Temperature Dependence of Aliovalent-Vanadium Doping in LiFePO4 Cathodes

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• 作者：Katharine L. Harrison ; Craig A. Bridges ; Mariappan Parans Paranthaman ; Carlo U. Segre ; John Katsoudas ; Victor A. Maroni ; Juan Carlos Idrobo ; John B. Goodenough ; Arumugam Manthiram
• 刊名：Chemistry of Materials
• 出版年：2013
• 出版时间：March 12, 2013
• 年：2013
• 卷：25
• 期：5
• 页码：768-781
• 全文大小：690K
• 年卷期：v.25,no.5(March 12, 2013)
• ISSN：1520-5002

文摘

Vanadium-doped olivine LiFePOb>4b> cathode materials have been synthesized by a low-temperature microwave-assisted solvothermal (MW-ST) method at 鈮?00 掳C. The samples have been extensively characterized by neutron/X-ray powder diffraction, infrared and Raman spectroscopy, elemental analysis, electron microscopy, and electrochemical techniques. The compositions of the as-synthesized materials were found to be LiFeb>1鈥?x/2b>Vb>xb>鈻?sub>x/2b>POb>4b> (0 鈮?x 鈮?0.2) with the presence of a small number of lithium vacancies (鈻? charge-compensated by V⁴⁺, not Fe³⁺, leading to an average oxidation state of 3.2+ for vanadium. The vacancies on the Fe site likely provide an additional conduction pathway for Li⁺ ions to transfer between neighboring 1D conduction channels along the crystallographic b axis. Heating the pristine 15% V-doped sample in inert or reducing atmospheres led to a loss of vanadium from the olivine lattice with the concomitant formation of a Lib>3b>Vb>2b>(POb>4b>)b>3b> impurity phase; after phase segregation, a partially V-doped olivine phase remained. For comparison, V-doped samples were also synthesized by conventional ball milling and heating, but only 10% V could be accommodated in the olivine lattice in agreement with previous studies. The higher degree of doping realized with the MW-ST samples demonstrates the temperature dependence of the aliovalent-vanadium doping in LiFePOb>4b>.<br>

Keywords:

olivine cathodes; LiFePOb>4b>; vanadium doping; lithium-ion batteries; cathodes