芳香族化合物碳源對磷酸亞鐵鋰電池性能之影響; Effects of Various Aromatic Compounds on the Performance of LiFePO4/C Composite Cathode by a Solid State Method

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题名:	芳香族化合物碳源對磷酸亞鐵鋰電池性能之影響;Effects of Various Aromatic Compounds on the Performance of LiFePO4/C Composite Cathode by a Solid State Method
作者:	王冠文;Guan-wen Wang
贡献者:	化學工程與材料工程研究所
关键词:	聯苯;磷酸亞鐵鋰;LiFePO4;Acenaphthene
日期:	2010-06-22
上传时间:	2010-12-08 13:35:05 (UTC+8)
出版者:	國立中央大學
摘要:	磷酸亞鐵鋰 (LiFePO4)的電子導電度只有10-9 至10-10 S cm-1，導致初始電容量較低及承受大電流能耐較差。為了提升磷酸亞鐵鋰的電池性能，藉由高溫固態法，並添加不同苯環數目芳香族化合物，製備磷酸亞鐵鋰/碳複合材料，其中以15 wt.%聯苯(Acenaphthene, C12H10)改質，於0.2 C及1 C 下，分別獲得初始放電電容量157 mAh g-1 及125 mAh g-1。另外，它展示極佳的循環穩定度，於0.2 C 下，經過100 次循環數測試後，放電電容量仍有152 mAh g-1 (初始放電電容量的95.6 %)，每個循環數的衰退放電電容量比率為0.044 %。經 HR-TEM 觀測， 2 個苯環數目的碳源聯苯所合成材料，碳層均勻包覆在LiFePO4 顆粒表面，且碳層厚度為 5~10 nm；當添加具有3 個苯環數的芳香族化合物碳源蔥時，碳層並未均勻包覆於LiFePO4 材料表面，且碳層厚度為20nm，顯示聯苯所合成LiFePO4/C 材料，碳層可均勻包覆在LiFePO4 顆粒表面，且碳層厚度較薄。聯苯所合成材料，於充放電截止電壓4.6/2.0 V 測試，經充放電速率0.2 C及5 C 的循環測試，可回復原始電容量，顯示材料結構穩定，並在10 C 之充放電速率測試下，仍有 30 mAh g-1 的放電電容量。吾人以 XANES 及XPS 觀測，以聯苯為碳源，於不同煆燒溫度773 K、873 K 及973 K 所合成的三個樣品，XANES 與XPS 光譜圖中顯示鐵原子皆為 Fe2+成分，無Fe3+存在。 Electronic conductivity of pristine LiFePO4 is only 10-9-10-10 S cm-1, which leads to initial capacity loss and poor rate capability. To improve the electrochemical properties of LiFePO4 powders, LiFePO4/C composite powders were prepared with various aromatic compounds by a high temperature solid-state method. LiFePO4 powders coated with 15 wt.% Acenaphthene (C12H10) exhibited initial discharge capacities of 157 mAh g-1 and 125 mAh g-1, at 0.2 and 1 C-rates, respectively. In addition, it showed excellent cycle stability. Even after 100 cycles at 0.2 C, a discharge capacity of 152 mAh g-1 was obtained (95.6 % of its initial value) with lower capacity fading of only 0.044 % per cycle. A series of residual carbons on the surface of prepared LiFePO4 materials originating from the pyrolysis of different aromatic compounds were characterized by field-emission scanning electron microscopy, high resolution transmission electron microscopy, energy dispersive spectrometry, and total organic carbon analysis. Their electrochemical properties were investigated by cyclic voltammetry, four-point probe conductivity measurements, and galvanostatic charge and discharge tests.
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