How do organic polysulphides improve the performance of Li-S batteries?

Revitalizing Li-S batteries: the power of electrolyte additives

Lithium-sulfur (Li-S) batteries have garnered significant attention as promising next-generation energy storage solutions due to their high energy density and cost efficiency. However, the broad adoption of Li-S batteries is impeded by several critical issues. These include the intrinsically low conductivities of sulfur (S) and lithium sulfide (Li2S), the polysulfide shuttle effect, and dendrite formation on the lithium (Li) electrode, among other challenges. Overcoming these obstacles is crucial to realizing the full potential of Li-S batteries. A key step towards improving Li-S battery performance is the optimization of electrolytes, with a particular focus on enhancing cell cyclability, rate capability, safety, and lifespan. This review examines the current advancements in various electrolyte additive options, including their concepts, designs, and materials, and how the electrolyte's final chemical and physical properties influence the overall performance of Li-S batteries. The aim is to provide a comprehensive framework for the rational selection of future electrolyte additives for Li-S batteries, based on the available concepts, and to evaluate the existing electrolyte additives.

Electrode Interface Engineering in Lithium-Sulfur Batteries Enabled by a Trifluoroacetamide-Based Electrolyte

The passivation caused by the deposition of the insulating discharge final product, lithium sulfide (Li₂S), leads to the instability of the cycle and the rapid capacity fading of lithium-sulfur batteries (LSBs), which restricts the development of LSBs. This paper proposes the employment of trifluoroacetamide (TFA) as an electrolyte additive to alleviate the passivation by increasing the solubility of Li₂S. The solubilization effect of TFA on Li₂S is attributed to intermolecular hydrogen bonds and O-Li bonds. Li₂S in the TFA-based electrolyte exhibits a flower-like 3D deposition behavior, which further alleviates the surface passivation of the electrode and impels conversion kinetics. In addition, the LiF-rich solid electrolyte interface layer can effectively defend the Li metal anode and suppress the growth of Li dendrites. Accordingly, the discharge capacity of the TFA-based battery remains at an excellent 681.2 mA h g^-1 after 400 cycles with a Coulombic efficiency of 99% at 0.5 C. After the battery stabilizes, the capacity decay is only 0.036% per cycle. Under harsh conditions, such as high rates (2 C) and high sulfur loadings (5.2 mg cm^-2) with lean electrolytes and elevated temperatures (60 °C), TFA-containing batteries exhibited more durable and stable cycling. This paper provides new insights into solving practical problems and gives an impetus in cycle stability for LSBs.

Lithium-Sulfur Batteries: Advances and Trends

A review with 132 references. Societal and regulatory pressures are pushing industry towards more sustainable energy sources, such as solar and wind power, while the growing popularity of portable cordless electronic devices continues. These trends necessitate the ability to store large amounts of power efficiently in rechargeable batteries that should also be affordable and long-lasting. Lithium-sulfur (Li-S) batteries have recently gained renewed interest for their potential low cost and high energy density, potentially over 2600 Wh kg−1. The current review will detail the most recent advances in early 2020. The focus will be on reports published since the last review on Li-S batteries. This review is meant to be helpful for beginners as well as useful for those doing research in the field, and will delineate some of the cutting-edge adaptations of many avenues that are being pursued to improve the performance and safety of Li-S batteries.