Binary Mixtures of Highly Concentrated Tetraglyme and Hydrofluoroether as a Stable and Nonflammable Electrolyte for Li–O₂ Batteries

Developing a long-term stable electrolyte is one of the most enormous challenges for Li–O₂ batteries. Equally, the high flammability of frequently used solvents seriously weakens the electrolyte safety in Li–O₂ batteries, which inevitably restricts their commercial applications. Here, a binary mixture of highly concentrated tetraglyme electrolyte (HCG4) and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE) was used for a novel electrolyte (HCG4/TTE) in Li–O₂ batteries, which exhibit good wettability, enhanced ionic conductivity, considerable nonflammability, and high electrochemical stability. Being a co-solvent, TTE can contribute to increasing ionic conductivity and to improving flame retardance of the as-prepared electrolyte. The cell with this novel electrolyte displays an enhanced cycling stability, resulting from the high electrochemical stability during cycling and the formation of electrochemically stable interfaces prevents parasitic reactions occurring on the Li anode. These results presented here demonstrate a novel electrolyte with a high electrochemical stability and considerable safety for Li–O₂ batteries

3D Foam-Like Composites of Mo₂C Nanorods Coated by N‑Doped Carbon: A Novel Self-Standing and Binder-Free O₂ Electrode for Li–O₂ Batteries

The development of self-standing and binder-free O₂ electrodes is significant for enhancing the total specific energy density and suppressing parasitic reactions for Li–O₂ batteries, which is still a formidable challenge thus far. Here, a three-dimensional foam-like composite composed of Mo₂C nanorods decorated by different amounts of N-doped carbon (Mo₂C-NR@<i>x</i>NC (<i>x</i> = 5, 11, and 16 wt %)) was directly employed as the O₂ electrode without applications of any binders and current collectors. Mo₂C-NR@<i>x</i>NC presents a network microstructure with interconnected macropore and mesoporous channels, which is beneficial to achieving fast Li⁺ migration and O₂ diffusion, facilitating the electrolyte impregnation, and providing enough space for Li₂O₂ storage. Additionally, the coated N-doped carbon layer can largely improve the electrochemical stability and conductivity of Mo₂C. The cell with Mo₂C-NR@11NC shows a considerable cyclability of 200 cycles with an overpotential of 0.28 V in the first cycle at a constant current density of 100 mA g^–1, a superior reversibility associated with the formation and decomposition of Li₂O₂ as desired, and a high electrochemical stability. On the basis of the experimental results, the electrochemical mechanism for the cell using Mo₂C-NR@11NC is proposed. These results represent a promising process in the development of a self-standing and binder-free foam-based electrode for Li–O₂ batteries