Abstract: Layered alkali transition metal oxides (i.e., LiMO 2 and NaMO 2 , M=transition metal) are the premier class of cathode materials in lithium- and sodium-ion battery system. The safety characteristics of LiMO 2 cathode based LIBs are one of the most critical barriers to be overcome for the large scale application such as EV. One of the main reasons that might cause safety hazards of the LIB is associated with the thermal instability of charged Li 1-x MO 2 cathode materials, which is related to the occurrence of exothermic reactions between flammable electrolyte and liberating oxygen from charged Li 1-x MO 2 at high temperature. Based on the structural homology between the layered LiMO 2 and NaMO 2 , we expect that the investigation of thermal stability of charged Na 1-x MO 2 cathode materials is also important for the practical use of SIBs. However, few attentions have been paid on safety issue of SIBs.  In this study, the thermal stability of charged Na 1-x MO 2 cathode materials is investigated by using combined in situ time-resolved X-ray diffraction and mass spectroscopy (TR-XRD/MS), which allows simultaneous observation of the structural changes and gas species that are evolved during thermal decomposition of charged cathode materials, especially O 2 gas in our interest. In addition, the ex situ/in situ X-ray absorption spectroscopy (XAS) has been also utilized to look at the local and electronic structural changes occurring during thermal decomposition in an elemental selective way. By utilizing combined X-ray techniques, we are able to get better understanding of structural and electronic structure changes in charged cathode materials during thermal decomposition. In this presentation, the thermal decomposition behavior of charged Na 1-x MO 2 (M=Co, Cr) cathodes will be covered. Acknowledgement The work done at Brookhaven National Lab. was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. DOE under Contract No. DE-SC0012704.

Abstract: Layer structured mixed transition metal oxides LiNi x Mn y Co y O 2 (x+y+z=1, NMC) have been widely studied as promising cathode materials for Li-ion batteries due to their superior properties, better thermal stability, lower cost and higher capacity comparing to LiCoO 2 , which is the widely used cathode material for Li-ion cells. A typical NMC cathode with a composition of 1:1:1 (LiNi 1/3 Mn 1/3 Co 1/3 O 2 ) is already being used in commercial lithium-ion battery cells. However, more systematic studies on the structure-performance relationship of the NCM materials are needed. It is critical to understand the role of each element in electrochemical performance in terms of the capacity, rate capability, cycling and calendar lifes as well as safety characteristics. In this regard, we present here a systematic study on the structural changes that occur in the NMC cathode materials with several different compositions such as NMC = 333, 433, 532, 622 and 811 during charge using combined in-situ synchrotron based X-ray techniques. While in situ X-ray diffraction (XRD) was used to track the average bulk crystal structural changes, in situ X-ray absorption spectroscopy (XAS) was applied to monitor the electronic structure and local structure changes around each transition metal element (Ni, Mn and Co) in the NMC cathode during charge. In addition, time-resolved XRD and Quick-EXAFS were also used for monitoring its structural changes and kinetic property of each transition metal upon charge at different C rates (C/10 to 30C). Detailed results including in situ XRD and XAS on the NMC materials with various NMC compositions during charge will be present. Acknowledgement The work done at Brookhaven National Lab. was supported by the U.S. Department of Energy, the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies under Contract Number DEAC02-98CH10886.

Abstract: Abstract not Available.

