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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 –C 6 H 4 O 2 ) vapor, develops a deep blue color. This blue powder can be formally described as [Li 2 O 2 ] 0.3   · [LiO 2 ] 0.7   · {Li[ p –C 6 H 4 O 2 ]} 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 –C 6 H 4 O 2 ] with a core of Li 2 O 2 . 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 lithiummore »peroxide/superoxide chemistry in the solid state with redox mediation.« less

Most plants, contrary to popular belief, do not waste over 30% of their photosynthate in a futile cycle called photorespiration. Rather, the photorespiratory pathway generates additional malate in the chloroplast that empowers many energy-intensive chemical reactions, such as those involved in nitrate assimilation. Thus, the balance between carbon fixation and photorespiration determines the plant carbon–nitrogen balance and protein concentrations. Plant protein concentrations, in turn, depend not only on the relative concentrations of carbon dioxide and oxygen in the chloroplast but also on the relative activities of magnesium and manganese, which are metals that associate with several key enzymes in the photorespiratory pathway and alter their function. Understanding the regulation of these processes is critical for sustaining food quality under rising CO2 atmospheres.