Probing the Effectiveness in Stabilizing Lithium Metal Anodes through Functional Additives.

A variety of electrolyte additives were comprehensively evaluated to understand their relative capability in stabilizing lithium metal anode. Although the Li||Cu test is an effective test to rule out ineffective additives, a reliable assessment of individual additives cannot be obtained just by a single evaluation method. Therefore, various methods must be combined to truly assess the stabilization of a lithium anode. Moreover, it was also discovered that a significant depletion of electrolytes occurred during the end-of-life of the lithium batteries, which partially contributed to the sudden failure of the lithium batteries during cycling. However, the main culprit of the sudden failure was identified as the significant increase in the resistance of the lithium metal anode. When used as an additive, cyclic fluorinated carbonates are the most effective in stabilizing the lithium anode and improving the cycling performance of lithium batteries among all the common additives. Despite its cost-effectiveness, the additive in the conventional electrolyte approach provides insufficient protection for lithium metal due to the complete consumption of the additive materials, which is necessary to repair the solid-electrolyte interphase (SEI). Therefore, it is suggested that a larger ratio (>15 wt %) of the SEI former should be employed to achieve effective lithium stabilization.

Sepiolite as a novel polysulfide trapper for energy applications: an electrochemical, X-ray spectroscopic and DFT study.

Capacity retention is a critical property to enhance in electrochemical storage systems applied to renewable energy. In lithium-sulfur (Li-S) batteries, the capacity fade resulting from the shuttle effect of polysulfides is a major obstacle to their practical application. Sepiolite, an eco-friendly earth-abundant clay with suitable surface chemistry for anchoring and retaining various molecules and structures, was studied as a cathode additive to mitigate the shuttle effect using experimental and theoretical approaches. Electrochemical measurements, spectroscopy, and ab initio calculations were performed to describe the mechanism and interfaces involved in polysulfide retention using 2 wt% of sepiolite as an additive in Li-S batteries. The results showed that the addition of sepiolite significantly improved the capacity retention during battery cycling. Spectroscopic analysis revealed that the effective sepiolite-polysulfide interface was governed by oxidized sulfur species. Additionally, ab initio studies showed a highly exothermic adsorption both inside and outside the sepiolite pore. This study demonstrates the potential use of eco-friendly, low-cost, non-toxic, natural, and abundant materials as additives to increase capacity retention.

Triazine-Carbon Nanotubes: New Platforms for the Design of Flavin Receptors.

The synthesis of functionalised carbon nanotubes as receptors for riboflavin (RBF) is reported. Carbon nanotubes, both single-walled and multi-walled, have been functionalised with 1,3,5-triazines and p-tolyl chains by aryl radical addition under microwave irradiation and the derivatives have been fully characterised by using a range of techniques. The interactions between riboflavin and the hybrids were analysed by using fluorescence and UV/Vis spectroscopic techniques. The results show that the attached functional groups minimise the π-π stacking interactions between riboflavin and the nanotube walls. Comparison of p-tolyl groups with the triazine groups shows that the latter have stronger interactions with riboflavin because of the presence of hydrogen bonds. Moreover, the triazine derivatives follow the Stern-Volmer relationship and show a high association constant with riboflavin. In this way, artificial receptors in catalytic processes could be designed through specific control of the interaction between functionalised carbon nanotubes and riboflavin.