Abstract: Introduction James and Goodenough first introduced layer-structured Li 2 MoO 3 as a lithium-battery cathode material [1]. It has a disordered NaFeO 2 structure (; a = 2.884 Å, c = 14.834 Å) consisting of a cubic close-packed oxygen cations with basal planes of octahedral sites alternatively filled with Li ions (3a sites) and a randomly distributed mixture of 1/3 Li (3b sites) and 2/3 Mo (3b sites) forming a Li-Mo layer(with a 1:2 Li:Mo ratio), in which the Mo ions forming disordered Mo 3 O 13 clusters rather than isolated Mo ions.[1-5] The theoretical capacity of the Li 2 MoO 3 reaches 339 mAh g -1 based on the Mo 4+ /Mo 6+ redox reaction alone ( i.e. without oxidation of the O 2- anions) and the Mo 4+ /Mo 6+ redox reaction potential is much lower than that of the oxygen release in Li 2 MnO 3 . Therefore, Li 2 MoO 3 is expected to be a good component in building a new layer-structured x Li 2 MoO 3 ·(1- x )Li M O 2 system as high-capacity cathode materials. Here we report the structural studies and charge compensation of Li 2 MoO 3 during the initial charge and discharge. The close to fully reversible structural changes and Mo ion migration, originated from the charge compensation of Mo ions in both the Mo-O and Mo-Mo covalent bonds in the Mo 3 O 13 cluster, make the Li 2 MoO 3 an appropriate alternative of Li 2 MnO 3 in constructing new x Li 2 MoO 3 ·(1- x )Li M O 2 cathode materials, which have less irreversible transition metal migration and oxygen evolution. The findings in this work will also shed light on the fundamental understandings of the relationships between the performance and structure changes, as well as on the new approaches in developing lithium-rich cathode materials with both high energy density and long cycle life. Results and discussion To understand the structural changes of Li 2 MoO 3 during lithium extraction, in situ x-ray diffraction (XRD) and X-ray absorption (XAS) spectroscopy at Mo K-edge were used to study the crystal structure and valence state as well as local structural changes of Mo ions in charging process. The X-ray absorption near edge structure (XANES) spectra of the Mo K-edge during charge show a continuous increase of the pre-edge peaks indicates the increased distortion of Mo-O 6 octahedral. The white line of the K-edge shifted to the higher energy gradually, suggesting the increasing oxidation state of Mo ions upon charge. Compare with the Mo K-edge XANES data of the MoO 2 and MoO 3 references, it can be estimated that the Mo ions were oxidized from Mo 4+ to average oxidation state close to Mo 6+ . More detailed results will be discussed in the presentation. Acknowledgement This work was supported by the U.S. Department of Energy, the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies under Contract No. DE-AC02-98CH10886. Use of the National Synchrotron Light Source was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886. The work at Institute of Physics, Chinese Academy of Sciences was supported by the National Natural Science Foundation (No. 51372268) of China and the National 973 Program of China (2009CB 220100). References [1] A. C. W. P. James and J. B. Goodenough, J. Solid State Chem., 1988, 76, 87.. [2] S. J. Hibble and I. D. Fawcett, Inorg. Chem., 1995, 34, 500. [3] S. J. Hibble, I. D. Fawcett and A. C. Hannon, Acta Cryst., 1997, B53, 604. [4] S. J. Hibble, A. C. Hannon and I. D. Fawcett, J. Phys.: Condens. Matter, 1999, 11, 9203 [5] W. H. McCarroll, L. Katz and R. Ward, J. Am. Chem. Soc., 1957, 79, 5410.

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Abstract: Abstract not Available.

Abstract: Li 2 MnO 3 stabilizes the structure of Li M O 2 ( M = Mn, Ni, Co, etc .) and makes Li-rich layer-structured x Li 2 MnO 3 ·(1- x )Li M O 2 (0 〈 x 〈 1.0, M = Mn, Ni, Co, etc .) composites (or solid solutions) become potential cathode materials for high energy density lithium ion batteries. However, as Mn 4+ is inactive in Li 2 MnO 3 , the charge compensation from O 2- ions during the initial delithiation and the irreversible layer-to-spinel structural transition in the subsequent lithiation makes the composite suffer from drawbacks such as low initial coulombic efficiency, discharge voltage and energy density falling, and poor rate performance during cycling as well as safety hazard in the initial cycle. Although surface modification, atomic substitution and optimization of synthesis strategies have been pursued to improve the performances of the x Li 2 MnO 3 ·(1- x )Li M O 2 composites, the inherent drawbacks of Li 2 MnO 3 component have not been, and cannot, overcome. Here we introduce Li 2 MoO 3 with disordered NaFeO 2 structure ( R -3 m ) as a prospective alternation of Li 2 MnO 3 for designing novel Li-rich cathode materials x Li 2 M ´O 3 ·(1- x )Li M O 2 . In this report, the structural transition and charge compensation of Li 2 MoO 3 during the initial charge and discharge were investigated with STEM and synchrotron in situ XRD and XAS techniques. It is shown that, during the initial delithiation, solid-solution reaction and two-phase reaction (slipped O3 → faulted O1) go in series due to charge compensation from Mo 4+ ions in both the Mo-O and Mo-Mo covalent bonds in the Mo 3 O 13 cluster accompanied with the Mo ion migration from Li-2Mo layer to Li layer. In the subsequent lithiation, its structure is recovered to a Li-insufficient O3 type Li 2- x MoO 3 ( x = 0.50) due to the incomplete reduction of Mo 6+ ions and the nearly reversible migration of the Mo ions at the end of lithiation. Unlike the irreversible oxygen release in deeply delithiated Li 2 MnO 3 , the O K-edge soft XAS of Li 2 MoO 3 illustrates that oxidation of O 2- to O (2-σ )- is nearly reversible and is required dynamically rather than thermodynamically. These features make Li 2 MoO 3 a promising superior alternate in constructing novel Li-rich cathode material with improved structural stability and easy charge compensation. In addition, the contribution of Mo-Mo covalent bond seems to help to maintain the framework of the electrode material by hindering the loss of oxygen. Therefore, the basic findings in this work will also bring new insight on understanding the performance decay and searching for new ways to improve the performance of the conventional x Li 2 MnO 3 ·(1- x )Li M O 2 materials. Acknowledgements This work was financially supported by the National Natural Science Foundation (No. 51372268) of China and the National 973 Program of China (2009CB 220100). The work at Brookhaven National Lab. was supported by the U.S. Department of Energy, the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies under Contract No. DEAC02-98CH10886.

