Flame-made Lithium Transition Metal Orthosilicates

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• 作者：Nils Wagner ; Ann Mari Svensson ; Fride Vullum-Bruer ; ^{vullum@nt.ntnu.no" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Li-ion battery ; Cathode ; Polyanion ; Li2FeSiO4 ; Flame spray pyrolysis
• 刊名：Electrochimica Acta
• 出版年：2016
• 出版时间：10 June 2016
• 年：2016
• 卷：203
• 期：Complete
• 页码：246-256
• 全文大小：4456 K

文摘

Li₂MSiO₄ (M = Fe, Mn, Co) compounds have since their discovery gained increased attention as alternative, inexpensive and inherently safe positive electrodes for Li-ion batteries. To meet the required performance for an electrode, sophisticated, complex and time-consuming synthesis measures are required at present. Here, we present a time-efficient and scalable aerosol combustion method with subsequent annealing, leading to nanoscale and carbon-coated Li₂FeSiO₄ and Li₂Fe_0.5Mn_0.5SiO₄. Using liquid-feed flame spray pyrolysis, we demonstrate synthesis of orthosilicate materials, with phase purities exceeding 95 wt. % according to Rietveld quantifications, in a relatively short time. The importance of the precursor concentration, in order to obtain loosely agglomerated nanoparticles, is discussed and the long-term performance is investigated. In the case of Li₂FeSiO₄, the optimised precursor concentration yielded particles of about 30 nm, which delivered an initial discharge capacity of up to 150 mAhg⁻¹ at 60 °C and C/20. Furthermore, over 50% of the capacity is retained at a high rate of 5C, and long-term cycling showed outstanding capacity retention of over 90% after 300 cycles at a moderate rate of C/2. Li₂Fe_0.5Mn_0.5SiO₄ on the other hand_, was shown to suffer from a severe capacity fade, and upon prolonged cycling the redox activity can be attributed solely to Fe.