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Layered LiNi0.4Mn0.4Co0.18Ti0.02O2 cathode powders were ball-milled for various lengths of time. The structural properties of the pristine and milled powders, which have different particle sizes were examined with X-ray diffraction, soft X-ray absorption spectroscopy, and transmission electron microscopy to determine the effect of milling on structure. Electrochemical testing in half-cells was also carried out and shows that milling plays an important role in the performance of these cathode materials; as milling time increases, there is a decrease in initial discharge capacity. The first cycle irreversible capacity also increases for milled samples, as does capacity loss upon cycling under some regimes. The electrochemical degradation is strongly correlated with damage to the lamellar structure of cathode particles induced by milling, and lithium carbonate formation. (c) The Author(s) 2019. Published by ECS. ; Office of Vehicle Technologies of the U.S. Department of Energy [DE-AC02-05CH11231]; National Natural Science Foundation of China [51101023]; Jiangsu Province Science and Technology Project [BY2016029-07]; United States Government ; This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. The synchrotron X-ray characterization of this work was performed at the Stanford Synchrotron Radiation Lightsource (SSRL), a Directorate of SLAC National Accelerator Laboratory and an Office of Science User Facility operated for the U.S. Department of Energy Office of Science by Stanford University. TP is grateful for the financial support of the National Natural Science Foundation of China under grant No. 51101023. The research was partially funded by the Jiangsu Province Science and Technology Project (BY2016029-07). TP also thanks the China Scholarship Council and the Six Talent Peaks Project of Jiangsu, and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD). This author also acknowledges the contribution of Hua Guo from Rice University for help constructing Figure 6 and the contribution of Xiangyun Song from Lawrence Berkeley National Laboratory for the BET measurement.; This document was prepared as an account of work sponsored by the United States Government. While this document is believed to contain correct information, neither the United States Government nor any agency thereof, nor the Regents of the University of California, nor any of their employees, makes any warranty, express or implied, or assumes any legal responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by its trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or the Regents of the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof or the Regents of the University of California.

In the spinel oxide cathode family, LiNi0.5Mn1.5O4 (LNMO) shows a high operating voltage (approximate to 4.7 V vs Li/Li+) and excellent Li-ion mobility with stable 3D conducting channels. Ni/Mn cation disordered and ordered phases usually coexist in LNMO materials, and they have distinct structural and electrochemical properties, resulting in different battery performances for LNMO materials with different phase compositions. Identifying the correlation between phase compositions and electrochemical properties is of significance to the improvement of battery performance and understanding of degradation mechanisms. Herein, the disordered/ordered phase compositions in LNMO materials are tailored by post-annealing strategies and their impacts on electrochemical performance and degradation mechanisms from the surface to the bulk are systematically investigated. The ordered phase increases rapidly as Mn3+ is oxidized to Mn4+ through a post-annealing process. LNMO with an intermediate fraction of disordered and ordered phases gives rise to improved cycling stability. This article further reports that a high ordered phase fraction can preferentially protect Ni from dissolution during cycling. However, these results suggest that the transition metal dissolution and surface structural change of LNMO do not exhibit a direct correlation with cycling stability. These results indicate the capacity fading mainly correlates with the bulk structural distortion, leading to decreased Li-ion kinetics. ; Department of Chemistry startup funds; U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-AC02-76SF00515]; Applied Battery Research (ABR) for Transportation Program; U.S. DOE Office of Science, Office of Basic Energy Sciences [DE-AC05-00OR22725]; U.S. DOE Office of Science User Facility [DE-AC02-05CH11231]; Walter Ahlstrom Foundation; European Union's Horizon 2020 research and innovation programme under the Marie Skodowska-Curie grant [841621] ; Published version ; The work at Virginia Tech was ...