水热法一步合成VO_2粉末及其微观形貌调控

One-step Hydrothermal Synthesis of VO_2 Powders with Micro-morphology Control

采用水热法,钒源选择V_2O_5,在使用还原剂草酸,不使用其他表面活性剂及模板的条件下,制备了具有不同微观形貌的VO_2(B)和VO_2(M)粉末,主要研究了草酸溶液浓度变化对产物微观形貌的影响。利用X射线衍射仪(XRD)对粉末的晶型结构和物相组成进行分析,通过扫描电子显微镜(SEM)对粉末的微观形貌进行表征。在180℃水热反应温度下,制备出了具有多种特殊微观形貌的VO_2(B)粉末,典型的如"雪花"状、"杨桃"状以及均匀短棒状等,全面系统地对粉末所出现的不同微观形貌进行了总结。采用蓝电电池测试系统对不同微观形貌VO_2(B)粉末制备的锂离子电池进行充放电测试,结果表明,"杨桃"状VO_2(B)锂离子电池性能较优,比容量峰值可达4 683.8mAh/g,但电池循环特性较差。同时,在水热反应温度260℃下,合成了微观形貌分别为短棒状、"雪花"状、"核桃"状以及球状的VO_2(M)粉末。DSC测试结果显示,VO_2(M)粉末形貌对其相变温度影响较小。

VO2(B)and VO2(M)powders with different micro-morphologies were successfully synthesized via hydrothermal method from V2O5 using oxalic acid as reducing agent.In the absence of surfactants and other templates in the synthesis mixture,the morphology of the product was only controlled by the concentration of the oxalic acid.The micro-morphology,crystal structure and composition of the powders were analyzed by scanning electron microscopy(SEM)and X-ray diffraction(XRD).At low hydrothermal temperature(180℃),VO2(B)powders with various micro-morphology,such as snowflake like,carambola like,and uniform rod like structures were obtained.The different micro-morphology of the powders appeared were summarized systematically.The prepared VO2 samples were tested in Li-ion batteries by LANDdt system.It was found that the batteries using VO2(B)powder with carambola like structure had the highest specific capacity peak value(4 683.8 mAh/g),but the cycling stability was poor.When the hydrothermal reaction temperature was increased tO260℃,rod like,snowflake like,walnut like and spherical like VO2(M)particles were synthesized.The DSC results showed that the micro-morphology had nOinfluence on the transition temperature of the mate-rials.