TG-MS analysis on thermal decomposable components in the SEI film on Cr2O3 powder anode in Li-ion batteries

The thermal decomposable species in the solid electrolyte interphase (SEI) film on Cr₂O₃ powder anode at different lithiated and delithiated states in the first cycle were analyzed by thermogravimetry and mass spectrometry (TG-MS) technique. The weight loss ratio in a fully lithiated Cr₂O₃ electrode during TG measurement at 50–500 °C is 8.9 wt%, which is decreased to 1.5 wt% for a fully delithiated Cr₂O₃ electrode. This indicates that the SEI film on Cr₂O₃ powder anode is decomposed electrochemically upon delithiation. The main gas products are CH₂=CH₂, CO₂, and CH₃-containing volatile species in thermal reaction. They are released step-by-step in four characteristic temperature regions, which were originated mainly from oligomer and polyethylene-oxide-like species, partly from ROCO₂Li. It is also observed that the amount of thermal decomposable components in the SEI film on the fully lithiated Cr₂O₃ powder electrode is much higher than that on graphite and hard carbon anodes, indicating different SEI features of transition metal oxide anodes.     

新型持久性有机污染物分析方法研究进展

多溴联苯醚、多溴联苯、全氟辛基羧酸/磺酸、十氯酮和溴代二(口恶)英等属于"斯德哥尔摩公约"2009年新增列和潜在的持久性有机污染物,近年来受到环境研究者的广泛关注.其在环境中的残留特征、污染来源、演变趋势、迁移传输、生物累积和毒理效应方面的研究依赖于分析技术的发展.多溴联苯醚和多溴联苯与传统持久性有机污染物具有类似的理化性质,采样和分析测定过程同有机氯农药和多氯联苯相近,可使用索氏提取、自动索氏提取、超声萃取、微波辅助萃取、压力溶剂萃取等多种提取方法,酸洗、多层复合层析柱和凝胶渗透色谱是最常用的净化手段,分析时采用GC/MS-EI或GC/MS-NCI对指示性单体进行定性定量.由于环境背景中的残留很低,使用高分辨质谱和串联质谱可降低方法检出限.对于水环境和沉积物中的全氟烷基羧酸、磺酸及其盐,目前主要采用固相萃取HPLC/MS/MS测定.亲水亲油平衡的萃取柱对全氟辛基羧酸和磺酸有良好的回收,弱阴离子交换萃取柱对短链和长链全氟烷基羧酸和磺酸都有满意的回收.十氯酮有一定极性,采用含有丙酮的萃取体系具有较高的回收率,GC/ECD和GC/MS分析时对色谱系统的清洁性有较高的要求,否则容易导致色谱峰拖尾影响定性和定量.溴代二(口恶)英与二(口恶)英的分析技术路线类似,需要更严格的净化过程分离多溴联苯醚,并在分析时控制热脱溴.此外,方法的应用还依靠溴代二(口恶)英标准物质的完善.     

Li and Na Co-decorated carbon nitride nanotubes as promising new hydrogen storage media

The capacity of Li and Na co-decorated carbon nitride nanotube (CNNT) for hydrogen storage is studied using first-principles density functional theory. The results show that with two H₂ molecules attached to per Li and four H₂ molecules per Na the Li and Na co-decorated CNNT gains a gravimetric density of H₂ as high as 9.09 wt% via electrostatic interaction without the clustering of the deposited metal atoms (at T=0 K). The average adsorption energy of hydrogen molecule is in the range of 0.09-0.22 eV/H₂, which is suitable for practical hydrogen storage at ambient temperatures.