Abstract
Li- and Mn-rich cathode materials win huge attentions due to their extremely high capacity and unique solid solution composite structure. As a composition contains two or more phase, the compatibility of these phases would be critical points to promise high capacity output. We chose both layered structures which have similar oxygen ion arrangement as framework and distinct cations distribution, 1 to found the xLi2MnO3-yLiNi1/3Co1/3Mn1/3O2 cathode materials. From former researches, 2 Li was always used to adjust the ratio of the layered and monoclinic phase. Thus, in this paper the Li content was changed to adjust the composition of the two contained phase. All the precursors of three samples were synthetized though co-precipitation route, after drying and mixing with lithium, the powders were sintered at 900 oC for 15h to obtain the final products. The XRD (X-ray diffraction) were used to investigate the order of crystal structure of these cathode materials, indicating that the ordering of the layered structure was improved with Li content decreased. The intensity of characteristic peaks for monoclinic phase increases with increasing Li content while the ratio of W rohom /W mono decrease from 4.1565 through 3.240 and 3.0789 to 2.44, these results combined with the broaden and split more clearly of (006)/(102) and (108)/(110) doublets indicate the formation of more ordered layered structure as more Li sites were occupied. Electrochemical performance was evaluated by galvanostatic mode at C/10 with cutoff voltage of 4.8V. Results show that the more Li in the structure, the lower polarizing voltage can be obtained, otherwise, the much lower first cycle coulombic efficiency accompanied. Rate capability (not shown) can be improved but with much faster capacity fade and voltage decay. Reference Chen, Y.; Chen, Z.; Xie, K., Effect of Annealing on the First Cycle Performance and Reversible Capabilities of Lithium-Rich Layered Oxide Cathodes. The Journal of Physical Chemistry C 2014.Watanabe, S.; Kinoshita, M.; Nakura, K., Capacity fade of LiNi(1−x−y)CoxAlyO2 cathode for lithium-ion batteries during accelerated calendar and cycle life test. I. Comparison analysis between LiNi(1−x−y)CoxAlyO2 and LiCoO2 cathodes in cylindrical lithium-ion cells during long term storage test. J. Power Sources 2014, 247 (0), 412-422. Figure 1
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