鋰離子電池高粉體密度鋰鐵磷酸鹽正極之製備與分析

Synthesis and Characterization of High tap-density LiFePO4 Cathode Material for Lithium Ion Batteries

陳文勤(Wen-Chin Chen)

指導教授 ： 吳乃立

國立臺灣大學/工學院/化學工程學研究所/碩士(2010年)

https://doi.org/10.6342/NTU.2010.02281

摘要

摘要
鋰鐵磷酸鹽為一新一代之鋰離子電池正極材料。它具有環保、高安全性以及低原料成本之優點，更被證實具有高功率充放電的能力。雖然有這些優點，鋰鐵磷酸鹽目前最需改善的缺點在於粉體密度(tap density)太低，造成電極片電量密度（即每單位體積粉體提供之電容量）低落。在本論文中，主要合成具有高粉體密度的鋰鐵磷酸鹽正極材料，在實驗設計上，我們將採用兩步驟製程，製備球形且大顆粒鋰鐵磷酸鹽粉體。
第一步驟為共沈澱法，以硝酸鐵、磷酸及氨水混合溶液為起始的反應物製造出大顆粒的磷酸鐵粉體。結果顯示，磷酸鐵粉體的晶貌及顆粒大小分布受到反應條件的影響，其中包括反應時的pH、反應物濃度、攪拌功率密度及顆粒滯留時間。
第二步驟將以固相法製備鋰鐵磷酸鹽。我們以固定劑量比將氫氧化鋰、葡萄糖當碳源與製備好的大顆粒磷酸鐵均勻混合，在高溫的條件下進行反應，使鋰嵌入磷酸鐵，形成高結晶度的鋰鐵磷酸鹽。結果顯示，此兩階段製程可製備出鋰鐵磷酸鹽高達1.5 g/cc之振實密度。此步驟中，我們將深入探討反應溫度、顆粒晶貌、粉體密度及電性的關聯。

關鍵字

鋰離子電池 ； 共沉澱法 ； 粉體密度鋰鐵磷酸鹽 ； 多孔結構

並列摘要

Abstract
Lithium iron phosphate (LiFePO4) is a promising cathode material for lithium ion batteries because it has the advantages of environmental benignity, high safety, and low cost. Despite of these advantages, the main problem of LiFePO4 d is low tap density, which causes very low energy density. This work focuses on the synthesis of LiFePO4 powder with high tap density. A two-step process will be carried out to synthesize spherical and micro-size LiFePO4 particles.
In the first step, Fe(NO3), H3PO4 and NH3 were used as starting materials to prepare FePO4 via co-precipitation method. The result shows that different precipitation conditions, including residence time, pH of reaction, agitation power density, and reactant concentration affect the size and morphology of the FePO4 powder.
In the second step, the FePO4 particles were mixed with a stoichiometric amount of Li source and glucose as the carbon coating source. Olivine powder with tap density greater than 1.5 g/cc had been synthesized. The correlations among the sintering temperature, microstructures, tap density and the electrochemical performance have been studied in detail.

並列關鍵字

Li-ion battery ； Co-precipitation ； tap density ； LiFePO4 ； porous structure

參考文獻

1. J. M. Tarascon and M. Armand, "Issues and challenges facing rechargeable lithium batteries," Nature, vol. 414, pp. 359-367, 2001.

2. K. M. Abraham, D. M. Pasquariello, and F. J. Martin, "Mixed ether electrolytes for secondary lithium batteries with improved low temperature performance," Journal of the Electrochemical Society, vol. 133, pp. 661-666, 1986.

3. A. J. Jacobson, R. R. Chianelli, and M. S. Whittingham, " Amorphous molybdenum-disulfide cathodes," Journal of the Electrochemical Society, vol. 126, pp. 2277-2278, 1979.

4. M. S. Whittingham and M. B. Dines, " Normal-butyllithium-effective, general cathode screening agent," Journal of the Electrochemical Society, vol. 124, pp. 1387-1388, 1977.

5. M. Lazzari and B. Scrosati, "A cyclable lithium organic electrolyte cell based on two intercalation electrodes," Journal of the Electrochemical Society, vol. 127, pp. 773-774, 1980.