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Abstract Sodium–oxygen (Na–O2) batteries are considered a promising energy storage alternative to current state‐of‐the‐art technologies owing to their high theoretical energy density, along with the natural abundance and low price of Na metal. The chemistry of these batteries depends on sodium superoxide (NaO2) or peroxide (Na2O2) being formed/decomposed. Most Na–O2batteries form NaO2, but reversibility is usually quite limited due to side reactions at interfaces. By using new materials, including a highly active catalyst based on vanadium phosphide (VP) nanoparticles, an ether/ionic liquid‐based electrolyte, and an effective sodium bromide (NaBr) anode protection layer, the sources of interface reactivity can be reduced to achieve a Na–O2battery cell that is rechargeable for 1070 cycles with a high energy efficiency of more than 83%. Density functional theory calculations, along with experimental characterization confirm the three factors leading to the long cycle life, including the effectiveness of the NaBr protective layer on the anode, a tetraglyme/EMIM‐BF4based electrolyte that prevents oxidation of the VP cathode catalyst surface, and the EMIM‐BF4ionic liquid aiding in avoiding electrolyte decomposition on NaO2.
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Secondary electron emission measurements from imidazolium-based ionic liquids
Abstract The electron-induced secondary electron emission (SEE) yields of imidazolium-based ionic liquids are presented for primary electron beam energies between 30 and 1000 eV. These results are important for understanding plasma synthesis of nanoparticles in plasma discharges with an ionic liquid electrode. Due to their low vapor pressure and high conductivity, ionic liquids can produce metal nanoparticles in low-pressure plasmas through reduction of dissolved metal salts. In this work, the low vapor pressure of ionic liquids is exploited to directly measure SEE yields by bombarding the liquid with electrons and measuring the resulting currents. The ionic liquids studied are [BMIM][Ac], [EMIM][Ac], and [BMIM][BF4]. The SEE yields vary significantly over the energy range, with maximum yields of around 2 at 200 eV for [BMIM][Ac] and [EMIM][Ac], and 1.8 at 250 eV for [BMIM][BF4]. Molecular orbital calculations indicate that the acetate anion is the likely electron donor for [BMIM][Ac] and [EMIM][Ac], while in [BMIM][BF4], the electrons likely originate from the [BMIM]+cation. The differences in SEE yields are attributed to varying ionization potentials and molecular structures of the ionic liquids. These findings are essential for accurate modeling of plasma discharges and understanding SEE mechanisms in ionic liquids.
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- Award ID(s):
- 2320244
- PAR ID:
- 10553235
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- Journal of Physics D: Applied Physics
- Volume:
- 58
- Issue:
- 3
- ISSN:
- 0022-3727
- Format(s):
- Medium: X Size: Article No. 035206
- Size(s):
- Article No. 035206
- Sponsoring Org:
- National Science Foundation
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