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Structural complexity of layered-spinel composite electrodes for Li-ion batteries
Cabana, Jordi,Johnson, Christopher S.,Yang, Xiao-Qing,Chung, Kyung-Yoon,Yoon, Won-Sub,Kang, Sun-Ho,Thackeray, Michael M.,Grey, Clare P. Cambridge University Press (Materials Research Soc 2010 Journal of materials research Vol.25 No.8
<P>The complexity of layered-spinel <I>y</I>Li2MnO3·(1 - <I>y</I>)Li1+<I>x</I>Mn2-<I>x</I>O4 (Li:Mn = 1.2:1; 0 ≤ <I>x</I> ≤ 0.33; <I>y</I> ≥ 0.45) composites synthesized at different temperatures has been investigated by a combination of x-ray diffraction (XRD), x-ray absorption spectroscopy (XAS), and nuclear magnetic resonance (NMR). While the layered component does not change substantially between samples, an evolution of the spinel component from a high to a low lithium excess phase has been traced with temperature by comparing with data for pure Li1+<I>x</I>Mn2-<I>x</I>O4. The changes that occur to the structure of the spinel component and to the average oxidation state of the manganese ions within the composite structure as lithium is electrochemically removed in a battery have been monitored using these techniques, in some cases in situ. Our <SUP>6</SUP>Li NMR results constitute the first direct observation of lithium removal from Li2MnO3 and the formation of LiMnO2 upon lithium reinsertion.</P>
Ion Exchange of Organic Ionic Compounds in Photoresist
Ryu, Eui-Hyun,Hong, Chang-Young,Jang, Min Kyung,Kim, Myung-Yeol,Kim, Dong Yong,Ahn, Jae Yun,Lim, Hae-Jin,Jeon, Hyun,Clark, Michael,Thackeray, James TECHNICAL ASSOC OF PHOTOPOLYMERS JAPAN 2015 フォトポリマ-懇話會誌= Journal of photopolymer science and t Vol.28 No.5
Muhammad, Shoaib,Kim, Hyunchul,Kim, Yunok,Kim, Donghwi,Song, Jay Hyok,Yoon, Jaegu,Park, Jin-Hwan,Ahn, Sung-Jin,Kang, Sun-Ho,Thackeray, Michael M.,Yoon, Won-Sub Elsevier 2016 Nano energy Vol.21 No.-
<P><B>Abstract</B></P> <P>The reaction mechanism of a high capacity lithium- and manganese-rich metal oxide, 0.4Li<SUB>2</SUB>MnO<SUB>3</SUB>–0.6LiMn<SUB>0.5</SUB>Ni<SUB>0.5</SUB>O<SUB>2</SUB>, has been investigated at the atomic level. High-resolution synchrotron X-ray powder diffraction (HRPD) and X-ray absorption spectroscopy (XAS) were used, respectively, to evaluate the electrochemical charge and discharge reactions in terms of local and bulk structural changes, and variations in the oxidation states of the transition metal ions. Ni K-edge XAS data indicate the participation of nickel in reversible redox reactions, whereas Mn K-edge absorption spectra show that the manganese ions do not participate in the electrochemical reactions. Rietveld refinements of the oxygen occupancy during charge and discharge provide evidence of reversible oxygen release and re-accommodation by the host structure; this unique oxygen participation is likely the main reason for the anomalously high capacity of these electrodes. The HRPD data also show that during the early cycles, characteristic peaks of the Li<SUB>2</SUB>MnO<SUB>3</SUB> component disappear when charged to 4.7V, but reappear on discharge to 2.5V, consistent with a reversible lithium and oxygen extraction process. The results provide new insights into the charge compensation mechanisms that occur when high capacity, lithium- and manganese-rich electrode materials are electrochemically cycled – a topic that is currently being hotly debated in the literature.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Anomalous high capacity of Li- and Mn-rich electrodes has been probed by HRPD and XAS. </LI> <LI> Reversible oxygen release and re-accommodation by the host structure accounts, at least in part, for the unusual high capacity. </LI> <LI> The Li<SUB>2</SUB>MnO<SUB>3</SUB> character of Li- and Mn-rich metal oxide structures is preserved during the initial cycles. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>