Lithium-ion (Li-ion) batteries that rely on cationic redox reactions are the primary energy source for portable electronics. One pathway toward greater energy density is through the use of Li-rich layered oxides. The capacity of this class of materials (>270 milliampere hours per gram) has been shown to be nested in anionic redox reactions, which are thought to form peroxo-like species. However, the oxygen-oxygen (O-O) bonding pattern has not been observed in previous studies, nor has there been a satisfactory explanation for the irreversible changes that occur during first delithiation. By using Li2IrO3 as a model compound, we visualize the O-O dimers via transmission electron microscopy and neutron diffraction. Our findings establish the fundamental relation between the anionic redox process and the evolution of the O-O bonding in layered oxides.
Science 18 December 2015:
Vol. 350 no. 6267 pp. 1516-1521
DOI: 10.1126/science.aac8260
http://www.sciencemag.org/content/350/6267/1516
开发高效的充电电池意味着在更小的质量或体积里填充更多的能量。层状锂氧化物是一类有潜力的材料，它可以使电池的容量增加一倍。不过，设计安全长效的电池需要对材料在氧化还原过程中的物理和化学变化有深入的认识。 McCalla 等人通过理论计算和实验相结合的手段，研究了电池中 O-O 二聚体生成的过程，这一过程对提升材料的性质十分关键。作者称，他们的发现为建立层状氧化物中，阴离子形成还原过程与 O-O 成键过程之间的关系打下了基础。（新材料在线）
