Al掺杂对正极材料LiNi_(0.33-x)Mn_(0.33)Co_(0.33)Al_xO_2结构和电化学性能的影响

Influence of Al Doping Content on the Structure and Electrochemical Behaviour of LiNi_(0.33-x)Mn_(0.33)Co_(0.33)Al_xO_2

以柠檬酸为螯合剂利用快速湿化学法合成了具有α-NaFeO2型层状结构的LiNi0.33-xMn0.33Co0.33AlxO2(x=0.00,0.01,0.02,0.04)正极材料,并通过X-射线衍射、充放电测试、循环伏安和交流阻抗对材料的结构和电化学性能进行了系统研究。XRD结果表明此方法合成的材料具有很好的层状结构且阳离子的混排度随着Al3+含量的增加而下降。电化学测试表明,LiNi0.31Mn0.33Co0.33Al0.02O2具有很好的电化学性能和和循环性能,1C放电倍率下首次放电比容量达到176.9 mAh.g-1,且Al3+的掺杂能有效提高电荷在电极界面间转移并抑制了在高压循环过程中电荷转移阻抗的增加。

Layered materials of LiNi0.33-xMn0.33Co0.33AlxO2（x=0.00,0.01,0.02,0.04） with α-NaFeO2 structure were synthesized by a fast wet-chemical process with citric acid as the chelating agent.The crystal structure and electrochemical properties were systematically investigated by X-ray diffraction（XRD）,charge-discharge test,cyclic voltammetry（CV） and AC impedance.Structure analysis shows that all the resulted LiNi0.33-xMn0.33Co0.33AlxO2 materials possess a well-layered hexagonal structure and the cation-mixing of Li layer in materials degrades with increasing Al content.The analysis from electrochemical tests suggests that the electrochemical performance is improved by Al substitution in LiNi0.33Mn0.33Co0.33O2.LiNi0.31Mn0.33Co0.33Al0.02O2 shows higher initial discharge capacity and more structure-stable than other samples.AC impedance reveals that the enhancement of electrochemical performance is attributed to the decrease of the charge transfer resistance during high-voltage cycling because of Al substitution.