373831 Anomalous Decrease in Structural Disorder Due to Charge Redistribution in Cr-Doped Li4Ti5O12 Negative-Electrode Materials for High-Rate Li-Ion Batteries

Monday, November 17, 2014
Galleria Exhibit Hall (Hilton Atlanta)
Jihwan Choi, School of Mechanical Engineering, Pusan National University, Pusan, South Korea

Since one of the main drawbacks of Li4Ti5O12 as a negative-electrode material is its low electronic conductivity, several researchers have attempted to improve the conductivity by narrowing the band gap through transition-metal doping. Herein, we report another, more significant effect of doping in addition to the band gap narrowing, namely, an anomalous decrease in the structural disorder in Li4Ti5O12 upon Cr3+ion doping. Although it is generally recognized that doping with heterogeneous elements increases the structural disorder, the Cr3+ion doping in Li4Ti5O12 demonstrated an unexpected structural phenomenon. From the results of various structural analyses using a synchrotron beam, such anomalous structural changes were revealed to originate from charge redistribution at nearby Ti4+ions. Finally, the capacity was markedly enhanced, especially at high C-rates (125 mAh/g for 10Ccharge/10Cdischarge, 145 mAh/g for 1Ccharge/50Cdischarge) because of both the band gap narrowing and the increased ionic diffusivity due to the decreased structural disorder, but was decreased instead for too-high doping levels.

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