Insights into stability, electronic properties, defect properties and Li ions migration of Na, Mg and Al-doped LiVPO₄F for cathode materials of lithium ion batteries: A first-principles investigation

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• 作者：Xiaojun Lv^a ; Zhenming Xu^a ; Jie Li^a ; ^{15216105346@163.com" class="auth_mail" title="E-mail the corresponding author} ; Jiangan Chen^b ; Qingsheng Liu^c
• 关键词：First-principles ; LiVPO4F ; Doping ; Electrical conductivity ; Li ions migration
• 刊名：Journal of Solid State Chemistry
• 出版年：2016
• 出版时间：July 2016
• 年：2016
• 卷：239
• 期：Complete
• 页码：228-236
• 全文大小：2477 K

文摘

The effects of Na, Mg and Al doping on the structure, electronic property, defect property and Li ions migration of LiVPO₄F were investigated by the first-principles method. Calculations show that the processes of forming Li_0.875Na_0.125VPO₄F, α- and β-LiMg_0.375V_0.75PO₄F, α- and β-LiAl_0.125V_0.875PO₄F are all feasible. Na, Mg and Al doping significantly improve the electrical conductivity of LiVPO₄F and simultaneously maintain their structural stability attributing to the reduction of band gaps through variations of V-3d spin up orbitals. Li vacancy defects of LiVPO₄F are not ignorable, and vacancy defects with a lower activation energy for Li atom are far more likely to occur than Frenkel defects for Li and vacancy defects for other atoms. For pristine LiVPO₄F, path D along [0.012 rc">rce" class="mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0022459616301712&_mathId=si0008.gif&_user=111111111&_pii=S0022459616301712&_rdoc=1&_issn=00224596&md5=8fd867fe4b23b5d132895cfc6f8bea00">rce" style="margin-top: -5px; vertical-align: middle" title="View the MathML source" src="/sd/grey_pxl.gif" data-inlimgeid="1-s2.0-S0022459616301712-si0008.gif">ript>rder="0" style="vertical-align:bottom" width="22" alt="View the MathML source" title="View the MathML source" src="http://origin-ars.els-cdn.com/content/image/1-s2.0-S0022459616301712-si0008.gif">ript>r hidden">roll">r accent="true">row>0.17row>̅r> 0.572] direction is found to have the lowest activation energy of 0.418 eV, suggesting that anisotropic nature of Li ion conduction and LiVPO₄F is a one-dimensional (1D)-ion conductor. The corresponding diffusion coefficient was estimated to be 2.82×10⁻⁹ cm²/s, which is in good agreement with those experimental values.