LiFePO4論文：鋰離子電池正極材料LiFePO_4及其摻雜改性的第一性原理研究

1、LiFeP04 論文：鋰離子電池正極材料LiFeP0_4 及其摻雜改性的第一性原理研究【中文摘要】基于考慮了 Fe-3d 電子間的庫侖作用 U 和交換作用 J的 GGA+方案,應(yīng)用第一性原理計(jì)算系統(tǒng)研究了LiFeP04 的晶格動(dòng)力學(xué)性質(zhì)。我們計(jì)算并分析了玻恩有效電荷張量、布里淵區(qū)中心的聲子頻率和聲子色散曲線。玻恩有效電荷張量顯示各向異性，佐證了LiFeP04 中鋰離子沿一維通道方向遷移的機(jī)理。布里淵區(qū)中心點(diǎn)聲子 頻率的計(jì)算值和相應(yīng)的實(shí)驗(yàn)結(jié)果符合得比較好。應(yīng)用第一性原理計(jì)算系統(tǒng)研究了 LiFeP04 的對位缺陷，以及對位缺陷的形成對材料的電導(dǎo) 率和離子擴(kuò)散速率的影響。結(jié)果表明,Li/Fe 交換缺

2、陷是最容易形成 的,形成缺陷后的 Fe-0 鍵變長,擴(kuò)寬了鋰離子傳輸通道，有利于鋰離 子在通道中的擴(kuò)散，對材料電化學(xué)性能的改善起到了一定的作用。應(yīng) 用第一性原理計(jì)算系統(tǒng)研究了具有 Mg 摻雜 Li 和 Fe 位的 LiFeP04 材 料的原子和電子結(jié)構(gòu)。結(jié)果顯示,Mg 更容易摻雜到 LiFeP04 的 Fe 位, 進(jìn)而形成新的LiFe1-yMgyP04 固溶體，可以很好地提高 LiFeP04 的離 子電導(dǎo)率和電子電導(dǎo)率，并由此提出可能的微觀導(dǎo)電機(jī)理。同時(shí),我們 發(fā)現(xiàn)隨著 Mg 含量的增加，雜質(zhì)的形成能和 LiFe1-yMgyP04 的體積呈現(xiàn) 降低和減小的趨勢，這與實(shí)驗(yàn)結(jié)果符合得比較好?！居⑽?/p>

3、摘要】Lattice dyn amical properties of LiFePO4 are studiedusing first-principles density functional theorytaking into account the on-site Coulomb interactionwithin theGGA+U scheme. Born effective charge ten sors, phononfrequencies at the Brillouinzone center and phonon dispersioncurves are calculated a

4、nd an alyzed. The Born effective charge ten sorsexhibit ani sotropy, which gives an in direct evide nee for theone-dimensional Li migration tunnel along the 010 directi on in LiFePO4,which has bee n proposed by other theoretical calculations andexperimental observation. The calculated pho non freque

5、 ncies at therpoint of the Brillo uin zone agree well with the available experime ntalresults.A ntisite defect, electr onic con ductivity and ionic dyn amicproperties of LiFePO4 have bee n inv estigated using first-principlesdensity functional theory taking into accountthe on-site Coulomb in teracti

6、o n within the GGA+U scheme.Results in dicate the Li/Fe excha nge defect is the most preferred tooccur in LiFePO4, which causes the Fe-O bond length to cha nge in thedirecti on favors the formatio n of Li+ diffusi on cha nn els, hence improving the ionic dyn amic properties of the olivi ne LiFePO4.A

7、tomic andelectro nic structures of LiFePO4 with Mg doping at Li and Fe sites havebeen investigatedusingthe first-principles density functional theory with the on-site Coulombinteraction taken into account. It isdem on strated that Mgis prefere ntiallydoped at Fe site in steadof Li site to form a new

8、 LiFe1-yMgyPO4 solid solution,leadingto a higher ionic conductivity. Besides, it is found that formatio n en ergiesand the cell volumes decreased gradually with the in crease of Mgconcen trati on in LiFe1-yMgyPO4, which agrees well with the availableexperimental data.【關(guān)鍵詞】LiFePO4 對位缺陷 Mg 摻雜晶格動(dòng)力學(xué)第一性原理 計(jì)算【英文關(guān)鍵詞】LiFePO4 An tiste defectMg-dop ing Lattice dyn amicsFirst-pr in ciplescalculati ons【目錄】鋰離子電池正極材料 LiFePO_4 及其摻雜改性的第一性 原理研究【備注】索購全文在線加好友釣:1.39938848同時(shí)提供論文寫作一對一指導(dǎo)和論文發(fā)表委托服務(wù)摘要 4-5 Abstract 5 第一章緒論 8-291.1鋰離子電池發(fā)展的歷史及其工作原理9-121.2 鋰離子電池正極材料的類型和結(jié)構(gòu)12-161.2.1 鋰離子電池正極材料的類型 121.2.2 鋰離子電池正極材料的結(jié)構(gòu)12-1