DABCOnium: Ein effizienter und Hochspannungs‐stabiler Singulett‐Sauerstoff‐Löscher für Metall‐O 2 ‐Zellen

Overlooked Factors Required for Electrolyte Solvents in Li-O2 Batteries: Capabilities of Quenching 1 O2 and Forming Highly-Decomposable Li2 O2

Although sufficient tolerance against attack by superoxide radicals (O₂ ^- ) has been mainly recognized as an important property for Li-O₂ battery (LOB) electrolytes, recent evidence has revealed that other critical factors also govern the cyclability, prompting a reconsideration of the basic design guidelines of LOB electrolytes. Here, we found that LOBs equipped with a N,N-dimethylacetamide (DMA)-based electrolyte exhibited better cyclability compared with other standard LOB electrolytes. This superior cyclability is attributable to the capabilities of quenching ¹ O₂ and forming highly decomposable Li₂ O₂ . The ¹ O₂ quenching capability is equivalent to that of a tetraglyme-based electrolyte containing a several millimolar concentration of a typical chemical quencher. Based on these overlooked factors, the DMA-based electrolyte led to superior cyclability despite its lower O₂ ^- tolerance. Thus, the present work provides a novel design guideline for the development of LOB electrolytes.

A Mitochondrion-Localized Two-Photon Photosensitizer Generating Carbon Radicals Against Hypoxic Tumors

The efficacy of photodynamic therapy is typically reliant on the local concentration and diffusion of oxygen. Due to the hypoxic microenvironment found in solid tumors, oxygen-independent photosensitizers are in great demand for cancer therapy. We herein report an iridium(III) anthraquinone complex as a mitochondrion-localized carbon-radical initiator. Its emission is turned on under hypoxic conditions after reduction by reductase. Furthermore, its two-photon excitation properties (λ_ex =730 nm) are highly desirable for imaging. Upon irradiation, the reduced form of the complex generates carbon radicals, leading to a loss of mitochondrial membrane potential and cell death (IC₅₀ ^light =2.1 μm, IC₅₀ ^dark =58.2 μm, PI=27.7). The efficacy of the complex as a PDT agent was also demonstrated under hypoxic conditions in vivo. To the best of our knowledge, it is the first metal-complex-based theranostic agent which can generate carbon radicals for oxygen-independent two-photon photodynamic therapy.

Pathways to Triplet or Singlet Oxygen during the Dissociation of Alkali Metal Superoxides: Insights by Multireference Calculations of Molecular Model Systems

Recent experimental investigations demonstrated the generation of singlet oxygen during charging at high potentials in lithium/oxygen batteries. To contribute to the understanding of the underlying chemical reactions a key step in the mechanism of the charging process, namely, the dissociation of the intermediate lithium superoxide to oxygen and lithium, was investigated. Therefore, the corresponding dissociation paths of the molecular model system lithium superoxide (LiO₂ ) were studied by CASSCF/CASPT2 calculations. The obtained results indicate the presence of different dissociation paths over crossing points of different electronic states, which lead either to the energetically preferred generation of triplet oxygen or the energetically higher lying formation of singlet oxygen. The dissociation to the corresponding superoxide anion is energetically less preferred. The understanding of the detailed reaction mechanism allows the design of strategies to avoid the formation of singlet oxygen and thus to potentially minimize the degradation of materials in alkali metal/oxygen batteries. The calculations demonstrate a qualitatively similar but energetically shifted behavior for the homologous alkali metals sodium and potassium and their superoxide species. Fundamental differences were found for the covalently bound hydroperoxyl radical.

Electrolytes for Rechargeable Lithium-Air Batteries

Lithium-air batteries are promising devices for electrochemical energy storage because of their ultrahigh energy density. However, it is still challenging to achieve practical Li-air batteries because of their severe capacity fading and poor rate capability. Electrolytes are the prime suspects for cell failure. In this Review, we focus on the opportunities and challenges of electrolytes for rechargeable Li-air batteries. A detailed summary of the reaction mechanisms, internal compositions, instability factors, selection criteria, and design ideas of the considered electrolytes is provided to obtain appropriate strategies to meet the battery requirements. In particular, ionic liquid (IL) electrolytes and solid-state electrolytes show exciting opportunities to control both the high energy density and safety.