Na_(2)MnPO_(4)F/Ti_(3)C_(2)-CQDs对Li/Na储能性能的密度泛函理论研究

Density generalized functional theory study of Na_(2)MnPO_(4)F/Ti_(3)C_(2)-CQDs for Li/Na energy storage performance

Na_(2)MnPO_(4)F作为锂/钠混合离子电池的电极材料,具有低成本、无毒、高电压和价态丰富等特点,但电子电导率低、离子扩散速率慢、锰的溶解及Jahn-Teller效应,限制了其应用。基于密度泛函理论下的第一性原理,以Na_(2)MnPO_(4)F/Ti_(3)C_(2)和Na_(2)MnPO_(4)F/Ti_(3)C_(2)-碳量子点(CQDs)复合材料为研究对象,构建Na2MnPO4F、NaLiMnPO_(4)F、Na_(2)MnPO_(4)F/Ti_(3)C_(2)、NaLiMnPO_(4)F/Ti_(3)C_(2)、Na_(2)MnPO4F/Ti_(3)C_(2)-CQDs和NaLiMnPO_(4)F/Ti_(3)C_(2)-CQDs等6种结构模型,计算能带结构、结合能、态密度及电荷局域密度,分析复合前后材料的电子结构和性能变化。Li原子的引入,使Na_(2)MnPO_(4)F与Ti_(3)C_(2)和Ti_(3)C_(2)-CQDs的结合能分别增大1.1397 J/m^(2)和0.7866 J/m^(2),复合Ti_(3)C_(2)和Ti_(3)C_(2)-CQDs能改善Na_(2)MnPO_(4)F的导电性,且Ti_(3)C_(2)-CQDs改善效果更佳。

As an electrode material for lithium/sodium hybrid ion battery,Na_(2)MnPO_(4)F had the features of low cost,nontoxicity,high voltage and abundant valence states,but its application was limited by the low electronic conductivity,slow ion diffusion rate,dissolution of manganese and Jahn-Teller effect.Based on the first principle under the density functional theory,Na_(2)MnPO_(4)F/Ti_(3)C_(2)and Na_(2)MnPO_(4)F/Ti_(3)C_(2)-carbon quantum dots(CQDs)composites were investigated to construct Na_(2)MnPO_(4)F,NaLiMnPO_(4)F,Na_(2)MnPO_(4)F/Ti_(3)C_(2),NaLiMnPO_(4)F/Ti_(3)C_(2),Na_(2)MnPO_(4)F/Ti_(3)C_(2)-CQDs and NaLiMnPO_(4)F/Ti_(3)C_(2)-CQDs six structural models.The energy band structures,binding energies,density of states and charge localization densities were calculated.The changes of electronic structure and properties of materials before and after composite were analyzed.The introduction of Li atoms could increase the binding energy of Na_(2)MnPO_(4)F with Ti_(3)C_(2)and Ti_(3)C_(2)-CQDs by 1.1397 J/m^(2)and 0.7866 J/m^(2),respectively,composite Ti_(3)C_(2)and Ti_(3)C_(2)-CQDs could improve the conductivity of Na_(2)MnPO_(4)F,the improvement effect of Ti_(3)C_(2)-CQDs was better.