摘要
通过多层核壳结构的γ-MnO2成功制备了一种由尖晶石单晶组合而成的空心球形尖晶石锰酸锂正极材料,所制备的样品采用X射线衍射、扫描电镜进行了表征,并进一步通过循环伏安、交流阻抗以及恒电流充放电对其电化学性能进行了研究。结果表明,所合成的空心球形锰酸锂颗粒大小均匀,平均直径在8μm左右,由结晶良好的尖晶石八面体单晶组成。电性能测试结果表明,空心球形尖晶石锰酸锂具有高比容量、高倍率以及优异的循环性能。在3.3～4.3V电压范围、0.2C下的首次放电比容量高达145.9mAh/g,50次循环后的容量保持率为95.9%,10C时的首次放电比容量仍为113.3mAh/g,100次循环后的容量保持率达95.5%。
This paper investigated the properties of ZnO ： H thin films. We found that hydrogen played an important role on structural and properties of ZnO = H thin films. With the changing of H2 flow ratio, the effects of H doping manifested as passivating vacancy defects, shallow donor doping and etching action. When the Hz flow ratio （R = H2/ （H2 ＋ Ar）40.02） was low, samples grown along the （002） preferential orientation. In this condition, H＋ did mainly play a role of shallow donor doping of passivating oxygen vacancies and substitu- ting zinc ion, so the unit cell volumes became smaller and the crystallinity of ZnO ： H thin films increased; in addition, H＋ passivated oxygen vacancies, which made the band tails became narrower, so the optical band gap became wider; we could observe the grains size became bigger and homogeneous distribution on the rough films surface from the SEM figure; besides, the resistivity of thin film decreased, which was mainly attributed to the electron mobility increased from the erystallinity increasing and the electron concentration increased from the shallow donor doping. When the flow ratio was more than 0.04 （R^0.04）, the （002） peak of XRD quenched, the unit cell volumes became bigger and the quality of crystallization decreased. In the FT-IR spectra, which was observed an absorption band at 3400-3900 cm-1. It exhibited to the typical O--H bonding local vibrational modes （LVM） absorption band. Owing to the charges unbalance was caused by polar molecular clusters （hydroxy） in the high doping concentration, which produced a mass of oxygen vacancies and increased the electron concentration, so it led to the decreasing of the film resistivity. In this condition, the optical band gap became narrower, which caused by the H＋ etching action.
出处
《功能材料》
EI
CAS
CSCD
北大核心
2013年第10期1493-1496,1501,共5页
Journal of Functional Materials
基金
国家自然科学基金资助项目(21071046)
