Publications (2)42.75 Total impact
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Article: LiCoO2 Concaved Cuboctahedrons from Symmetry-Controlled Topological Reactions
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ABSTRACT: Morphology control of functional materials is generally performed by controlling the growth rates on selected orientations or faces. Here, we control particle morphology by “crystal templating”: by choosing appropriate precursor crystals and reaction conditions, we demonstrate that a material with rhombohedral symmetry—namely the layered, positive electrode material, LiCoO2—can grow to form a quadruple-twinned crystal with overall cubic symmetry. The twinned crystals show an unusual, concaved-cuboctahedron morphology, with uniform particle sizes of 0.5−2 μm. On the basis of a range of synthetic and analytical experiments, including solid-state NMR, X-ray powder diffraction analysis and HRTEM, we propose that these twinned crystals form via selective dissolution and an ion-exchange reaction accompanied by oxidation of a parent crystal of CoO, a material with cubic symmetry. This template crystal serves to nucleate the growth of four LiCoO2 twin crystals and to convert a highly anisotropic, layered material into a pseudo-3-dimensional, isotropic material.Journal of the American Chemical Society 12/2010; · 9.91 Impact Factor -
Article: In situ NMR observation of the formation of metallic lithium microstructures in lithium batteries.
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ABSTRACT: Lithium metal has the highest volumetric and gravimetric energy density of all negative-electrode materials when used as an electrode material in a lithium rechargeable battery. However, the formation of lithium dendrites and/or 'moss' on the metal electrode surface can lead to short circuits following several electrochemical charge-discharge cycles, particularly at high rates, rendering this class of batteries potentially unsafe and unusable owing to the risk of fire and explosion. Many recent investigations have focused on the development of methods to prevent moss/dendrite formation. In parallel, it is important to quantify Li-moss formation, to identify the conditions under which it forms. Although optical and electron microscopy can visually monitor the morphology of the lithium-electrode surface and hence the moss formation, such methods are not well suited for quantitative studies. Here we report the use of in situ NMR spectroscopy, to provide time-resolved, quantitative information about the nature of the metallic lithium deposited on lithium-metal electrodes.Nature Material 06/2010; 9(6):504-10. · 32.84 Impact Factor
