@article{7280, abstract = {Non-aqueous lithium-oxygen batteries cycle by forming lithium peroxide during discharge and oxidizing it during recharge. The significant problem of oxidizing the solid insulating lithium peroxide can greatly be facilitated by incorporating redox mediators that shuttle electron-holes between the porous substrate and lithium peroxide. Redox mediator stability is thus key for energy efficiency, reversibility, and cycle life. However, the gradual deactivation of redox mediators during repeated cycling has not conclusively been explained. Here, we show that organic redox mediators are predominantly decomposed by singlet oxygen that forms during cycling. Their reaction with superoxide, previously assumed to mainly trigger their degradation, peroxide, and dioxygen, is orders of magnitude slower in comparison. The reduced form of the mediator is markedly more reactive towards singlet oxygen than the oxidized form, from which we derive reaction mechanisms supported by density functional theory calculations. Redox mediators must thus be designed for stability against singlet oxygen.}, author = {Kwak, Won-Jin and Kim, Hun and Petit, Yann K. and Leypold, Christian and Nguyen, Trung Thien and Mahne, Nika and Redfern, Paul and Curtiss, Larry A. and Jung, Hun-Gi and Borisov, Sergey M. and Freunberger, Stefan Alexander and Sun, Yang-Kook}, issn = {2041-1723}, journal = {Nature Communications}, publisher = {Springer Nature}, title = {{Deactivation of redox mediators in lithium-oxygen batteries by singlet oxygen}}, doi = {10.1038/s41467-019-09399-0}, volume = {10}, year = {2019}, } @article{7276, abstract = {Singlet oxygen (1O2) causes a major fraction of the parasitic chemistry during the cycling of non‐aqueous alkali metal‐O2 batteries and also contributes to interfacial reactivity of transition‐metal oxide intercalation compounds. We introduce DABCOnium, the mono alkylated form of 1,4‐diazabicyclo[2.2.2]octane (DABCO), as an efficient 1O2 quencher with an unusually high oxidative stability of ca. 4.2 V vs. Li/Li+. Previous quenchers are strongly Lewis basic amines with too low oxidative stability. DABCOnium is an ionic liquid, non‐volatile, highly soluble in the electrolyte, stable against superoxide and peroxide, and compatible with lithium metal. The electrochemical stability covers the required range for metal–O2 batteries and greatly reduces 1O2 related parasitic chemistry as demonstrated for the Li–O2 cell.}, author = {Petit, Yann K. and Leypold, Christian and Mahne, Nika and Mourad, Eléonore and Schafzahl, Lukas and Slugovc, Christian and Borisov, Sergey M. and Freunberger, Stefan Alexander}, issn = {1433-7851}, journal = {Angewandte Chemie International Edition}, number = {20}, pages = {6535--6539}, publisher = {Wiley}, title = {{DABCOnium: An efficient and high-voltage stable singlet oxygen quencher for metal-O2 cells}}, doi = {10.1002/anie.201901869}, volume = {58}, year = {2019}, } @article{7281, abstract = {Li–O2 batteries are plagued by side reactions that cause poor rechargeability and efficiency. These reactions were recently revealed to be predominantly caused by singlet oxygen, which can be neutralized by chemical traps or physical quenchers. However, traps are irreversibly consumed and thus only active for a limited time, and so far identified quenchers lack oxidative stability to be suitable for typically required recharge potentials. Thus, reducing the charge potential within the stability limit of the quencher and/or finding more stable quenchers is required. Here, we show that dimethylphenazine as a redox mediator decreases the charge potential well within the stability limit of the quencher 1,4-diazabicyclo[2.2.2]octane. The quencher can thus mitigate the parasitic reactions without being oxidatively decomposed. At the same time the quencher protects the redox mediator from singlet oxygen attack. The mutual conservation of the redox mediator and the quencher is rational for stable and effective Li–O2 batteries.}, author = {Kwak, Won-Jin and Freunberger, Stefan Alexander and Kim, Hun and Park, Jiwon and Nguyen, Trung Thien and Jung, Hun-Gi and Byon, Hye Ryung and Sun, Yang-Kook}, issn = {2155-5435}, journal = {ACS Catalysis}, number = {11}, pages = {9914--9922}, publisher = {ACS}, title = {{Mutual conservation of redox mediator and singlet oxygen quencher in Lithium–Oxygen batteries}}, doi = {10.1021/acscatal.9b01337}, volume = {9}, year = {2019}, } @article{7282, abstract = {Interphases that form on the anode surface of lithium-ion batteries are critical for performance and lifetime, but are poorly understood. Now, a decade-old misconception regarding a main component of the interphase has been revealed, which could potentially lead to improved devices.}, author = {Freunberger, Stefan Alexander}, issn = {1755-4330}, journal = {Nature Chemistry}, number = {9}, pages = {761--763}, publisher = {Springer Nature}, title = {{Interphase identity crisis}}, doi = {10.1038/s41557-019-0311-0}, volume = {11}, year = {2019}, } @article{7283, abstract = {Potassium–air batteries, which suffer from oxygen cathode and potassium metal anode degradation, can be cycled thousands of times when an organic anode replaces the metal.}, author = {Petit, Yann K. and Freunberger, Stefan Alexander}, issn = {1476-1122}, journal = {Nature Materials}, number = {4}, pages = {301--302}, publisher = {Springer Nature}, title = {{Thousands of cycles}}, doi = {10.1038/s41563-019-0313-8}, volume = {18}, year = {2019}, }