从制备方法到形貌控制的角度着手,使用水热法制备性能稳定的LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)正极材料并对其电化学性能进行分析。采用草酸(H2C2O4)、碳酸氢铵(NH4HCO3)和尿素(CON2H4)作为沉淀剂和螯合剂,使用不同的Ni、Co、Mn过渡金属盐作为原材料,利用水热法制备出新颖的棒状形貌、球形形貌和椭球形形貌的LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)正极材料,并对正极材料进行电化学测试。结果表明,棒状形貌、球形形貌和椭球形形貌的正极材料都具有优异的循环性能,其中椭球状材料的电化学性能最好(当在充放电倍率为20 m A/g,电压范围在2.8~4.3 V时,首次放电比容量为175.04m Ah/g,最高放电比容量为188.78 m Ah/g,容量保持率为88.7%,在倍率为2000 m A/g时放电比容量达到115.47m Ah/g)。
In this study. we have employed a facile oxalate-assisted hydrothermal approach to tailor the morphology of β-NaYF_4:Er^(3+),Yb^(3+)(NYFEY) powders through the variation of the molar ratio of oxalate ions(Oxa^(2-)) and rare earth ions(RE^(3+)) in the range of 0.5:1.1:1.2:1, 5:1. and 10:1. The obtained results show that the crystallinity, particle size and upconversion luminescence intensity of the as-synthesized NYFEY particles are gradually decreased as the Oxa^(2-):RE^(3+) molar ratio increases from 0.5:1 to 10:1. For the purpose of photoelectrochemical performance evaluation,the as-synthesized NYFEY particles with different morphologies are incorporated into the nanocrystalline TiO2 films to form the multifunctional nano-and sub-micro meter composite photoanodes of dye-sensitized solar cells(DSSCs). A short-circuit current density(Jsc) of 14.26 mA/cm^2 and power conversion efficiency(PCE) of 7.31% are obtained for DSSCs prepared with hexagonal rod-like NYFEY crystals,evidencing an increase of 29.8% compared with DSSCs prepared with only TiO_2 nanoparticles. The demonstrated synthesis approach for tailoring the morphology and size of NYFEY particles and enhancing the performance of DSSCs can also be applied for other types of solar cells.
Juan WangZhenqiang DuMirabbos HojamberdievSiqi ZhengYunhua Xu
