碳纳米材料改性LiFePO_(4)及其电化学性能  

Nanocarbons modified LiFePO_(4) and its electrochemical performance

作　　者：狄方 杨浩淋 邢天宇[1,2,4] 赵小平 张砚秋 李莉香[1,2] 安百钢 DI Fang;YANG Haolin;XING Tianyu;ZHAO Xiaoping;ZHANG Yanqiu;LI Lixiang;AN Baigang(School of Chemical Engineering,University of Science and Technology Liaoning,Anshan 114051,Liaoning,China;Key Laboratory of Energy Materials and Electrochemistry Research Liaoning Province,University of Science and Technology Liaoning,Anshan 114051,Liaoning,China;Shandong Shuifa Industrial Group Co.Ltd.,Jinan 250103,Shandong,China;Wanhua Chemical Group Co.Ltd.,Yantai 264001,Shangdong,China)

机构地区：[1]辽宁科技大学化学工程学院,辽宁鞍山114051 [2]辽宁省能源材料与电化学重点实验室,辽宁鞍山114051 [3]山东水发实业集团有限公司,山东济南250103 [4]万华化学集团股份有限公司,山东烟台264001

出　　处：《储能科学与技术》2020年第S01期7-12,共6页Energy Storage Science and Technology

基　　金：国家自然科学基金项目(51672118,51672117,51972156,52872131);辽宁省特聘教授项目(2017);辽宁省重点研发计划重点项目(2018304017)

摘　　要：利用碳纳米管(CNTs)一维纤维结构和良好的导电能力,以聚吡咯包覆碳纳米管(PPy@CNTs)热转化形成的氮掺杂碳纳米管(NCNTs)为导电增强剂,将NCNTs与炭包覆LiFePO_(4)(C@LFP)复合以使商业LiFePO_(4)电极获得更优异的电化学性能。首先采用葡萄糖热解方法,制备C@LFP,再使NCNTs均匀分布在C@LFP间,制备炭包覆和氮掺杂碳纳米管改性磷酸亚铁锂NCNTs-C@LFP。分别利用X射线衍射仪(XRD)和场发射扫描电镜(SEM)对样品晶体结构组成分析和微观结构形貌进行观察。NCNTs均匀分布于LFP颗粒之间,并且制备工艺没有改变LiFePO_(4)晶体结构。通过物理吸附仪对样品的孔结构进行分析,NCNTs-C@LFP的比表面积和利于离子传输的中小孔体积也较纯LFP明显提高。采用电化学技术进行半电池测试,结果表明,炭包覆有效提高了LiFePO_(4)粒子导电能力,而一维NCNTs进一步提高了LiFePO_(4)粒子间的导电性。NCNTs-C@LFP电荷传递阻抗较LFP降低了5倍。在0.1 C倍率放电条件下,NCNTs-C@LFP比容量达165 mA·h/g,较商业LiFePO_(4)(125 mA·h/g)提高32%。1 C倍率100次充放电循环,NCNTs-C@LFP容量保持率为94%。利用碳包覆层和氮掺杂碳纳米管构筑三维导电网络的简单技术路线,可有效改善LiFePO_(4)电化学性能。By utilizing the advantages of good conductivity and one-dimensional fiber structure of carbon nanotubes(CNTs),nitrogen-doped carbon nanotubes(NCNTs)formed through the thermal conversion of polypyrrole-coated carbon nanotubes(PPy@CNTs)was utilized as an enhanced conducting additive.A composite of LiFePO_(4)coated with carbon layers(C@LFP)and NCNTs has been prepared to improve the electrochemical performance of commercial LiFePO_(4)(LFP).The C@LFP was prepared through the pyrolysis of sucrose.Then the NCNTs-C@LFP and the nitrogen-doped CNTs(NCNTs)were uniformly distributed between the C@LFP particles.X-ray diffractometer and field emission scanning electron microscope(SEM)were used to analyze the crystal structure and microstructure of the samples.NCNTs are uniformly distributed between LFP particles and the preparation process did not change the crystal structure of LiFePO_(4).The analysis of the pore structure of the sample by a physical adsorption instrument showed that the nanocarbon modification increases the specific surface area and the volume of small mesopores with the size of 2~5 nm of the NCNTsC@LFP,which can facilitate the ions migration.Electrochemical tests showed that the carbon coating could improve the electronic conductivity of LFP particles and the NCNTs enhance the conductivity between the LFP particles.The charge transfer impedance of NCNTs-C@LFP shows a decrease of five times as that of LFP.The capacity of NCNT@C@LFP reaches 165 mA·h/g at a 0.1 C rate,which increases by 32%compared with the LFP(125 mA·h/g).The capacity retention rate of NCNTs-C@LFP is 94%after 100 cycles at 1.0 C.The results indicate that the electrochemical performance of LFP can be improved efficiently through constructing the conducting networks by the carbon coating with twodimensional structure and NCNTs with one-dimensional structure.

关 键 词：锂离子电池 磷酸亚铁锂 碳包覆 氮掺杂碳纳米管 

分 类 号：TQ131.11[化学工程—无机化工] TM912[电气工程—电力电子与电力传动]