期刊
ENERGY & ENVIRONMENTAL SCIENCE
卷 12, 期 8, 页码 -出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/c9ee01453e
关键词
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资金
- European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program [636069]
- Austrian Federal Ministry of Science, Research and Economy
- Austrian Research Promotion Agency [845364]
Aprotic alkali metal-oxygen batteries require reversible formation of metal superoxide or peroxide on cycling. Severe parasitic reactions cause poor rechargeability, efficiency, and cycle life and have been shown to be caused by singlet oxygen (O-1(2)) that forms at all stages of cycling. However, its formation mechanism remains unclear. We show that disproportionation of superoxide, the product or intermediate on discharge and charge, to peroxide and oxygen is responsible for O-1(2) formation. While the overall reaction is driven by the stability of peroxide and thus favored by stronger Lewis acidic cations such as Li+, the O-1(2) fraction is enhanced by weak Lewis acids such as organic cations. Concurrently, the metal peroxide yield drops with increasing O-1(2). The results explain a major parasitic pathway during cell cycling and the growing severity in K-, Na-, and Li-O-2 cells based on the growing propensity for disproportionation. High capacities and rates with peroxides are now realized to require solution processes, which form peroxide or release O(2)via disproportionation. The results therefore establish the central dilemma that disproportionation is required for high capacity but also responsible for irreversible reactions. Highly reversible cell operation requires hence finding reaction routes that avoid disproportionation.
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