化学
氧化还原
电解质
歧化
单线态氧
法拉第效率
锂(药物)
降级(电信)
离子
动力学
马库斯理论
化学物理
氧气
纳米技术
反应速率常数
无机化学
电极
物理化学
催化作用
有机化学
材料科学
电气工程
医学
物理
量子力学
内分泌学
工程类
作者
Sunyhik D. Ahn,Ceren Zor,Sixie Yang,Marco Lagnoni,Daniel Dewar,Tammy Nimmo,Chloe Chau,Max Jenkins,Alexander J. Kibler,Alexander Pateman,Gregory J. Rees,Xiangwen Gao,Paul Adamson,Nicole Grobert,Antonio Bertei,Lee Johnson,Peter G. Bruce
出处
期刊:Nature Chemistry
[Springer Nature]
日期:2023-06-01
卷期号:15 (7): 1022-1029
被引量:14
标识
DOI:10.1038/s41557-023-01203-3
摘要
Although Li–air rechargeable batteries offer higher energy densities than lithium-ion batteries, the insulating Li2O2 formed during discharge hinders rapid, efficient re-charging. Redox mediators are used to facilitate Li2O2 oxidation; however, fast kinetics at a low charging voltage are necessary for practical applications and are yet to be achieved. We investigate the mechanism of Li2O2 oxidation by redox mediators. The rate-limiting step is the outer-sphere one-electron oxidation of Li2O2 to LiO2, which follows Marcus theory. The second step is dominated by LiO2 disproportionation, forming mostly triplet-state O2. The yield of singlet-state O2 depends on the redox potential of the mediator in a way that does not correlate with electrolyte degradation, in contrast to earlier views. Our mechanistic understanding explains why current low-voltage mediators (<+3.3 V) fail to deliver high rates (the maximum rate is at +3.74 V) and suggests important mediator design strategies to deliver sufficiently high rates for fast charging at potentials closer to the thermodynamic potential of Li2O2 oxidation (+2.96 V). Ultra-high-capacity Li–air batteries have low Coulombic efficiency and degrade during re-charging, resulting in a poor cycle life. Redox mediators enable improvements but only at undesirably high potentials. The origin of this high potential and the impact of purported reactive intermediates has now been elucidated by resolving the charging mechanism using Marcus theory.
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