Ti掺杂LiNiO_2第一性原理研究

On the first principles of Ti-doped LiNiO_2

采用基于密度泛函理论的第一性原理超软贋势平面波法,对Ti掺杂LiNiO_2的几何结构进行优化,计算其晶体结构、原子布局、态密度、能带结构及电子结构.结果表明:Ti掺杂LiNiO_2,降低系统能量,结构更加稳定,并且使得晶胞参数c及c/a比值增大,层间距增大,有利于Li+脱嵌和迁移,从而改善其电化学性能;同时,掺杂Ti影响周边O和Ni电子排布,使得周边O-Ni键增长,减弱O与Ni之间的相互作用,O-Ti与O-Ni键长相近,抑制因Jahn-Teller效应导致的八面体扭曲,增强结构稳定性,改善循环性能;Ti掺杂还使得禁带宽度、能隙及电子跃迁所需能量均减小,且此时Li在材料中以离子形态存在,有利于脱嵌和扩散,增强导电性.

Based on density functional theory,the first principles supersoft pseudopotential plane wave method is used to optimize the geometry structure of Ti doped LiNiO2,and calculate its crystal structure,atomic layout,density of states,energy band structure and electronic structure.The results show that Ti doped with LiNiO2 decreases the energy and structure of the system,and makes the ratio of C and c/a increased.The spacing between layers increases,which is favorable for Li+deintercalation and migration,thereby improving its electrochemical performance.Meanwhile,doping Ti affects the arrangement of electrons around O and Ni,making the peripheral O-Ni bond grow,weakening the interaction between O and Ni.O-Ti is close to the O-Ni bond,suppressing the distortion of the eight surface due to Jahn-Teller effect,enhancing the structural stability and improving the cycling performance.Ti doping also decreases the energy of band gap,energy gap and electron transition.At the same time,Li exists in the material in ionic form,which is conducive to the deembedding and diffusion,and enhance the conductivity.