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Visualization of O-O peroxo-like dimers in high-capacity layered oxides for Li-ion batteries

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Science  18 Dec 2015:
Vol. 350, Issue 6267, pp. 1516-1521
DOI: 10.1126/science.aac8260

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Peering into cathode layered oxides

The quest for better rechargeable batteries means finding ways to pack more energy into a smaller mass or volume. Lithium layered oxides are a promising class of materials that could double storage capacities. However, the design of safe and long-lasting batteries requires an understanding of the physical and chemical changes that occur during redox processes. McCalla et al. used a combination of experiments and calculations to understand the formation of O-O dimers, which are key to improving the properties of these cathode materials.

Science, this issue p. 1516

Abstract

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.

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