(1. 中南大學(xué) 冶金科學(xué)與工程學(xué)院, 長沙 410083; 2. 廣西師范大學(xué) 化學(xué)化工學(xué)院，桂林 541004)
摘 要: 以可溶性鋰鹽、鐵鹽及有機(jī)碳源為原料，通過真空高溫固相合成法，同時得到兩種LiFePO4/C納米復(fù)合材料(分別來源于直接固相合成和氣相沉積)。采用XRD、SEM、TEM及電化學(xué)工作站對復(fù)合材料的結(jié)構(gòu)及電化學(xué)性能進(jìn)行分析和研究。結(jié)果表明：來源于氣相沉積的LiFePO4/C復(fù)合材料具有良好的結(jié)構(gòu)和電化學(xué)性能，LiFePO4顆粒大小為50~200 nm，碳膜的厚度為5~10 nm；在0.05C倍率下放電比容量為170 mA∙h/g，接近LiFePO4材料的理論比容量；以1C、2C、5C倍率放電，放電容量分別是理論容量的83%、77%、62%；1C倍率下進(jìn)行充放電循環(huán)50次后，容量衰減只有0.27%，表明材料具有良好的倍率放電性能和循環(huán)性能。
關(guān)鍵字: 鋰離子二次電池；磷酸鐵鋰；陰極；復(fù)合材料；納米材料
vacuum heat solid-phase method
（1.School of Metallurgical Science and Engineering, Central South University, Changsha 410083, China;
2. School of Chemistry and Chemical Engineering, Guangxi Normal University, Guilin 541004, China）
Abstract:Two kinds of LiFePO4/C nano-composites from direct solid-phase synthesis and vapor deposition respectively were obtained simultaneity through vacuum heat solid-phase method using soluble lithium salts, ferric salt and organic carbon as raw materials. XRD, SEM, TEM and electrochemical workstation were used to analyze the structures and electrochemical properties of composites. The result shows that the LiFePO4/C composite from vacuum vapor deposition has good structure and excellent electrochemical performance; the size of LiFePO4 particle is 50−200 nm and the carbon membrane thickness is 5−10 nm; the specific capacity is 170 mA∙h/g when discharged at 0.05C, which is close to theoretical capacity of LiFePO4 materials. When discharged at 1C, 2C and 5C, the specific capacities of nano-composite are 83%, 77% and 62% of the theoretical capacity, respectively, indicating that the sample has good discharge capability at large current rate. The LiFePO4/C nano-composite also shows excellent cycling stability with only 0.27% capacity fade after being charged-discharged for 50 cycles at 1C current rate.
Key words: lithium-ion secondary battery; LiFePO4; cathode; composite; nanomaterials
