Solvothermal Synthesis, Development, and Performance of LiFePO4 Nanostructures

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• 作者：Jianxin Zhu ; Joseph Fiore ; Dongsheng Li ; Nichola M. Kinsinger ; Qianqian Wang ; Elaine DiMasi ; Juchen Guo ; David Kisailus
• 刊名：Crystal Growth & Design
• 出版年：2013
• 出版时间：November 6, 2013
• 年：2013
• 卷：13
• 期：11
• 页码：4659-4666
• 全文大小：708K
• 年卷期：v.13,no.11(November 6, 2013)
• ISSN：1528-7505

文摘

We report the synthesis and nanostructural development of polycrystalline and single crystalline LiFePO₄ (LFP) nanostructures using a solvothermal media (i.e., water鈥搕ri(ethylene glycol) mixture). Crystal phase and growth behavior were monitored by powder and synchrotron X-ray diffraction, as well as transmission electron microscopy (TEM), while particle morphologies were examined using scanning electron microscopy (SEM). Initially, thin (100 nm) platelets of Fe₃(PO₄)₂路8H₂O (vivianite, VTE) formed at short reaction times followed by the nucleation of LFP (20 nm particles) on the metastable VTE surfaces. Upon decrease in pH, primary LFP nanocrystals subsequently aggregated into polycrystalline diamond-like particles via an oriented attachment (OA). With increasing reaction time, the solution pH further decreased, leading to a dissolution鈥搑ecrystallization process (i.e., Ostwald ripening, OR) of the oriented polycrystalline LFP particles to yield evenly sized, single crystalline LiFePO₄. Samples prepared at short reaction durations demonstrated a larger discharge capacity at higher rates compared with the single crystalline particles. This is due to the small size of the primary crystallites within larger secondary LiFePO₄ particles, which reduced the lithium ion diffusion path while subsequently maintaining a high tap density. Understanding the relationship between solution conditions and nanostructural development as well as performance revealed by this study will help to develop synthetic guidelines to enable efficient lithium ion battery performance.