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The water catalysis at oxygen cathodes of lithium-oxygen cells.

Li F, Wu S, Li D, Zhang T, He P, Yamada A, Zhou H - Nat Commun (2015)

Bottom Line: However, even in the state-of-the-art lithium-oxygen cells the charge potentials are as high as 3.5 V that are higher by 0.70 V than the discharge potentials.This can significantly reduce the charge overpotential to 0.21 V, and results in a small discharge/charge potential gap of 0.32 V and superior cycling stability of 200 cycles.The overall reaction scheme will alleviate side reactions involving carbon and electrolytes, and shed light on the construction of practical, rechargeable lithium-oxygen cells.

View Article: PubMed Central - PubMed

Affiliation: 1] Energy Interface Technology Group, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1, Umezono, Tsukuba 305-8568, Japan [2] Department of Chemical System Engineering, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.

ABSTRACT
Lithium-oxygen cells have attracted extensive interests due to their high theoretical energy densities. The main challenges are the low round-trip efficiency and cycling instability over long time. However, even in the state-of-the-art lithium-oxygen cells the charge potentials are as high as 3.5 V that are higher by 0.70 V than the discharge potentials. Here we report a reaction mechanism at an oxygen cathode, ruthenium and manganese dioxide nanoparticles supported on carbon black Super P by applying a trace amount of water in electrolytes to catalyse the cathode reactions of lithium-oxygen cells during discharge and charge. This can significantly reduce the charge overpotential to 0.21 V, and results in a small discharge/charge potential gap of 0.32 V and superior cycling stability of 200 cycles. The overall reaction scheme will alleviate side reactions involving carbon and electrolytes, and shed light on the construction of practical, rechargeable lithium-oxygen cells.

No MeSH data available.


Discharge/charge profiles of the fifth cycles of the Li–O2 cells with Ru/MnO2/SP.The applied DMSO-based electrolytes are dried over a Li foil, and contain 120 and 281 p.p.m. of H2O. Rate: 500 mA g−1.
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f6: Discharge/charge profiles of the fifth cycles of the Li–O2 cells with Ru/MnO2/SP.The applied DMSO-based electrolytes are dried over a Li foil, and contain 120 and 281 p.p.m. of H2O. Rate: 500 mA g−1.

Mentions: The dependence of the charge potentials on the concentration of H2O in electrolytes is shown in Fig. 6. In the dried DMSO-based electrolyte, one charge potential plateau can be obtained at ∼3.65 V, which is attributed to the oxidation of Li2O2 and in good agreement with the literatrues101112131415. When there is 120 p.p.m. of water in the electrolyte, the charge potential plateau is significantly reduced to ∼3.2 V. This has been confirmed to the oxidation of LiOH that can be quickly converted from the primary discharge product Li2O2 via the sequential Steps (i and ii) in Fig. 5a over the catalyst of Ru/MnO2/SP in both the discharging and charging processes. However, when the concentration of water in the electrolyte is increased to 281 p.p.m., the charge potential plateau is shortened and increased. It may be induced by the LiOH on the surface of the discharge product, which is surrounded/adsorbed by H2O molecules in the electrolyte, and hence has high oxidation potentials following the Nernst equation173233.


The water catalysis at oxygen cathodes of lithium-oxygen cells.

Li F, Wu S, Li D, Zhang T, He P, Yamada A, Zhou H - Nat Commun (2015)

Discharge/charge profiles of the fifth cycles of the Li–O2 cells with Ru/MnO2/SP.The applied DMSO-based electrolytes are dried over a Li foil, and contain 120 and 281 p.p.m. of H2O. Rate: 500 mA g−1.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4525193&req=5

f6: Discharge/charge profiles of the fifth cycles of the Li–O2 cells with Ru/MnO2/SP.The applied DMSO-based electrolytes are dried over a Li foil, and contain 120 and 281 p.p.m. of H2O. Rate: 500 mA g−1.
Mentions: The dependence of the charge potentials on the concentration of H2O in electrolytes is shown in Fig. 6. In the dried DMSO-based electrolyte, one charge potential plateau can be obtained at ∼3.65 V, which is attributed to the oxidation of Li2O2 and in good agreement with the literatrues101112131415. When there is 120 p.p.m. of water in the electrolyte, the charge potential plateau is significantly reduced to ∼3.2 V. This has been confirmed to the oxidation of LiOH that can be quickly converted from the primary discharge product Li2O2 via the sequential Steps (i and ii) in Fig. 5a over the catalyst of Ru/MnO2/SP in both the discharging and charging processes. However, when the concentration of water in the electrolyte is increased to 281 p.p.m., the charge potential plateau is shortened and increased. It may be induced by the LiOH on the surface of the discharge product, which is surrounded/adsorbed by H2O molecules in the electrolyte, and hence has high oxidation potentials following the Nernst equation173233.

Bottom Line: However, even in the state-of-the-art lithium-oxygen cells the charge potentials are as high as 3.5 V that are higher by 0.70 V than the discharge potentials.This can significantly reduce the charge overpotential to 0.21 V, and results in a small discharge/charge potential gap of 0.32 V and superior cycling stability of 200 cycles.The overall reaction scheme will alleviate side reactions involving carbon and electrolytes, and shed light on the construction of practical, rechargeable lithium-oxygen cells.

View Article: PubMed Central - PubMed

Affiliation: 1] Energy Interface Technology Group, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1, Umezono, Tsukuba 305-8568, Japan [2] Department of Chemical System Engineering, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.

ABSTRACT
Lithium-oxygen cells have attracted extensive interests due to their high theoretical energy densities. The main challenges are the low round-trip efficiency and cycling instability over long time. However, even in the state-of-the-art lithium-oxygen cells the charge potentials are as high as 3.5 V that are higher by 0.70 V than the discharge potentials. Here we report a reaction mechanism at an oxygen cathode, ruthenium and manganese dioxide nanoparticles supported on carbon black Super P by applying a trace amount of water in electrolytes to catalyse the cathode reactions of lithium-oxygen cells during discharge and charge. This can significantly reduce the charge overpotential to 0.21 V, and results in a small discharge/charge potential gap of 0.32 V and superior cycling stability of 200 cycles. The overall reaction scheme will alleviate side reactions involving carbon and electrolytes, and shed light on the construction of practical, rechargeable lithium-oxygen cells.

No MeSH data available.