Lithium superoxide encapsulated in a benzoquinone anion matrix
Lithium superoxide encapsulated in a benzoquinone anion matrix
复制标题
DOI：
10.1073/pnas.2019392118
复制
发表时间：
2021-12
期刊：
影响因子：
--
通讯作者：
Matthew J Nava;S. Zhang;Katharine S Pastore;Xiaowen Feng;K. Lancaster;D. Nocera;C. Cummins
中科院分区：
文献类型：
--
作者：
Matthew J Nava;S. Zhang;Katharine S Pastore;Xiaowen Feng;K. Lancaster;D. Nocera;C. Cummins
意义超氧化锂（LiO 2）是锂空气电池的重要中间体，锂空气电池是一种有前途的下一代储能平台。LiO 2的导电性、稳定性和反应性被认为在锂空气电池的可循环性中起着至关重要的作用。我们证明，物理封装的Li 2 O2与适当的氧化还原活性分子可能是一个可行的策略，以访问和稳定的LiO 2在室温下，同时保护溶剂和电解质从有害的反应性来自LiO 2。用氧化还原介体封装不会阻碍界面电子和锂离子传输，并为研究人员提供了一个模拟锂空气电池充电的模型系统。过氧化锂是锂空气电池中的关键存储材料。了解这种盐的氧化还原特性对于提高这类电池的性能至关重要。过氧化锂在暴露于对苯醌（p-C6 H4 O2）蒸汽时，会产生深蓝色。这种蓝色粉末可以正式描述为[Li 2 O2]0.3 · [LiO 2]0.7 · {Li[p-C6 H4 O2]}0.7，尽管光谱表征表明更细微的结构形态。红外光谱、拉曼光谱、电子顺磁共振光谱、漫反射紫外-可见光谱和X射线吸收光谱表明，苯醌自由基阴离子的锂盐在过氧化锂表面形成，表明在固态下发生了电子和锂离子的转移。结果，形成专性超氧化锂并将其封装在具有Li 2 O2核的Li[p-C6 H4 O2]壳中。超氧化锂已被提议作为锂-空气电池的充电/放电循环中的关键中间体，但由于不稳定性而尚未被分离。本文报道的结果提供了具有氧化还原介导的固态过氧化锂/超氧化物化学的快照。
Significance Lithium superoxide (LiO2) is an important intermediate in lithium–air batteries, a promising next-generation energy-storage platform. The conductivity, stability, and reactivity profiles of LiO2 are thought to play a crucial role in the cyclability of lithium–air batteries. We demonstrate that physical encapsulation of Li2O2 with an appropriate redox-active molecule may be a viable strategy to access and stabilize LiO2 at room temperature while simultaneously protecting the solvent and electrolyte from deleterious reactivity derived from LiO2. Encapsulation with a redox mediator does not impede interfacial electron and lithium-ion transport and provides researchers with a model system that recapitulates the charging of a lithium–air cell. Lithium peroxide is the crucial storage material in lithium–air batteries. Understanding the redox properties of this salt is paramount toward improving the performance of this class of batteries. Lithium peroxide, upon exposure to p–benzoquinone (p–C6H4O2) vapor, develops a deep blue color. This blue powder can be formally described as [Li2O2]0.3 · [LiO2]0.7 · {Li[p–C6H4O2]}0.7, though spectroscopic characterization indicates a more nuanced structural speciation. Infrared, Raman, electron paramagnetic resonance, diffuse-reflectance ultraviolet-visible and X-ray absorption spectroscopy reveal that the lithium salt of the benzoquinone radical anion forms on the surface of the lithium peroxide, indicating the occurrence of electron and lithium ion transfer in the solid state. As a result, obligate lithium superoxide is formed and encapsulated in a shell of Li[p–C6H4O2] with a core of Li2O2. Lithium superoxide has been proposed as a critical intermediate in the charge/discharge cycle of Li–air batteries, but has yet to be isolated, owing to instability. The results reported herein provide a snapshot of lithium peroxide/superoxide chemistry in the solid state with redox mediation.