热处理温度对针状焦的结构及电化学性能的影响  

Effect of heat treatment temperature on structure and electrochemical properties of needle coke

作　　者：杨洲 鲍晨光 陈玉喜[1] 夏笑虹[1] 何月德[1] 刘洪波[1,2] Yang Zhou;Bao Chen-guang;Chen Yu-xi;Xia Xiao-hong;He Yue-de;Liu Hong-bo(College of Material Science and Engineering,Hunan University,Hunan Changsha 410082,China;Hunan Province Key Laboratory for Advanced Carbon Materials Applied Technology,Hunan University,Hunan Changsha 410082,China)

机构地区：[1]湖南大学材料科学与工程学院,湖南长沙410082 [2]湖南大学先进炭材料及应用技术湖南省重点实验室,湖南长沙410082

出　　处：《炭素技术》2022年第2期45-52,共8页Carbon Techniques

基　　金：国家自然科学基金项目(51772083,51402101);湖南省科技重大专项项目(2018GK1030)。

摘　　要：为探索不同热处理温度下针状焦的结构演变及电化学性能,对其进行600~3000℃的热处理并作为锂离子电池负极材料。通过X射线衍射、拉曼光谱、傅里叶变换红外光谱等考察了针状焦随热处理温度的结构演变,通过恒电流充放电、循环伏安法等探究了针状焦的电化学性能随热处理温度的变化规律,揭示了热处理温度对针状焦结构和电化学性能的影响。结果表明,随着热处理温度的升高,针状焦经历了从无定形碳到三维有序石墨的结构变化,主要嵌锂机制从“表面吸附储锂”、“碳层边缘嵌锂”向“石墨微晶层间嵌锂”转变。针状焦在37.2 mA/g电流密度下的放电比容量随热处理温度升高呈先减小后增大的规律变化,经3000℃热处理的针状焦比容量可达365 mAh/g。“褶皱”的碳六边形网格层难以储锂是造成热处理温度低于2200℃的针状焦放电比容量较低的主要原因之一。热处理温度高于2200℃的针状焦具有稳定的电位平台,电位平台的出现及其长度与石墨微晶尺寸明显增大具有较好的关联性。Needle coke was used as anode materials for lithium-ion batteries after heat-treating in a wide temperature range(from600℃to 3000℃)in order to explore the relationship between the structural evolution and electrochemical properties at different heat treatment temperatures.The structure evolution of needle coke with temperature was systematically investigated by using X-ray diffraction,Raman spectroscopy and Fourier transform infrared spectroscopy and so on.Meanwhile,the variation of electrochemical performance of needle coke was also tested by galvanostatic charge discharge and cyclic voltammetry.The results show that the main mechanism of lithium storage changes from"surface adsorption","edge intercalation"to"graphite microcrystalline intercalation"as the structure of needle coke evolves from amorphous carbon to three-dimensional ordered graphite with the increase of heat treatment temperature.The specific discharge capacity of needle coke at the current density of 37.2 m A/g decreases first(below 2200℃)and then increases with the heat treatment temperature and reaches as high as 365 m Ah/g at 3000℃.The capacity decrease of the needle coke heat-treated below 2200℃can be ascribed to the“wrinkled”hexagonal carbon lattice of needle coke being not favorable for lithium ions storage.As the temperature increases above 2200℃,needle coke exhibits a stable potential platform,and the appearance and length of potential platform have a good correlation with the increase of graphite microcrystalline size.

关 键 词：锂离子电池 针状焦 热处理温度 结构 电化学性能 

分 类 号：TQ522.65[化学工程—煤化学工程] TE626.87[石油与天然气工程—油气加工工程] TM911.15[电气工程—电力电子与电力传动]