Abstract: Recently, LiNi 0.5 Mn 1.5 O 4 , denoted as LNMO, has attracted a lot of research attention as a promising high-energy density cathode material based on its higher operating voltage at ~4.7V vs. Li + /Li compared to the parent material, LiMn 2 O 4 .[1] On the other hand, the poor cycle and calendar life of LNMO, especially at elevated temperatures, still remain one of the major challenges in its widespread usage. Extensive research has addressed some key factors determining its capacity and rate performance, such as cation ordering, route of synthesis, stoichiometry, heat treatment, particle morphology, particle size, transition metal substitution, and the Li-insertion/de-insertion mechanism of this material.[2-7] Unlike the widely studied electrochemical performance and reaction mechanism, the thermal stability of LNMO, which could greatly impact the safety of LIBs, has received little attention. This lack of interest probably could be attributed to the assumption that the excellent thermal stability of the delithiated LNMO can be naturally inherited from its parent material LiMn 2 O 4 , for which only a subtle structural rearrangement takes place without the oxygen release up to 500 °C in the fully delithiated state.[8] Therefore, Li x Mn 2 O 4 has been regarded as a thermally safer cathode material than layered materials, such as Li x CoO 2 , Li x Ni 0.8 Co 0.15 Al 0.05 O 2 and Li x Ni 1/3 Co 1/3 Mn 1/3 O 2 . All of these structurally layered materials undergo a series of phase transitions with accompanied oxygen release below 300°C in their charged states. However, for LNMO, what was overlooked at is that when a quarter of the Mn is replaced by Ni, the thermodynamics of the material inevitably changes yielding a very different thermal stability than its parent LiMn 2 O 4 . Unfortunately, little research has been published on the thermal stability of LNMO materials and their doped derivatives; the research focus has been on their reactivity with the electrolyte using calorimetric measurements thus far.[9-11] There are very few studies correlating thermal stability neither with structural differences (ordered or disordered) nor with oxygen-releasing structure changes during heating for LNMO. To further understand the thermal stability of both ordered (o-) and disordered (d-) LNMO in the delithiated state, we applied a combination of in situ synchrotron time-resolved x-ray diffraction (TR-XRD) coupled with mass spectroscopy (MS) and in situ x-ray absorption spectroscopy (XAS) during heating. This combination allowed us to simultaneously monitor the phase transformations (by TR-XRD) and the accompanying gas evolution (e.g., oxygen by MS) as well as the local- and electronic-structural changes with an elemental selective capability (by XAS) during thermal decomposition. Through this systematic investigation, the mechanism of thermal decomposition and the oxygen release behavior of (electrochemically) delithiated d- and o-LNMO during heating have been explored in terms of changes in crystal structures, chemical compositions and valance of the transition metals. We also investigated the impact of doping (e.g., Zn and Fe) on the thermal- and electrochemical cycling- stability of LNMO materials using the above in situ x-ray tools. Some of preliminary results regarding doped LNMO materials will also be presented in the meeting. Acknowledgement This work was supported by the U.S. Department of Energy, the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies under Contract No. DE-AC02-98CH10886. Use of the National Synchrotron Light Source was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886. References [1] Zhong, Q. M.; Bonakdarpour, A.; Zhang, M. J.; Gao, Y.; Dahn, J. R. J Electrochem Soc 1997 , 144, 205. [2] Kim, J. H.; Myung, S. T.; Yoon, C. S.; Kang, S. G.; Sun, Y. K. Chem. Mater. 2004, 16, 906. [3] Kunduraci, M.; Al-Sharab, J. F.; Amatucci, G. G. Chem. Mater. 2006, 18, 3585. [4] Xiao, J.; Chen, X. L.; Sushko, P. V.; Sushko, M. L.; Kovarik, L.; Feng, J. J.; Deng, Z. Q.; Zheng, J. M.; Graff, G. L.; Nie, Z. M.; Choi, D. W.; Liu, J.; Zhang, J. G.; Whittingham, M. S. Adv. Mater. 2012, 24, 2109. [5] Song, J.; Shin, D. W.; Lu, Y. H.; Amos, C. D.; Manthiram, A.; Goodenough, J. B. Chem. Mater. 2012, 24, 3101. [6] Ariyoshi, K.; Maeda, Y.; Kawai, T.; Ohzuku, T. J. Electrochem. Soc. 2011, 158, A281. [7] Cabana, J.; Zheng, H. H.; Shukla, A. K.; Kim, C.; Battaglia, V. S.; Kunduraci, M. J. Electrochem. Soc. 2011, 158, A997. [8] Schilling, O.; Dahn, J. R. J. Electrochem. Soc. 1998, 145, 569. [9] Bhaskar, A.; Gruner, W.; Mikhailova, D.; Ehrenberg, H. RSC Advances 2013, 3, 5909. [10] Patoux, S.; Sannier, L.; Lignier, H.; Reynier, Y.; Bourbon, C.; Jouanneau, S.; Le Cras, F.; Martinet, S. Electrochim. Acta 2008, 53, 4137. [11] Xiang, H. F.; Wang, H.; Chen, C. H.; Ge, X. W.; Guo, S.; Sun, J. H.; Hu, W. Q. J. Power Sources 2009, 191, 575.