni0.4O and Al2O3; on the Li/S performance, both capacity and cycle life was conducted. Commercially viable cell configurations were developed by a simple ball milling followed by a heat treatment; the best performance was by S/PANI/ Mg0.6Ni0.4O composite with an initial discharge capacity of 1500 mA h g-1. Many problems arise due to polysulphides solubility; therefore, the optimised cathode was tested with electrolytes to investigate the effect of high concentration and viscosity, as well as LiNO3 addition. It was shown that although increasing the electrolyte concentration leads to the higher battery performance and stability, the similar results could be achieved with the addition of LiNO3. Generally, it was shown the tailoring electrolyte and electrodes parameters for Li/S cell is as important as development of efficient and easy scale-up S electrodes

Exploring 3D microstructural evolution in Li-Sulfur battery electrodes using in-situ X-ray tomography

Lithium sulfur (Li-S) batteries offer higher theoretical specific capacity, lower cost and enhanced safety compared to current Li-ion battery technology. However, the multiple reactions and phase changes in the sulfur conversion cathode result in highly complex phenomena that significantly impact cycling life. For the first time to the authors’ knowledge, a multi-scale 3D in-situ tomography approach is used to characterize morphological parameters and track microstructural evolution of the sulfur cathode across multiple charge cycles. Here we show the uneven distribution of the sulfur phase fraction within the electrode thickness as a function of charge cycles, suggesting significant mass transport limitations within thick-film sulfur cathodes. Furthermore, we report a shift towards larger particle sizes and a decrease in volume specific surface area with cycling, suggesting sulfur agglomeration. Finally, we demonstrate the nano-scopic length-scale required for the features of the carbon binder domain to become discernible, confirming the need for future work on in-situ nano-tomography. We anticipate that X-ray tomography will be a powerful tool for optimization of electrode structures for Li-S batteries

Examining the effect of nanosized Mg₀.₆Ni₀.₄O and Al₂O₃ additives on S/polyaniline cathodes for lithium–sulphur batteries

Nanostructured magnesium nickel oxide Mg₀.₆Ni₀.₄O and alumina Al₂O₃ were studied as additives to sulphur/polyaniline (S/PANI) composites via wet ball-milling of sulphur and polyaniline followed by heat treatment. Metal oxide nanoparticles, which have small particle size, porous structure and high specific surface area to volume ratio, are expected to be catalytic for chemical reactions, including electron transfer and are able to adsorb lithium polysulphides. The composites were characterized by SEM and electrochemical methods. Cyclic voltammetry studies suggest that the alumina additive acts differently to the Mg₀.₆Ni₀.₄O. The results suggest that although the alumina additive improves the S/PANI composite performance as a lithium–sulphur battery cathode, the use of Mg₀.₆Ni₀.₄O is more effective

Exploring 3D microstructural evolution in Li-Sulfur battery electrodes using in-situ X-ray tomography

Lithium sulfur (Li-S) batteries offer higher theoretical specific capacity, lower cost and enhanced safety compared to current Li-ion battery technology. However, the multiple reactions and phase changes in the sulfur conversion cathode result in highly complex phenomena that significantly impact cycling life. For the first time to the authors’ knowledge, a multi-scale 3D in-situ tomography approach is used to characterize morphological parameters and track microstructural evolution of the sulfur cathode across multiple charge cycles. Here we show the uneven distribution of the sulfur phase fraction within the electrode thickness as a function of charge cycles, suggesting significant mass transport limitations within thick-film sulfur cathodes. Furthermore, we report a shift towards larger particle sizes and a decrease in volume specific surface area with cycling, suggesting sulfur agglomeration. Finally, we demonstrate the nano-scopic length-scale required for the features of the carbon binder domain to become discernible, confirming the need for future work on in-situ nano-tomography. We anticipate that X-ray tomography will be a powerful tool for optimization of electrode structures for Li-S batteries

PACKING STRUCTURE OF BINARY PARTICLE COMPACTS WITH FIBERS

Fibers have been used to improve the mechanical properties of the asphalt paving mixture. It is known that the enhancement of powder compact mechanical properties is related to the compact packing microstructure. This study focuses on the evaluation of the packing microstructure of powder compacts produced from ternary mixtures of spherical particles and fibers. The discrete element method is employed to generate the compacts of particle mixtures of different compositions under gravity. The compact microstructure is quantitatively characterized by utilizing the developed image analysis technique to approximate the size distribution of voids among particles in X, Y and Z directions. As a result, the denser packing was obtained with a greater fraction of small spherical particles. The inclusion of fibers resulted in the high-density compact with uniform distribution of small size voids

Examining the effect of nanosized Mg0.6Ni0.4O and Al2O3 additives on S/polyaniline cathodes for lithium–sulphur batteries

Abstract Nanostructured magnesium nickel oxide Mg0.6Ni0.4O and alumina Al2O3 were studied as additives to sulphur/polyaniline (S/PANI) composites via wet ball-milling of sulphur and polyaniline followed by heat treatment. Metal oxide nanoparticles, which have small particle size, porous structure and high specific surface area to volume ratio, are expected to be catalytic for chemical reactions, including electron transfer and are able to adsorb lithium polysulphides. The composites were characterized by SEM and electrochemical methods. Cyclic voltammetry studies suggest that the alumina additive acts differently to the Mg0.6Ni0.4O. The results suggest that although the alumina additive improves the S/PANI composite performance as a lithium–sulphur battery cathode, the use of Mg0.6Ni0.4O is more effective