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RISS 인기검색어
- 검색키워드
- 저자 : Levi Mikhael (검색결과 2 건)
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Kumar Nayak, Prasant,Grinblat, Judith,Levi, Elena,Penki, Tirupathi Rao,Levi, Mikhael,Sun, Yang-Kook,Markovsky, Boris,Aurbach, Doron American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.5
<P>Li- and Mn-rich transition-metal oxides of layered structure are promising cathodes for Li-ion batteries because of their high capacity values, >= 250 mAh g(-1). These cathodes suffer from capacity fading and discharge voltage decay upon prolonged cycling to potential higher than 4.5 V. Most of these Li and Mn-rich cathodes contain Ni in a 2+ oxidation state. The fine details of the composition of these materials may be critically important in determining their performance. In the present study, we used Li1.2Ni0.13Mn0.54Co0.13O2 as the reference cathode composition in which Mn ions are substituted by Ni ions so that their average oxidation state in Li1.2Ni0.13Mn0.54Co0.13O2 could change from 2+ to 3+. Upon substitution of Mn with Ni, the specific capacity decreases but, in turn, an impressive stability was gained, about 95% capacity retention after 150 cycles, compared to 77% capacity retention for Li1.2Ni0.13Mn0.54Co0.13O2 cathodes when cycled at a C/5 rate. Also, a higher average discharge voltage of 3.7 V is obtained for Li1.2Ni0.13Mn0.54Co0.13O2 cathodes, which decreases to 3.5 V after 150 cycles, while the voltage fading of cathodes comprising the reference material is more pronounced. The Li1.2Ni0.13Mn0.54Co0.13O2 cathodes also demonstrate higher rate capability compared to the reference Li1.2Ni0.13Mn0.54Co0.13O2 cathodes. These results clearly indicate the importance of the fine composition of cathode materials containing the five elements Li, Mn, Ni, Co, and 0. The present study should encourage rigorous optimization efforts related to the fine composition of these cathode materials, before external means such as doping and coating are applied.</P>
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Nayak, Prasant Kumar,Grinblat, Judith,Levi, Mikhael D.,Haik, Ortal,Levi, Elena,Talianker, Michael,Markovsky, Boris,Sun, Yang-Kook,Aurbach, Doron American Chemical Society 2015 Chemistry of materials Vol.27 No.7
<P>Li[Ni<SUB>1/3</SUB>Mn<SUB>2/3</SUB>]O<SUB>2</SUB> was synthesized by a self-combustion reaction (SCR), characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy, and studied as a cathode material for Li-ion batteries at 30 °C and 45 °C. The structural studies by XRD and TEM confirmed monoclinic Li[Li<SUB>1/3</SUB>Mn<SUB>2/3</SUB>]O<SUB>2</SUB> phase as the major component, and rhombohedral (LiNiO<SUB>2</SUB>), spinel (LiNi<SUB>0.5</SUB>Mn<SUB>1.5</SUB>O<SUB>4</SUB>), and rock salt Li<SUB>0.2</SUB>Mn<SUB>0.2</SUB>Ni<SUB>0.5</SUB>O as minor components. The content of the spinel phase increases upon cycling due to the layered-to-spinel phase transition occurring at high potentials. A high discharge capacity of about 220 mAh g<SUP>–1</SUP> is obtained at low rate (C/10) with good capacity retention upon cycling. However, LiNi<SUB>0.5</SUB>Mn<SUB>1.5</SUB>O<SUB>4</SUB> synthesized by SCR exhibits a discharge capacity of about 190 mAh g<SUP>–1</SUP> in the potential range of 2.4–4.9 V, which decreases to a value of 150 mAh g<SUP>–1</SUP> after 100 cycles. Because of the presence of the spinel component, Li[Ni<SUB>1/3</SUB>Mn<SUB>2/3</SUB>]O<SUB>2</SUB> cathode material exhibits part of its capacity at potentials around 4.7 V. Thus, it can be considered as an interesting high-capacity and high-voltage cathode material for high-energy-density Li-ion batteries. Also, the Li[Ni<SUB>1/3</SUB>Mn<SUB>2/3</SUB>]O<SUB>2</SUB> electrodes exhibit better electrochemical stability than spinel LiNi<SUB>0.5</SUB>Mn<SUB>1.5</SUB>O<SUB>4</SUB> electrodes when cycled at 45 °C.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2015/cmatex.2015.27.issue-7/acs.chemmater.5b00405/production/images/medium/cm-2015-00405w_0020.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm5b00405'>ACS Electronic Supporting Info</A></P>
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