(中南大學 冶金科學與工程學院， 長沙 410083)
摘 要: 以碳凝膠作為碳添加劑， 采用固相法制備了復(fù)合型LiFePO4/C鋰離子電池正極材料。研究了不同摻碳量對樣品性能的影響。 利用X射線衍射儀、 掃描電鏡和碳硫(質(zhì)量分數(shù))分析方法對所得樣品的晶體結(jié)構(gòu)、 表面形貌、 含碳量進行分析研究。 結(jié)果表明： 樣品中的碳含量（質(zhì)量分數(shù)）分別為0％、 5％、 10％、 22％， 所得樣品均為單一的橄欖石型晶體結(jié)構(gòu)， 碳的加入使LiFePO4顆粒粒徑減小。另外， 碳分散于晶體顆粒之間， 增強了顆粒之間的導電性。 合成樣品的電化學性能測試結(jié)果表明， 摻碳后的LiFePO4放電比容量和循環(huán)性能都得到顯著改善。其中， 含碳量為22％的LiFePO4/C在0.1 C倍率下放電， 首次放電容量達 43.4 mA·h/g， 充放電循環(huán)6次后電容量為142.7 mA·h/g， 容量僅衰減0.7%。
關(guān)鍵字: 鋰離子電池； 正極材料； 磷酸鐵鋰； 碳凝膠
（ College of Metallurgy Science and Engineering,
Central South University, Changsha 410083, China）
Abstract: LiFePO4/C composite obtained with carbon gel as carbon droped were prepared by solid-state reaction. The crystalline structure, morphology of particles, carbon contents were analyzed by X-ray diffraction, scanning electromicroscopy and carbon/sulfur determinator. The resulting carbon contents in these samples are 0％, 5％, 10％, 22%, respectively . The results of X-ray diffraction show that the LiFePO4/C is pure olivine-type phase. SEM micrographs confirmed that the addition of the carbon reduces the LiFePO4 grain size.The carbon is dispersed between the grains, ensuring a good electronic contact. Electrochemical tests show that the material obtained by adding carbon gives enhanced performance in term of improved practical capacity and cycleability. The first specific discharge capacities of the LiFePO4/C coated with about 22% carbon is 143.4 mA·h/g, after 6 times cycling the discharge capacities is 142.7 mA·h/g. The capacity fade is about 0.7%.
Key words: Li-ion battery; cathode material; lithium iron phosphate; carbon gel
