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In situ x-ray diffraction studies of a new LiMg{sub 0.125}Ni{sub 0.75}O{sub 2} cathode material

Description: A Synchrotron x-ray source was used for In Situ x-ray diffraction studies during charge on a new LiMg{sub 0.125}Ti{sub 0.125}Ni{sub 0.75} cathode material synthesized by FMC Corp. It had been demonstrated by Gao that this new material has superior thermal stability than LiNiO{sub 2} and LiCo{sub 0.2}Ni{sub 0.8}O{sub 2} at over-charged state. In this current paper, studies on the relationship between the structural changes and thermal stability at over-charged state for these materials are presented. For the first time, the thermal stability of these materials are related to their structural changes during charge, especially to the formation and lattice constant change of a hexagonal phase (H3). The spectral evidence support the hypothesis that the improvement of thermal stability is obtained by suppressing the formation of H3 phase and reducing the shrinkage of its lattice constant c when charged above 4.3 V.
Date: July 1, 1999
Creator: Yang, X.Q.; Sun, X.; McBreen, J.; Gao, Y.; Yakovleva, M.V.; Xing, X.K. et al.
Partner: UNT Libraries Government Documents Department

In Situ X-ray Diffraction Studies of Cathode Materials in Lithium Batteries

Description: There is an increasing interest in lithiated transition metal oxides because of their use as cathodes in lithium batteries. LiCoO{sub 2}, LiNiO{sub 2} and LiMn{sub 2}O{sub 4} are the three most widely used and studied materials, At present, although it is relative expensive and toxic, LiCoO{sub 2} is the material of choice in commercial lithium ion batteries because of its ease of manufacture, better thermal stability and cycle life. However, the potential use of lithium ion batteries with larger capacity for power tools and electric vehicles in the future will demand new cathode materials with higher energy density, lower cost and better thermal stability. LiNiO{sub 2} is isostructural with LiCoO{sub 2}. It offers lower cost and high energy density than LiCoO{sub 2}. However, it has much poorer thermal stability than LiCoO{sub 2}, in the charged (delithiated) state. Co, Al, and other elements have been used to partially replace Ni in LiNiO{sub 2} system in order to increase the thermal stability. LiMn{sub 2}O{sub 4} has the highest thermal stability and lowest cost and toxicity. However, the low energy density and poor cycle life at elevated temperature are the major obstacles for this material. In order to develop safer, cheaper, and better performance cathode materials, the in-depth understanding of the relationships between the thermal stability and structure, performance and structure are very important. The performance here includes energy density and cycle life of the cathode materials. X-ray diffraction (XRD) is one of the most powerful tools to study these relationships. The pioneer ex situ XRD work on cathode materials for lithium batteries was done by Ohzuku. His XRD studies on LiMn{sub 2}O{sub 4}, LiCoO{sub 2}, LiNiO{sub 2}, LiNi{sub 0.5}Co{sub 0.5}O{sub 2}, and LiAl{sub x}Ni{sub 1-x}O{sub 2} cathodes at different states of charge have provided important guidelines for the development of these new ...
Date: November 1, 1998
Creator: Yang, X. Q.; Sun, X.; McBreen, J.; Mukerjee, S.; Gao, Yuan; Yakovleva, M. V. et al.
Partner: UNT Libraries Government Documents Department

Studies on Relationship Between Structure of Over-Charge State and Thermal Stability for LiNiO(sub 2) Based Cathode Materials

Description: A synchrotrons x-ray source was used for In Situ x-ray diffraction studies on cathode materials during charge and discharge. Two new cathode materials, LiNi{sub 0.75}Mg{sub 0.125}Ti{sub 0.125}O{sub 2} and LiNi{sub 0.56}Co{sub 0.25}Mg{sub 0.05}Ti{sub 0.05}O{sub 2}, were studied in comparison with LiNiO{sub 2}, and LiCo{sub 0.2}Ni{sub 0.8}O{sub 2}. The relationship between the structural changes and thermal stability at over-charged state has been investigated. For the W time, The thermal stability of these materials are related to their structural changes during charge, especially to the formation of a hexagonal phase H3 with collapsed lattice along ''c'' axis. A hypothesis is proposed that through suppressing the formation of H3 phase when charged above 4.3 V, the thermal stability of the cathode materials can be improved.
Date: October 17, 1999
Creator: Sun, X.; Yang, X. Q.; McBreen, J.; Gao, Y.; Yakovleva, M. V.; Xing, X. K. et al.
Partner: UNT Libraries Government Documents Department