Morphology-controlled LiFePO₄ cathodes by a simple polyol reaction for Li-ion batteries

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• 作者：Vinod Mathew ; Muhammad Hilmy Alfaruqi ; Jihyeon Gim ; Jinju Song ; Sungjin Kim ; Docheon Ahn ; Jaekook Kim
• 关键词：Polyol ; LiFePO4 ; Nanorod bundles ; Secondary structures ; Cathodes ; Lithium-ion batteries
• 刊名：Materials Characterization
• 出版年：March, 2014
• 年：2014
• 卷：89
• 期：Complete
• 页码：93-101
• 全文大小：1514 K

文摘

LiFePO₄ cathodes with secondary nanorod structures and nano-plate morphologies were synthesized by varying the reaction time in a polyol refluxing process without the use of any characteristic structure directing agents. The X-ray diffraction studies indicate the highly crystalline nature of the prepared samples. Electron microscopy investigations revealed the morphology of the samples after 1 to 16 h polyol reaction to be secondary nanorod bundles whereas the olivine sample recovered after 32 h polyol reaction displayed nano-plate morphology. The dimensions of the obtained samples varied from a few tens to a few hundred nanometers. When employed in a lithium test cell, the LiFePO₄ cathodes reacted for 1, 4, 8, 16 and 32 h delivered discharge capacities of 161, 162, 171, 143 and 155 mAhg^鈭?#xA0;1, respectively, with a well-defined plateau at 3.4 V and impressive capacity retentions until 50 cycles. Interestingly, among the prepared electrodes, the LiFePO₄ nanorod bundle cathode prepared under 1 h reaction time maintained the highest average reversible capacities of 123 and 103 mAhg^鈭?#xA0;1 at C-rates as high as 3.2 and 6.4 C. The crystal growth mechanism during the polyol refluxing method can be explained by the stages of precursor dissolution and nucleation, oriented crystal growth and alignment by self-assembly, aggregation and partial dissolution and complete re-crystallization.